The subtropical hilly region of China is a region with intensive crop and livestock production,which has resulted in serious N pollution in soil,water and air.This review summarizes the major soil N cycling processes ...The subtropical hilly region of China is a region with intensive crop and livestock production,which has resulted in serious N pollution in soil,water and air.This review summarizes the major soil N cycling processes and their influencing factors in rice paddies and uplands in the subtropical hilly region of China.The major N cycling processes include the N fertilizer application in croplands,atmospheric N deposition,biological N fixation,crop N uptake,ammonia volatilization,N_(2)O/NO emissions,nitrogen runoff and leaching losses.The catchment nutrients management model for N cycle modeling and its case studies in the subtropical hilly region were also introduced.Finally,N management practices for improving N use efficiency in cropland,as well as catchment scales are summarized.展开更多
To explore the causes of the ecological environment deterioration of lakes in the Inner Mongolia Plateau,this study took a typical inland lake Daihai as an example,and investigated the groundwater recharge in the proc...To explore the causes of the ecological environment deterioration of lakes in the Inner Mongolia Plateau,this study took a typical inland lake Daihai as an example,and investigated the groundwater recharge in the process of lake shrinkage and eutrophication.Using the radon isotope(^(222)Rn)as the main means of investigation,the ^(222)Rn mass balance equation was established to evaluate the groundwater recharge in Daihai.The spatial variability of ^(222)Rn activity in lake water and groundwater,the contribution of groundwater recharge to lake water balance and its effect on nitrogen and phosphorus pollution in lake water were discussed.The analysis showed that,mainly controlled by the fault structure,the activity of ^(222)Rn in groundwater north and south of Daihai is higher than that in the east and west,and the difference in lithology and hydraulic gradient may also be the influencing factors of this phenomenon.The ^(222)Rn activity of the middle and southeast of the underlying lake is greater,indicating that the ^(222)Rn flux of groundwater inflow is higher,and the runoff intensity is greater,which is the main groundwater recharge area for the lake.The estimated groundwater recharge in 2021 was 3017×10^(4) m^(3),which was 57%of the total recharge to the lake,or 1.6 times and 8.1 times that of precipitation and surface runoff.The TN and TP contents in Daihai have been rising continuously,and the average TN and TP concentrations in the lake water in 2021 were 4.21 mg·L^(−1) and 0.12 mg·L^(−1),respectively.The TN and TP contents entering the lake with groundwater recharge were 6.8 times and 8.7 times above those of runoff,accounting for 87%and 90%of the total input,respectively.The calculation results showed that groundwater is not only the main source of recharge for Daihai,but also the main source of exogenous nutrients.In recent years,the pressurized exploitation of groundwater in the basin is beneficial in increasing the groundwater recharge to the lake,reducing the water balance difference of the lake,and slowing down the shrinking degree of the lake surface.However,under the action of high evaporation,nitrogen and phosphorus brought by groundwater recharge would become more concentrated in the lake,leading to a continuous increase in the content of nutrients and degree of eutrophication.Therefore,the impact of changes in regional groundwater quantity and quality on Daihai is an important issue that needs further assessment.展开更多
Intensive practices in forest soils result in dramatic nitrogen(N)losses,particularly ammonia(NH_(3))volatilization,to adjacent environmental areas.A soil column experiment was conducted to evaluate the effect of bamb...Intensive practices in forest soils result in dramatic nitrogen(N)losses,particularly ammonia(NH_(3))volatilization,to adjacent environmental areas.A soil column experiment was conducted to evaluate the effect of bamboo biochar on NH_(3) volatilization from tea garden and bamboo forest soils.The results showed that biochar amendment effectively reduced NH_(3) volatilization from tea garden and bamboo forest soil by 79.2%and 75.5%,respectively.The soil pH values increased by 0.53-0.61 units after biochar application.The NH_(4)^(+)-N and total N of both soils were 13.8-29.7%and 34.0-41.9%higher under the biochar treatments than under the control treatment,respectively.In addition,the soil water contents of the two biochar-amended soils were significantly higher(P<0.05),by 10.7-12.5%,than that of the soils without biochar amendment.Therefore,biochar mitigates NH_(3) volatilization from the tested forest soils,which was due to the increases in soil NH_(4)^(+)-N,total N and water contents after biochar amendment.Our main findings suggest that biochar addition is an effective management option for sustainable forest management.展开更多
This paper presented the first part of the studies about the development of a tool for groundwater contamination prediction, conducted by the Laboratory of Sciences and Technology of Water (UAC/Benin). The investigati...This paper presented the first part of the studies about the development of a tool for groundwater contamination prediction, conducted by the Laboratory of Sciences and Technology of Water (UAC/Benin). The investigation made consisted in estimating the combined effect of retardation factor and biodegradation on migration processes of leachate, in the underlying soils of household waste dumpsites, without active safety barrier. Leachate infiltration tests for different initial conditions were made on soil columns and the breakthrough curves were traced for electrical conductivity, the 5 day biochemical oxygen demand (BOD5) and total kjeldahl nitrogen TKN. A mathematical migration model was developed and solved numerically by finite difference method and implemented with Matlab R2013a. Thus, the calibration of the model was made with electric conductivity data by determining the dispersion coefficient of the studied soils (D = 0.96 cm2/min). Simulations for model verification showed that the established model can perfectly predict the migration of biodegradable organic pollution (BOD5) but did not give conclusive results for the monitoring of nitrogenous organic matter (TKN). The influence of the retardation factor on the migration of biodegradable organic pollutants in soils was linear, while the biodegradation rate of the organic material on migration showed an exponential pattern.展开更多
基金supported by the National Natural Science Foundation of China(41771336,41471267,4211101081,42161144002)Youth Innovation Promotion Association of the Chinese Academy of Sciences(Y2021102)+1 种基金Key Research and Development Program of Hunan Province(2020NK2011)Chinese Academy of Science and Technology Service Network Initiative Project(KFJ-STSQYZD-2021-22-002).
文摘The subtropical hilly region of China is a region with intensive crop and livestock production,which has resulted in serious N pollution in soil,water and air.This review summarizes the major soil N cycling processes and their influencing factors in rice paddies and uplands in the subtropical hilly region of China.The major N cycling processes include the N fertilizer application in croplands,atmospheric N deposition,biological N fixation,crop N uptake,ammonia volatilization,N_(2)O/NO emissions,nitrogen runoff and leaching losses.The catchment nutrients management model for N cycle modeling and its case studies in the subtropical hilly region were also introduced.Finally,N management practices for improving N use efficiency in cropland,as well as catchment scales are summarized.
基金national key research and development program“Spatio-temporal evolution and mechanism of ecological degradation of water resources in the‘one lake and two seas’basin”(2019YFC0409201).
文摘To explore the causes of the ecological environment deterioration of lakes in the Inner Mongolia Plateau,this study took a typical inland lake Daihai as an example,and investigated the groundwater recharge in the process of lake shrinkage and eutrophication.Using the radon isotope(^(222)Rn)as the main means of investigation,the ^(222)Rn mass balance equation was established to evaluate the groundwater recharge in Daihai.The spatial variability of ^(222)Rn activity in lake water and groundwater,the contribution of groundwater recharge to lake water balance and its effect on nitrogen and phosphorus pollution in lake water were discussed.The analysis showed that,mainly controlled by the fault structure,the activity of ^(222)Rn in groundwater north and south of Daihai is higher than that in the east and west,and the difference in lithology and hydraulic gradient may also be the influencing factors of this phenomenon.The ^(222)Rn activity of the middle and southeast of the underlying lake is greater,indicating that the ^(222)Rn flux of groundwater inflow is higher,and the runoff intensity is greater,which is the main groundwater recharge area for the lake.The estimated groundwater recharge in 2021 was 3017×10^(4) m^(3),which was 57%of the total recharge to the lake,or 1.6 times and 8.1 times that of precipitation and surface runoff.The TN and TP contents in Daihai have been rising continuously,and the average TN and TP concentrations in the lake water in 2021 were 4.21 mg·L^(−1) and 0.12 mg·L^(−1),respectively.The TN and TP contents entering the lake with groundwater recharge were 6.8 times and 8.7 times above those of runoff,accounting for 87%and 90%of the total input,respectively.The calculation results showed that groundwater is not only the main source of recharge for Daihai,but also the main source of exogenous nutrients.In recent years,the pressurized exploitation of groundwater in the basin is beneficial in increasing the groundwater recharge to the lake,reducing the water balance difference of the lake,and slowing down the shrinking degree of the lake surface.However,under the action of high evaporation,nitrogen and phosphorus brought by groundwater recharge would become more concentrated in the lake,leading to a continuous increase in the content of nutrients and degree of eutrophication.Therefore,the impact of changes in regional groundwater quantity and quality on Daihai is an important issue that needs further assessment.
基金This study was financially supported by the Natural Science Foundation of Jiangsu Province(BK20160931)the Natural Science Foundation of China(31601832)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘Intensive practices in forest soils result in dramatic nitrogen(N)losses,particularly ammonia(NH_(3))volatilization,to adjacent environmental areas.A soil column experiment was conducted to evaluate the effect of bamboo biochar on NH_(3) volatilization from tea garden and bamboo forest soils.The results showed that biochar amendment effectively reduced NH_(3) volatilization from tea garden and bamboo forest soil by 79.2%and 75.5%,respectively.The soil pH values increased by 0.53-0.61 units after biochar application.The NH_(4)^(+)-N and total N of both soils were 13.8-29.7%and 34.0-41.9%higher under the biochar treatments than under the control treatment,respectively.In addition,the soil water contents of the two biochar-amended soils were significantly higher(P<0.05),by 10.7-12.5%,than that of the soils without biochar amendment.Therefore,biochar mitigates NH_(3) volatilization from the tested forest soils,which was due to the increases in soil NH_(4)^(+)-N,total N and water contents after biochar amendment.Our main findings suggest that biochar addition is an effective management option for sustainable forest management.
基金The authors gratefully acknowledge the International Foundation for Science(IFS),Stockholm,for supporting the present work under the IFS Grant W/5840-1.
文摘This paper presented the first part of the studies about the development of a tool for groundwater contamination prediction, conducted by the Laboratory of Sciences and Technology of Water (UAC/Benin). The investigation made consisted in estimating the combined effect of retardation factor and biodegradation on migration processes of leachate, in the underlying soils of household waste dumpsites, without active safety barrier. Leachate infiltration tests for different initial conditions were made on soil columns and the breakthrough curves were traced for electrical conductivity, the 5 day biochemical oxygen demand (BOD5) and total kjeldahl nitrogen TKN. A mathematical migration model was developed and solved numerically by finite difference method and implemented with Matlab R2013a. Thus, the calibration of the model was made with electric conductivity data by determining the dispersion coefficient of the studied soils (D = 0.96 cm2/min). Simulations for model verification showed that the established model can perfectly predict the migration of biodegradable organic pollution (BOD5) but did not give conclusive results for the monitoring of nitrogenous organic matter (TKN). The influence of the retardation factor on the migration of biodegradable organic pollutants in soils was linear, while the biodegradation rate of the organic material on migration showed an exponential pattern.
