Bioremediation of soil contaminated with pentachlorophenol (PCP) using humic acids bound on zeolite

We determined the toxicity of various chlorophenols, especially pentachlorophenol (PCP), on five bacterial strains and studied PCP biodegradation in soils amended with an organomineral complex (OMC) prepared from humic acids (organic part) bound on zeolite (inorganic part). Both components of OMC have excellent sorption properties and are of natural origin and therefore suitable to be used in the environment. Toxicity of chlorophenols depends not only on the number of chlorine atoms but also on their position on aromatic ring, and is thus regiospecific. Biodegradation of PCP was studied in three real completely characterized soil samples, Chernozem, Fluvisol, and Regosol, with and without the addition of OMC. The soils were sterilized and bioaugmented with the bacterial isolate Comamonas testosteroni CCM 7530. The immobilization effect of OMC in relation to PCP depends on the concentration of humic acids (HAs), the PCP concentration, and the content of organic carbon in soil. The microbial activity and the simulated action of acid rains led to the gradual release and biodegradation of the reversibly bound PCP without no initial toxic effect on indigenous or bioaugmented microorganisms. OMC appeared to be a good trap for PCP with potential applications in remediation technology because it reduces the potential toxicity of PCP to microbial community by lowering its bioavailability and thus facilitates its biodegradation.     

Using Four Capitals to Assess Watershed Sustainability

The La Antigua watershed drains into the Gulf of Mexico and can be considered as one of the most important areas in Mexico because of its high productivity, history, and biodiversity, although poverty remains high in the area in spite of these positive attributes. In this study, we performed an integrated assessment of the watershed to recommend a better direction toward a sustainable management in which the four capitals (natural, human, social, and built) are balanced. We contrasted these four capitals in the municipalities of the upper, middle and lower watershed and found that natural capital (natural ecosystems and ecosystem services) was higher in the upper and middle watershed, while human and social capitals (literacy, health, education and income) were generally higher downstream. Overall, Human Development Index was negatively correlated with the percentage of natural ecosystems in the watershed, especially in the upper and lower watershed regions. Our results indicate that natural capital must be fully considered in projections for increasing human development, so that natural resources can be preserved and managed adequately while sustaining intergenerational well-being.     

A method for measuring the anoxic biodegradability under denitrifying conditions

A test for assessing the anoxic biodegradability of organic compounds under denitrifying conditions is proposed. The method is based on the recovery and quantification of the CO2 produced, which is evidence of complete biodegradation of the test compound (added as the sole carbon source). The tests were carried out in a mineral medium, with nitrate as electron acceptor. Whole lake sediments, sediment extracts and a commercial inoculum were assayed as a possible inoculum source by means of glucose biodegradability tests. It was found that the sediment extracts constitute a suitable and environmentally-relevant inoculum source, since they add non-significant amounts of carbon to the tests. Two xenobiotic compounds, namely, aniline and phenol, were tested in the aforementioned conditions as well as in a standard aerobic biodegradability test. Both aniline and phenol attained a biodegradation level higher than 60% in a short time period (<28 days) and thus can be considered as readily biodegradable in denitrifying environments. Nevertheless, the kinetics obtained in the anoxic test were slower than in aerobic conditions, and even suggested the accumulation of intermediate metabolites in the case of phenol. The results of this study indicate that the fate of xenobiotic compounds under anoxic conditions differs from that observed in an oxic environment, and therefore it should be considered by standard biodegradability testing procedures.     

Survey of organochlorine pesticides in horticultural soils and there grown Cucurbitaceae

Organochlorine pesticides (OCP) are still found in food and feed crops although they were applied about 40 years ago. There is a considerable knowledge gap concerning the extent of soil and crop contamination by OCP. We performed two surveys in 2002 and 2005 to assess the loads of OCP in 41 Swiss horticultural fields under organic and conventional production and corresponding Cucurbitaceae fruits (cucumbers, zucchini, and pumpkin), whereas these fields stay for intensive agricultural production in Europe. In addition, soil organic carbon, texture, and pH were measured also. OCP were detected in 27 out of 41 fields (65.9%). The farming practice had no influence on the contamination or level of OCP in soil. The sum of OCP-loads per field ranged from <0.01 to 1.3mgkg(-1) dry soil and pentachloroaniline (PCA, 2.1mgkg(-1)), p,p'-DDT (0.5mgkg(-1)), and p,p'-DDE and dieldrin (0.4mgkg(-1)) were the most detected pesticides over all investigated soils. PCA (up to 0.02mgkg(-1)), dieldrin (up to 0.04mgkg(-1)), alpha-chlordane and cis-heptachloroepoxide (<0.01mgkg(-1)) were detected in five cucumber samples out of 41 Cucurbitaceae samples. Statistical analysis revealed no significant influence of the measured soil properties on the OCP-load of soils and cucumbers, although there is evidence that the bioavailability of OCP in soils to Cucurbitaceae plants was influenced by the sorption of the compounds to soil organic matter and by the polarity of the pesticide molecules. It is suggested, that OCP contamination is widespread in all European regions with intensive plant production and associated pesticide use, and deserves more attention with respect to save food production.     

Organophosphate pesticide environmental exposure: analysis of salivary cholinesterase and carboxilesterase activities in preschool children and their mothers

A pilot study was conducted to evaluate the usefulness of salivary cholinesterase and carboxylesterase as biomarkers of exposure to environmental organophosphate pesticides. Ninety samples were obtained from women and 62 samples from their preschool-aged children who live near an agricultural area of the Upper Valley of the Negro River (Patagonia, Argentina) where pesticides are applied 6 months a year. Each participant donated two samples under similar conditions: one in the pre-exposure period and another during the pulverization period. Demographic information, potential confounders, and risk behaviors were registered. Active or passive smoking had no effect on these enzyme activities in either group. During the pulverization period, cholinesterase activity was not detectable in 76% of the children's samples and 23% of the mothers' samples. Comparing samples collected during the pulverization period with respect to the pre-pulverization period, the average mother and child cholinesterase activity decreased by 65.7% (p < 0.001) and 85.8% (p < 0.001), respectively. Also, mother and child carboxylesterase activity decreased by 27.5% (p < 0.001) and 41.9% (p < 0.01), respectively. Child carboxylesterase activity in the pulverization period was associated to the habit of eating dust outdoors (p < 0.01). The most frequent inhibition levels observed for cholinesterase and carboxylesterase activity were between 70–100% and 0–29%, respectively, in both groups studied. This shows that at the same level of exposure, cholinesterase was more sensitive to inhibition than carboxylesterase. Therefore, carboxylesterase might more properly reflect the degree of environmental organophosphate exposure and may have potential as a novel tool for biomonitoring.     

Using historical ecology to reassess the conservation status of coniferous forests in Central Europe

Forests cover approximately one‐third of Central Europe. Oak (Quercus) and European beech (Fagus sylvatica) are considered the natural dominants at low and middle elevations, respectively. Many coniferous forests (especially of Picea abies) occur primarily at midelevations, but these are thought to have resulted from forestry plantations planted over the past 200 years. Nature conservation and forestry policy seek to promote broadleaved trees over conifers. However, there are discrepancies between conservation guidelines (included in Natura 2000) and historical and palaeoecological data with regard to the distribution of conifers. Our aim was to bring new evidence to the debate on the conservation of conifers versus broadleaved trees at midelevations in Central Europe. We created a vegetation and land‐cover model based on pollen data for a highland area of 11,300 km² in the Czech Republic and assessed tree species composition in the forests before the onset of modern forestry based on 18th‐century archival sources. Conifers dominated the study region throughout the entire Holocene (approximately 40–60% of the area). Broadleaved trees were present in a much smaller area than envisaged by current ideas of natural vegetation. Rather than casting doubt on the principles of Central European nature conservation in general, our results highlight the necessity of detailed regional investigations and the importance of historical data in challenging established notions on the natural distribution of tree species.     

Improving bioavailability of phosphorous from cattle dung by using phosphatase immobilized on natural clay and nanoclay

The high P retention of acidic Andisols makes necessary to increase our technological approaches in pasture management in the animal system production. Here, we evaluated the clay- or nanoclay-acid phosphatase complexes for improving phosphorus mineralization from degraded cattle dung. We implemented an immobilization mechanism of acid phosphatase (AP) using natural clays (allophanic and montmorillonite) and nanoclays as support materials. Also, we evaluated the mineralization of organic P containing in decomposed cattle dung with clay- and nanoclay-AP complexes by incubation studies. Clays and nanoclays were characterized by microscopy techniques as atomic force and confocal-laser scanning microscopy. We found that these support materials stabilized AP by encapsulation. Our results showed that immobilization on allophanic or montmorillonite materials improved both the specific activity (4-48%) and the V_max (28-38%) of AP. Moreover, the enzyme had a better performance when immobilized on clay and nanoclay from Andisol than on montmorillonite materials. Phosphorous mineralization of cattle dung was regulated by water-soluble P present in the dung and P re-adsorption on allophanic materials. However, we were able to detect a potential capacity of AP immobilized on allophanic nanoclays as the best alternative for P mineralization. Further research with initially low water-soluble P containing organic materials is required to quantify the P mineralization potential and bioavailability of P from dung.     

Analyzing Spatio-temporal Land Cover Dynamics in an Atlantic Forest Portion Using Unsupervised Change Detection Techniques

Environmental Modeling & Assessment - Over the past decades, the Southeast Atlantic Forest in Paraíba do Sul River Valley has suffered intense deforestation and human disturbances. Due to...     

Adsorption distribution impact on preferential transport within horizontal flow constructed wetland (HFCW)

Predicting preferential water flow and solute transport in soils is in the interest of scientists and engineers in the fields of agricultural soil, forest hydrology, soil physics and wastewater treatment by constructed wetland. In artificial wetlands, any preferential pathway induces an insufficient residence time of pollutants in the soil, making an incomplete and unfinished biodegradation process, a wrong evaluation of the hydraulic residence time of the system which would hinder its management in a complete system with several entities of treatment and a non-homogeneous growth of the biofilm in the solid filter mass. This paper is a contribution in tracer experiment data analysis within a horizontal flow constructed wetland built in a storm water basin. A two-dimensional numerical model was used to simulate flow and reactive solute transport. The flow model was successfully calibrated in very dry soil conditions. The adsorption profiles used in the reactive transport modeling are those of five molecules: metolachlor, atrazine, deethylatrazine (DEA), deisopropylatrazine (DIA), and hydroxyatrazine (HA). We show that the adsorption distribution is an internal factor of soil which is responsible to the “preferential” pathway transport in a homogeneous gravel texture. The mean residence time of pollutants within the filter is strongly correlated with the average value of the adsorption coefficient. Moreover, we note a lack of significant impact of the heterogeneity of the medium on the statistical moments of breakthrough curve. It appears that a uni-modal breakthrough curve is not significant to the absence of preferential flow in the medium and at least a two-dimensional display can provide sufficient evidence on the presence or absence of preferential pathways. Finally, using a PLS regression, it is possible to perfectly discriminate the number of peaks of concentration and the asymmetry of the breakthrough curve.     

Analysis of PM2.5 and PM10 in the atmosphere of Mexico City during 2000-2002

During the last 10 years, high atmospheric concentrations of airborne particles recorded in the Mexico City metropolitan area have caused concern because of their potential harmful effects on human health. Four monitoring campaigns have been carried out in the Mexico City metropolitan area during 2000-2002 at three sites: (1) Xalostoc, located in an industrial region; (2) La Merced, located in a commercial area; and (3) Pedregal, located in a residential area. Results of gravimetric and chemical analyses of 330 samples of particulate matter (PM) with an aerodynamic diameter less than 2.5 microm (PM2.5) and PM with an aerodynamic diameter less than 10 microm (PM10) indicate that (1) PM2.5/PM10 average ratios were 0.42, 0.46, and 0.52 for Xalostoc, La Merced, and Pedregal, respectively; (2) the highest PM2.5 and PM10 concentrations were found at the industrial site; (3) PM2.5 and PM10 concentrations were lower at nighttime; (4) PM2.5 and PM10 spatial averages concentrations were 35 and 76 microg/m3, respectively; and (5) when the PM2.5 standard was exceeded, nitrate, sulfate, ammonium, organic carbon, and elemental carbon concentrations were high. Twenty-four hour averaged PM2.5 concentrations in Mexico City and Sao Paulo were similar to those recorded in the 1980s in Los Angeles. PM10 concentrations were comparable in Sao Paulo and Mexico City but 3-fold lower than those found in Santiago.