洱海流域乡镇尺度上人类活动对净氮输入量的影响

人类活动引起的氮素过量输入已经成为引起水体富营养化及其他生态危害的主要原因.为了研究人类活动对流域氮素的影响,本文基于洱海流域16个乡镇行政单元的统计数据,考虑流动人口的影响,利用NANI模型估算洱海流域乡镇尺度的人类活动净氮输入量(net anthropogenic nitrogen inputs,NANI).结果表明,2014年洱海流域NANI总量为29.81×10~3t,单位面积输入强度(以氮计)为10 986 kg·(km~2·a)-1,显著高于我国平均水平.当地旅游人口带入的食品氮输入为0.26×10~3t,占到了流域居民食品氮输入的8%.从氮素的输入量的构成来看,肥料输入是最大的贡献源,占到了流域净氮输入的47%,其次为食品饲料的净氮输入.在空间分布上,乡镇单元的NANI分布呈现明显区域化特征,从流域整体上看呈现北高南低的特点.耕地或人口集中的乡镇NANI强度偏高,洱海流域具有较大的氮素污染风险.

Impact of Human Activities on Net Anthropogenic Nitrogen Inputs (NANI) at Township Scale in Erhai Lake Basin

Excessive nitrogen inputs from human activities have become the main cause of water eutrophication and related ecological hazards. In order to study the impact of human activities on nitrogen in the basin, and based on statistical data of administrative units in 16 towns and villages, this study used the NANI model to calculate net anthropogenic nitrogen inputs (NANI) at township scale in Erhai Lake basin. Results show that the total amount of NANI in Erhai Lake basin was 29.81×10³ t in 2014, and nitrogen input intensity per unit area was 10986 kg·(km²·a)^-1, significantly higher than the national average. The input of nitrogen from food by the local tourist population was 0.26×10³ t, accounting for 8% of local food nitrogen input. Nitrogen input from chemical fertilizer is the largest NANI input source, accounting for 47% of net nitrogen input in the basin, followed by net nitrogen input of food and feed. The spatial distribution of NANI at township scale shows evident regionalization, with higher values in the north and lower values in the south of the basin. The intensity of NANI in towns with cropland or population is high. The corresponding risk of nitrogen pollution in Erhai Lake basin is therefore a primary concern, and will remain so in the near future.