A comparison of results from two test methods for assessing the toxicity of aminotriazole to Selenastrum capricornutum

Two different test methods for assessing the toxicity of aminotriazole to Selenastrum capricornutum are compared. Growth medium composition is demonstrated to have a significant effect on the toxicity of aminotriazole.     

Sustainable watershed management: an international multi-watershed case study

Global freshwater resources are being increasingly polluted and depleted, threatening sustainable development and human and ecosystem health. Utilizing case studies from 4 different watersheds in the United States, Japan, Switzerland, and Brazil, this paper identifies the most relevant sustainability deficits and derives general vectors for more sustainable water management. As a consequence of the demographic and economic developments experienced in the last few decades, each watershed has suffered declines in water quality, streamflow and biotic resources. However, the extent and the cultural perception of these water-related problems vary substantially in the different watersheds, leading to specific water-management strategies. In industrialized countries, exemplified by the US, Switzerland, and Japan, these strategies have primarily consisted of finance- and energy-intensive technologies, allowing these countries to meet water requirements while minimizing human health risks. But, from a sustainability point of view, such strategies, relying on limited natural resources, are not long-term solutions. For newly industrialized countries such as Brazil, expensive technologies for water management are often not economically feasible, thus limiting the extent to which newly industrialized and developing countries can utilize the expertise offered by the industrialized world. Sustainable water management has to be achieved by a common learning process involving industrialized, newly industrialized, and developing countries, following general sustainability guidelines as exemplified in this paper.     

Factors affecting mass transfer limited biodegradation in saturated porous media

Microbial degradation rates in the subsurface are not only limited by the physiological capacity of the organisms, but also by inefficient supply of nutrients to the microbes. Although mass transfer limitation of biodegradation in the subsurface has been postulated for years, experimental evidence is still scarce. In the column experiments described here, diffusive transport of 4-nitroanisole from the bulk solution to cells of Rhodococcus opacus strain AS2 immobilized on glass beads or sand appeared to be responsible for the slow transformation rates observed. Assuming steady state, we applied a coupled transformation/transport equation to these data (Best equation) and apparent bead-related mass transfer coefficients were found to increase in proportion to the surface area covered with bacteria. This implies that mass transfer coefficients for individual cells remained constant. In an idealized oligotrophic environment where cells are only loosely clustered and do not shield each other, we would therefore expect biodegradation rates to be independent from the longitudinal distribution of the total biomass along a given flow path. Moreover, apparent mass transfer coefficients increased with the grain size of the column fillings, but did not change upon varying the flow rate. With a limiting external transport step, overall transformation fluxes do not become saturated at concentrations as low as predicted for Michaelis-Menten-type kinetics. Mass transfer limitation thus offers a justification for the common assumption that biodegradation rates in the subsurface follow first order kinetics in a wide concentration range.     

流域的可持续管理:国际多个流域的案例研究

全球淡水资源正在不断受到污染和亏耗,威胁着可持续发展及人类和生态系统的健康.本文通过美国、日本、瑞士和巴西四个不同流域的案例研究,阐述了与淡水资源密切相关的可持续发展中的缺陷,指明了水资源可持续管理的总体方向.由于近几十年来人口的增长和经济的发展,每个流域的水质、流量和生物资源量都在下降.但是对于不同的流域来说,与水有关的这些问题的严重程度和文化观念大不相同,因而形成各自独特的水资源管理政策.在工业化国家,例如美国、瑞士和日本,这类政策允许采用资金密集型和能源密集型技术,使得这些国家在满足其水资源需求的同时还能尽量降低人类健康风险.然而,从可持续发展的观点看,以有限的自然资源为基础制定的这类政策,并非长久之计.对于新兴工业化国家(如巴西)来说,昂贵的水资源管理技术在经济上常常行不通,因而限制了新兴工业化国家和发展中国家对发达国家提供的技术的利用程度.要实现水资源的可持续管理,发达国家、新兴工业化国家和发展中国家都需要经历一个学习的过程,同时还需要遵循本文介绍的可持续发展的通用原则.     

Octachlorodibenzo-p-dioxin in wood treatment materials and treated wood

The octachlorodibenzo-p-dioxin (OCDD) concentrations have been determined in aged samples of commercial pentachlorophenol (PCP), in wood protection formulations containing PCP and in wood treated with PCP as a preservative or as an anti-sapstain treatment. The concentrations of OCDD found in the various samples are within the range expected from the amount of commercial PCP initially present in the samples. In view of the known stability of OCDD the results are interpreted as indicating that the formulation, treatment and ageing processes have not led to any substantial conversion of PCP to OCDD; although one result indicates that outdoor exposure of treated samples increased the OCDD concentration by a factor of approximately 2 after $\text{3}\text{1}\text{2}$ years. Analysis of aged samples of treated wood indicate that OCDD is lost much less rapidly from the wood than PCP.     

Analysis of polychlorobiphenyls from used transformers for polychlorodibenzofurans

The results of analyses for polychlorodibenzofuran (PCDF) content in two samples of polychlorobiphenyl (PCB) from used electrical transformers are presented and discussed. In neither sample was there evidence for enhanced PCDF concentrations even though one of them had been subjected to overheating while in service.     

Polychlorodibenzo-p-dioxins and dibenzofurans in technical pentachlorophenol - results of a collaborative analytical exercise

Results of analyses of eight samples of technical pentachlorophenol conducted by three different analytical methods are presented and discussed.     

Long term changes in polychlorodibenzo-p-dioxin concentrations in wood treated with technical pentachlorophenol

Wood samples treated with technical pentachlorophenol (PCP), technical sodium pentachlorophenoxide (NaPCP) and octachlorodibenzo-p-dioxin have been exposed outdoors for periods up to $\text{2}\text{1}\text{2}$ years. Analysis of extracts from the samples show that photolytic reductive dechlorination of highly chlorinated dibenzo-p-dioxins to less chlorinated isomers occurs. However there is no discernible increase in polychlorodibenzo-p-dioxin concentrations in the technical PCP treated wood presumably because further photolytic reactions and volatilisation compete effectively with the photolytic formation. There is no evidence for formation of octachlorodibenzo-p-dioxin (OCDD) in technical PCP treated wood in this study, probably because photolytic destruction and volatilisation compete effectively with formation reactions when the initial OCDD concentration is relatively high.