Chen Yuwei

Lead isotope geochemistry of the urban environment in the Pearl River Delta

The study of the Pb isotopic and elemental composition of eolian dusts, aerosols and soils collected from urban areas in the Pearl River Delta, China, indicates that the atmospheric Pb pollution originates from automobile exhausts and industry. The Pb isotopes allow distinguishing between Pb from the natural background, automobile exhausts, and industrial pollution. The Pb isotopes show that the air-carried Pb pollution in Guangzhou and Foshan is a mixture of industrial Pb from the Fankou Pb-Zn giant deposit and automobile exhaust, whereas the pollution in Foshan is mainly from industry. The chemical compositions show that aerosols possess features of volcanic ash, and eolian dusts are mixtures of aluminosilicates-sulfides.

Discussion on possible error for pbytoplankton chlorophyll-a concentration analysis using hot-ethanol extraction method

Hot-ethanol extraction method is a widely used method in the world to determine phytoplankton chloro- phyll-a concentration.This paper aims to introduce the hot-ethanol extraction method in detail to all the scientists dealing with aquatic environment research in China.By experience from the authors,possible error during the oper- ation of the analysis was discussed.Hot-ethanol extraction method is a widely used method in the world to determine phytoplankton chloro- phyll-a concentration.This paper aims to introduce the hot-ethanol extraction method in detail to all the scientists dealing with aquatic environment research in China.By experience from the authors,possible error during the oper- ation of the analysis was discussed.

Geochronological and geochemical constraint on the Cenozoic extension of Cathaysian lithosphere and tectonic evolution of the border sea basins in East Asia

Abstract Geochronological and geochemical evidence indicates that continuous volcanism occurred from 92–38 Ma in Maoming and Sanshui basins in Guangdong. However, the source regions changed sharply from the lower crust to the upper mantle at 56±2 Ma. That change might have been related to the time when India began to collide with Tibet (at ca. 55 Ma). The first stage of opening of border sea basins to East Asia also occurred ca. 56 Ma. A set of pull-apart basins in the Cathaysian block as well as the proto-South China Sea, Celebes Sea and West Philippine Sea were formed during Eocene (53–34 Ma). Indochina was extruded through left-lateral slip along the Red River fault between 35–17 Ma, which interrupted the NE directed shear extension in East Asia. No basaltic magmatism related to extension erupted during this interval. Significant extension of the lithosphere occurred along a NE strike in the Cathaysian block, East Sea and Japan Sea since 17 Ma, which also changed the movement direction of the Indochina block from left-lateral to right-lateral slip. The South China Sea possibly opened again during this stage. Isotopic geochemical features of the mantle beneath the border seas are distinct from those of the Pacific Plate and resemble those of the Indian Ocean domain.

Dynamic variations of water quality in Taihu Lake and multivariate analysis of its influential factors

Dynamic variation of water quality in Meiliang Bay and part of western Taihu Lake has been analysed based on the data from 1991 to 1992. Principal component analysis is used to reveal the mutual relationships of various factors. It is shown that there exists an obvious spatial and temporal variation in the main factors of water quality. Annual values of TP, TN, CON, Chl-a and conductivity decrease evidently from inner Meiliang Bay to the outer from north to south. TP and TN fluctuate seasonally with much higher value in winter. This is particularly true for the mouth of the Liangxi River. In addition, the Chl-a has a synchronous variation with water temperature, although being lagged a little, and closely relates to TP and TN. Finally, the results from principal component analysis show that TP, TN, SS (or SD), water temperature and Chl-a are the most influential factors to water quality in this area, and both suspensions and algae can contribute to transparency in Taihu Lake.

Temporal-spatial variations of euphotic depth of typical lake regions in Lake Taihu and its ecological environmental significance

By using the data of underwater irradiance measured in the different lake regions of Lake Taihu during 1998–2004 and total suspended solids (TSS), wind speeds of the total 13 stations in typical lake regions during 1993–2003, this paper analyzes the factors of influencing on PAR (photosynthetically available radiation) attenuation, euphotic depth, and presents the temporal and spatial variations of euphotic depth of typical lake regions in Lake Taihu, and the spectral distributions of euphotic depth at station 2. The results show that the concentration of TSS is the most important factor impacting PAR attenuation, followed by chlorophyll a; chromophoric dissolved organic matter (CDOM) has little impact on the PAR euphotic depth. During 1993–2003, the mean yearly PAR euphotic depths of the typical lake regions ranged from 1.04 to 1.95 m with a mean value of 1.35±0.23 m. The PAR euphotic depth fell into 3 spatial zone types: Type I, the lowest, including the lake center and the inflows of rivers; Type II, intermediate, including Meiliang Bay, Wulihu Lake and Gonghu Bay; Type III, the greatest, including the East Lake Taihu; corresponding mean depths were approximately 1.1, 1.4, 2.0 m, respectively. The seasonal variations of euphotic depths were not quite the same in different lake regions. In the lake center, the mean values of PAR euphotic depth in summer and autumn were significantly greater than those in winter and spring; in the Meiliang Bay, winter means were significantly greater than in the other three seasons; in the East Lake Taihu, winter means were significantly less than in the other three seasons. However, no distinct seasonal change was recorded in the Wulihu Lake, Gonghu Bay and the inflows of rivers. The spectral distributions of euphotic depth present a minimal value at the blue light wave band of 400 nm, and a peak at the green light wave band of around 580 nm. In 1998 and 1999, based on the seasonal many-day continuous measurements, the PAR euphotic depths at station 2 were recorded 2.00±0.21, 2.52±0.45, 1.58±0.24, 2.00±0.15 m in spring, summer, autumn and winter, respectively. The peak value of 440 nm absorbed by phytoplankton corresponded to a euphotic depth of only 0.81–1.47 m (mean 1.07±0.29 m), which was much lower than the mean PAR euphotic depth of 1.98±0.41 m.

Soil Characteristics in Relation to Vegetation Communities in the Wetlands of Poyang Lake, China

Poyang Lake is an important wetland with global ecological functions. Impact of plant species composition on soil physicochemical characteristics is potentially critical but is as yet poorly understood in this great, shallow and water passing lake wetland. Five dominant plant communities, Phragmites communis community (Phragmites), Polygonum hydropiper community (P. hydropiper), Artemisia selengensis community (A. selengensis), Carex cinerascens community (C. cinerascens) and Phalaris ayuyldinacea community (Phalaris) were surveyed to identify the influences of plant species composition on soil properties. Results show great heterogeneity in soil characters among studied vegetation communities. The lowest average values of pH and soil bulk density are presented in soil with Phragmites, while the highest ones are determined in C. cinerascens and A. selengensis, respectively. Moreover, C. cinerascens is determined with the highest average contents of total organic carbon (TOC) and total nitrogen (TN), whereas Phalaris community presents the lowest soil carbon and nutrient accumulation in surface soil. Plots of C. cinerascens, Phragmites and Phalaris are identified with obvious convergence patterns, while dispersive patterns are identified in A. selengensis and P. hydropiper, suggesting great heterogeneity in soil properties among typical communities in Poyang Lake.

Carbon dioxide partial pressure and carbon fluxes of air-water interface in Taihu Lake, China

To obtain carbon dioxide (CO2) flux between water-air interface of Taihu lake, monthly water samplers at 14 sites and the local meteorological data of the lake were collected and analyzed in 1998. Carbon dioxide partial pressures (pCO2) at air-water interface in the lake were calculated using alkalinity, pH, ionic strength, active coefficient, and water temperature. The carbon fluxes at different sublakes and areas were estimated by concentration gradient between water and air in consideration of Schmidt numbers of 600 and daily mean windspeed at 10 m above water surface. The results indicated that the mean values of pCO2 in Wuli Lake, Meiliang Bay, hydrophyte area, west littoral zone, riverine mouths, and the open lake areas were 1 807.8±1 071.4 (mean±standard deviation) μatm (1atm=1.013 25×105Pa), 416.3±217.0 μatm, 576.5±758.8 μatm, 304.2±243.5 μatm, 1 933.6±1 144.7 μatm, and 448.5±202.6 μatm, respectively. Maximum and minimum pCO2 values were found in the hypertrophic (4 053.7 μatm) and the eutrophic (3.2 μatm) areas. The riverine mouth areas have the maximum fluxes (82.0±62.8 mmol/m2a). But there was no significant difference between eutrophic and mesotrophic areas in pCO2 and the flux of CO2. The hydrophyte area, however, has the minimum (−0.58±12.9 mmol/m2a). In respect to CO2 equilibrium, input of the rivers will obviously influence inorganic carbon distribution in the riverine estuary. For example, the annual mean CO2 flux in Zhihugang River estuary was 19 times of that in Meiliang Bay, although the former is only a part of the latter. The sites in the body of the lake show a clear seasonal cycle with pCO2 higher than atmospheric equilibrium in winter, and much lower than atmospheric in summer due to CO2 consumption by photosynthesis. The CO2 amount of the net annual evasion that enters the atmosphere is 28.42×104 t/a, of which those from the west littoral zone and the open lake account for 53.8% and 36.7%, respectively.

Nitrogen and phosphorus forms and release risks of lake sediments from the middle and lower reaches of the Yangtze River

Cluster analysis, principal component analysis and correlation matrix analysis were used to analysis the nitrogen and phosphorus release risks from sediments in 18 lakes located in the middle and lower reaches of the Yangtze River, as well as the nitrogen and phosphorus forms and related geochemical parameters from sediments, pore waters and overlying waters. The ecological difference of macrophyte and algae dominated lakes was the main reason of the difference of nitrogen and phosphorus release. The release risks were well correlated with the iron-bound phosphorus (FeP), algae available phosphorus (AAP), total nitrogen (TN), total phosphorus (TP) in sediment, the content of nitrogen and phosphorus in overlying and pore waters, porosity and organic matter content of surficial sediment. The AAP and FeP was the main phosphorus forms deciding the phosphorus release risk and other forms were in less effect on it due to the lower contents or lower transformation ability. The sediment organic phosphorus was not directly related to the phosphorus release risks but remarkably positively correlated to organic matter contents in sediment.

Assemblage structure investigation of macrozoobenthos and water quality bioassessment of the main river systems in Taihu Basin

Aimed at characterizing the assemblage structure of macrozoobenthos,identifying the key influencing environmental factors and evaluating the water quality in terms of biological indexes,we investigated macrozoobenthos at 73 sites of the five river systems(Rivers Tiaoxi,Nanhe,Taoge,Huangpu and Yanjiang)within Taihu Basin during April and June of 2010.Total 88 species from 48 families,8 classes and 3 phyla have been found in the investigations.The mean density of macrozoobenthos was 5888.91ind./m2,in which the proportion of oligochaetes was 94.19%.The mean biomass of macrozoobenthos was 105.18g/m2,of gastropods with 72.50% in total biomass.Limnodrilus hoffmeisteri was the dominant species in all river systems.One-way analysis of similarity(ANOSIM)showed that macrozoobenthos assemblages in the Yanjinag River system differed significantly from other four river systems,and those of Tiaoxi and the Taoge River systems differed significantly.L.hoffmeisteri was primarily responsible for dissimilarities of macrozoobenthos assemblages among the five river systems,followed by Bellamya aeruginosa,Branchiura sowerbyi,Chironomus plumosus,Gammarus sp.,Propsilocerus akamusi,Corbicula fluminea,Microchironomus sp.,Chironominae sp.,Glyptotendipes lobiferus,Tanypus chinensis and Alocinma longicornis.Canonical Correspondence Analysis showed that CODMn,PO4-P,TN and NO3-N were strongly correlated with the macrozoobenthos assemblages.The results of bioassessment using the BPI and the Wright Indexes indicated that the five river systems were mostly at status of intermediate polluted.

The Study on Natural Restoration of Aquatic Vegetation in the Northern Lakeside, Lake Taihu

It has been observed and studied that the natural restoration process of aquatic vegetation in the experimental enclosure of northern lakeside, Lake Taihu, from 1997 to 1999 years. It is found that the local macrophytes, for example, the Nymphoides peltata, Trapa sp. and Potamogeton malainus Mig, can be naturally restored in the bare lakeside of big shallow eutrophication lakes by an enclosed protection methods. The cover area by species of Nymphoides peltata and Trapa sp. has taken up to 14.3% and 12.7% of the total enclosure area in the summer of 1998, respectively. The companion species of vegetation are Potamogeton malainus Mig, Hydrilla verticillata Royle and Vallisneria spiralis L. The affection to the natural restore of macrophytes by anthropologic readping and fish culture has also been discussed. According to the results of enclosure experiment, it has provided a strategy for control of eutrophication in big shallow lakes, for example, Taihu Lake.