Influence of acidity level in simulated rain on disease progress in four plant pathosystems

Field investigations were performed in 1984-1985 on the effects of acidity level in simulated rain on disease dynamics in four pathosystems: alfalfa leaf spot (ALS), peanut leaf spot (PLS), potato late blight (PLB), and soybean brown spot (SBS). Studies were performed in an ambient rain exclusion apparatus with simulated rain acidity levels of pH 2.8, 3.6, 4.2, 4.8, or 5.6 and four plots per pH level. In 1984 for ALS and PLB, rain was simulated three times a week at 6-8 mm per event. For PLS and SBS in 1984 and for PLB, PLS, and SBS in 1985, rain was simulated twice a week at 13-16 mm per event with a 10 min pause halfway through each event. Disease was assessed three times a week. In 1984, no significant effect of acidity level in simulated rain on disease severity was detected in any pathosystem. Severity of PLB differed among treatments in 1985 with significant quadratic and cubic components for the dose-response relationship. PLS severity decreased with increasing level of acidity in simulated rain in 1985 and the dose-response relationship was linear. No differences in severity of ALS or SBS due to acidity of simulated rain were found. Thus, disease response to acidity of simulated rain is system dependent.     

WATER USE AND WATER CONSERVATION BY THE COPPER MINING INDUSTRY1

ABSTRACT: This paper examines the use of water by copper mines for treating low grade ores. The froth flotation process for treating sulphide ore and the heap leaching process for treating oxide ore are described, and ways of reducing the amount of water used in these processes are discussed. Estimates of the costs reducing water consumption are given. Finally, the circumstances in which it would be desirable for a copper mine to reduce its level of water consumption are considered.     

Influence of glyphosate and its formulation (Roundup) on the toxicity and bioavailability of metals to Ceriodaphnia dubia

This study examined the toxicological interaction between glyphosate (or its formulation, Roundup) and several heavy metals to a freshwater cladoceran, Ceriodaphnia dubia. We demonstrated that all binary combinations of Roundup and metals (Cd, Cu, Cr, Ni, Pb, Se and Zn) exhibited "less than additive" mixture toxicity, with 48-h LC50 toxic unit > 1. Addition of glyphosate alone could significantly reduce the acute toxicity of Ag, Cd, Cr, Cu, Ni, Pb and Zn (but not Hg and Se). The ratio between glyphosate and metal ions was important in determining the mitigation of metal toxicity by glyphosate. A bioaccumulation study showed that in the presence of glyphosate the uptake of some metals (e.g. Ag) was halted but that of others (e.g. Hg) was increased significantly. Therefore, our study strongly suggests that glyphosate and its commercial formulations can control the toxicity as well as the bioavailability of heavy metals in aquatic ecosystems where both groups of chemicals can co-occur.     

Three Different Topics for Bioremediation Application on Soils and Waters Contaminated with Aromatic Compounds, by Using Immobilized Bacteria

Molecular techniques and modelling are presented as powerful tools required in the performance of efficient soil and water bioremediation systems. An Escherichia coli CC118-D strain was constructed by inserting the Klebsiella pneumoniae hpa B gene, coding for the unstable 3,4-dihydroxyphenylacetate 2,3-dioxygenase, into its chromosome. When the constructed strain was immobilized, both enzyme stability and viability increased along the studied period, in absence of antibiotic. We proposed this strategy as an approach to overcoming plasmid instability and to enhance enzyme activity and stability, avoiding antibiotic utilization. A model was developed to understand and predict the behaviour of bacteria and pollutants in a bioreactor system, considering: fluid dynamics, molecular/cellular scale processes and biofilm formation.     

Genotoxicity is unrelated to total concentration of priority carcinogenic polycyclic aromatic hydrocarbons in soils undergoing biological treatment

A solid-phase microbiological assay was used to determine the changes in genotoxicity associated with sequestration or biodegradation of carcinogenic compounds in contaminated soils. The concentration of six carcinogenic polycyclic aromatic hydrocarbons (PAHs) did not change in 59 d in sterile soil, but the genotoxicity declined markedly. In a soil undergoing bioremediation in the field for 147 d or biodegradation in the laboratory for 180 d, the concentrations either changed little or declined at different rates, but the genotoxicity increased followed by a decline. The genotoxicity of a second soil declined as a result of biological treatment. The data show that genotoxicity of contaminated soils may be unrelated to the concentration of carcinogenic PAHs because of aging or new mutagens formed during biological treatment.     

The combination of chemical,structural, and functional indicators to evaluate the anthropogenic impacts on agricultural stream ecosystems

Environmental Science and Pollution Research - Freshwater contamination by pesticides in agricultural landscapes is of increasing concern worldwide, with strong pesticide impacts on biodiversity,...     

Natural attenuation of chlorinated solvents at Area 6, Dover Air Force Base: characterization of microbial community structure

A polyphasic approach based on cultivation and direct recovery of 16S rRNA gene sequences was utilized for microbial characterization of an aquifer contaminated with chlorinated ethenes. This work was conducted in order to support the evaluation of natural attenuation of chlorinated ethenes in groundwater at Area 6 at Dover Air Force Base (Dover, DE). Results from these studies demonstrated the aquifer contained relatively low biomass (e.g. direct microscopic counts of < 10(7) bacteria/g of sediment) comprised of a physiologically diverse group of microorganisms including iron reducers, acetogens, sulfate reducers, denitrifiers, aerobic and anaerobic heterotrophs. Laboratory microcosms prepared with authentic sediment and groundwater provided direct microbiological evidence that the mineralization of vinyl chloride and cis-dichloroethene as well as each step in the complete reductive dechlorination of tetracloroethene to ethene can occur in the Area 6 aquifer. Enrichment cultures capable of the oxidative degradation of cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC) were obtained from groundwater across the aquifer demonstrating the possible importance of direct, non-cometabolic oxidation of cis-DCE and VC in natural attenuation. Culture-independent analyses based upon recovery of 16S rRNA gene sequences revealed the presence of anaerobic organisms distributed primarily between two major bacterial divisions: the delta subdivision of the Proteobacteria and low-G + C gram positive. Recovery of sequences affiliated with phylogenetic groups containing known anaerobic-halorespiring organisms such as Desulfitobacterium, Dehalobacter, and certain groups of iron reducers provided qualitative support for a role of reductive dechlorination processes in the aquifer. This molecular data is suggestive of a functional linkage between the microbiology of the site and the apparent natural attenuation process. The presence and distribution of microorganisms were found to be consistent with a microbially driven attenuation of chlorinated ethenes within the aquifer and in accord with a conceptual model of aquifer geochemistry which suggest that both reductive and oxidative mechanisms are involved in heterogeneous, spatially distributed processes across the aquifer.