Zhu Yuxin

Human influence on heavy metal distribution in the Upper Lake Nansi sediments, Shandong Province, China

Core and surface sediment samples were collected from three sub-lakes (Lake Nanyang, Lake Dushan and Lake Zhaoyang) in the Lake Nansi Basin, Shandong Province. In order to reveal the characteristics of spatial and historical distribution of heavy metals in different sublakes of the Upper Lake Nansi, heavy metal (As, Cr, Cu, Hg, K, Mn, Ni, Pb, Zn, Al, Fe, Ti and V) concentrations of sediment samples were investigated. Based on the activity of137Cs in the sediments, the modern accumulation rate of Lake Nansi sediments is 3.5 mm/a. Our results show that the whole Upper Lake Nansi has been already polluted by heavy metals, among which Lake Nanyang has been polluted seriously by mercury, as well as by lead and arsenic, while Lake Dushan has been most seriously polluted by lead and arsenic. Historical variation of heavy metal (Cr, Cu, K, Ni, Zn, Al, Fe, Ti and V) concentrations shows an abrupt shift in 1962, resulting in a division of two periods: from 1957 to 1962 when metal enrichment increased with time, and from 1962 to 2000 when it decreased with time, while that of some anthropogenic elements such as Hg, Pb and Mn tend to increase toward the surface. However, the variation trend of As in the sediments is different from that of Hg, Pb and Mn, with its maximum value appearing in 1982. Since 1982 the concentrations of As have decreased due to the forbidden use of arsenite pesticides. This variation trend revealed changes in manner of human activity (coal combustion, waste discharges from both industries and urban sewage) within the catchment during different periods.Core and surface sediment samples were collected from three sub-lakes (Lake Nanyang, Lake Dushan and Lake Zhaoyang) in the Lake Nansi Basin, Shandong Province. In order to reveal the characteristics of spatial and historical distribution of heavy metals in different sublakes of the Upper Lake Nansi, heavy metal (As, Cr, Cu, Hg, K, Mn, Ni, Pb, Zn, Al, Fe, Ti and V) concentrations of sediment samples were investigated. Based on the activity of137Cs in the sediments, the modern accumulation rate of Lake Nansi sediments is 3.5 mm/a. Our results show that the whole Upper Lake Nansi has been already polluted by heavy metals, among which Lake Nanyang has been polluted seriously by mercury, as well as by lead and arsenic, while Lake Dushan has been most seriously polluted by lead and arsenic. Historical variation of heavy metal (Cr, Cu, K, Ni, Zn, Al, Fe, Ti and V) concentrations shows an abrupt shift in 1962, resulting in a division of two periods: from 1957 to 1962 when metal enrichment increased with time, and from 1962 to 2000 when it decreased with time, while that of some anthropogenic elements such as Hg, Pb and Mn tend to increase toward the surface. However, the variation trend of As in the sediments is different from that of Hg, Pb and Mn, with its maximum value appearing in 1982. Since 1982 the concentrations of As have decreased due to the forbidden use of arsenite pesticides. This variation trend revealed changes in manner of human activity (coal combustion, waste discharges from both industries and urban sewage) within the catchment during different periods.

Source Analysis of Heavy Metals in Surface Sediments of Lake Taihu

Heavy metals of natural and anthropogenic sources are mixed in lake sediments, and it is dif- ficult to discern. Based on linear regression analysis results and element chemical properties, Al and V are selected as the concentration normalizing elements. The natural and anthropogenic sources contributing to the elemental concentrations in core MS of Lake Taihu are analyzed in terms of element--to--Al ratio versus V--to--Al ratio. Results show that heavy metals were from natural sources before mid 1920s. The heavy metals, such as Al, Fe, Mn, V, Cr, Pb, Cu, Zn and As, were from changed natural sources, and Hg originated from human pollution partly between mid 1920s and 1970s. The heavy metals, such as Pb, Cu, Zn, Hg, As, are contaminated by human pollution since mid 1970s. The source characters of heavy metals are correspondent with the hu- man activities and economic development in Lake Taihu drainage basin.

The enrichment characteristics of mercury in the sediments of Dongjiu and Xijiu, Taihu Lake catchment, in the past century

The concentration and the enrichment factors of mercury (Hg) in the sediment cores of Dongjiu and Xijiu, Taihu Lake catchment, were studied. The accumulation fluxes, anthropogenic input concentration and anthropogenic accumulation fluxes of Hg in recent 100 years were also analyzed based on the 210Pb dating. The results indicate that the increasing concentrations of Hg in the sediments are influenced by natural factors and anthropogenic input simultaneously. Generally, about 2/3 of the Hg in the sediment was from anthropogenic sources. In the early 20th century, the anthropogenic input was owing to the urban development and fossil fuel consumptions surrounding the Taihu Lake and the worldwide atmospheric deposition of Hg since the industrial revolution. The concentration and anthropogenic fluxes of Hg increased with the industrial development in the catchment since the 1930s. It reached the maximum during the middle 1970s and middle 1990s, and decreased since the middle 1990s with constraints on high pollution industries.

Environmental variation in central Tibetan Plateau in the last 200 years

Through the analyses on sediment lithology,210Pb and137Cs dating, carbonate content, Sr/Ca and Mg/Ca of Ostrocod, and carbon and oxygen stable isotope of carbonate of gravity core from Cuoe Lake in the Naqu area, Tibetan Plateau, the paleolimnology was studied to investigate the environmental variation in the central Tibetan Plateau in the last 200 years. It is inferred that the environmental variation has undergone two stages. The climate was arid in the early 100 years, while it became warmer and more humid in the later 100 years, with a period of 20 years for humidity change.

Variation characteristics of heavy metals and nutrients in the core sediments of Taihu Lake and their pollution history

The sedimentary environment change, trophic evolution and heavy metals pollution history of the northern Taihu Lake in the last 100 years are studied according to the sedimentary geochemical proxies of the core sediments, such as grain size, nutrients, heavy metals, diatom, etc. The nutrients in the sediments depended mainly on the lake internal circulation and the heavy metals were from natural geogenic sources before the 1920s, which were not influenced by human activities generally, and grain size was one of the key factors influencing heavy metals content in the sediments. The alternation of manner and strength of human activities in Taihu Lake catchment before and after the 1920s made the lake sediments coarser, and hence heavy metals and TP content decreased contrasted with that before the 1920s. TP content in sediments and water increased from the 1950s to late 1970s due to anthropogenic pollutants discharge, and the lake belonging to mesotrophic state. TN and TOC content and C/N ratio increased due to the increasing external pollutants into Taihu Lake by human activities, TP content also increased obviously in water and sediments, and the diatom association was dominated by eutrophic species since the late 1970s, indicating the eutrophication state of Taihu Lake in this period. Meanwhile the increasing in heavy metals content, such as Cu, Mn, Ni, Pb and Zn, and their proportion of valid fractions in the sediments indicates that they all result from human pollutants since the late 1970s. The heavy metals in the surface sediments have certain potential biological toxicity due to the higher SEM/AVS ratio.

Distribution and Ecological Risk Assessment for Heavy Metals in Superficial Sediments of Nansihu Lake

Heavy metal concentrations (As, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn) of superficial sediments in the Nansihu Lake were investigated in April, 2002. The determination of the heavy metal distribution of the lakes superficial sediments was carried out by ICP-AES. The potential ecological risk index (RI) and geological acumination index(Igeo), as the quantitative diagnostic tools, were used to evaluate the pollution degree of various heavy metals in the sediments. The results show the distribution of pollutants in the sediments could be divided into three sections with different ecological risk characteristics: ⑴ light pollution area in Zhaoyang Lake, ⑵ medium pollution area in Dushan Lake, and ⑶ heavy pollution area in Nanyang Lake.

Temporal and Spatial Distribution of Elements in a Small Catchment, and Buffer Function of Wetland in Longgan Lake, China

Wetland is the conjunction of lake and terrene where human activities are concentrated. From the viewpoints of material transport and cycling in the terrene-lake system, wetland is the buffer where sand and mud, heavy metals, pollutants and nutrients are tarried. In this paper, we provide a case study based on the temporal and spatial distribution of elements in the Wangling River catchment, a small sub-catchment of Longgan Lake in the middle reaches of the Yangtze River. We have found that wetland can buffer major heavy metals such as Cr, Cu, etc. significantly, but has a little buffer function to some active elements such as Fe and Mn, which are always transported as solutions. Human activities not only influence the distribution of elements, but also weaken the buffer function of wetland. Intensive human activities in the Longgan Lake area in the past 70 years have been recorded in stream, wetland and lake sediments, especially the human activity events such as deforesting and reclaiming on a large scale in 1958 and the 1980’s. Human activities caused the increase of sedimentation rates since the 1950’s, as well as the increase of elements’ concentrations. The extensive use of fertilizers and pesticides since the 1960’s have led to the increase of total P concentrations. Increasing SO2 emission accelerate the process of cation exchange in soil, and enhance the leaching of Mn out of soils. Permanent storing of water causes the soil gleyification that also intensifies the leaching of Mn. These are two major reasons for the obvious increase of manganese concentrations in recent 20 years in Longgan Lake. Intensive human activities since the 1950s’ have intensified the population in this region and thus destroyed the buffer function of wetland.

Environmental Characteristics of An Acid Qinghai Lake in Tengchong, Yunnan Province

Qinghai Lake is an acid lake and located in Tengchong County, Yunnan province. Qinghai Lake is a crater lake with continuously acid groundwater supply, which is the geological foundation of the acid lake. We analyzed water, soil, sediment and biological samples of Qinghai Lake. As result showing, the water has low pH value, very low cation concentration and mineralization degree, and obviously migration of element Ca, Mg, Al and Fe in sediment. Few species, low biomass and lack of blue green algae, Gastropoda, Lamellibranchia and Crustacea are most notable characteristics distinguished from general neutral and alkaline lakes. Change of element geochemistry behavior of acid aqueous medium in a lake, and its impact on organisms cause the decrease of acid sensitive species and the increase of acid tolerant species, these are the basic characteristics of Qinghai Lake and dynamic mechanism of forming acid lake environment.

Environmental Changes Revealed by Lacustrine Sediment from Longgan Lake since Last Glacial Maximum

Longgan Lake is located in the lower reaches of the Yangtze River. Based on the sediment pigments, total organic carbon, pollen, grains and susceptibilities, combining with 14 C dating, the environmental evolutions were reconstructed since the Last Glacial Maximum. Before 15.0kaBP and during 10.0-6.3kaBP,the Longgan Lake was characterized by river deposition with lower productivity and higher susceptibility. During 15.0-10.0kaBP,Longgan Lake was formed initiated, as documented by obvious increase of organic production. The rudiment of the lake started from 6.3 kaBP, followed by the stable lake condition after 3.7kaBP. The wetland vegetation was extablished around the lake area after 3 3kaBP. It is necessary, however, to track the changes of sediment source, in order to study the mechanism of lake formation and evolution in Longgan lake,as well as the relationship between the lake and Yangtze River.

The influence of grain size composition on metal content in the sediment: the case of core sediment in Lake Taihu

The metal contents in the sediments are influenced not only by human pollutants, but also by grain size and mineral composition of the sediments, which should be evaluated in the study of heavy metal. The metals contents and their correlations with grain size in sediments of core MS from Lake Taihu are studied in this paper in order to evaluate the grain size effects on metals contents. The metals in core MS can be classified into two categories according to their variation characteristics. Al, Fe, K etc belong to one category, the contents of which are high in the middle-lower section of the sediment core and low in the upper section; Na belongs to the other category, the variation of its content is opposite with the first category. According to the correlations of the metals and grain size, clay content was selected as the normalization component of metals. After normalized by the clay content, the metals contents take on consistent variation along the sediment core. The analysis results show that the metals contents in Core MS are influenced mainly by grain sizes composition and the normalization of metals content must be taken during the study of metals variation and pollution evaluation.