Role of iron chemistry in controlling the release of pollutants from resuspended sediments

Aquatic sediments often contain a large number of chemical contaminants that are potential pollutants. It is often presumed that such contaminants are released to the water column during sediment resuspension and, in there, adversely impact aquatic life and other beneficial uses of the water. However, extensive laboratory and field studies of about 100 contaminated sediments from across the United States that specifically addressed this type of release showed that of about 30 common heavy metals, organic compounds, and other potential pollutants, only manganese II and ammonia were released to then remain in the water column after sediment resuspension. These results indicated that the chemistry of aqueous iron controls the availability of many contaminants in resuspended sediment. The formation of ferric hydroxide during sediment suspension into the water column, as a result of the reaction between ferrous iron in the sediments and dissolved oxygen in the water column, leads to rapid scavenging of many contaminants in the Fe(OH)₃ precipitate. The scavenged contaminants are redeposited in the sediments. This article reviews the role of the aqueous chemistry of iron as it relates to controlling the release of potential pollutants from resuspended sediments. © 2005 Wiley Periodicals, Inc.     

Ecophilosophy and science

Summary This paper aims to do two main things: first, to provide an introduction to ecophilosophy by presenting a spectrum of positions that have been developed to characterise the relationship between humans and their environment; second, to examine the variety of ways in which scientific work impacts upon human thought in regard to each of these positions. The import of this discussion should be twofold: first, it should help to acquaint readers with, and hopefully, interest them in, the kinds of developments that have been occurring in the area of ecophilosophy; second, it should help to acquaint environmentally concerned people with, and, hopefully, interest them in, the relevance of science to their arguments. Although many environmentally concerned people are scientifically informed, this second aim is worth stating because a number of environmentally concerned people unfortunately remain suspicious of the role of science in general.Dr Warwick Fox is a Research Fellow at the Centre for Environmental Studies at the University of Tasmania. His first degree, in experimental psychology from the University of Western Australia, was followed by PhD in environmental philosophy. Currently his research interests are concerned with the development of a comprehensive and coherent oriented world view, from epistemology and cosmology to psychology, ethnics and politics.     

Evaluating the practices of climate-smart agriculture sustainability in Ethiopia using geocybernetic assessment matrix

Environment, Development and Sustainability - The geocybernetic assessment matrix (GAM) evaluation of climate-smart agriculture (CSA) practices in Ethiopia is carried out in this paper. With regard...     

A question of justice: are holiday clubs serving the most deprived communities in England?

In response to the problem of holiday hunger, hundreds of local “holiday clubs” have recently been established across the UK. This research examines the spatial relationship between income, childhood deprivation, ethnicity and holiday clubs across 32,844 Lower Super Output Areas (LSOAs) in England to determine if these clubs are currently operating in an inclusive fashion. Data on the location of holiday clubs comes from a national survey. Binary logistic regression results suggest that holiday clubs are likely to operate in economically disadvantaged areas. At the same time, clubs are not distributed equally by ethnicity. That is, holiday clubs operated by voluntary organisations are more likely to be situated in LSOAs that are disproportionately white and English\British and less likely to be situated in LSOAs that are disproportionately ethnic minority. This finding has important implications for the pursuit of holiday clubs as a policy mechanism for addressing access to food in light of the state’s failure to adequately feed all of the country’s children.     

Levels of PCDD/Fs and trace elements in superficial soils of Pavia Province (Italy)

Trace elements and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed in soils from rural and light-industrialized sites (n=168) of Province of Pavia (Northern Italy). Most of the trace element values fit in typical ranges of concentrations in soils and are similar to the ones reported for rural sites in Italy or sites with no direct anthropogenic impact. Total concentrations of 2,3,7,8 chlorine substituted PCDD/Fs in superficial soils ranged between 24.4 and 1287 pg g(-1) dw (0.5-28.9 pg WHO(98)-TEQ g(-1) dw). The North Eastern part of the Province presented significantly higher levels (p<0.001) than the rest of the Province for As, Cd, Hg, Pb, Zn and PCDD/Fs. While the existence of a defined heavy metal polluting source for this specific site has been suggested, in the case of PCDD/Fs, profiles were not linked to any specific emission source fingerprint. In the whole extension of Pavia Province, OCDD/F dominated the 2,3,7,8 chlorine substituted congener soil pattern, followed by the 1,2,3,4,6,7,8 hepta-CDD/F congener. Principal Component Analysis (PCA) showed that this profile could not be associated to any described PCDD/F emission source fingerprint and was relatively similar to the baseline deposition of sites with no direct impact of PCDD/F emission sources independently of land use.     

Substrate-dependent bacterivory by intertidal benthic copepods

The trophic importance of bacteria to harpacticoid copepods in intertidal areas remains poorly understood, and so do the mechanisms of bacterial feeding. It is, for instance, unclear whether harpacticoids directly target bacterial cells or merely co-ingest them with substrates to which bacterial cells may be attached. Here, we investigate bacterial uptake and substrate requirement for four mud intertidal species (Microarthridion littorale, Platychelipus littoralis, Delavalia palustris and Nannopus palustris) by means of ¹³C-labeled bacteria and biomarker fatty acids (FA). Bacterial uptake strongly depended on grazing on a primary food source but bacterial ingestion rates were low, and no clear indication of copepods directly targeting bacteria was found. Delavalia was the only species that accumulated bacteria-derived FA and gained in polyunsaturated FA (PUFA) probably through bioconversion of bacteria-derived FA. In general, however, our results suggest that bacteria represent a relatively minor and low-quality food for intertidal harpacticoid copepods.