洱海悬浮颗粒物时空分布特征及其环境学意义

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

水体ρ(SPM)(SPM表示悬浮颗粒物)是衡量水污染程度的指标之一,其在湖泊内源释放和水环境变化中扮演重要角色.通过采集不同季节、不同区域、不同水深的洱海SPM,研究其时空分布特征,并对其成因进行解析,从而阐明其对洱海水质的影响机制.结果表明:①ρ(SPM)的季节性变化趋势为夏季>秋季>冬季>春季,藻类生长是其夏季明显高于其他季节的主要原因,其空间分布规律为中部>北部≥南部,其垂向分布规律为表层>中层>底层.②水体ρ(SPM)与水中溶解性有机物浓度间的关系表明,上覆水中SPM的迁移转化是影响上覆水溶解性有机物的重要因素.③DON(溶解性有机氮)的Kd(分配系数)(lg Kd为6. 12±0. 47)高于TDN(溶解性总氮)(lg Kd为5. 70±0. 48),表明DON比TDN具有更高的颗粒反应性,DON可以很大程度上被浮游植物吸收利用,产生更高的ρ(SPM),使得湖泊存在富营养化的风险.研究显示,洱海水体ρ(SPM)受入湖河流和湿沉降的影响较小,受内源代谢影响较大,较高水温、较高pH(8. 98)、较低ρ(DO)均是导致藻源性ρ(SPM)增大的原因.

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 study,the temporal and spatial distribution characteristics of SPM in Erhai Lake in different seasons,different regions and different water depths were studied. The causes of SPM were analyzed,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 > spring,with algae growth being the main reason for the obvious higher content of SPM in summer. In addition,the regional distribution showed the variation trends as: central >northern ≥ southern,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),indicating that DON possessed a higher particle reactivity. DON can be absorbed and utilized by phytoplankton,thereby producing a higher SPM concentration,and in turn posing a risk of lake eutrophication. The 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 temperature,higher pH(8. 98),and lower dissolved oxygen concentration were considered to contribute to the increment of algae-related SPM concentration.