Jinglu Wu

Heavy Metal Pollution of Lakes along the Mid-Lower Reaches of the Yangtze River in China: Intensity, Sources and Spatial Patterns

Lakes in the middle and lower reaches of the Yangtze River form a shallow lake group unique in the World that is becoming increasingly polluted by heavy metals. Previous studies have largely focused on individual lakes, with limited exploration of the regional pattern of heavy metal pollution of the lake group in this area. This paper explores the sources, intensity and spatial patterns of heavy metal pollution of lake sediments. A total of 45 sample lakes were selected and the concentrations of key metal elements in the sediments of each lake were measured. The cluster analysis (CA), principal component analysis (PCA) and Geo-accumulation index (Ig) analysis permitted analysis of the source and pollution intensity of the target lakes. Results suggested a notable spatial variation amongst the sample lakes. Lakes in the upper part of the lower reach of the Yangtze River surrounded by typical urban landscapes were strongly or extremely polluted, with high concentrations of Pb, Zn, Cu and Cd in their sediments. This was attributed to large amount of untreated industrial discharges and municipal sewage produced within the lake catchments. In contrast, the heavy-metal pollution of lakes in the Taihu Delta area was notably lower due to industrial restructuring and implementation of effective environmental protection measures. Lakes along the middle reach of Yangtze River surrounded by agricultural areas were unpolluted to moderately polluted by heavy metals overall. Our results suggested that lakes in the central part of China require immediate attention and efforts should be made to implement management plans to prevent further degradation of water quality in these lakes.

Water and Sediment Quality in Lakes along the Middle and Lower Reaches of the Yangtze River, China

Water and sediment samples were collected from 45 lakes along the middle-lower Yangtze River, China. Each lake was sampled seasonally, over a period of one year. Water quality variables and metals in sediments were measured. Lakes along the lowest part of the river, within the Yangtze River Delta, had highest nutrient concentrations and were eutrophic or hypereutrophic. Lakes displayed a gradient in many water chemistry variables, from the middle to the lower Yangtze River. Lakes of the Delta region had the highest conductivity, sulfate, turbidity, and Chl-a values, and the lowest dissolved oxygen concentrations. A number of lakes near urban areas in the study region also displayed similar conditions. Lakes polluted by heavy metals were found in the upper part of the lower Yangtze River and had high Cu, Cr, and Co concentrations in sediments. The mean Igeo (index of geoaccumulation) values for Cu, Cr, and Co classes ranged from 0 to 4, indicating moderate to heavy contamination, contributed mainly from untreated industrial waste water produced within the lake catchments. Lakes of the middle Yangtze River are generally in relatively better condition, except for those around urban zones, which experience higher nutrient and heavy metal loading. The spatial distribution of lake conditions in the area can be related to the policy of regional economic development. The Delta region in China is developed and includes such cities as Shanghai and Suzhou. Heavy industries have moved into the interior region of China too, and development of modern cities is now occurring under some level of environmental protection. Nevertheless, lakes in the central part are becoming seriously polluted with both heavy metals and nutrients because local authorities promote industrialization and urbanization to improve economic conditions, while often ignoring environmental protection. Pollution is increasingly occurring in upstream reaches, a tendency that will bring more environmental problems. Interior lakes of China require immediate attention to prevent further declines in water quality.

Water Quantity and Quality of Six Lakes in the Arid Xinjiang Region, NW China

Xinjiang arid region is situated in the hinterland of Asia, characterized by very low precipitation and high evaporation. Most lakes in the region have evolved naturally to salt lakes and lagoons over the long term. In recent decades, driven by continuous climate warming and human activities, the water quantity and quality of lakes have fluctuated frequently, which has had significant impacts on regional resources and the environment. In this article, the water quantity and quality of six lakes, from saline to fresh, were studied. They are located at different geomorphologic regions (e.g., mountains and plains) in Xinjiang, China. Mountain Lakes Kanasi and Sailimu have expanded slightly, but their water quantity and quality have not changed significantly over the past decade. Oasis lakes, such as Lake Bositeng and Lake Chaiwopu, and tail-end lakes, such as Lake Wulungu and Lake Ebinur, have reduced in area, and in general, the water has become saline. Lake changes were mainly responses to the regional climate change, although factors like human activities and basin morphological characteristics have led to individual differences in lake evolution. Changes in water quality and quantity are clearly linked. Where water quantity increased, water became less salty and vice versa. Over the past decade, water quality of the mountain lakes (Sailimu and Kanasi) were relatively stable, but oasis lakes (i.e., Bositeng and Chaiwopu) continue to deteriorate, whereas water quality of the tail-end lakes (Wulungu and Ebinur) display unstable hydrochemistry.

Geochemical Responses to Anthropogenic and Natural Influences in Ebinur Lake Sediments of Arid Northwest China.

Geochemical concentrations were extracted for a short sediment core from Ebinur Lake, located in arid northwest China, and mathematical methods were used to demonstrate the complex pattern of the geochemical anomalies resulting from the temporal changes in natural and anthropogenic forces on the lake sediments. The first element assemblage (C1) (aluminum, potassium, iron, magnesium, beryllium, etc.) was predominantly terrigenous; among the assemblage, total phosphorus and titanium were generally consistent with aluminum except with regards to their surface sequences, which inferred the differences of source regions for terrigenous detrital material led to this change around ca. 2000AD. The second assemblage (C2) (calcium and strontium) was found to have a negative relationship with aluminum through a cluster analysis. The third assemblage (C3) included sodium and magnesium, which were influenced by the underwater lake environment and deposited in the Ebinur depression. The concentration ratio of C1/(C1+C2) was used as an indicator for denudation amount of detrital materials, which was supported by the values of magnetic susceptibility. The enrichment factors for heavy metals suggested that the influence of human activities on heavy-metal enrichment in Ebinur Lake region was not severe over the past century. Prior to the 1960s, geochemical indicators suggested a stable lacustrine environment with higher water levels. Beginning in the 1960s, high agricultural water demand resulted in rapid declines in lake water level, with subsequent increases of lake water salinity, as evidenced by enhanced sodium concentration in lake core sediments. During this period, anthropogenic activity also enhanced the intensity of weathering and the denudation of the Ebinur watershed.

A 200-year sediment record of environmental change from Lake Sayram, Tianshan Mountains in China

Two parallel sediment cores (30 cm long) were extracted from Lake Sayram, in the Tianshan Mountains of Xinjiang in arid northwest China. We used 210Pb and 137Cs dating, multi-proxy indices, including geochemical composition, carbonate content, magnetic susceptibility (MS), and δ13C and δ18O of bulk carbonate, to reconstruct regional environmental change over the past two centuries. High evaporation modifies δ18O and δ13C of the dissolved inorganic carbon in lake water and may be responsible for the covariance between δ13C and δ18O of bulk carbonate. The ratio of immobile to mobile elements (CI = (Fe+Al+Mn+Cr+Co+Ni)/(K+Na+Ca+Mg+Sr+Ba)) is associated with humidity, and the ratio of Sr/Ca reflects lake salinity. Constrained cluster analysis of the multi-proxy indices was used to partition sediment deposition into three periods. In the first period of 1820–1890s, the climate was dryer with high evaporation, and lake water had higher salinity. During the second period from 1890s to 1960s, multi-proxy indices suggested that regional humidity increased and there was relatively more chemical weathering. The latest period, 1960s to present day, was the wettest of the past nearly 200 years. Nevertheless, we infer that human-related impacts have greatly increased in the last 50 years from the increased MS and phosphorus content.

Organochlorine pesticides and polycyclic aromatic hydrocarbons in water and sediment of the Bosten Lake, Northwest China

We evaluated organic pollution in Bosten Lake, Xinjiang, China, by measuring the concentrations and distributions of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs). Water and sediment samples were collected from 19 sites (B1–B19) in the lake for analysis. Our analytical results show that the concentrations of total OCPs in water ranges from 30.3 to 91.6 ng/L and the concentrations of PAHs ranges from undetectable (ND) to 368.7 ng/L. The concentrations of total OCPs in surface (i.e., lake bottom) sediment ranges from 6.9 to 16.7 ng/g and the concentrations of PAHs ranges from 25.2 to 491.0 ng/g. Hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) account for large proportions of the OCPs. Low α- to γ-HCH ratios in both water and sediment samples indicate possible contributions from both industrial products and lindane. DDTs in water are probably from historical input, whereas DDTs in sediments are from both historical and recent inputs. Moreover, DDT products in both water and sediments were from multiple sources in the northwestern part of the lake (B11, B12, B13, and B14). Fugacity ratios for DDT isomers (p,p′-DDE and p,p′-DDT) at these sites were generally higher than equilibrium values. These results suggest that the input from the Kaidu River and diffusion of DDTs from the sediment to the water are responsible for DDT pollution in the water. Lower-molecular-weight PAHs, which originate primarily from wood and coal combustion and petroleum sources, represent the major fraction of the PAHs in both water and sediment samples. Our findings indicate that OCPs and PAHs in Bosten Lake can be attributed primarily to human activities. A risk assessment of OCPs and PAHs in water and sediment from Bosten Lake, however, suggests that concentrations are not yet high enough to cause adverse biological effects on the aquatic ecosystem.

Hydrochemical and isotopic characters of surface water in agricultural oases of the Tianshan Mountains, Northwest China

ABSTRACT For evaluating the status of surface water in agricultural oases of the Tianshan Mountains and discussing the influences of human activities and geographical factors on hydrochemical process, we conducted hydrochemical investigations of surface water in two major agricultural oases: Manas and Yili. The δ2H and δ18O of surface water in Manas Oasis ranged from −75.4‰ to − 46.2‰ and −11.6‰ to − 5.5‰, respectively, and from −86.4‰ to − 71.8‰ and −12.5‰ to − 10.7‰ in Yili Oasis. Because rivers are mainly supplied by meltwater from ice and snow, the deuterium excess parameter is mostly positive in the oasis surface waters supplied by these rivers. Ca2+-Mg2+- is the major hydrochemical facies type in Yili and Manas oases. Surface waters of both regions are slightly saturated with carbonate minerals and undersaturated with respect to evaporite minerals, suggesting that the minerals present in the water are mainly produced by calcite and dolomite weathering. Total dissolved solids (TDS) in Manas Oasis are higher than those in Yili Oasis. The δ2H and δ18O of surface water samples in Manas Oasis are isotopically enriched, which indicates that the evaporation effect on Manas is stronger than on Yili. The relatively high salinity in Manas is also associated with local contamination by soil leaching. Agricultural activities are important to the quality of surface water. If such activity is not controlled, water salinization will be increased. Clarification of the hydrological status of these oases and their factors will be used for water management and protection of agricultural oases.

Spatial and temporal distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in sediments from Poyang Lake, China

Concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured in 22 surface sediment samples and an approximately 100-year scale sediment core collected from Poyang Lake. This valuable sediments enable analysis of spatial and temporal distribution patterns of PAH sources, and determine the anthropogenic impacts on Poyang Lake. Total PAH concentrations in the surface sediments ranged from 73.2 to 367.2 ng/g dw, and higher residues were encountered in regions with high-density populations and intensive human activities. Total PAH concentrations in the sediment core ranged from 42.0 to 334.0 ng/g dw and were grouped in two clusters (pre-1990s and post-1990s to the present). PAH concentrations in sediments changed both temporally and spatially, suggesting a difference in PAH sources. Before the 1990s, major PAH sources in the sediment core were from coal, wood and grass combustion. This finding naturally agrees with open lake conditions on a spatial scale, which were related to agricultural activities. Petroleum combustion from industrialization and urbanization has become the predominant PAH source in the sediment core from the 1990s to the present and corresponds to sources observed in the southwestern lake near the relatively developed Nanchang City. In the northern lake leading to the Yangtze River, certain petroleum-related contaminants from shipping have become the main PAH sources. The different PAH sources observed in sediments generally reflect the degree of socio-economic development in the Poyang Lake valley, which is consistent with the local written records, indirectly validating the connection of sediment PAH records to the history of human activities in and around Poyang Lake.

Water Chemistry and Stable Isotopes of Different Water Types in Tajikistan

The concentration of major ions and their molar ratios are used to identify sources of the solutes and highlight their hydrochemical evolutions in surface waters. Oxygen and hydrogen isotopes of stream and lake waters are ideal to characterize sources and transport pathways of incoming precipitation. In order to analyze the spatial distribution characteristics and further explore the formation reason and environmental significance, major ions and isotopes of hydrogen and oxygen were measured in lake, river and spring water samples collected in Tajikistan from September to October 2011. Ca2+ and HCO3− were the dominant ions of river and spring waters, and originated mainly from carbonate weathering. The northwestern waters were of the Ca-SO42− type resulting from silicate weathering. Most lakes of Tajikistan are located in the eastern, mountainous area and are of the Mg-SO42− and Na-Cl− type, reflecting persistent, long-term evaporation under an arid climate. The hydrogen and oxygen isotope values of river and spring water in Tajikistan ranged from −129 to −65‰ and −17 to −9.3‰, respectively, and display larger variance in spatial distribution, indicating that river and spring waters in the east are supplied mainly by glaciers and waters in the west come mainly from precipitation. Regression lines between hydrogen and oxygen isotopes in waters from the eastern (δD = 9.2δ18O + 28.0) and western (δD = 5.5δ18O - 10.7) rivers and springs differ as a consequence of different moisture sources in the two areas. Significant correlations between hydrochemistry and isotope values in lake water mainly reflect the intensity of evaporation under arid climate conditions.