Regression models for octanol‐water partition coefficients,and for bioconcentration in fish

Octanol‐water partition coefficients (P) of a number of organochlorine insecticides (OCs) are presented. The merits of log‐log regressions between experimental ? values and calculated estimates of P, solute activity coefficients in water, solute molecular surface area data, and reversed‐phase liquid‐chromatographic net retention data, are critically evaluated for several classes of pollutants: polycyclic aromatic hydrocarbons (PAHs), chlorinated benzenes, chlorinated biphenyls and OCs. Special attention is paid to the predictive accuracy of such semi‐empirical regressions in connection with possible effects of solute molecular shape and polarity.

Finally, bioconcentration and ‐accumulation of hydrophobic pollutants in fish are briefly discussed.     

Arsenic species in the well water and sediments of the blackfoot disease area in Taiwan

The blackfoot disease (BFD) observed in southwestern Taiwan is due to drinking high arsenic concentrations in well water. This paper presents some results concerning the distributions of arsenic species in water and sediments collected in the BFD (well, river and coastal) area and the background (lake and ocean) area for comparison. The results show that the concentrations of arsenate (870 ± 26 ug/L) and arsenite (70.2 ± 2.6 ug/ L) in well waters, and the contents of arsenic (1640 ug/g) with high percentage of easily reducible (Fe and Mn oxides, 91.7%) and exchangeable and carbonate (4.6%) phases in well sediments were much higher than those in river, lake and coastal samples. Low arsenic (3.46–31.8 ug/g) with high percentages (73.8–97.3%) of detritus and minerals phase with low percentages (0.4–9.8%) of total carbonate and exchangeable phases were found in the river and coastal samples in the BFD area as well as the lake and ocean samples in background area. It might suggest that the higher concentrations of toxic As(III) in well water and arsenic with higher values of easily reducible, carbonate and exchangeable phases in the well sediments, combined with the higher values of dissolved organic carbon, humic and fulvic acids and aromatic carbon as well as the higher fluorescence indensity in the well water are the key factors to cause the BFD in Taiwan.     

Ground water pollution by pesticides at the watershed‐soil catena scale: Lindane at the lower Colorado river basin (Argentina)

The movement of Lindane from application points at the surface soil towards the underground water and further transport within this compartment at the watershed‐soil catena scale, was inspected by measurements of the pesticide concentration in soil water at a controlled experiment where it was applied at a usual label dose. The concentrations of Lindane in soil water and the upper phreatic level were also measured at successive dates in samples obtained from a net of phreatimeter probes distributed over the area (1,500 km²) of the lower Colorado River basin (Bs. Aires, Argentina). The location of cultivated‐irrigated areas within the watershed was inferred from NDVI (Normalized Difference Vegetation Index)‐1 km‐10 day AVHRR images obtained at successive dates during the irrigation season. Feasible paths of underground gravitational water flows were computed by means of a GIS‐simulation model on the basis of local terrain slopes and aspects. The pattern of Lindane distribution over the basin was explained on the basis of the distribution of diffuse sources, the patterns of percolation and groundwater flows and the thermodynamic characteristics of the pesticide.     

Determination and QSPR analysis of log Kow and log Koc for fluorine containing benzene derivatives

Octanol‐water partition coefficients (Kow) and soil organic carbon sorption coefficients (Koc) were determined for 14 fluorinated benzene derivatives. Quantitative structure‐property relationships were developed using molecular connectivity indices and quantum chemical parameters to analyze the most significant factors influencing these physico‐chemical properties of the compounds. The substitution by F in benzene derivatives has greater influence on Koc than on Kow.     

Higher education in urban environmental management: a new programme at the Asian Institute of Technology,Bangkok

Environmental management and planning is now considered as a new field of professional expertise. There are even professional associations for interested professionals. To date, urban environmental management has been regarded as a subdiscipline of environmental management, but since the Rio Conference in 1992, with the new focus of urban management on environmental problems, it can itself be considered as a professional field. This paper traces the emergence of the field and tries to identify the new skills required for it. The question of formal training, in higher education, for a new type of professional is raised and discussed. It refers at length to an initiative taken by the Asian Institute of Technology (Bangkok) to propose and offer a new graduate programme in this discipline, and draws on the author's experience of an Asian workshop (Bangkok, May 1993) aimed at defining the need for such a new profession in Asia.     

Interactions Among the Copper Species and Forms in Sea Water/Sediments and Copper Bioaccumulation in Oysters

Abstract

Earlier papers indicated that the first incident of green discoloration in oysters (Crassostrea gigas) and the mass mortality observed in 1986 along the Taiwan Erhjin Chi coastal area were caused by the higher contents of total copper and copper species (mainly bioavailable and free ion) in sea water. the copper in sea water would be sorbed by suspended matter and transferred to sediments, and the copper in the sediments would also be desorbed to sea water. Processes of copper adsorption and desorption are the major factors influencing the contents of total copper and copper species in sea water and sediments. in this study, the Erhjin Chi sediments were mixed with sea water by a shaker technique. When the mixture was shaken for one hour, analogous to tidal mixing in estuaries, only copper desorption from sediments was observed. If the shaking time is increased for more than 3 hours, the copper released from the sediments was resorbed to the remaining solid phases. the higher the contents of mud (91.71%) and total copper (701 mg kg^?1) in sediments, the higher the copper desorption rate (1.86 ppm hr^?1) and copper adsorption rate (0.50 ppm hr^?1) were observed. in sediments containing lower mud (0.80%) and lower copper (43.5 mg kg^?1), the copper desorption and adsorption rates were 0.83 ppm hr^?1 and 0.22 ppm hr^?1, respectively. the interactions among the total copper and copper species in sea water and sediments, chemical and ecological parameters, and copper bioaccumulation in oysters in the Erhjin Chi estuarine and coastal area are also discussed.     

Applicability of Montreal Process Criterion 4 — soil and water conservation — to rangeland sustainability

SUMMARY

Criterion 4 of the Montreal Process addresses the conservation of soil and water resources as a way to assess the sustainability of a nation's forests. For the most part, the indicators under this criterion are relevant to rangelands. The area and percent of rangeland with significant soil erosion apply equally well to both biomes. Percent of streams with flow rates and timing outside its range of historical variation is also equally important, although a measure of proper functioning and condition may provide a better measure of the indicator. The area and percent of rangeland with diminished soil productive capability because of a loss of reduced organic matter or changed physical characteristics can be useful indicators locally and regionally.     

A critique of ethical and social issues of genetically modified crops

SUMMARY

The ethical and social issues of genetically modified crops as reported by the Nuffield Bioethics Committee are summarised. A critique of their findings is presented. It is argued that the apparent benefits are outweighed by the ecological, social and economic costs, and that the yields of some genetically modified crops are poorer when compared to conventional species. Furthermore, the current regulations are far too lax for consumer protection. There is an urgent need for a critical and disinterested review of the scientific basis of the research.     

Organic farmers in islands: Agricultural management and attitude towards the environment

SUMMARY

This study explores differences among organic farmers who live in islands and have isolated small-size operations. The relationships between farmers' characteristics and attitudes and farm management were interpreted by studying how they manage their land, their attitudes towards the environment and alternative farming systems, and their involvement in organic farming. The research was carried out using questionnaires addressed to organic farmers on the island of Thassos. Nonlinear canonical correlation was applied for data analysis. This information could contribute to adjustment of policy decisions for on-farm diversification. Agricultural policy makers should approach organic farmers in northern Thassos (productive irrigated olive orchards with gentle slopes) by enacting standards to reduce the cost of alternative plant protection methods and promoting their products in order to maintain and expand organic farming. They should also approach organic farmers in southern Thassos (less productive, dry cultivated olive orchards with steep slopes, overgrazed and often abandoned) by providing them with the necessary information and appropriate agricultural know-how to effectively manage their farms. Organic farmers with stable off-farm income are more aware of environmental values and consider that they risk less than others in order to gain the benefits of alternative farming systems. However, they should attend training programmes to achieve economic success to allow them to continue farming organically.     

The effect of macrophytes on retention times in a constructed wetland for wastewater treatment

Retention times of treated water in a constructed wetland (CW) with horizontal subsurface flow were determined both in the vegetative and non-vegetative periods of 2005. Tracer experiments were performed using fluorescein, an organic compound detectable at extremely low concentrations. Nominal and tracer retention times were determined and compared. Winter tracer retention time (TRT 194 h) and nominal retention time (nHRT 190 h) were nearly exactly equal, while summer TRT (335 h) was approximately twofold higher than nHRT (158 h). Residence time distribution function (RTD) was used to compare retention times obtained for the vegetative and non-vegetative periods. The obtained results document a significant influence of dense common reed vegetation on retention characteristics of the studied system. Common reed can convert a significant volume of water from liquid to gas via evapotranspiration (ET) and thus prolong water retention times in the system. This is very important both technically and ecologically. Longer retention times mean a longer time for microbiological decay of wastewater. Water converted from liquid to gas causes cooling of the microclimate, which is very important, especially in intensively cultivated areas with a lack of water.