In Central America, chemical-intensive tropical agriculture takes place in close proximity to highly valued and biologically diverse ecosystems, yet the potential for atmospheric transport of pesticides from plantations to national parks and other reserves is poorly characterized. The specific meteorological conditions of mountain ranges can lead to contaminant convergence at high altitudes, raising particular concern for montane forest ecosystems downwind from pesticide use areas. Here we show, based on a wide-ranging air and soil sampling campaign across Costa Rica, that soils in some neotropical montane forests indeed display much higher concentrations of currently used pesticides than soils elsewhere in the country. Specifically, elevated concentrations of the fungicide chlorothalonil, the herbicide dacthal, and the insecticide metabolite endosulfan sulfate on volcanoes Barva and Poas, lying directly downwind of the extensive banana plantations of the Caribbean lowland, indicate the occurrence of atmospheric transport and wet deposition of pesticides at high altitudes. Calculations with a contaminant fate model, designed for mountain regions and parametrized to the Costa Rican environment, show that chemicals with a log K(AW) between -3 and -5 have a greater potential for accumulation at high altitudes. This enrichment behavior is quantified by the Mountain Contamination Potential and is sensitive to contaminant degradability. The modeling work supports the hypothesis suggested by the field results that it is enhanced precipitation scavenging at high elevations (caused by lower temperatures and governed by K(AW)) that causes pesticides to accumulate in tropical montane areas. By providing for the first time evidence of significant transfer of currently used pesticides to Central American montane cloud forests, this study highlights the need to evaluate the risk that tropical agricultural practices place on the region's ecological reserves.

Abstract-A study of pesticide residues in surface waters and sediments was undertaken in the Suerte River Basin, Costa Rica, that drains into the Tortuguero conservation area. Samples were collected in streams, packing plants, and the Suerte River. The most frequently measured compounds in surface water samples were the fungicides thiabendazole, propiconazole, and imazalil; the nematicides terbufos and cadusafos; and the insecticide chlorpyrifos. At the conservation area, propiconazole was detected in 43% of the samples at concentrations ranging from 0.05 to 1.0 g/L. In 25% of the samples collected at this site, a nematicide (cadusafos, carbofuran, or ethoprophos) was detected (0.06-6.2 g/L). According to this study, most of the insecticide-nematicides analyzed pose a risk for acute or chronic toxicity to aquatic organisms based on the exposure levels and toxicity values from the literature. Ametryn, imazalil, and thiabendazole also exceeded the calculated chronic risk ratio. The most frequently detected compounds in sediments were thiabendazole, chlorpyrifos, imazalil, and propiconazole. The occurrence was higher in the packing plants and streams. Pesticides in waters and sediments of Tortuguero conservation area could pose a threat to this wetland and an additional stress to the endangered species that inhabit this area. More information is needed regarding the distribution and stability of pesticides in the lagoon system as well as of the effects of mixtures of low levels of pesticides and their degradation products on representative species of the Tortuguero ecosystem. Meanwhile, all measures to reduce the emissions of pesticides from the banana plantations and the packing plants should be taken.

No abstract

A survey of the contamination of the physical environment of Costa Rica with banned organochlorine pesticides (OCPs) relied on sampling air and soil at 23 stations acrossthe country in 2004. Average annual air concentrations, determined with XAD-based passive samplers, and surface soil concentrations were generally low when compared to values reported for North and Central America, which is consistent with relatively low historical domestic use and little atmospheric inflow from neighboring countries. Statistical analysis and concentration maps reveal three types of spatial distribution: alpha-hexachlorocyclohexane and p,p'-DDD had a relatively uniform distribution across the country; other DDT-related species were greatly elevated over the national average at Manuel Antonio, a National Park on the Pacific coast; and dieldrin, lindane, and chlordane-related species had higher concentrations in Costa Rica's populated Central Valley. An altitudinal transect of stations in the Central Valley shows declining air-soil concentration ratios with elevation for lindane, likely driven by atmospheric inversions and soil organic carbon content. Enantiomeric composition of chiral OCPs in air and soil was close to racemic, with slight depletion of (-)-alpha-HCH, (-)-cis-chlordane, and (+)-trans-chlordane. Estimated air-soil fugacity fractions are highly uncertain but indicate equilibrium conditions for most OCPs, net volatilization of lindane at some sites, and net deposition for p,p'-DDE. The study demonstrates an approach for quickly evaluating the spatial distribution of OCPs in an understudied area, identifying regionally important contaminants and areas of elevated concentrations.

Air was sampled for one year in the central valley of Costa Rica using an active high-volume sampler as well as passive samplers (PAS) based on polyurethane foam (PUF) disks and XAD-resin filled mesh cylinders. Extracts were analyzed for pesticides that are either banned or currently used in Costa Rican agriculture. Sampling rates for PUF-based passive air samplers, determined from the loss of depuration compounds spiked on the disks prior to deployment averaged 5.9 +/- 0.9 m3 x d(-1) and were higher during the windier dry season than during the rainy season. Sampling rates for the XAD-based passive sampler were determined from the slopes of linear relationships that were observed between the amount of pesticide sequestered in the resin and the length of deployment, which varied from 4 months to 1 year. Those sampling rates increased with decreasing molecular size of a pesticide, and their average of 2.1 +/- 1.5 m3 x d(-1) is higher than rates previously reported for temperate and polar sampling sites. Even though the trends of the sampling rate with molecular size and temperature are consistent with the hypothesis that molecular diffusion controls uptake in passive samplers, the trends are much more pronounced than a direct proportionality between sampling rate and molecular diffusivity would suggest. Air concentrations derived by the three sampling methods are within a factor of 2 of each other, suggesting that properly calibrated PAS can be effective tools for monitoring levels of pesticides in the tropical atmosphere. In particular, HiVol samplers, PUF-disk samplers, and XAD-based passive samplers are suitable for obtaining information on air concentration variability on the time scale of days, seasons and years, respectively. This study represents the first calibration study for the uptake of current use pesticides by passive air samplers.

Abstract-Although pesticide use is high in the Central American region, few studies concerning environmental levels and effects of pesticides in aquatic ecosystems have been conducted. In this review 18 studies were identified, most of which deal exclusively with organochlorine residues, but other chemical groups also were studied and found in tropical aquatic ecosystems. Only five studies considered effects of pesticides on aquatic organisms; four of these examined both the presence of pesticides in environmental substrates and field effects. Major research needs include studies on fate and degradation in tropical conditions; acute and chronic toxicity to native species; effects of temperature, humidity, and other characteristics of tropical conditions on toxicity, as well as effects of pesticides on tropical ecosystems.

No abstract

No abstract