This work aimed to report present levels (2007–2008 sampling) of tri- (TBT), di- (DBT), and monobutyltin (MBT) in surface sediments from 11 Portuguese coastal sites and discuss the evolution of BTs contamination in the last two decades. All the samples revealed quantifiable values of TBT, DBT, and MBT with total butyltin concentrations between 1 and 565 ng/g (of Sn in dry sediment). Maximum level of TBT, 66 ng/g, was observed in Sado estuary, at Lisnave site, in the proximity of a big shipyard. MBT decreased site by site by the same order as DBT and TBT did, but its concentrations were much higher in many cases, denoting that TBT contamination was much higher in the past. A comparison with the available previous data confirmed a marked decrease of TBT contamination all over the last years, indicating that the main sources of TBT in Portuguese coastwise stopped effectively. 相似文献
The objective of this study was to investigate both acute and chronic effects of clofibrate and clofibric acid on the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH) and catalase (CAT) of the mosquitofish (Gambusia holbrooki). AChE, commonly used as a biomarker of neurotoxicity, was determined in the total head. LDH, an important enzyme of anaerobic metabolism, was quantified in dorsal muscle, and CAT, enzyme which has been used as indicative parameter of peroxisome proliferation, was determined in the liver. Furthermore, alterations of body and liver weight were also determined, through the calculation of the ratios final body weight/initial body weight, liver weight/final body weight, liver weight/gills weight and liver weight/head weight. Acute exposure of G. holbrooki to both clofibrate and clofibric acid induced a decrease in liver CAT activity, an increase in muscle LDH activity, while no effects were observed on AChE activity. However, chronic exposure did not alter significantly the enzymatic activities, suggesting reduced or null effects over these pathways, relative to effects reported in other species. No effects were observed for the calculated ratios, except a significant weight reduction for males chronically exposed to clofibrate. 相似文献
Although arable landscapes have a long history, environmental problems have accelerated in recent decades. The effects of these changes are usually externalized, being greater for society as a whole than for the farms on which they operate, and incentives to correct them are therefore largely lacking. Arable landscapes are valued by society beyond the farming community, but increased mechanization and farm size, simplification of crop rotations, and loss of non-crop features, have led to a reduction in landscape diversity. Low intensity arable systems have evolved a characteristic and diverse fauna and flora, but development of high input, simplified arable systems has been associated with a decline in biodiversity. Arable intensification has resulted in loss of non-crop habitats and simplification of plant and animal communities within crops, with consequent disruption to food chains and declines in many farmland species. Abandonment of arable management has also led to the replacement of such wildlife with more common and widespread species. Soils have deteriorated as a result of erosion, compaction, loss of organic matter and contamination with pesticides, and in some areas, heavy metals. Impacts on water are closely related to those on soils as nutrient and pesticide pollution of water results from surface runoff and subsurface flow, often associated with soil particles, which themselves have economic and ecological impacts. Nitrates and some pesticides also enter groundwater following leaching from arable land. Greatest impacts are associated with simplified, high input arable systems. Intensification of arable farming has been associated with pollution of air by pesticides, NO2 and CO2, while the loss of soil organic matter has reduced the system's capacity for carbon sequestration. International trade contributes to global climate change through long distance transport of arable inputs and products. The EU Rural Development Regulation (1257/99) provides an opportunity to implement measures for alleviating ecological impacts of arable management through a combination of cross-compliance and agri-environment schemes. To alleviate the problems described in this paper, such measures should take account of opportunities for public/private partnerships and should integrate social, cultural, economic and ecological objectives for multifunctional land use. 相似文献
Macroinvertebrate benthic communities are one of the key biological components considered for the assessment of benthic integrity in the context of the Water Framework Directive (WFD). However, under moderate contamination scenarios, the assessment of macrobenthic alterations at community level alone could be insufficient to discriminate the environmental quality of coastal and transitional waters. Keeping this in view, sediment quality of moderately contaminated sites in a coastal lagoon (óbidos lagoon, Portugal) was assessed by the combination of sediment metal levels, Carcinus maenas biomarkers (accumulated metals and oxidative stress responses) and macrobenthic communities. Two sites were selected in confined inner branches (BS and BB) and a third one in the middle lagoon (ML). The site BB presented slightly higher levels of metals in sediment but biological variables calculated for macrobenthic data were not significantly different between sites. The biotic index M-AMBI that is being applied to assess environmental quality of transitional waters in the scope of the WFD pointed either to high (site ML) or good quality status (BS and BB) in the selected sites. However, crabs from BB site presented significantly higher levels of Ni in hepatopancreas than those from ML and macrobenthic community structure was significantly different between BB and ML. Additionally, spatial differences were obtained for oxidative stress parameters suggesting that BB site presented stressors for crabs (higher GST and lower GSHt at BB site). Factor analysis (PCA) integrating sediment contamination, biomarkers in crabs and macrobenthic data also distinguished BB site as the most environmentally disturbed. On the other hand, at ML site, some macrobenthic variables (equitability and polychaetes’ diversity) were found to be enhanced by current environmental conditions, suggesting the existence of a better sediment quality. Current results pointed to the usefulness of integrating macrobenthic community alterations with responses at organism level (bioaccumulation and biochemical endpoints) in order to increase the accuracy of environmental quality assessment in lagoon systems. Moreover, the application of different statistical methods was also found to be recommendable. 相似文献
Selenium (Se) is an essential metalloid element for mammals. Nonetheless, both deficiency and excess of Se in the environment are associated with several diseases in animals and humans. Here, we investigated the interaction of Se, supplied as selenate (Se+6) and selenite (Se+4), with phosphorus (P) and sulfur (S) in a weathered tropical soil and their effects on growth and Se accumulation in Leucaena leucocephala (Lam.) de Wit. The P-Se interaction effects on L. leucocephala growth differed between the Se forms (selenate and selenite) supplied in the soil. Selenate was prejudicial to plants grown in the soil with low P dose, while selenite was harmful to plants grown in soil with high P dose. The decreasing soil S dose increased the toxic effect of Se in L. leucocephala plants. Se tissue concentration and total Se accumulation in L. leucocephala shoot were higher with selenate supply in the soil when compared with selenite. Therefore, selenite proved to be less phytoavailable in the weathered tropical soil and, at the same time, more toxic to L. leucocephala plants than selenate. Thus, it is expected that L. leucocephala plants are more efficient to phytoextract and accumulate Se as selenate than Se as selenite from weathered tropical soils, for either strategy of phytoremediation (decontamination of Se-polluted soils) or purposes of biofortification for animal feed (fertilization of Se-poor soils).
Radiotracer experiments were performed (February–April, 1982) to study the assimilation and metabolism of the transuranium nuclide americium-241 in the marine teleosts Serranus scriba (Linnaeus, 1758) and Scorpaena notata Rafinesque, 1810, caught off the Monaco coast. Fish fed with 241Am-labelled food showed that assimilation of this radionuclide takes place through the gastrointestinal walls and that the small fraction accumulated is incorporated mainly in the skin, muscle and skeleton. Gut-transfer coefficients were similar in both species and averaged 0.7% (range 0.1 to 1.7%) of the ingested activity. The calculated biological half-lives for loss of the absorbed fraction ranged between 49 and 61 d for Serranus scriba and 12 and 117 d for Scorpaena notata. Results from an intramuscular injection experiment indicated that 241Am was retained mainly in the liver, skin and skeleton; the fraction accumulated by muscle was very low. Liver displayed a relatively short biological half-time for 241Am loss of roughly 24 d. Routes of 241Am excretion from the teleosts appear to be through the kidneys, gills and feces with bile serving as a possible excretion route from the liver. From the limited amount of published information available for comparison, experimental evidence is presented which suggests that 241Am taken up via the food chain is more biologically available to marine fish than is plutonium. 相似文献