Significance of the Long Range Transport of Pesticides in the Atmosphere

Abstract

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 RECOMMENDATIONSBased 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.

Current-Use and Legacy Pesticide History in the Austfonna Ice Cap, Svalbard, Norway

“…The core was analyzed for density, δ 18 O, major ions, conductivity, and 137 Cs which provided various dating reference horizons (22). The resulting accumulation rate is ∼0.5 m (H2O equivalent) yr -1 .…”

The aerosol-climate model ECHAM5-HAM

“…Non-eruptive emissions are distributed between the volcano height and one third below, eruptive emissions are distributed 500 to 1500 m above the volcano height (ACB). Anthropogenic sulfur emissions are considered from fossil-fuel and bio-fuel emissions (Cofala et al, 2005) and from vegetation fires (van der Werf et al, 2003). Emissions from industry, power-plants, and shipping are distributed between 100 and 300 m above surface (ACB).…”

“…For carbonaceous emissions from vegetation fires (van der Werf et al, 2003) we assumer=0.075 µm and σ =1.59 (adapted from ACB valuesr=0.04 µm and σ =1.8) and injection heights as described in Section 2.3.1. The biogenic monoterpene emissions of Guenther et al (1995), are scaled by the factor 0.15 to estimate the production of Secondary Organic Aerosol (SOA) from biogenic sources (ACB).…”

“…Furthermore, heterogeneous reactions on the aerosol surface and in liquid aerosol particles interact with the chemistry of the atmosphere (Ravishankara, 1997;Andreae and Crutzen, 1997;Crutzen, 1996;Dentener and Crutzen, 1993). Pollutants, such as DDT, condense on aerosol particles so that their transport and deposition are largely determined by the aerosol pathways (van Pul et al, 1998;Unsworth et al, 1999). Moreover, the deposition of aerosol in the ocean plays an important role in the biogeochemical cycle of the oceans (Vink and Measures, 2001;Johnson et al, 1997).…”

Validation of the AGDISP model for predicting airborne atrazine spray drift: A South African ground application case study

“…Although most pesticides are designed to have low persistence in the environment, many, including triazines, are sufficiently stable to undergo atmospheric transport at a regional or global scale (van Dijk & Guicherit, 1999). Apart from drift due to turbulent air masses during application, pesticide residues may become concentrated in atmospheric inversions or stable air masses, or be transported over long distances Unsworth et al, 1999). This phenomenon makes pesticide spray drift an important environmental concern.…”