Xin Liu; Hu Sheng; Songyan Jiang; et al.

自从17世纪00年代以来，中国对磷的开采、使用和出口已经强化，正在耗尽这种关键的营养物质并且污染了淡水供应。磷是种植粮食的一个关键元素，但是随着它流失到湖泊、河流和海洋中，它逐渐变得不容易获得。同时，大规模的磷流失导致了富营养化，这可能导致藻华，植物过度拥挤和氧耗尽。Zengwei Yuan及其同事对自从17世纪00年代以来中国的磷循环进行了建模，并且评估了富营养化的潜力。这组作者报告说，中国强化了其磷循环从而养活不断增加的人口以及满足人们对于动物蛋白的需求，特别是在过去大约60年间。此外，磷在内陆水体和陆地上积累。根据对中国现有的磷酸盐矿石储量的粗略估计，这组作者估计，这个储量将会在大约35年内耗尽。然而，这组作者发现，有效使用可能把磷耗尽推迟超过20年。这组作者说，这些发现为建立一个可持续的磷循环提供了数据，从而可能带来有效率的粮食生产和健康的水供应。

　　Phosphorus (P) is an essential nutrient for living systems with emerging sustainability challenges related to supply uncertainty and aquatic eutrophication. However, its long-term temporal dynamics and subsequent effects on freshwater ecosystems are still unclear. Here, we quantify the P pathways across China over the past four centuries with a life cycle process-balanced model and evaluate the concomitant potential for eutrophication with a spatial resolution of 5 arc-minutes in 2012. We find that P cycling in China has been artificially intensified during this period to sustain the increasing population and its demand for animal protein-based diets, with continuous accumulations in inland waters and lands. In the past decade, China’s international trade of P involves net exports of P chemicals and net imports of downstream crops, specifically soybeans from the United States, Brazil, and Argentina. The contribution of crop products to per capita food P demand, namely, the P directly consumed by humans, declined from over 98% before the 1950s to 76% in 2012, even though there was little change in per capita food P demand. Anthropogenic P losses to freshwater and their eutrophication potential clustered in wealthy coastal regions with dense populations. We estimate that Chinese P reserve depletion could be postponed for over 20 y by more efficient life cycle P management. Our results highlight the importance of closing the P cycle to achieve the cobenefits of P resource conservation and eutrophication mitigation in the world’s most rapidly developing economy.

　　（来源：PNAS, 2016, 113(10): 2609–2614）