洱海10条入湖河流缓冲带三圈内氮含量沿程变化

2013年7月采集了10条洱海入湖河流缓冲带三圈(外圈、内圈、中圈)内沿程34个断面的表层水样,测定了水样中总氮、可溶性总氮和氨氮的含量,分析其空间分布特征.结果表明,缓冲带内3个采样点的水质变化规律有9种类型:连续升高型,连续降低型,先降低后升高的“V”字型,先升高后降低的倒“V”字型,平稳型,先升高后平稳型,先下降后平稳型,先平稳后降低型,先平稳后升高型,10条洱海入湖河流水体ρ(TN)较高,平均值为2.93mg/L,特别是内圈入湖河口处ρ(TN)平均值为3.74mg/L,对洱海威胁较大,应加大河道治理,完善缓冲带内圈村落管网收集系统和垃圾处理设施.其中,茫涌溪、黑龙溪和清碧溪流域缓冲带ρ(DTN)为0.30~2.31mg/L,占TN比例的平均值为81%,中圈水体中氮负荷明显较内圈和外圈的高,应通过测土平衡施肥以及有机肥增施来降低化肥使用量,减少农田污染物随径流流失.考虑入湖河流水质上游普遍较好,中游开始恶化,建议在缓冲带外圈建设生态砾石床、生态塘和地下渗透池等生态截蓄净化工程.

Nitrogen evolution with distance of 10 inflow rivers in the three circles of buffer zone around Erhai Lake

Surface water of 34 monitoring sections in 10inflow rivers, which were located at the 3 ribbon sections (inner, outer and middle) of the buffer zone of Erhai Lake, was sampled in July 2013. The water quality including total nitrogen, dissolved total nitrogen and ammonia nitrogen was measured and the spatial variabilities of selected water quality parameters were analyzed, aiming at put forward reasonable suggestions for the lack of function and establishment and improvement of the buffer zone. The results showed that there were 9 categories of the variation of water quality in ribbon sections, i.e., rise continuously, reduce continuously, first reduce then rise emerge “V” shape, first rise then reduce emerge inverted “V” shape, gently, first rise then steady, first reduce then steady, first keep gently then reduce, first keep gently then rise. The average ρ(TN) in 10inflow rivers of Erhai Lake was 2.93mg/L. The average ρ(TN) of estuary in the inner ribbon section was 3.74mg/L, which was a threat to the lake. So improving the collection network of sewage and garbage disposal facilities was very important in the inner ribbon section. At the same time, management strengthen of rivers should be made. ρ(DTN) of Mangyongxi River, Heilongxi River and Qingbixi River in the buffer zone were changed between 0.30mg/L and 2.31mg/L, occupying 81% of ρ(TN) averagely. The nitrogen load of the 3 rivers in the middle ribbon section in the buffer zone was obviously higher than that in the inner and outer parts. Therefore, the use of fertilizer in the farmland should be controlled so that reducing nitrogen losses with the runoff. Ecological gravel bed, ecological pond and underground infiltration pond and other ecological purification engineering measures should be built in the outer ribbon section, considering the water quality began to deteriorate from the middle reaches.