Wu Fengchang

Characterization of dissolved organic matter fractions from Lake Hongfeng, Southwestern China Plateau.

With XAD-series and ion exchange resins, dissolved organic matter (DOM) from Lake Hongfeng in Southwestern China Plateau was isolated into 6 fractions, i.e., humic acid (HA), fulvic acid (FA), hydrophobic neutrals (HON), hydrophilic acids (HIA), hydrophilic bases (HIB) and hydrophilic neutrals (HIN). Those fractions were characterized by high performance size exclusion chromatography, fluorescence spectroscopy and UV absorbance. Among the 6 fractions, FA was predominant and accounted for 51% of the total DOM. The weight-average (Mw) and number-averaged (Mn) molecular weight of these fractions ranged from 1688 to 2355 Da and from 1338 to 1928 Da, respectively. A strong correlation was observed between specific UV absorbance at 280 nm, E2/E3 (absorbance at 250 nm to 365 nm), and the molecular weight for DOM fractions. UV-Vis fulvic-like fluorescence peaks were found in all fractions. Protein-like fluorescence peaks existed in HON may indicate that microbial activity was severely in Lake Hongfeng. There was a significant relationship between fluorescence intensities and specific UV absorbance at 254 nm for those DOM fractions, suggesting their similar luminescence characteristics. The values of fluorescence index (f450/500) indicated that hydrophobic fractions may derive from terrestrial sources, and the hydrophilic fractions from microbial and terrestrial origins. Those results suggest that there were inter-relationships between molecular weight, fluorescence and absorbance characteristics, and also subtle consistencies between the hydrophilic and hydrophobic properties and the sources for these 6 fractions from Lake Hongfeng.

Natural organic matter and its significance in terrestrial surface environment

Natural organic matter is an important component in terrestrial surface environment. More and more researches indicated that it plays an important role in physical, chemical and biological processes of terrestrial ecosystem; it is the important cycling routes of matter and energy and relates with nearly all the important links of ecosystem. Natural organic matter is not only the important study field of biogeochemistry, ecology and environment sciences, but also a basic theoretical area in the assessment, prediction and control of environment pollution. Natural organic matter now becomes the focus of environment quality, toxicology, environment law and management. Using fresh lake and river as examples, this article briefly summarizes the study results of sources, chemical structure, cycling characteristics, coupling relations with nutrients cycling, and its effects on mobility and transformation of toxic metals and organic pollutants, and expounds the possible right research directions and contents referring to water eutrophication and environment pollution. This article also makes a prospect about modern organic environment and biogeochemistry.

The distribution characteristic and environmental significance of Cesium-137 deposit profile in Chinese lacustrine sediment

Cesium-137(~(137)Cs)is an artificial radionuclide.Its distribution in the deposit profile is used as a tool of sedimentary chronology.In order to know the depth distribution profile characteristics and environmental significance of ~(137)Cs in the sediment of Chinese lake,the literatures concerned were compared and analyzed in this article.We discussed the whole characteristics and main affect factor of lacustrine sedimentary profile of ~(137)Cs in five lake areas by reason of different physiognomy.This research indicated that the ~(137)Cs deposit profile related to the physiographic characteristics,rainfall,vegetation and human activity besides latitude and altitude.The atmospheric nuclear experiment in China and the Chernobyl accident in Pre-Soviet Union potentially influenced on the 137Cs distribution of some zone.Cesium-137(~(137)Cs)is an artificial radionuclide.Its distribution in the deposit profile is used as a tool of sedimentary chronology.In order to know the depth distribution profile characteristics and environmental significance of ~(137)Cs in the sediment of Chinese lake,the literatures concerned were compared and analyzed in this article.We discussed the whole characteristics and main affect factor of lacustrine sedimentary profile of ~(137)Cs in five lake areas by reason of different physiognomy.This research indicated that the ~(137)Cs deposit profile related to the physiographic characteristics,rainfall,vegetation and human activity besides latitude and altitude.The atmospheric nuclear experiment in China and the Chernobyl accident in Pre-Soviet Union potentially influenced on the 137Cs distribution of some zone.

Environmental behavior and toxicity of engineered nanomaterials

With rapid development and application of nanotechnology, there is an increasing concern over the environmental fate, behavior, toxicity, exposure and risk of engineered nanomaterials (ENMS). In this review, we presented the release pathways of ENMS into the environment and their potential environmental behavior with a focus on the suspension and aggregation of ENMS and their interactions with dissolved organic matter and contaminants. In addition, toxicity of several types of engineered ENMS to various organisms was discussed. Then, we concluded with the future research perspectives of engineered ENMS.

Molecular Weight Distribution of Dissolved Organic Matter in Lake Hongfeng Determined by High Performance Size Exclusion Chromatography (HPSEC) With On-Line UV-Vis Absorbance and Fluorescence Detection

The molecular weight distribution (MWD) of dissolved organic matter (DOM) in lake waters from Lake Hongfeng was examined using high performance size exclusion chromatography (HPSEC) with UV-vis absorbance and fluorescence detection. The elution curves obtained by absorbance and fluorescence techniques expressed similar patterns, with the exception of diminishing of large fraction and the peaks behind several seconds in fluorescence chromatograms. According to its molecular weight (MW), DOM in water samples is divided into several fractions: large (> 3.5 kDa); medium-large (3.5−2.0 kDa); medium (2.0−1.0 kDa) and small (< 1.0 kDa). The average molecular weight was calculated using the elution curve detected by UV-vis absorbance and fluorescence detection techniques. The results showed that the weight-average molecular weight (Mw) and number-average molecular weight (Mn) calculated by UV-vis absorbance techniques range from 1750 to 2050 Dalton and from 1450 to 1850 Dalton, respectively. And theMw andMn obtained by fluorescence detection are lower by 50 to 400 Dalton. As a reference, the molecular weight of Fluka humic acid (FHA) is larger than that of water samples by about 200 Dalton. The average molecular weight of DOM for water samples collected in March and July was compared. The results revealed that the molecular weight is lower for water samples obtained in July than that obtained in March, indicating the ambient environment has an influence on the molecular weight, including photo-degradation and biological activity.

Mechanism of seasonal deterioration of water quality in Lake Baihua, China

Water quality of Lake Baihua was found worsening in the autumn of 1994. Studies have shown that the decomposition of organic matter in the upper-level sediments resulted in seasonal anoxia with the release of P, Mn, and S2− from the sediments to the overlying water column, and the increase of NO2− concentration led to blackening of the water column, death of fishes and secondary Mn pollution.

Seasonal variation and vertical characteristics of the δ~(15)N of particulate organic matter in Lake Hongfeng and Lake Baihua, Guizhou Province

The stable nitrogen isotopic ratios of particulate organic matter (δ15NPOM) was used to elucidate the seasonal variation and vertical characteristics of the different dissolved inorganic nitrogen sources and autochthonous biogeochemistry processes in two lakes (Hongfeng and Baihua) in Guizhou Province, China. The δ15N values of surface POM seasonally varied from 3.7‰ to 14.9‰ in Lake Hongfeng and from 1.3‰ to 8.7‰ in Lake Baihua. It indicated that source of POM was greatly varied in these two lakes during study period. In Lake Hongfeng, the higher δ15N POM values appeared in winter (February, 2004) and summer (September, 2003). The highest δ15N POM values in winter were attributted to the input of high contents and 15N-enriched inorganic nitrogen from industry wastes. During spring, the δ15N POM values decreased when phytoplankton uptake 14N-enriched inorganic nitrate generated by nitrification in the interior Lake Hongfeng. The variation of δ15N values in surface POM coincided well with the variation of δ15N values of inorganic nitrogen sources. It suggestted that the variation of δ15NPOM mainly influenced by inorganic nitrogen sources, which might resulted from the impact of allochthonous human activities. In Lake Baihua, the higher values of δ15NPOM appeared in summer (September, 2003) while the values were low during winter season. These high and low values were possibly aroused by the growth of primary production and large 15N-depleted organic particles input from sewage respectively. In addition, the combination of δ15NPOM and C/N values in the vertical profile can be used to trace some special biogeochemistry processes in lacustrine ecosystem.

The eutrophication process of Lake Dianchi: evidences from the δ~(13)C value of the bound nC_(16:0) fatty acid

The purpose of this study is to investigate changes in sedimentary environments in Lake Dianchi, a shallow water lake on the Yun-Gui Plateau. Overall characteristics of organic matter values, including δ13Corg, δ13N, C/N and TOC, from a 63cm-long core from the center of the lake were analyzed. Concentrations and stable carbon isotopic compositions of the bound fatty acids are also analyzed and compared with those of the corresponding free fatty acids. The results indicate that the past environment changes recorded in the modern sediments in Lake Dianchi can be divided into three main stages. Values of δ13N and TOC increased during the latest stage of the 0-20cm interval and were related with the eutrophication process of the Lake Dianchi, when concentrations ofbound fatty acids and free fatty acids range from 38.5-209.6μg/g and 12.0-318.1μg/g, respectively. Compared to free fatty acids, bound fatty acids in the sediments of Lake Dianchi have more abundant unsaturated fatty acids, iso- and anteiso-branched fatty acids, indicating that they predominantly sourced from the plankton and bacteria and were more resistant to the early chemical and biological degradation. Multiplying of the plankton and bacteria caused the speeding up the lake eutrophication processes. Changes in the δ13C value of the bound nC16:0 fatty acid were recorded well in Lake Dianchi sediments and provided good information of the enhancement of lake eutrophication in the recent few decades. Therefore, it will become an important indicator reflecting the lake hyper-eutrophication.

Characteristics and influence to overlying water of amino acids from typical plants distributed in Lake Taihu,China

The concentrations of total hydrolyzable amino acids( THAAs) were investigated in 8 kinds of typical plants of both East Lake Taihu and Gonghu Bay,in order to find the links and differences of composition of THAAs in the typical plants,sediments and water as well as the composition of THAAs in different typical plants of Lake Taihu. The form and composition of 15 kinds of THAAs in 18 samples were analyzed by o-phthalaldehyde pre-column derivatization-RP-HPLC. The average concentration of THAAs in typical plants of East Lake Taihu was 861. 6 ± 182. 96 μmol / g. The average concentration in typical plants of Gonghu Bay was 700. 0 ± 232. 3 μmol / g. The comparison of the concentrations of THAAs in different kinds of plants showed submerged macrophytes and floating-leaved macrophytes had the highest concentration of THAAs,followed by emerged macrophytes and terrestrial plants. The dominating amino acids were Asparagine,Glutamic acid,Arginine,Alanine and Lysine,which accounted for more than 50% of concentration of THAAs. About 30. 7%-94. 7% of the N in plants were from THAAs,which was an important source of N in plants. Meanwhile,in comparison with the composition of THAAs in sediments and water in Lake Taihu,the typical plants generally aligned with sediments but different from the water. It showed that THAAs in plant may be an important source of the THAAS in sediments.

ANNUAL LAMINATIONS IN THE SEDIMENTS OF HONGFENG LAKE, CHINA

Hongfeng Lake is an eutrophic freshwater artificial reservior. It began to restore water in 1960. Three sediment cores were taken from beneth about 25 m of water in the center of Hongfeng Lake in May 1991. The stratigraphy of the three cores was easily matched by using prominent marking horizons and characteristic seqnences of laminations. In three layer samples studied, diatom and other algae taxa appear in repeating sequences. The presence of laminations may reflect either the regular changes of physical-chemical conditions within the lake or the variation in the intensity of erosion and transport of material from the catchment, part iculaly where instability in the lake-water system has occurred as a result of human activities. The laminations were mainly caused by seasonal variation of environmental conditions, particularly climate. Unlike most of the previous examples, they have been formed at most recent sediments, in a small freshwater lake in the eastern slope of the Qinghai-Xizang Plateau, China in a subtropical climate, which is mainly controlled by southeastern and southwestern monsoon. It is believed that it’s the first reported instance of laminated lake sediments from China.