Utilising the Synergy between Plants and Rhizosphere Microorganisms to Enhance Breakdown of Organic Pollutants in the Environment (15 pp)

Background Phytoremediation is a promising technology for the cleanup of polluted environments. The technology has so far been used mainly to remove toxic heavy metals from contaminated soil, but there is a growing interest in broadening its applications to remove/degrade organic pollutants in the environment. Both plants and soil microorganisms have certain limitations with respect to their individual abilities to remove/breakdown organic compounds. A synergistic action by both rhizosphere microorganisms that leads to increased availability of hydrophobic compounds, and plants that leads to their removal and/or degradation, may overcome many of the limitations, and thus provide a useful basis for enhancing remediation of contaminated environments.Main Features The review of literature presented in this article provides an insight to the nature of plant-microbial interactions in the rhizosphere, with a focus on those processes that are relevant to the breakdown and/or removal of organic pollutants. Due consideration has been given to identify opportunities for utilising the plant-microbial synergy in the rhizosphere to enhance remediation of contaminated environments.Results and Discussion The literature review has highlighted the existence of a synergistic interaction between plants and microbial communities in the rhizosphere. This interaction benefits both microorganisms through provision of nutrients by root exudates, and plants through enhanced nutrient uptake and reduced toxicity of soil contaminants. The ability of the plant-microbial interaction to tackle some of the most recalcitrant organic chemicals is of particular interest with regard to enhancing and extending the scope of remediation technologies.Conclusions Plant-microbial interactions in the rhizosphere offer very useful means for remediating environments contaminated with recalcitrant organic compounds.Outlook A better knowledge of plant-microbial interactions will provide a basis for improving the efficacy of biological remediations. Further research is, however, needed to investigate different feedback mechanisms that select and regulate microbial activity in the rhizosphere.     

Survey of dioxin sources in the Baltic Region (extended summary)

The present paper summarises the results of the project: 'Survey of Anthropogenic Sources of Dioxins and Furans in the Baltic Region'. As a part of the project, inventories have been carried out in Estonia, Latvia, Lithuania and Poland by applying the toolkit for quantification of dioxin and furan releases developed by UNEP Chemicals. The main route of direct releases to the environment is emission to air. Total emission to air from Poland was estimated at 490 (88-1,300) g I-TEQ/year, whereas the emissions from Estonia, Latvia and Lithuania were estimated as being 14 (2.4-54), 23 (2.6-63) and 17 (2.6-38) g I-TEQ, respectively. In general, the uncertainty on the estimates is very high, and recommendations regarding further development of the inventories have been made, and measures for reducing the releases have been provided.     

Influence of chlorination pH and chlorine dose on the formation of mutagenic activity and the strong bacterial mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-5(2H)-furanone (MX) in water

Samples from two Dutch raw water sources were chlorinated in the laboratory at different pH:s and chlorine doses, and were analysed for mutagenic activity and the mutagenic compound 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX). Chlorination produced mutagenic activity as well as MX in both waters. The formation of MX was favoured by acidic reaction conditions and high chlorine doses, but in waters treated with excess chlorine at pH 9, no MX was detected. The mutagenicity was approximately on the same level after chlorination of both water types but the MX concentration was significantly higher in the water containing mainly humic material.

MX was found to be quantitatively extracted from acidified waters by the XAD resin adsorption technique.     

Road safety effects of roundabouts in Flanders

INTRODUCTION: This paper analyzes the effect on road safety of 95 roundabouts that were built in Flanders between 1994 and 1999. RESULTS: The study shows that the effect on the number and severity of road accidents adjusted for the trend and regression to the mean is significant, but varies considerably in accordance with the speed limit regime on the intersection. Roundabouts are most effective on intersections of a main road with a high speed limit (90 km/h) and an adjacent road with a lower speed limit (50 or 70 km/h). The empirical analysis reveals a reduction of 34% (varying between 15% and 59%) for the total number of injury accidents, 30% (7%-45%) for light injury accidents, and 38% (27%-72%) for serious injury accidents. This study also takes a closer look at the impact of different post-implementation periods using accident data of 1-, 3-, or 6-years after the construction of a roundabout on the calculated effectiveness results and warns for a severe underestimation when a one-year period is used. IMPACT ON INDUSTRY: An effective traffic safety policy based on scientific results thus requires some patience from the policy-makers.     

Restricted host use by the herbivorous amphipod <Emphasis Type="Italic">Peramphithoe tea</Emphasis> is motivated by food quality and abiotic refuge

There is a growing list of marine invertebrate herbivores known to restrict their host choices to a subset of available species, yet the relative importance of the evolutionary forces that select for specialized feeding habits remain unclear. One such specialist is the gammaridean amphipod Peramphithoe tea (F. Ampithoidae) that restricts its distribution to the brown laminarian seaweed Egregia menziesii in Oregon. A field survey indicated that among available seaweeds in the low intertidal zone of Boiler Bay, Oregon, Egregia housed greater than 90% of P. tea individuals. A set of laboratory-based habitat and feeding choice assays revealed that this specialized host distribution is likely the consequence of choices made by adult P. tea. The restricted host choice is apparently maintained by at least two evolutionary forces. First, a juvenile performance assay indicates that both Egregia and the co-occurring seaweed Alaria marginata, provide high food quality relative to other seaweeds available in the low-intertidal zone. Second, a field transplantation experiment revealed that Egregia protects adult amphipods from becoming dislodged with wave energy more readily than did Alaria. Thus, Egregia’s value as good quality food and refuge from abiotic stress together explain the restricted host use of P. tea. A comparison with previous studies suggests that use of Egregia is not consistent across the geographic range of P. tea, suggesting the possibility that the host preferences of local populations may respond evolutionarily to geographic shifts in seaweed communities.