Composition analysis of colored dissolved organic matter in Taihu Lake based on three dimension excitation-emission fuorescence matrix and PARAFAC model, and the potential application in water quality monitoring

Taihu Lake is one of the five biggest lakes in China. Surface water samples from 26 sampling sites of Taihu Lake were collected. Furthermore wet chemical analysis （CODCr and BOD5） and measurement of three dimensional excitation-emission matrix （3DEEM） spectra in the laboratory have been conducted. Using parallel factor analysis （PARAFAC） model, three components of colored dissolved organic matter （CDOM） have been identified successfully, based on the analysis of 3DEEM data. The characteristics of the three components also have been described by comparing them to some components of CDOM, identified in earlier researches. Meanwhile, spatial variations of concentration for the three components in Taihu Lake have been analyzed, and the result indicates that the concentration of component 1 depends more on the situation of wastewater pollution and can be used as the indicator of wastewater pollution. The relationship between the concentrations of the three components and results of the wet chemical analysis show that none of the three components can be used as indicators of gross organic matter in water. However, the concentrations of all the three components have obvious linear relationships with the BOD5 value, especially for component 1 （r = 0.72878）. Finally, the potential applications of the composition analysis based on 3DEEM and PARAFAC model in water quality monitoring have been illuminated.

DYNAMIC VARIATIONS OF WATER QUALITY IN TAIHU LAKE AND MULTIVARIATE ANALYSIS OF ITS INFLUENTIAL FACTORS

Dynamic variation of water quality in Meiliang Bay and part of West Taihu Lake has been analysed based on data from 1991 to 1992. Principal Component Analysis is used to reveal the mutual relationships of various factors. It is shown that there existis an obvious spatial and temporal variation in the main factors of water quality. Annual values of TP, CON, TN, Chl-a and conductivity decrease evidently from inner Meiliang Bay to the outer from north to south. TP and TN fluctuate seasonally with much higher value in winter. This is particularly true for the mouth of Liangxi River. In addition, the Chl-1 has a synchronous variation with water temperature, although being lagged a little, and closely relates to TP and TN. Finally, the results from Principal Component Analysis show that TP, TN, SS (or SD), water temperature and Chl-a are the most influential factors to water qualuty in this area, and both suspensions and algae can contribute to transparency to Taihu Lake.

Water quality, nutrient budget, and pollutant loads in Chinese mitten crab (Eriocheir sinensis) farms around East Taihu Lake

To understand the factors causing frequent outbreaks of harmful algae blooms in the Taihu Lake, China, we studied water quality and nutrient budget in Chinese mitten crab (Eriocheir sinensis) farm ponds in the eastern part of the lake from November 2007 to December 2009. We estimated the nitrogen (N), phosphorus (P), and chemical oxygen demand (COD) loads. Materials input and output ponds, water exchange, and applied management practices of 838.5-hm2 crab ponds were surveyed using questionnaires. Water quality of 12 ponds, which were located no more than 2 km from East Taihu Lake, were monitored. The results show that water quality in the crab ponds was better than reference data. Feeds, including corn seed, commercial feed, trash fish, and gastropod, were the major sources of N and P input in the crab ponds, contributing 88.7% and 94.9%, respectively. In total, 60.5% of N and 37.3% of P were sequestered by macrophytes, and only 15.7% and 8.5% of them were discharged as effluent. The net loads of N and P in effluent were 16.43 kg/hm2/cycle and 2.16 kg/hm2/cycle, respectively, while the COD load was -17.88 kg/hm2/cycle. This indicated that crab farming caused minor negative impact on the trophic status of the lake area, which was attenuated by macrophytes. However, wastewater purification is still necessary in crab faming.

DYNAMIC VARIATIONS OF WATER QUALITY IN TAIHU LAKE AND MULTIVARIATE ANALYSIS OF ITS INFLUENTIAL FACTORS

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Study on the water quality of the Taihu Lake using genotoxicological methods

The micronucleus(MCN) test of Vicia faba root tip cell was used to screen the water quality of the Taihu Lake. The MCN ‰ and the pollution index ( PI ) were examined and the F test was carried out to evaluate the statistical difference in mean MCN ‰ among various samples. There were significant difference among thirty nine samples and there were six sites whose PI values are above 2. The authors suggest that the Taihu Lake has partly been polluted to different degrees and the whole water body can be divided into three types. Ames tests were then conducted to detect mutagenicity at five significant sites. The results showed that rivers flowing through urban area carried large amount of mutagenic pollutants into the lake and these pollutants contaminated the source of main waterworks.

Analysis of black water aggregation in Taihu Lake

Black water aggregation （BWA） in Taihu Lake is a disaster for the lake environment. It is a phenomenon resulting from water environmental deterioration and eutrophication caused by accumulation of pollutants in the lake, according to research on the water quality, pollutants of BWA, and occurrence mechanisms of BWA. Dead algae are the material base of BWA, the polluted sediment is an important factor for the formation of BWA, and hydrological and meteorological conditions such as sun light, air temperature, wind speed, and water flow are the other factors that may lead to the formation of BWA. Thioether substances such as dimethyl trisulfide are the representative pollutants of BWA. Parameters such as chlorophyll-a, DO, pH, and water temperature are sensitive indicators of BWA. Measures such as algae collection, ecological dredging, pollution control, and water diversion from the Yangtze River to the lake, are effective, and strengthening aeration is an emergency measure to control BWA.

Spectral Geometric Triangle Properties of Chlorophyll-A Inversion in Taihu Lake Based on TM Data

The main objective of this study was to develop and validate the applicability of the Area Chlorophyll-a Concentration Retrieved Model (ACCRM), Height Chlorophyll-a Concentration Retrieved Model (HCCRM), Angle Chlorophyll-a Concentration Retrieved Model (AgCCRM), and Ratio Model of TM2/TM3 (RM) in estimating the chlorophyll-a concentration in Case II water bodies, such as Taihu Lake in Jiangsu Province, China. Water samples were collected from 23 stations on the 27th and 28th of October, 2003. The four empirical models were calibrated against the calibration dataset (samples from 19 stations) and validated using the validation dataset (samples from 4 stations). The regression analysis showed higher correlation coefficients for the ACCRM and the HCCRM than for the AgCCRM and the Ratio Model;and the HCCRM was slightly superior to the ACCRM. The performance of the ACCRM and the HCCRM was validated, and the ACCRM underestimated concentration values more than the HCCRM. The distribution of chlorophyll-a concentrations in Taihu Lake on October 27, 2003 was estimated based on the Landsat/TM data using the ACCRM and the HCCRM. Both models indicated higher chlorophyll-a concentrations in the east, north and center of the lake, but lower concentrations in the south. The accuracy of results obtained from the HCCRM and the ACCRM were also supported by the validation dataset. The study revealed that the HCCRM and the ACCRM had the best potential for accurately assessing the chlorophyll-a concentration in the highly turbid water bodies.

Human health ambient water quality criteria for 13 heavy metals and health risk assessment in Taihu Lake

Heavy metals are widely concerning because of their toxicity,persistence,non-degradation and bioaccumulation ability.Iluman health ambient water quality criteria(AWQC)are specific levels of chemicals that can occur in water without harming human health.At present,most countries do not consider the effects of aquatic vegetables in deriving human health AWQC.Therefore,the intake of aquatic vegetables(Brasenia schreberi)was added to the derivation of human health AWQC and a health risk assessment for 13 heavy metals in Taihu Lake.The human health AWQC(consumption of water,fish and aquatic vegetables)values of 13 heavy metals ranged from 0.04(Cd)to 710.87μg/L(Sn),and the intake of B.schreberi had a very significant effect on the human health AWQC for Cu,with a more than 62-fold difference.The hazard quotients of As(2.8),Cd(1.6),Cr(1.4)and Cu(4.86)were higher than the safe level(HQ=1),indicating that As,Cd,Cr and Cu in Taihu Lake posed a significant health risk.Sensitivity analysis showed that the contribution rate of B.schreberi intake to the human health risk from Cu was 91.6%,and all results indicated that the risk of Cu in B.schreberi to human health should be of particular concern.This study adds the consideration of aquatic vegetable consumption to the traditional method of human health AWQC derivation and risk assessments for the first time,and this approach can promote the development of risk assessments and water quality criteria.

江苏苏州太湖三山岛国家湿地公园水质监测与分析

对江苏苏州太湖三山岛国家湿地公园2019—2021年这3年间的水体水质进行了监测,并分析了公园内植物应用现状以及植物对水质的影响。结果表明:pH值指标变化幅度较小,且一直维持在国家地表水规定的范围内;溶解氧含量一直处于Ⅰ类水环境质量标准;总氮含量略有变化,维持在Ⅱ类水环境质量标准;化学需氧量逐年增长;总磷、氨氮的含量变化趋势相似,均呈现先增加后降低的趋势。区域内植物群落丰富,垂柳、芦苇、睡莲、香蒲等植物交错分布,对水体的净化能力强。当前,应加强湿地内居民环保意识,实施正确的湿地生态保护措施,以期更好地保护该地区的生物多样性。

太湖北部湖滨带芦苇湿地夏季水质时空变化特征分析

为了解太湖北部湖滨带芦苇湿地夏季水质时空变化,于2022年6—9月,在芦苇湿地时空分布调查的基础上,分别采集典型湖滨带芦苇湿地表层水体样品,测定pH、总氮(TN)、总磷(TP)、氨氮(NH+4-N)、高锰酸盐指数(COD Mn)、叶绿素a(Chl-a)等水质理化指标,并对湿地水质时空变化特征和水体富营养化状态进行分析。结果表明,所调查的7片芦苇湿地中pH、溶解氧(DO)、电导率(EC)、水温(WT)月间变化差异均极显著(p<0.01),COD Mn月间差异显著(p<0.05),但TN、TP、NH+4-N和Chl-a月间变化无显著差异(p>0.05)。所有水质理化指标在竺山湾、月亮湾、梅梁湾和贡湖湾芦苇湿地间均具有显著差异性(p<0.05)。湿地夏季水体基本呈中度或重度富营养化状态,时间上8月水质最差,地理位置上月亮湾最差。太湖北部湖滨带芦苇湿地水体属于磷限制型,限制磷元素的输入可有效控制湖滨带苇区水体富营养化的程度。

探析无锡某水厂取水头部水源各水质指标间的关系

原水水质直接关系到饮用水的安全,对原水水质的监测、预判和预警,可及时进行后续工艺调整,保障安全优质供水。文章统计分析了无锡某水厂取水头部原水各项水质指标的变化趋势,发现季节交替与望虞河引水会影响原水水质指标的数值,其中,pH与藻密度和水温有一定的正相关关系;溶解氧与水温呈显著的负相关关系;藻类的生长繁殖(水体中藻类数量的变化)与水温、总氮、总磷密切相关,藻类数量与叶绿素之间总体上呈现线性正相关关系,且具有季节性特征;嗅味指标如2-甲基异莰醇(2-MIB)等与藻种类以及其密度关系较大,而浑浊度、高锰酸盐指数与氨之间无显著相关性。望虞河引水期间氯化物随着引水下降较显著;水中浑浊度、高锰酸盐指数、氨、亚硝酸盐等水质指标受引水略有波动,关联性暂不显著。

基于特征工程和NGO-LSTM的水质预测模型研究

由于水质数据特征复杂、关联度参差不齐而导致溶解氧浓度预测难度较大,为提高水质溶解氧浓度预测的准确性,提出了一种基于特征工程和北方苍鹰优化算法的长短期记忆网络(Feature Engineering-Northern Goshawk Optimization-Long Short Term Memory,FE-NGO-LSTM)混合模型。首先对水质数据集进行缺失值补齐、特征筛选与特征多项式构造,然后基于NGO-LSTM模型优化模型参数,提升预测性能;对不同多项式阶数下的特征预测效果进行分析之后,将该模型与基于灰狼优化算法、鲸鱼优化算法及粒子群优化算法的LSTM模型进行对比;最后,在太湖流域东苕溪城南监测断面对该模型进行了验证,计算FE-NGO-LSTM模型预见期为4,8,12,16,20,24 h的预测结果。试验结果显示:当多项式阶数为2阶时,模型预测效果最好,FE-NGO-LSTM模型相比基于其他优化算法的LSTM模型,平均绝对误差、均方误差、均方根误差分别至少降低9.0%,12.9%及6.3%,且随着预见期的增加,预测误差仍在可接受范围内,说明FE-NGO-LSTM模型在预测溶解氧浓度时具有一定优势与泛化性。

基于主成分分析法的梅梁湖水质分析与评价

选取2010-2015年7-9月梅梁湖区域6站点的悬浮物、溶解氧、pH值、硝酸盐氮、氨态氮、高锰酸盐指数、总磷和总氮等8个监测指标数据,采取主成分分析法分析了该区域的水质,明确影响该水域主要污染因子。结果表明:8项指标提取为3个主成分,解释了84.14%的水质信息。从空间分布上来看,靠近湖岸的湖区水质较差,在远离入湖河口,水域开阔处,水质较好。在时间上,梅梁湖区域水质状况不断得到改善,水质状况主要受入湖污染负荷和入湖水量的影响。梅梁湖区域富营养化污染严重,有机污染程度得到了一定的改善。研究结果对进一步了解梅梁湖区域水质情况具有重要意义,同时也为江苏省梅梁湖水质管理的科学决策提供支持。

提升太湖水质导向下的太湖水环境治理策略

太湖作为我国重要的淡水湖泊之一,近年来面临着严重的水质污染和生态系统退化问题。制定有效的治理策略对改善太湖水环境、保护湖泊生态系统具有重要意义。在治理中,首先需严格控制太湖流域的污染源,可分为农业污染、工业污染以及生活污染。在农业生产中推广科学施肥、合理用药等环保措施,降低农业面源污染;在工业方面,加强环保监管,推广清洁生产技术,减少工业废水排放;同时,应加强城乡生活污水处理设施的建设和运营,提高生活污水处理率。在治理过程中还需生态调水,促进生态修复,减轻太湖富营养化水平,提高水质安全性。另外,通过加强湖泊岸线的管理,可以防止过度开发以及非法侵占的状况发生。

基于Sentinel-2与随机森林算法的太湖水生植被分布监测

基于2018—2021年太湖地区哨兵2号(Sentinel-2)卫星遥感影像和随机森林算法,结合植被敏感指数,开展太湖水生植被分布监测,综合分析了水生植被的时空变化特征,初步揭示了太湖水生植被的动态变化。结果表明,太湖水生植被分布面积有逐年上升的趋势,且年间变化具有明显的单峰型特征,表现为春季沉寂,夏季快速增长,秋季达到暴发期,冬季面积开始减退;太湖水生植被主要分布于东太湖、东部沿岸和贡湖,类型以沉水植被为主,其中浮叶植被主要分布于东太湖,挺水植被主要分布于东太湖沿岸的浅水区域;沉水植被主要分布于东部沿岸和贡湖;水生植被主要分布的东太湖水域,其水质总体优于太湖其他水域。

考虑大气沉降的湖库分区动态水环境容量精细解析

针对面源污染为主的湖库型流域,为建立水质目标管理与污染总量控制之间更精准的响应关系,借鉴日最大负荷总量模式,基于物质量平衡原理提出考虑径流丰枯变化、不均匀混合、大气沉降等影响因素的湖库分区动态水环境容量精细解析方法,包括污染混合区设置、代表水文系列确定、逐日分区水量水质计算。以沙河水库为例,分别以全湖Ⅱ类、主湖Ⅱ类作为水质管理目标,采用2010—2015年代表水文系列对总氮动态水环境容量进行精细解析。结果表明:全湖Ⅱ类、主湖Ⅱ类水质管理目标下沙河水库总氮水环境容量的多年均值分别为36.7 t和99.43 t,若不考虑湖滨混合区,全湖Ⅱ类水质目标下总氮的年水环境容量计算值偏大66.43%;实施水质目标管理的水域面积越大,大气沉降对水环境容量的影响越大;径流年际及年内丰枯变化对水环境容量的影响显著;各分区总氮控制总量占全流域总量的比例与面积比基本一致。湖库分区动态水环境容量精细解析可量化不同因素对水环境容量计算结果的影响,科学解析面源输入型湖库水环境容量的时空结构特征,实现水质目标管理与污染总量分区管控的有机联动,更好地支撑流域水环境的精细化管理。

2020年太湖流域洪水及太湖总磷变化趋势分析

收集整理了2000—2020年太湖水量、总磷数据,对2020年太湖流域洪水以及其后太湖总磷的变化规律进行了分析,并与2016年洪水进行了比较。从洪水特征、出入湖磷通量、环湖河道磷质量浓度、太湖磷存量及组成等方面进行了研究,明确了2020年洪水对太湖总磷的影响。结果表明:2020年洪水并未造成太湖总磷污染的反弹,2020年后太湖总磷污染情况出现明显好转;与2016年洪水不同,2020年洪水并没有造成入湖磷通量的增加;2020年入湖总磷质量浓度较2007年以来的平均值下降了21.5%,这是入湖磷通量未增加的主要原因。

太湖丰水期到枯水期水质动态变化及综合分析

湖泊水质和生态体系关乎当地经济和社会发展。近几十年以来,太湖水质不断恶化,为了解太湖湖体水环境现状,为其后续治理提供理论指导,选取2021年第19—53周(2021年5月3日—2022年1月2日)湖心监测站pH、溶解氧、高锰酸钾指数、氨氮、总磷的自动监测数据,分析其时间变化特征,并进行水质指标间的相关性分析、水质评价和主成分分析。研究表明:丰水期DO、COD_(Mn)、TP均低于枯水期,NH_(3)-N高于枯水期;丰水期和枯水期的COD_(Mn)与DO都呈现负相关,TP与DO、COD_(Mn)与TP总体上呈现正相关,NH_(3)-N与DO在丰水期呈现正相关、枯水期呈现负相关;太湖的主要污染物是TP,受其影响,丰水期、枯水期均为Ⅳ类水质;周边城市工业废水的排放是太湖污染的主要影响因子,其贡献率达到37.3%,其次,农业化肥的施用和水产养殖也是影响太湖水质的主要因子。该结论对太湖水环境治理具有一定的参考意义。

基于水量与水质的太湖流域水生态服务供需关系及多情景评估

耦合水量供给与水质净化的水生态服务供需关系的多尺度空间量化评估,有助于刻画和识别丰水区水质性缺水问题,并丰富水生态服务研究。在构建水量供给和水质净化服务供需评估方法的基础上,利用空间分析方法在现状情景基础上分别设置提升用水效率、改善土地管理方式和优化土地利用空间配置三种优化情景,并在栅格、子流域和县域三个尺度上开展基于水量供给和水质净化的水生态服务供需关系的定量评估,分别探讨了不同情景不同尺度下的水生态服务供需变化、空间响应及其机制特征。研究结果表明:(1)太湖流域的水量供需状况显著优于水质供需状况,节水能够有效改善流域内的水量赤字,而减量施肥和优化土地利用配置能够显著改善流域内的水质赤字。(2)多尺度的水量供给与水质净化服务供需解析,有助于精准识别不同尺度下亟需治理的关键区域。(3)水量赤字区主要集中在建设用地分布区域,耕地仍是引致水质赤字的主要原因,但随着尺度的逐渐增大,水质赤字区的建设用地面积也在不断增加。(4)优化土地利用结构方案是解决水质性缺水的最有效方法,但需要突破现有政策尤其是耕地保护政策的刚性约束,故耦合提升用水效率等方法是当前治理太湖流域“水质性缺水”问题首选措施。

2010~2020年太湖无锡水域水质时空变化及原因分析

分析太湖无锡水域水质时空变化对于区域富营养化控制、水污染防治有重要意义。基于2010~2020年太湖无锡水域逐月水质数据和入湖河流水质数据,采用综合污染指数和综合营养状态指数评估了湖区水质和富营养化状态的时空变化特征,分析了主要水质指标的年际年内变化规律和空间格局,探究了湖区水质与入湖河流污染物浓度及通量的相关性。结果表明,2010~2020年太湖无锡水域水质明显改善,全湖综合污染指数和综合营养状态指数分别下降了25%、10%。除总磷浓度无明显变化趋势外,湖区其余水质因子浓度均呈下降趋势。季节变化方面,高锰酸盐指数、总磷和叶绿素a浓度在夏秋季保持较高值,总氮和氨氮浓度则在冬春季保持较高值。空间上,营养盐浓度由西北部、北部湖区向东南部、东部湖区递减。2013~2020年入湖河流水质变化与湖区水质变化趋势基本一致,其中湖区总氮和氨氮浓度分别与入湖河流总氮浓度和氨氮入湖通量呈显著正相关关系,空间格局响应基本一致,入湖河流的外源输入是影响湖区水质时空变化的重要因素。