D. Calamari

BIOCONCENTRATION OF ORGANIC CHEMICAL VAPOURS IN PLANT LEAVES : THE AZALEA MODEL

Abstract Experimental data on the accumulation and release kinetics of azalea leaves exposed to constant vapour levels of alachlor, dieldrin and 3,4,3′,4′-tetrachlorobiphenyl are reported. Calculated leaf/air bioconcentration factors for these and other 11 organic chemical vapours are used to improve a correlation with the 1- octanol water and air/water equilibrium partition coefficients.

Chlorinated hydrocarbons in pine needles in Europe : fingerprint for the past and recent use

Pine needles have been demonstrated as a useful monitoring matrix for the evaluation of the tropospheric contamination levels of persistent chlorinated hydrocarbons, such as DDTs, HCHs, and HCB. Global chlorinated hydrocarbon distribution has been investigated with major attention to remote areas, while the factors affecting the distribution trends in regions of major use are less known. Six countries in Europe were analyzed by the transect sampling mode. Homogeneous contamination intensities were present within each transect, and correspondence factor analysis was used for the characterization of the typical distribution patterns

Chlorinated hydrocarbons in plant foliage: an indication of the tropospheric contamination level

Abstract Levels of some chlorinated hydrocarbons in foliage from the Italian peninsula and other countries of the world are reported. The use of plant leaves in monitoring and for the prediction of potential environmental distribution of persistent hydrophobic pollutants is discussed.

QSARs for organotin compounds on Daphnia magna

Abstract A QSAR study has been carried out on several organotin compounds using physical and topological parameters (log P, pKa, 1 x and 1 x v ) and acute toxicity data on Daphnia magna . Equations with significant correlation and high predictive capacity have been found.

Chlorinated dioxins: volatilization from soils and bioconcentration in plant leaves.

Polychlorinated dibenzodioxins (PCDDs) are a group of xenobiotics of extreme environmental interest, by virtue of their high toxic potential, coupled with high bioaffinity and resistance to degradation. One in particular (2,3,7,8tetrachloro dibenzo-p-dioxin, 2,3,7,8-TCDD), is probably the most poisonous substance ever introduced into the environment. PCDDs are not intentionally produced, but mainly arise from combustion processes and certain industrial activities; all the sources of these substances are not yet completely known (Hutzinger and Fiedler 1989). However, loads to the environment are certainly significant as PCDD residues may be found in many different environmental matrices (Jones and Bennet 1989).

Environmental Risk Assessment of Trifluoroacetic Acid

The Montreal Protocol was developed in 1987 in response to concerns that the chlorofluorocarbons (CFCs) were releasing chlorine into the stratosphere and that this chlorine was causing a depletion of stratospheric ozone over Antarctica. This international agreement called for a phase out of these CFCs. Industry initiated a major effort to find replacements that are safe when properly used and safe to the environment. The toxicology and environmental fate of these first generation replacements has been studied extensively. It was determined that the new substances break down in the environment to give predominantly carbon dioxide, water and inorganic salts of chlorine and fluorine. The only exception is that some substances also break down to yield trifluoroacetic acid (HTFA), a substance resistant to further degradation. Recognizing this, industry embarked on a research and assessment program to study the potential effects of trifluoroacetate (TFA) on the environment and to investigate possible degradatio...

A fugacity model of pesticide runoff to surface water : development and validation

Abstract Real field data for pesticide release to surface water are compared with data obtained by simulations of a fugacity-derived model. This was done for several herbicides, applied on to two basins, characterized by different soil properties. The basin were hydraulically isolated and data for water input (rainfall and irrigation), output (outflowing surface water) were recorded, together with concentration of the investigated pesticides in the outflowing water. A fugacity model was developed to take into account the unsteady-state condition of the actual field treatments, since pesticides are typically applied once or twice on the same area. The model allows for several pesticide applications on different areas of the basin at different times and for different reaction half lives, that may change during the simulation time, depending on environmental conditions. A “user friendly” program for Windows® was written, allowing for calculations and plotting of the results. The comparison between predicted and measured concentrations indicated that the model is a useful tool for the prediction of surface water concentration.

Changes in tropospheric composition and air quality.

Reductions in stratospheric ozone (O3) cause increased penetration of ultraviolet-B (UV-B) radiation to the troposphere, and therefore increases in the chemical activity in the lower atmosphere (the troposphere). Tropospheric ozone levels are sensitive to local concentrations of nitrogen oxides (NOx) and hydrocarbons. Model studies suggest that additional UV-B radiation reduces tropospheric ozone in clean environments (low NOx), and increases tropospheric ozone in polluted areas (high NOx). Assuming other factors remain constant, additional UV-B will increase the rate at which primary pollutants are removed from the troposphere. Increased UV-B is expected to increase the concentration of hydroxyl radicals (OH) and result in faster removal of pollutants such as carbon monoxide (CO), methane (CH4), non-methane hydrocarbons (NMHCs), sulfur and nitrogen oxides, hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Concentrations of peroxy radicals (both inorganic and organic) are expected to increase, leading to higher atmospheric levels of hydrogen peroxide (H2O2) and organic peroxides. The effects of UV-B increases on tropospheric O3, OH, methane, CO, and possibly other tropospheric constituents, while not negligible, will be difficult to detect because the concentrations of these species are also influenced by many other variable factors (e.g., emissions). Trifluoroacetic acid (TFA, CF3COOH) is produced in the atmosphere by the degradation of HCFC-123 (CF3CHCl2), HCFC-124 (CF3CHFCl), and HFC-134a (CF3CH2F), which are used as substitutes for ozone-depleting substances. The atmospheric oxidation mechanisms of these replacement compounds are well established. Reported measurements of TFA in rain, rivers, lakes, and oceans show it to be a ubiquitous component of the hydrosphere, present at levels much higher than can be explained by reported sources. The levels of TFA produced by the atmospheric degradation of HFCs and HCFCs emitted up to the year 2020 are estimated to be orders of magnitude below those of concern, and to make only a minor contribution to the current environmental burden of TFA. No significant effects on humans or the environment have been identified from TFA produced by atmospheric degradation of HCFCs and HFCs. Numerous standard short-term studies have shown that TFA has, at most, moderate toxicity.

A proposal to define quality objectives for aquatic life for mixtures of chemical substances

Abstract The need for Water Quality Objectives for chemical substances in combination is recognized. Fundamental concepts for the assessment of aquatic toxicity of mixtures of chemicals are described and a short review on avaiable information on mixture effects and on problems to extend the Water Quality Objective principles from single chemicals to a mixture is given. Finally, a Water Quality Objective for mixtures of chemicals with similar modes of action is proposed and some criteria and examples for grouping different chemical substances are suggested.

The use of terrestrial plant biomass as a parameter in the fugacity model

Abstract A new compartment, the terrestrial plant biomass, is proposed for inclusion in the fugacity model. Two possibilities of calculation have been developed and exemplified: the first considers the plant as a whole, the second takes into account foliage, trunk and roots separately.