Polybrominated diphenyl ethers (PBDEs) and 2,2′,4,4′,5,5′-hexabromobiphenyl (BB-153) in landfill leachate in Cape Town, South Africa

An assessment of the concentrations of selected polybrominated diphenyl ether (PBDE) congeners as well as BB 153 in leachate samples collected from three landfill sites within the city of Cape Town was conducted. A liquid–liquid extraction technique was employed for the isolation of all the target compounds from the leachate samples. Extracts obtained were further subjected to multi-layer column chromatography employing different forms of silica gel. The prepared samples were analysed using a high capillary gas chromatograph equipped with a micro-electron capture detector (GC-μECD). The overall mean concentrations of the total PBDEs, including BDE 209 ranged between 5.65 and 2,240, 0.28–20.5 and 1.66–1,170 ng/l for Bellville, Coastal Park, and Vissershok landfill sites, respectively. The mean concentrations of BB 153, which were generally low in most of the samples analysed, were 70.4, 7.14 and 8.16 ng/l for Bellville, Coastal Park and Vissershok sites, respectively. The influence of precipitation on the characteristics and quantity of leachate produced from the landfill sites investigated was most pronounced during the August/September sampling regime. Generally, the trend observed in this study clearly indicated a wide variation in the levels of these contaminants in all the landfill sites studied from one sampling period to the other. However, the principal component analysis revealed that the release of these contaminants might be associated with two or three possible sources. This study further confirmed the relevance of landfill leachate as an important source of PBDE contamination of the environment, especially the groundwater and surface water sources.     

Tales of island tails: biogeomorphic development and management of barrier islands

The Frisian islands (Southern North Sea) have extensive island tails, i.e. the entire downdrift side of an island consisting of salt marshes, dunes, beaches and beach plains, and green beaches. Currently, large parts of these tails are ageing and losing dynamics, partly due to human influence. This may mean a loss of young stages on the long term, and current management is not enough to counteract this. To aid the development of new interventions aiming at (re)introducing natural dynamics, a conceptual model of island-tail development under natural and disturbed conditions was developed, based on existing data, field visits and literature. The development of an island tail follows the general pattern of biogeomorphic succession. The first phase consists of a bare beach plain. In the second phase, embryonic dunes form. In the third phase, green beaches, dunes and salt marshes form, including drainage by creeks and washovers. In the fourth phase, vegetation succession continues and the morphology stabilises. Human interference (such as sand dikes and embankments) reduces natural dynamics and increases succession speed, leading to a reduction in the diversity in landforms and vegetation types. Both for natural and human-influenced island tails, succession is the dominant process and large-scale rejuvenation only occurs spontaneously when large-scale processes cause erosion or sedimentation. Island tails cannot be kept permanently in a young successional stage by reintroducing natural dynamics through management interventions, as biogeomorphic succession is dominant. However, such interventions may result in local and temporal rejuvenation when tailored to the specific situation.     

Analyzing spatial count data,with an application to weed counts

Count data on a lattice may arise in observational studies of ecological phenomena. In this paper a hierarchical spatial model is used to analyze weed counts. Anisotropy is introduced, and a bivariate extension of the model is presented.     

荷兰莱茵河和墨兹河三角洲五斑按蚊麦赛变种和黑小按蚊幼体种群的分布及动态

本文研究了荷兰两南部莱茵河和默兹河三角洲地区五斑按蚊(Anopheles maculipennis)复合体蚊虫的分布及生态学.研究地区以前曾流行过疟疾,而黑小按蚊(A.atroparvus)则是唯一的传病媒介.对五斑按蚊的125处潜在的水生生境进行了采样,其中有47处(37.6%)含有这一物种复合体的幼体.     

The role of water in the development of The Netherlands— a historical perspective

In this paper an overview is presented of the landscape development of the low-lying parts of The Netherlands. It is shown that water has played an important role in this development. Since prehistoric times, but especially since about 800 AD, man has gradually occupied the low lands along the sea and the main rivers. Through these settlements a chain of actions and reactions of man and his physical environment was set into motion. This chain of events is briefly outlined. It is stated and also illustrated that not only the characteristics of the landscape of the western part of The Netherlands, but also the organization of the Dutch society has been influenced strongly by manÕs need to cope with the omnipresence of water and the threats and opportunities posed by that. It is concluded that the outlined events can only be understood properly if interdisciplinary research takes a more prominent role than it does now.     

A Novel Environmental Quality Criterion for Acidification in Swedish Lakes – An Application of Studies on the Relationship Between Biota and Water Chemistry

The recovery from acidification has led to the demand for more precise criteria for classification of acidification. The Swedish Environmental Protection Agency has revised Sweden’s Ecological Quality Criteria for acidification to improve the correlation between the chemical acidification criteria and biological effects. This paper summarises the most relevant findings from several of the studies commissioned for this revision. The studies included data on water chemistry in 74 reference lakes in southern Sweden with data on fish in 61 of the lakes, as well as data on littoral fauna in 48 lakes. We found that the acidity variable most strongly correlated to the biota was the median pH from the current year. Our results probably do not reflect the mechanisms behind the negative effects of acidity on the biota, but are fully relevant for evaluation of monitoring data. The biogeochemical models used for predicting acidification reference conditions generate a pre-industrial buffering capacity. In order to get an ecologically more relevant criteria for acidification based on pH, we transferred the estimated change in buffering capacity into a corresponding change in pH. A change of 0.4 units was defined as the threshold for acidification. With this criterion a considerably lower number of Swedish lakes were classified as acidified when compared with the present Ecological Quality Criteria.     

Inhibition of ethoxyresorufin-O-deethylase (EROD) activity in mixtures of 2,3,7,8-tetrachlorodibenzo-p-dioxin and polychlorinated biphenyls

Induction of ethoxyresorufin-O-deethylase (EROD) activity and porphyrin accumulation shows different structure-activity relationships for different polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Interactions between the two responses can strongly influence the induction and activity of EROD. The results support the conclusion that there are nonadditive interactions between nondioxin-like PCBs and dioxin-like compounds. The interaction between EROD activity and the porphyrin biosynthesis makes the prerequisite of additivity in the toxic equivalency factor concept for environmental mixtures highly spurious. Inhibition of EROD activity caused by non-dioxin like compounds could have a significant impact on the value of EROD activity as a biomarker in the present methods of risk assessment for these compounds.     

Disposition, elimination and enzyme induction of 1,2,3,7,8-PnCDD, 1,2,3,6,7,8-HxCDD and 2,3,4,7,8-PnCDF in the liver of the mouse after a single oral dose

The disposition, elimination and cytochrome P450 related enzyme induction of 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PnCDD), 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin (HxCDD) and 2,3,4,7,8-pentachlorodibenzofuran (PnCDF) were studied in the liver of the male C57BL/6 mouse. Elimination of all compounds from the liver followed first-order kinetics. Half-lives for PnCDD, HxCDD and PnCDF were 15, 52 and 65 days respectively. 7-Ethoxyresorufin-O-deethylation (EROD) activity in the livers of the treated animals showed a good correlation with the liver tissue concentrations but the slopes of these liver concentration-response curves were not equal for all three compounds.     

Deposition to forests in Europe: most important factors influencing dry deposition and models used for generalisation

Dry deposition of gases and particles to forests is influenced by factors influencing the turbulent transport, such as wind speed, tree height, canopy closure, LAI, etc. as well as by factors influencing surface condition, such as precipitation, relative humidity, global radiation, etc. In this paper, an overview of these factors is given and it is shown which are the most important determining temporal and spatial variation of dry deposition of sodium and sulphur. Furthermore, it is evaluated how well current deposition models are able to describe the temporal and spatial variation in dry deposition. It is concluded that the temporal variation is not modelled well enough, because of limited surface-wetness exchange parameterisations. The influence of forest characteristics are modelled reasonably well, provided enough data describing the forests and the spatial variation in concentration is available. For Europe these data are not available. The means to decrease the atmospheric deposition through forest management is discussed.