Dissipation of DDT in a heavily contaminated soil in Mato Grosso, Brazil

After the prohibition of organochlorine-pesticide use in Brazil for controlling insect vector diseases, Mato Grosso State gathered the exceeding DDT and stored it irregularly in an open air area that belongs to the National Health Foundation, causing soil contamination. This study aimed to evaluate the contamination level and dissipation of p,p'-DDT and p,p'-DDE in this area. For that, surface soil samples were collected on 19 September 2000, 15 December 2000, 4 April 2001 and soil samples 30-40 cm; 60-70 cm and 90-100 cm deep were taken from five points in the studied area on 17 July 2001. The contaminants were determined by a small scale method which consists on extraction and clean-up steps combined into one step by transferring soil samples mixed with neutral alumina to a chromatographic column prepacked with neutral alumina and elution with hexane:dichloromethane (7:3 v:v). The eluate was concentrated and the analytes were quantified by gas chromatography with an electron-capture detector. p,p'-DDT at surface soil ranged from 3,800 to 7,300 mg kg(-1). 30-40 cm deep soil sample concentrations varied from 0.036 to 440 mg kg(-1) while 90-100 cm deep samples varied from 0.069 to 180 mg kg(-1). Volatilization is probably the main dissipation process. The p,p'-DDT is moving slowly downward in the soil profile, however, the levels of this contaminant are high enough to present risk to underground waters.     

Coupling of 2,4,6-trinitrotoluene (TNT) metabolites onto humic monomers by a new laccase from Trametes modesta

During degradation of trinitrotoluene (TNT) by Trametes modesta, addition of humic monomers prevented the accumulation of all major stable TNT metabolites (aminodinitrotoluenes [AMDNT]) by at least 92% in the presence of 200 mM ferulic acid and guaiacol. Acute toxicity tests with individual TNT metabolites and in T. modesta cultures supplemented with 200 microM TNT demonstrated that the TNT biodegradation process lead to less toxic metabolites. Toxicity decreased in the order TNT>4-HADNT (4-hydroxylaminodinitrotoluene)>2-HADNT>2,6-DNT (2,6-dinitrotoluene)>2',2',6,6-azoxytetranitrotoluene>4-AMDNT>2-AMDNT>2,4-diamninonitrotoluene (2,4-DAMNT) while 2,4-DNT and 2,6-DAMNT were the least toxic. Ferulic acid is the best candidate for immobilization TNT biodegradation metabolites since it prevented the accumulation of AMDNTs in cultures during TNT biodegradation and its products were less toxic. All humic monomers were very effective in immobilizing 2-HADNT [100%], 4-HADNT [100%] and 2,2,6,6-azoxytetranitrotoluene [100%]. Two distinct laccase isoenzymes (LTM1 and LTM2) potentially involved in immobilization of TNT degradation products were purified to electrophoretic homogeneity. LTM1 and LTM2 have molecular weights of 77.6 and 52.5 kDa, are 18% and 24% glycosylated, have pI values of 3.6 and 4.2, respectively. Both enzymes oxidized all the typical laccase substrates tested. LTM1 showed highest kinetic constants (K(m)=0.03 microM; K(cat)=8.8 4x 10(7)s(-1)) with syringaldazine as substrate.     

Reductive dehalogenation of tetrabromobisphenol-A by sediment from a contaminated ephemeral streambed and an enrichment culture

This study was aimed at improving our understanding of the physiology of the microorganisms that reductively dehalogenate tetrabromobisphenol-A (TBBPA). Activity was followed in contaminated sediments from a polluted streambed as well as from fracture filling material underlying the stream. Reductive dehalogenation was observed in surface sediments but not in fracture filling samples from a depth of 3m. Likewise, anaerobic microbial activity, represented by sulphate reduction, was much higher in the surface sediment. In the culture enriched from the surface sediment, optimal microbial debromination of TBBPA took place at a salinity of 2% and 3% NaCl, temperature of 30 degrees Celsius, and pH of 7-8. Ethanol, pyruvate and the combination of hydrogen with acetate were the most suitable electron donors and carbon sources for this culture. Alternative electron acceptors like Fe(3+), SO(4)(2-), SO(3)(2-), NO(3)(-) and 2,4,6-tribromophenol inhibited TBBPA debromination. The debrominating bacteria were heat sensitive (80 degrees Celsius, for 10min) but were not inhibited by bromoethanesulphonate or molybdate. This study allowed optimisation of our culturing conditions, but was also important for understanding the factors which influence TBBPA debromination in situ.     

Polycyclic aromatic hydrocarbons (PAHs) in the aerosol in Beijing, China, measured by aminopropylsilane chemically-bonded stationary-phase column chromatography and HPLC/fluorescence detection

We developed a useful analytical method for the determination of polycyclic aromatic hydrocarbons (PAH) concentrations in the aerosol of China. We used an accelerated solvent extraction (ASE) method for the extraction of PAHs from the aerosol samples, in order to reduce the extraction time and the solvent volume used. The optimum purification method was developed, with aminopropylsilane chemically-bonded stationary-phase column chromatography, in order to remove many co-extractives which cannot be removed by conventional purification methods using silica-gel column chromatography. HPLC/fluorescence detection (FLD) was adopted as the analytical method, because it has very high sensitivity to PAH and it is easy to install, operate, and maintain as compared with GC/MS. With the analytical method developed in this study, the recovery and precision (RSD) for most of the PAHs ranged from 75% to 129% and from 2.8% to 22.7%, respectively. The concentrations of PAHs in the aerosol samples collected from October 2003 to April 2005 in Beijing, China were determined using the newly developed method. SigmaPAHs, which is the sum of the concentrations of all detected PAHs, was 177.8 +/- 239.9 ng m(-3) (n = 64). The SigmaPAHs concentration in the heating season (305.1 +/- 279.0 ng m(-3), n = 33) was 7.2 times higher than that in the non-heating season (42.3 +/- 32.0 ng m(-3), n = 31). These strong seasonal variations in atmospheric PAH concentration are possibly due to coal combustion for residential heating in winter.     

Methods for the preparation of a biodesulfurization biocatalyst using Rhodococcus sp

Several methods to prepare a biodesulfurization (BDS) biocatalyst were investigated in this study using a strain of Rhodococcus sp. 1awq. This bacterium could selectively remove sulfur from dibenzothiophene (DBT) via the "4S" pathway. DBT, dimethylsulfoxide (DMSO), sodium sulphate and mixed sulfur sources were used to study their influence on cell density, desulfurization activity, desulfurization ability, and the cost of biocatalyst production. In contrast to that observed from bacteria cultured in DBT, only partial desulfurization activity of strain 1awq was induced by DBT after cultivation in a medium containing inorganic sulfur as the sole sulfur source. The biocatalyst, prepared from culture with mixed sulfur sources, was found to possess desulfurization activity. With DMSO as the sole sulfur source, the desulfurization activity was shown to be similar to that of bacteria incubated in medium with DBT as the sole sulfur source. The biocatalyst prepared by this method with the least cost could remove sulfur from hydrodesulfurization (HDS)-treated diesel oil efficiently, providing a total desulfurization percent of 78% and suggesting its cost-effective advantage.     

Avoidance bio-assays may help to test the ecological significance of soil pollution

We measured the short-term (100 min) avoidance of a soil heavily polluted by hydrocarbons by the soil springtail Folsomia candida, at six rates of dilution in a control, unpolluted soil. We compared the results with those of long-term (40-day) population tests. Five strains were compared, of varying geographical and ecological origin. When pure, the polluted soil was lethal in the long-term and avoided in the short-term by all strains. Avoidance tests, but not population tests, were able to discriminate between strains. Avoidance thresholds differed among strains. Two ecological consequences of the results were discussed: (i) toxic compounds may kill soil animals or deprive them from food, resulting in death of populations, (ii) pollution spots can be locally deprived of fauna because of escape movements of soil animals. Advantages and limitations of the method have been listed, together with proposals for their wider use in soil ecology and ecotoxicology.     

Genetic toxicity in surface water from Guaíba Hydrographic Region under the influence of industrial, urban and agricultural sewage in the Drosophila wing-spot test

Mutagenic and recombinagenic activity of surface waters in the Guaíba Hydrographic Region (RS, Brazil) was investigated using the SMART in Drosophila melanogaster. Two positive results in Caí River (September 2000 and August 2001) and in Taquari River (August 2001 and February 2002)--linked to direct recombinagenic toxicants were observed. In Jacuí samples, an indirect mutagenic and recombinagenic action was detected in a September 2000 collection and a direct recombinational activity was observed in February 2002. Also in February 2002--samples from Dilúvio Brook and Guaíba Lake (GPC) were able to induce wing spots by mitotic recombinagenesis. The former sampling site showed toxicants to have a direct action, and the latter an increment in mitotic recombination that depended on metabolic action. The SMART wing test shows that all positive responses were mainly related to homologous mitotic recombination.     

Soil amendments reduce trace element solubility in a contaminated soil and allow regrowth of natural vegetation

We tested the effects of three amendments (a biosolid compost, a sugar beet lime, and a combination of leonardite plus sugar beet lime) on trace element stabilisation and spontaneous revegetation of a trace element contaminated soil. Soil properties were analysed before and after amendment application. Spontaneous vegetation growing on the experimental plot was studied by three surveys in terms of number of taxa colonising, percentage vegetation cover and plant biomass. Macronutrients and trace element concentrations of the five most frequent species were analysed. The results showed a positive effect of the amendments both on soil chemical properties and vegetation. All amendments increased soil pH and TOC content and reduced CaCl(2)-soluble-trace element concentrations. Colonisation by wild plants was enhanced in all amended treatments. The nutritional status of the five species studied was improved in some cases, while a general reduction in trace element concentrations of the aboveground parts was observed in all treated plots. The results obtained show that natural assisted remediation has potential for success on a field scale reducing trace element entry in the food chain.     

Effect of chromium on the fatty acid composition of two strains of Euglena gracilis

The effect of hexavalent chromium on fatty acid composition was studied in two strains of Euglena gracilis; UTEX 753 (from the Culture Collection of Algae of Texas University, USA) and MAT (isolated from a highly polluted River). Both were grown in photoauxotrophic and photoheterotrophic conditions and exposed to two metal concentrations, one below and one above IC50. The high malondialdehyde (MDA) levels (3 to 7-fold) obtained with chromium concentration above IC50, suggested the existence of metal-induced lipid peroxidation. Total lipid content increased only with concentration below IC50, whereas it was inhibited by higher metal concentration. Photoheterotrophic control strains exhibited a significantly higher proportion of saturated and polyunsaturated fatty acids. Polyunsaturated acids were most affected by chromium, especially those related to chloroplast structures. Ultra-structure studies showed clear thylakoid disorganization in all treated cells. The results indicate that hexavalent chromium affects levels of fatty acids, especially those related to photosynthetic activity.