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| Spatial-temporal patterns and driving forces of nitrogen flows for agricultural plantation-consumption system in Yangtze River Economic Belt |
| Received:September 26, 2020 |
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| KeyWord:Yangtze River Economic Belt;non-point source pollution;material flow analysis;spatial analysis;spatial-temporal patterns;driving forces |
| Author Name | Affiliation | E-mail | | PANG Ai-ping | Key Laboratory for Water and Sediment Science of the Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, China
Department of Public Management, Nanjing Academy of Administration, Nanjing 210046, China | | | LI Chun-hui | Key Laboratory for Water and Sediment Science of the Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, China | chunhuili@bnu.edu.cn | | YI Yu-jun | Key Laboratory for Water and Sediment Science of the Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, China | |
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| Abstract: |
| To address the pollution caused by the excessive use of nitrogen(N)in agricultural and rural areas, this study used material flow analysis(MFA)and spatial analysis to depict the spatial and temporal evolution of N flows in the agricultural plantation-consumption system in the Yangtze River Economic Belt. The results showed that inorganic N fertilizer input was 1.088 5×1010 kg N in 1998, which increased at a rate of 1.14% until 2012 and then subsequently began to decrease. In 2018, the amount of inorganic N fertilizer applied was lower than that of 1998, but it remained the major source of N for the Yangtze River Economic Belt. The effective N output, in the form of crop production, was not affected by fluctuation of N input. The crop yield in 2018 was 18.97% and 25.71% higher than the yield in 1998 and 2008, respectively. In recent years, the quantity of breeding pigs in the Yangtze River Economic Belt has declined; however, the N emissions from residents and breeding areas have not reduced significantly. Owing to the acceleration of urbanization and the improvement of rural living environments, N emissions through directly discharged sewage in the rural area has decreased. The average annual percentage of N runoff losses from the pathways of inorganic N fertilizer application, feces and organic wastes production, atmospheric deposition, straw return to farmland, direct sewage discharge, and irrigation was 0.53, 0.28, 0.11, 0.04, 0.02, and 0.01, respectively. The influence of the different pathways varied over time; for instance, the contribution of feces and organic wastes production to N emissions dropped from 0.33 to 0.26 in 2018. Spatially, the high-risk areas of agricultural non-point source pollution are mainly distributed through the northeast to the southwest parts of Sichuan, the central and southern parts of Zhejiang, the northeast and southeast parts of Chongqing, and most parts of Yunnan, which account for 22.83%, 22.10%, 21.80%, and 25.14% of the province(city)area, respectively. In the above provinces, approximately 20% of the remaining N in the soil is lost through N runoff, which in turn leads to eutrophication of water bodies. |
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