A quantitative model was developed to relate the amount of 137 Cs loss from the soil profile to the rate of soil erosion. According to mass balance model, the depth distribution pattern of 137 Cs in ...A quantitative model was developed to relate the amount of 137 Cs loss from the soil profile to the rate of soil erosion. According to mass balance model, the depth distribution pattern of 137 Cs in the soil profile, the radioactive decay of 137 Cs, sampling year and the difference of 137 Cs fallout amount among years were taken into consideration. By introducing typical depth distribution functions of 137 Cs into the model, detailed equations for the model were got for different soils. The model shows that the rate of soil erosion is mainly controlled by the depth distribution pattern of 137 Cs, the year of sampling, and the percentage reduction in total 137 Cs. The relationship between the rate of soil loss and 137 Cs depletion is neither linear nor logarithmic. The depth distribution pattern of 137 Cs is a major factor for estimating the rate of soil loss. Soil erosion rate is directly related with the fraction of 137 Cs content near the soil surface. The influences of the radioactive decay of 137 Cs, sampling year and 137 Cs input fraction are not large compared with others.展开更多
[Objective] The aim was to research soil erosion in boundary areas of Dongchuan City and Huize County in Yunnan Province through quantitative analysis on factors influencing soil erosion and establishment of conceptua...[Objective] The aim was to research soil erosion in boundary areas of Dongchuan City and Huize County in Yunnan Province through quantitative analysis on factors influencing soil erosion and establishment of conceptual model, providing method for land use and treatment of soil erosion. [Method] Based on Universal Soil Loss Equation （USLE）, quantitative indices determined and the conceptual model of of six factors influencing soil erosion were soil erosion was established. In addition. pixel-loss map was obtained through multiplication and soil erosive areas and the treatment schemes were proposed through statistical work of pixel-loss map and soil erosion map. [Result] In the research, annual loss modulus averaged 5 962 t/hm2, indicating the area was heavily eroded; from soil erosion map, it can be concluded that the heavily erosive area was near rivers, where wasteland and bare land dominated with slope of 30°-40° and without protective measures. [Conclusion] The research indicated that land use in the area is unreasonable erosive region should be paid more attention. In addition, the to be changed into terrace cultivation. and 51.6% of heavily wasteland is suggested to be changed into terrace cultivation.展开更多
In the mid-eastern China,there are few or no lakes which are in the absence of anthropogenic disturbances,or their sediments remain undisturbed.As a result,the reference lakes distribution and paleolimnological recons...In the mid-eastern China,there are few or no lakes which are in the absence of anthropogenic disturbances,or their sediments remain undisturbed.As a result,the reference lakes distribution and paleolimnological reconstruction approaches usually are inappropriate to estimate lake reference conditions for nutrients.This yields the necessity of using the extrapolation methods to estimate the lake reference conditions for nutrients within those regions.The lake reference conditions for nutrients could be inferred inversely from the law of mass conservation,current lake nutrient concentration,and the loadings from watershed.Considering the scarcity of hydrological and water quality data associated with lakes and watersheds in China,as well as the low requirement of the watershed nutrient loadings models for these data,the soil conservation service(SCS) distributed hydrological model and the universal soil loss equation(USLE) were applied.The SCS model simulates the runoff process of the watershed,thereby calculating dissolved nutrients annually.The USLE estimates the soil erosion and particulate nutrients annually in a watershed.Then,with the loadings from atmospheric deposition and point source,the previous annual average nutrient concentrations could be acquired given the current nutrient concentrations in a lake.Therefore,the nutrient reference conditions minimally impacted by human activities could be estimated.Based on the proposed model,the reference conditions for total nitrogen and total phosphorus of Chaohu Lake,Anhui Province,China are 0.031 mg/L and 0.640 mg/L,respectively.The proposed reference conditions estimation model is of clear physical concept,and less data required.Thus,the proposed approach can be used in other lakes with similar circumstances.展开更多
文摘A quantitative model was developed to relate the amount of 137 Cs loss from the soil profile to the rate of soil erosion. According to mass balance model, the depth distribution pattern of 137 Cs in the soil profile, the radioactive decay of 137 Cs, sampling year and the difference of 137 Cs fallout amount among years were taken into consideration. By introducing typical depth distribution functions of 137 Cs into the model, detailed equations for the model were got for different soils. The model shows that the rate of soil erosion is mainly controlled by the depth distribution pattern of 137 Cs, the year of sampling, and the percentage reduction in total 137 Cs. The relationship between the rate of soil loss and 137 Cs depletion is neither linear nor logarithmic. The depth distribution pattern of 137 Cs is a major factor for estimating the rate of soil loss. Soil erosion rate is directly related with the fraction of 137 Cs content near the soil surface. The influences of the radioactive decay of 137 Cs, sampling year and 137 Cs input fraction are not large compared with others.
文摘[Objective] The aim was to research soil erosion in boundary areas of Dongchuan City and Huize County in Yunnan Province through quantitative analysis on factors influencing soil erosion and establishment of conceptual model, providing method for land use and treatment of soil erosion. [Method] Based on Universal Soil Loss Equation （USLE）, quantitative indices determined and the conceptual model of of six factors influencing soil erosion were soil erosion was established. In addition. pixel-loss map was obtained through multiplication and soil erosive areas and the treatment schemes were proposed through statistical work of pixel-loss map and soil erosion map. [Result] In the research, annual loss modulus averaged 5 962 t/hm2, indicating the area was heavily eroded; from soil erosion map, it can be concluded that the heavily erosive area was near rivers, where wasteland and bare land dominated with slope of 30°-40° and without protective measures. [Conclusion] The research indicated that land use in the area is unreasonable erosive region should be paid more attention. In addition, the to be changed into terrace cultivation. and 51.6% of heavily wasteland is suggested to be changed into terrace cultivation.
基金Under the auspices of the Major Special Technological Program of Water Pollution Control and Management (No. 2009ZX07106-001)National Natural Science Foundation of China (No. 51079037,51109052)
文摘In the mid-eastern China,there are few or no lakes which are in the absence of anthropogenic disturbances,or their sediments remain undisturbed.As a result,the reference lakes distribution and paleolimnological reconstruction approaches usually are inappropriate to estimate lake reference conditions for nutrients.This yields the necessity of using the extrapolation methods to estimate the lake reference conditions for nutrients within those regions.The lake reference conditions for nutrients could be inferred inversely from the law of mass conservation,current lake nutrient concentration,and the loadings from watershed.Considering the scarcity of hydrological and water quality data associated with lakes and watersheds in China,as well as the low requirement of the watershed nutrient loadings models for these data,the soil conservation service(SCS) distributed hydrological model and the universal soil loss equation(USLE) were applied.The SCS model simulates the runoff process of the watershed,thereby calculating dissolved nutrients annually.The USLE estimates the soil erosion and particulate nutrients annually in a watershed.Then,with the loadings from atmospheric deposition and point source,the previous annual average nutrient concentrations could be acquired given the current nutrient concentrations in a lake.Therefore,the nutrient reference conditions minimally impacted by human activities could be estimated.Based on the proposed model,the reference conditions for total nitrogen and total phosphorus of Chaohu Lake,Anhui Province,China are 0.031 mg/L and 0.640 mg/L,respectively.The proposed reference conditions estimation model is of clear physical concept,and less data required.Thus,the proposed approach can be used in other lakes with similar circumstances.
