成渝地区双城经济圈人类活动氮磷输入时空演变及其驱动因素

随着城市化进程的加快，高强度人类活动重塑了氮磷等的自然地球化学循环，养分的高效利用与可持续管理面临挑战. 选取地处长江经济带与“一带一路”交汇处的成渝地区双城经济圈为研究区域，基于净人为氮磷输入模型，明晰了人类活动氮磷输入(NANI和NAPI)强度及其组成结构，厘清了其时间轨迹及空间格局，辨识了主要社会经济影响因素的相对贡献度. 结果表明:①2011—2019年成渝地区双城经济圈平均NANI和NAPI分别为13 063 kg/(km2·a)(以N计，下同)和2 291 kg/(km2·a)(以P计，下同)，高于长江经济带尺度和全国尺度的平均水平，但低于长三角和长江中游城市群. 非点源NANI和NAPI占比较高，农用化肥输入量为主要来源，食品/饲料养分输入量次之. ②时间尺度上，2011—2019年研究区NANI和NAPI均呈整体下降趋势，分别降低了43.2%和25.9%，其中非点源NANI和NAPI分别降低了44.9%和26.8%，但点源NANI和NAPI分别上升了7.0%和3.3%；空间尺度上，2011—2019年NANI和NAPI平均强度较高的地区大部分集中于研究区域中部以及成都市、重庆市的周边地市，其中德阳市NANI和NAPI均为最高，雅安市NANI和NAPI均为最低. ③NANI和NAPI除与其组分直接相关外，与农村人口密度、耕地面积占比均呈显著正相关，与森林覆盖率呈显著负相关(P<0.05). 研究显示，城市化驱动下的人为氮磷输入时空格局特征明显，我国相关管理措施对其具有积极作用，且区域协同治理已成为破解环境问题的关键. 

Spatiotemporal Evolution and Driving Factors of Nitrogen and Phosphorus Input from Human Activities in Chengdu-Chongqing Economic Circle

With increasing urbanization, intensive human activities have reshaped the natural geochemical cycles of nitrogen and phosphorus, challenging the efficient utilization and sustainable management of nutrients. The Chengdu-Chongqing Economic Circle was chosen as the study region, which locates at the intersection of the Yangtze River Economic Belt and ‘the Belt and Road’. Based on the net anthropogenic nitrogen (N) and phosphorus (P) input model (NANI and NAPI), the total N and P input of human activities and its composition characteristics were analyzed, the spatiotemporal heterogeneity of N and P input of human activities were clarified, and the relative contribution rates of main socio-economic influencing factors were identified. The results showed that: (1) From 2011 to 2019, the average NANI and NAPI of the Chengdu-Chongqing Economic Circle were 13,063 kg/(km2·a) (in N) and 2,291 kg/(km2·a) (in P), respectively. They are higher than the NANI and NAPI of the Yangtze River Economic Belt and the national average level, but lower than the Yangtze River Delta and the Yangtze River middle reaches city cluster. Non-point sources accounted for a high proportion, with agricultural fertilizer input as the main sources, followed by net food and feed imports. (2) In terms of time scale, from 2011 to 2019, the NANI and NAPI in the Chengdu-Chongqing Economic Circle decreased by 43.2% and 25.9%, respectively. Non-point source NANI and NAPI decreased by 44.9% and 26.8%, while point source NANI and NAPI increased by 7.0% and 3.3%, respectively. In terms of spatial scale, most of the prefecture-level cities with high average intensity of NANI and NAP from 2011 to 2019 were concentrated in the central part of the study region and the neighboring cities of Chengdu and Chongqing. The NANI and NAPI were the highest in Deyang and the lowest in Ya'an. (3) NANI and NAPI were directly correlated with their components. NANI and NAPI were significantly positively correlated with the rural population density and the proportion of cultivated land area, and were significantly negatively correlated with the forest coverage rate (P<0.05). The research shows that the spatiotemporal pattern of NANI and NAPI driven by urbanization is obvious. Relevant management measures in China have a positive effect on it, and regional collaborative governance has become the key to solve environmental problems.