A screening tool for vulnerability assessment of pesticide leaching to groundwater for the islands of Hawaii, USA

Abstract

This paper describes an updated version of a screening tool for groundwater vulnerability assessment to evaluate pesticide leaching to groundwater, based on a revised version of the attenuation factor. The tool has been implemented in a geographical information system (GIS) covering the major islands of the state of Hawaii, USA. The Hawaii Department of Agriculture currently uses the tool in their pesticide evaluation process as a first-tier screening tool. The basic soil properties and pesticide properties necessary to compute the index, and estimates of their uncertainty, are included in the GIS. Uncertainties in soil and pesticide properties are accounted for using first-order uncertainty analysis. Classifications of pesticides as 'likely', 'uncertain' or 'unlikely' to leach are made on the basis of the uncertainty and a comparison of the revised attenuation factor with values and uncertainties of two reference chemicals. The reference chemicals represent what are considered to be a 'leachable' and a 'non-leachable' pesticide under Hawaii conditions. It is concluded that the tool is suitable for screening new and already used pesticides for the islands of Hawaii. However, the tool is associated with uncertainties that are not accounted for, so a conservative approach with respect to interpretation of the results and selection of pesticide parameters used in the tool is recommended.

Applying a statewide geospatial leaching tool for assessing soil vulnerability ratings for agrochemicals across the contiguous United States

“…The chemical database of volatile and non-volatile chemicals was newly developed for the regional pollutant leaching assessment in the State of Hawaii (Ki and Ray, 2015;Stenemo et al, 2007). This database was constructed from various data sources including the Pesticides Properties DataBase of the Agriculture and Environment Research Unit in the United Kingdom (so-called PPDB; UH, 2013), the Pesticide Properties Database of the USDA-Agricultural Research Service (so-called PPD; Herner and Acock, 2003), and the handbook on chemicals (Mackay et al, 2006).…”

“…On the other hand, simple models that require a reduced number of input parameters may delineate the risk of contaminants over large areas, ensuring a rapid diagnosis of soil and groundwater vulnerability (Ki and Ray, 2015;Stenemo et al, 2007). There are some straightforward tools for assessing the leaching potential of pesticides by different input parameters and screening algorithms.…”

“…Screening Concentration In GROund Water (SCI-GROW; Pereira et al, 2014), Windows Pesticide Screening Tool (WIN-PST; Brown et al, 2011), and statistical regression models of regional and national scales (Stackelberg et al, 2012) are the tools offered at the federal level from the US Environmental Protection Agency (USEPA), Department of Agriculture (USDA), and Geological Survey (USGS), respectively. Attenuation factor (AF), implemented at the State of Hawaii in the US, is a state-level tool used for pesticide evaluation procedure such as pesticide registration and certification (Ki and Ray, 2015;Stenemo et al, 2007). All these tools, except for regression models of the USGS that used additional parameters of watershed characteristics (e.g., air temperature, prevalence of artificial drainage, etc.…”

Pesticide sorption and leaching potential on three Hawaiian soils

“…This approach uses reference chemicals to determine a pesticide's leachability classification (i.e. unlikely, uncertain, likely) and accounts for uncertainty of model parameters in its estimation (Stenemo et al, 2007). This index-based tool and others like it [e.g.…”

“…To determine their leaching potentials, the measured sorption coefficients of the herbicides were used to calculate the corresponding t 1/2 values required to qualify as a "leacher" (GUS index) (Gustafson, 1989). The leaching potentials of these chemicals were then assessed using the CLEARS leaching tool (Stenemo et al, 2007).…”