Wangyu River Research Articles

Field study on endogenous perfluoroalkyl acid release and their spatiotemporal distribution processes induced by inland navigation

Dense populations and industries in regions with developed inland waterways have caused the significant discharge of perfluoroalkyl acids (PFAAs) into surrounding waterways. Despite being the dominant energy input in the waterways, the impact of ship navigation on endogenous PFAA release is unclear. In this study, a field experiment was carried out in the Wangyu River (Taihu Basin, China) to investigate the spatiotemporal distribution processes of PFAAs in the water column after passage of ships with different tonnages, speeds, and draughts. The results showed that the PFAA contents did not decrease continuously with time but increased with a lag after the passing ship triggered a transient massive dissolution of PFAAs into the overlying water. In addition, PFAA contents in suspended particulate matter (SPM) exhibited a fluctuating downward trends after their peak at the moment of ship passage. Vertically, the PFAA concentrations among the layers of overlying water were relatively homogeneous, whereas SPM exhibited substantial heterogeneity in its distribution and adsorption of PFAAs. Moreover, the differences in jet scouring velocity (u), disturbance duration (t), and draught (h) of ships resulted in large variability in PFAA contents in the water column. Variance partitioning analysis further quantified the effects of u, t, and h on total PFAAs in the water column, with individual contributions of 53 %, 12 %, and 6 %, respectively. Furthermore, the release of endogenous PFAAs induced by ship passage involved rapid and slow processes, the former determining the overall PFAA release and the latter affecting PFAA concentration recovery in the water column. The findings provide in-situ observational data on spatiotemporal variations of PFAAs in multiphase media following ship passage, enhancing our understanding of endogenous pollution in inland waterways.

Distribution characteristics and controlling factors of typical antibiotics and antibiotic resistance genes in river networks in western area of Wangyu River, China

Antibiotics and antibiotic resistance genes (ARGs) pose health risks in aquatic environments because of their persistence and mobility. River networks can provide a perfect opportunity for exploring the occurrence and enrichment of ARGs and antibiotics in freshwater environments. On this basis, the abundances of four types of antibiotics (sulfonamides, quinolones, tetracyclines, and macrolides) and 13 ARGs (sulІ, sulІІ, tetA, tetB, tetO, tetW, qnrA, qnrS, qnrD, ermB, ermF, ermC, and ereA) were measured in the river networks of the west bank of the Wangyu River in China. The spatial distribution and temporal variation of these antibiotics and ARGs were characterized, and their controlling factors were analyzed. All four types of antibiotics were detected with high frequencies between 41% and 100%. Quinolone antibiotics exhibited the highest average concentration (286.53 ng/L). The concentrations of quinolones, tetracyclines, and macrolides were significantly higher in the winter than in the summer, whereas the concentration of sulfonamides was higher in wet periods than in dry periods. Of the 13 ARGs, sulI was the most abundant (1.28 × 105 copies per milliliter), followed by sulII and tetO (5.41 × 104 and 4.45 × 104 copies per milliliter, respectively). The canonical correspondence analysis showed that environmental factors, including dissolved oxygen, water temperature, total nitrogen, pH, and total phosphorus, had significant effects on the abundance of ARGs. sulІ, sulІІ, tetA, and tetB were significantly correlated with 16S ribosomal RNA sequences, indicating that the bacterioplankton community might affect the distribution of ARGs. The correlation heat map analysis showed that the spread of ARGs was influenced by specific bacterial groups, such as Acidobacteria and Cyanobacteria, indicating that these bacterioplankton may be the hosts of environmental ARGs.

Nontargeted Identification and Temporal Trends of Per- and Polyfluoroalkyl Substances in a Fluorochemical Industrial Zone and Adjacent Taihu Lake.

Various per- and polyfluoroalkyl substances (PFASs) remain undiscovered and unexplored in the environment. The goals of this study were to discover new species of PFASs in effluent and surface waters from a fluorochemical industrial zone, and to assess their concentration, distribution, and temporal trends in the adjacent natural environment. In total, 83 emerging PFASs from 14 classes were identified, 22 of which were reported for the first time. Authentic standards were synthesized for 13 per- and polyfluoroalkyl ether carboxylic acids (PFECAs), thereby greatly expanding the scope of PFAS-targeted monitoring. The newly identified compounds accounted for 27%-95% of the total PFAS concentrations. Of note, a novel diether carboxylic acid, 2-[2-(trifluoromethoxy)hexafluoropropoxy]tetrafluoropropanoic acid (C7 HFPO-TA) was detected at an extremely high concentration in the fluorochemical zone effluent (447 000 ng/L) and at a median concentration in the fluorochemical zone surface water (670 ng/L), with detectable levels also found in the natural environment, that is, Wangyu River (23 ng/L) and Taihu Lake (5.6 ng/L). The distinct geographic distribution of C7 HFPO-TA suggests transport from the industrial point source to Taihu Lake via the Wangyu River. The concentration of C7 HFPO-TA in Taihu Lake, along with that of many other emerging PFASs, continued to grow in three sampling campaigns from 2016 to 2021. Considering the environmental persistence and toxicity of structurally similar PFECAs (e.g., HFPO-DA), studies on C7 HFPO-TA are urgently needed.

A modelling framework to track phosphorus sources of the drinking water intakes in a large eutrophic lake

Excess phosphorus (P) in freshwater lakes is a global challenge due to its potential cause of harmful algal blooms threating drinking water safety. However, quantifying the P sources for a specific site in a large lake is extremely challenging due to the complex interaction between internal and external P loading to surface water. To address this challenge, this study developed a modelling framework to track P sources of two drinking water intakes in a large shallow lake (Lake Taihu) in China. The framework proposed a new-developed index (PSCI, P source contribution index) to quantify the contributions of various P sources for the drinking water intakes. PSCI was derived by a three-dimensional hydrodynamic and water quality model that describes the complex processes of P sources, sinks and transportation in both horizontal and vertical directions within the lake. Application of the framework to these two drinking water intakes (Jinshu and Shangshan) achieved a surprising finding that internal P loading from sediment was a significant P source with a contribution as high as 47.1% and 30.4%, respectively. Central Lake Taihu had a large contribution of 49.5% and 68.3% for Jinshu and Shangshan, and inflow river (Wangyu River) had a contribution of < 5%. The high contribution of internal P loading was mainly due to the sediment P accumulation for years and large external P loading. Our study highlighted the important role of internal P loading affecting the P concentration of drinking water intake in a large eutrophic lake, and demonstrated the high value of the modelling framework in quantifying the P sources for a specific site (e.g., drinking water intake) in a lake.

Shift in the distribution and fate of perfluoroalkyl acids by sluice gates in the multi-environment media of rivers

The impact of sluice operations on the distribution and fate of perfluoroalkyl acids (PFAAs) remains poorly understood. In this study, the distribution of PFAAs was investigated in water, suspended particles, sediment, and pore water from the upstream and downstream sections of six sluice gates along the Wangyu River, China. The target PFAAs were widely distributed in the dissolved phase (∑PFAAs: 447.61 ± 180.26 ng/L), particle phase (∑PFAAs: 2040.95 ± 1870.88 ng/g dw), sedimentary phase (∑PFAAs: 39.42 ± 35.38 ng/g dw), and pore water phase (∑PFAAs: 8172.54 ± 4278.60 ng/L). Our data suggest predominant detections of short-chain PFAAs such as perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA) in the four environmental media. Sediment pore water appeared as an essential repository and potential source for PFAA re-release to the river environment. The levels of PFAAs in the dissolved and suspended particle phase upstream of the sluices were significantly lower than those downstream, while the situation in the sediment and pore water phase was the opposite. Sluice operation caused PFAA redistribution among the multi-environment media but did not change the PFAA composition, which had the significant effect on the partition behavior of perfluoroalkyl carboxylic acids (PFCAs) between particles and water, as well as changed the migration pattern of PFOA, PFNA and PFOS from equilibrium to the migration state. Quantitative prediction models were developed for simulating fate of PFAAs in gate-controlled river, and the major factors affecting the distribution and fate of PFAAs were identified. Our findings provide insights into the redistribution mechanisms of PFAAs and an understanding of their environmental fate.

Occurrence and transport of perfluoroalkyl acids (PFAAs) in a Yangtze River water diversion project during water diversion and flooding

Water diversion is increasingly utilized for water supply, flood control, irrigation, and water quality improvement in many water bodies globally. Our findings indicate that micropollutants such as perfluoroalkyl acids (PFAAs) can be transported via dual-source water diversion projects during water diversion and flood discharge, which may negatively impact both receiving water bodies. However, the sources, spatiotemporal variations, and fluxes of PFAAs under water diversion projects remain unclear. Here we report patterns of 18 PFAA compounds in the surface water at 14 sites of a dual-source water diversion project (Wangyu River) connecting the Yangtze River and Taihu Lake in China. We found multiple contamination hotspots with PFHxA and PFOA dominantly originating from industrial and domestic sources during water diversion from the Yangtze River to Taihu Lake. During the severe flooding in summer 2020, PFAA concentrations ranged from 82.0 to 114.0 ng L−1, while the concentrations and relative contributions of individual perfluoroalkane sulfonic acids (PFSAs) increased along the mainstream due to the tributaries’ contribution and high contamination level in the lake. Based on the spatiotemporal patterns of PFAA pollution, the flux of total PFAAs including both dissolved-phase and SS-phase into Taihu Lake was estimated as 26.6 kg in January 2020 as a reference value for water diversion. To our knowledge, this is the first report to describe the sources, occurrences, and transport of PFAAs in a dual-source water diversion project during water diversion and flooding. The results provide a novel perspective regarding the ecological safety of dual-source water diversion projects.

Quantification of pollutants in rainfall-runoff in plain areas with dense river networks: A case study in the Western Bank of Wangyu River, Taihu Basin

如何精细量化降雨径流污染负荷是流域尺度实现面源精准治污全过程控制的重要前提.本研究以水污染较为严重的望虞河西岸综合示范区为例，通过开展不同土地利用类型的降雨观测实验，修正SCS-CN模型中的初损率，并基于土地利用类型遥感解译和降雨径流污染物浓度测定，精细刻画降雨径流中总磷（TP）、总氮（TN）、氨氮（NH₃-N）、化学需氧量（COD）4类主要污染物的时空分布格局.结果表明：研究区绿地和农田、硬质地表的降雨初损率分别为0.3和0.9；径流深、污染负荷与降雨深之间存在显著的正相关性.随着降雨量逐年递减，研究区降雨径流中TP、TN、NH₃-N、COD四类污染物的负荷量分别从2017年的190、1359、445和16041 t减少至2019年的118、949、314和11250 t；单位面积TN和COD负荷最高的用地类型是农村住宅用地，草地的四种污染物单位面积负荷均最低，林地次之.相关研究结果为望虞河流域水污染控制提供了基础数据，也为定量测算平原河网区面源污染负荷提供了方法参考.;Quantifying the pollutant loads in rainfall-runoff plays a critical role in non-point water pollution control at the watershed level. In this study, rainfall-runoff experiments were conducted on various land use types in the western bank area of Wangyu River to localize the initial abstraction ratio in the SCS-CN model. Then, by incorporating the remote sensing interpretation of land use types and the measurement of pollutant concentration in the rainfall-runoff, this study explored the temporal and spatial patterns of four kinds of pollutants, namely total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH₃-N) and chemical oxygen demand (COD). The results indicate that the recommended initial abstraction ratios for grassland/forest/farmland and impervious surface in the study area are 0.3 and 0.9, respectively. Besides, the rainfall-runoff depths and pollutant loads are found to be significantly and positively correlated with the rainfall depths. Along with the decrease of annual rainfall in this region, the annual amount of TP, TN, NH₃-N and COD loads in rainfall-runoff have reduced from 190, 1359, 445 and 16041 t in 2017 to 118, 949, 314 and 11250 t in 2019, respectively. Rural resident land, among all the land use types, has the highest TN and COD loads per area, while grassland and forest rank the bottom. This study provides precise information about pollutants in rainfall-runoff to facilitate the development of water pollution control strategies in Wangyu River watershed and can be used as a methodological reference for future quantification of non-point source pollution practices in plain areas with dense river networks.

Study on pollution traceability based on the optimized hydrodynamic model of Tai Lake

Abstract This research optimized a hydrodynamic model based on in-situ measurement experiments, which can evaluate the transport process of pollution groups from inflowing lake sources with different wind conditions and their effects on the sensitive area in Tai Lake. The results showed that the wind drag coefficient (Cs) was 0.001–0.0028 when the wind speed was 1–12 m/s, and the particle trajectory is validated well by the methods of Thiessen polygon and Lagrange particle tracking, which proves that this hydrodynamic model was optimized successfully. During the water diversion period, the results showed that the Northwest Area and Gong Bay are the most important pollution flux sources to the sensitive area. Under northwest wind condition, the pollution flux proportion from Northwest Area and Gong Bay is 65 and 17%, respectively. Under southeast wind condition, the pollution flux proportion from Northwest Area and Gong Bay is 48 and 27%, respectively. Namely, pollution control to the upstream watershed of the Northwest Area and improving the water quality (TP &amp;lt; 0.065 mg/L; TN &amp;lt; 1.2 mg/L) from the Wangyu river are the effective methods to reduce the pollution risks for the sensitive area.

Dual-Source Optimization of the “Diverting Water from the Yangtze River to Tai Lake (DWYRTL)” Project Based on the Euler Method

Appropriate water body diversion can improve the water quality of Tai Lake. Excessive diversion of water would, however, dramatically alter the local flow fields, which are not conducive to the growth of aquatic plants and the stability of ecosystems. The current “Diverting Water from the Yangtze River to Tai Lake (DWYRTL)” project uses a single water source, the Wangyu River, for diversion, a model that may significantly affect the nearby flow rate or uniformity of the lake and is not conducive to the long-term stability of the aquatic ecosystem in the Tai Lake district of the eastern part of the lake. In order to simulate the different situations of single- and dual-source water diversions (Wangyu-Xinmeng Rivers) in Tai Lake, we based this study on a three-dimensional hydrodynamic model coupled with the Euler method, which can accurately calculate the water exchange rates in the different districts of Tai Lake. The results show that (1) it is recommended that the total annual diversion of water should not exceed 20 × 108 m3; (2) the wind field is the most important factor determining the distribution of spatial water exchange; (3) under wind-free conditions, the flow rate of a single-source diversion of water is approximately 50% higher than that of dual-source diversion; and (4) water diversion under the prevailing conditions of the northwest wind in winter will reduce the semiexchange period of the eastern part of the lake area from 50 to 30 days, significantly changing the nearby district’s uniformity, leading to ecological risks. Therefore, it is recommended that the dual-source water diversion mode be used in winter and windless season, and single-source water diversion mode be used in other seasons.

Contaminant Characteristics and Ecological Risk Assessments of Heavy Metals from River Networks in the Western Area of the Wangyu River

To study the pollution characteristics and ecological risks of heavy metals in the western area of the Wangyu River, water and surface sediment samples of five rivers were investigated. The concentration and chemical fractions of eight heavy metals (Ni, Cu, Cr, Zn, As, Cd, Pb, and Hg) were analyzed, the pollution sources of heavy metals were studied using multivariate statistical analysis, and various ecological risk assessments were applied to identify the level of heavy metal contaminants. The results showed that the concentration of heavy metals in water was low, except for Hg, which was lower than the Class I standard of Surface Water Environmental Quality Standard. The content of heavy metals in surface sediments was high, except for Hg, which was significantly higher than the environmental background values. The partition coefficient of heavy metals in water-sediments showed that Cd, As, and Hg had strong re-emission potential. The Igeo indicated that Cu, Zn, and Cd were in a high pollution state as a whole. The RI showed that Cd was the main ecological risk factor in the study area. The RRSP indicated that the degree of pollution by Ni, Zn, and As was low because of its high residual fraction ratio, which was difficult to release under natural conditions. However, the degree of pollution by Cd was high because it had the highest content of weak acid extractable fraction among all the heavy metals. Therefore, it is necessary to pay more attention to Cd contamination. The source analysis of heavy metals showed that the western area of the Wangyu River was mainly affected by the pollution emissions from the surrounding machinery factories.

Effects of Water Diversion from Yangtze River to Lake Taihu on the Phytoplankton Habitat of the Wangyu River Channel

To reveal the effects of water diversion from the Yangtze River to Lake Taihu on the phytoplankton habitat of the main water transfer channel of the Wangyu River, we investigated the water’s physicochemical parameters and phytoplankton communities during the water diversion and non-diversion periods over the winters between 2014–2016, respectively. During the water diversion periods in the winter of 2014 and 2015, the nutrients and organic pollutant contents of the Wangyu River channel were significantly lower than those during the non-diversion period in 2016. Moreover, the phytoplankton diversities and relative proportions of Bacillariophyta during the diversion periods evidently increased during the water diversion periods in winter. The increase in the water turbidity content, the decrease in the contents of the permanganate index, and the total phosphorus explained only 21.4% of the variations in the phytoplankton communities between the diversion and non-diversion periods in winter, which revealed significant contributions of the allochthonous species from the Yangtze River and tributaries of the Wangyu River to phytoplankton communities in the Wangyu River. The increasing gradient in the contents of nutrients and organic pollutants from the Yangtze River to Lake Taihu indicated the potential allochthonous pollutant inputs along with the Wangyu River. Further controlling the pollutants from the tributaries of the Wangyu River is critical in order to improve the phytoplankton habitats in river channels and Lake Taihu.

Antibiotics pollution in Gonghu Bay in the period of water diversion from Yangtze River to Taihu Lake

As a famous project in China, the water diversion from Yangtze River to Taihu Lake Project has impacts on the water quality of Taihu Lake, especially Gonghu Bay, which is the entrance of the diversion water and the drinking water source for Wuxi and Suzhou. To investigate contamination of the antibiotics in Gonghu Bay in the period of water diversion, 16 antibiotics in 14 water samples collected from Wangyu River and Gonghu Bay in China were analyzed by liquid chromatography–tandem mass spectrometry. The results indicated that the concentration of total antibiotics in Wangyu River and Gonghu Bay ranged from 1320 to 17,209 ng/L (mean: 3920 ± 3841 ng/L). The average level of different antibiotics was tetracyclines (range 1082–15,310 ng/L, mean 3161 ± 3479 ng/L) > quinolones (range 225–1325 ng/L, mean 463 ± 276 ng/L) > sulfonamides (range n.d.–888 ng/L, mean 402 ± 248 ng/L) > macrolides (range 12–17 ng/L, mean 14 ± 2 ng/L), and levels of the detected antibiotics in Gonghu Bay were higher than that in Wangyu River, indicating that the antibiotics pollution in Gonghu Bay were much severer than Wangyu River. Ecological risk evaluation showed that in the Wangyu and Gonghu water, trimethoprim (TMP), sulfacetamide (SAAM), sulfamethoxypyridazine (SMP), and sulfamerazine (SMRZ) presented low ecological risk levels, chlortetracycline (CTC), tetracycline (TC), roxithromycin (ROM), and sulfamethoxazole (SMX) had medium level of risk, and oxytetracycline (OTC), norfloxacin (NOR), ofloxacin (OFL), ciprofloxacin (CIP), and enrofloxacin (ENR) had high level of ecological risk. The total hazard quotient of antibiotic mixtures for each sample site indicated high risk of antibiotics in Wangyu River and Gonghu Bay. In summary, the water diversion could mitigate antibiotic pollution in Gonghu Bay to a certain degree. However, the risk of antibiotics in the Wangyu River and Gonghu Bay is still high.

Occurrence and ecological risk assessment of organic micropollutants in the lower reaches of the Yangtze River, China: A case study of water diversion

Water diversion has been increasingly applied to improve water quality in many water bodies. However, little is known regarding pollution by organic micropollutants (OMPs) in water diversion projects, especially at the supplier, and this pollution may threaten the quality of transferred water. In the present study, a total of 110 OMPs belonging to seven classes were investigated in water and sediment collected from a supplier of the Yangtze River within four water diversion projects. A total of 69 and 58 target OMPs were detected in water and sediment, respectively, at total concentrations reaching 1041.78 ng/L and 5942.24 ng/g dry weight (dw). Polycyclic aromatic hydrocarbons (PAHs) and pharmaceuticals were the predominant pollutants identified. When preliminarily compared with the pollution in the receiving water, the Yangtze River generally exhibited mild OMPs pollution and good water quality parameters, implying a clean water source in the water diversion project. However, in Zongyang and Fenghuangjing, PAHs pollution was more abundant than that in the corresponding receiving water in Chaohu Lake. Ammonia nitrogen pollution in the Wangyu River was comparable to that in Taihu Lake. These findings imply that water diversion may threaten receiving waters in some cases. In addition, the risks of all detected pollutants in both water and sediment were assessed. PAHs in water, especially phenanthrene and high-molecular-weight PAHs, posed high risks to invertebrates, followed by the risks to fish and algae. Pharmaceuticals, such as antibiotics and antidepressants, may also pose risks to algae and fish at a number of locations. To the best of our knowledge, this report is the first to describe OMPs pollution in water diversion projects, and the results provide a new perspective regarding the security of water diversion projects.

Research on appropriate hydraulic retention time on basis of water quality improvement of Lake Taihu

准确估算换水周期对于研究湖泊水体化学、生物变化以及污染物迁移、扩散、转化有着重要意义，换水周期是湖泊的一个重要环境参数.根据2010年实测水文、气象和环湖水量、水质条件，建立3组情景模式：第1组为实况方案，第2组是环湖水量倍比缩放方案，第3组为望虞河水量倍比缩放方案.采用EcoTaihu模型模拟3组情景模式下太湖及各湖区营养盐状况，并根据实测结果对模型进行校验.模型计算结果表明：在2010年太湖水文、气象条件下，150~160 d换水周期条件下太湖氮、磷浓度最低，即太湖适宜换水周期为150～160 d.;Hydrolic retention time in an aquatic environment of lake water has long been of interest to biological limnologists because it is very important for determining lacustrine ecosystem health and sensitive to pollution threats. To evaluate the retention time of Lake Taihu, three scenarios are set up according to the measured data of hydrological, meteorological, boundary conditions of water quantity and quality around the lake in 2010, in which the first is the real scheme, the second is the inflow flux multiplier scheme around the lake, and the last is Wangyu River inflow flux multiplier scheme. EcoTaihu Model is adopted to simulate the nutrients conditions in Lake Taihu and its subzones. The results show that under the hydrological, meteorological and the boundary conditions in 2010, an appropriate hydraulic retention time of Lake Taihu is between 150 days and 160 days.

Water age distribution of the Lake Taihu and impact of the Yangtze River to Lake Taihu Water Transfer Project on the water age

太湖作为典型的风生流湖泊，风场对水体运输和交换的过程起着重要的作用.基于环境水动力学模型EFDC源程序建立了染色剂模型以及水龄模型，借助水龄研究太湖水体的长期输运过程和更新速率特征，从而为太湖的调水工程管理提供科学依据.本文在研究春、夏、秋、冬季不同风场作用下太湖的水龄季节性分布特征的基础上，结合太湖实测风速、流量数据及“引江济太”工程调水运行的现状，着重分析了望虞河枢纽调水运行以及新沟河工程对太湖水龄分布的影响.数值试验的模拟结果表明：太湖水体交换受季风影响明显，春、夏季的水龄相对较大、水体交换较差；靠近湖流入口处的地方水龄较小，远离入口的地方水龄较大；水流流向与风向一致时水龄减小，水循环加快，反之则减慢.望虞河引水引工程能够减小贡湖及湖心区的水龄，加快贡湖湖区及湖心区的水循环；新沟河工程引水能够减小梅梁湖区的水龄，改善该湖区的水质.引水工程的实施对加快整个太湖的水循环做出重要贡献.;Lake Taihu is a typical wind-driven lake, and wind plays an important role in process of water exchange and concentration transportation. Based on Environmental Fluid Dynamics Model (EFDC), water age model and conservative dye model were set up to study characteristics of seasonal water age distribution and to further reveal the impacts of the Wangyu River Water Transfer Project and the Xingou River to the Lake Taihu Transfer Project on water age distribution on basis of winds, inflow and outflow, operations of existing water transfer projects. It is concluded that by the numerical test results, water exchange of Lake Taihu is mainly influenced by the monsoons. Water age is comparably larger in the spring and summer, which indicates the water exchange rate in the spring and summer is lower than that in the autumn and winter. Water ages near inflow locations are comparably smaller, and the locations far from the inflows are larger. Water age is smaller when the flow direction is the same as wind direction, while the exchange of water is increased at the same time and on the contrary water exchange is reduced. During operation of the Wangyu River Water Transfer Project, the water ages of the Gonghu Bay and Middle Lake Taihu are basically reduced, and water exchange is increased in the areas. During operation of the Xingou River Water Transfer Project, the water ages of the Meiliang Bay are basically reduced, and water quality is improved in the area. The water exchange of Lake Taihu will be significantly improved with continuous or occasional transfer operations.

Heavy metal pollution status and ecological risks of sediments under the influence of water transfers in Taihu Lake, China.

The effects of water transfer projects on water channels and the receiving water involved need to be understood. In this research, the compositions and particle size distributions of surface sediment and the Cd, Cr, Cu, Ni, Pb, and Zn contents and distributions in the sediment along a water transfer route from the Wangyu River to Taihu Lake, China, were studied. The correlative relationship between the grain size trend and heavy metal content distribution suggested that heavy metals in Wangyu River sediment have affected the heavy metal contents of Taihu Lake sediment through silt and clay migrating in the transferred water. Enrichment factors and potential ecological risk values were calculated. Low levels of potential ecological risks are posed at 20 sampling sites in Taihu Lake, but higher-to-serious risks (potential ecological risk values >275) are posed at all Wangyu River sites. Toxicity of heavy metals (Cd, Cu, Zn, and Ni) in the Wangyu River sediments is more serious than those in the Taihu Lake, but is similar to the entrance of Gonghu Bay. Multivariate statistical analyses (Pearson correlation, cluster, and factor analyses) suggested heavy metals in the study area have many sources, and the relationships between particle migration and heavy metal contents indicated transferring water are likely to lead to adverse ecological risks being posed in Taihu Lake.

Analysis of isotope tracing of domestic sewage sources in Taihu Lake—A case study of Meiliang Bay and Gonghu Bay

Due to the difficulty of quantifying the temporal and spatial variations of the sewage sources of Taihu Lake, this paper collected water samples from Gonghu Bay and Meiliang Bay, in the northeast of Taihu Lake and from the inflow river of Wangyu River from January to December in 2012 and applied stable isotope techniques to trace the sources of the nitrogen pollutants. At the same time, a two-end-member mixing model of isotopes was used to determine the sources of domestic sewage. According to the results of nitrogen isotope values in the sampling points, the annual proportion of the sewage sources of the Meiliang Bay, Gonghu Bay and Wangyu River is 17.2%, 15.3% and 19.7%, respectively. More than 80% of the nitrogen pollution sources are from non-domestic sewage, which indicates that domestic sewage is not the primary source of nitrogen pollution in Taihu Lake. In addition, these three regions have demonstrated higher ratios of sewage sources during the winter season than during other seasons. Therefore, domestic sewage that flows into Taihu Lake during the winter season should be strictly limited. In the meantime, it is necessary to strengthen the treatment of nitrogen sources other than domestic sewage sources.

Contribution of alkaline phosphatase to phosphorus cycling in natural riparian zones in the Wangyu River running into Lake Taihu

Understanding phosphorus (P) cycling is essential to reducing algal blooms and other negative effects in water. However, few studies have investigated the contributions of alkaline phosphatase (APase) or alkaline phosphatase activity (APA) to P cycling in natural riparian zones. Here, seasonal and spatial development of plankton, P fractions, APA fractions, and fluorescence labeled enzyme activity were investigated in a natural riparian zone in the main diversion channel for water transfer into Lake Taihu. Plankton greatly benefited from APase, and APA production was their important advantage for P acquisition and proliferation. Fluorescence labeling varied greatly between species and seasons, indicating different adaptive strategies for dissolved organic P acquisition. Phytoplankton experienced severe P stress when they were the main APA producers in spring and summer, but bacteria were superior P competitors. During autumn and winter, free APA dominated, phytoplankton APA (phyt-APA) deceased because of low biomass or high dissolved reactive P (DRP) and bacterial APA (bact-APA) proportions were high. Bulk APA and DRP were negatively correlated for the entire data-set and during the productive seasons. Significant negative correlation was observed between phyt-APA and DRP in the lacustrine and wetland zones, but the situation was complicated for bact-APA, probably owing to organic carbon limitation.

Sediment transport following water transfer from Yangtze River to Taihu Basin

To meet the increasing need of fresh water and to improve the water quality of Taihu Lake, water transfer from the Yangtze River was initiated in 2002. This study was performed to investigate the sediment distribution along the river course following water transfer. A rainfall-runoff model was first built to calculate the runoff of the Taihu Basin in 2003. Then, the flow patterns of river networks were simulated using a one-dimensional river network hydrodynamic model. Based on the boundary conditions of the flow in tributaries of the Wangyu River and the water level in Taihu Lake, a one-dimensional hydrodynamic and sediment transport numerical model of the Wangyu River was built to analyze the influences of the inflow rate of the water transfer and the suspended sediment concentration (SSC) of inflow on the sediment transport. The results show that the water transfer inflow rate and SSC of inflow have significant effects on the sediment distribution. The higher the inflow rate or SSC of inflow is, the higher the SSC value is at certain cross-sections along the river course of water transfer. Higher inflow rate and SSC of inflow contribute to higher sediment deposition per kilometer and sediment thickness. It is also concluded that a sharp decrease of the inflow velocity at the entrance of the Wangyu River on the river course of water transfer induces intense sedimentation at the cross-section near the Changshu hydro-junction. With an increasing distance from the Changshu hydro-junction, the sediment deposition and sedimentation thickness decrease gradually along the river course.

Presence and patterns of alkaline phosphatase activity and phosphorus cycling in natural riparian zones under changing nutrient conditions

Phosphorus (P) is an important limiting nutrient in aquatic ecosystems and knowledge of P cycling is fundamental for reducing harmful algae blooms and other negative effects in water. Despite their importance, the characteristics of P cycling under changing nutrient conditions in shallow lakes were poorly investigated. In this study, in situ incubation experiments were conducted in a natural riparian zone in the main diversion channel used for water transfer into Lake Taihu (Wangyu River). Variations in microbial biomass, dissolved P fractions (organic and inorganic), and alkaline phosphatase activity (bulk APA and specific APA) were determined after incubation with and without the addition of P and nitrogen (N) (4 total water treatments: +P, +N, +NP, and control). Experiments were conducted during two seasons (late spring and early fall) to account for natural differences in nutrient levels that may occur in situ . Our results demonstrated that low levels of DRP may not necessarily indicate P limitation. Phytoplankton exhibited “serial N limitation with P stress” in May, such that chlorophyll a (Chl a ) increased significantly with N addition, while the limiting nutrient shifted to P in October and phytoplankton biomass increased with P addition. Phytoplankton contributed greatly to APA production and was significantly influenced by P bioavailability, yet high levels of bulk APA were also not necessarily indicative of P limitation. In contrast to phytoplankton, bacteria were less P stressed. As a consequence of enhanced utilization of dissolved reactive P (DRP) and dissolved organic P (DOP), +N treatment elevated APA significantly. By contrast, APA could be repressed to low values and phytoplankton converted a large portion of DRP to DOP with P addition. But this was not consistent with bacteria APA (bact-APA) in the absence or presence of abundant phytoplankton biomass. The correlation between bulk APA and DRP was good at separate sites and discrepant for the whole data set. Regulation of APA was demonstrated by an inverse hyperbolic relationship between bulk APA, specific APA, and DRP, with a transition from high to low activity occurring between 20 and 50 μg L -1 . This study provides a better understanding of how APA and P cycling change with nutrient perturbations in Lake Taihu system. The obtained results can help understanding the process of P cycling in water and providing a reference for nutrient control in the water transfer project.