“…NAPI can be calculated as the sum of its major components, which include P fertilizer application, nonfood P and P in net food and feed imports (Hong et al, ). Evidence from Lake Erie (H. Han et al, ), the Baltic Sea (Hong et al, ), Lake Michigan (H. Han et al, ), and some watersheds in China (Chen, Hu, Guo, et al, ; Chen et al, ; Zhang, Swaney, Hong, et al, ) showed that NAPI has advantages not only in predicting riverine P fluxes but also in determining the extent of P accumulation and surplus (Y. Han et al, ), in assessing riverine P pollution (Chen, Hu, Guo, et al, ; H. Han et al, ; Russell et al, ), and in evaluating the pattern of P retention (Hong et al, ).…”