Distribution and assessment of Pb in the supergene environment of the Huainan Coal Mining Area,Anhui, China

Coal mining area is highly subject to lead (Pb) pollution from coal mining activities. Several decades of coal mining and processing practices in dozens of coal mines in the Huainan Coal Mining Area (HCMA) have led to the accumulation of massive amounts of coal gangue, which piled in dumps. In order to investigate the impacts of coal gangue dumps on Pb level in the supergene media of the HCMA, a systematic sampling campaign comprising coal gangue, soil, wheat, and earthworm samples was conducted. The average Pb content in the coal mining area soil is 24 mg/kg, which is slightly higher than the associated coal gangues (23 mg/kg) and markedly higher than reference region soil (12.6 mg/kg). Soil in the HCMA present a slight to moderate Pb contamination, which might be related to the weathering and leaching of coal gangue dumps. Lateral distribution of Pb in HCMA soil differed among individual coal mines. The soil profile distribution of Pb depends on both natural and anthropogenic contributions. Average Pb content is higher in roots than in stems, leaves, and wheat husks, while the Pb level in seeds exceeded the maximum Pb allowance for foods (Maximum Levels of Contaminants in Foods of China, GB 2762–2012). Earthworms in the selected area are significantly enriched in Pb, suggesting higher bio-available Pb level in soil in the HCMA.     

Remediation of contaminated soil by a solvent/surfactant system

This study investigates a new approach using a solvent/surfactant-aided soil-washing process to improve the performance of conventional surfactant-aided soil remediation. Three surfactants (Brij 35, Tween 80, and SDS) and three organic solvents (acetone, triethylamine, and squalane) were used to evaluate the desorption performances of 4,4'-dichlorobiphenyl (DCB) out of three soils with different sorption characteristics. The performance improvement is likely due to better dissolution of the hydrophobic contaminants from the soil assisted by the solvent, and the formation of solvent-incorporated surfactant micelles, which increases both the size (i.e. capacity) and affinity of micelles for more effective contaminant extraction. The foc of soils were found to be important in determining the performance of a solvent/surfactant-aided soil-washing process. Judging from the experimental data and as verified by the two constants in the proposed soil-washing model, as the organic solvent is coexisting with the surfactant micelles, both the marginal soil-washing performance (right after the use of a very small amount of solvent compared to that of none) and the final soil-washing capacity are increased compared to those of a pure surfactant-aided washing process.     

The effect of thallium on the growth of Lemna minor and plant tissue concentrations in relation to both exposure and toxicity

The effect of thallium on frond production and the rates of increase in surface area and fresh weight in Lemna minor were examined in terms of concentrations of the element in the growth medium and in the plant. The toxicity indices, EC(50) and threshold concentration, indicate that curtailment of frond expansion occurs at a lower thallium exposure than inhibition of frond multiplication. Production of smaller fronds, rather than chlorosis, was the most notable initial response to thallium stress and, below the threshold of toxicity, enhanced multiplication rates were recorded. Subsequent recovery in thallium-free medium was significant in the region of EC(50) exposures and below, but very little recovery occurred at higher exposures. Lemna minor has a remarkable capacity to accumulate thallium, and accumulation factors of 88 x 10(3) at low exposures, and 6 x 10(3) at high exposures, were recorded, which would suggest some form of active uptake.     

Chromium accumulation,transport and toxicity in plants∗

The predominant pathway for human exposure to chromium in non‐occupationally exposed individuals is via food with a daily intake of around 30–100 μgd^–1, with vegetables providing a major contribution. Unlike reports of chromium essentiality to man and animals, plants appear not to require chromium in spite of some early reports of a stimulatory growth effect.

Most reports on chromium in plants have been concerned with their growth on soils amended with sewage sludge, pF‐ash, tannery waste, or on ultra basic soils, which contain extreme concentrations of the element. Experimental studies with plants grown in hydroponic solution have often been undertaken at unrealistically high concentrations to examine the uptake of chromium in various forms, either as CrIII or CrVI at different pHs. In most cases, reports on chromium in plants deal with element concentrations and plant/soil relationships rather than detailed biochemical and physiological processes.

In general, chromium is largely retained in the roots of plants, although the oxidation state of chromium, pH, presence of humates and fulvates and plant species, affect plant uptake and transport. Leaves usually contain higher concentrations than grains. The uptake of CrIII is largely a passive process, whereas CrVI uptake is a metabolically mediated process via the sulphate pathway and is thus readily transported around the plant. The presence of a compound similar to trioxalate CrIII has been recorded while little chromium has been reported to be associated with cell organelles or soluble proteins.     

Testing of coloured samples for toxicity by the algal-ATP bioassay microplate technique

Algal-ATP bioassay is a relatively simple, inexpensive, reliable and fast testing procedure for toxicity assessment. This algal growth inhibition bioassay technique using Selenastrum capricornutum was used to assess the toxicity levels in pulp and paper mill and thermomechanical mill effluent samples. Pulp and paper mill and thermomechanical mill effluent samples contain a wide range of colours due to certain physico-chemical properties of the test samples. The optical densities of the samples ranged from 0.27 to> 2.0 (a 600 nanometer). The colour variations in the test samples may interfere with ATP measurements. This paper presents data on the nature of interferences due to certain physico-chemical properties of the test sample and the usefulness of developed controls to overcome the problems for a more realistic toxicity assessment of coloured waste samples.     

The system design of UV-assisted catalytic oxidation process--degradation of 2,4-D

Unlike the conventional first- or second-order model, a novel approach to design for the removal of 2,4-dichlorophenoxy (2,4-D) by the UV-catalytic oxidation process (UVCOP) was investigated. Two distinctive parameters, initial decay rate and maximum oxidative capacity, were characterized. By using these parameters, the performance of the degradation of 2,4-D by UVCOP regarding to the reagent dosages could be successfully predicted. Low concentrations of ferrous ion was found to be a rate-limiting factor for the process while the dosage of hydrogen peroxide was concluded as a dominant species in determining the maximum oxidation capacities. This information can be used to optimize the treatment process and achieve the expected performance target; an "optimal-dose model" was developed accordingly. The model is an intelligent and useful tool to evaluate the optimal doses of hydrogen peroxide with the minimum dose of ferrous ion, which leads to a better design of the treatment process.     

FLOW ANALYSIS OF LANDSLIDE DAMMED LAKE WATERSHEDS: A CASE STUDY1

Abstract: The Chi-Chi earthquake, which occurred on September 21, 1999, and had a magnitude of 7.3 on the Richter scale, resulted in an extensive landslide that blocked the Ching-Shui Creek in Taiwan, forming a large lake with a storage volume of 40 million m³. This paper describes an analytical procedure used to perform flow analysis of the Tsao-Ling watershed, which includes the new landslide dammed lake. In this study, a digital elevation model was applied to obtain the watershed geomorphic factors and stage-area storage function of the landslide dammed lake. Satellite images were used to identify the landslide area and the land cover change that occurred as a result of the earthquake. Two topography-based runoff models were applied for long term and short term streamflow analyses of the watershed because the watershed upstream of the landslide dam was ungauged. The simulated daily flow and storm runoff were verified using limited available measured data in the watershed, and good agreement was obtained. The proposed analytical procedure for flow analysis is considered promising for application to other landslide dammed lake watersheds.     

Metabolism of DDT in Different Tissues of Young Rats

The bioconcentration and distribution pattern of p,p′-DDT 1,1,1-1trichloro-2,2-bis(2-chlorophenyl-4-chlorophenyl)-ethane] and its main metabolites (p,p′-DDD [1,1-dichloro-2,2-bis (4-chlorophenyl) ethane] and p,p′-DDE [1,1-dichloro-2,2-bis (4-chlorophenyl) in adipose tissue, liver, brain, kidney, thymus, and testis were examined in young rats after 10 days of intraperitoneal injection of 50 and 100 mg of p,p′-DDT/kg of body weight. Analyses were performed by high-resolution gas chromatography. p,p′-DDT was found to be accumulated in a dose-dependent manner with the highest concentration in adipose tissue. However, in brain, the accumulation of pesticide was low and remained unchanged at the higher dose. This difference may relate to the protective role of the blood-brain barrier, which limits the access of the xenobiotic in the cerebral compartment, and to the differential tissue lipid composition. Although tissues concentration of p,p′-DDE and p,p′-DDD correlated positively to total p,p′-DDT levels, the active role in detoxification of pollutants may explain why p,p′-DDD is more abundant in liver than in the rest of organs. On the contrary, in brain, the concentration of p,p′-DDE is higher than that of p,p′-DDD, suggesting that the metabolism of the parent insecticide proceeds via more than one pathway.     

Receptor modeling for analyzing PCDD/F and dioxin-like PCB sources in Hong Kong

A total of 96 ambient air samples were collected from January 2004 to December 2004 for the investigation of dioxins (polychlorinated dibenzo-para-dioxins and polychlorinated dibenzofurans [PCDD/Fs]) and dioxin-like profile for polychlorinated biphenyls (PCBs) in the atmosphere of Hong Kong. Two-day back-trajectories were obtained using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model from National Oceanic and Atmospheric Administration (NOAA) Air Resources Laboratory. Receptor models – potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) – were built based on the measured PCDD/Fs and dioxin-like PCBs total toxic equivalent (TEQ) concentrations. Both models were modified in this study so as to integrate the information obtained from three sampling sites in Hong Kong. The PSCF modeling resolved two main PCDD/F and dioxin-like PCB polluting paths from Mainland China. In line with previous studies, the northerly path around the Pearl River Delta might be one of the pollution sources of Hong Kong air. On the other hand, the receptor models also indicated another potential northeasterly source from Yangtze River Delta, which was seldom mentioned as the source region of Hong Kong air. Results from the CWT modeling suggested that the most toxic air mass affecting Hong Kong is probably attributable to the northeast path rather than the north path.