Spatial and Temporal Distribution of Suspended Particulate Matter in Lake Erhai and Its Environmental Significance

Suspended particulate matter (SPM) content in waterbody is one of the indicators for measuring the degree of water pollution. It plays an important role in endogenous release and water environment change of lakes. In this studyꎬ the temporal and spatial distribution characteristics of SPM in Erhai Lake in different seasonsꎬ different regions and different water depths were studied. The causes of SPM were analyzedꎬ and its influence mechanism on the water quality of Erhai Lake was also clarified. The obtained results indicated that: (1) The seasonal variation of SPM content followed the pattern as: summer > autumn > winter > springꎬ with algae growth being the main reason for the obvious higher content of SPM in summer. In additionꎬ the regional distribution showed the variation trends as: central > northern ≥ southernꎬ surface > middle > bottom. (2) The relationship between SPM content and dissolved organic matter in overlying water indicated that migration and transformation of SPM were important factors affecting the behavior of dissolved organic matter in overlying water. (3) The partition coefficient (Kd) of dissolved organic nitrogen (DON) ( lg Kd = 6􀆰 12±0􀆰 47) was higher than that of dissolved total nitrogen (TDN)(lg Kd = 5􀆰 70±0􀆰 48)ꎬ indicating that DON possessed a higher particle reactivity. DON can be absorbed and utilized by phytoplanktonꎬ thereby producing a higher SPM concentrationꎬ and in turn posing a risk of lake eutrophication. The 环 境 科 学 研 究 第 32 卷 obtained results indicated that the influence deriving from inflow river and wet deposition on SPM distribution was relatively small. It was mainly affected by endogenous metabolism. Higher water temperatureꎬ higher pH (8􀆰 98)ꎬ and lower dissolved oxygen concentration were considered to contribute to the increment of algae ̄related SPM concentration.