This study examines how Algeria’s winter(December-February,DJF)rainfall is affected by the trends and variability of the Mediterranean Sea Surface Temperature(SST)between 1993 and 2023.Empirical Orthogonal Function(E...This study examines how Algeria’s winter(December-February,DJF)rainfall is affected by the trends and variability of the Mediterranean Sea Surface Temperature(SST)between 1993 and 2023.Empirical Orthogonal Function(EOF)analysis and composite diagnostics were used to identify dominant SST modes and their atmospheric linkages using high-resolution datasets(ERSST,CHIRPS,and NCEP/NCAR reanalysis).The second Mediterranean SST mode(EOF2),which is the main cause of rainfall variability in Algeria,accounts for 25.3%of the variance in SST and is distinguished by a zonal dipole(eastern cooling vs.western warming).The associated atmospheric patterns show that whereas cool phases reduce precipitation through anticyclonic conditions and subsidence,warm SST phases increase rainfall through cyclonic circulation,increased vertical motion,and moisture flux convergence.The study concludes that the interannual and annual variation of Mediterranean SST is one of the key regulators of the winter hydroclimate in Algeria,and it has important implications,for the variability of water resources in the region.The importance of interannual SST variability over long-term trends in regulating Algeria’s winter hydroclimate is also highlighted by these findings,which are worth studying in the future.展开更多
Heavy metal contamination from Artisanal and Small-Scale Gold Mining(ASGM)is increasingly recognized as a global issue,impacting soil quality and public health.In Tanzania,while ASGM activities significantly bolster l...Heavy metal contamination from Artisanal and Small-Scale Gold Mining(ASGM)is increasingly recognized as a global issue,impacting soil quality and public health.In Tanzania,while ASGM activities significantly bolster local economies,they also pose serious environmental risks.This study examined the levels and dispersion of heavy metals,specifically mercury(Hg),lead(Pb),arsenic(As),zinc(Zn),and cadmium(Cd)in the Chunya district.Soil samples were collected from both active and abandoned tailing heaps and analysed by Atomic Absorption Spectroscopy(AAS),with the results compared to the WHO/FAO(2008)guidelines for agricultural soils.The findings revealed alarming concentrations of Hg across all sampling points,ranging from 0.88 to 3.72 mg·kg^(−1).In contrast,48 out of 51 sampling points exhibited higher Cd levels between 0.98 and 4.42 mg/kg,exceeding the safe limits of 0.5 mg·kg^(−1)for Hg and 0.8 mg·kg^(−1)for Cd.In contrast,the negative control site showed much lower levels(0.03mg·kg^(−1)for Cd and 0.43 mg·kg^(−1)for Hg).A notable decrease in heavy metal concentrations was observed with increasing distance from the tailing heaps(0 m to 200 m).Soil pH and electrical conductivity significantly influenced the mobility of these contaminants,with higher concentrations found near lower tailing heaps.The elevated levels of Hg and Cd present substantial risks to human health and ecosystems,highlighting the urgent need for effective remediation strategies.Furthermore,the gold mining industry must innovate technologies that minimize heavy metal release during extraction processes to mitigate environmental harm.展开更多
The genesis mechanism of low-resistivity oil formation in the medium-deep Shahejie Formation of Bohai C Oilfield is unclear,and there is a lack of effective methods for identifying low-resistivity oil layers.This arti...The genesis mechanism of low-resistivity oil formation in the medium-deep Shahejie Formation of Bohai C Oilfield is unclear,and there is a lack of effective methods for identifying low-resistivity oil layers.This article conducts a comprehensive analysis based on core sample experiments,and research shows that the formation of low-resistivity oil layers in the oilfield is mainly caused by the superposition of three factors:1)microcapillary development,high irreducible water;2)additional conductive effect of clay;3)deep invasion of high salinity mud filtrate.The low-resistivity oil layer in this oilfield is mainly characterized by high mud content and strong additional conductivity of clay,and the complex pore throat structure leads to high irreducible water saturation,and the impact of saline mud intrusion,resulted in low-resistivity oil layers.The oil-field is mainly a lightweight oil layer with hydrophilic wettability,studying the response characteristics of oil and water layers through core nuclear magnetic resonance experiments,effectively identifying low-resistivity oil layers based on the correlation between resistivity and physical properties.展开更多
This study investigates the Benxi Formation sandstone reservoirs in the Yanchuan East Block of the Ordos Basin,employing an integrated approach that includes core observation,thin-section analysis,scanning electron mi...This study investigates the Benxi Formation sandstone reservoirs in the Yanchuan East Block of the Ordos Basin,employing an integrated approach that includes core observation,thin-section analysis,scanning electron microscopy,high-pressure mercury intrusion,and petrophysical testing to systematically evaluate reservoir petrographic features and pore structures.Results reveal that Benxi Formation sandstones predominantly comprise quartz sandstones,lithic quartz sandstones,and lithic sandstones,characterized by high quartz content,widespread volcanic lithic fragments,moderately well-sorted grains,and complex cement types.Pore types are dominated by residual intergranular and dissolution pores,with minor intracrystalline pores and fractures;overall porosity ranges from 0.17%to 9.07%(average 4.74%),and permeability from 0.01 to 6.05 mD,classifying them as ultra-low porosity and tight reservoirs.High-pressure mercury intrusion indicates microfine throats as the primary structure,divisible into four distinct types.Diagenetically,compaction and cementation are the main drivers of primary pore loss and reservoir tightening,whereas late-stage dissolution partially ameliorates pore networks.Overall,Benxi Formation sandstone reservoirs exhibit pervasive densification but localized favorable pore assemblages and connectivity,facilitating hydrocarbon migration and accumulation.These findings advance understanding of Upper Paleozoic tight sandstone reservoir characteristics and aid in predicting sweet spots.展开更多
Harmful algal blooms(HABs)pose a growing threat to aquatic ecosystems,human health,and economies worldwide.Climate change and nutrient enrichment have driven an increase in both the size and frequency of blooms,making...Harmful algal blooms(HABs)pose a growing threat to aquatic ecosystems,human health,and economies worldwide.Climate change and nutrient enrichment have driven an increase in both the size and frequency of blooms,making accurate observation more urgent than ever.Remote sensing has become a critical tool for monitoring HABs,yet commonly used multispectral instruments such as MODIS,Landsat,and Sentinel face major limitations.Their coarse spatial resolution prevents reliable observation in smaller inland waters,long revisit times restrict timely monitoring,and limited spectral bands reduce the ability to discriminate key pigments like chlorophyll a and phycocyanin.In contrast,hyperspectral sensors capture hundreds of narrow,contiguous bands at higher spatial,temporal,and radiometric resolutions,enabling the detection of subtle phytoplankton characteristics and bloom dynamics across diverse environments.Hyperspectral imagers mounted on unmanned aerial systems further provide near-daily data collection,making them especially effective for tracking bloom evolution.While forecasting remains an emerging application,hyperspectral observation offers the clearest path forward for improving HAB detection and monitoring.This paper reviews the advantages of hyperspectral remote sensing over multispectral approaches and argues for its adoption as an essential technology in safeguarding aquatic health and mitigating the rising global risk of HABs.展开更多
Drought is one of the primary meteorological disasters affecting Dali Prefecture.This study employs the Integrated Meteorological Drought Index(IMDI)to systematically analyze the spatiotemporal evolution characteristi...Drought is one of the primary meteorological disasters affecting Dali Prefecture.This study employs the Integrated Meteorological Drought Index(IMDI)to systematically analyze the spatiotemporal evolution characteristics of mete-orological drought in Dali Prefecture from 2002 to 2023.Using linear trend analysis,spatial interpolation,and meteorological statistical methods,the key findings are as follows:interannual drought frequency fluctuated between 5.3%and 34.2%,with a mean of 24.3%;the 2019 extreme drought event showed significant correlation with concurrent Indian Ocean sea surface temperature anomalies;spatially,drought frequency exhibited a north-high-southlow pattern,ranging from 23.1%in the south to 29.8%in the north,with northern counties(e.g.,Jianchuan,Heqing)recording the maximum frequency(29.8%)resulting from the föhn effect on the leeward slope of the Nushan Mountains and high agricultural water consumption;annual drought duration increased significantly at 1.9 days/decade;seasonally,droughts intensified in spring(+0.62 days/decade)and winter(+1.5 days/decade)but weakened in summer(−0.8 days/decade)and autumn(−0.4 days/decade),a pattern poten-tially linked to East Asian monsoon weakening causing reduced winter-spring moisture transport;for drought severity,light drought dominated(annual mean:42.5 days,58%of total drought days)followed by progressively shorter durations of moderate,severe,and extreme drought,while combined severe/extreme drought duration increased at 0.7 days/decade,consistent with regional warming and increased evapotranspiration.This study elucidates the spatio-temporal drought patterns and climatic drivers in Dali Prefecture,providing a scientific basis for drought resilience planning and optimized water resource allocation in this plateau marginal region.展开更多
The publication of trifluoroacetic acid(TFA)concentrations in the Atlantic Ocean in 2022-2023 prompted an inventory update to include the period 2000 to 2020 for fluorspar(CaF2)production,use,TFA emissions,and their c...The publication of trifluoroacetic acid(TFA)concentrations in the Atlantic Ocean in 2022-2023 prompted an inventory update to include the period 2000 to 2020 for fluorspar(CaF2)production,use,TFA emissions,and their contri-bution to TFA in the Atlantic Ocean.The update accounts for 90%of the acid spar used to produce hydrogen fluoride in the period 2000 to 2020.Emissions of TFA due to fluorocarbons(HFCs,HFOs,HCFOs,HCFCs,and anaesthetics)are estimated at 503,700 tonnes in this period.Generation of TFA from the use of pesticides is estimated at 239,000 to 796,000 tonnes globally,assuming a 30%to 100%yield of TFA.In total,estimated emissions of TFA,from 1930 to 2020,are 1,019,000 tonnes,with a theoretical upper limit of 2,283,000 tonnes,which includes the quantity of TFA manufactured,where production is assumed to equal emissions.The estimated emissions of TFA to the Atlantic Ocean from 1930 to 2020 are 467,000 tonnes,with a theoretical upper limit of 1,215,000 tonnes.This is not consistent with the measured TFA concentrations,which suggest the Atlantic Ocean contains at least 40 million tonnes of TFA,possibly over 80 million tonnes,and must therefore include a large natural burden.展开更多
Expansive soils present a significant geohazard to light infrastructure world-wide,causing costly damage through swelling and shrinkage cycles driven by moisture content changes.One key property controlling this behav...Expansive soils present a significant geohazard to light infrastructure world-wide,causing costly damage through swelling and shrinkage cycles driven by moisture content changes.One key property controlling this behavior,the Cation Exchange Capacity(CEC),is complex and expensive to measure directly,making it necessary to find reliable and affordable proxies for initial site assessments.This study introduces and validates a novel parameter,the weighted plasticity index(wPI),for classifying the swelling potential of expansive clays.Twenty-six soil samples,representing a range from low to high plasticity clays from Trinidad,underwent standard geotechnical laboratory tests,including Atterberg limits and grain size analysis.The wPI was calculated for each sample as the product of its Plasticity Index(PI)and the percentage of fine particles(percent passing the 425-μm sieve).A strong linear relationship(R^(2)=0.94)was found between the wPI and the Liquid Limit(LL).Using a previously established relationship between LL and CEC,a robust mathematical model connecting wPI directly to CEC was derived.This model formed the basis for a new four-tiered swelling potential classification system(Low,Medium,High,and Very High)based on the calculated wPI values.The wPI method provides a reliable,quick,and cost-effective tool for geotechnical engineers to evaluate swelling potential,promoting the design of more resilient and sustainable infrastructure in areas prone to expansive soils.展开更多
In Oilfield B of the Bohai Bay Basin,the shallow-water delta sandbody reservoirs are thin and exhibit rapid lateral changes.Local incised superposition results in complex oil-water relationships within the sandbodies ...In Oilfield B of the Bohai Bay Basin,the shallow-water delta sandbody reservoirs are thin and exhibit rapid lateral changes.Local incised superposition results in complex oil-water relationships within the sandbodies and uneven plane injection-production response,which restricts the efficient tapping of remaining oil.Based on data such as drilling cores,geochemical analysis,well logging,and seismic data,the sedimentary characteristics of the lobate shallowwater delta are determined.Through seismic forward modeling,the seismic waveform characteristics of different sand body stacking patterns are summarized to guide the fine description of composite sand body stacking patterns and single-stage sand body plane distribution patterns.The results show that:by using identification markers such as the discontinuous,superimposed,and elevation difference characteristics of event axes on inverted seismic profiles,as well as the variation zones of planar seismic attributes,2 phases of composite channels can be divided.Five types of sandbody contact patterns were summarized,including discrete contact,lateral cutting contact,natural levee connection,vertical aggradation superimposition,and composite superimposition.Combined with the results of fine characterization of sand bodies,based on the single-phase channel and river-bar lobes,the remaining oil distribution law is summarized,the oil-water relationship and remaining oil distribution of the river-bar composite sand body are jointly controlled by the cutting interface of the sand body and the rhythm pattern of the composite sand body,and the potential tapping strategies such as improving the single-phase channel well pattern,river-bar lobes well pattern reconstruction and local encryption are proposed.The successful implementation of 24 adjustment wells and the successful production of 100 m3/d from 9 new adjustment wells demonstrates that the fine characterization method and resulting residual oil predictions are reasonable and credible,and provide reference for the development,production and potential mining of similar oilfields.展开更多
Under the context of global climate change,the frequent occurrence of strong winds in Guyuan has significantly hindered the development of local facility agriculture.Using hourly meteorological data from the Sanying N...Under the context of global climate change,the frequent occurrence of strong winds in Guyuan has significantly hindered the development of local facility agriculture.Using hourly meteorological data from the Sanying National Station and the Guyuan Greenhouse Station between April 2024 and April 2025,this study employed machine learning methods to develop wind speed prediction models based on BP neural network,support vector machine,and random forest(referred to as BP,SVM,and RF models),aiming to provide references for local disaster prevention and mitigation.The results indicate that:1)Wind speed at the Guyuan Greenhouse Station exhibits the strongest correlation with that at the National Station(0.489-0.595),followed by temperature and 24-hour precipitation(0.116-0.336).2)The mean absolute error(MAE)of the BP,RF,and SVM models at all heights is below 1.5 m/s,the root mean square error(RMSE)is under 2.1 m/s,and the forecast accuracy(FA)exceeds 75%,indicating satisfactory model performance.Compared to 3 m,the MAE and RMSE of 0.5 m are larger,while the FA is smaller.This indicates that the wind speed of 0.5 m is close to the ground,and is more affected by surface roughness and turbulence effects,resulting in greater randomness and making the model more difficult.3)Based on case analyses of May 10 and May 1,2024,the overall simulation performance ranks as“RF model>SVM model>BP model”;however,the SVM model demonstrates higher accuracy in simulating strong wind events.展开更多
Antimicrobial pollution in surface waters has become an urgent environmental issue globally,yet few studies have specifically focused on the prevalence and impacts of antimicrobial contaminants in Tanzanian surface wa...Antimicrobial pollution in surface waters has become an urgent environmental issue globally,yet few studies have specifically focused on the prevalence and impacts of antimicrobial contaminants in Tanzanian surface waters.This review article presents a comprehensive assessment of antimicrobial pollutants in Tanzania’s aquatic ecosystems,filling a critical gap in the current literature.The findings reveal widespread contamination of surface waters,primarily with antibiotics,from diverse sources,including domestic sewage,agricultural runoff,industrial effluents,and healthcare facilities.This work integrates findings from a range of disciplines,including environmental monitoring,public health,and agricultural practices,to provide a holistic understanding in the Tanzanian context.The presence of antimicrobial pollutants may lead to the promotion of antimicrobial resistance,disruption of microbial communities,and risks to human health through food chain.Therefore,there is a call for further studies to assess the extent of antimicrobial pollution in Tanzania and its broader implications for both environmental and public health.展开更多
The sandstone reservoir of the Shanxi Formation serves as a key exploration and development target in the eastern Yanchuan gas field of the Ordos Basin,where its physical properties and pore structure directly govern ...The sandstone reservoir of the Shanxi Formation serves as a key exploration and development target in the eastern Yanchuan gas field of the Ordos Basin,where its physical properties and pore structure directly govern the enrichment and distribution of hydrocarbons.This study systematically examines the petrological features,pore types,throat structures,and petrophysical parameters of the Shanxi Formation sandstone reservoir using core observation,thin-section identification,cast thin-section and scanning electron microscopy analyses,mercury injection porosimetry,and conventional petrophysical testing.Results indicate that the reservoir predominantly comprises fine-to mediumgrained sandstones,dominated by lithic sandstones,lithic quartz sandstones,and quartz sandstones as the primary lithofacies assemblages.Detrital components are chiefly quartz and metamorphic rock fragments,with cementation primarily of the pore-filling type and common siliceous and carbonate cements.Dominant pore types include dissolution pores in volcanic lithics,residual intergranular pores,and minor intercrystalline pores and microfractures.Porosity is generally low,averaging less than 6%,with permeability ranging from 0.001 to 5.577 mD.Mercury injection experiments reveal that throat sizes are predominantly small,exhibiting poor sorting and limited connectivity,classifying the reservoir overall as an ultra-low-porosity,tight type,though locally high-quality sandstone intervals are developed.Integrated analysis highlights pronounced heterogeneity in the Shanxi Formation reservoir,wherein pore preservation and dissolution processes exert significant enhancement on reservoir quality,while microfractures play a pivotal role in hydrocarbon migration and accumulation.These findings offer valuable insights for reservoir evaluation and natural gas exploration and development in the Shanxi Formation of the eastern Yanchuan gas field.展开更多
This study analyzes the spatiotemporal patterns and driving factors of forest fires in Liangshan Prefecture based on fire data from 2016 to 2024 using statistical methods.The results indicate:1)From 2016 to 2024,fores...This study analyzes the spatiotemporal patterns and driving factors of forest fires in Liangshan Prefecture based on fire data from 2016 to 2024 using statistical methods.The results indicate:1)From 2016 to 2024,forest fires in Liangshan Prefecture occurred predominantly between January and May(140 incidents),accounting for 97.90%of the total.March recorded the highest number of fires(48 incidents),representing 33.57%.Within a 24-hour period,113 fires occurred between 12:00 PM and 9:00 PM,constituting 79.02%of all incidents.2)Spatially,Mianning County recorded the highest number of forest fires(28 incidents,19.58%),followed by Xichang,Muli,and Yanyuan with 22,23,and 20 incidents,respectively.Human activities,particularly agricultural burning,outdoor smoking,and other causes,were the dominant factors,collectively accounting for 41%of incidents.3)Forest fires predominantly occurred at elevations between 1500 and 3000 meters(132 fires,92.31%),on slopes with gradients of 5-25 degrees(81 fires,56.65%),on west-facing aspects(northwest,west,southwest)(72 fires,53.14%),in areas with NDVI values between 0.51 and 0.8(79 incidents,55.24%),within 500-2000 m residential buffer zones(151 incidents,98.60%),and within 500 m road buffer zones(103 incidents,72.03%).4)Among meteorological factors,the 20-day average temperature(0.3041),80-day maximum temperature(0.3487),20-day minimum temperature(0.2594),20-day minimum relative humidity(−0.3132),70-day maximum wind speed(0.1885),and 70-day peak wind speed(0.1965)showed the strongest correlations with forest fire burned area.Burned area also exhibited a positive correlation with the Meteorological Drought Index(MCI)on the day of the fire(0.1990).This study confirms the lagged and persistent effects of meteorological factors on forest fire occurrence,providing key scientific evidence for constructing regional fire prediction models that integrate multi-scale meteorological indicators.展开更多
The Quasi-Biennial Oscillation(QBO)is a vital mode of stratospheric variability with significant influence on tropical and subtropical climate systems.However,its influence on precipitation variability across Eastern ...The Quasi-Biennial Oscillation(QBO)is a vital mode of stratospheric variability with significant influence on tropical and subtropical climate systems.However,its influence on precipitation variability across Eastern and Southern Africa remains insufficiently understood.This study examines the impact of the QBO on summer precipitation and associated circulation anomalies over Eastern and Southern Africa from 1979 to 2021.Using ERA5 and NOAA reanalysis datasets,we applied composite and correlation analyses to assess precipitation responses to westerly(WQBO)and easterly(EQBO)phases.Results show a dipole-like pattern,with WQBO linked to enhanced precipitation in both Eastern and Southern Africa,while EQBO is associated with reduced precipitation.Circulation analysis reveals that WQBO phases promote upper-level divergence,low-level moisture inflow,and vertical ascent,whereas EQBO phases enhance subsidence and upperlevel convergence.These findings highlight the QBO role in modulating precipitation through stratosphere-troposphere coupling and its interaction with regional circulation patterns.The quasi-periodic nature of QBO offers substantial potential for enhancing seasonal precipitation predictions when integrated with other regional circulations,such as the Botswana High and the Angola Low.展开更多
A geostatistical study was conducted with the objective of developing a better understanding of the sediments deposited in the tailings dam of an iron mine located in Brazil.The samples,derived from two drilling campa...A geostatistical study was conducted with the objective of developing a better understanding of the sediments deposited in the tailings dam of an iron mine located in Brazil.The samples,derived from two drilling campaigns conducted in 2001 and 2010,were statistically evaluated and validated for the construction of both a 3D geological model and an estimated model.The geological body modeling process was performed using an implicit method,which was based on the interpretation and adjustments of vertical sections and considered the positions of the samples and the grades of the chemical components of interest.In addition,the primitive topography was also considered to determine the base and limits of the deposit,as well as the current topography.The ordinary kriging(OK)method was chosen to estimate the grades of the chemical components and the retained/passing percentages of the particle size fractions described in the samples.The kriging model was validated through two analyses:mean comparison and drift analyses.The total tonnage of the estimated model was 287.14 Mt,with an average Fe grade of 63.89%.展开更多
The Quasi-Biennial Oscillation(QBO)is a dominant mode of interannual variability in the tropical stratosphere,known to influence global weather and climate patterns through stratosphere-troposphere coupling.While its ...The Quasi-Biennial Oscillation(QBO)is a dominant mode of interannual variability in the tropical stratosphere,known to influence global weather and climate patterns through stratosphere-troposphere coupling.While its impacts on the Northern Hemisphere are well-documented,its role in the Southern Hemisphere subtropical climate remains less explored.This study investigates the relationship between the QBO and September surface air temperature(SAT)over Southern Africa during the early austral spring from 1979 to 2021.We find that the QBO’s easterly phase(EQBO)at 50 hPa is associated with a significant dipole pattern in SAT,characterized by warming over southeastern Africa and cooling along the southwestern coastal area.Analysis reveals that this temperature pattern is driven by a coherent teleconnection pathway:the EQBO forces a quasi-barotropic geopotential height anomaly,which modulates vertical velocity,leading to enhanced convection and increased cloud cover over the cooling region and suppressed convection over the warming area.Outgoing Longwave Radiation data confirm this dipole in convective activity.A latitudinal-vertical cross-section demonstrates the descent of QBOrelated wind anomalies into the subtropical troposphere,outlining the direct stratospheric pathway for this distant influence.Our results identify the QBO as a key stratospheric precursor for early spring temperature variability in Southern Africa,with important implications for improving regional seasonal forecasting.展开更多
Tropical forests have large carbon stocks and their conservation is a very important mitigation measure against global warming.However,this carbon pool is the most vulnerable to anthropogenic activities like selective...Tropical forests have large carbon stocks and their conservation is a very important mitigation measure against global warming.However,this carbon pool is the most vulnerable to anthropogenic activities like selective logging and little is known about its recovery.This study aimed to determine the carbon stock recovery after selectively logging using different allometric equations in six 1 ha permanent monitoring plots established in logged and unlogged forest types.Each 1 ha was divided into 25,20×20 m and the DBH of all trees≥2 cm was measured in 2005/2006 and re-measured in 2011/2012.The logged forests had the highest%change in the species richness indicating the impacts of logging.The presence of exploitable commercial trees in both forest types suggests their recruitment after logging.The insignificant difference in the AGB using different allometric equations is an indication that the Pan tropical equation is a good reference for the calculations of AGB in moist tropical forests.The 59.4%recovery rate in forests of 21 YAL indicates that 30 years is not enough for the recovery of the Carbon timber stock as the unlogged forests had a 77.7%.This calls for a review of forest management silvicultural activities for sustainable forest management.展开更多
The study investigated using rice husk biochar(RHB)to immobilize TNT and RDX explosives in soil at demining sites in Amuru District,Uganda.RHB produced via pyrolysis at 550℃was applied at a rate of 5%w/w to soil samp...The study investigated using rice husk biochar(RHB)to immobilize TNT and RDX explosives in soil at demining sites in Amuru District,Uganda.RHB produced via pyrolysis at 550℃was applied at a rate of 5%w/w to soil samples spiked at 50μg·g^(−1)RDX or TNT.The Liquid chromatography-tandem mass spectrometer(LC-MS/MS)analysis showed that the RHB immobilized 56%-67%of RDX and 55%-69%of TNT.The biochar’s porous structure and surface functional groups facilitated the explosive adsorption,reducing bioavailability.This demonstrates RHB’s effectiveness as an environmentally friendly and cost-effective remediation strategy.展开更多
Oilfield Q is a typical heavy oil reservoir,characterized by high porosity,high permeability,high crude oil viscosity,active edge and bottom water,and loose reservoirs that are prone to sand production.Since it was pu...Oilfield Q is a typical heavy oil reservoir,characterized by high porosity,high permeability,high crude oil viscosity,active edge and bottom water,and loose reservoirs that are prone to sand production.Since it was put into production in 2001,good development results have been achieved through comprehensive management measures such as optimized water flooding,infill well adjustment,separate-layer series development,and well pattern modification.It has now entered the late stage of development,showing characteristics such as rapid water cut rise,significant production decline,and low water flooding efficiency.Through the study of mechanism models,this paper screens out suitable blocks and optimizes the cyclic water injection parameters,achieving good results.It can provide a theoretical basis and reference for improving the development effect of heavy oil reservoirs in the ultra-high water cut stage.展开更多
Nano zero valent iron particles (nZVI) are popular the last few years because of the numerous applications in remediation of a wide range of pollutants in contaminated soils and aquifers. The nZVI particles can be 10 ...Nano zero valent iron particles (nZVI) are popular the last few years because of the numerous applications in remediation of a wide range of pollutants in contaminated soils and aquifers. The nZVI particles can be 10 - 1000 times more reactive than granular or micro-scale ZVI particles due to the small particle size, large specific surface area and high reactivity. An alternative green synthesis procedure was used for the production of nano zero valent iron particles (nZVI) using green tea (GT) extract, which is characterized by its high antioxidant content. Polyphenols in green tea extract possess double role in the synthesis of nZVI, because they not only reduce ferric cations, but also protect nZVI from oxidation and agglomeration as capping agents. The objective of current study was to simulate ata laboratory scale the attachment of GT-nZVI particles on soil material and study the effectiveness of attached nanoparticles for removing hexavalent chromium (Cr(VI)) from contaminated groundwater flowing through the porous soil bed. Column tests were carried out with various flowrates in order to examine the effect of contact time between the attached on porous medium nZVI and the flow-through solution on Cr(VI) reduction. After the completion of column tests the soil material in each column was split in 5 vertical sections, which were further subjected to chemical analyses and leaching tests. According to the results of the study increasing the contact time favors the reduction and removal of Cr(VI) from the aqueous phase. The reductive precipitation of Cr can be described as a reaction that follows a pseudo-first order kinetic law, with rate constant equal to k = 0.0243 ± 0.0011 min-1. Leaching tests indicated that precipitated chromium is not soluble. In the examined soil material, the total amount of precipitated Cr was found to range between 280 and 890 mg/(kg soil), while soluble Cr was less than 1.4 mg/kg and most probably it was due to the presence of residual Cr(VI) solution in the porosity of soil.展开更多
文摘This study examines how Algeria’s winter(December-February,DJF)rainfall is affected by the trends and variability of the Mediterranean Sea Surface Temperature(SST)between 1993 and 2023.Empirical Orthogonal Function(EOF)analysis and composite diagnostics were used to identify dominant SST modes and their atmospheric linkages using high-resolution datasets(ERSST,CHIRPS,and NCEP/NCAR reanalysis).The second Mediterranean SST mode(EOF2),which is the main cause of rainfall variability in Algeria,accounts for 25.3%of the variance in SST and is distinguished by a zonal dipole(eastern cooling vs.western warming).The associated atmospheric patterns show that whereas cool phases reduce precipitation through anticyclonic conditions and subsidence,warm SST phases increase rainfall through cyclonic circulation,increased vertical motion,and moisture flux convergence.The study concludes that the interannual and annual variation of Mediterranean SST is one of the key regulators of the winter hydroclimate in Algeria,and it has important implications,for the variability of water resources in the region.The importance of interannual SST variability over long-term trends in regulating Algeria’s winter hydroclimate is also highlighted by these findings,which are worth studying in the future.
文摘Heavy metal contamination from Artisanal and Small-Scale Gold Mining(ASGM)is increasingly recognized as a global issue,impacting soil quality and public health.In Tanzania,while ASGM activities significantly bolster local economies,they also pose serious environmental risks.This study examined the levels and dispersion of heavy metals,specifically mercury(Hg),lead(Pb),arsenic(As),zinc(Zn),and cadmium(Cd)in the Chunya district.Soil samples were collected from both active and abandoned tailing heaps and analysed by Atomic Absorption Spectroscopy(AAS),with the results compared to the WHO/FAO(2008)guidelines for agricultural soils.The findings revealed alarming concentrations of Hg across all sampling points,ranging from 0.88 to 3.72 mg·kg^(−1).In contrast,48 out of 51 sampling points exhibited higher Cd levels between 0.98 and 4.42 mg/kg,exceeding the safe limits of 0.5 mg·kg^(−1)for Hg and 0.8 mg·kg^(−1)for Cd.In contrast,the negative control site showed much lower levels(0.03mg·kg^(−1)for Cd and 0.43 mg·kg^(−1)for Hg).A notable decrease in heavy metal concentrations was observed with increasing distance from the tailing heaps(0 m to 200 m).Soil pH and electrical conductivity significantly influenced the mobility of these contaminants,with higher concentrations found near lower tailing heaps.The elevated levels of Hg and Cd present substantial risks to human health and ecosystems,highlighting the urgent need for effective remediation strategies.Furthermore,the gold mining industry must innovate technologies that minimize heavy metal release during extraction processes to mitigate environmental harm.
文摘The genesis mechanism of low-resistivity oil formation in the medium-deep Shahejie Formation of Bohai C Oilfield is unclear,and there is a lack of effective methods for identifying low-resistivity oil layers.This article conducts a comprehensive analysis based on core sample experiments,and research shows that the formation of low-resistivity oil layers in the oilfield is mainly caused by the superposition of three factors:1)microcapillary development,high irreducible water;2)additional conductive effect of clay;3)deep invasion of high salinity mud filtrate.The low-resistivity oil layer in this oilfield is mainly characterized by high mud content and strong additional conductivity of clay,and the complex pore throat structure leads to high irreducible water saturation,and the impact of saline mud intrusion,resulted in low-resistivity oil layers.The oil-field is mainly a lightweight oil layer with hydrophilic wettability,studying the response characteristics of oil and water layers through core nuclear magnetic resonance experiments,effectively identifying low-resistivity oil layers based on the correlation between resistivity and physical properties.
文摘This study investigates the Benxi Formation sandstone reservoirs in the Yanchuan East Block of the Ordos Basin,employing an integrated approach that includes core observation,thin-section analysis,scanning electron microscopy,high-pressure mercury intrusion,and petrophysical testing to systematically evaluate reservoir petrographic features and pore structures.Results reveal that Benxi Formation sandstones predominantly comprise quartz sandstones,lithic quartz sandstones,and lithic sandstones,characterized by high quartz content,widespread volcanic lithic fragments,moderately well-sorted grains,and complex cement types.Pore types are dominated by residual intergranular and dissolution pores,with minor intracrystalline pores and fractures;overall porosity ranges from 0.17%to 9.07%(average 4.74%),and permeability from 0.01 to 6.05 mD,classifying them as ultra-low porosity and tight reservoirs.High-pressure mercury intrusion indicates microfine throats as the primary structure,divisible into four distinct types.Diagenetically,compaction and cementation are the main drivers of primary pore loss and reservoir tightening,whereas late-stage dissolution partially ameliorates pore networks.Overall,Benxi Formation sandstone reservoirs exhibit pervasive densification but localized favorable pore assemblages and connectivity,facilitating hydrocarbon migration and accumulation.These findings advance understanding of Upper Paleozoic tight sandstone reservoir characteristics and aid in predicting sweet spots.
文摘Harmful algal blooms(HABs)pose a growing threat to aquatic ecosystems,human health,and economies worldwide.Climate change and nutrient enrichment have driven an increase in both the size and frequency of blooms,making accurate observation more urgent than ever.Remote sensing has become a critical tool for monitoring HABs,yet commonly used multispectral instruments such as MODIS,Landsat,and Sentinel face major limitations.Their coarse spatial resolution prevents reliable observation in smaller inland waters,long revisit times restrict timely monitoring,and limited spectral bands reduce the ability to discriminate key pigments like chlorophyll a and phycocyanin.In contrast,hyperspectral sensors capture hundreds of narrow,contiguous bands at higher spatial,temporal,and radiometric resolutions,enabling the detection of subtle phytoplankton characteristics and bloom dynamics across diverse environments.Hyperspectral imagers mounted on unmanned aerial systems further provide near-daily data collection,making them especially effective for tracking bloom evolution.While forecasting remains an emerging application,hyperspectral observation offers the clearest path forward for improving HAB detection and monitoring.This paper reviews the advantages of hyperspectral remote sensing over multispectral approaches and argues for its adoption as an essential technology in safeguarding aquatic health and mitigating the rising global risk of HABs.
基金supported by the Innovation and Entrepreneurship Training Program for College Students in Yunnan Province,with the project title“Analysis of the Impact of Spatiotemporal Distribution of Drought on Forest Fire Risk Levels and Its Trend in Dali Prefecture”.
文摘Drought is one of the primary meteorological disasters affecting Dali Prefecture.This study employs the Integrated Meteorological Drought Index(IMDI)to systematically analyze the spatiotemporal evolution characteristics of mete-orological drought in Dali Prefecture from 2002 to 2023.Using linear trend analysis,spatial interpolation,and meteorological statistical methods,the key findings are as follows:interannual drought frequency fluctuated between 5.3%and 34.2%,with a mean of 24.3%;the 2019 extreme drought event showed significant correlation with concurrent Indian Ocean sea surface temperature anomalies;spatially,drought frequency exhibited a north-high-southlow pattern,ranging from 23.1%in the south to 29.8%in the north,with northern counties(e.g.,Jianchuan,Heqing)recording the maximum frequency(29.8%)resulting from the föhn effect on the leeward slope of the Nushan Mountains and high agricultural water consumption;annual drought duration increased significantly at 1.9 days/decade;seasonally,droughts intensified in spring(+0.62 days/decade)and winter(+1.5 days/decade)but weakened in summer(−0.8 days/decade)and autumn(−0.4 days/decade),a pattern poten-tially linked to East Asian monsoon weakening causing reduced winter-spring moisture transport;for drought severity,light drought dominated(annual mean:42.5 days,58%of total drought days)followed by progressively shorter durations of moderate,severe,and extreme drought,while combined severe/extreme drought duration increased at 0.7 days/decade,consistent with regional warming and increased evapotranspiration.This study elucidates the spatio-temporal drought patterns and climatic drivers in Dali Prefecture,providing a scientific basis for drought resilience planning and optimized water resource allocation in this plateau marginal region.
基金supported financially by the EFCTC trade association.
文摘The publication of trifluoroacetic acid(TFA)concentrations in the Atlantic Ocean in 2022-2023 prompted an inventory update to include the period 2000 to 2020 for fluorspar(CaF2)production,use,TFA emissions,and their contri-bution to TFA in the Atlantic Ocean.The update accounts for 90%of the acid spar used to produce hydrogen fluoride in the period 2000 to 2020.Emissions of TFA due to fluorocarbons(HFCs,HFOs,HCFOs,HCFCs,and anaesthetics)are estimated at 503,700 tonnes in this period.Generation of TFA from the use of pesticides is estimated at 239,000 to 796,000 tonnes globally,assuming a 30%to 100%yield of TFA.In total,estimated emissions of TFA,from 1930 to 2020,are 1,019,000 tonnes,with a theoretical upper limit of 2,283,000 tonnes,which includes the quantity of TFA manufactured,where production is assumed to equal emissions.The estimated emissions of TFA to the Atlantic Ocean from 1930 to 2020 are 467,000 tonnes,with a theoretical upper limit of 1,215,000 tonnes.This is not consistent with the measured TFA concentrations,which suggest the Atlantic Ocean contains at least 40 million tonnes of TFA,possibly over 80 million tonnes,and must therefore include a large natural burden.
文摘Expansive soils present a significant geohazard to light infrastructure world-wide,causing costly damage through swelling and shrinkage cycles driven by moisture content changes.One key property controlling this behavior,the Cation Exchange Capacity(CEC),is complex and expensive to measure directly,making it necessary to find reliable and affordable proxies for initial site assessments.This study introduces and validates a novel parameter,the weighted plasticity index(wPI),for classifying the swelling potential of expansive clays.Twenty-six soil samples,representing a range from low to high plasticity clays from Trinidad,underwent standard geotechnical laboratory tests,including Atterberg limits and grain size analysis.The wPI was calculated for each sample as the product of its Plasticity Index(PI)and the percentage of fine particles(percent passing the 425-μm sieve).A strong linear relationship(R^(2)=0.94)was found between the wPI and the Liquid Limit(LL).Using a previously established relationship between LL and CEC,a robust mathematical model connecting wPI directly to CEC was derived.This model formed the basis for a new four-tiered swelling potential classification system(Low,Medium,High,and Very High)based on the calculated wPI values.The wPI method provides a reliable,quick,and cost-effective tool for geotechnical engineers to evaluate swelling potential,promoting the design of more resilient and sustainable infrastructure in areas prone to expansive soils.
文摘In Oilfield B of the Bohai Bay Basin,the shallow-water delta sandbody reservoirs are thin and exhibit rapid lateral changes.Local incised superposition results in complex oil-water relationships within the sandbodies and uneven plane injection-production response,which restricts the efficient tapping of remaining oil.Based on data such as drilling cores,geochemical analysis,well logging,and seismic data,the sedimentary characteristics of the lobate shallowwater delta are determined.Through seismic forward modeling,the seismic waveform characteristics of different sand body stacking patterns are summarized to guide the fine description of composite sand body stacking patterns and single-stage sand body plane distribution patterns.The results show that:by using identification markers such as the discontinuous,superimposed,and elevation difference characteristics of event axes on inverted seismic profiles,as well as the variation zones of planar seismic attributes,2 phases of composite channels can be divided.Five types of sandbody contact patterns were summarized,including discrete contact,lateral cutting contact,natural levee connection,vertical aggradation superimposition,and composite superimposition.Combined with the results of fine characterization of sand bodies,based on the single-phase channel and river-bar lobes,the remaining oil distribution law is summarized,the oil-water relationship and remaining oil distribution of the river-bar composite sand body are jointly controlled by the cutting interface of the sand body and the rhythm pattern of the composite sand body,and the potential tapping strategies such as improving the single-phase channel well pattern,river-bar lobes well pattern reconstruction and local encryption are proposed.The successful implementation of 24 adjustment wells and the successful production of 100 m3/d from 9 new adjustment wells demonstrates that the fine characterization method and resulting residual oil predictions are reasonable and credible,and provide reference for the development,production and potential mining of similar oilfields.
基金supported by Ningxia Natural Science Foundation Project(2023AAC02088)Liangshan Prefecture 2023 Annual Science and Technology Planning Project(23ZDYF0182).
文摘Under the context of global climate change,the frequent occurrence of strong winds in Guyuan has significantly hindered the development of local facility agriculture.Using hourly meteorological data from the Sanying National Station and the Guyuan Greenhouse Station between April 2024 and April 2025,this study employed machine learning methods to develop wind speed prediction models based on BP neural network,support vector machine,and random forest(referred to as BP,SVM,and RF models),aiming to provide references for local disaster prevention and mitigation.The results indicate that:1)Wind speed at the Guyuan Greenhouse Station exhibits the strongest correlation with that at the National Station(0.489-0.595),followed by temperature and 24-hour precipitation(0.116-0.336).2)The mean absolute error(MAE)of the BP,RF,and SVM models at all heights is below 1.5 m/s,the root mean square error(RMSE)is under 2.1 m/s,and the forecast accuracy(FA)exceeds 75%,indicating satisfactory model performance.Compared to 3 m,the MAE and RMSE of 0.5 m are larger,while the FA is smaller.This indicates that the wind speed of 0.5 m is close to the ground,and is more affected by surface roughness and turbulence effects,resulting in greater randomness and making the model more difficult.3)Based on case analyses of May 10 and May 1,2024,the overall simulation performance ranks as“RF model>SVM model>BP model”;however,the SVM model demonstrates higher accuracy in simulating strong wind events.
文摘Antimicrobial pollution in surface waters has become an urgent environmental issue globally,yet few studies have specifically focused on the prevalence and impacts of antimicrobial contaminants in Tanzanian surface waters.This review article presents a comprehensive assessment of antimicrobial pollutants in Tanzania’s aquatic ecosystems,filling a critical gap in the current literature.The findings reveal widespread contamination of surface waters,primarily with antibiotics,from diverse sources,including domestic sewage,agricultural runoff,industrial effluents,and healthcare facilities.This work integrates findings from a range of disciplines,including environmental monitoring,public health,and agricultural practices,to provide a holistic understanding in the Tanzanian context.The presence of antimicrobial pollutants may lead to the promotion of antimicrobial resistance,disruption of microbial communities,and risks to human health through food chain.Therefore,there is a call for further studies to assess the extent of antimicrobial pollution in Tanzania and its broader implications for both environmental and public health.
文摘The sandstone reservoir of the Shanxi Formation serves as a key exploration and development target in the eastern Yanchuan gas field of the Ordos Basin,where its physical properties and pore structure directly govern the enrichment and distribution of hydrocarbons.This study systematically examines the petrological features,pore types,throat structures,and petrophysical parameters of the Shanxi Formation sandstone reservoir using core observation,thin-section identification,cast thin-section and scanning electron microscopy analyses,mercury injection porosimetry,and conventional petrophysical testing.Results indicate that the reservoir predominantly comprises fine-to mediumgrained sandstones,dominated by lithic sandstones,lithic quartz sandstones,and quartz sandstones as the primary lithofacies assemblages.Detrital components are chiefly quartz and metamorphic rock fragments,with cementation primarily of the pore-filling type and common siliceous and carbonate cements.Dominant pore types include dissolution pores in volcanic lithics,residual intergranular pores,and minor intercrystalline pores and microfractures.Porosity is generally low,averaging less than 6%,with permeability ranging from 0.001 to 5.577 mD.Mercury injection experiments reveal that throat sizes are predominantly small,exhibiting poor sorting and limited connectivity,classifying the reservoir overall as an ultra-low-porosity,tight type,though locally high-quality sandstone intervals are developed.Integrated analysis highlights pronounced heterogeneity in the Shanxi Formation reservoir,wherein pore preservation and dissolution processes exert significant enhancement on reservoir quality,while microfractures play a pivotal role in hydrocarbon migration and accumulation.These findings offer valuable insights for reservoir evaluation and natural gas exploration and development in the Shanxi Formation of the eastern Yanchuan gas field.
基金supported by the 2024 Science and Technology Plan Project of Sichuan Province[grant number 2024YFTX0016]the Undergraduate Innovation and Entrepreneurship Training Program[grant number S202510621001].
文摘This study analyzes the spatiotemporal patterns and driving factors of forest fires in Liangshan Prefecture based on fire data from 2016 to 2024 using statistical methods.The results indicate:1)From 2016 to 2024,forest fires in Liangshan Prefecture occurred predominantly between January and May(140 incidents),accounting for 97.90%of the total.March recorded the highest number of fires(48 incidents),representing 33.57%.Within a 24-hour period,113 fires occurred between 12:00 PM and 9:00 PM,constituting 79.02%of all incidents.2)Spatially,Mianning County recorded the highest number of forest fires(28 incidents,19.58%),followed by Xichang,Muli,and Yanyuan with 22,23,and 20 incidents,respectively.Human activities,particularly agricultural burning,outdoor smoking,and other causes,were the dominant factors,collectively accounting for 41%of incidents.3)Forest fires predominantly occurred at elevations between 1500 and 3000 meters(132 fires,92.31%),on slopes with gradients of 5-25 degrees(81 fires,56.65%),on west-facing aspects(northwest,west,southwest)(72 fires,53.14%),in areas with NDVI values between 0.51 and 0.8(79 incidents,55.24%),within 500-2000 m residential buffer zones(151 incidents,98.60%),and within 500 m road buffer zones(103 incidents,72.03%).4)Among meteorological factors,the 20-day average temperature(0.3041),80-day maximum temperature(0.3487),20-day minimum temperature(0.2594),20-day minimum relative humidity(−0.3132),70-day maximum wind speed(0.1885),and 70-day peak wind speed(0.1965)showed the strongest correlations with forest fire burned area.Burned area also exhibited a positive correlation with the Meteorological Drought Index(MCI)on the day of the fire(0.1990).This study confirms the lagged and persistent effects of meteorological factors on forest fire occurrence,providing key scientific evidence for constructing regional fire prediction models that integrate multi-scale meteorological indicators.
文摘The Quasi-Biennial Oscillation(QBO)is a vital mode of stratospheric variability with significant influence on tropical and subtropical climate systems.However,its influence on precipitation variability across Eastern and Southern Africa remains insufficiently understood.This study examines the impact of the QBO on summer precipitation and associated circulation anomalies over Eastern and Southern Africa from 1979 to 2021.Using ERA5 and NOAA reanalysis datasets,we applied composite and correlation analyses to assess precipitation responses to westerly(WQBO)and easterly(EQBO)phases.Results show a dipole-like pattern,with WQBO linked to enhanced precipitation in both Eastern and Southern Africa,while EQBO is associated with reduced precipitation.Circulation analysis reveals that WQBO phases promote upper-level divergence,low-level moisture inflow,and vertical ascent,whereas EQBO phases enhance subsidence and upperlevel convergence.These findings highlight the QBO role in modulating precipitation through stratosphere-troposphere coupling and its interaction with regional circulation patterns.The quasi-periodic nature of QBO offers substantial potential for enhancing seasonal precipitation predictions when integrated with other regional circulations,such as the Botswana High and the Angola Low.
文摘A geostatistical study was conducted with the objective of developing a better understanding of the sediments deposited in the tailings dam of an iron mine located in Brazil.The samples,derived from two drilling campaigns conducted in 2001 and 2010,were statistically evaluated and validated for the construction of both a 3D geological model and an estimated model.The geological body modeling process was performed using an implicit method,which was based on the interpretation and adjustments of vertical sections and considered the positions of the samples and the grades of the chemical components of interest.In addition,the primitive topography was also considered to determine the base and limits of the deposit,as well as the current topography.The ordinary kriging(OK)method was chosen to estimate the grades of the chemical components and the retained/passing percentages of the particle size fractions described in the samples.The kriging model was validated through two analyses:mean comparison and drift analyses.The total tonnage of the estimated model was 287.14 Mt,with an average Fe grade of 63.89%.
基金ECMWF-ERA5 and NOAA for making their data available.
文摘The Quasi-Biennial Oscillation(QBO)is a dominant mode of interannual variability in the tropical stratosphere,known to influence global weather and climate patterns through stratosphere-troposphere coupling.While its impacts on the Northern Hemisphere are well-documented,its role in the Southern Hemisphere subtropical climate remains less explored.This study investigates the relationship between the QBO and September surface air temperature(SAT)over Southern Africa during the early austral spring from 1979 to 2021.We find that the QBO’s easterly phase(EQBO)at 50 hPa is associated with a significant dipole pattern in SAT,characterized by warming over southeastern Africa and cooling along the southwestern coastal area.Analysis reveals that this temperature pattern is driven by a coherent teleconnection pathway:the EQBO forces a quasi-barotropic geopotential height anomaly,which modulates vertical velocity,leading to enhanced convection and increased cloud cover over the cooling region and suppressed convection over the warming area.Outgoing Longwave Radiation data confirm this dipole in convective activity.A latitudinal-vertical cross-section demonstrates the descent of QBOrelated wind anomalies into the subtropical troposphere,outlining the direct stratospheric pathway for this distant influence.Our results identify the QBO as a key stratospheric precursor for early spring temperature variability in Southern Africa,with important implications for improving regional seasonal forecasting.
基金supported by the International Tropical Timber Organisation(ITTO)grantthe equipment grant was provided by IDEA WILD+2 种基金the Carnegie Corporation of New York through the Future Africa Research Leadership(FAR-LeaF)grant of the University of Pretoriasupported the fieldwork and data analyses,the mobility grant and research modernization allowance of the Ministry of Higher Education(MINESUP)Cameroonthe Fako America Scholarship.
文摘Tropical forests have large carbon stocks and their conservation is a very important mitigation measure against global warming.However,this carbon pool is the most vulnerable to anthropogenic activities like selective logging and little is known about its recovery.This study aimed to determine the carbon stock recovery after selectively logging using different allometric equations in six 1 ha permanent monitoring plots established in logged and unlogged forest types.Each 1 ha was divided into 25,20×20 m and the DBH of all trees≥2 cm was measured in 2005/2006 and re-measured in 2011/2012.The logged forests had the highest%change in the species richness indicating the impacts of logging.The presence of exploitable commercial trees in both forest types suggests their recruitment after logging.The insignificant difference in the AGB using different allometric equations is an indication that the Pan tropical equation is a good reference for the calculations of AGB in moist tropical forests.The 59.4%recovery rate in forests of 21 YAL indicates that 30 years is not enough for the recovery of the Carbon timber stock as the unlogged forests had a 77.7%.This calls for a review of forest management silvicultural activities for sustainable forest management.
文摘The study investigated using rice husk biochar(RHB)to immobilize TNT and RDX explosives in soil at demining sites in Amuru District,Uganda.RHB produced via pyrolysis at 550℃was applied at a rate of 5%w/w to soil samples spiked at 50μg·g^(−1)RDX or TNT.The Liquid chromatography-tandem mass spectrometer(LC-MS/MS)analysis showed that the RHB immobilized 56%-67%of RDX and 55%-69%of TNT.The biochar’s porous structure and surface functional groups facilitated the explosive adsorption,reducing bioavailability.This demonstrates RHB’s effectiveness as an environmentally friendly and cost-effective remediation strategy.
文摘Oilfield Q is a typical heavy oil reservoir,characterized by high porosity,high permeability,high crude oil viscosity,active edge and bottom water,and loose reservoirs that are prone to sand production.Since it was put into production in 2001,good development results have been achieved through comprehensive management measures such as optimized water flooding,infill well adjustment,separate-layer series development,and well pattern modification.It has now entered the late stage of development,showing characteristics such as rapid water cut rise,significant production decline,and low water flooding efficiency.Through the study of mechanism models,this paper screens out suitable blocks and optimizes the cyclic water injection parameters,achieving good results.It can provide a theoretical basis and reference for improving the development effect of heavy oil reservoirs in the ultra-high water cut stage.
文摘Nano zero valent iron particles (nZVI) are popular the last few years because of the numerous applications in remediation of a wide range of pollutants in contaminated soils and aquifers. The nZVI particles can be 10 - 1000 times more reactive than granular or micro-scale ZVI particles due to the small particle size, large specific surface area and high reactivity. An alternative green synthesis procedure was used for the production of nano zero valent iron particles (nZVI) using green tea (GT) extract, which is characterized by its high antioxidant content. Polyphenols in green tea extract possess double role in the synthesis of nZVI, because they not only reduce ferric cations, but also protect nZVI from oxidation and agglomeration as capping agents. The objective of current study was to simulate ata laboratory scale the attachment of GT-nZVI particles on soil material and study the effectiveness of attached nanoparticles for removing hexavalent chromium (Cr(VI)) from contaminated groundwater flowing through the porous soil bed. Column tests were carried out with various flowrates in order to examine the effect of contact time between the attached on porous medium nZVI and the flow-through solution on Cr(VI) reduction. After the completion of column tests the soil material in each column was split in 5 vertical sections, which were further subjected to chemical analyses and leaching tests. According to the results of the study increasing the contact time favors the reduction and removal of Cr(VI) from the aqueous phase. The reductive precipitation of Cr can be described as a reaction that follows a pseudo-first order kinetic law, with rate constant equal to k = 0.0243 ± 0.0011 min-1. Leaching tests indicated that precipitated chromium is not soluble. In the examined soil material, the total amount of precipitated Cr was found to range between 280 and 890 mg/(kg soil), while soluble Cr was less than 1.4 mg/kg and most probably it was due to the presence of residual Cr(VI) solution in the porosity of soil.
