Alkali Soil Reclamation with Flue Gas Desulfurization Gypsum in China and Assessment of Metal Content in Corn Grains

Flue gas desulfurization gypsum (FGDG), the by-product of wet and semi-dry desulfurization processes, has been used as an alkali soil amendment in China. We evaluated the change in soil properties, agricultural production and the safety of FGDG as a soil amendment. As a result, soil pH and ESP (exchangeable sodium percentage) decreased and corn production increased in FGDG-treated plots. The metal (B, Cr, Mn, Ni, Cu, As, Cd, Pb) contents in soil, FGDG, and corn grains were quantified by ICP-MS. Consequently, the contents of almost all metals in FGDG were lower than in soil. Moreover, the contents of almost all of the metals in the corn grains in the FGDG-treated plots were almost the same or lower than those in the control plot. Statistical analysis indicated that there was no effect of gypsum application on the metal content in the corn grains. Almost all of the metal contents were lower than the standard values set by FAO/WHO for human intake. The results showed that the FGDG from wet and semi-dry FGD processes is suitable as an alkali soil amendment.     

Effect of Different Amendments on Growing of Canna indica L. Inoculated with AMF on Mining Substrate

Canna indica L. (CiL) was used here in phytoremediation of mining soils. Our work evaluated the effect of AMF (i) on the growth and (ii) on the uptake of heavy metals (HM). The tests were conducted in the greenhouse on mining substrates collected from the Kettara mine (Morocco). The mine soil was amended by different proportions of agricultural soil and compost and then inoculated with two isolates of AMF (IN1) and (IN2) of different origins. After six months of culture, the results show that on mining soils (100%) only AMF (IN2) was able to colonize the roots of CiL with a frequency of 40 ± 7% and an intensity of 6.5 ± 1.5%. Also, the lowest values of shoot and root dry biomass are obtained on these mining soils with respectively 0.30 g and 0.27 g. In contrast, the accumulation of HM was higher and reached more than 50% of that contained in the mining soils, the highest values with 138 mg kg^?1 Cu²⁺, Zn²⁺ 270 mg kg^?1 and 1.38 mg kg^?1 Cd was recorded. These results indicate that the colonization of CiL roots by AMF (IN2) could significantly improve its potential to be used in phytoremediation of polluted soil.     

Evaluation of Bacterial Community Structure and Its Influence on Sulfide Oxidation in a Bio-Leaching Environment

The mechanism of sulfide oxidation by adhering bacteria (direct oxidation mechanism) and by ferric ion in the aqueous phase was studied by quantitative assessment of bacterial activity on the sulfide surface. To probe for the principal bacterial species on the surface and in the supernatant, a library of DNA genes encoding portions of bacterial 16S rRNA was constructed. The PCR-amplified DNA from the bacterial populations was cloned employing PROMEGA's pGEM-T Easy Vector system. The clone frequency indicated that iron-oxidizing bacteria were dominant in the liquid phase, while Acidithiobacillus ferroixdans, which is both sulfur and iron oxidizer was the most prevalent on the sulfide surface. Samples of crystalline pyrite were exposed to the bacterial consortium to evaluate surface alterations caused by bacteria. Chemical (abiotic) oxidation experiments with ferric ion as the oxidant were carried out in parallel with the biological oxidation tests. Changes in the surface topography were monitored by atomic force microscopy (AFM) while changes in surface chemistry were examined by Raman spectroscopy. Bacterial attachment resulted in a 53% increase in the specific surface area in comparison to a 13% increase caused by chemical (ferric ion) oxidation. The oxidation rate was assessed by evaluating the iron release. After corrections for surface area changes, the specific abiotic (oxidation by Fe^{3 +}) and biotic oxidation rates with adhering bacteria were nearly the same (2.6 × 10^{? 9} mol O₂/s/m² versus 3.3 × 10^{? 9} mol O₂/s/m²) at pH = 2 and a temperature of 25°C. The equality of rates implies that the availability of ferric ion as the oxidant is rate limiting.     

Safety Risk Assessment of Iran's Underground Coal Mines Based on Preventive and Preparative Measures

Mining is one of the most hazardous occupations all around the world, especially in underground coal mines. Analysis and management of safety risk are prerequisites toward control and increment in mines' safety. Common safety risk analyses in mines are based on the statistical data of the occurred incidents and economical aspects are usually neglected. In this study, based on a novel procedure and presentation of preventive and preparative measures, safety risk of Iran's underground coal mines' incidents was assessed and classified by taking advantage of Iran's mining experts' opinions. Among 10 significant identified incidents, methane explosion, coal dust explosion, and traffic accidents accounted for the highest levels of safety risk before adjustment, respectively. The most hazardous incidents in the adjusted risk mode were the same, but in a reverse order. Application of safety measures in three modes of preventive adjustments, preparative adjustment and both of them caused some risk reduction with the mean values of 67, 21, and 75%, respectively, thereby indicating the importance of safety risk management in underground coal mines and the preference for preventive measures in this area.     

Pyridine and other coal tar constituents as free radical-generating environmental neurotoxicants

Summary We have tested the hypothesis that chronic exposure to the principal constituents of the aqueous fraction of coal tar extracts can lead to the in vivo formation of substances which may produce neurological damage as the result of free radical generation and lipid peroxidation, these may be involved in the etiology of some neurological disorders. Artificial mixtures of the aqueous fraction of coal tar extracts were given in low concentrations to pigmented mice in their drinking water over a 3-month period. This resulted in significant increases in lipid peroxidation in the striatum, cerebellum and liver of the mice under test, the rank order being striatum > cerebellum > liver. These results are compatible with the possibility that coal tar emissions (as would be recovered or liberated in the burning, refining or beneficiation of coal) constitute a potential source of neurotoxicants with a predilection for damaging the nigrostriatal neuronal pathway. Our observations may thus have identified an important and hitherto unsuspected environmental source of neurotoxic chemicals, a possibility consistent with the proposed involvement of an environmental chemical factor in Parkinson's disease and perhaps in other neurological disorders.