Human behavioral impact on nitrogen flow—A case study of the rural areas of the middle and lower reaches of the Changjiang River, China

To assess sustainability of rural management in the Changjiang River basin, human behavioral (food consumption, lifestyle pattern, and human waste disposal) impact on nitrogen flow was quantitatively evaluated. A survey of day-to-day activities was conducted in two representative counties: Taoyuan and Taihe. Daily nitrogen intake from food per capita and potential nitrogen load from human waste on the environment were calculated. The former in Taoyuan and Taihe was 17.0 and 16.0 g N, respectively. In Taoyaun and Taihe, 26% and 67% of human waste, respectively, were utilized or returned to agricultural lands, while 74% and 33%, respectively, were discharged into rivers. Therefore, regarding the annual potential nitrogen load from human waste in Taoyuan, approximately 1.61 and 4.58 kg N per capita is returned to farmlands and directly discharged into rivers, respectively. Similarly, in Taihe, approximately 3.91 and 1.93 kg N per capita is returned to farmlands and directly discharged into rivers, respectively, annually. The impact of changing human behavior patterns on nitrogen flow was examined using a nitrogen flow model that incorporates both food production and consumption processes. The results of economic growth and urbanization were as follows: (1) increased consumption of animal-derived products in rural areas, which increases the importance of these products compared to crop products and (2) less use of organic recyclables such as disposed human waste, which makes rural communities more dependent on chemical fertilizers and imported animal feeds. China is facing serious water pollution problems; therefore, organic matter recycling within communities requires reconsideration.