Leaching potentials of four pesticides used for bananas in the Canary Islands

Nonpoint source (NPS) groundwater contamination, that is related to the regional-scale use of agrochemicals, is a major environmental problem. This paper reports preliminary assessments of groundwater vulnerability due to pesticide leaching for areas of banana (Musa balbisiana) silviculture for the Canary Island of Tenerife using simple indites. Estimates of contamination potential were made for the four most commonly used pesticides using the retardation factor (RP) and the attenuation factor (AF). Soil, crop, and recharge maps for Tenerife were overlaid using a geographic information system (GIS) approach, Soil depth, the type of irrigation, soil-pH dependent chemical half-lives, and the method of landcover characterization were each assessed relative to their individual and cumulative impacts on assessing regional-scale NPS groundwater vulnerability. The order of leaching potential, in terms of greatest mobility, for the four chemicals was found to be: (i) carbufuran (2,3-dihydro-2,2-dimethyl-7-benzofluranyl-n-methanylcarbamate), (ii) ethoprophos (O-ethyl-S,S-di-n-propyl-phosphoradithioate), (iii) fenamiphos (ethyl 3-methyl-4-(methylthio)-phenyl1-methylethylphosphoramidate), and (iv) oxamyl (methyl2-(dimethylamino)-N-[[(methylamino)carbony]oxy]-2-oxoethanimi dothioate). The worst-case scenario for groundwater contamination in Tenerife, related to banana silviculture, was found to be carbofuran with furrow irrigation. The best pesticide and irrigation combination to minimize potential groundwater contamination, related to the cultivation of bananas in Tenerife, was oxamyl and drip irrigation. The regional-scale NPS groundwater vulnerability assessments presented were for Tenerife are the first to be made for the island and will he useful for future chemical regulation decisions and for targeting critical areas that may require remediation.