Photodegradation of TCDD in soil containing organic solvents

Studies were conducted to understand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) behaviour in the near surface zone in relation to the operating conditions: UV-intensity, temperature and exposure modes. Comparisons have been made between Oriel lamp exposure tests and sunlight exposure tests. Under Oriel lamp exposure, the convective transport of TCDD, which depends on operating temperature, was the limiting factor in the cleanup process. The product differences between Oriel exposure tests and sunlight exposure tests probably result from the difference of UV-intensities.     

Material suppliers and industrial metabolism

Life Cycle Assessment (LCA) is not sufficiently tailored to the analysis of strategic environmental problems of material suppliers. Sustainable development calls for a reduction by a factor of 10 to 20 in the material intensity of the economy, a situation which leads to dramatic shifts in markets for raw materials. Furthermore, a material supplier might have major improvement options in the material’s numerous downstream uses. LCAs, however, can’t cover these two aspects. An adapted form of Substance Flow Analysis (SFA) may be an answer. This approach defines a system in relation to the flow of a specific material through society. All environmental interventions related to the material are inventoried. An emission evaluation indicates the dominant environmental bottlenecks, given the current market volume of each application of the material. This helps to identify improvement options and strategic choices in market portfolios. Scenario analysis on potential measures can further indicate changes of material flows — and thus markets — in the system. The approach is illustrated with a case study on chlorine.     

巴西圣保罗州莫日-瓜苏河流流域中的汞:根据210Pb测年剖面估计的沿海泻湖与河流贡献之间的联系

引言 莫日-瓜苏河位于纳斯吉拉斯州,海拔高1450m.流淌470km后,该河流注入圣保罗州的帕尔杜河.其流域总面积为1400km2,其中有86%位于圣保罗州,包括一个工业化地区[1].     

Analysis of Lower Green Bay and Fox River,Collingwood Harbour,Spanish Harbour,and the Metro Toronto and Region remedial action plan (RAP) processes

This article presents a model of remedial action planning, which includes four key variables that determine progress in plan development and implementation and explain the differing level of achievement in individual sites. The model is illustrated by the characteristics and developments of four remedial action plan (RAP) processes (Lower Green Bay and Fox River, Collingwood Harbour, Spanish Harbour, and the Metro Toronto and Region RAPs). Differences in the local context of the plans have, to a significant degree, predisposed individual planning and implementation experiences. Local context includes three variables, namely geographical—technical and sociopolitical aspects and the previous history of water pollution management in the area. RAP precursors are a necessary precondition for progress in planning and substantive achievements. While there is a tendency that most geographically focused RAPs in administratively simple areas accomplish most, the motivation and political clout of RAP participants are strongly intervening factors. Resource input from upper levels of government, in particular financial commitment for plan implementation, is the fourth necessary ingredient for progress due to the RAPs' weak regulatory and institutional framework. Unfortunately, upper levels of government have shown widespread reluctance to lead in remedial action planning. This was only in part offset by local commitment and support for RAP and its cause.     

Ecology of subtropical hermit crabs in S.W. Madagascar: cluster structure and function

The Madagascar coast (both) has a higher density and diversity of hermit crabs than is known from any other locality in the western Indian Ocean. Of the 20 species occurring at Anakao (S.W. Madagascar), 11 aggregated into clusters, including all but one of the species above the subtidal zone. The mean number of hermit crabs and species in clusters varied with several spatial parameters and time. Over 80% of the community clustered in certain habitats in particular tidal zones, whilst as low as 3% clustered in others. The highest intensity of clustering with shore zone was coincident with peak numbers of hermit crabs. The initiation and duration of clusters of hermit crabs above the eulittoral was driven by circadian rhythms, whilst those in the eulittoral were governed by tidal state. Clusters above and below the eulittoral were longer in duration, and those in the subtidal were more temporally variable than those above it. Certain pairs of species showed positive correlations of occurrence and (more rarely) of abundance, and all the correlations (of occurrence) of one, Clibanarius eurysternus, were negative. Positive correlations of occurrence were related to the degree of shell-use commonality between species pairs. Eulittoral species clustered with other individuals of approximately similar size and exchanged shells upon cluster disintegration. There was evidence of a dehydration-reduction function to shell clustering in addition to shell-exchange facilitation. The highly variable species-specific strategies of clustering may be important in alleviating both intra- and interspecific competition in assemblages of similar and highly abundant species.     

DOWNSTREAM CHANNEL GEOMETRY FOR USE IN PLANNING-LEVEL MODELS1

ABSTRACT: There is considerable potential for use of channel dimension data in planning-level models for resource and impact assessment. The channel dimension data is used to route flows and sediment through the basin. The cost of obtaining actual surveyed data for large watersheds is typically prohibitive. Predictive equations have been developed based on 674 stations from watersheds across the United States which encompass a wide variety of channel types and sizes. These equations were tested against an independent data set and found to be adequate for use in planning-level models. Future research is advocated which would include data from regions and stream types not included in this study.     

ERODIBILITY OF URBAN BEDROCK AND ALLUVIAL CHANNELS,NORTH TEXAS1

ABSTRACT: Major erosion of urban stream channels is found in smaller basins in the North Texas study area with contributing drainage areas of less than ten square miles. Within these basins, four basic channel types are identified based on bed and bank lithologies: alluvial banks and bottoms, alluvial banks and gravel bottoms, alluvial banks with rock bottoms, and rock banks with rock bottoms. Most channels (75 percent) have alluvial banks with gravel or rock bottoms. Channel slopes are steep (.38 to.76 percent). Rock consists predominantly of shale and limestone. Channel cross sections are divided into the following four zones based on weathering, scour and entrainment mechanisms: soil zone, slake zone, rock zone and bed material zone. Erodibility of the channels is determined using multiple techniques including reach hydraulics and stream power computations, submerged jet testing, slab entrainment thresholds, and slake durability rates. Procedures are based on both empirical and modeled time series estimates of channel erosion. Field and modeled results support rates of erosion of up to four inches per year. Rates are tied to flow regime, climate, and type of channel bed and banks.