滨湖河网叶绿素a时空分布特征及相关性分析

以中国太湖梅梁湾东部的无锡市滨湖区河网为例，分别在2018年丰水期（8月）和枯水期（11月）以及2019年平水期（3月）对分布在河网各处的41个点位进行监测，并对水样中的叶绿素a（Chl-a）、pH等14个理化指标进行测定。将河网分为4条干流为代表的4个主要水系，采用主成分分析和相关性分析，判断不同的水质因子对Chl-a浓度变化的影响，初步识别每个水系中的主要影响因子；将水质因子分别列入线性逐步回归分析中，得出各水系及整个河网关于Chl-a的线性逐步回归方程，并分析主要因子对该河网中Chl-a含量变化的影响机理。结果显示:滨湖河网Chl-a 3次监测整体平均值为22.617 mg/m3，丰水期、枯水期、平水期3期平均值分别为17.256，48.878，1.717 mg/m3。空间上，Chl-a总体呈现河网北部梁溪河水系最高，东部骂蠡港、东南角曹王泾次之，西部陆典桥浜最低的规律。整个河网与Chl-a显著相关的有高锰酸盐指数、SS、Hg、PO₄3-。梅梁湾调水对北部河网有藻类补充作用，且输移过程中携带的溶解态或沉积态营养物质如SS、TN等在夏秋季节成为藻类增长的重要来源。骂蠡港与西部陆典桥浜水系主要水源由五里湖提供，其水质受五里湖水质的直接影响；东南部曹王泾水系的2条支流汇入对其水质改善有促进作用。

SPATIO-TEMPERAL DISTRIBUTION CHARACTERISTICS AND CORRELATION ANALYSIS OF CHLOROPHYLL-A IN RIVER NETWORK

Taking the river network in Binhu district as an example, 41 points distributed throughout the river network were monitored in 2018 during the wet season (August) and dry season (November), and 2019 during the normal season (March), and 14 physicochemical indexes such as chlorophyll a (chl-a) and pH were measured. The river network was divided into four main river systems. Principal component analysis and correlation analysis were used to judge the influence of different water quality factors on chl-a concentration change, and the main influencing factors in each water system were preliminarily identified. The water quality factors were included in the linear stepwise regression analysis to obtain the equation of chl-a for each river system and the whole river network. The mechanism of these main factors affecting chl-a content change in the river network was discussed. The results showed that the overall average value of the monitoring in the three phases of chl-a in the river network was 22.617 mg/m3, and the average value in the three phases of abundant season, dry season and smooth season was 17.256, 48.878, 1.717 mg/m3, respectively. Spatially, the overall pattern of chl-a was that the Liangxi River system was the highest in the north of the river network, followed by Ligang in the east and Caowangjing in the southeast, and the lowest in Ludianqiao in the west. The COD_Mn permanganate index, SS, Hg and PO₄3- were significantly correlated with Chl-a in the whole river network. Meiliang bay water diversion played a supplementary role for algae in the northern river network, and the input dissolved or deposited nutrients, such as TP and TN, were important sources of algae growth in summer and autumn. The main water source of Maligang and Ludianqiaobang River system in the west was provided by Wuli lake, and their water quality was directly affected. The inflow of two tributaries of Caowangjing system in the southeast promoted the improvement of water quality.