Survey of heavy metal pollution and assessment of agricultural soil in Yangzhong district, Jiangsu Province, China

We investigated concentrations of Hg, Cd, Pb, Zn, Cu, As, Ni, and Cr in samples of soil, cereal, and vegetables from Yangzhong district, China. Compared to subsoils, the sampled topsoils are enriched in Hg, Cd, Cu, Pb, Zn, and As. High levels of Cd and Hg are observed in most agricultural soils. Concentrations of Cr and Ni show little spatial variation, and high Cu, Pb, and Zn contents correspond well to areas of urban development. High As contents are primarily recorded at the two ends of the sampled alluvion. The contents of Cd, Hg, and total organic carbon (TOC) increase gradually to maximum values in the upper parts of soil profiles, while Cr and Ni occur in low concentrations within sampled profiles. As, Pb, Cu, and Zn show patterns of slight enrichment within the surface layer. Compared to data obtained in 1990, Cd and Hg show increased concentrations in 2005; this is attributed to the long-term use of agrochemicals. Cr and Ni contents remained steady over this interval because they are derived from the weathering of parent material and subsequent pedogenesis. The measured As, Cu, Pb, and Zn contents show slight increases over time due to atmospheric deposition of material sourced from urban anthropogenic activity. Low concentrations of heavy metals are recorded in vegetables and cereals because the subalkaline environment of the soil limits their mobility. Although the heavy metal concentrations measured in this study do not pose a serious health risk, they do affect the quality of agricultural products.     

Pressurized CO2/zero valent iron system for nitrate removal

A fluidized zero valent iron (ZVI) reactor pressurized by CO(2) gas for controlling pH was employed for nitrate reduction. The proposed CO(2) pressurized system potentially has advantages of using less CO(2) gas and reaching equilibrium pH faster than CO(2)-bubbled system. However, due to weak acid nature of carbonic acid, system pH gradually increased with increasing oxidation of ZVI and reduction of nitrate. As pH increased with progress of reaction, nitrate removal rate decreased continuously. The results indicate that nitrate removal efficiency increases with increasing initial ZVI dosage but reaches plateau at ZVI doses of higher than 8.25gl(-1), and initial nitrate concentration up to 100mg l(-1) as N has minimal impact on the removal efficiency. Unlike the fluidized system with pH control by strong acid reported in our pervious study, near 100% of nitrogen recovery was observed in the current process, indicating that nitrate reduction by ZVI with different pH controlled mechanisms will have different reaction routes.     

Non-aromatic hydrocarbons in surface sediments near the Pearl River estuary in the South China Sea

Surface sediment samples at 4 sites along an offshore transect from outer continental shelf off the Pearl River estuary to the shelf slope region of the northern South China Sea, have been analyzed for total organic carbon (TOC), total nitrogen (TN), solvent extractable organic matter (EOM) and non-aromatic hydrocarbons. TOC, TN and EOM show distinct spatial variations. Their highest values are all recorded at the shelf slope region. EOM varies from 18.70-38.58 microgg(-1) dry sediment and accounts for 0.20-0.72% of the TOC contents. The non-aromatic hydrocarbons are an important fraction of EOM. Their contents range from 3.43-7.06 microgg(-1) dry sediment. n-Alkanes with carbon number ranging from 15-38 are identified. They derive from both biogenic and petrogenic sources in different proportions. Results of isoprenoid hydrocarbons, hopanes and steranes also suggest possible petroleum contamination.     

Comparative on Causes and Accumulation of Selenium in the Tree-rings Ambient High-selenium Coal Combustion Area from Yutangba, Hubei, China

Toxic trace elements emitted during coal combustion are the main sources of air pollution. They are released into the atmosphere mainly in the forms of fine ash, smoke and flue, and thus adversely affect plant, animal and human health. Selenium is one of toxic and the most volatile in coal. Large amount of atmospheric emission of selenium, as well as selenium present and scrubber stockpiles in ash may create serious environmental problems. In the paper, on the basis of investigating the abundance and distribution of selenium in plant-rings during recent 20 years, the bioaccumulation of selenium is explained that selenium in plant, which were collected from the village of selenium-rich coal combustion, is much higher than that in plants collected away from the village of selenium-rich coal combustion. The main origins of selenium are selenium-rich coal combustion and high-selenium rock weathered. The selenium recycle by food chain and selenium will accumulate and redistribute in environments.     

Polycyclic aromatic hydrocarbons in Dalian soils: distribution and toxicity assessment

Concentrations of 15 polycyclic aromatic hydrocarbons (PAHs) were measured in surface soils collected from Dalian, China, for examination of distributions and composition profiles and their potential toxicity. The sum of 15 PAHs (SigmaPAHs) ranged from 190 to 8595 ng g(-1) dry weight, and showed an apparent urban-suburban-rural gradient in both SigmaPAHs and composition profiles. Using hierarchical cluster analysis (HCA), the sampling sites were grouped into four clusters corresponding to traffic area, park/residential area, suburban and rural areas. The ratios of naphthalene (Nap) and fluorene (Fl) versus fluoranthene (Flu), pyrene (Pyr) and indeno(1,2,3-cd)pyrene (InP) in the four clusters provided evidence of local distillation. The diagnostic ratios indicated the prevalent PAH sources were petroleum combustion and coal combustion in Dalian, and a cross plot of diagnostic ratios distinguished the urban samples from suburban and rural ones. Toxic potency assessment of soil PAHs presented a good relationship with benzo(a)pyrene (BaP) levels, toxic equivalent concentrations based on BaP (TEQ(BaP)) and dioxin-like toxic equivalent concentrations (TEQ(TCDD)). The study highlights that BaP is a good indicator for assessing the potential toxicity of PAHs, and presents a promising toxicity assessment method for soil PAHs.     

Evaluation of nitrification inhibitor 3,4-dimethyl pyrazole phosphate on nitrogen leaching in undisturbed soil columns

The application of nitrogen fertilizers leads to various ecological problems such as nitrate leaching. The use of nitrification inhibitors (NI) as nitrate leaching retardants is a proposal that has been suggested for inclusion in regulations in many countries. In this study, the efficacy of the new NI, 3,4-dimethyl pyrazole phosphate (DMPP), was tested under simulated high-risk leaching situations in two types of undisturbed soil columns. The results showed that the accumulative leaching losses of soil nitrate under treatment of urea with 1.0% DMPP, from columns of silt loam soil and heavy clay soil, were 66.8% and 69.5% lower than those soil columns tested with regular urea application within the 60 days observation, respectively. However, the losses of ammonium leaching were reversely increased 9.7% and 6.7% under the former treatment than the latter one. Application of regular urea with 1.0% DMPP addition can reduce about 59.3%-63.1% of total losses of inorganic nitrogen via leaching. The application of DMPP to urea had stimulated the inhibition effects of DMPP on the ammonium nitrification process in the soil up to 60 days. It is proposed that the DMPP could be used as an effective NI to control inorganic N leaching losses, minimizing the risk of nitrate pollution in shallow groundwater.     

Photoelectrocatalytic degradation of pentachlorophenol in aqueous solution using a TiO2 nanotube film electrode

Titanium dioxide (TiO2) nanotube film electrodes are fabricated by the anodic oxidation method. Scanning electron microscopy (SEM) showed that these tubes were well aligned and organized into high-density uniform arrays. XRD analysis showed the TiO2 nanotubes to be in the anatase crystal form. The TiO2 nanotube film electrode exhibited increased photoelectrocatalytic (PEC) capability compared to a traditional TiO2 film electrode fabricated using the anodizing method for pentachlorophenol (PCP) degradation in aqueous solution. The bias potential, pH value, and electrolyte concentration were shown to be important factors influencing the degradation of PCP by the PEC method using the TiO2 nanotube film electrode as the working electrode.     

In situ studies on the distribution patterns and dynamics of microcystins in a biomanipulation fish--bighead carp (Aristichthys nobilis)

The distribution and dynamics of microcystins in various organs of the phytoplanktivorous bighead carp were studied monthly in Lake Taihu, which is dominated by toxic cyanobacteria. There was a good agreement between LC-MS and HPLC-UV determinations. Average recoveries of spiked fish samples were 63% for MC-RR and 71% for MC-LR. The highest MC contents in intestine, liver, kidney and spleen were 85.67, 2.83, 1.70 and 1.57 microg g-1 DW, respectively. MCs were much higher in mid-gut walls (1.22 microg g-1 DW) than in hind- and fore-gut walls (0.31 and 0.18 microg g-1 DW, respectively), suggesting the importance of mid-gut wall as major site for MC absorption. A cysteine conjugate of MC-LR was detected frequently in kidney. Among the muscle samples analyzed, 25% were above the provisional tolerable daily intake level by WHO. Bighead is strongly resistant to microcystins and can be used as biomanipulation fish to counteract cyanotoxin contamination in eutrophic waters.     

Comparison of China’s Environmental Impact Assessment (EIA) Law with the European Union (EU) EIA Directive

In this paper, we first review the development of China’s Environmental Impact Assessment (EIA) system in the past 30 years. Then we compare the framework and operational procedures of China’s new EIA law with those of the EU EIA Directive. We also compare public participation, as well as sanctions and control in the two EIA systems. In addition, we identify where the processes in both EIA systems are similar or different from one another. By comparison, we noted that there are at least three obvious weaknesses in China’s EIA system: (1) the application of new models for EIA legislation; (2) the improvement of EIA guidance and education; and (3) the enhancement of public participation in EIA process. Our study indicates that these three major shortcomings should be overcome and improved in China’s EIA system, when compared with the EU EIA system.     

Estimation of waste generation from floods

A framework of correlation for estimating the amount of waste generation from floods is developed. Flood waste data were collected from four recent typhoons in Taiwan. Parameters affecting the flood waste are analyzed. Population density, flooded area and amount of total rainfall are chosen as the correlating parameters for the model development, and regression diagnostics are performed to check the validity of the collected data. The simple linear model is shown to be incapable of correlating the flood waste data. An exponential model is proposed and shown to give acceptable correlation with the flood waste data spanning five orders of magnitude. The model can be useful in the planning of waste cleanup after floods.