南通近岸海域水质特征的因子及聚类分析研究

基于2012年5月、8月和10月3个航次水质环境调查资料,利用因子分析探讨南通近岸海域海水水质主要影响因素的空间分布特征;通过站位聚类分析进行了区域类别划分,并对各区的主要影响因素及其季节变化进行了分析。因子分析结果显示,南通近岸海域主要存在4种水质影响因素,总体表现为受近岸污染源的控制影响,其中F1(NO-2-N、石油类)高值区位于冷家沙西北侧,是北上长江径流与外海水在冷家沙浅滩处相遇作用的结果;F2(DO、NO-3-N)体现了外海水进入的影响,其值由近岸向离岸逐渐增大;F3(COD、PO3-4-P)显示了河流输入的影响,F4(NH+4-N)体现了人为源的作用,两者高值区均分布于栟茶运河河口和长江口北侧。站位聚类分析显示,南通近岸海域可划分为5个类型区,其中A区(小洋口港近岸区域)受陆源河口排污影响,且所处水道尾部水文动力条件弱,污染严重;B区(烂沙洋海域)受西侧相邻的河口排污区和近岸污染影响,在主要潮汐通道的强动力作用下,污染程度较轻;C区(冷家沙区域)为B、D两区之间的潮滩区,受到B、D两区域污染的综合影响;D区(冷家沙南侧近岸海域)主要受近岸污染影响,为小庙洪和网仓洪的强动力控制区;长江入海携带污染物及水流扰动对E区(东南部离岸海域)有一定干扰。不同空间类型分区体现了区域动力地貌在海洋污染物分布中的强烈影响。

A research on water quality characteristics of Nantong nearshore based on factor analysis and cluster analysis

Based on the water quality survey data of three seasons from 16 monitoring sites in 2012,factor analysis was used to study the main factors of water quality and their spatial distribution characteristics. By cluster analysis,we estimated the similarity of the sites and divided Nantong offshore into diverse areas. According to factor analysis,there were four factors impacting water quality of Nantong nearshore. F1 was concentrated in the northwest of Lenjia Sandbank caused by the interactions of runoff of Changjiang River and water from open sea.The concentrations of F2 which reflect the effection of water from open sea in the nearshore part were lower than that in the offshore part.The areas with high-value of F3 which reflect the influence of river input and F4 which represent anthropogenic source were distributed in the estuary of Bencha Canal and the Changjiang River. Nantong offshore marine areas could be divided into 5 areas based on cluster analysis. District A adjacent to lands where river feeds into sea was heavily polluted because of its weak water dynamic condition. Pollution of district B covered tidal channel area was lighter. District C located between district B and district D was influenced by both of them. District D which was under the control of intense water dynamic condition caused by Xiaomiaohong Channel and Wangcanghong Channel was influenced by land-based pollution. Pollutants and flows from the Changjiang River influenced district E to some extent. Different types of partitions indicated strong influence on pollutant distribution caused by regional hydrodynamic pattern.