春季香溪河库湾CODMn时空分布及其影响因子初探

于2012年春季在香溪河库湾合理布置断面观测，分析水体高锰酸盐指数(CODMn)的时空分布特征，并对CODMn与水体中叶绿素a、溶解氧(DO)、水体垂向稳定系数、总氮(TN)和溶解性硅酸盐(D Si)进行相关分析，以期为香溪河流域有机污染的治理提供支持和指导。结果表明：春季香溪河库湾CODMn浓度变化范围为1.40～5.36 mg/L，4月CODMn均值明显高于3月和5月，为366 mg/L，整个春季CODMn浓度从下游至上游呈现明显增大的趋势。相关分析发现，春季水华暴发期间，CODMn与叶绿素a显著正相关(分别为072和074)，而在未暴发水华的3月二者的相关性不显著。浮游植物和水体稳定系数是影响CODMn变化的主要因素。倒灌异重流使得高含氮、低CODMn浓度的长江干流水体进入库湾下游并稀释CODMn浓度。CODMn与DO在3月和5月的弱相关关系为香溪河CODMn特殊的分布特征提供了其它合理的解释,其分布特征受多种因素的共同影响。春季库湾上游有机污染趋于恶化，限制支流特别是上游污染物的排放是改善有机污染现状的有效途径

SPATIAL AND TEMPORAL DISTRIBUTIONS OF CODMN AND THEIR INFLUENCING FACTORS IN XIANGXI BAY DURING SPRING

With the objective of supporting and guiding conservation of Xiangxi Bay (XXB),filed data were collected in Xiangxi Bay during the spring of 2012 to investigate the spatial and temporal distribution of permanganate index of oxygen demand(CODMn) and analyze the response of CODMn to chlorophyll a (Chl a),dissolved oxygen (DO),the vertical stability factor of water,total nitrogen (TN) and soluble silicates.The results show that the variation of CODMn concentration in XXB ranged from 140 to 536 mg/L in spring.The average concentration of CODMn was significantly higher in April than that in March and May.Both the value of Chl a and CODMn became markedly high with the outbreak of algal blooms.In April and May,significantly positive correlation was observed between CODMn and Chl a(rApril=072,rMay=074) ,whereas the correlation was weak in March.The concentration of CODMn increased significantly across downstream to upstream in the entire spring.Chl a and water stability factor were the main factors affecting the variation of CODMn when spring algal bloom occurred.The increase in water stability factor of top layers caused accumulation of algae and organic pollutants in surface water,leading to the increase of CODMn.On the other hand,the correlation between CODMn and TN was negative.In the estuary,silicate appeared with higher densities than in the upstream.Diatoms played a critical role in shaping the spatial distribution of soluble silicate in XXB.There was density flow which carried a large amount of nitrogen from Changjiang (CJ) mainstem into XXB,and much water with high CODMn from XXB into CJ,leading to decreased CODMn concentration in XXB.The water body was at high eutrophication level in the upper reach of XXB.Density flow diluted Chl a in the estuary but increased the risk of occurring algal bloom in the downstream.The weak correlation coefficient between CODMn and DO in March and May provided a good explanation for the special distribution of CODMn in XXB.The distribution of CODMn was influenced by many factors,including biochemical elements and hydrodynamic forces.In addition,further analysis indicated that exogenous pollution was still the main reason for the development of organic pollution.Because the sources of water pollution are different,a variety of pollution prevention is needed.Increased recognition of external pollution is finally highlighted from watershed management perspectives.The organic pollution in the upper reach of XXB gets worse in the spring,suggesting that reduce the discharge of the organic pollutions is an effective measure to improve the water quality in XXB