苏州河市郊段底泥中COD_(Cr)和NH_3-N的空间分布特征

对苏州河截流区外河段(城郊段)东大盈河口—北新泾,按河道形态,支流与城镇分布等因素,沿程采集24个底泥柱样,测定其不同部位不同深度底泥中COD_(Cr)和NH_3-N含量,分析COD_(Cr)和NH_3-N在沿程和垂向上的分布特征及其成因。结果表明,底泥中污染沿程分布呈不规则波状起伏,东大盈河、蕴藻浜、盐铁塘、封浜、华漕港、新槎浦等支流口,浮泥层中COD_(Cr)含量达2万mg/kg,超过背景值2—3倍,支流口下游200m范围内均较高;黄渡小支流口、华漕港支流口浮泥层中NH_3-H含量达250mg/kg,超过背景值3倍。在垂向分布上,底泥柱样都出现峰值分布,在某些弯道及支流口出现递减分布。底泥耗氧污染程度主要与支流及其排污量有关,其次是弯道凸岸处污染物易于沉积富集。这为苏州河市郊段环境综合治理、底泥疏浚和处置提供了科学依据。

Spatial Distribution Characteristics of COD_(Cr) and NH3-N in the Sediment of Suburban Reach of Suzhou Creek

Outside the interception area reach (suburban reach) of Suzhou Creek, Dongdayin estuary-Beixinjing, according to the feature of river, factors of branch small towns distribution, along the reach to collect 24 sediment column samples, and deteimine the contents of CODCr and NH3-N at different sites and depths of sediment, and analyzed the distrrbution characteristics and formation of CODCr and NH,-N along the reach and virtically. The result showed that along the reach, distribution of contaminated sediment was irregular and uneven, the contents of CODCr in the sediment of Dayin estuary, Wunzhouban, Yantietang, Fonban, Huazhaogang and Xincharpu etc. branches estuaries were higher than 20 thousand mg/kg, exceeding 2 ~ 3 fold of background value, 200 m away from the branches estuaries were rather high; the small branches estuaries of Huargdu and Huazhaogang estuaries, NH.,-N contents in sediment were 250mg/kg, exceeding 3 fold of background value. In virtical distribution, the sediment column samples appeared peak distribution at certain curve channels and branches estuaries, appeared gradually decreased distribution. Degree of oxygen consumed of sediments, firstly correlated with branches and their amount of pollutants discharged, and secondly, the projected peak of cure channel where the pollutants could easily deposit and cencentrate. These could provide scientific bases for comprehensivte harness of creek environment, and dredging and disposing sediments.