澜沧江流域水体悬浮颗粒物δ^(15)N空间差异及成因分析

Spatial Difference and Causes Analysis of the δ^(15)N of Suspended Particulate Matter in the Lancang River Basin

梯级水电建设对澜沧江流域生源物质迁移转化及其生态环境的影响目前受到国内外学者的广泛关注,本文通过使用稳定同位素技术,分析了澜沧江流域悬浮颗粒物氮同位素的空间分布差异及其成因.结果表明,澜沧江上游自然河道水体溶解无机氮(DIN)质量浓度变化范围为0. 28～0. 60 mg·L^(-1),下游水库段DIN质量浓度显著增高,变化范围为0. 39～1. 15mg·L^(-1);上游自然河道段悬浮颗粒物δ^(15)N变化范围为4. 52‰～6. 72‰,下游水库段明显增重其变化范围为2. 3‰～11. 8‰.利用Isosource软件对悬浮颗粒物来源进行分析,结果表明澜沧江流域内工业及生活污水为悬浮物颗粒物氮素的主要贡献源,占比约为42. 43%;土壤有机质、大气沉降、农业化肥的贡献率分别为22. 38%、18. 16%和17. 03%;在该流域内上游自然河道段受工业及生活污水、土壤有机质以及大气沉降共同影响,下游水库段则主要受工业及生活污水的影响.同时小湾、漫湾、大朝山这3个库区内存在藻类吸收同化作用而使得悬浮颗粒物δ^(15)N变轻的现象.

The influence of cascade hydropower construction on the migration and transformation of raw material and ecological problems in the Lancang River Basin is of concern to scholars domestically and internationally. Based on stable isotope technology,this study analyzed the spatial distribution of nitrogen in the Lancang River Basin and explained the cause of this distribution. The results showed that the range of dissolved inorganic nitrogen（ DIN） was 0. 28-0. 60 mg·L^-1,and that of DIN in the downstream area of the Lancang River was 0. 39-1. 15 mg·L^-1. The range of suspended particulate matter δ^15N in the upstream area of this river was 4. 52‰-6. 72‰,and that in the downstream reservoir section was heavier than that in the upstream reservoir,which varied between 2. 3‰ and11. 8‰. This study used Isosource to analyze the source of suspended particulate matter. The results showed that industrial wastewater and sewage,soil organic matter,atmospheric sedimentation,and agrochemicals are the main sources of suspended particulate matter,and their respective total contribution rates are 42. 43%,22. 38%,18. 16%,and 17. 03%. At the same time,the δ^15N of suspended particulate matter in Xiaowan,Manwan,and Dachaosan dams downstream of the Lancang River were influenced by algal assimilation,it leads to a reduction in the number of δ^15N of suspended particles.