Temporal and spatial variations of net anthropogenic nitrogen inputs (NANI) in the Pearl River Basin of China from 1986 to 2015

Human activities have greatly influenced the natural nitrogen cycle, causing dramatic degradation of ecosystem function. Net anthropogenic nitrogen input (NANI) is an important factor contributing to the impact of human activities on the regional nitrogen cycle. Here, we analyzed the temporal and spatial variation of NANI in the Pearl River Basin of China between 1986 to 2015, and found that the total amount of NANI significantly increased from 3,362.25 kg N km-2 yr-1 to 8,071.15 kg N km-2 yr-1. Application of nitrogen fertilizers was the largest component of NANI in the Basin, accounting for 55.53% in the total NANI, followed by food/feed net nitrogen input (21.26%), atmospheric nitrogen deposition (12.95%), and crop nitrogen fixation (10.26%). Over the last three decades, nitrogen inputs from atmospheric nitrogen deposition have become the second largest source of NANI due to rapid industrialization and urbanization in the region. Regression analysis showed that the rapid growth of both GDP and population density were the main contributors to the increase of NANI. In addition, the increase in the number of red tides in the Pearl River Estuary was strongly correlated with NANI discharge (R2 = 0.90, p

人类活动已极大干扰了自然氮循环，导致生态系统功能发生显著退化。人为氮净输入（Net Anthropogenic Nitrogen Input, NANI）是人类活动影响区域氮循环的重要驱动因素。本研究针对中国珠江流域1986年至2015年间的NANI时空变化特征展开分析，结果显示NANI总量从3362.25 kg N·km⁻²·yr⁻¹显著增长至8071.15 kg N·km⁻²·yr⁻¹。氮肥施用是该流域NANI的最大组成部分，占NANI总量的55.53%；其次为食品/饲料净氮输入（21.26%）、大气氮沉降（12.95%）与作物固氮（10.26%）。近三十年来，受流域内快速工业化与城市化进程影响，大气氮沉降贡献的氮输入已成为NANI的第二大来源。回归分析结果表明，GDP与人口密度的双重快速增长是推动NANI上升的主要驱动因素。此外，珠江口赤潮发生频次的增加与NANI排放呈极强相关性（决定系数R²=0.90，p值