Cycling of DDT in the global environment 1950–2002: World ocean returns the pollutant (original) (raw)
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“New” DDT inputs to North America: Atmospheric deposition
Chemosphere, 1985
Measurement of untransformed (p,p'-and o,p'-) DDT in rain, snow, and peat indicates that input of "new" DDT continues over a large portion of eastern North America. Peat cores obtained from ombrotrophic bogs indicate that current atmospherically derived fluxes are about 10-20% of those which occurred during peak DDT usage (-1960).
Significance of the Long Range Transport of Pesticides in the Atmosphere
Pure and Applied Chemistry, 1999
Since the 1960s there has been a growing body of data regarding the presence of pesticides in the atmosphere. The monitoring results obtained show that traces of pesticides may undergo long range transport and be deposited considerable distances away from the treatment areas, including remote areas such as the Arctic and Antarctic regions. Pesticides have been found in air, rain, cloud water, fog and snow. The appearance and subsequent behaviour of pesticides in the atmosphere are complex processes and the concentrations found depend on several variables such as their volatility, photostability, method of application and extent of use. Whilst volatility of pesticides can be linked to their Henry's Law constant this is very much a simplification since it is also influenced by the surfaces treated, e.g. soil or leaves, and by the extent to which aerosols are formed during the application. The disappearance of pesticides from the atmosphere is due to hydrolysis, indirect photolysis via OH ؒ radicals and to deposition in rain. Pesticides which are resistant to hydrolysis and photolysis can be transported over great distances, for example, organochlorine insecticides have been detected in the Arctic regions. In general, concentrations in rainwater are, when detected, in the low or sub g/L range and highest concentrations are found during the time of application. The use of fugacity models has been shown to be a useful approach to predict concentrations in air. Under most conditions the presence of pesticides in air, or rainwater, has no significant effects on nontarget systems, including direct and indirect effects. Exceptions to this are damage by auxintype herbicides to sensitive plants which has resulted on restrictions in their use in certain areas and transient chlorotic spotting thought to be caused by drift of aerosols from application of low rate sulfonyl urea herbicides. For animal species one possible exception has been postulated. This is for persistent organochlorine pesticides in Arctic regions where, due to the very oligotrophic nature of the Arctic ocean, they are more liable to bioaccumulate and be transported in the food web giving enhanced levels in mothers' milk. THE IUPAC COMMISSION ON AGROCHEMICALS AND THE ENVIRONMENT MAKES THE FOLLOWING RECOMMENDATIONS Based on the conclusions from this review, several recommendations for further areas of research are suggested. Since the factors governing the fate and behaviour of pesticides in the atmosphere are the same for any organic contaminant, whether from natural or anthropogenic sources, research studies on pesticides in air should be considered in the same way as any organic contaminant in the atmosphere. 1 Investigations should be encouraged into obtaining a better understanding of cloud chemistry and its role in the long and intermediate transport of organic contaminants, including pesticides. 2 Investigations should be encouraged into the application of fugacity models in the prediction of atmospheric concentrations of organic contaminants, including pesticides, in defined areas due to long range transport. 3 In order to refine and validate current models specifically for pesticides additional investigations are required into: X the chemical reactivity of pesticides, particularly their photodegradation under environmental conditions. X the transfer of pesticides between environmental compartments to give the key factors leading to their occurrence in the atmosphere. X the parameters required to define the 'unit world', i.e. an identified and limited geographic area, for use in fugacity models.
Short and Long Term Fate of Environmental Pollutants and Their Management
2012
There has been an increasing demand of chemical substances during this and the last century. The use of chemicals for a long time has been identified as a negative impact on the environment since it became apparent that residues could be transferred through the food chain; remain in soil or sediment as intractable substances. Chlorinated pesticides stand as a classic case of intractable substances and their residues remain dispersed throughout the world. Even though banned, their use continued because of their effectiveness as insecticides and availability. The effective use of DDT (dichlorodiphenyltrichloroethane) for control against malaria was recognized following its removal but was reinstated for controlled situations. Arsenic is another classic case because its residues from the application of its compounds as insecticides for cattle dips remain as buried residues that are intractable. The soil from such repositories requires remediation. The recognition of problems associated...
Global-scale environmental transport of persistent organic pollutants
Chemosphere, 2001
In order to realistically simulate both chemistry and transport of atmospheric organic pollutants, it is indispensable that the applied models explicitly include coupling between dierent components of the global environment such as atmosphere, hydrosphere, cryosphere and soil system. A model with such properties is presented. The atmospheric part of the model is based on the equations in a general contravariant form which permits easy changes of the coordinate system by rede®ning the metric tensor of a speci®cally employed coordinate system. Considering a need to include explicitly the terrain eects, the terrain following spherical coordinate system is chosen from among many possible coordinate systems. This particular system is a combination of the Gal-Chen coordinates, commonly employed in mesoscale meteorological models, and the spherical coordinates, typical for global atmospheric models. In addition to atmospheric transport, the model also simulates the exchange between air and dierent types of underlying surfaces such as water, soil, snow, and ice. This approach permits a realistic representation of absorption and delayed re-emission of pollutants from the surface to the atmosphere and, consequently, allows to capture hysteresis-like eects of the exchange between the atmosphere and the other components of the system. In this model, the most comprehensive numerical representation of the exchange is that for soil. In particular, the model includes a realistic soil module which simulates both diusion and convection of a tracer driven by evaporation from the soil, precipitation, and gravity. The model is applied to a long-term simulation of the transport of pesticides (hexachlorocyclohexanes in particular). Emission¯uxes from the soil are rigorously computed on the basis of the realistic data of the agricultural application. All four modelled systems, i.e. atmosphere, soil, hydrosphere and cryosphere, are driven by objectively analysed meteorological data supplemented, when necessary, by climatological information. Therefore, the veri®cation against the observed data is possible. The comparison of the model results and the observations taken at remote stations in the Arctic indicates that the presented global modelling system is able to capture both trends and short-term components in the observed time series of the concentrations, and therefore, provides a useful tool for the evaluation of the source± receptor relationships.
BETR North America: A regionally segmented multimedia contaminant fate model for North America
Environmental Science and Pollution Research, 2001
focus is on describing contaminant fate and transport over the entire continent, including transfer, transport and cycling between air, vegetation, soil, surface water, sediments and near-shore coastal water. The BETR North America model is built on a general framework that links individual regional contaminant fate models to create a model that encompasses a larger, spatially heterogeneous area. It can thus address issues of long-range transport of chemicals between regions within the continent. Parameterization of the model to represent the North American environment is ongoing, and is described in the companion paper in this issue by Woodfine et al. Illustrative calculations to describe the fate and transport of toxaphene in North America are described.
Emerging Pollutants – Part I: Occurrence, Fate and Transport
Water Environment Research, 2012
Part I: Occurrence, Fate, and Transport (this literature review) compiles research from 2013 investigating emerging pollutants in wastewater and environmental waters and the sources of emerging pollutants. The paper summarizes important findings on environmental aquatic occurrence, persistence and transport of emerging pollutants in the environment, monitoring approaches, modeling, and regulatory discussions. The paper further mentions updates in our understanding of the toxicological impacts of these compounds where relevant specifically to wastewater. Finally, the paper speaks to the environmental sinks and degradation of pollutants. Part II: Treatment (the companion to this review) includes discussion of water and wastewater treatment technologies on emerging pollutants.
On the Global Distribution of Persistent Organic Pollutants
CHIMIA International Journal for Chemistry, 2003
The global distribution of persistent organic pollutants (POPs) has become one of the main environmental problems in the last decade. This article gives an overview of the main contributions to the knowledge of the atmospheric transport and accumulation mechanisms of POPs in remote areas, based on their analysis in selected environmental compartments from high altitude mountain regions of Europe. The studies indicated that transport and deposition of polycyclic aromatic hydrocarbons are mainly linked to atmospheric particles. Consequently, wet and dry deposition are the main removal processes of these compounds from the atmosphere, resulting in a significant influence of regional sources. In contrast, gas exchange seems to be the main input mechanism of organochlorine compounds from the atmosphere to terrestrial and aquatic systems. For these compounds, an altitude dependence of their accumulation in fish muscle and sediments was detected, with a major retention of the less volatile compounds (vapor pressure ≤ 10-2.5 Pa) in the locations situated at higher altitude, those of lower annual average temperature, whereas no relationship was observed for more volatile OCs. The results represent a new aspect in the Global Distillation Effect theory as proposed for semivolatile persistent pollutants, indicating that this transport mechanism not only involves transfer from low to high latitudes, but also preferential accumulation of the less volatile compounds in high altitude regions of mid-latitude areas.
Environmental Science & Technology, 2005
Annually averaged concentrations and enantiomeric compositions of organochlorine pesticides (OCPs) in air were determined in 2000/2001 at 40 stations across North America using XAD-based passive samplers. Absolute concentration differences across the continent, the skewness and kurtosis of the concentration distribution, the relative abundance of parent compound and metabolites, and the chiral signatures can identify regional sources of OCP to the atmosphere. Specifically, air samples collected in the southeastern United States had elevated concentrations of chlordane-related compounds, higher ratios of transto cis-chlordane and heptachlor to heptachlor epoxide, as well as higher enantiomeric fractions of trans-chlordane as compared to other regions, suggesting continued release of microbially unprocessed chlordane to the regional atmosphere. Similarly, greatly elevated concentrations of p,p′-DDT, low relative abundance of the metabolite DDE, and a racemic composition of o,p′-DDT in samples from southern Mexico and Belize indicate recent use of DDT in these regions. Belize is also a potential source region for dieldrin. Reflecting its continued use in North America, endosulfan is now one of the most abundant and ubiquitous OCPs in the continental atmosphere. In contrast to these OCPs, air concentrations of penta-and hexachlorobenzene vary only by factors of 2-4 across the continent, reflecting a long atmospheric residence time and few primary sources. Atmospheric levels of the chlorobenzenes, R-endosulfan, and p,p′-DDE increase with elevation in the Canadian Rocky Mountains. Empirical travel distances for the OCPs derived from latitudinal concentration profiles are in good agreement with model-derived indicators of longrange transport potential and, in particular, lead to a similar categorization of the OCPs. Large-scale passive air sampling networks are suitable for monitoring compliance with, and effectiveness of, regulatory control measures and for establishing experimentally the atmospheric long-range transport behavior of organic air pollutants.