The impact of pumped water from a de-watered Magnesian limestone quarry on an adjacent wetland: Thrislington, County Durham, UK

Although quarrying is often cited as a potential threat to wetland systems, there is a lack of relevant, quantitative case studies in the literature. The impact of pumped groundwater discharged from a quarry into a wetland area was assessed relative to reference conditions in an adjacent fen wetland that receives only natural runoff. Analysis of vegetation patterns at the quarry wetland site, using Detrended Correspondence Analysis and the species indicator values of Ellenberg, revealed a clear disparity between community transitions in the quarry wetland and the reference site. Limited establishment of moisture-sensitive taxa, the preferential proliferation of robust wetland species and an overall shift towards lower species diversity in the quarry wetland were explicable primarily by the physico-chemical environment created by quarry dewatering. This encompassed high pH (up to 12.8), sediment-rich effluent creating a nutrient-poor substrate with poor moisture retention in the quarry wetland, and large fluctuations in water levels.     

The effects of UVB radiation on temperate southern hemisphere forests

The temperate forests of the southern hemisphere are the most likely forests to be affected by increased levels of ultraviolet-B (UVB) radiation resulting from reduced ozone. The review describes these forests and then discusses the morphological changes, physiological effects, and protection mechanisms, particularly UV absorbing compounds that result from present day and increasing UVB radiation. Possible avenues for future research are explored.     

Distribution of selected heavy metals and rare earth elements in surficial sediments from the polish sector of the Vistula Lagoon

The concentrations of 22 trace elements plus the rare earth elements (REE) were determined in the <63 μm fraction of surficial sediments from the Polish sector of the Vistula Lagoon by ICP-MS. For the anthropogenically-enriched elements, the mean element enrichment factors (EF's) decrease in the sequence Ag (9.9) > Sb (7.5) >As (5.8) ≥ Cd (5.2) > Pb (3.7), albeit with large variability in concentration in the sediments from one station to another. These observations demonstrate that sediments from the Vistula Lagoon are locally polluted by these anthropogenically-derived elements. Plots of NASC-normalized REE data show that the REE patterns of the sediments have not been significantly modified during transport from their source with only a minor depletion of the heavy rare earth elements (HUE) compare to the light rare earth elements (LREE). The lack of any significant anomalies for Ce and Eu indicates that redox processes have not played a major role in modifying the distribution of the REE. Factor ananalysis of the compositional data shows that sediments from the Polish sector of the Vistula Lagoon can be divided into three main groups depending on the geographical location and the degree of contamination by heavy metals.     

Effect of manganese on the concentration of amino acids in different regions of the rat brain

The present study was designed to determine if chronic exposure of weanlings and adult rats to Mn produces significant alterations in amino acid concentrations in different regions of the rat brain. Weanling (30 day old) and adult (90 day old) male rats were exposed to 10 and 20 mg Mn/kg body weight per day, by gavage, for 30 days. Forty-eight hours after the last dose, animals were sacrificed by decapitation and brains were dissected into different regions to determine the concentration of amino acids by HPLC/EC. A dose dependent decrease in body weight gain was found in the adult, but not in the weanling rats. Significant increases occurred in concentrations of aspartate, glutamate, glutamine, taurine and gamma-aminobutyric acid (GABA) in the cerebellum of the adult rats dosed with 20 mg/kg per day, Mn. A significant decrease in the concentration of glutamine was observed in caudate nucleus and hippocampus of weanling rats dosed with 10 mg/kg, Mn. These data suggest that chronic Mn exposure can produce a decrease in body weight gain in adult rats and alterations in amino acids in different regions of weanling and adult rat brains.     

Methane emission from lakes

A physico-chemical model to describe methane and carbon dioxide emission from lakes was developed. The model describes the emission by diffusion, bubbles and plants. The intensity of the fluxes can be calculated either for total or particular emission in dependence on gas bubbles composition. It was found, that diffusional (Q) and bubble (J) fluxes depend on the methane molar ratio (X) in bubbles as follows: [formula: see text]. The model allows to estimate the role of the methane oxidation by atmospheric oxygen in the total methane flux. It was shown, that the methane oxidation does not influence much methane fluxes to the atmosphere for most of the experimentally observed situations.     

Clearance of PCDD/Fs via the gastrointestinal tract in occupationally exposed persons.

A digestive tract mass balance was performed on six men with high body burdens of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Intake via food was measured by analyzing duplicate portions of the food consumed by the volunteers and excretion via feces was determined by quantitative collection and analysis of the feces. Blood samples were taken to determine the current body burden. The results showed that the quantity of non-metabolized chemical excreted in the feces clearly exceeded the uptake via food for all of the 2,3,7,8-substituted PCDDs and some of the PCDFs, indicating a significant clearance across the gastrointestinal tract. The concentrations of these PCDD/F congeners in blood and feces were highly correlated (r > 0.8), demonstrating that the fecal PCDD/F content was determined by the body burden. The half lives in the test persons due to fecal clearance of non-metabolized chemical were estimated from the excretion rate and the current body burden and ranged between 10 years (Cl8DD) and 33 years (2,3,4,7,8-Cl5DF). These were compared with the overall contaminant half-lives due to all clearance processes which were calculated from the body burden and the decrease in blood concentrations measured over several years. The fecal clearance of non-metabolized PCDD/F contributed on average between 37% (2,3,7,8-Cl4DD) and 90% (Cl8DD) to the total elimination. This indicates that the gastrointestinal pathway plays a decisive role in the clearance of most 2,3,7,8-subsituted PCDD/F congeners.     

Chlorinated hydrocarbon contaminants in Hong Kong surficial sediments.

Twenty surficial sediments were sampled from nearshore Hong Kong waters during 1997-1998, and analyzed for a range of chlorinated pesticides and polychlorinated biphenyls (PCBs). Results showed that concentrations (on a dry weight basis) of total HCHs were in the range 0.1-16.7 ng g-1, and total DDTs 0.3-14.8 ng g-1. PCBs, measured as an Aroclor 1242, 1248, 1254, 1260 (1:1:1:1) mixture, were found to be in a range of 0.5-97.9 ng g-1, and were at highest concentrations in Victoria Harbour. Results indicated that chlorinated pesticides and PCBs in Hong Kong nearshore sediments were most likely derived from waste discharge from a variety of sources, including agricultural, sewage, industrial waste disposal and shipping-related activities. In addition, as the north and west sides of Hong Kong are subject to influence from the Pearl River (due mainly to agricultural activities in the Pearl River Delta, and to a lesser extent developments around the Shenzhen Special Economic Zone), these inputs are also thought to be likely sources of contamination.     

Toxicological characterization of sediments from Baie des Anglais on the St. Lawrence Estuary.

The sediments of Baie des Anglais on the St. Lawrence Estuary have a history of environmental contamination, but no information exists relating to their toxicity. The purpose of the present study was to characterize three sites in and near Baie des Anglais, in terms of sediment toxicity and contaminants. Sites 1 and 2 within the Baie des Anglais are relatively close to local industry and municipal sewage discharge points, while Site 3 is outside the bay. Three microscale bioassays, Microtox, echinoderm fertilization and Toxi-ChromoPad, showed that sediments from Site 1 were the most toxic, followed by Site 2. Site 3 was non-toxic. While the solid phase Microtox test did indicate that Site 1 was most toxic, the absolute response was weak. Liver cytochrome P450 1A1 mRNA in American plaice (Hippoglossoides platessoides), captured at Site 1 in the bay was significantly induced compared to the P450 system of plaice captured at Sites 2 and 3. Hepatic metallothionein mRNA levels were not significantly different between plaice captured at all three sites. Sediment chemical analyses revealed a gradient in polycyclic aromatic hydrocarbons, polychlorinated biphenyls and dibenzofurans (PCDF) with the highest levels recorded at Site 1, about 10-fold less at Site 2 and 100-fold less at Site 3. Amongst the organochlorines the PCDF group were deemed the most important due to their prevalence and known toxicity. Heavy metal concentrations were low and representative of background levels for the St. Lawrence Estuary.     

Determination of organochlorine and organophosphate pesticide residues in fruits, vegetables and sediments.

A method is described for the determination of organochlorine and organophosphate pesticide residues in fruits, vegetables and sediments. The concentrated solvent extract was sealed in a polymeric membrane tube, dialysed in cyclohexane and the solvent replaced with hexane. The organophosphates were analysed on a specific thermionic detector without further clean-up. For the organochlorine pesticides the extract was eluted through 3 g of alumina and analysed on GC/ECD. The clean-up for sediment extract was carried out on a 10 g alumina column with 100 mL hexane containing 5% acetone and the eluate was concentrated to 5 mL. The detection limit for organophosphates on a 40 g sample and a final volume of 10 mL was on the average 0.01 mg/kg. The detection limit for organochlorine pesticides, with the final volume of 25 mL, was 0.005 mg/kg for all pesticides except for p,p'-DDT and endosulfan sulphate, which was 0.01 mg/kg. The detection limit for organochlorine pesticides in sediment, with the final volume of 2 mL, was less than 1 microgram/kg and for organophosphate pesticides less than 10 micrograms/kg when the final volume was made to 0.5 mL. At the detection limits the method produced a very high coefficient of variation for both organochlorine and organophosphate pesticides.     

Methods for the analysis of PCBs in human food, faeces and serum.

A method was developed to determine trace concentrations of a range of individual PCB congeners in biological samples (serum, food and faeces) using GC-MS, to prepare a mass balance of PCBs in humans. A simple method for the analysis of PCBs in human serum, which excluded an extraction step, was first employed. Results indicated that the recoveries of 13C12 PCB spikes were variable. A soxhlet extraction step was added and was found to be efficient and reproducible. A quality control routine and method validation results are presented. In batch tests of the methods presented it was found that the serum analysis method gave within batch mean 13C12 spike recoveries of 98-120% and standard deviations between 6 and 20%. The food/faeces analysis method gave within-batch mean 13C12 spike recoveries of 88-100%, and within batch standard deviations between 4 and 12%. The batch to batch mean recovery for serum analysis was 100%, with an RSD of 9% for high spikes and 10% for low spikes. For food/faeces analysis the batch to batch average recovery was 110%, with an RSD of 5% for high spikes and 9% for low spikes.