In this study, we investigate the spatiotemporal characteristics of drought in India and its impact on agriculture during the summer season （April-September）. In the analysis, we use Standardized Precipitation Evapo...In this study, we investigate the spatiotemporal characteristics of drought in India and its impact on agriculture during the summer season （April-September）. In the analysis, we use Standardized Precipitation Evapotranspiration Index （SPEI） datasets between 1982 and 2012 at the six-monthly timescale. Based on the criterion SPEI 〈 -1, we obtain a map of the number of occurrences of drought and find that the humid subtropical Upper Middle Gangetic Plain （UMGP） region is highly drought-prone, with an occurrence frequency of 40%-45%. This UMGP region contributes at least 18%-20% of India＇s annual cereal production. Not only the probability of drought, but the UMGP region has become increasingly drought-prone in recent decades. Moreover, cereal production in the UMGP region has experienced a gradual declining trend from 2000 onwards, which is consistent with the increase in drought-affected areas from 20%-25% to 50%-60%, before and after 2000, respectively. A higher correlation coefficient （-0.69） between the cereal production changes and drought-affected areas confirms that at least 50% of the agricultural （cereal） losses are associated with drought. While analyzing the individual impact of precipitation and surface temperature on SPEI at 6 month timescale [SPEI （6）] we find that, in the UMGP region, surface temperature plays the primary role in the lowering of the SPEI. The linkage is further confirmed by correlation analysis between SPEI （6） and surface temperature, which exhibits strong negative values in the UMGP region. Higher temperatures may have caused more evaporation and drying, which therefore increased the area affected by drought in recent decades.展开更多
Aeolian loess deposits contain abundant information about the evolution of the paleoenvironment.For example,paleoclimate changes recorded in Chinese loess area obtained significant achievement in the past few decades....Aeolian loess deposits contain abundant information about the evolution of the paleoenvironment.For example,paleoclimate changes recorded in Chinese loess area obtained significant achievement in the past few decades.Compared to Chinese loess,research on Indian loess is lacking.Currently,most studies focus on the Kashmir area located in the southern Himalayas,and studies on other areas are rare.However,field observations demonstrate that the sediments around the New Delhi-Agra-Jaipur Plain are similar to Chinese loess-paleosol sequences.For example,the boundary between two strata is transitional and without horizontal bedding.Moreover,obvious pedogenic horizons developed among sediment sequences,probably indicating unrecognised aeolian deposits in the Indo-Gangetic Plain(IGP).To confirm this,pilot samples were obtained from the IGP and detailed indoor measurements conducted.The results indicate that the distribution patterns of particle size and rare earth elements(REE) of the pilot samples are similar to Chinese loess.Furthermore,the scanning electronic microscopy(SEM) images of pilot samples show obvious conchoidal fractures,dash-shaped concavities,and abundant small pits that usually form through mechanical impact.These are typical characteristics of aeolian particles.In addition,environmental and rock magnetic measurements indicate that the dominant magnetic minerals in the pilot samples are magnetite and maghemite,and that they likely contain small amounts of hematite.Furthermore,conventional magnetic parameters are comparable with Chinese loess.Based on this,aeolian loess deposits are widely distributed in the IGP,which may have promoted the development of Indian farming and contributed towards the prosperity of ancient Indian civilisation.This study also provides a new and valuable record for the research on paleoclimate changes in the study area in the future.展开更多
Lumbini is a world heritage site located in the southern plains region of Nepal, and is regarded as a potential site for evaluating transboundary air pollution due to its proximity to the border with India. In this st...Lumbini is a world heritage site located in the southern plains region of Nepal, and is regarded as a potential site for evaluating transboundary air pollution due to its proximity to the border with India. In this study, 82 aerosol samples were collected between April 2013 and July 2014 to investigate the levels of particulate-bound mercury(PBM) and the corresponding seasonality, sources, and influencing factors.The PBM concentration in total suspended particulate(TSP) matter ranged from 6.8 pg m^(-3) to351.7 pg m^(-3)(mean of 99.7 ± 92.6 pg m^(-3)), which exceeded the ranges reported for remote and rural sites worldwide. The Hg content(PBM/TSP) ranged from 68.2 ng g^(-1) to 1744.8 ng g^(-1)(mean of 446.9 ±312.7 ng g^(-1)), indicating anthropogenic enrichment. The PBM levels were higher in the dry season(i.e.,winter and the pre-monsoon period) than in the wet season(i.e., the monsoon period). In addition, the δ^(202) Hg signature indicated that waste/coal burning and traffic were the major sources of Hg in Lumbini during the pre-monsoon period. Meanwhile, precipitation occurring during photochemical processes in the atmosphere may have been responsible for the observed Δ^(199) Hg values in the aerosol samples obtained during the monsoon period. The PBM concentration was influenced mostly by the resuspension of polluted dust during dry periods and crop residue burning during the post-monsoon period. The estimated PBM deposition flux at Lumbini was 15.7 lg m^(-2) yr^(-1). This study provides a reference dataset of atmospheric PBM over a year, which can be useful for understanding the geochemical cycling of Hg in this region of limited data.展开更多
Precipitation represents an important phenomenon for carbon and nitrogen deposition.Here,the concentrations and fluxes of dissolved organic carbon(DOC)and total dissolved nitrogen(TDN)with their potential sources were...Precipitation represents an important phenomenon for carbon and nitrogen deposition.Here,the concentrations and fluxes of dissolved organic carbon(DOC)and total dissolved nitrogen(TDN)with their potential sources were analyzed in wet precipitation during summer monsoon from the Northern Indo-Gangetic Plain(IGP),important but neglected area.The volume-weighted mean(VWM)concentration of DOC and TDN were 687.04 and 1210.23μg/L,respectively.Similarly,the VWM concentration of major ions were in a sequence of NH_(4)^(+)>Ca^(2+)>SO_(4)^(2-)>Na^(+)>K^(+)>NO_(3)~->Cl~->Mg^(2+)>F~->NO_(2)~-,suggesting NH_(4)^(+)and Ca^(2+)from agricultural activities and crustal dust played a vital role in precipitation chemistry.Moreover,the wet deposition flux of DOC and TDN were 9.95 and 17.06 kg/(ha year),respectively.The wet deposition flux of inorganic nitrogen species such as NH_(4)^(+)-N and NO_(3)^(-)-N were 14.31 and 0.47 kg/(ha year),respectively,demonstrating the strong influence of emission sources and precipitation volume.Source attribution from different analysis suggested the influence of biomass burning on DOC and anthropogenic activities(agriculture,animal husbandry)on nitrogenous species.The air-mass back trajectory analysis indicated the influence of air masses originating from the Bay of Bengal,which possibly carried marine and anthropogenic pollutants along with the biomass burning emissions to the sampling site.This study bridges the data gap in the less studied part of the northern IGP region and provides new information for policy makers to deal with pollution control.展开更多
Ambient particulate matter (PM2.5 and PM10) concentrations were measured during two different seasons (summer and winter) at three different locations of Gurugram which is located in the Indo-Gangetic plain of India. ...Ambient particulate matter (PM2.5 and PM10) concentrations were measured during two different seasons (summer and winter) at three different locations of Gurugram which is located in the Indo-Gangetic plain of India. The ambient concentrations of both PM2.5 and PM10 were higher during winter season (PM2.5: 261 μg·m-3;PM10: 440 μg·m-3) when compared to summer period (PM2.5: 114 μg·m-3;PM10: 202 μg·m-3). Potential Source Contribution Function (PSCF) analysis suggests significant seasonal variation in potential contributing locations of ambient PM2.5 over the study area. The PSCF analysis suggests that cross country transport of PM2.5 from Pakistan and Afghanistan significantly attributed to higher concentrations of PM2.5 at the study locations;whereas, PM2.5 emitted from locations in the south-western direction of the study sites attributed to the ambient PM2.5 concentrations at the study site during summer seasons. Further study is required to measure percentage contribution from different sectors and locations to the ambient particulate concentrations at the study site to develop sector specific mitigation plan.展开更多
基金supported by the National Basic Research Development Program of China(Grant No.2015CB953602)National Science Foundation of China(Grant Nos.41271542 and 41661144006)a CAS-TWAS President’s Fellowship,2013
文摘In this study, we investigate the spatiotemporal characteristics of drought in India and its impact on agriculture during the summer season （April-September）. In the analysis, we use Standardized Precipitation Evapotranspiration Index （SPEI） datasets between 1982 and 2012 at the six-monthly timescale. Based on the criterion SPEI 〈 -1, we obtain a map of the number of occurrences of drought and find that the humid subtropical Upper Middle Gangetic Plain （UMGP） region is highly drought-prone, with an occurrence frequency of 40%-45%. This UMGP region contributes at least 18%-20% of India＇s annual cereal production. Not only the probability of drought, but the UMGP region has become increasingly drought-prone in recent decades. Moreover, cereal production in the UMGP region has experienced a gradual declining trend from 2000 onwards, which is consistent with the increase in drought-affected areas from 20%-25% to 50%-60%, before and after 2000, respectively. A higher correlation coefficient （-0.69） between the cereal production changes and drought-affected areas confirms that at least 50% of the agricultural （cereal） losses are associated with drought. While analyzing the individual impact of precipitation and surface temperature on SPEI at 6 month timescale [SPEI （6）] we find that, in the UMGP region, surface temperature plays the primary role in the lowering of the SPEI. The linkage is further confirmed by correlation analysis between SPEI （6） and surface temperature, which exhibits strong negative values in the UMGP region. Higher temperatures may have caused more evaporation and drying, which therefore increased the area affected by drought in recent decades.
基金supported by National Natural Science Foundation of China(Grant Nos.41210002,U1405231&41602185)
文摘Aeolian loess deposits contain abundant information about the evolution of the paleoenvironment.For example,paleoclimate changes recorded in Chinese loess area obtained significant achievement in the past few decades.Compared to Chinese loess,research on Indian loess is lacking.Currently,most studies focus on the Kashmir area located in the southern Himalayas,and studies on other areas are rare.However,field observations demonstrate that the sediments around the New Delhi-Agra-Jaipur Plain are similar to Chinese loess-paleosol sequences.For example,the boundary between two strata is transitional and without horizontal bedding.Moreover,obvious pedogenic horizons developed among sediment sequences,probably indicating unrecognised aeolian deposits in the Indo-Gangetic Plain(IGP).To confirm this,pilot samples were obtained from the IGP and detailed indoor measurements conducted.The results indicate that the distribution patterns of particle size and rare earth elements(REE) of the pilot samples are similar to Chinese loess.Furthermore,the scanning electronic microscopy(SEM) images of pilot samples show obvious conchoidal fractures,dash-shaped concavities,and abundant small pits that usually form through mechanical impact.These are typical characteristics of aeolian particles.In addition,environmental and rock magnetic measurements indicate that the dominant magnetic minerals in the pilot samples are magnetite and maghemite,and that they likely contain small amounts of hematite.Furthermore,conventional magnetic parameters are comparable with Chinese loess.Based on this,aeolian loess deposits are widely distributed in the IGP,which may have promoted the development of Indian farming and contributed towards the prosperity of ancient Indian civilisation.This study also provides a new and valuable record for the research on paleoclimate changes in the study area in the future.
基金supported by the National Natural Science Foundation of China (Grant Nos.41801042 and 41630754)the Second Tibetan Plateau Scientific Expedition and Research Program (STEP)(Grant No.2019QZKK0605)+3 种基金State Key Laboratory of Cryospheric SciencesChinese Academy of Sciences (Grant No.SKLCSZZ-2020)Grant received from the Asia-Pacific Network for Global Change Research (APN)(Grant reference:CRECS2020-07MYTripathee) is highly appreciatedsupported by a PIFI fellowship from the Chinese Academy of Sciences as a young staff member (2020FYC0001)。
文摘Lumbini is a world heritage site located in the southern plains region of Nepal, and is regarded as a potential site for evaluating transboundary air pollution due to its proximity to the border with India. In this study, 82 aerosol samples were collected between April 2013 and July 2014 to investigate the levels of particulate-bound mercury(PBM) and the corresponding seasonality, sources, and influencing factors.The PBM concentration in total suspended particulate(TSP) matter ranged from 6.8 pg m^(-3) to351.7 pg m^(-3)(mean of 99.7 ± 92.6 pg m^(-3)), which exceeded the ranges reported for remote and rural sites worldwide. The Hg content(PBM/TSP) ranged from 68.2 ng g^(-1) to 1744.8 ng g^(-1)(mean of 446.9 ±312.7 ng g^(-1)), indicating anthropogenic enrichment. The PBM levels were higher in the dry season(i.e.,winter and the pre-monsoon period) than in the wet season(i.e., the monsoon period). In addition, the δ^(202) Hg signature indicated that waste/coal burning and traffic were the major sources of Hg in Lumbini during the pre-monsoon period. Meanwhile, precipitation occurring during photochemical processes in the atmosphere may have been responsible for the observed Δ^(199) Hg values in the aerosol samples obtained during the monsoon period. The PBM concentration was influenced mostly by the resuspension of polluted dust during dry periods and crop residue burning during the post-monsoon period. The estimated PBM deposition flux at Lumbini was 15.7 lg m^(-2) yr^(-1). This study provides a reference dataset of atmospheric PBM over a year, which can be useful for understanding the geochemical cycling of Hg in this region of limited data.
基金supported by the second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0605)the National Natural Science Foundation of China(No.41630754)+2 种基金State Key Laboratory of Cryospheric Sciences(No.SKLCS-ZZ-2020)the Chinese Academy of Science for international Young staff support under President's International Fellowship Initiative(PIFI)(No.2020FYC0001)programthe Research Grants Council(RGC)of Hong Kong for providing Hong Kong PhD Fellowship Scheme(HKPFS),2020/21(No.PF19-33279)。
文摘Precipitation represents an important phenomenon for carbon and nitrogen deposition.Here,the concentrations and fluxes of dissolved organic carbon(DOC)and total dissolved nitrogen(TDN)with their potential sources were analyzed in wet precipitation during summer monsoon from the Northern Indo-Gangetic Plain(IGP),important but neglected area.The volume-weighted mean(VWM)concentration of DOC and TDN were 687.04 and 1210.23μg/L,respectively.Similarly,the VWM concentration of major ions were in a sequence of NH_(4)^(+)>Ca^(2+)>SO_(4)^(2-)>Na^(+)>K^(+)>NO_(3)~->Cl~->Mg^(2+)>F~->NO_(2)~-,suggesting NH_(4)^(+)and Ca^(2+)from agricultural activities and crustal dust played a vital role in precipitation chemistry.Moreover,the wet deposition flux of DOC and TDN were 9.95 and 17.06 kg/(ha year),respectively.The wet deposition flux of inorganic nitrogen species such as NH_(4)^(+)-N and NO_(3)^(-)-N were 14.31 and 0.47 kg/(ha year),respectively,demonstrating the strong influence of emission sources and precipitation volume.Source attribution from different analysis suggested the influence of biomass burning on DOC and anthropogenic activities(agriculture,animal husbandry)on nitrogenous species.The air-mass back trajectory analysis indicated the influence of air masses originating from the Bay of Bengal,which possibly carried marine and anthropogenic pollutants along with the biomass burning emissions to the sampling site.This study bridges the data gap in the less studied part of the northern IGP region and provides new information for policy makers to deal with pollution control.
文摘Ambient particulate matter (PM2.5 and PM10) concentrations were measured during two different seasons (summer and winter) at three different locations of Gurugram which is located in the Indo-Gangetic plain of India. The ambient concentrations of both PM2.5 and PM10 were higher during winter season (PM2.5: 261 μg·m-3;PM10: 440 μg·m-3) when compared to summer period (PM2.5: 114 μg·m-3;PM10: 202 μg·m-3). Potential Source Contribution Function (PSCF) analysis suggests significant seasonal variation in potential contributing locations of ambient PM2.5 over the study area. The PSCF analysis suggests that cross country transport of PM2.5 from Pakistan and Afghanistan significantly attributed to higher concentrations of PM2.5 at the study locations;whereas, PM2.5 emitted from locations in the south-western direction of the study sites attributed to the ambient PM2.5 concentrations at the study site during summer seasons. Further study is required to measure percentage contribution from different sectors and locations to the ambient particulate concentrations at the study site to develop sector specific mitigation plan.
