Fractionation of Heavy Metals in Surface Sediments of Taihu Lake, East China

The BCR (European Communities Bureau of Reference) three-step sequential extraction procedure was applied to fractionate heavy metals in the sediment of Taihu Lake. For the determination of total metal concentration of the sediments, sample digestion was achieved by using HF/H₂O₂/HNO₃(2/1/1) acid mixture in a microwave-irradiated closed vessel system. The concentrations of Cd, Ni, Cr, Zn, Cu and Pb in various extracts solutions were analyzed by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). The results obtained from the BCR three-step sequential extraction indicated relatively high mobility of Zn, Cu, Pb and Ni in the sediments while Cd and Cr were poorly mobile. Enrichment of heavy metals was found in the sediments collected in the northern parts of Taihu Lake. In the sediments collected in the southern and western sides of the Lake, heavy metal concentrations were relatively low. The relationship between total organic carbon (TOC) and heavy metals concentrations in the sediments is discussed.     

Changes of soil microbiological properties caused by land use changing from rice-wheat rotation to vegetable cultivation

A survey was done recently in Jiaxing city of Zhejiang Province in the Yangtze River Delta to compare the differences of soil microbiological properties among paddy soils with different land use including continuous open-field vegetable cultivation (OFVC), plastic-greenhouse vegetable cultivation (PGVC) and traditional rice-wheat rotation (RWR). The soil types included are percolating, permeable and waterlogged paddy soils. The results indicate that the microbial flora was markedly changed as the land use changed for all the three soil types. In continuous vegetable cultivation soils, especially in PGVC soils, the bacteria amounts decreased dramatically, but the fungal and actinomyce amounts increased as compared with RWR soils. The dehydrogenase activities decreased significantly in vegetable soils, especially in PGVC soils as compared with RWR soils. The microbial biomass C and the total phospholipid contents (TPL) in vegetable cultivation soil greatly decreased as compared with RWR soils. Biolog analysis indicated that the kinds of carbon sources that could be metabolized by native microbes in PGVC soils greatly decreased as compared with OFVC soils and RWR soils, revealing that microbial diversity had decreased since land use change. The activities of some soil enzymes including urease, invertase and phosphase were all lower in OFVC soils than those in RWR soils, and those in PGVC soils were the lowest. The degradation of microbiological activities in continuous vegetable cultivation soils, especially in PGVC soils, as compared with RWR soils might have been caused by soil acidification and accumulation of salts due to overuse of both organic and inorganic fertilizers in vegetable cultivation.     

DNA changes in barley (Hordeum vulgare) seedlings induced by cadmium pollution using RAPD analysis

In recent years, several plant species have been used as bioindicators, and several tests have been developed to evaluate the toxicity of environmental contaminants on vegetal organisms. In this study, barley (Hordeum vulgare L) seedling was used as bioindicator of cadmium (Cd) pollution in the range of 30-120 mgl(-1). Inhibition of root growth and reduction of total soluble protein content in root tips of barley seedlings were observed with the increase of Cd concentrations. The changes occurring in random amplified polymorphic DNA (RAPD) profiles of root tips following Cd treatment included variation in band intensity, loss of normal bands and appearance of new bands compared with the normal seedlings. Additionally, we found that the effect of changes was dose-dependent. These results indicated that genomic template stability (a qualitative measure reflecting changes in RAPD profiles) was significantly affected at the above Cd concentration. Thus, DNA polymorphisms detected by RAPD analysis could be used as an investigation tool for environmental toxicology and as a useful biomarker assay for the detection of genotoxic effects of Cd pollution on plants.     

The integrated use of chemical analysis, cytochrome P450 and stress proteins in mussels to assess pollution along the Galician coast (NW Spain)

Aliphatic and polycyclic aromatic hydrocarbons (PAHs) as well as biochemical markers, such as cytochrome P450, benzo(a)pyrene hydroxylase (BPH) and stress-70 proteins, were determined in mussels (Mytilus galloprovincialis) collected in October 1995 from several locations along the Galician coast (NW Spain). The survey proved the existence of a pollution gradient among sampling sites and a chronic exposure to petrogenic and pyrolitic hydrocarbons. This was reflected in mussel tissue levels of PAHs which ranged from 22 to 562 ng/g wet weight. High levels of total cytochrome P450 were detected in mussels from the most polluted sites, but differences were not statistically significant. BPH activity did not show either differences among sampling sites. Conversely, stress-70 proteins were significantly induced in the most polluted locations, and levels of the 72-kDa band correlated well (r2 = 0.854) with the sum of the PAHs from four to six rings accumulated by mussels.     

Three-dimensional quantitative structure activity relationship (3D-QSAR) analysis for in vitro toxicity of chlorophenols to HepG2 cells

In the present paper, comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were applied to investigate two 3D-QSAR models for the cytotoxicity of chlorophenols. These models have evaluated the intensity of chlorophenols' toxicity on HepG2 cells in vitro. The CoMFA model has both high consistency and predictability. The contribution of the electrostatic field to biological activity is greater than that of the steric field. The CoMSIA model used in this study includes two fields, one is hydrophobic field, and the other is electrostatic field. The relative contribution of them is 0.789:0.211. Consisted with the CoMFA model, the CoMSIA electrostatic filed also plays a dominant role. The CoMFA and CoMSIA contour maps significantly elucidated that the electrostatic field is more important than the other fields and might be one of the reasons resulting in potential reactive mechanism involved in cell proliferation inhibition.     

Photocatalytic degradation of AZO dyes by supported TiO2 + UV in aqueous solution

The photocatalytic degradation performance of photocatalysts TiO2 supported on 13-X, Na-Y, 4A zeolites with different loading content was evaluated using the photocatalytic oxidation of dyes direct fast scarlet 4BS and acid red 3B in aqueous medium. The results showed that the best reaction dosage of TiO2-zeolite catalysts is about 2 g/l and the photocatalytic kinetics follows first order for all supported catalysts. The photocatalytic activity order of the three series catalysts is 13X type >Y type >4A type. The physical state of titanium dioxide on the supports is evaluated by X-ray photoelectron spectra (XPS), powder X-ray diffraction (XRD), BET, and FTIR.     

Comparison of ozone uptake and sensitivity between a phytotron study with young beech and a field experiment with adult beech (Fagus sylvatica)

Chamber experiments on juvenile trees have resulted in severe injury and accelerated loss of leaves along with reduced biomass production under chronically enhanced O3 levels. In contrast, the few studies conducted on adult forest trees in the field have reported low O3 sensitivity. In the present study, young beech in phytotrons was more sensitive to O3 than adult beech in the field, although employed O3 regimes were similar. The hypotheses tested were that: (1) differences in O3 uptake were caused by the ontogenetically higher stomatal conductance of young compared to adult trees, (2) the experimental settings in the phytotrons enhanced O3 uptake compared to field conditions, and (3) a low detoxification capacity contributes to the higher O3 sensitivity of the young trees. The higher O3 sensitivity of juvenile beech in the phytotrons is demonstrated to relate to both the experimental conditions and the physiological responsiveness inherent to tree age.     

Evaluation of biomarkers in caged fishes and mussels to assess the quality of waters in a bay of the NW Mediterranean Sea

Specimens of sea bass (Dicentrarchus labrax) were placed in cages for 1 month in spring and autumn at different locations in the Bay of Cannes (NW Mediterranean). Biochemical markers evaluated were: ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) activities in fish livers and acetylcholinesterase (AChE) activity in fish muscle. EROD and GST activities were higher in front of the outlet for the wastewater plant of Cannes and in the harbour than outside the marina. High EROD and GST activities may be induced by petrol hydrocarbons and/or polychlorinated biphenyls (PCBs). AChE was low in the muscles of the fish caged in the harbour compared with samples from the other cages. Low AChE activity could suggest the presence of organophosphorus and carbamate compounds in seawater from the harbour. Mussels (Mytilus galloprovincialis) were caged off Cannes for the same periods as the fishes. Heavy metal, metallothionein (MT) concentrations and lysosomal membrane stability were evaluated in the digestive gland of the mussels. Results show low heavy metal and MT concentrations, implying low metal concentrations in the surrounding waters. High lysosomal membrane stability revealed a good physiological status of these animals after caging. The whole set of data indicates that seawater in the Bay of Cannes appeared to be unpolluted as regards pollutants which may induce the measured biomarkers, except in restricted areas.     

Bioaccumulation of the rare earth elements lanthanum, gadolinium and yttrium in carp (Cyprinus carpio)

Widespread use of the rare earth elements (REEs) in China for agricultural purposes, together with many other applications, has resulted in a remarkable increase of REE concentrations in the environment. The comparative bioaccumulations of representative light, medium and heavy REEs in a variety of tissues of carp (Cyprinus carpio L.) were investigated for an evaluation of their impacts on aquatic animals. The fish were exposed continuously to solutions containing 0.50 mg litre(-1) of each element for 45 days at pH 6.0 and sacrificed at time intervals. Skeleton, muscle, gills and internal organs were analysed for REE contents. A method using cation-exchange resin separation and ICP-AES determination was developed for the quatification of individual REEs. The results show that carp has low ability to take up the REEs under the experimental conditions. The order of REEs under the experimental conditions. The order of maximum bioconcentration factors was mostly internal organs > gills > skeleton > muscle. Neither synergistic nor antagonistic effects of the mixed REE solutions for carp were observed. The relative distributions of different REEs in the investigated tissues exhibited similar patterns. Among the selected tissues studied, the concentration of a heavy REE (Y) was the smallest, while concentrations of a medium (Gd) and a light REE (La) showed only a slight difference.     

The role of citric acid on the phytoremediation of heavy metal contaminated soil

Adsorption and hydroponics experiments were conducted to study the role of citric acid on the phytoremediation of heavy metal contaminated soil. The results show that addition of citric acid decreased the adsorption of both lead and cadmium, such an effect was bigger for cadmium than for lead. The decrease in the adsorption of Pb and Cd was mainly due to a decrease of pH in the presence of citric acid. The presence of citric acid could alleviate the toxicity of Pb and Cd to radish, and stimulate their transportation from root to shoot. The studies of heavy metal forms using sequential extraction demonstrated that lead was mainly existed as FHAC (a lower bioavailable form) in the root, while F(HCl) was the dominant form in the leaf. The addition of citric acid to the soil changed the concentration and relative abundance of all the forms. The detoxifying effect of citric acid to Pb in shoots might result from the transformation of higher toxic forms into lower toxic forms. Cadmium was mainly present as F(NaCl), therefore, it had higher toxicity than lead. The addition of citric acid increased the abundance of F(H2O) + F(NaCl), indicating that citric acid treatment could transform cadmium into more transportable forms.