This study explores the integration of Synthetic Aperture Radar(SAR)imagery with deep learning and metaheuristic feature optimization techniques for enhanced oil spill detection.This study proposes a novel hybrid appr...This study explores the integration of Synthetic Aperture Radar(SAR)imagery with deep learning and metaheuristic feature optimization techniques for enhanced oil spill detection.This study proposes a novel hybrid approach for oil spill detection.The introduced approach integrates deep transfer learning with the metaheuristic Binary Harris Hawk optimization(BHHO)and Principal Component Analysis(PCA)for improved feature extraction and selection from input SAR imagery.Feature transfer learning of the MobileNet convolutional neural network was employed to extract deep features from the SAR images.The BHHO and PCA algorithms were implemented to identify subsets of optimal features from the entire feature dataset extracted by MobileNet.A supplemented hybrid feature set was constructed from the PCA and BHHO-generated features.It was used as input for oil spill detection using the logistic regression supervised machine learning classification algorithm.Several feature set combinations were implemented to test the classification performance of the logistic regression classifier in comparison to that of the proposed hybrid feature set.Results indicate that the highest oil spill detection accuracy of 99.2%has been achieved using the logistic regression classification algorithm,with integrated feature input from subsets identified using the PCA and the BHHO feature selection techniques.The proposed method yielded a statistically significant improvement in the classification performance of the used machine learning model.The significance of our study lies in its unique integration of deep learning with optimized feature selection,unlike other published studies,to enhance oil spill detection accuracy.展开更多
Loss of multiyear ice(MYI)is of great importance for Arctic climate and marine systems and can be monitored using active and passive microwave satellite data.In this paper,we describe an upgraded classification algori...Loss of multiyear ice(MYI)is of great importance for Arctic climate and marine systems and can be monitored using active and passive microwave satellite data.In this paper,we describe an upgraded classification algorithm using the data from the scatterometer and radiometer sensors onboard the Chinese Haiyang-2B(HY-2B)satellite to identify MYI and first-year ice(FYI).The proposed method was established based on K-means and fuzzy clustering(K-means+FC)and was used to focus on the transition zone where the ice condition is complex due to the highly commixing of MYI and FYI,leading to the high challenge for accurate classification of sea ice.The K-means algorithm was applied to preliminarily classify MYI using the combination of scatterometer and radiometer data,followed by applying fuzzy clustering to reclassify MYI in the transition zone.The HY-2B K-means+FC results were compared with the ice type products[including the Ocean and Sea Ice Satellite Application Facility(OSI SAF)sea ice type product and the Equal-Area Scalable Earth-Grid sea ice age dataset],and showed agreement in the time series of MYI extent.Intercomparisons in the transition zone indicated that the HY-2B K-means+FC results can identify more old ice than the OSI SAF product,but with an underestimation in identifying second-year ice.Comparisons between K-means and Kmeans+FC results were performed using regional ice charts and Sentinel-1 synthetic aperture radar(SAR)data.By adding fuzzy clustering,the MYI is more consistent with the ice charts,with the overall accuracy(OA)increasing by 0.9%–6.5%.Comparing against SAR images,it is suggested that more scattered MYI floes can be identified by fuzzy clustering,and the OA is increased by about 3%in middle freezing season and 7%–20%in early and late freezing season.展开更多
The North Water Polynya(NOW)is one of the largest and most productive polynyas in the Arctic.Compared to the surrounding sea ice,the combination of high winds and cold air,together with the thin ice or open water surf...The North Water Polynya(NOW)is one of the largest and most productive polynyas in the Arctic.Compared to the surrounding sea ice,the combination of high winds and cold air,together with the thin ice or open water surface of the NOW,produces large turbulent heat fluxes(THFs).The accurate estimation of these parameters requires high-resolution atmospheric data,which can be provided by the reanalysis products from different sources.In this study,we calculated the winter latent heat flux(LHF)and sensible heat flux(SHF)over the NOW and its surrounding sea ice area from 2005/2006 to 2015/2016 using high-resolution(15 km)Arctic System Reanalysis version 2(ASRv2)data and low-resolution(30 km)European Centre for Medium-Range Weather Forecasts ERA5 data.Results show that the LHF/SHF over the surrounding sea ice is about 82%/88%lower than over the NOW,as estimated using either dataset.Furthermore,within each area,the difference in the THFs estimated from the two datasets is small.The spatial distribution of the LHF/SHF estimated from both data sources is similar to that of sea ice concentration.The average LHF/SHF in the polynya obtained using ASRv2 data is only 5%/7%higher than that from the values obtained using ERA5 data.This is because the wind speed and air temperature from the ASRv2 data are higher than those of ERA5,and their effects on the THFs can cancel each other out.Furthermore,the estimated THFs do not necessarily improve with the refined resolution of ASRv2.展开更多
Seventeen topsoil samples （9 urban, 4 suburban, 3 rural and 1 background） were collected in/around Harbin, a typical city in northeast of China, to measure concentration levels of organocholrine pesticides （OCPs） ...Seventeen topsoil samples （9 urban, 4 suburban, 3 rural and 1 background） were collected in/around Harbin, a typical city in northeast of China, to measure concentration levels of organocholrine pesticides （OCPs） in topsoil of Northeastern China in 2006. Hexachlorohexanes （HCH）, dichlorodiphenyltrichloroethane （DDT）, and hexachlorobenzene （HCB） were detected in soil samples with mean concentrations （in pg/g dry weight （dw）） of 7120, 5425, and 1039, respectively. The mean concentrations for other OCPs were very low, 4.8 pg/g dw for chlordane and 3.3 pg/g dw for endosulfan. Source identification analysis reveals that all OCPs found in soil samples were due to historical use of these chemicals or from other source regions through long- and short-range atmospheric transport. DDT was mainly used in the rural sites, whereas the sources of HCB, chlordane and endosulfan were mainly in the urban area. HCH was found almost equally in both urban and rural area. Soil concentrations of all detected OCPs, except HCHs, in and around Harbin were much lower than those in the southeast of China, which is expected since the use of these OCPs in the former was much lower than that in the latter, however higher HCH concentrations in and around Harbin than those found in most places of the Southeast China is not expected. It is suggested that high HCH concentration in soil of Northeast China was most likely due to long-range atmospheric transport （LRAT） from Southeast China and the cold condensation process.展开更多
Depth variations of total mercury （Hg） and methylmercury （MeHg） concentrations were studied in cores from non-colonized sediments, sediments colonized by Halimione portulacoides, Sarcocornia fruticosa and Spartina...Depth variations of total mercury （Hg） and methylmercury （MeHg） concentrations were studied in cores from non-colonized sediments, sediments colonized by Halimione portulacoides, Sarcocornia fruticosa and Spartina maritima and belowground biomass, in a moderately contaminated salt marsh （Tagus Estuary, Portugal）. Concentrations in belowground biomass exceeded up to 3 （Hg） and 15 （MeHg） times the levels in sediments, and up to 198 （Hg） and 308 （MeHg） times those found in aboveground parts. Methylmercury in colonized sediments reached 3% of the total Hg, 50 times above the maximum values found in non-colonized sediments. The absence of correlations between total Hg concentrations in sediments and the corresponding MeHg levels suggested that methylation was only dependent on the environmental and microbiological factors. The analysis of belowground biomass at high-depth resolution （2 cm） provided evidence that Hg and MeHg were actively absorbed from sediments, with higher enrichment factors at layers where higher microbial activity was probably occurring. The results obtained in this study indicated that the biotransformation of Hg to the toxic MeHg could increase the toxicity of plant-colonized sediments.展开更多
Photoreduction characteristics of divalent inorganic mercury (Hg2+) in the presence of specific algae species are still not well known.Laboratory experiments were conducted in the present study to identify the effects...Photoreduction characteristics of divalent inorganic mercury (Hg2+) in the presence of specific algae species are still not well known.Laboratory experiments were conducted in the present study to identify the effects of different concentrations of living/dead algae species,including Aphanizomenon flosaquae (AF) and Microcystis aeruginosa (MA),on the photoreduction rate of Hg2+ under various light conditions.The experimental results showed that percentage reduction of Hg2+ was significantly influenced by radiation wavelengths,and dramatically decreased with the presence of algae.The highest percentage reduction of Hg2+ was induced by UV-A,followed by UV-B,visible light and dark for both living and dead AF,and the order was dark > UV-A > UV-B > visible light for both living and dead MA.There were two aspects,i.e.,energy and attenuation rate of light radiation and excrementitious generated from algae metabolisms,were involved in the processes of Hg2+ photoreduction with the presence of algae under different light conditions.The percentage reduction of Hg2+ decreased from 15% to 11% when living and dead AF concentrations increased by 10 times (from 106 to 105 cells/mL),and decreased from11% to ~9% in the case of living and dead MA increased.Algae can adsorb Hg2+ and decrease the concentration of free Hg2+,thus inhibiting Hg2+ photoreduction,especially under the conditions with high concentrations of algae.No significant differences were found in percentage reduction of Hg2+ between living and dead treatments of algae species.The results are of great importance for understanding the role of algae in Hg2+ photoreduction.展开更多
Time-series of weekly total carbon （TC） concentrations of fine aerosol particles （PM2.5） in Beijing and Toronto were compared to investigate their respective levels and temporal patterns over two years from August...Time-series of weekly total carbon （TC） concentrations of fine aerosol particles （PM2.5） in Beijing and Toronto were compared to investigate their respective levels and temporal patterns over two years from August 2001 through July 2003. In addition to this comparison, differences in the factors contributing to the observed concentrations and their temporal variations are discussed. Based upon past knowledge about the two megacities with highly contrasting air pollutant levels, it is not surprising that the average TC concentration in Belling （31.5 μg C m^-3） was greater than that in Toronto by a factor of 8.3. Despite their large concentration differences, in both cities TC comprised a similarly large component of PM2.5. TC concentrations exhibited very different seasonal patterns between the two cities. In Beijing, TC experienced higher levels and greater weekly fluctuations in winter whereas in Toronto this behavior was seen in summer. As a result, the greatest gap in TC concentrations between Beijing and Toronto （by a factor of 12.7） occurred in winter, while the smallest gap （a factor of 4.6） was in summer. In Beijing, seasonal variations in the emissions probably played a greater role than meteorology in influencing the TC seasonality, while in Toronto during the warm months more than 80% of the hourly winds were recorded from the south, along with many potential anthropogenic sources for the days with high TC concentrations. This comparison of the differences provides insight into the major factors affecting carbonaceous aerosol in each city.展开更多
Bioaccumulative and biomagnifying contaminants, such as persistent organic pollutants （POPs） and mercury （Hg）, have for decades been recognized as a health concern in arctic marine biota. In recent years, global c...Bioaccumulative and biomagnifying contaminants, such as persistent organic pollutants （POPs） and mercury （Hg）, have for decades been recognized as a health concern in arctic marine biota. In recent years, global climate change （GCC） and related loss of arctic sea ice have been observed to be driving substantial change in arctic ecosystems. This review summarizes findings documenting empirical links between GCC-induced ecological changes and alterations in POP and Hg exposures and pathways in arctic marine ecosystems. Most of the studies have reported changes in POP or Hg concentrations in tissue in relation to GCC-induced changes in species trophic interactions. These studies have typically focused on the role of changes in abun- dance, habitat range or accessibility of prey species, particularly in relation to sea ice changes. Yet, the ecological change that re- suited in contaminant trend changes has often been unclear or assumed. Other studies have successfully used chemical tracers, such as stable nitrogen and carbon isotope ratios and fatty acid signatures to link such ecological changes to contaminant level variations or trends. Lower sea ice linked-diet changes/variation were associated with higher contaminant levels in some popula- tions of polar bears, ringed seals, and thick-billed murres, but the influence of changing trophic interactions on POP levels and trends varied widely in both magnitude and direction. We suggest that future research in this new area of GCC-linked ecotox- icology should focus on routine analysis of ancillary ecological metrics with POP and Hg studies, simultaneous consideration of the multiple mechanisms by which GCC and contaminant interactions can occur, and targeted research on changing exposures and toxicological effects in species known to be sensitive to both GCC and contaminants [Current Zoology 61 （4）： 617-628, 2015].展开更多
As indispensable strategic materials for high-tech industries,rare earth elements and yttrium(REY)have become particularly important in recent years,raising the demand of developing new approaches for reclamation of R...As indispensable strategic materials for high-tech industries,rare earth elements and yttrium(REY)have become particularly important in recent years,raising the demand of developing new approaches for reclamation of REY from REY-rich materials such as coal combustion products(CCPs).In this study,five coal-fired power plants(CFPPs)in Guizhou of southwest China were selected for investigating REY concentrations of solid samples,atmospheric emissions,and recovery potentials.REY concentrations of feed fuels are higher in this study(147.2-468.6 mg/kg)than what have been reported previously for coals in China and the world.REY atmospheric emissions are extremely low(38.70-180.11 mg REY/t coal).REY are enriched in bottom ash and fly ash,with average of 658±296 mg/kg and maximum of 1257 mg/kg from the five CFPPs.Relative enrichment factors(REF)of REY in bottom ash and fly ash compared with the feed fuel are 0.86-1.02 and 0.91-1.04,respectively.REY concentrations in desulfurized gypsum are very low(6-17 mg/kg),and that is mostly inherited from limestone.Critical REY(Nd,Eu,Tb,Dy,Y,and Er)in bottom/fly ash account for 34%-39%of the total REY and the outlook coefficients(Cout1)are in the range of 0.89-1.11.This study indicates a promising prospect to reclaim REY from REYrich CCPs(bottom and fly ash)in CFPPs in Guizhou,especially in the central-north Guizhou,although such practices require further technology advancement.展开更多
Karst in interbedded carbonates and evaporites has been reported to have important and complex impacts on reservoir. It is significant for exploration and karst geology. Here, we report such a new case from Middle Tri...Karst in interbedded carbonates and evaporites has been reported to have important and complex impacts on reservoir. It is significant for exploration and karst geology. Here, we report such a new case from Middle Triassic Leikoupo Formation of Sichuan Basin, Southwest China. Stratigraphic incompleteness and the occurrence of unconformity provide evidence for the presence of eogenetic karst. Under the impact of this eogenetic karst, residual weathered and solution-collapse breccia, solution pores and silicification and dedolomitization have been observed. Classic stratigraphic zonation of karst is not readily distinguishable, which is ascribed to the stratigraphic collapse of carbonate rocks resulting from the dissolution of evaporites by lateral subsurface fluid flow. In terms of impact on reservoir quality, karst can generally improve the initial physical property of the porous layers in theory. However, subsurface fluid flow dissolved the evarporitic beds and facilitated the collapse of overlying strata. As a consequence, the lateral continuity of the reservoirs would be destroyed, and relatively high-quality reservoirs can only be developed with little collapse of overlying strata, reflecting reservoir heterogeneities. This may be a general feature of reservoir formation under the impact of karst in interbedded carbonates and evaporites.展开更多
Using the observed data from 184 stations over the Yunnan-Guizhou Plateau （YGP） from 1961 to 2005, the long-term trends in sunshine duration, cloud amount, dry visibility （Vd）, dry extinction, and water vapor over...Using the observed data from 184 stations over the Yunnan-Guizhou Plateau （YGP） from 1961 to 2005, the long-term trends in sunshine duration, cloud amount, dry visibility （Vd）, dry extinction, and water vapor over the YGP are analyzed. The results show that 85% of the stations recorded shortening annual sunshine duration, with the decrease rates between -12.2 and -173.7 h/10yr. Results of Mann-Kendall tests indicate that, among the stations with decreasing sunshine duration, 63.7% of them experienced an abrupt change that started in the 1970s and peaked in the 1980s. This decreasing trend has reversed in the early years of the 21st century. The cloud cover and water vapor content in the mid and lower levels over the YGP had no obvious changes during the study period. The annual averages of Vd declined from 34 km in the 1960s to 27 km at present. The annual mean dry extinction coefficient trended upward, from 0.176 to 0.190, on the YGP from 1980 to 2005. Analyses of cloud cover, water vapor, atmospheric visibility, and dry extinction coefficient revealed that emitted tropospheric aerosols （including air pollutants） resulting from increased energy consumption over the YGP could be a major Factor influencing the reductions of sunshine duration and atmospheric visibility.展开更多
To evaluate the effectiveness of emission control regulations designed for reducing air pollution, chemically resolved PM_(2.5) data have been collected across Canada through the National Air Pollution Surveillance ne...To evaluate the effectiveness of emission control regulations designed for reducing air pollution, chemically resolved PM_(2.5) data have been collected across Canada through the National Air Pollution Surveillance network in the past decade. 24-hr time integrated PM_(2.5) collected at seven urban and two rural sites during 2010-2016 were analyzed to characterize geographical and seasonal patterns and associated potential causes. Site-specific seven-year mean gravimetric PM_(2.5) mass concentrations ranged from 5.7 to 9.6 μg/m^(3). Seven-year mean concentrations of SO_(4)^(2-), NO_(3)^(-), NH_(4)^(+), organic carbon(OC), and elemental carbon(EC) were in the range of 0.68 to 1.6, 0.21 to 1.5, 0.27 to 0.71, 1.1 to 1.9, and 0.37 to 0.71 μg/m^(3), accounting for 10.8%-18.1%, 3.7%-16.7%, 4.7%-7.4%, 18.4%-21.0%, and 6.4%-10.6%, respectively, of gravimetric PM_(2.5) mass. PM_(2.5) and its five major chemical components showed higher concentrations in southeastern Canada and lower values in Atlantic Canada, with the seven-year mean ratios between the two regions being on the order of 1.7 for PM_(2.5) and 1.8-7.1 for its chemical components. When comparing the concentrations between urban and rural sites within the same region, those of SO_(4)^(2-) and NH_(4)^(+) were comparable, while those of NO_(3)^(-), OC, and EC were around 20%, 40%-50%, and 70%-80%, respectively, higher at urban than rural sites, indicating the regional scale impacts of SO_(4)^(2-) and NH_(4)^(+) and effects of local sources on OC and EC. Monthly variations generally showed summertime peaks for SO_(4)^(2-) and wintertime peaks for NO_(3)^(-), but those of NH_(4)^(+), OC, and EC exhibited different seasonality at different locations.展开更多
The effects of calcination and modification on the morphology （shapes and textures） and crystal structure of anhydrite powders were studied. The results show that, calcination at 100℃ causes anhydrite to disintegra...The effects of calcination and modification on the morphology （shapes and textures） and crystal structure of anhydrite powders were studied. The results show that, calcination at 100℃ causes anhydrite to disintegrate into smaller crystals, accompanied by a slight in- crease in d-spacing. Without calcination and modification, the solidification time and curing time of anhydrite are 15 and 77 h, respectively. After the treatment, however, the solidification time and curing time are shortened significantly to 9.5 and 14 rain, respectively. The com- pressive and flexural strengths of hydration products made from the treated anhydrite reach 10.2 and 2.0 MPa, respectively. The much shorter solidification and curing time make it possible to use anhydrite as a building and construction material.展开更多
Background:Forest based climate mitigation emerged as a key component of the Paris Agreement,and thus re-quires robust science to reduce uncertainties related to such strategies.The aim of this study was to assess and...Background:Forest based climate mitigation emerged as a key component of the Paris Agreement,and thus re-quires robust science to reduce uncertainties related to such strategies.The aim of this study was to assess and compare the cumulative effects on carbon dynamics of forest management and climate change on boreal and northern temperate forest sector in eastern Canada for the 2020–2100 period.Methods:We used the spatially explicit forest landscape model LANDIS-II and its extension Forest Carbon Suc-cession,in conjunction with the Carbon Budget Model for Harvested Wood Products framework.We simulated the dynamics of forest composition and carbon flows from forest ecosystems to wood products and their substitution effect on markets under increasing climate forcing,according to a tonne-year approach.Simulations were con-ducted for a series of forest management scenarios based on realistic practices principally by clearcut in the boreal territory and continuous-cover forestry in the northern temperate one.These scenarios included:i)a business-as-usual scenario(BaU),representing the current management strategy,ii)increased harvesting by 6.3%to 13.9%,iii)increased conservation(i.e.reduced harvesting by 11.1%to 49.8%),iiii)and a scenario representing the natural evolution of the forest landscape(i.e.without any management activity).Results:Our study revealed that increasing harvesting levels had contrasting effects on the mitigation potential in northern temperate(enhance net sequestration)and boreal forest sector(enhance net emissions)in comparison to the BaU from 2040 onwards,regardless of the future climate.Carbon storage in wood products and the substi-tution effect were not sufficient to offset carbon emissions from ecosystems.Moreover,climate change had a strong impact on the capacity of both landscapes to act as carbon sinks.Northern temperate landscapes became a net source of carbon over time due to their greater vulnerability to climate change than boreal landscapes.Conclusions:Our study highlights the need to consider the initial landscape characteristics in simulations to maximize the mitigation potential of alternative forest management strategies.The optimal management solution can be very different according to the characteristics of forest ecosystems.This opens the possibility of optimizing management for specific forest stands,with the objective of maximizing the mitigation potential of a given landscape.展开更多
The paper forms the second part of an introduction to possible impacts of climate change on daily streamflow and extremes in the Province of Ontario, Canada. Daily streamflow simulation models developed in the compani...The paper forms the second part of an introduction to possible impacts of climate change on daily streamflow and extremes in the Province of Ontario, Canada. Daily streamflow simulation models developed in the companion paper (Part I) were used to project changes in frequency of future daily streamflow events. To achieve this goal, future climate information (including rainfall) at a local scale is needed. A regression-based downscaling method was employed to downscale eight global climate model (GCM) simulations (scenarios A2 and B1) to selected weather stations for various meteorological variables (except rainfall). Future daily rainfall quantities were projected using daily rainfall simulation models with downscaled future climate information. Following these projections, future daily streamflow volumes can be projected by applying daily streamflow simulation models. The frequency of future daily high-streamflow events in the warm season (May–November) was projected to increase by about 45%-55% late this century from the current condition, on average of eight-GCM A2 projections and four selected river basins. The corresponding increases for future daily low-streamflow events and future daily mean streamflow volume could be about 25%-90% and 10%-20%, respectively. In addition, the return values of annual one-day maximum streamflow volume for various return periods were projected to increase by 20%-40%, 20%-50%, and 30%-80%, respectively for the periods 2001-50, 2026-75, and 2051-2100. Inter-GCM and interscenario uncertainties of future streamflow projections were quantitatively assessed. On average, the projected percentage increases in frequency of future daily high-streamflow events are about 1.4-2.2 times greater than inter-GCM and interscenario uncertainties.展开更多
The paper forms the first part of an introduction to possible impacts of climate change on daily streamflow and extremes in the Province of Ontario, Canada. In this study, both conceptual and statistical streamflow si...The paper forms the first part of an introduction to possible impacts of climate change on daily streamflow and extremes in the Province of Ontario, Canada. In this study, both conceptual and statistical streamflow simulation modeling theories were collectively applied to simulate daily streamflow volumes. Based on conceptual rainfall-runoff modeling principle, the predictors were selected to take into account several physical factors that affect streamflow, such as (1) current and previous quantities of rainfall over the watershed, (2) an index of pre-storm moisture conditions, (3) an index of pre-storm evapotranspiration capacities, and (4) a seasonal factor representing seasonal variation of streamflow volume. These rainfall-runoff conceptual factors were applied to an autocorrelation correction regression procedure to develop a daily streamflow simulation model for each of the four selected river basins. The streamflow simulation models were validated using a leave-one-year-out cross-validation scheme. The simulation models identified that the explanatory predictors are consistent with the physical processes typically associated with high-streamflow events. Daily streamflow simulation models show that there are significant correlations between daily streamflow observations and model validations, with model R2s of 0.68-0.71, 0.61-0.62, 0.71-0.74, and 0.95 for Grand, Humber, Upper Thames, and Rideau River Basins, respectively. The major reason for the model performance varying across the basins might be that rainfall-runoff response time and physical characteristics differ significantly among the selected river basins. The results suggest that streamflow simulation models can be used to assess possible impacts of climate change on daily streamflow and extremes at a local scale, which is major objective of a companion paper (Part II).展开更多
Capillary electrophoresis coupled to mass spectrometry（CE–MS） was used for the analysis of naphthenic acid fraction compounds（NAFCs） of oil sands process-affected water（OSPW）. A standard mixture of amine-deriva...Capillary electrophoresis coupled to mass spectrometry（CE–MS） was used for the analysis of naphthenic acid fraction compounds（NAFCs） of oil sands process-affected water（OSPW）. A standard mixture of amine-derivatized naphthenic acids is injected directly onto the CE column and analyzed by CE–MS in less than 15 min. Time of flight MS analysis（TOFMS）, optimized for high molecular weight ions, showed NAFCs between 250 and 800 m/z. With a quadrupole mass analyzer, only low-molecular weight NAFCs（between 100 and 450 m/z） are visible under our experimental conditions. Derivatization of NAFCs consisted of two-step amidation reactions mediated by 1-ethyl-3-（3-dimethylaminopropyl）carbodiimide（EDC）, or mediated by a mixture of EDC and N-hydroxysuccinimide, in dimethyl sulfoxide, dichloromethane or ethyl acetate. The optimum background electrolyte composition was determined to be 30%（V/V） methanol in water and 2%（V/V） formic acid. NAFCs extracted from OSPW in the Athabasca oil sands region were used to demonstrate the feasibility of CE–MS for the analysis of NAFCs in environmental samples, showing that the labeled naphthenic acids are in the mass range of 350 to 1500 m/z.展开更多
The dry deposition process refers to the flux loss of an atmospheric pollutant due to uptake of the pollutant by the earth’s surfaces.Dry deposition flux of a chemical species is typically calculated as the product o...The dry deposition process refers to the flux loss of an atmospheric pollutant due to uptake of the pollutant by the earth’s surfaces.Dry deposition flux of a chemical species is typically calculated as the product of its surface-layer concentration and its dry deposition velocity(V_(d)).Field measurement based V_(d) data are very scarce or do not exist for many chemical species considered in chemistry transport models.In the present study,gaseous and particulate dry deposition schemes were applied to generate a database of hourly V_(d) for 45 gaseous species and three particle size ranges for two years(2016–2017)at a 15 kmby 15 km horizontal resolution across North America.Hourly V_(d) of the 45 gaseous species ranged from<0.001 to 4.6 cm/sec across the whole domain,with chemical species-dependentmedian(mean)values being in the range of 0.018–1.37 cm/sec(0.05–1.43 cm/sec).The spatial distributions of the two-year average V_(d) showed values higher than 1–3 cm/sec for those soluble and reactive species over certain land types.Soluble species have the highest V_(d) over water surfaces,while insoluble but reactive species have the highest V_(d) over forests.Hourly V_(d) of PM_(2.5) across the whole domain ranged from 0.039 to 0.75 cm/sec with median(mean)value of 0.18(0.20)cm s^(−1),while the mean V_(d) for PM_(2.5)–10 is twice that of PM_(2.5).Uncertainties in the modeled V_(d) are typically on the order of a factor of 2.0 or larger,which needs to be considered when applying the dataset in other studies.展开更多
Retrieval of Thin-Ice Thickness(TIT)using thermodynamic modeling is sensitive to the parameterization of the independent variables(coded in the model)and the uncertainty of the measured input variables.This article ex...Retrieval of Thin-Ice Thickness(TIT)using thermodynamic modeling is sensitive to the parameterization of the independent variables(coded in the model)and the uncertainty of the measured input variables.This article examines the deviation of the classical model’s TIT output when using different parameterization schemes and the sensitivity of the output to the ice thickness.Moreover,it estimates the uncertainty of the output in response to the uncertainties of the input variables.The parameterized independent variables include atmospheric longwave emissivity,air density,specific heat of air,latent heat of ice,conductivity of ice,snow depth,and snow conductivity.Measured input parameters include air temperature,ice surface temperature,and wind speed.Among the independent variables,the results show that the highest deviation is caused by adjusting the parameterization of snow conductivity and depth,followed ice conductivity.The sensitivity of the output TIT to ice thickness is highest when using parameterization of ice conductivity,atmospheric emissivity,and snow conductivity and depth.The retrieved TIT obtained using each parameterization scheme is validated using in situ measurements and satellite-retrieved data.From in situ measurements,the uncertainties of the measured air temperature and surface temperature are found to be high.The resulting uncertainties of TIT are evaluated using perturbations of the input data selected based on the probability distribution of the measurement error.The results show that the overall uncertainty of TIT to air temperature,surface temperature,and wind speed uncertainty is around 0.09 m,0.049 m,and−0.005 m,respectively.展开更多
As a genre that expressed women＇s dark protests, fantasies and the fear, female Gothic was not theorized until the late 1960s, and before its theorization, this convention was adopted by many women writers in their w...As a genre that expressed women＇s dark protests, fantasies and the fear, female Gothic was not theorized until the late 1960s, and before its theorization, this convention was adopted by many women writers in their works. Charlotte Perkins Gilman＇s The yellow wallpaper is one of the many examples. As the epitome of female gothic, The yellow wallpaper utilized the female gothic conventions--the grotesque symbol of yellow wallpaper, the hysteric narrative format and the archetype image of madwoman, to express women＇s status of her time--their repression, rebellion and quest for the ＂true self＂.展开更多
基金The authors extend their appreciation to the Deputyship for Research&Innovation,Ministry of Education in Saudi Arabia for funding this research work through the project number RI-44-0456.
文摘This study explores the integration of Synthetic Aperture Radar(SAR)imagery with deep learning and metaheuristic feature optimization techniques for enhanced oil spill detection.This study proposes a novel hybrid approach for oil spill detection.The introduced approach integrates deep transfer learning with the metaheuristic Binary Harris Hawk optimization(BHHO)and Principal Component Analysis(PCA)for improved feature extraction and selection from input SAR imagery.Feature transfer learning of the MobileNet convolutional neural network was employed to extract deep features from the SAR images.The BHHO and PCA algorithms were implemented to identify subsets of optimal features from the entire feature dataset extracted by MobileNet.A supplemented hybrid feature set was constructed from the PCA and BHHO-generated features.It was used as input for oil spill detection using the logistic regression supervised machine learning classification algorithm.Several feature set combinations were implemented to test the classification performance of the logistic regression classifier in comparison to that of the proposed hybrid feature set.Results indicate that the highest oil spill detection accuracy of 99.2%has been achieved using the logistic regression classification algorithm,with integrated feature input from subsets identified using the PCA and the BHHO feature selection techniques.The proposed method yielded a statistically significant improvement in the classification performance of the used machine learning model.The significance of our study lies in its unique integration of deep learning with optimized feature selection,unlike other published studies,to enhance oil spill detection accuracy.
基金the National Key Research and Development Program of China under contract No.2021YFC2803301the Fundamental Research Funds for the Central Universities,China under contract Nos 2042024kf0037 and 2042022dx0001the Natural Science Foundation of Wuhan under cocntract No.2024040701010030.
文摘Loss of multiyear ice(MYI)is of great importance for Arctic climate and marine systems and can be monitored using active and passive microwave satellite data.In this paper,we describe an upgraded classification algorithm using the data from the scatterometer and radiometer sensors onboard the Chinese Haiyang-2B(HY-2B)satellite to identify MYI and first-year ice(FYI).The proposed method was established based on K-means and fuzzy clustering(K-means+FC)and was used to focus on the transition zone where the ice condition is complex due to the highly commixing of MYI and FYI,leading to the high challenge for accurate classification of sea ice.The K-means algorithm was applied to preliminarily classify MYI using the combination of scatterometer and radiometer data,followed by applying fuzzy clustering to reclassify MYI in the transition zone.The HY-2B K-means+FC results were compared with the ice type products[including the Ocean and Sea Ice Satellite Application Facility(OSI SAF)sea ice type product and the Equal-Area Scalable Earth-Grid sea ice age dataset],and showed agreement in the time series of MYI extent.Intercomparisons in the transition zone indicated that the HY-2B K-means+FC results can identify more old ice than the OSI SAF product,but with an underestimation in identifying second-year ice.Comparisons between K-means and Kmeans+FC results were performed using regional ice charts and Sentinel-1 synthetic aperture radar(SAR)data.By adding fuzzy clustering,the MYI is more consistent with the ice charts,with the overall accuracy(OA)increasing by 0.9%–6.5%.Comparing against SAR images,it is suggested that more scattered MYI floes can be identified by fuzzy clustering,and the OA is increased by about 3%in middle freezing season and 7%–20%in early and late freezing season.
基金supported by the National Key Research and Development Program of China(Grant no.2024YFB3908004).
文摘The North Water Polynya(NOW)is one of the largest and most productive polynyas in the Arctic.Compared to the surrounding sea ice,the combination of high winds and cold air,together with the thin ice or open water surface of the NOW,produces large turbulent heat fluxes(THFs).The accurate estimation of these parameters requires high-resolution atmospheric data,which can be provided by the reanalysis products from different sources.In this study,we calculated the winter latent heat flux(LHF)and sensible heat flux(SHF)over the NOW and its surrounding sea ice area from 2005/2006 to 2015/2016 using high-resolution(15 km)Arctic System Reanalysis version 2(ASRv2)data and low-resolution(30 km)European Centre for Medium-Range Weather Forecasts ERA5 data.Results show that the LHF/SHF over the surrounding sea ice is about 82%/88%lower than over the NOW,as estimated using either dataset.Furthermore,within each area,the difference in the THFs estimated from the two datasets is small.The spatial distribution of the LHF/SHF estimated from both data sources is similar to that of sea ice concentration.The average LHF/SHF in the polynya obtained using ASRv2 data is only 5%/7%higher than that from the values obtained using ERA5 data.This is because the wind speed and air temperature from the ASRv2 data are higher than those of ERA5,and their effects on the THFs can cancel each other out.Furthermore,the estimated THFs do not necessarily improve with the refined resolution of ASRv2.
基金supported by the Heilongjiang Province Postdoctoral Research Funding (No AUGA41001074)the State Key Lab of Urban Water Resource and Envi-ronment, Harbin Institute of Technology (No 2008DX01)
文摘Seventeen topsoil samples （9 urban, 4 suburban, 3 rural and 1 background） were collected in/around Harbin, a typical city in northeast of China, to measure concentration levels of organocholrine pesticides （OCPs） in topsoil of Northeastern China in 2006. Hexachlorohexanes （HCH）, dichlorodiphenyltrichloroethane （DDT）, and hexachlorobenzene （HCB） were detected in soil samples with mean concentrations （in pg/g dry weight （dw）） of 7120, 5425, and 1039, respectively. The mean concentrations for other OCPs were very low, 4.8 pg/g dw for chlordane and 3.3 pg/g dw for endosulfan. Source identification analysis reveals that all OCPs found in soil samples were due to historical use of these chemicals or from other source regions through long- and short-range atmospheric transport. DDT was mainly used in the rural sites, whereas the sources of HCB, chlordane and endosulfan were mainly in the urban area. HCH was found almost equally in both urban and rural area. Soil concentrations of all detected OCPs, except HCHs, in and around Harbin were much lower than those in the southeast of China, which is expected since the use of these OCPs in the former was much lower than that in the latter, however higher HCH concentrations in and around Harbin than those found in most places of the Southeast China is not expected. It is suggested that high HCH concentration in soil of Northeast China was most likely due to long-range atmospheric transport （LRAT） from Southeast China and the cold condensation process.
基金supports providing by IPIMAR, Environment Canada and Reserva Natural do Estuário do Tejo Joo Canrio wish to thanks Fundaco para a Ciência e Tecnologia for his PDF grant(SFRH/BPD/26324/2006)
文摘Depth variations of total mercury （Hg） and methylmercury （MeHg） concentrations were studied in cores from non-colonized sediments, sediments colonized by Halimione portulacoides, Sarcocornia fruticosa and Spartina maritima and belowground biomass, in a moderately contaminated salt marsh （Tagus Estuary, Portugal）. Concentrations in belowground biomass exceeded up to 3 （Hg） and 15 （MeHg） times the levels in sediments, and up to 198 （Hg） and 308 （MeHg） times those found in aboveground parts. Methylmercury in colonized sediments reached 3% of the total Hg, 50 times above the maximum values found in non-colonized sediments. The absence of correlations between total Hg concentrations in sediments and the corresponding MeHg levels suggested that methylation was only dependent on the environmental and microbiological factors. The analysis of belowground biomass at high-depth resolution （2 cm） provided evidence that Hg and MeHg were actively absorbed from sediments, with higher enrichment factors at layers where higher microbial activity was probably occurring. The results obtained in this study indicated that the biotransformation of Hg to the toxic MeHg could increase the toxicity of plant-colonized sediments.
基金supported by the Science and Technology Department of Guizhou Province(No.Qiankehe LH zi [2017]7334hao)the China Postdoctoral Science Foundation(No.2017M613005)+2 种基金Foundation of Guizhou Educational Committee(No.Qian jiao he KY[2016]135)the National Natural Science Foundation of China(No.41563012)the Doctoral Scientific Research Foundation of Guizhou Normal University for 2014
文摘Photoreduction characteristics of divalent inorganic mercury (Hg2+) in the presence of specific algae species are still not well known.Laboratory experiments were conducted in the present study to identify the effects of different concentrations of living/dead algae species,including Aphanizomenon flosaquae (AF) and Microcystis aeruginosa (MA),on the photoreduction rate of Hg2+ under various light conditions.The experimental results showed that percentage reduction of Hg2+ was significantly influenced by radiation wavelengths,and dramatically decreased with the presence of algae.The highest percentage reduction of Hg2+ was induced by UV-A,followed by UV-B,visible light and dark for both living and dead AF,and the order was dark > UV-A > UV-B > visible light for both living and dead MA.There were two aspects,i.e.,energy and attenuation rate of light radiation and excrementitious generated from algae metabolisms,were involved in the processes of Hg2+ photoreduction with the presence of algae under different light conditions.The percentage reduction of Hg2+ decreased from 15% to 11% when living and dead AF concentrations increased by 10 times (from 106 to 105 cells/mL),and decreased from11% to ~9% in the case of living and dead MA increased.Algae can adsorb Hg2+ and decrease the concentration of free Hg2+,thus inhibiting Hg2+ photoreduction,especially under the conditions with high concentrations of algae.No significant differences were found in percentage reduction of Hg2+ between living and dead treatments of algae species.The results are of great importance for understanding the role of algae in Hg2+ photoreduction.
基金funded by National Natural Science Foundation of China(NSFC)projects(Grant Nos.20322203 and 40675079)the National Science Fund for Distinguished Young Scholars of NSFC(Grant No.20625722)
文摘Time-series of weekly total carbon （TC） concentrations of fine aerosol particles （PM2.5） in Beijing and Toronto were compared to investigate their respective levels and temporal patterns over two years from August 2001 through July 2003. In addition to this comparison, differences in the factors contributing to the observed concentrations and their temporal variations are discussed. Based upon past knowledge about the two megacities with highly contrasting air pollutant levels, it is not surprising that the average TC concentration in Belling （31.5 μg C m^-3） was greater than that in Toronto by a factor of 8.3. Despite their large concentration differences, in both cities TC comprised a similarly large component of PM2.5. TC concentrations exhibited very different seasonal patterns between the two cities. In Beijing, TC experienced higher levels and greater weekly fluctuations in winter whereas in Toronto this behavior was seen in summer. As a result, the greatest gap in TC concentrations between Beijing and Toronto （by a factor of 12.7） occurred in winter, while the smallest gap （a factor of 4.6） was in summer. In Beijing, seasonal variations in the emissions probably played a greater role than meteorology in influencing the TC seasonality, while in Toronto during the warm months more than 80% of the hourly winds were recorded from the south, along with many potential anthropogenic sources for the days with high TC concentrations. This comparison of the differences provides insight into the major factors affecting carbonaceous aerosol in each city.
文摘Bioaccumulative and biomagnifying contaminants, such as persistent organic pollutants （POPs） and mercury （Hg）, have for decades been recognized as a health concern in arctic marine biota. In recent years, global climate change （GCC） and related loss of arctic sea ice have been observed to be driving substantial change in arctic ecosystems. This review summarizes findings documenting empirical links between GCC-induced ecological changes and alterations in POP and Hg exposures and pathways in arctic marine ecosystems. Most of the studies have reported changes in POP or Hg concentrations in tissue in relation to GCC-induced changes in species trophic interactions. These studies have typically focused on the role of changes in abun- dance, habitat range or accessibility of prey species, particularly in relation to sea ice changes. Yet, the ecological change that re- suited in contaminant trend changes has often been unclear or assumed. Other studies have successfully used chemical tracers, such as stable nitrogen and carbon isotope ratios and fatty acid signatures to link such ecological changes to contaminant level variations or trends. Lower sea ice linked-diet changes/variation were associated with higher contaminant levels in some popula- tions of polar bears, ringed seals, and thick-billed murres, but the influence of changing trophic interactions on POP levels and trends varied widely in both magnitude and direction. We suggest that future research in this new area of GCC-linked ecotox- icology should focus on routine analysis of ancillary ecological metrics with POP and Hg studies, simultaneous consideration of the multiple mechanisms by which GCC and contaminant interactions can occur, and targeted research on changing exposures and toxicological effects in species known to be sensitive to both GCC and contaminants [Current Zoology 61 （4）： 617-628, 2015].
基金Project supported by the K.C.Wong Education FoundationNational Natural Science Foundation of China(U1612442)+3 种基金Key Grant for Creative Research Groups of Guizhou Provincial Education Department(Qian-Jiao-He KY Zi2016047)Young Scientific Talents Growth Project of Guizhou Provincial Education Department(Qian-Jiao-He KY Zi 2016252)Doctoralof Zunyi Normal University(Zun-Shi BS 201815)Science and Technology Project of Guizhou Provincial Science and Technology Department(Qian-Ke-He-Ping-Tai-RenCai 20175727-07)。
文摘As indispensable strategic materials for high-tech industries,rare earth elements and yttrium(REY)have become particularly important in recent years,raising the demand of developing new approaches for reclamation of REY from REY-rich materials such as coal combustion products(CCPs).In this study,five coal-fired power plants(CFPPs)in Guizhou of southwest China were selected for investigating REY concentrations of solid samples,atmospheric emissions,and recovery potentials.REY concentrations of feed fuels are higher in this study(147.2-468.6 mg/kg)than what have been reported previously for coals in China and the world.REY atmospheric emissions are extremely low(38.70-180.11 mg REY/t coal).REY are enriched in bottom ash and fly ash,with average of 658±296 mg/kg and maximum of 1257 mg/kg from the five CFPPs.Relative enrichment factors(REF)of REY in bottom ash and fly ash compared with the feed fuel are 0.86-1.02 and 0.91-1.04,respectively.REY concentrations in desulfurized gypsum are very low(6-17 mg/kg),and that is mostly inherited from limestone.Critical REY(Nd,Eu,Tb,Dy,Y,and Er)in bottom/fly ash account for 34%-39%of the total REY and the outlook coefficients(Cout1)are in the range of 0.89-1.11.This study indicates a promising prospect to reclaim REY from REYrich CCPs(bottom and fly ash)in CFPPs in Guizhou,especially in the central-north Guizhou,although such practices require further technology advancement.
基金funded by the “13th Five-Year Plan” National Science and Technology Major Project of China(No.2016ZX05004002)
文摘Karst in interbedded carbonates and evaporites has been reported to have important and complex impacts on reservoir. It is significant for exploration and karst geology. Here, we report such a new case from Middle Triassic Leikoupo Formation of Sichuan Basin, Southwest China. Stratigraphic incompleteness and the occurrence of unconformity provide evidence for the presence of eogenetic karst. Under the impact of this eogenetic karst, residual weathered and solution-collapse breccia, solution pores and silicification and dedolomitization have been observed. Classic stratigraphic zonation of karst is not readily distinguishable, which is ascribed to the stratigraphic collapse of carbonate rocks resulting from the dissolution of evaporites by lateral subsurface fluid flow. In terms of impact on reservoir quality, karst can generally improve the initial physical property of the porous layers in theory. However, subsurface fluid flow dissolved the evarporitic beds and facilitated the collapse of overlying strata. As a consequence, the lateral continuity of the reservoirs would be destroyed, and relatively high-quality reservoirs can only be developed with little collapse of overlying strata, reflecting reservoir heterogeneities. This may be a general feature of reservoir formation under the impact of karst in interbedded carbonates and evaporites.
基金funded by the National Natural Science Foundation of China (NSFC) (Grant No. 40965009)the Guizhou Provincial Meteorological Bureau Key Laboratory Programme (No. KF200906)
文摘Using the observed data from 184 stations over the Yunnan-Guizhou Plateau （YGP） from 1961 to 2005, the long-term trends in sunshine duration, cloud amount, dry visibility （Vd）, dry extinction, and water vapor over the YGP are analyzed. The results show that 85% of the stations recorded shortening annual sunshine duration, with the decrease rates between -12.2 and -173.7 h/10yr. Results of Mann-Kendall tests indicate that, among the stations with decreasing sunshine duration, 63.7% of them experienced an abrupt change that started in the 1970s and peaked in the 1980s. This decreasing trend has reversed in the early years of the 21st century. The cloud cover and water vapor content in the mid and lower levels over the YGP had no obvious changes during the study period. The annual averages of Vd declined from 34 km in the 1960s to 27 km at present. The annual mean dry extinction coefficient trended upward, from 0.176 to 0.190, on the YGP from 1980 to 2005. Analyses of cloud cover, water vapor, atmospheric visibility, and dry extinction coefficient revealed that emitted tropospheric aerosols （including air pollutants） resulting from increased energy consumption over the YGP could be a major Factor influencing the reductions of sunshine duration and atmospheric visibility.
基金supported by the China Scholarship Council for one year as a visiting fellow at Environment and Climate Change Canada。
文摘To evaluate the effectiveness of emission control regulations designed for reducing air pollution, chemically resolved PM_(2.5) data have been collected across Canada through the National Air Pollution Surveillance network in the past decade. 24-hr time integrated PM_(2.5) collected at seven urban and two rural sites during 2010-2016 were analyzed to characterize geographical and seasonal patterns and associated potential causes. Site-specific seven-year mean gravimetric PM_(2.5) mass concentrations ranged from 5.7 to 9.6 μg/m^(3). Seven-year mean concentrations of SO_(4)^(2-), NO_(3)^(-), NH_(4)^(+), organic carbon(OC), and elemental carbon(EC) were in the range of 0.68 to 1.6, 0.21 to 1.5, 0.27 to 0.71, 1.1 to 1.9, and 0.37 to 0.71 μg/m^(3), accounting for 10.8%-18.1%, 3.7%-16.7%, 4.7%-7.4%, 18.4%-21.0%, and 6.4%-10.6%, respectively, of gravimetric PM_(2.5) mass. PM_(2.5) and its five major chemical components showed higher concentrations in southeastern Canada and lower values in Atlantic Canada, with the seven-year mean ratios between the two regions being on the order of 1.7 for PM_(2.5) and 1.8-7.1 for its chemical components. When comparing the concentrations between urban and rural sites within the same region, those of SO_(4)^(2-) and NH_(4)^(+) were comparable, while those of NO_(3)^(-), OC, and EC were around 20%, 40%-50%, and 70%-80%, respectively, higher at urban than rural sites, indicating the regional scale impacts of SO_(4)^(2-) and NH_(4)^(+) and effects of local sources on OC and EC. Monthly variations generally showed summertime peaks for SO_(4)^(2-) and wintertime peaks for NO_(3)^(-), but those of NH_(4)^(+), OC, and EC exhibited different seasonality at different locations.
文摘The effects of calcination and modification on the morphology （shapes and textures） and crystal structure of anhydrite powders were studied. The results show that, calcination at 100℃ causes anhydrite to disintegrate into smaller crystals, accompanied by a slight in- crease in d-spacing. Without calcination and modification, the solidification time and curing time of anhydrite are 15 and 77 h, respectively. After the treatment, however, the solidification time and curing time are shortened significantly to 9.5 and 14 rain, respectively. The com- pressive and flexural strengths of hydration products made from the treated anhydrite reach 10.2 and 2.0 MPa, respectively. The much shorter solidification and curing time make it possible to use anhydrite as a building and construction material.
基金This study was funded by the Quebec Ministry of Forests,Wildlife,and Parks(contrats de service de recherche forestier 142332156-2018-A and 142332174-E:PI:E.Thiffault)by the Natural Science and Engineering Research Council through a Discovery Grant to E.Thiffault(grant number RGPIN-2018-05755).
文摘Background:Forest based climate mitigation emerged as a key component of the Paris Agreement,and thus re-quires robust science to reduce uncertainties related to such strategies.The aim of this study was to assess and compare the cumulative effects on carbon dynamics of forest management and climate change on boreal and northern temperate forest sector in eastern Canada for the 2020–2100 period.Methods:We used the spatially explicit forest landscape model LANDIS-II and its extension Forest Carbon Suc-cession,in conjunction with the Carbon Budget Model for Harvested Wood Products framework.We simulated the dynamics of forest composition and carbon flows from forest ecosystems to wood products and their substitution effect on markets under increasing climate forcing,according to a tonne-year approach.Simulations were con-ducted for a series of forest management scenarios based on realistic practices principally by clearcut in the boreal territory and continuous-cover forestry in the northern temperate one.These scenarios included:i)a business-as-usual scenario(BaU),representing the current management strategy,ii)increased harvesting by 6.3%to 13.9%,iii)increased conservation(i.e.reduced harvesting by 11.1%to 49.8%),iiii)and a scenario representing the natural evolution of the forest landscape(i.e.without any management activity).Results:Our study revealed that increasing harvesting levels had contrasting effects on the mitigation potential in northern temperate(enhance net sequestration)and boreal forest sector(enhance net emissions)in comparison to the BaU from 2040 onwards,regardless of the future climate.Carbon storage in wood products and the substi-tution effect were not sufficient to offset carbon emissions from ecosystems.Moreover,climate change had a strong impact on the capacity of both landscapes to act as carbon sinks.Northern temperate landscapes became a net source of carbon over time due to their greater vulnerability to climate change than boreal landscapes.Conclusions:Our study highlights the need to consider the initial landscape characteristics in simulations to maximize the mitigation potential of alternative forest management strategies.The optimal management solution can be very different according to the characteristics of forest ecosystems.This opens the possibility of optimizing management for specific forest stands,with the objective of maximizing the mitigation potential of a given landscape.
文摘The paper forms the second part of an introduction to possible impacts of climate change on daily streamflow and extremes in the Province of Ontario, Canada. Daily streamflow simulation models developed in the companion paper (Part I) were used to project changes in frequency of future daily streamflow events. To achieve this goal, future climate information (including rainfall) at a local scale is needed. A regression-based downscaling method was employed to downscale eight global climate model (GCM) simulations (scenarios A2 and B1) to selected weather stations for various meteorological variables (except rainfall). Future daily rainfall quantities were projected using daily rainfall simulation models with downscaled future climate information. Following these projections, future daily streamflow volumes can be projected by applying daily streamflow simulation models. The frequency of future daily high-streamflow events in the warm season (May–November) was projected to increase by about 45%-55% late this century from the current condition, on average of eight-GCM A2 projections and four selected river basins. The corresponding increases for future daily low-streamflow events and future daily mean streamflow volume could be about 25%-90% and 10%-20%, respectively. In addition, the return values of annual one-day maximum streamflow volume for various return periods were projected to increase by 20%-40%, 20%-50%, and 30%-80%, respectively for the periods 2001-50, 2026-75, and 2051-2100. Inter-GCM and interscenario uncertainties of future streamflow projections were quantitatively assessed. On average, the projected percentage increases in frequency of future daily high-streamflow events are about 1.4-2.2 times greater than inter-GCM and interscenario uncertainties.
文摘The paper forms the first part of an introduction to possible impacts of climate change on daily streamflow and extremes in the Province of Ontario, Canada. In this study, both conceptual and statistical streamflow simulation modeling theories were collectively applied to simulate daily streamflow volumes. Based on conceptual rainfall-runoff modeling principle, the predictors were selected to take into account several physical factors that affect streamflow, such as (1) current and previous quantities of rainfall over the watershed, (2) an index of pre-storm moisture conditions, (3) an index of pre-storm evapotranspiration capacities, and (4) a seasonal factor representing seasonal variation of streamflow volume. These rainfall-runoff conceptual factors were applied to an autocorrelation correction regression procedure to develop a daily streamflow simulation model for each of the four selected river basins. The streamflow simulation models were validated using a leave-one-year-out cross-validation scheme. The simulation models identified that the explanatory predictors are consistent with the physical processes typically associated with high-streamflow events. Daily streamflow simulation models show that there are significant correlations between daily streamflow observations and model validations, with model R2s of 0.68-0.71, 0.61-0.62, 0.71-0.74, and 0.95 for Grand, Humber, Upper Thames, and Rideau River Basins, respectively. The major reason for the model performance varying across the basins might be that rainfall-runoff response time and physical characteristics differ significantly among the selected river basins. The results suggest that streamflow simulation models can be used to assess possible impacts of climate change on daily streamflow and extremes at a local scale, which is major objective of a companion paper (Part II).
基金supported by the Environment Canada and the NSERC
文摘Capillary electrophoresis coupled to mass spectrometry（CE–MS） was used for the analysis of naphthenic acid fraction compounds（NAFCs） of oil sands process-affected water（OSPW）. A standard mixture of amine-derivatized naphthenic acids is injected directly onto the CE column and analyzed by CE–MS in less than 15 min. Time of flight MS analysis（TOFMS）, optimized for high molecular weight ions, showed NAFCs between 250 and 800 m/z. With a quadrupole mass analyzer, only low-molecular weight NAFCs（between 100 and 450 m/z） are visible under our experimental conditions. Derivatization of NAFCs consisted of two-step amidation reactions mediated by 1-ethyl-3-（3-dimethylaminopropyl）carbodiimide（EDC）, or mediated by a mixture of EDC and N-hydroxysuccinimide, in dimethyl sulfoxide, dichloromethane or ethyl acetate. The optimum background electrolyte composition was determined to be 30%（V/V） methanol in water and 2%（V/V） formic acid. NAFCs extracted from OSPW in the Athabasca oil sands region were used to demonstrate the feasibility of CE–MS for the analysis of NAFCs in environmental samples, showing that the labeled naphthenic acids are in the mass range of 350 to 1500 m/z.
文摘The dry deposition process refers to the flux loss of an atmospheric pollutant due to uptake of the pollutant by the earth’s surfaces.Dry deposition flux of a chemical species is typically calculated as the product of its surface-layer concentration and its dry deposition velocity(V_(d)).Field measurement based V_(d) data are very scarce or do not exist for many chemical species considered in chemistry transport models.In the present study,gaseous and particulate dry deposition schemes were applied to generate a database of hourly V_(d) for 45 gaseous species and three particle size ranges for two years(2016–2017)at a 15 kmby 15 km horizontal resolution across North America.Hourly V_(d) of the 45 gaseous species ranged from<0.001 to 4.6 cm/sec across the whole domain,with chemical species-dependentmedian(mean)values being in the range of 0.018–1.37 cm/sec(0.05–1.43 cm/sec).The spatial distributions of the two-year average V_(d) showed values higher than 1–3 cm/sec for those soluble and reactive species over certain land types.Soluble species have the highest V_(d) over water surfaces,while insoluble but reactive species have the highest V_(d) over forests.Hourly V_(d) of PM_(2.5) across the whole domain ranged from 0.039 to 0.75 cm/sec with median(mean)value of 0.18(0.20)cm s^(−1),while the mean V_(d) for PM_(2.5)–10 is twice that of PM_(2.5).Uncertainties in the modeled V_(d) are typically on the order of a factor of 2.0 or larger,which needs to be considered when applying the dataset in other studies.
文摘Retrieval of Thin-Ice Thickness(TIT)using thermodynamic modeling is sensitive to the parameterization of the independent variables(coded in the model)and the uncertainty of the measured input variables.This article examines the deviation of the classical model’s TIT output when using different parameterization schemes and the sensitivity of the output to the ice thickness.Moreover,it estimates the uncertainty of the output in response to the uncertainties of the input variables.The parameterized independent variables include atmospheric longwave emissivity,air density,specific heat of air,latent heat of ice,conductivity of ice,snow depth,and snow conductivity.Measured input parameters include air temperature,ice surface temperature,and wind speed.Among the independent variables,the results show that the highest deviation is caused by adjusting the parameterization of snow conductivity and depth,followed ice conductivity.The sensitivity of the output TIT to ice thickness is highest when using parameterization of ice conductivity,atmospheric emissivity,and snow conductivity and depth.The retrieved TIT obtained using each parameterization scheme is validated using in situ measurements and satellite-retrieved data.From in situ measurements,the uncertainties of the measured air temperature and surface temperature are found to be high.The resulting uncertainties of TIT are evaluated using perturbations of the input data selected based on the probability distribution of the measurement error.The results show that the overall uncertainty of TIT to air temperature,surface temperature,and wind speed uncertainty is around 0.09 m,0.049 m,and−0.005 m,respectively.
文摘As a genre that expressed women＇s dark protests, fantasies and the fear, female Gothic was not theorized until the late 1960s, and before its theorization, this convention was adopted by many women writers in their works. Charlotte Perkins Gilman＇s The yellow wallpaper is one of the many examples. As the epitome of female gothic, The yellow wallpaper utilized the female gothic conventions--the grotesque symbol of yellow wallpaper, the hysteric narrative format and the archetype image of madwoman, to express women＇s status of her time--their repression, rebellion and quest for the ＂true self＂.
