An Optimal Algorithm for the Retrieval of Chlorophyll,Suspended Sediments and Gelbstoff of Case Ⅱ Waters in the Pearl River Estuary

An optimal algorithm for the retrieval of chlorophyll, suspended sediments and gelbstoff of case Ⅱ waters in the Pearl River estuary was established with the optical parameters derived from the in-situ data obtained in Jan. 2003 in the same area. And then, the chlorophyll, suspended sediments and gelbstoff of the SeaWiFS pixels on Jan. 29, 2003 corresponding to the in-situ sites of Jan. 25 and 26, 2003 were synchronously retrieved, with average relative errors of 14.9%, 12.1% and 13.6% for chlorophyll, suspended sediments and gelbstoff, respectively. The research results indicated that the optimal retrieval algorithm established here was relatively fit for the retrieval of the chlorophyll, suspended sediments and gelbstoff of case Ⅱ waters in the Pearl River estuary, and had quite good retrieval accuracy.

Monitoring and Evaluation of Environmental Quality of the Waters near the Oujiang River Estuary in Wenzou

Based on the monitoring results of environmental quality of the waters near the Oujiang River estuary from 2010 to 2017,the present situation of environmental quality of the waters was analyzed and evaluated.The results showed that pH,DO,COD Mn ,petroleum,and heavy metal (Cu,Pb,Zn,Cd,Hg,As and Cr) content in the waters near the Oujiang River estuary did not exceed the second-class standard of Seawater Quality Standard (GB 3097-1997),while both inorganic nitrogen and reactive phosphate in the waters greatly exceeded the second-class standard.The water quality near the Oujiang River estuary was in an eutrophic state.In terms of sediment quality,the standard index of most evaluation factors except for Cu was smaller than 1,meeting the demands of sediment quality for environmental protection.

Monitoring and Evaluation of Environmental Quality of the Waters near the Feiyun River Estuary in Wenzou in Recent Years

Based on the monitoring results of environmental quality of the waters near the Feiyun River estuary during 2011-2016, the current situation of environmental quality of the waters was analyzed and evaluated. The results showed that pH, DO, COD Mn , petroleum, and heavy metals (Cu, Pb, Zn, Cd, Hg, As and Cr) in the waters near the Feiyun River estuary did not exceed the second-class standard of Seawater Quality Standard (GB 3097-1997), while both inorganic nitrogen and reactive phosphate in the waters exceeded the second-class standard obviously. The water quality of the waters near the Feiyun River estuary was in an eutrophic state. In terms of sediment quality, the standard index of most evaluation factors except for Cu was smaller than 1, meeting the demands of sediment quality for environmental protection.

Estimation of Peak Water Level in Pearl River Estuary under the Background of Sea Level Rise

[Objective] The study aimed to predict the peak water level in Pearl River Estuary under the background of sea level rise. [Method] The changing trends of peak water level at Denglongshan station and Hengmen station were analyzed firstly on the basis of regression models, and then sea level rise in Pearl River Estuary in 2050 was predicted to estimate the 1-in-50-year peak water level in the same year. [Result] Regression analyses showed that the increasing rate of peak water level over past years was 6.3 mm/a at Denglongshan station and 5.8 mm/a at Hengmen station. In addition, if sea level will rise by 20, 30 and 60 cm respectively in 2050, it was predicted that the 1-in-50-year peak water level will reach 3.04, 3.14 and 3.44 m at Denglongshan station, and 3.19, 3.29 and 3.59 m at Hengmen station separately. [Conclusion] The estimation of peak water level in Pearl River Estuary could provide theoretical references for water resources planning.

The Derivation of Nutrient Criteria for the Adjacent Waters of Yellow River Estuary in China

Ecological protection and high-quality development of the Yellow River basin are becoming part of the national strategy in recent years.The Yellow River Estuary has been seriously affected by human activities.Especially,it has been severely polluted by the nitrogen and phosphorus from land sources,which have caused serious eutrophication and harmful algal blooms.Nutrient criteria,however,was not developed for the Yellow River Estuary,which hindered nutrient management measures and eutrophication risk assessment in this key ecological function zone of China.Based on field data during 2004-2019,we adopted the frequency distribution method,correlation analysis,Linear Regression Model(LRM),Classification and Regression Tree(CART)and Nonparametric Changepoint Analysis(nCPA)methods to establish the nutrient criteria for the adjacent waters of Yellow River Estuary.The water quality criteria of dissolved inorganic nitrogen(DIN)and soluble reactive phosphorus(SRP)are recommended as 244.0μg L^(−1) and 22.4μg L^(−1),respectively.It is hoped that the results will provide scientific basis for the formulation of nutrient standards in this important estuary of China.

Water Quality Evaluation in Tidal River Reaches of Liaohe River Estuary, China Using a Revised QUAL2K Model

Rivers in the Liaohe River Estuary area have been seriously polluted by discharges of wastewater containing petroleum pol- lutants and nutrients. In this paper, The Enhanced Stream Water Quality Model （QUAL2K） and its revised model as well as One-dimensional Tide Mean Model （1D model） were applied to predict and assess the water quality of the tidal fiver reach of the Liaohe River Estuary. Dissolved oxygen （DO）, biochemical oxygen demand （BODs）, ammonia nitrogen （NH3-N） and total phosphorus （TP） were chosen as water quality indices in the two model simulations. The modelled results show that the major reasons for degraded rivers remain petroleum and non-point source pollution. Tidal water also has a critical effect on the variation of water quality. The sensitivity analysis identifies that flow rate, point load and diffuse load are the most sensitive parameters for the four water quality indices in the revised QUAL2K simulation. Uncertainty analysis based on a Monte Carlo simulation gives the probability distribution of the four wa- ter quality indices at two locations （6.50 km and 44.84 km from the river mouth）. The statistical outcomes indicate that the observed data fall within the 90% confidence intervals at all sites measured, and show that the revised QUAL2K gives better results in simulating the water quality of a tidal fiver.

Three-Dimensional Water Quality Model Based on FVCOM for Total Load Control Management in Guan River Estuary,Northern Jiangsu Province

Guan River Estuary and adjacent coastal area(GREC) suffer from serious pollution and eutrophicational problems over the recent years.Thus,reducing the land-based load through the national pollutant total load control program and developing hydrodynamic and water quality models that can simulate the complex circulation and water quality kinetics within the system,including longitudinal and lateral variations in nutrient and COD concentrations,is a matter of urgency.In this study,a three-dimensional,hydrodynamic,water quality model was developed in GREC,Northern Jiangsu Province.The complex three-dimensional hydrodynamics of GREC were modeled using the unstructured-grid,finite-volume,free-surface,primitive equation coastal ocean circulation model(FVCOM).The water quality model was adapted from the mesocosm nutrients dynamic model in the south Yellow Sea and considers eight compartments:dissolved inorganic nitrogen,soluble reactive phosphorus(SRP),phytoplankton,zooplankton,detritus,dissolved organic nitrogen(DON),dissolved organic phosphorus(DOP),and chemical oxygen demand.The hydrodynamic and water quality models were calibrated and confirmed for 2012 and 2013.A comparison of the model simulations with extensive dataset shows that the models accurately simulate the longitudinal distribution of the hydrodynamics and water quality.The model can be used for total load control management to improve water quality in this area.

Optimization of Shanghai Marine Environmental Monitoring Sites in the Identification of Boundaries of Different Water Quality Grades

Water quality is critical to ensure that marine resources and the environment are utilized in a sustainable manner. The objective of this study is therefore to investigate the optimum placement of marine environmental monitoring sites to monitor water quality in Shanghai, China. To improve the mapping or estimation accuracy of the areas with different water quality grades, the monitoring sites were fixed in transition bands between areas of different grades rather than in other positions. Following bidirectional optimization method, first, 18 candidate sites were selected by filtering out specific site categories. Second, three of these were, in turn, eliminated because of the rule defined by the changes in the areas of water quality grades and by the standard deviation of the interpolation errors of dissolved inorganic nitrogen(DIN) and phosphate(PO_4-P). Furthermore, indicator kriging was employed to depict the transition bands between different water quality grades whenever new sampling sites were added. The four optimization projects of the newly added sites reveal that, all optimized sites were distributed in the transition bands of different water grades, and at the same time in the areas where the historical sites were sparsely distributed. New sites were also found in the overlap region of different transition bands. Additional sites were especially required in these regions to discriminate the boundaries of different water quality grades. Using the bidirectional optimization method of the monitoring sites, the boundaries of different water quality grades could be determined with a higher precision. As a result, the interpolation errors of DIN and PO_4-P could theoretically decrease.

Contamination by Organochlorine Pesticides in the Estuaries of Southeast China

Persistent organic pollutants(POPs) such as organochlorine pesticides are of global concern due to their widespread occurrence and persistence. This paper reports recent research studying the distribution and fate of organochlorine pesticides in the Jiulong River, the Minjiang River and the Pearl River estuaries in Southeast China. Eighteen organochlorine pesticides were extracted from water, pore water and sediment samples, followed by analysis by GC ECD. The results showed that the contamination levels were similar in these three estuaries. The levels of the total organochlorine pesticides in porewater were significantly higher than those in surface water, due to the high affinity of these hydrophobic compounds for sediment phase. Among the hexachlorocyclohexane(HCH) compounds, β HCH was found to be the most important isomer. The analysis of 1,1,1 trichloro 2,2 bis chlorophenyl ethane(DDT) and its metabolites showed that 1,1 dichloro 2[ o chlorophenyl] 2[ p chlorophenyl] ethylene(DDE) was dominant in the group.

Design of environmental decision support system and its application to water quality management

EDSS is a comprehensive software system for water quality management in tidal river networks in general and for the Pearl River Delta in particular. Its purpose is to provide a practical tool that could assist government agencies in decision making for the efficient management of water resources in terms of both quantity and quality. By combining the capabilities of geographical information system (GIS), database management system (DBMS), model base management system (MBMS) and expert system, the aim is to improve the quality of decision making in what is becoming an increasingly complex area. This paper first outlines the basic concepts and philosophy adopted in developing EDSS, the system architecture, design features, implementation techniques and facilities provided. Thereafter, the core part of the system—the hydrodynamic and water quality models are described briefly. The final contribution in this paper describes the application of EDSS to the Pearl River Delta, which has the most complicated tidal river network patterns as well as the fastest economic development in the world. Examples are given of the real-world problems that can be addressed using the system, including cross-boundary water pollution analysis, regional drinking water take-up site selection, screening of important polluters, environmental impact assessment, and water quality zoning and planning. It is illustrated that EDSS can provide efficient and scientific analytical tools for planning and decision-making purposes in the information era.

Spatial assessment of water quality using chemometrics in the Pearl River Estuary, China

A cruise was commissioned in the summer of 2009 to evaluate water quality in the Pearl River Estuary （PRE）. Chemometrics such as Principal Component Analysis （PCA）, Cluster analysis （CA） and Self-Organiz- ing Map （SOM） were employed to identify anthropogenic and natural influences on estuary water quality. The scores of stations in the surface layer in the first principal component （PC1） were related to NH4-N, PO4-P, NO2-N, NO3-N, TP, and Chlorophyll a while salinity, turbidity, and SiO3-Si in the second principal component （PC2）. Similarly, the scores of stations in the bottom layers in PC1 were related to PO4-P, NO2-N, NO3-N, and TP, while salinity, Chlorophyll a, NH4-N, and SiO3-Si in PC2. Results of the PCA identified the spatial distribution of the surface and bottom water quality, namely the Guangzhou urban reach, Middle reach, and Lower reach of the estuary. Both cluster analysis and PCA produced the similar results. Self-organizing map delineated the Guangzhou urban reach of the Pearl River that was mainly influenced by human activities. The middle and lower reaches of the PRE were mainly influenced by the waters in the South China Sea. The information extracted by PCA, CA, and SOM would be very useful to regional agencies in developing a strategy to carry out scientific plans for resource use based on marine system functions.

Spatial and Seasonal Variations of Nutrients in Sediment Profiles and Their Sediment-Water Fluxes in the Pearl River Estuary,Southern China

Three cruises were launched in the Pearl River Estuary （PRE） in 2005 to investigate the biogeochemical cycling of nutrients associated with early diagenesis related to degradation of organic matter. Seasonal and spatial variations of pore water nutrient concentrations and profile patterns in sediments were studied. Nutrient fluxes at the sediment-water interface （SWI） were measured by incu- bation experiments, and we here discussed the accumulation and transformation processes of nutrients at the SWI. The nutrients generally decreased from the Pearl River outlets downstream, indicating an- thropogenic influences on the nutrient inputs in the estuary. NO3-N concentration was the highest of the three forms of DIN （dissolved inorganic nitrogen, the sum of NH4-N, NO3-N and NO2-N） in the overly- ing water, and NH4-N was the main component of DIN in pore water. The gradual increase of NH4-N and the rapid decrease of NO3-N with sediment depth provided the evidence for anaerobic conditions below the SWI. Negative fluxes of NO3-N and positive fluxes of NH4-N were commonly observed, sug- gesting the denitrification of NO3-N at the SWL The DIN flux direction suggested that the sediment was the sink of DIN in spring, however, the sediment was generally the source of DIN in summer and winter. PO4-P distribution patterns were distinct while SiO4-Si inconspicuously varied in sediment profiles in different seasons. The flux results indicated that PO4-P mainly diffused from the water column to the sediment while SiO4-Si mainly diffused from the sediment to the water column. Generally, the incu- bated fluxes were the coupling of diffusion, bioturbation and biochemical reactions, and were relatively accurate in this study.

Water quality model with multiform of N/P transport and transformation in the Yangtze River Estuary

As the Yangtze River Estuary and adjacent sea have been classified as a problem area with regard to eutrophication, it is important to explore the spatial and temporal variations of nitrogen and phosphorus （N/P） nutrients in this area. Based on danish hydraulic institute （DHI）＇s open platform Ecolab, a hydrodynamic and water quality model was developed for the Yangtze River Estuary, in which the transport and transformation processes of different forms of N/P nutrients were considered. Validations against measured data show that the model is overall reliable. Preliminary application of the model suggests that the model can simulate the characteristics of high phosphorus concentration area in the Yangtze River Estuary, and the high concentration area is closely related to the resuspension process of particulate phosphorus.

Spatial variations of river water quality in Pearl River Delta, China

In Pearl River Delta （PRD）, river water quality has deteriorated gradually due to population increase and ongoing industrialization and urbanization. In this study, multivariate statistic methods were used to assess water quality spatial pattern and to identify characteristics of water quality variation in the PRD. Water quality monitoring of the PRD during the year 2005 and 2008 was conducted at 25 different stations. Seventeen water quality parameters were analyzed for further studying. Results of one-way analysis of variance （ANOVA） indicated that all the parameters except air temperature, water temperature and zinc showed significant difference among monitoring stations in both dry and wet season. Monitoring stations in the PRD were separately classified into three statistically significant clusters at （Olink/Omax） （ 2 in dry and wet season, respectively. The three clusters indicated the similarity and dissimilarity of river water quality among 25 monitoring stations, corresponding to heavy pollution, moderate pollution and slight pollution. Thus, the results of this study are useful to evaluate water quality and manage water resources in the PRD.

Quantifying water quality and flow in multi-branched urban estuaries for a rainfall event with mass balance method

In this study,field observations were conducted after a heavy rainfall event in the Sumida and Shakujii rivers in Tokyo,Japan.The flow dynamics and fluxes of salt,suspended sediment(SS),and dissolved oxygen(DO)were investigated with the mass balance method.The fractions of fresh water and saltwater in seaward and landward flows were separated.The maximum salt flux in the Shakujii River was 53.8 kg/s during the flood tide,and those in the Sumida River were 680.3 kg/s at the upstream station and 703.7 kg/s at the downstream station.The trends of SS and DO fluxes were similar in both rivers.In the Shakujii River,the highest SS(3.1 kg/s)and DO(0.4 kg/s)fluxes appeared during the flood tide after rainfall.In the Sumida River,the maximum SS fluxes(6.1 and 6.3 kg/s at the upstream and downstream stations,respectively)and DO fluxes(1.15 and 1.21 kg/s at the upstream and downstream stations,respectively)appeared during the ebb tide.The mass balance method was used to estimate discharge,salinity,SS concentration,and DO concentration at a station with missing data.The results show that the estimated salinity and SS concentration had a significant correlation with the on-site observations,with correlation coefficients(R)of 0.950 and 0.835,respectively,but not for DO concentration(R?0.638).The disparity between the computed and measured data may be explained by the differences in velocity,salinity,topography,sedimentation,and the presence of organic matter.The analysis based on the advective salt transport components found a lower salt flux per unit width in the Shakujii River(0.36 kg/(m·s))in comparison with that in the Sumida River(2.88 kg/(m·s)).This indicates a higher probability for salt retention in the Shakujii River.©2020 Hohai University.Production and hosting by Elsevier B.V.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

PRELIMINARY RESEARCH ON WATER EXCHANGE AT THE PEARL RIVER ESTUARIES

To meet the needs of many parameters, simpler mathematical models of the seawater mixing and exchanging at estuaries are established in this note for studying the complicated Pearl River estuary. Calculations and discussions are made according to the investigation information obtained in March 1987.

长江口鱼类群落粒径结构特征及群落稳定性评估

为了解长江口鱼类群落粒径结构特征及群落稳定性状态,实验基于2018年长江口四季鱼类资源与环境调查数据,利用标准化粒径谱、群落稳定性评估模型对鱼类群落特征进行了探究,并利用营养指数法对长江口水体生态环境质量状况进行了综合评价。结果显示:①长江口鱼类粒级主要分布在−2~6范围内,曲线穹顶位于0~3粒级范围,鱼类群落以小型鱼类为主,整体处于受干扰状态;②北支和南支的鱼类群落存在季节变化,北支粒径谱曲率夏季最大(–0.04),秋季最小(–0.41),生物量与数量相对关系统计量W值为–0.11~0.12;南支粒径谱曲率夏季最大(–0.04),冬季最小(–0.24),W值为–0.03~0.37;③南支鱼类群落稳定性系数均值为0.57,北支均值为0.43,4个季节南支与北支鱼类群落稳定性程度不同。水质营养指数表明,北支富营养化程度(18.89)较南支(5.43)高,且富营养化指数和群落稳定性系数呈显著负相关,水体富营养化或对长江口鱼类群落系统偏离稳定状态有重要影响。研究表明,长江口鱼类群落粒径偏小,鱼类群落稳定性不高,水质呈富营养化状态。本研究探究了全面禁捕前长江口鱼类粒径结构特征并评估了鱼类群落稳定性,为长江口禁渔效果评价提供了前期研究依据。

珠江三角洲典型水产养殖区浅层地下水碘化物分布、来源及健康风险评估

为了解珠江三角洲典型水产养殖区浅层地下水中碘化物的来源以及存在的饮用健康风险,本研究综合运用数理统计分析、主成分分析、水质评价和健康风险评估等方法对珠江三角洲典型淡水养殖区域内鱼塘、污水处理池、居民饮用井三种类型水源共21个代表性样品进行分析。结果表明:研究区浅层地下水水化学类型以Ca^(2+)·HCO_(3)^(-)型为主,ρ(I^(-))介于2~343μg/L之间,其中33.3%的监测点位为高碘型水源,集中分布于研究区西部;浅层地下水中的碘易赋存于弱碱性还原环境中,而鱼塘泥沙中的富碘有机质的分解渗透作用可能会加重地下水的碘富集;城镇化进程中产生的还原性废水和垃圾渗滤液伴随着富含碳酸盐岩体中有机质的分解,都可能成为浅层高碘地下水的重要来源;研究区地表水(鱼塘水、污水处理池水)中Ⅳ类水占比为16.7%,处于较差类别,其中化学需氧量(COD_(Mn))与总氮(TN)为主要超标因子;浅层地下水质量类别最低为Ⅲ类水,整体水质较好,部分点位存在pH和ρ(I^(-))超标问题;成人的高碘饮用水健康风险较低,J4点位地下水源的儿童非致癌风险值大于1.0,建议加强对居民引用水井J4的ρ(I^(-))的常规监控,以保障儿童饮用水健康。

基于FVCOM的夏季珠江冲淡水年际变化特征

珠江冲淡水对南海北部的物理、化学以及生物特性具有十分重要的意义。本文以1993至2012年连续20年的FVCOM(The Finite Volume Community Ocean Model)模型后报模拟数据为基础,将海表盐度32等值线与岸线所围面积定义为珠江冲淡水的扩展范围,对珠江冲淡水在夏季(6月、7月和8月)的年际变化特征进行研究,并分析了南海季风和珠江径流量等因素对珠江冲淡水的影响。在西南风和较大的珠江径流量的作用下,夏季是珠江冲淡水同时向粤西和粤东两侧扩展的唯一季节,冲淡水扩展范围最大,且夏季珠江冲淡水的扩展形态和扩展面积具有明显的年际变化特征,1994年的东风异常极大增强了冲淡水的西向扩展。通过对2008年台风“风神”的分析,发现热带气旋引起的表层对流和垂向混合对珠江冲淡水具有明显的作用,但是由于其持续时间较短,对年际变化的影响并不显著。1998年夏季的强厄尔尼诺事件导致6月、7月和8月均出现了西南风异常,强西南风阻碍了冲淡水的西向扩展,促进了区域的上升流和表层流。

珠三角重要水库型饮用水源地土地利用变化对水质的联动影响

文章以珠三角地区大中型水库水源地作为重点研究区,探讨珠三角水库饮用水源地土地利用变化对水库水质影响的贡献和趋势,分析了珠三角地区水库型水源地近40年(1980—2020年)的土地利用变化,基于灰色关联分析辨识区域尺度上土地利用变化特征与水质等级的影响关系,然后选取珠澳供水系统中的大镜山水库为典型区,结合冗余分析及相关分析法,探讨流域尺度近20年的土地利用与水库水质指标变化作用关系,结果表明:1)研究区土地利用主要变化为建设用地及水域面积扩张,水田、旱地、林地面积减少。土地利用转移趋势主要为林地及耕地向生产生活用地转移,随着政策实施,上述土地利用转化过程有所放缓。2)区域上看,研究区非点源污染风险源虽逐渐减少,但至2020年仍占总土地利用的9.48%,土地利用格局调整和管理措施提升仍有一定空间。土地利用变化与水质存在明显相关性,根据相关性的强弱排序为:建设用地>农用地>林地,土地利用造成的面源污染仍是重要影响因素。3)大镜山水库水质存在多个月份总氮超标现象严重,氮磷污染逐渐上升,总氮和总磷为当前大镜山水体的主要污染物。大镜山水库各土地利用类型与水质指标呈现相关性,林地与氮磷水质指标整体呈显著负相关,建设用地、农用地呈显著正相关,同时调水对水库TN浓度具有正向影响。虽然不同流域的水质影响因素有变化,但流域土地利用格局配置对非点源污染的影响仍是不受控的因素之一,需进一步加强对其作用机制的认识,后续可通过模型模拟来研究供水水质影响机制,通过优化土地利用结构提升其水质净化生态服务功能,进而改善水库水质。