Globally,sub-optimal use of nitrogen (N) fertiliser and elevated N irrigation groundwater have led to high leached nitrate (NO_(3)^(–)) losses from protected vegetable field systems.Optimising fertiliser and irrigati...Globally,sub-optimal use of nitrogen (N) fertiliser and elevated N irrigation groundwater have led to high leached nitrate (NO_(3)^(–)) losses from protected vegetable field systems.Optimising fertiliser and irrigation management in different soil types is crucial to reduce future N loads from such systems.The present 4-year study examined leached N loads from lysimeter monitoring arrays set up across 18 protected vegetable system sites encompassing the dominant soil types of northern China.The treatments applied at each field site were:1) a high N and high irrigation input treatment (HNHI);2) a low N but high irrigation input treatment (LNHI) and 3) a low N with low irrigation input treatment (LNLI).Results showed that the mean annual leached total nitrogen loads from the HNHI,LNHI and LNLI treatments were 325,294 and 257 kg N ha^(–1) in the fluvo-aquic soil,114,100 and 78 kg N ha^(–1) in the cinnamon soil and 79,68 and 57 kg N ha^(–1) in the black soil,respectively.The N dissolved in irrigation water in the fluvo-aquic soil areas was 8.26-fold higher than in the cinnamon areas.A structural equation model showed that N fertiliser inputs and leaching water amounts explained 14.7 and 81.8%of the variation of leached N loads,respectively.Correspondingly,reducing irrigation water by 21.5%decreased leached N loads by 20.9%,while reducing manure N and chemical N inputs by 22 and 25%decreased leached N loads by only 9.5%. This study highlights that protected vegetable fields dominated by fluvo-aquic soil need management to curtail leached N losses in northern China.展开更多
Scientific knowledge on the chemical compositions of fine particulate matter(PM_(2.5)) is essential for properly assessing its health and climate effects,and for decisionmakers to develop efficient mitigation strategi...Scientific knowledge on the chemical compositions of fine particulate matter(PM_(2.5)) is essential for properly assessing its health and climate effects,and for decisionmakers to develop efficient mitigation strategies.A high-resolution PM_(2.5) chemical composition dataset(CAQRA-aerosol)is developed in this study,which provides hourly maps of organic carbon,black carbon,ammonium,nitrate,and sulfate in China from 2013 to 2020 with a horizontal resolution of 15 km.This paper describes the method,access,and validation results of this dataset.It shows that CAQRA-aerosol has good consistency with observations and achieves higher or comparable accuracy with previous PM_(2.5) composition datasets.Based on CAQRA-aerosol,spatiotemporal changes of different PM_(2.5) compositions were investigated from a national viewpoint,which emphasizes different changes of nitrate from other compositions.The estimated annual rate of population-weighted concentrations of nitrate is 0.23μg m^(−3)yr^(−1) from 2015 to 2020,compared with−0.19 to−1.1μg m^(−3)yr^(−1) for other compositions.The whole dataset is freely available from the China Air Pollution Data Center(https://doi.org/10.12423/capdb_PKU.2023.DA).展开更多
Acid-base dissociable antibiotic-metal complexes are known to be emerging contaminants in the aquatic environments.However,little information is available on the photochemical properties and toxicity of these complex ...Acid-base dissociable antibiotic-metal complexes are known to be emerging contaminants in the aquatic environments.However,little information is available on the photochemical properties and toxicity of these complex forms.This study investigated the spectral properties of three fluoroquinolones(FQs)with and without metal ions Fe(III),Cu(II),and Al(III)in solutions under different pH conditions,as well as evaluated the changes in toxicity due to the complex with thesemetal ions using luminescent bacteria(vibrio fischeri).FQs showed a higher tendency to coordinate metal ions under alkaline conditions compared to neutral and acidic conditions,and the formation of complexes weakened the ultravioletabsorbing ability of FQs.At pH=7.0,Cu(II)quenched the fluorescence intensity of FQs.Moreover,their Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy were explored,revealing that the coordination sites of Cu(II)in three FQs were situated in a bidentate manner through the oxygen atom of the deprotonated carboxyl group and cyclic carbonyl oxygen atom.This conclusion was further verified by the theory of molecular surface electrostatic potential.In addition,except for complexes of ciprofloxacin-metals,enhanced toxicity of FQs upon coordination with Fe(III)was observed,while reduced toxicity was found for coordination with Cu(II)and Al(III).These results are important for accurately evaluating the photochemical behavior and risk of these antibiotics in aquatic environments contaminated with metal ions.展开更多
Migratory insect pests tend to suddenly immigrate into new habitats over a short period to simultaneously lay eggs in clusters,resulting in gregarious larvae that cause severe damage to crops.These aggregated larvae c...Migratory insect pests tend to suddenly immigrate into new habitats over a short period to simultaneously lay eggs in clusters,resulting in gregarious larvae that cause severe damage to crops.These aggregated larvae can adapt well to various natural enemies and pathogens in their new habitats,but how their resistance might be enhanced and its immunological significance remain unknown.Here,we examined how infection by a pathogen and a parasitic fly affect the immune response and migratory behavior in two phases of the oriental armyworm,Mythimna separata,which differ dramatically in their flight capacity and fecundity.The gregarious larvae displayed greater resistance than solitary larvae to the challenges of both the entomopathogenic fungus Metarhizium anisopliae and the parasitoid Exorista civilis.In response to a challenge by M.anisopliae,gregarious larvae exhibited more pronounced increases in phenoloxidase(PO)activity and lysozyme activity than solitary larvae.Furthermore,in addition to the greater PO and lysozyme activities,the levels of dopamine and 5-hydroxytryptamine(5-HT)were also greater in challenged gregarious and solitary larvae.Injection of dopamine(or 5-HT)significantly enhanced PO activity,lysozyme activity,antibacterial activity and larval survival.Subsequently,there was a significant increase in the flight capacity of adults derived from gregarious larvae challenged by M.anisopliae;while no significant variation was observed in the adults from challenged solitary larvae.The preoviposition period,oviposition period and fecundity were not significantly affected by M.anisopliae,regardless of whether the larvae were gregarious or solitary.These results provide new insights into the relationship between migration and immunity in insects,and their behavior after immunization.展开更多
Little Terns Sternula albifrons are estuarine birds extensively using increasingly urbanized coastal areas.Given the increased exposure of these ecosystems to anthropogenic activities,it is crucial to study the ecolog...Little Terns Sternula albifrons are estuarine birds extensively using increasingly urbanized coastal areas.Given the increased exposure of these ecosystems to anthropogenic activities,it is crucial to study the ecology of this species and interactions with human stressors to establish management measures.We collected regurgitates(n=182)and blood samples(n=48)to study Little Terns’diet,health condition and isotopic niche,and individually tracked breeding adults(n=9,during 2021 and 2022)at 2 sandy beaches 21 km apart and located within Ria Formosa Natural Park,Algarve,Portugal.Although both areas are adjacent to foraging coastal marine areas and an estuarine lagoon system with saltpans,they differ in human disturbance.We also compared breeding success and adult health measures between these 2 colonies.The main prey for both populations were Sand Smelts Atherina spp.and Gobies Pomatoschistus spp.,and no differences in δ^(13)C and δ^(15)N stable isotopic values between colonies were found.Tracking data revealed that individuals foraged in the surroundings of their breeding colonies.Entrance Channels and Ocean were the most frequently used habitats for foraging by individuals from the less disturbed colony.Adults from the more disturbed colony foraged mostly in Entrance Channels.Overall,all individuals tended to forage during daytime.There were no differences in health measures of individuals between colonies,though breeding success at the most disturbed colony was comparably lower.It is important to protect both breeding areas and adjacent foraging habitats for Little Terns,particularly given the expected increasing pressure from human activities on coastal areas worldwide.展开更多
Two new species of Leptobrachella are described from Vietnam based on morphological differences and genetic divergences in 16S rRNA mitochondrial gene sequences.The new taxa are distinguished from each other and from ...Two new species of Leptobrachella are described from Vietnam based on morphological differences and genetic divergences in 16S rRNA mitochondrial gene sequences.The new taxa are distinguished from each other and from other species of the genus Leptobrachella in body size,head width/length ratio,tympanum morphology,dorsal skin texture,the presence/absence of fringes on toes,color of dorsal and ventral body,and iris color.The two new species are also divergent from each other and from other congeners by a 4.14% or greater uncorrected genetic distance.Leptobrachella batxatensis sp.nov.is genetically closest to L.shiwandashanensis and L.wuhuangmontis from China.Leptobrachella duyenae sp.nov.is genetically closest to L.bidoupensis from Vietnam with strong nodal support from both BI and ML analyses(1.0/99%).展开更多
Occurrence and abundance of molecular hydrogen in natural geologic reservoirs are enigmatic,due to its various sources,diverse migration pathways and complicated biological and chemical reactions.Natural gas samples c...Occurrence and abundance of molecular hydrogen in natural geologic reservoirs are enigmatic,due to its various sources,diverse migration pathways and complicated biological and chemical reactions.Natural gas samples containing hydrogen from producing wells in several sedimentary basins in China were collected in this study,and gas abundances and isotopic compositions of these gases were compared with those in global petroliferous basins and deep intrusive rocks.Several geochemical indicators were suggested for identifying sources,migration and accumulation mechanisms of hydrogen in the subsurface environment.Hydrogen contents in natural gas deposits have contributions from various sources with the following high-to-low order:microbial degradation>serpentinization>deep mantle volatile release>radiation-induced water decomposition>thermal cracking of organic matter.A hydrogen-rich reservoir in Kansas,USA,is specifically analyzed to determine its formation mechanism.This study suggests that future exploration of geological hydrogen resources may focus on the igneous rock bodies with overlying dense sedimentary rocks in the continental rift systems.展开更多
As antibiotic pollutants cannot be incompletely removed by conventional wastewater treatment plants,ultraviolet(UV)based advanced oxidation processes(AOPs)such as UV/persulfate(UV/PS)and UV/chlorine are increasingly c...As antibiotic pollutants cannot be incompletely removed by conventional wastewater treatment plants,ultraviolet(UV)based advanced oxidation processes(AOPs)such as UV/persulfate(UV/PS)and UV/chlorine are increasingly concerned for the effective removal of antibiotics from wastewaters.However,the specific mechanisms involving degradation kinetics and transformation mechanisms are not well elucidated.Here we report a detailed examination of SO_(4)•−/Cl•-mediated degradation kinetics,products,and toxicities of sulfathiazole(ST),sarafloxacin(SAR),and lomefloxacin(LOM)in the two processes.Both SO_(4)•−/Cl•-mediated transformation kinetics were found to be dependent on pH(P<0.05),which was attributed to the disparate reactivities of their individual dissociated forms.Based on competition kinetic experiments and matrix calculations,the cationic forms(H_(2)ST^(+),H_(2)SAR^(+),and H_(2)LOM^(+))were more highly reactive towards SO_(4)•−in most cases,while the neutral forms(e.g.,HSAR^(0)and HLOM^(0))reacted the fastest with Cl•for the most of the antibiotics tested.Based on the identification of 31 key intermediates using tandem mass spectrometry,these reactions generated different products,of which the majority still retained the core chemical structure of the parent compounds.The corresponding diverse transformation pathways were proposed,involving S−N breaking,hydroxylation,defluorination,and chlorination reactions.Furthermore,the toxicity changes of their reaction solutions as well as the toxicity of each intermediate were evaluated by the vibrio fischeri and ECOSAR model,respectively.Many primary by-products were proven to be more toxic than the parent chemicals,raising the wider issue of extended potency for these compounds with regards to their ecotoxicity.These results have implications for assessing the degradative fate and risk of these chemicals during the AOPs.展开更多
Buffer material and metal disposal containers are the key engineering barriers in the geological disposal of high-level radioactive waste.The durability of disposal containers largely depends on the water con-tent in ...Buffer material and metal disposal containers are the key engineering barriers in the geological disposal of high-level radioactive waste.The durability of disposal containers largely depends on the water con-tent in buffer material.This work focused on investigating the corrosion evolution of NiCu low alloy steel in compacted GMZ bentonite with different water contents for 270 d by using weight loss,electrochemi-cal measurements,and various methods for analyzing corrosion products.As the water content increased from 13%to 20%,the water in the bentonite transformed from an unsaturated to a critical saturated state,and the corrosion rate of NiCu steel clearly increased.In these two systems,the oxygen could mi-grate to the thin liquid film on the steel surface through the air pores in the bentonite in the gas phase and undergo cathodic reduction.Meanwhile,it oxidized the ferrous hydrolysis products into ferric corro-sion products and formed a rust layer,which could block the diffusion of oxygen.At that moment,the cathodic process of NiCu steel corrosion changed to rust reduction.When the water content continually increased to 30%and 40%,the compacted bentonite was in a saturation state,and the corrosion rate of NiCu steel was significantly decreased.This was because most pores among the bentonite particles were occupied by a large amount of free water,which hindered the diffusion of oxygen and inhibited its cathodic reduction.Furthermore,it restrained the oxidation of ferrous corrosion products,which greatly weakened the cathodic depolarization of rust,leading to the cathodic process being dominated by the hydrogen evolution reaction.展开更多
Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load.Due to the complexity of biological s...Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load.Due to the complexity of biological structures,the underlying micro-behaviors involving time-dependent deformation are poorly understood.For this,an abnormal phenomenon was observed where the axial and lateral creep deformations were mutually independent by a series of triaxial tests under constant stress and strain rate conditions.The significantly large lateral creep deformation implies that the creep process cannot be described in continuum mechanics regime.Herein,it is hypothesized that sliding mechanism of crystal cleavages dominates the lateral creep deformation in coral reef limestone.Then,approaches of polarizing microscope(PM)and scanning electronic microscope(SEM)are utilized to validate the hypothesis.It shows that the sliding behavior of crystal cleavages combats with conventional creep micro-mechanisms at certain condition.The former is sensitive to time and strain rate,and is merely activated in the creep regime.展开更多
The Yangtze River economic belt(YREB),China is important to the Chinese economy and for supporting sustainable development.Clarifying the relationship between water quality indices and socioeconomic indicators could h...The Yangtze River economic belt(YREB),China is important to the Chinese economy and for supporting sustainable development.Clarifying the relationship between water quality indices and socioeconomic indicators could help improve aquatic environment management in the YREB and our understanding of the causes and effects of water quality variations in other large river basins.In this study,river water quality,factors affecting water quality,and management strategies,and correlations between water quality indices and socioeconomic indicators in the YREB during the 13th Five-Year Plan period(2016-2020)were assessed.The single-factor evaluation method,constant price for GDP,and correlation analyses were adopted.The results showed that:1)water quality in the YREB improved during the 13th Five-Year Plan period.The number of aquatic environment sections meeting GradeⅠ-Ⅲwater quality standards increased by 13.1%and the number below Grade V decreased by 2.9%.2)The values of 12 indicators in the YREB exceeded relevant standards.The indicators with highest concentreation were the total phosphorus,chemical oxygen demand,ammonia nitrogen,and permanganate index,which were relatively high in downstream regions in Anhui Province,Jiangsu Province,and Shanghai Municipality.3)Ammonia nitrogen,chemical oxygen demand,and total phosphorus emissions per unit area and water extraction per unit area are relatively high in the three downstream regions mentioned above.4)Increased domestic sewage discharges have increased total wastewater discharges in the YREB.5)River water quality in the YREB strongly correlated with population,economic,and water resource indices and less strongly correlated with government investment,agriculture,meteorology,energy,and forestry indices.This confirmed the need to decrease wastewater discharges and non-point-source pollutant emissions.The aquatic environment could be improved by taking reasonable measures to control population growth,adjusting the industrial structure to accelerate industrial transformation and increase the proportion of tertiary industries,and investing in technological innovations to protect the environment.展开更多
Studying the spatiotemporal distribution and transboundary transport of aerosols,NO_(2),SO_(2),and HCHO in typical regions is crucial for understanding regional pollution causes.In a 2-year study using multi-axis diff...Studying the spatiotemporal distribution and transboundary transport of aerosols,NO_(2),SO_(2),and HCHO in typical regions is crucial for understanding regional pollution causes.In a 2-year study using multi-axis differential optical absorption spectroscopy in Qingdao,Shanghai,Xi’an,and Kunming,we investigated pollutant distribution and transport across Eastern China-Ocean,Tibetan Plateau-Central and Eastern China,and China-Southeast Asia interfaces.First,pollutant distributionwas analyzed.Kunming,frequently clouded and misty,exhibited consistently high aerosol optical depth throughout the year.In Qingdao and Shanghai,NO_(2)and SO_(2),as well as SO_(2)in Xi’an,increased in winter.Elevated HCHO in summer in Shanghai and Xi’an,especially Xi’an,suggests potential ozone pollution issues.Subsequently,pollutant transportation across interfaces was studied.At the Eastern China-Ocean interface,the gas transport flux was the largest among other interfaces,with the outflux exceeding the influx,especially in winter and spring.The input of pollutants from the Tibetan Plateau to central-eastern Chinawas larger than the output in winter and spring,with SO_(2)having the highest transport flux in winter.The pollution input from Southeast Asia to China significantly exceeded the output,with spring and winter inputs being 3.22 and 3.03 times the output,respectively.Lastly,the transportation characteristics of a pollution event at Kunming were studied.During this period,pollutants were transported from west to east,with themaximum SO_(2)transport flux at an altitude of 2.87 km equaling 27.74μg/(m^(2)·s).It is speculated that this pollution was caused by the transport from Southeast Asian countries to Kunming.展开更多
The trends and characteristics of global CH_(4)emissions were analyzed using greenhouse gas data reported by both Annex I and non-Annex I countries under the United Nations Framework Convention on Climate Change(UNFCC...The trends and characteristics of global CH_(4)emissions were analyzed using greenhouse gas data reported by both Annex I and non-Annex I countries under the United Nations Framework Convention on Climate Change(UNFCCC)from 1990 to 2021.The results show the following:(1)In 2021,the cumulative CH_(4)emissions from the 42 nations listed in Annex I of the UNFCCC amounted to 1871521.79 kt CO_(2)eq.The top 10 countries account for 82.0%of the total CH_(4)emissions.(2)Most Annex I countries showed a gradual decline in CH_(4)emissions over the period.In contrast,emissions from non-Annex I countries have increased year by year.Notably,CH_(4)emissions in the United States,the European Union,the Russian Federation,and Ukraine decreased by 14.0%,37.4%,24.0%,and 60.9%,respectively.(3)In 2020,the CH_(4)emissions of the agriculture,energy,waste treatment and LULUCF(land use,land-use change and forestry)sectors in Annex I countries were 72240.43,63863.51,41573.08,and 889019 million tons of CO_(2)eq,accounting for 38.6%,34.1%,22.2%,and 4.8%,respectively.Among non-Annex I countries,the main CH_(4)sources vary by country.In China and Mexico,energy and agriculture were the largest contributors,accounting for 44.8%and 40.2%in China,and 34.4%and 43.3%in Mexico,respectively.In India,Brazil,Nigeria,Argentina,and Vietnam,agriculture dominated,contributing 73.8%,75.8%,59.7%,60.3%,and 58.5%of total emissions,respectively.Indonesia was an exception,with waste treatment being the primary source,accounting for 64.8%of its total CH_(4)emissions.展开更多
The variability of the sea surface salinity measurements provided by the Soil Moisture and Ocean Salinity mission reveals the presence of a local salinity maximum(a salty tongue)in the northwestern tropical Atlantic.T...The variability of the sea surface salinity measurements provided by the Soil Moisture and Ocean Salinity mission reveals the presence of a local salinity maximum(a salty tongue)in the northwestern tropical Atlantic.The sea surface salinity positive anomaly starts increasing in July,reaches its maximum in January,and then disappears.The local maximum of salinity appears in the late boreal autumn/winter,when the Amazon discharge is minimal and the salty water from the South Atlantic is transported by the North Brazil Current along the shelf break across the equator.The authors validate the satellite observations in this area and assess the vertical structure of the salinity maximum by using in situ measurements and an in situ-interpolated product.展开更多
This article analyses the relationship between PM_(10) concentrations inside and outside two schools in Barreiro,Portugal:Primary School No.5 and D.Luís Mendonça Furtado Basic School.The main objective was t...This article analyses the relationship between PM_(10) concentrations inside and outside two schools in Barreiro,Portugal:Primary School No.5 and D.Luís Mendonça Furtado Basic School.The main objective was to understand the impact of external and internal sources on indoor air quality(IAQ)in school environments.Monitoring campaigns were carried out in different indoor spaces,including classrooms,the gym,and the canteen,and the results were compared with PM_(10) levels outside the building.At Primary School No.5,indoor PM10 concentrations were consistently higher than the outdoor values measured on Avenida do Bocage,with an average Indoor/Outdoor(I/O)ratio of 2.2,indicating a significant impact of indoor activities on particle levels.Similarly,at the D.Luís Mendonça Furtado Basic School,there was an increase in PM_(10) and PM_(2:5) concentrations during school hours,with the highest I/O ratio(3.04)recorded on school days.In the evenings and at weekends,when the spaces were unoccupied,particle concentrations dropped considerably,reaching an I/O ratio of 0.70.Said results suggest that indoor activities are a determining factor for particle levels in indoor air,emphasizing the need for ventilation and pollution control strategies in schools to protect the health of students and staff.展开更多
Recent studies suggest per-and polyfluoroalkyl substances(PFAS)are ubiquitous in rivers worldwide.In the Asia-Pacific region,the frequency of PFAS detection in rivers is increasing.However,the overwhelming majority of...Recent studies suggest per-and polyfluoroalkyl substances(PFAS)are ubiquitous in rivers worldwide.In the Asia-Pacific region,the frequency of PFAS detection in rivers is increasing.However,the overwhelming majority of studies and data represent high population and urbanized river catchments.In this study,we investigate PFAS occurrence in major Philippines river systems characterized by both high and low population densities.In the Pasig Laguna de Bay River,which drains a major urban conurbation,we detected PFAS at concentrations typical of global rivers.Unexpectedly,we did not detect PFAS in river water or sediments in low population density river catchments,despite our instrument detection limits being lower than the vast majority of river concentrations reported worldwide.We hypothesize that septic tanks,as the dominant wastewater treatment practice in Philippines catchments,may control the release of PFAS into groundwater and rivers in the Philippines.However,no groundwater PFAS data currently exist to validate this supposition.More broadly,our findings highlight the need for more representative PFAS sampling and analysis in rivers to more accurately represent regional and global detection frequencies and trends.展开更多
A methodology for identifying volatile organic compounds （VOCs） and determining air quality of indoor air has been developed. The air samples are collected using pump samplers by the inhabitants when they perceive o...A methodology for identifying volatile organic compounds （VOCs） and determining air quality of indoor air has been developed. The air samples are collected using pump samplers by the inhabitants when they perceive odorous and/or discomfort episodes. Glass multi-sorbent tubes are connected to the pump samplers for the retention of VOC. The analysis is performed by automatic thermal desorption （ATD） coupled with gas chromatography-mass spectrometry （GC/MS）. This methodology can be applied in cases of sick building syndrome （SBS） evaluation, in which building occupants experience a series of varied symptoms that appear to be linked to time spent in the building. Chemical pollutants concentrations （e.g., VOC） have been described to contribute to SBS. To exemplify the methodology, a qualitative determination and an evaluation of existing VOC were performed in a dwelling where the occupants experienced the SBS symptoms. Higher total VOC （TVOC） levels were detected during episodes in indoor air （1.33 ±1.53 mg/m^3） compared to outdoor air （0.71± 0.46 mg/m^3）. The concentrations of individual VOCs, such as ethanol, acetone, isopropanol, 1-butanol, acetic acid, acetonitrile and 1-methoxy-2-propanol, were also higher than the expected for a standard dwelling. The external source of VOC was found to be an undeclared activity of storage and manipulation of solvents located at the bottom of a contiguous building.展开更多
Groundwater residence time is a fundamental property of groundwater to understand important hydrogeological issues,such as deriving sustainable abstraction volumes,or,the evolution of groundwater quality.The anthropog...Groundwater residence time is a fundamental property of groundwater to understand important hydrogeological issues,such as deriving sustainable abstraction volumes,or,the evolution of groundwater quality.The anthropogenic trace gases chlorofluorocarbons (CFC-11,CFC-12 and CFC-113) and sulphur hexafluoride (SF6) are ideal in this regard because they have been released globally at known rates and become dissolved in groundwater following Henry’s Law,integrating over large spatial (global) and temporal (decades) scales.The CFCs and SF6 are able to date groundwater up to w100 years old with the caveat of certain simplifying assumptions.However,the inversion of environmental tracer concentrations (CFCs and SF6) to derive groundwater age rests on the accurate determination of groundwater recharge parameters,namely temperature,elevation,salinity and excess air,in addition to resolving the potential for contamination,degradation and unsaturated zone effects.This review explores the fundamentals of CFC-11,CFC-12,CFC-113 and SF6 as environmental tracers of groundwater age and recommends complementary techniques throughout.Once this relatively simple and inexpensive technique has been used to determine initial concentrations at the recharge zone,setting the groundwater dating ‘clock’ to zero,this review then explores the meaning of groundwater ‘age’ in relation to measured environmental tracer concentrations.It is shown that the CFCs and SF6 may be applied to a wide-range of hydrogeological problems and suggests that environmental tracers are particularly powerful tools when integrated with numerical flow and transport models.展开更多
This work investigated the influence of Sn and Mo on corrosion behavior of ferrite-pearlite steel in the simulated bottom plate environment of cargo oil tank. The results indicate that the corrosion rate of three ferr...This work investigated the influence of Sn and Mo on corrosion behavior of ferrite-pearlite steel in the simulated bottom plate environment of cargo oil tank. The results indicate that the corrosion rate of three ferrite-pearlite steels increased with extending the immersion time due to the continuous accumulation of the residual Fe3C. However, the addition of Sn or the combined addition of Sn and Mo could reduce the corrosion rate of Sn containing steel and Sn-Mo containing steel to 37.5% and 20% of that of carbon steel, respectively. Moreover, the cathodic reaction of Sn containing steel and Sn-Mo containing steel was always controlled by the charge transfer step during the whole immersion test, while that of carbon steel was gradually transformed into the diffusion-controlled process. These results were mainly related with the deposition of metallic Sn and Mo on the steel surface. The metallic Sn and Mo with uniform distribution restrained the galvanic effect through suppressing both the anodic dissolution of ferrite and cathodic hydrogen evolution reaction on the residual Fe3C.展开更多
基金supported by the National Key Research and Development Program of China(2021YFD1700900)the National Natural Science Foundation of China(31972519)+1 种基金the Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences(2060302-05-956-1)the Project for the Government’s Purchase Service,China(13210186)。
文摘Globally,sub-optimal use of nitrogen (N) fertiliser and elevated N irrigation groundwater have led to high leached nitrate (NO_(3)^(–)) losses from protected vegetable field systems.Optimising fertiliser and irrigation management in different soil types is crucial to reduce future N loads from such systems.The present 4-year study examined leached N loads from lysimeter monitoring arrays set up across 18 protected vegetable system sites encompassing the dominant soil types of northern China.The treatments applied at each field site were:1) a high N and high irrigation input treatment (HNHI);2) a low N but high irrigation input treatment (LNHI) and 3) a low N with low irrigation input treatment (LNLI).Results showed that the mean annual leached total nitrogen loads from the HNHI,LNHI and LNLI treatments were 325,294 and 257 kg N ha^(–1) in the fluvo-aquic soil,114,100 and 78 kg N ha^(–1) in the cinnamon soil and 79,68 and 57 kg N ha^(–1) in the black soil,respectively.The N dissolved in irrigation water in the fluvo-aquic soil areas was 8.26-fold higher than in the cinnamon areas.A structural equation model showed that N fertiliser inputs and leaching water amounts explained 14.7 and 81.8%of the variation of leached N loads,respectively.Correspondingly,reducing irrigation water by 21.5%decreased leached N loads by 20.9%,while reducing manure N and chemical N inputs by 22 and 25%decreased leached N loads by only 9.5%. This study highlights that protected vegetable fields dominated by fluvo-aquic soil need management to curtail leached N losses in northern China.
基金support from the National Key Scientific and Technological Infrastructure project “Earth System Science Numerical Simulator Facility” (Earth Lab)sponsored by the National Natural Science Foundation of China (Grant Nos. 42175132, 92044303, and 42205119)+2 种基金the National Key R&D Program (Grant Nos. 2020YFA0607802 and 2022YFC3703003)the CAS Information Technology Program (Grant No. CAS-WX2021SF-0107-02)the fellowship of China Postdoctoral Science Foundation (Grant No. 2022M723093)
文摘Scientific knowledge on the chemical compositions of fine particulate matter(PM_(2.5)) is essential for properly assessing its health and climate effects,and for decisionmakers to develop efficient mitigation strategies.A high-resolution PM_(2.5) chemical composition dataset(CAQRA-aerosol)is developed in this study,which provides hourly maps of organic carbon,black carbon,ammonium,nitrate,and sulfate in China from 2013 to 2020 with a horizontal resolution of 15 km.This paper describes the method,access,and validation results of this dataset.It shows that CAQRA-aerosol has good consistency with observations and achieves higher or comparable accuracy with previous PM_(2.5) composition datasets.Based on CAQRA-aerosol,spatiotemporal changes of different PM_(2.5) compositions were investigated from a national viewpoint,which emphasizes different changes of nitrate from other compositions.The estimated annual rate of population-weighted concentrations of nitrate is 0.23μg m^(−3)yr^(−1) from 2015 to 2020,compared with−0.19 to−1.1μg m^(−3)yr^(−1) for other compositions.The whole dataset is freely available from the China Air Pollution Data Center(https://doi.org/10.12423/capdb_PKU.2023.DA).
基金supported by the National Natural Science Foundation of China(Nos.21976045 and 22076112)China Scholarship Council(CSC)Scholarship(Nos.202208610125 and 202308610123)+1 种基金Shaanxi Key Laboratory of Environmental Monitoring and Forewarning of Trace Pollutants(No.SHJKFJJ202318)the Key Research and Development Program of Shaanxi Province(No.2024SF-YBXM-567).
文摘Acid-base dissociable antibiotic-metal complexes are known to be emerging contaminants in the aquatic environments.However,little information is available on the photochemical properties and toxicity of these complex forms.This study investigated the spectral properties of three fluoroquinolones(FQs)with and without metal ions Fe(III),Cu(II),and Al(III)in solutions under different pH conditions,as well as evaluated the changes in toxicity due to the complex with thesemetal ions using luminescent bacteria(vibrio fischeri).FQs showed a higher tendency to coordinate metal ions under alkaline conditions compared to neutral and acidic conditions,and the formation of complexes weakened the ultravioletabsorbing ability of FQs.At pH=7.0,Cu(II)quenched the fluorescence intensity of FQs.Moreover,their Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy were explored,revealing that the coordination sites of Cu(II)in three FQs were situated in a bidentate manner through the oxygen atom of the deprotonated carboxyl group and cyclic carbonyl oxygen atom.This conclusion was further verified by the theory of molecular surface electrostatic potential.In addition,except for complexes of ciprofloxacin-metals,enhanced toxicity of FQs upon coordination with Fe(III)was observed,while reduced toxicity was found for coordination with Cu(II)and Al(III).These results are important for accurately evaluating the photochemical behavior and risk of these antibiotics in aquatic environments contaminated with metal ions.
基金supported by the National Key Research and Development Program of China(2022YFD1400600)the National Natural Science Foundation of China(32172397,32472540,31871951 and 31672019)+1 种基金the China Agriculture Research System of MOF and MARA(CARS-22)the Natural Science Foundation of Beijing,China(6172030)。
文摘Migratory insect pests tend to suddenly immigrate into new habitats over a short period to simultaneously lay eggs in clusters,resulting in gregarious larvae that cause severe damage to crops.These aggregated larvae can adapt well to various natural enemies and pathogens in their new habitats,but how their resistance might be enhanced and its immunological significance remain unknown.Here,we examined how infection by a pathogen and a parasitic fly affect the immune response and migratory behavior in two phases of the oriental armyworm,Mythimna separata,which differ dramatically in their flight capacity and fecundity.The gregarious larvae displayed greater resistance than solitary larvae to the challenges of both the entomopathogenic fungus Metarhizium anisopliae and the parasitoid Exorista civilis.In response to a challenge by M.anisopliae,gregarious larvae exhibited more pronounced increases in phenoloxidase(PO)activity and lysozyme activity than solitary larvae.Furthermore,in addition to the greater PO and lysozyme activities,the levels of dopamine and 5-hydroxytryptamine(5-HT)were also greater in challenged gregarious and solitary larvae.Injection of dopamine(or 5-HT)significantly enhanced PO activity,lysozyme activity,antibacterial activity and larval survival.Subsequently,there was a significant increase in the flight capacity of adults derived from gregarious larvae challenged by M.anisopliae;while no significant variation was observed in the adults from challenged solitary larvae.The preoviposition period,oviposition period and fecundity were not significantly affected by M.anisopliae,regardless of whether the larvae were gregarious or solitary.These results provide new insights into the relationship between migration and immunity in insects,and their behavior after immunization.
基金financial and logistic support(for fieldwork campaigns,GPS tracking devices and laboratory analysis)from the project LIFE Ilhas Barreira project(LIFE18 NAT/PT/000927)funding provided by Foundation for Science and Technology,I.P.(FCT)to MARE(UIDB/MAR/04292/2020,https://doi.org/10.54499/UIDB/04292/2020 and UIDP/04292/2020,https://doi.org/10.54499/UIDP/04292/2020+1 种基金the Associate Laboratory ARNET(LA/P/0069/2020,https://doi.org/10.54499/LA/P/0069/2020)supported by FCT doctoral fellowships(10.54499/2020.07495.BD,SFRH/BD/145827/2019)。
文摘Little Terns Sternula albifrons are estuarine birds extensively using increasingly urbanized coastal areas.Given the increased exposure of these ecosystems to anthropogenic activities,it is crucial to study the ecology of this species and interactions with human stressors to establish management measures.We collected regurgitates(n=182)and blood samples(n=48)to study Little Terns’diet,health condition and isotopic niche,and individually tracked breeding adults(n=9,during 2021 and 2022)at 2 sandy beaches 21 km apart and located within Ria Formosa Natural Park,Algarve,Portugal.Although both areas are adjacent to foraging coastal marine areas and an estuarine lagoon system with saltpans,they differ in human disturbance.We also compared breeding success and adult health measures between these 2 colonies.The main prey for both populations were Sand Smelts Atherina spp.and Gobies Pomatoschistus spp.,and no differences in δ^(13)C and δ^(15)N stable isotopic values between colonies were found.Tracking data revealed that individuals foraged in the surroundings of their breeding colonies.Entrance Channels and Ocean were the most frequently used habitats for foraging by individuals from the less disturbed colony.Adults from the more disturbed colony foraged mostly in Entrance Channels.Overall,all individuals tended to forage during daytime.There were no differences in health measures of individuals between colonies,though breeding success at the most disturbed colony was comparably lower.It is important to protect both breeding areas and adjacent foraging habitats for Little Terns,particularly given the expected increasing pressure from human activities on coastal areas worldwide.
基金supported by the National Foundation for Science and Technology Development (NAFOSTED,106.05-2021.19)The CAS President’s International Fellowship Initiative (PIFI 2023VBC0022) supported C.V.HOANG as a Visiting Scientist in China+1 种基金Field surveys in Vietnam were partially supported by Project to Build National Forest Resources Museum Networkpartially supported by Ideal Wild and the Rufford Foundation (grant No.43835-1) to C.V.HOANG。
文摘Two new species of Leptobrachella are described from Vietnam based on morphological differences and genetic divergences in 16S rRNA mitochondrial gene sequences.The new taxa are distinguished from each other and from other species of the genus Leptobrachella in body size,head width/length ratio,tympanum morphology,dorsal skin texture,the presence/absence of fringes on toes,color of dorsal and ventral body,and iris color.The two new species are also divergent from each other and from other congeners by a 4.14% or greater uncorrected genetic distance.Leptobrachella batxatensis sp.nov.is genetically closest to L.shiwandashanensis and L.wuhuangmontis from China.Leptobrachella duyenae sp.nov.is genetically closest to L.bidoupensis from Vietnam with strong nodal support from both BI and ML analyses(1.0/99%).
基金supported by the National Natural Science Foundation of China(Nos.42488101,42141021,42172149,42172168,U2244209)the Tencent Foundation through the XPLORER PRIZE。
文摘Occurrence and abundance of molecular hydrogen in natural geologic reservoirs are enigmatic,due to its various sources,diverse migration pathways and complicated biological and chemical reactions.Natural gas samples containing hydrogen from producing wells in several sedimentary basins in China were collected in this study,and gas abundances and isotopic compositions of these gases were compared with those in global petroliferous basins and deep intrusive rocks.Several geochemical indicators were suggested for identifying sources,migration and accumulation mechanisms of hydrogen in the subsurface environment.Hydrogen contents in natural gas deposits have contributions from various sources with the following high-to-low order:microbial degradation>serpentinization>deep mantle volatile release>radiation-induced water decomposition>thermal cracking of organic matter.A hydrogen-rich reservoir in Kansas,USA,is specifically analyzed to determine its formation mechanism.This study suggests that future exploration of geological hydrogen resources may focus on the igneous rock bodies with overlying dense sedimentary rocks in the continental rift systems.
基金supported by the Key Research and Development Program of Shaanxi Province(No.2024SF-YBXM-567)the National Natural Science Foundation of China(Nos.21976045,22076112)the China Scholarship Council(CSC)Scholarship(No.202308610123).
文摘As antibiotic pollutants cannot be incompletely removed by conventional wastewater treatment plants,ultraviolet(UV)based advanced oxidation processes(AOPs)such as UV/persulfate(UV/PS)and UV/chlorine are increasingly concerned for the effective removal of antibiotics from wastewaters.However,the specific mechanisms involving degradation kinetics and transformation mechanisms are not well elucidated.Here we report a detailed examination of SO_(4)•−/Cl•-mediated degradation kinetics,products,and toxicities of sulfathiazole(ST),sarafloxacin(SAR),and lomefloxacin(LOM)in the two processes.Both SO_(4)•−/Cl•-mediated transformation kinetics were found to be dependent on pH(P<0.05),which was attributed to the disparate reactivities of their individual dissociated forms.Based on competition kinetic experiments and matrix calculations,the cationic forms(H_(2)ST^(+),H_(2)SAR^(+),and H_(2)LOM^(+))were more highly reactive towards SO_(4)•−in most cases,while the neutral forms(e.g.,HSAR^(0)and HLOM^(0))reacted the fastest with Cl•for the most of the antibiotics tested.Based on the identification of 31 key intermediates using tandem mass spectrometry,these reactions generated different products,of which the majority still retained the core chemical structure of the parent compounds.The corresponding diverse transformation pathways were proposed,involving S−N breaking,hydroxylation,defluorination,and chlorination reactions.Furthermore,the toxicity changes of their reaction solutions as well as the toxicity of each intermediate were evaluated by the vibrio fischeri and ECOSAR model,respectively.Many primary by-products were proven to be more toxic than the parent chemicals,raising the wider issue of extended potency for these compounds with regards to their ecotoxicity.These results have implications for assessing the degradative fate and risk of these chemicals during the AOPs.
基金supported by the National Natural Science Foundation of China(Nos.52173304 and U1867216)the National Key R&D Program of China(No.2022YFB3207600)China Scholarship Council(No.2018SLJ014508).
文摘Buffer material and metal disposal containers are the key engineering barriers in the geological disposal of high-level radioactive waste.The durability of disposal containers largely depends on the water con-tent in buffer material.This work focused on investigating the corrosion evolution of NiCu low alloy steel in compacted GMZ bentonite with different water contents for 270 d by using weight loss,electrochemi-cal measurements,and various methods for analyzing corrosion products.As the water content increased from 13%to 20%,the water in the bentonite transformed from an unsaturated to a critical saturated state,and the corrosion rate of NiCu steel clearly increased.In these two systems,the oxygen could mi-grate to the thin liquid film on the steel surface through the air pores in the bentonite in the gas phase and undergo cathodic reduction.Meanwhile,it oxidized the ferrous hydrolysis products into ferric corro-sion products and formed a rust layer,which could block the diffusion of oxygen.At that moment,the cathodic process of NiCu steel corrosion changed to rust reduction.When the water content continually increased to 30%and 40%,the compacted bentonite was in a saturation state,and the corrosion rate of NiCu steel was significantly decreased.This was because most pores among the bentonite particles were occupied by a large amount of free water,which hindered the diffusion of oxygen and inhibited its cathodic reduction.Furthermore,it restrained the oxidation of ferrous corrosion products,which greatly weakened the cathodic depolarization of rust,leading to the cathodic process being dominated by the hydrogen evolution reaction.
基金supported by the National Natural Science Foundation of China(Grant Nos.41877267,41877260)the Priority Research Program of the Chinese Academy of Science(Grant No.XDA13010201).
文摘Catastrophic failure in engineering structures of island reefs would occur when the tertiary creep initiates in coral reef limestone with a transition from short-to long-term load.Due to the complexity of biological structures,the underlying micro-behaviors involving time-dependent deformation are poorly understood.For this,an abnormal phenomenon was observed where the axial and lateral creep deformations were mutually independent by a series of triaxial tests under constant stress and strain rate conditions.The significantly large lateral creep deformation implies that the creep process cannot be described in continuum mechanics regime.Herein,it is hypothesized that sliding mechanism of crystal cleavages dominates the lateral creep deformation in coral reef limestone.Then,approaches of polarizing microscope(PM)and scanning electronic microscope(SEM)are utilized to validate the hypothesis.It shows that the sliding behavior of crystal cleavages combats with conventional creep micro-mechanisms at certain condition.The former is sensitive to time and strain rate,and is merely activated in the creep regime.
基金National Key Research and Development Program of China(No.2022YFC3204404,2023YFF1303705)National Natural Science Foundation of China(No.U2243206)。
文摘The Yangtze River economic belt(YREB),China is important to the Chinese economy and for supporting sustainable development.Clarifying the relationship between water quality indices and socioeconomic indicators could help improve aquatic environment management in the YREB and our understanding of the causes and effects of water quality variations in other large river basins.In this study,river water quality,factors affecting water quality,and management strategies,and correlations between water quality indices and socioeconomic indicators in the YREB during the 13th Five-Year Plan period(2016-2020)were assessed.The single-factor evaluation method,constant price for GDP,and correlation analyses were adopted.The results showed that:1)water quality in the YREB improved during the 13th Five-Year Plan period.The number of aquatic environment sections meeting GradeⅠ-Ⅲwater quality standards increased by 13.1%and the number below Grade V decreased by 2.9%.2)The values of 12 indicators in the YREB exceeded relevant standards.The indicators with highest concentreation were the total phosphorus,chemical oxygen demand,ammonia nitrogen,and permanganate index,which were relatively high in downstream regions in Anhui Province,Jiangsu Province,and Shanghai Municipality.3)Ammonia nitrogen,chemical oxygen demand,and total phosphorus emissions per unit area and water extraction per unit area are relatively high in the three downstream regions mentioned above.4)Increased domestic sewage discharges have increased total wastewater discharges in the YREB.5)River water quality in the YREB strongly correlated with population,economic,and water resource indices and less strongly correlated with government investment,agriculture,meteorology,energy,and forestry indices.This confirmed the need to decrease wastewater discharges and non-point-source pollutant emissions.The aquatic environment could be improved by taking reasonable measures to control population growth,adjusting the industrial structure to accelerate industrial transformation and increase the proportion of tertiary industries,and investing in technological innovations to protect the environment.
基金supported by the National Key Research and Development Project of China(Nos.2022YFC3703502 and 2018YFC0213201)the National Natural Science Foundation of China(No.42105133)the Local Service Project of Hefei(No.2020BFFFD01804).
文摘Studying the spatiotemporal distribution and transboundary transport of aerosols,NO_(2),SO_(2),and HCHO in typical regions is crucial for understanding regional pollution causes.In a 2-year study using multi-axis differential optical absorption spectroscopy in Qingdao,Shanghai,Xi’an,and Kunming,we investigated pollutant distribution and transport across Eastern China-Ocean,Tibetan Plateau-Central and Eastern China,and China-Southeast Asia interfaces.First,pollutant distributionwas analyzed.Kunming,frequently clouded and misty,exhibited consistently high aerosol optical depth throughout the year.In Qingdao and Shanghai,NO_(2)and SO_(2),as well as SO_(2)in Xi’an,increased in winter.Elevated HCHO in summer in Shanghai and Xi’an,especially Xi’an,suggests potential ozone pollution issues.Subsequently,pollutant transportation across interfaces was studied.At the Eastern China-Ocean interface,the gas transport flux was the largest among other interfaces,with the outflux exceeding the influx,especially in winter and spring.The input of pollutants from the Tibetan Plateau to central-eastern Chinawas larger than the output in winter and spring,with SO_(2)having the highest transport flux in winter.The pollution input from Southeast Asia to China significantly exceeded the output,with spring and winter inputs being 3.22 and 3.03 times the output,respectively.Lastly,the transportation characteristics of a pollution event at Kunming were studied.During this period,pollutants were transported from west to east,with themaximum SO_(2)transport flux at an altitude of 2.87 km equaling 27.74μg/(m^(2)·s).It is speculated that this pollution was caused by the transport from Southeast Asian countries to Kunming.
基金supported by the National Key Research and Development Program of China[grant number 2022YFC3703003]the Energy Foundation Project[grant number G-2309-35044]the SinoNorwegian Project on Methane from Livestock Production and Waste Management(ChiNorCH4)[grant number CHN-2148,22/0011].
文摘The trends and characteristics of global CH_(4)emissions were analyzed using greenhouse gas data reported by both Annex I and non-Annex I countries under the United Nations Framework Convention on Climate Change(UNFCCC)from 1990 to 2021.The results show the following:(1)In 2021,the cumulative CH_(4)emissions from the 42 nations listed in Annex I of the UNFCCC amounted to 1871521.79 kt CO_(2)eq.The top 10 countries account for 82.0%of the total CH_(4)emissions.(2)Most Annex I countries showed a gradual decline in CH_(4)emissions over the period.In contrast,emissions from non-Annex I countries have increased year by year.Notably,CH_(4)emissions in the United States,the European Union,the Russian Federation,and Ukraine decreased by 14.0%,37.4%,24.0%,and 60.9%,respectively.(3)In 2020,the CH_(4)emissions of the agriculture,energy,waste treatment and LULUCF(land use,land-use change and forestry)sectors in Annex I countries were 72240.43,63863.51,41573.08,and 889019 million tons of CO_(2)eq,accounting for 38.6%,34.1%,22.2%,and 4.8%,respectively.Among non-Annex I countries,the main CH_(4)sources vary by country.In China and Mexico,energy and agriculture were the largest contributors,accounting for 44.8%and 40.2%in China,and 34.4%and 43.3%in Mexico,respectively.In India,Brazil,Nigeria,Argentina,and Vietnam,agriculture dominated,contributing 73.8%,75.8%,59.7%,60.3%,and 58.5%of total emissions,respectively.Indonesia was an exception,with waste treatment being the primary source,accounting for 64.8%of its total CH_(4)emissions.
基金financed by the Funda?ao para a Ciencia e a Tecnologia(FCT)through the project UIDP/04292/2020(https://doi.org/10.54499/UIDP/04292/2020)UIDB/04292/2020(https://doi.org/10.54499/UIDB/04292/2020)+2 种基金awarded to MARE and through project LA/P/0069/2020(https://doi.org/10.54499/LA/P/0069/2020)granted to the Associate Laboratory ARNETfunded by the European Space Agency through the SMOS Expert Support Laboratory(ESL)for SMOS Level 2 over land,ocean,ice[4000130567/20/I-BG]MCIN/AEI/10.13039/501,100,011,033 through the project INTERACT[PID2020-114623RB-C31]。
文摘The variability of the sea surface salinity measurements provided by the Soil Moisture and Ocean Salinity mission reveals the presence of a local salinity maximum(a salty tongue)in the northwestern tropical Atlantic.The sea surface salinity positive anomaly starts increasing in July,reaches its maximum in January,and then disappears.The local maximum of salinity appears in the late boreal autumn/winter,when the Amazon discharge is minimal and the salty water from the South Atlantic is transported by the North Brazil Current along the shelf break across the equator.The authors validate the satellite observations in this area and assess the vertical structure of the salinity maximum by using in situ measurements and an in situ-interpolated product.
文摘This article analyses the relationship between PM_(10) concentrations inside and outside two schools in Barreiro,Portugal:Primary School No.5 and D.Luís Mendonça Furtado Basic School.The main objective was to understand the impact of external and internal sources on indoor air quality(IAQ)in school environments.Monitoring campaigns were carried out in different indoor spaces,including classrooms,the gym,and the canteen,and the results were compared with PM_(10) levels outside the building.At Primary School No.5,indoor PM10 concentrations were consistently higher than the outdoor values measured on Avenida do Bocage,with an average Indoor/Outdoor(I/O)ratio of 2.2,indicating a significant impact of indoor activities on particle levels.Similarly,at the D.Luís Mendonça Furtado Basic School,there was an increase in PM_(10) and PM_(2:5) concentrations during school hours,with the highest I/O ratio(3.04)recorded on school days.In the evenings and at weekends,when the spaces were unoccupied,particle concentrations dropped considerably,reaching an I/O ratio of 0.70.Said results suggest that indoor activities are a determining factor for particle levels in indoor air,emphasizing the need for ventilation and pollution control strategies in schools to protect the health of students and staff.
基金Natural Environment Research Council,Grant/Award Number:NE/W006871/1。
文摘Recent studies suggest per-and polyfluoroalkyl substances(PFAS)are ubiquitous in rivers worldwide.In the Asia-Pacific region,the frequency of PFAS detection in rivers is increasing.However,the overwhelming majority of studies and data represent high population and urbanized river catchments.In this study,we investigate PFAS occurrence in major Philippines river systems characterized by both high and low population densities.In the Pasig Laguna de Bay River,which drains a major urban conurbation,we detected PFAS at concentrations typical of global rivers.Unexpectedly,we did not detect PFAS in river water or sediments in low population density river catchments,despite our instrument detection limits being lower than the vast majority of river concentrations reported worldwide.We hypothesize that septic tanks,as the dominant wastewater treatment practice in Philippines catchments,may control the release of PFAS into groundwater and rivers in the Philippines.However,no groundwater PFAS data currently exist to validate this supposition.More broadly,our findings highlight the need for more representative PFAS sampling and analysis in rivers to more accurately represent regional and global detection frequencies and trends.
文摘A methodology for identifying volatile organic compounds （VOCs） and determining air quality of indoor air has been developed. The air samples are collected using pump samplers by the inhabitants when they perceive odorous and/or discomfort episodes. Glass multi-sorbent tubes are connected to the pump samplers for the retention of VOC. The analysis is performed by automatic thermal desorption （ATD） coupled with gas chromatography-mass spectrometry （GC/MS）. This methodology can be applied in cases of sick building syndrome （SBS） evaluation, in which building occupants experience a series of varied symptoms that appear to be linked to time spent in the building. Chemical pollutants concentrations （e.g., VOC） have been described to contribute to SBS. To exemplify the methodology, a qualitative determination and an evaluation of existing VOC were performed in a dwelling where the occupants experienced the SBS symptoms. Higher total VOC （TVOC） levels were detected during episodes in indoor air （1.33 ±1.53 mg/m^3） compared to outdoor air （0.71± 0.46 mg/m^3）. The concentrations of individual VOCs, such as ethanol, acetone, isopropanol, 1-butanol, acetic acid, acetonitrile and 1-methoxy-2-propanol, were also higher than the expected for a standard dwelling. The external source of VOC was found to be an undeclared activity of storage and manipulation of solvents located at the bottom of a contiguous building.
基金supported by a Natural Environment Research Council(NERC) Collaborative Awards in Science and Engineering (CASE) studentship(NE/EEA6549/1)
文摘Groundwater residence time is a fundamental property of groundwater to understand important hydrogeological issues,such as deriving sustainable abstraction volumes,or,the evolution of groundwater quality.The anthropogenic trace gases chlorofluorocarbons (CFC-11,CFC-12 and CFC-113) and sulphur hexafluoride (SF6) are ideal in this regard because they have been released globally at known rates and become dissolved in groundwater following Henry’s Law,integrating over large spatial (global) and temporal (decades) scales.The CFCs and SF6 are able to date groundwater up to w100 years old with the caveat of certain simplifying assumptions.However,the inversion of environmental tracer concentrations (CFCs and SF6) to derive groundwater age rests on the accurate determination of groundwater recharge parameters,namely temperature,elevation,salinity and excess air,in addition to resolving the potential for contamination,degradation and unsaturated zone effects.This review explores the fundamentals of CFC-11,CFC-12,CFC-113 and SF6 as environmental tracers of groundwater age and recommends complementary techniques throughout.Once this relatively simple and inexpensive technique has been used to determine initial concentrations at the recharge zone,setting the groundwater dating ‘clock’ to zero,this review then explores the meaning of groundwater ‘age’ in relation to measured environmental tracer concentrations.It is shown that the CFCs and SF6 may be applied to a wide-range of hydrogeological problems and suggests that environmental tracers are particularly powerful tools when integrated with numerical flow and transport models.
基金financial support by the National Key Research and Development Program of China (No. 2017YFB0702302)National Natural Science Foundation of China (Nos. 51671200, 51501201 and 51501204)
文摘This work investigated the influence of Sn and Mo on corrosion behavior of ferrite-pearlite steel in the simulated bottom plate environment of cargo oil tank. The results indicate that the corrosion rate of three ferrite-pearlite steels increased with extending the immersion time due to the continuous accumulation of the residual Fe3C. However, the addition of Sn or the combined addition of Sn and Mo could reduce the corrosion rate of Sn containing steel and Sn-Mo containing steel to 37.5% and 20% of that of carbon steel, respectively. Moreover, the cathodic reaction of Sn containing steel and Sn-Mo containing steel was always controlled by the charge transfer step during the whole immersion test, while that of carbon steel was gradually transformed into the diffusion-controlled process. These results were mainly related with the deposition of metallic Sn and Mo on the steel surface. The metallic Sn and Mo with uniform distribution restrained the galvanic effect through suppressing both the anodic dissolution of ferrite and cathodic hydrogen evolution reaction on the residual Fe3C.
