Mobilization of arsenic in groundwater of Bangladesh: evidence from an incubation study

The extensive extraction of arsenic (As)-contaminated groundwaters for drinking, household and agricultural purposes represents a serious health concern in many districts of Bangladesh. This laboratory-based incubation study investigated the sources and mechanisms of As mobilization in these groundwaters. Several incubation studies were carried out using sediments collected from the Bangladesh aquifer that were supplemented, or not, with different nutrients, followed by an analysis of the sediment suspensions for pH, ORP (oxidation-reduction potential), EC (electrical conductivity) and As and Fe(ΙΙ) concentrations. In the substrate-amended sediment suspensions incubated under anaerobic environment, there was a mobilization of As (maximum: 50–67 μg/l) and Fe(ΙΙ) (maximum: 182 μg/l), while the ORP value decreased immediately and drastically (as much as −468 mV to −560 mV) within 5–6 days. In the sediment suspensions incubated under control and aerobic conditions, no significant As mobilization occurred. The simultaneous mobilization of As and Fe(ΙΙ) from sediments is a strong indication that their mobilization resulted from the reduction of Fe oxyhydroxide by the enhanced activity of indigenous bacteria present in the sediments; this phenomenon also provides insights on the mobilization mechanism of As in groundwater. The concentrations of As in the sediments used in the incubation studies were strongly linked to the gradients of redox potential development that was stimulated by the quantity of organic nutrient (glucose) used. The penetration of surface-derived organic matter into the shallow aquifer may stimulate the activity of microbial communities, thereby leading to a reduction of iron oxyhydroxide and As release.     

Means to improve the effect of in situ bioremediation of contaminated soil: an overview of novel approaches

Different aspects of bacterial degradation of organic contaminants in soil, and how to improve the efficiency and reproducibility is discussed in this review. Although bioremediation in principle includes the use of any type of organism in improving the condition of a contaminated site, most commonly bacteria are the degraders and other organisms, such as soil animals or plant roots, play a role in dissemination of bacteria and, indirectly, plasmids between bacteria, and in providing nutrients and co-substrates for the bacteria active in the degradation process. There are a number of different procedures that have been tested more-or-less successfully in attempts to improve reliability, cost efficiency and speed of bioremediation. The methods range from minimal intervention, such as mere monitoring of intrinsic bioremediation, through in situ introduction of nutrients and/or bacterial inocula or improvement of physico-chemical conditions, all the way to excavation followed by on site or ex situ composting in its different varieties. In the past the rule has been that more intervention (leading to higher costs) has been more reliable, but novel ideas are continuously tried out, both as a means to come up with new truly functional applications and also as a line of studies in basic soil microbial ecology. Both approaches generate valuable information needed when predicting outcome of remediation activities, evaluating environmental risks, deciding on cleaning-up approaches, etc. The emphasis of this review is to discuss some of the novel methods for which the value has not been clearly shown, but that in our view merit continued studies and efforts to make them work, separately or in combination.     

Methyl jasmonate increases aluminum tolerance in rice by augmenting the antioxidant defense system,maintaining ion homeostasis,and increasing nonprotein thiol compounds

Environmental Science and Pollution Research - Aluminum (Al) stress is known as a serious threat to the growth and production of crops in acidic soils. Here, the effects of different concentrations...     

The South Karelia Air Pollution Study: Relationship of Outdoor and Indoor Concentrations of Malodorous Sulfur Compounds Released by Pulp Mills

We studied the indoor penetration of ambient air malodorous sulfur compounds released by pulp mills. The indoor and outdoor concentrations were simultaneously measured with automatic SO₂ analyzers. The filtering effect of three different materials connected to a gaseous filter unit was tested during six study periods. The tested materials were Sorbixofil® based on gypsum impregnated by KMnO₄ Purafil® based on Al₂O₃, both absorbing sulfur compounds by oxidation, and carbonized tissue. The periods lasted from 14 to 88 days. The results indicated that malodorous sulfur air pollutants penetrated indoors effectively, but after some delay because the dilution was slow. In a comparison of different filter materials, Purafil® was the most effective, producing low indoor concentrations. The study concludes that people living near pulp mills are exposed to substantial amounts of malodorous air pollutants, both indoors and outdoors. This exposure can be reduced by using gaseous sulfur sensitive filter materials connected to a controlled ventilation system.