Magnesium Contamination in Soil at a Magnesite Mining Region of Liaoning Province, China.

Magnesite is the world's most important source material for magnesia refractory production, and Haicheng City in Liaoning Province, China has been called "the magnesium capital of the world." However, magnesite mining in these areas has caused serious environmental problems. Field investigations have shown that the soil profile of many sites in the mining region are contaminated by magnesium, and the magnesium-enriched crusts that have formed on the soil surface have affected ecologically important soil functions, particularly reduced water penetration rate. Laboratory experiment revealed that anionic polyacrylamide and calcium dihydrogen phosphate can be used to improve soil condition, and have positive effects on soil function. The findings of this study are of significance in the magnetite mining areas, providing clear options for the remediation of soils that should be carried out immediately.

Effects of sulfur dioxide pollution on the translocation and accumulation of heavy metals in soybean grain.

BACKGROUND: Open-top chambers were used to study the impact of simultaneous exposure to atmospheric SO(2) pollution and heavy metal contamination in soils on the metal contents and productivity of soybean plant. METHODS: Plants were exposed at ambient levels as control SO(2) (1.2 ppb), low SO(2) (97 ppb), and high SO(2) (490 ppb) over the whole growing season while simultaneously being exposed to either Cd (0.5 mg kg(-1)), Pb (250 mg kg(-1)), Cu (100 mg kg(-1)), or Zn (150 mg kg(-1)) in soil. RESULTS: This experimental study covering the whole growth season has shown that SO(2) has a synergistic effect in enhancing the heavy metal contents in aboveground tissues of soybean plant, and the effects of high SO(2) treatment were found to be highly significant, showing increases of 42% and 29% for Cu and Cd content of grain, respectively. CONCLUSION: The research findings are of practical significance in the environmental control for the combined pollution of air and soil to ensure the quality of agricultural products and therefore benefits for human health.

Distribution and migration of nitrobenzene in water following a simulated spill.

Releases of nitrobenzene into the aquatic environment pose a threat to human health and aquatic resources, and have attracted much attention world-wide. In order to find out the distribution and migration patterns of pooled nitrobenzene underwater in different conditions, laboratory column experiments were designed to simulate stagnant water, flowing water and rainfall disturbance events. The results showed that in stagnant water there was a slow diffusion of the nitrobenzene from the pool leading to higher concentrations of the chemical deeper in the water column. In flowing water, the removal of the substance was rapid and water concentrations were much lower and more uniform throughout the column. The disturbance event brought a substantial quantity of nitrobenzene into the water column which then dissipated according to the flow regime. Analysis of the data showed that distribution pattern of nitrobenzene in the stagnant water column followed a logarithmic equation C(NB) = a ln(t) + b, and in disturbed flowing water, the distribution pattern of nitrobenzene followed a negative exponential regression equation C(NB) = Ne(-Mt). These conclusions have practical significance in developing remediation technologies for water polluted by nitrobenzene.

Risk assessment of heavy metals in soil previously irrigated with industrial wastewater in Shenyang, China.

The Zhangshi Irrigation Area (ZIA) in Shenyang, China has been irrigated by industrial wastewater since 1962. Since then, parts of the ZIA have been rezoned for industrial uses, but the remaining area, named Sluice Gate III (SLIII) and Lower Reaches (LR), still occupies 1825ha. Although land irrigation with industrial wastewater ceased in 1992, a study on heavy metals in soils was carried out to assess the feasibility of agricultural crop cultivation in SLIII and LR. A detailed field investigation was conducted and both total heavy metal concentrations and bioavailable fraction in soil were determined. The results have highlighted that Cd concentrations in soils still exceed the Environmental Quality Standard for Soil in China (GB15618-1995) grade C standard in SLIII region, and grade B standard in LR. In the SLIII, Zn and Pb concentrations in soil are higher than the grade A standard, although Cu is close the grade A standard. In SLIII the dominant chemical fractions were the exchangeable and carbonatic forms, which represent up to 43% and 35% of the Cd, respectively. The Cd in these two fractionations poses the highest risk for the plant absorption and accumulation. Therefore the SLIII should be abandoned for cultivated crops to prevent the Cd contamination of food chain and any associated hazards to human health.

Studies on the sources of benzo[a]pyrene in grain and aboveground tissues of rice plants.

Rice plant pot experiments designed to identify benzo[a]pyrene (B[a]P) sources in plant tissues were conducted in an air-quality controlled greenhouse built to prevent contamination from B[a]P air pollution. Results from quartz sand cultures with control and 50, 100 and 500 microgkg(-1) of B[a]P treatments were compared with those from outdoor field experiments, in which rice plants were exposed to polluted air in the urban area of Shenyang, China. When B[a]P was strictly controlled in both air and quartz sand culture medium, the background values of B[a]P in rice plant tissues were uniformly very low. There was no significant difference of B[a]P contents of rice grain between control and treatments of B[a]P in controlled air quality trials. This indicated that the source of B[a]P in the rice grains is not from any B[a]P in the root culture media. The B[a]P content of rice grain, husk, and stem with leaf sampled from outdoor field was up to 7.33-, 9.21- and 27.10-fold higher than corresponding tissues from air-quality controlled conditions. This indicated that polluted air is the main source of B[a]P in aboveground tissues. Therefore control of B[a]P pollution in ambient air is of prime importance for improving the quality of cereal crops.

Optimization of laccase production from Trametes versicolor by solid fermentation.

The regulation of culture conditions, especially the optimization of substrate constituents, is crucial for laccase production by solid fermentation. To develop an inexpensive optimized substrate formulation to produce high-activity laccase, a uniform design formulation experiment was devised. The solid fermentation of Trametes versicolor was performed with natural aeration, natural substrate pH (about 6.5), environmental humidity of 60% and two different temperature stages (at 37 degrees C for 3 days, and then at 30 degrees C for the next 17 days). From the experiment, a regression equation for laccase activity, in the form of a second-degree polynomial model, was constructed using multivariate regression analysis and solved with unconstrained optimization programming. The optimized substrate formulation for laccase production was then calculated. Tween 80 was found to have a negative effect on laccase production in solid fermentation; the optimized solid substrate formulation was 10.8% glucose, 27.7% wheat bran, 9.0% (NH4)2SO4, and 52.5% water. In a scaled-up verification of solid fermentation at a 10 kg scale, laccase activity from T. versicolor in the optimized substrate formulation reached 110.9 IU/g of dry mass.

Optimization of cellulase complex formulation for peashrub biomass hydrolysis.

To improve efficiency and reduce cost, solid state simultaneous saccharification and fermentation of peashrub woody biomass was investigated under anaerobic conditions at 50 degrees C, with a cellulase-inoculant mixture consisting of Trichoderma koningii cellulase, Aspergillus niger cellulase, and Lactobacillus. Experimental formulations were prepared according to uniform prescription design principles. By crude protein, crude fiber models constructed using multivariate regression in SPSS and solutions analysis through unconstrained mathematical optimization in Microsoft Excel, it was clearly revealed that low pH value (3.8) from lactic acid accumulation produced by Lactobacillus would ultimately limit enzymatic hydrolysis during long-term fermentation (30 days). It was shown that a cellulase complex with filter paper cellulase/carboxymethyl cellulase/cotton lyase/beta-glucosidase/pectinase of activity ratios of 0.6:1:0.3:1:2.6 could effectively break peashrub cell wall structure by biodegradation of easily digested components and, then, release cellular contents to improve crude protein content. Thus, the enzymatic hydrolysis of peashrub biomass by the optimized cellulase complex could improve crude protein content by 45.3% (from 8.45 to 12.28%), although it only biodegraded about 10.90% of the crude fiber (from 44.45 to 40.08%).

Biodegradation of benzo[a]pyrene in soil by Mucor sp. SF06 and Bacillus sp. SB02 co-immobilized on vermiculite.

Two indigenous microorganisms, Bacillus sp. SB02 and Mucor sp. SF06, capable of degrading polycyclic aromatic hydrocarbons (PAHs) were co-immobilized on vermiculite by physical adsorption and used to degrade benzo[a] pyrene (BaP). The characteristics of BaP degradation by both free and co-immobilized microorganism were then investigated and compared. The removal rate using the immobilized bacterial-fungal mixed consortium was higher than that of the freely mobile mixed consortium. 95.3% of BaP was degraded using the co-immobilized system within 42 d, which was remarkably higher than the removal rate of that by the free strains. The optimal amount of inoculated co-immobilized system for BaP degradation was 2%. The immobilized bacterial-fungal mixed consortium also showed better water stability than the free strains. Kinetics of BaP biodegradation by co-immobilized SF06 and SB02 were also studied. The results demonstrated that BaP degradation could be well described by a zero-order reaction rate equation when the initial BaP concentration was in the range of 10-200 mg/kg. The scanning electronic microscope (SEM) analysis showed that the co-immobilized microstructure was suitable for the growth of SF06 and SB02. The mass transmission process of co-immobilized system in soil is discussed. The results demonstrate the potential for employing the bacterial-fungal mixed consortium, co-immobilized on vermiculite, for in situ bioremediation of BaP.

A comparative study of classical and biochemical endpoints for phytotoxicity testing of chlorobenzoic acids.

The phytotoxicity of chlorobenzoic acids (CBAs) was studied and the biochemical endpoints' suitability and sensibility was evaluated. Two terrestrial plant species in the same family were exposed to different concentrations of CBAS and tested their germination according to the guideline of Organization for Economic Cooperation and Development (OECP, 1984). The results showed that CBA dose-inhibition rate of classical endpoint had the distinct linear relationship in the range of 10%-50% inhibition rate for root elongation (p < 0.01), and the dose variances of CBAs had the greater influence on the inhibition rate of germination than on inhibition rate of root elongation. The CBA dose half effect concentration-inhibition rate of two antioxidant enzyme activity superoxide dismutase (SOD) and catalase (CAT) had the quadratic relationship, and CBA dose-inhibition rate of the peroxides (POD) activity had the linear relationship (p < 0.05). Comparing the half effect concentration (EC50) of two kinds of endpoints, the POD activity was more sensitive than classical endpoint, however, SOD and CAT activity were not sensitive in the experiment.

[Application of wastewater land treatment technique to the construction of ecological engineering in sand land].

In this paper studies on the feasibility of harmlessness and resource of wastewater, which was discharged from a thermal power plant, by using slow rate filtration of land treatment technique for the fast recovery of vegetation in the Kubuqi sand land were carried out. The selected arbor, shrub and herbage in the land treatment system were poplar (Populus alba Var. Pyramidalis bunge), seabuckthorn (Hippophae rhamnoides) and sweet clover (Melilotus suaveolens) respectively. Three levels of wastewater hydraulic loading were designed in the field pilot experiment. They were high plot with 3000 mm/a irrigation (H), medium plot with 1500 mm/a irrigation (M) and low plot (L) with small volume of irrigation only used in the period of transplant seedlings. The performance indicate that the purification function of power plant wastewater by pre-treatment through combination of precipitation pool with storage ponds is effective and therefore the effluent after pretreatment can be used to irrigation vegetation. The experiment results show that the volume of tree crown for poplar in H plot and M plot was up to 1.07 and 2.21 times comparing with L plot respectively. The annual yield (dry weight) of sweet clover in H plot and M plot was up to 2.33 and 3.0 times comparing with L plot respectively. The height of seabuckthorn in H zone and M plot was up to 1.08 and 1.32 times comparing with L plot respectively. There is direct proportion between growth status of vegetation and hydraulic loading of irrigation. The contents of heavy metals for sweet clover (Cd 0.021 mg/kg, Pb<0.001 mg/kg, Cr <0.01 mg/kg, As 0.043 mg/kg) are much lower than the food standards of grain and vegetables, therefore the sweet clover for raising livestock is safe. Wastewater in this area is valuable source. Its reasonable utilization can contribute important benefits in economy and ecology in the ecological construction and developing effective agriculture and animal husbandry.

The practical value of applying chemical biliary duct embolization to chemical hepatectomy for treatment of hepatolithiasis.

BACKGROUND: The high recurrence rate of hepatolithiasis, together with the high operative risk of hepatectomy for specifically located stones, has not been effectively settled until now. Thus, the aim of this study was to investigate the feasibility and effectiveness of using chemical biliary duct embolization (CBDE) to achieve chemical hepatectomy in a rabbit model of hepatolithiasis. MATERIALS AND METHODS: The animal model of hepatolithiasis was established using the methods of obstruction plus infection. Seven days later, the left hepatic ducts were embolized using phenol plus cyanoacrylate or absolute ethanol plus cyanoacrylate. Subsequently, the influence of CBDE on bile duct, liver, and stone formation was analyzed by histology, RT-PCR for procollagen, biochemistry, and enzymatic histochemistry for beta-glucuronidase (beta-G). RESULTS: CBDE resulted in the entire ablation of the diseased biliary duct mucosa and the complete occlusion of the diseased biliary duct lumen, thus effectively eradicating chronic proliferative cholangitis and preventing stone formation. More importantly, CBDE also resulted in the complete fibrosis and "self-cut" in the periphery of the embolized lobe, thus achieving chemical hepatectomy. Also of note, the embolized lobe exhibited a much lower level of endogenous beta-G than the nonembolized lobe, indicating an inhibitory effect of CBDE on beta-G. Besides, the mRNA level of procollagen I in the embolized bile duct wall of phenol embolization group was significantly higher than the ethanol embolization group. CONCLUSION: Chemical biliary duct embolization, especially using phenol plus cyanoacrylate, may prevent the recurrence of intrahepatic stone and concurrently achieve the effect of chemical hepatectomy.

[Application of terrestrial invertebrates biomarkers in soil pollution ecology study].

Biomarkers in terrestrial invertebrates play an important role in estimating either exposure or resultant effects of pollutants in soil ecosystem, which has received increasing attention and made significant progress. The present paper has drawn three important biomarkers, i.e., lysosomes, stress protein and mettllothioneins (MTs). The lysosomal membrane stability of coelomocytes was assayed as neutral-red retention time (NRR-time) resulting from toxicant stress. Hsp70 and Hsp60 were commonly used in the stress protein families. The quantification methods of different isofoms of the mettllothioneins could specifically indicate different metal contamination. The rationale, characteristics, and relevant exemplary case of assaying the biomarkers and their promising application to ecotoxicological diagnosing in soil contamination were discussed.