Estimation of mercury content in tailings of the gold mine area of Poconé, Mato Grosso,Brazil

As in many other parts of the world, gold is produced in the surface mining region of Poconé, Mato Grosso, Brazil, using mercury. The goal of this investigation was to estimate the amount of mercury in certain tailings and to determine the area of the land that has been contaminated by the gold mining operations. Mercury concentrations from 2 to 495 ng/g (dw) were determined in the tailing materials. It was observed that only isolated sites were acting as central points of contamination. Using digital Landsat satellite data (The-matic Mapper) and aerial photos, the sites degraded by the mining were classified, and their total area was estimated to be 12.3 km² in the region of Poconé. It was estimated, that 4.9 km² were occupied by the contaminated tailings. The mean height of the pile slags was determined to be 4.5 m. From the experimentally calculated average density of the material in the tailings, 2.01 g/cm³, the total mercury content in the piles of tailings was estimated to be 1600 ± 350 kg.     

The metabolization of lindane in a culture of mould and the degradation scheme of lindane

The metabolism of Lindane, gamma-Pentachlorcyclohexene and isomeric Tetrachlorobenzenes in a culture of Mould was investigated in this work. 1,2-, 1,4-Dichlorobenzene, 1,2,3-, 1,2,4-, 1,3,5-Trichlorobenzene, 1,2,3,4-, 1,2,4,5- and/or 1,2,3,5-Tetrachlorobenzene, Pentachlorobenzene, gamma-Pentachlorocyclohexene, Hexachlorobenzene, Tetrachlorocyclohexenol, 2,3,4-, 2,4,6-Trichlorophenol, 2,3,4,5-, 2,3,4,6- and/or 2,3,5,6-Tetrachlorophenol and Pentachlorophenol could be identified as metabolites of Lindane. A degradation scheme is proposed. It includes gamma-Pentachlorocyclohexene, Hexachlorocyclohexene, Pentachlorocyclohexenol, Tetrachlorocyclohexenol and Polychlorophenols as main metabolites. The pathway based on many earlier published experimental results of these and other authors so far as possible.In former papers we have already reported about the known literature concerning the metabolism of Lindane (1 – 4).Comprehensive studies about the metabolism of Lindane in cultures of mould (1, 5, 6), in rats (7 – 9), and in men (2, 3) are to contribute in explaining away any uncertainties about the degradation of Lindane. Many investigations contributed to work out degradation schemes of Lindane (10 – 21).     

Effects of open-top chamber fumigations with ozone on three fungal leaf diseases of wheat and the mycoflora of the phyllosphere

Spring wheat (Triticum aestivum L. cv. Turbo) was exposed in open-top chambers to six different ozone levels (8-h daily means from 12.4 to 122 microg m(-3)), to non-filtered air and to chamberless field conditions for 31 days from seedling stage through ear emergence. Powdery mildew (Erysiphe graminis DC. f.sp. tritici Marchal) which developed during the exposure period was significantly enhanced from 0.3/0.6% (two chamber replicates), 1.2/2.1%, 0.9/2.2% in charcoal-filtered air (CF) to 1.5/1.6%, 3.7/4.3%, 4.4/4.6% at the highest level of ozone, on the flag leaf, second and third leaf position, respectively. Post-exposure inoculation with Septoria nodorum Berk. led to increases of disease severity on the flag leaf from 40.9/43.6% in CF to 66.3/70.6% at the highest ozone concentration and on the ears from 15.7/16.5% to 26.3/26.6%. In the same comparison, severity of spot blotch following inoculation with Bipolaris sorokiniana (Sacc.) Shoem. (syn. Helminthosporium sativum Pamm., King et Bakke) was increased on the flag leaf from 3.6/8.9% to 12.3/23.4%. The three diseases examined correlated significantly with the ozone treatments in fumigated chambers. Disease severity was enhanced even on undamaged plant tissue (flag leaves). Infections of the two facultative pathogens on lower leaf positions started only in part from visible ozone lesions, mildew did not start from such lesions. No significant effects of ozone in the chambers on the saprobial colonization of the phyllosphere were detected, whereas there were marked differences in this respect between plants from the field and the chambers. At the highest ozone treatment, contents of chlorophyll a and carotenoids on the second leaf position declined significantly, which was associated with symptoms of premature senescence. Senescing effects of ozone are therefore assumed to be one major factor in predisposing wheat for necrotrophic leaf pathogens. Surprisingly, injurious and predisposing effects of ozone were completely absent in chambers supplied with non-filtered air containing ambient ozone at doses equivalent to those in CF + ozone chambers. Evidently, biological effects of ozone in pure air and in ambient air may differ markedly.