Papers by Ricardo Diaz Diaz
Environmental Toxicology and Chemistry, 2001
Currently, no guidelines cover use of pesticides in the forested areas of the Canary island of Te... more Currently, no guidelines cover use of pesticides in the forested areas of the Canary island of Tenerife. An index-based model (Li) was used to rank the leaching potential of 50 pesticides that are, or could be, used for management purposes in the pine forest areas of Tenerife. Once the pesticides with the greatest leaching potential were identified, regional-scale groundwater vulnerability assessments, with consideration for data uncertainties, were generated using soil, climatic, and chemical information in a geographic information system framework for all pine forest areas of the island. Process-based simulations with the pesticide root zone model for the areas and pesticides of highest vulnerability were conducted to quantitatively characterize the leaching potentials. Carbofuran, hexazinone, picloram, tebuthiuron, and triclopyr were each identified as being potential leachers.
Biotherapy (Dordrecht, Netherlands), 1998
Regional-Scale Leaching Assessments for Tenerife: Effect of Data Uncertainties
Journal of Environment Quality, 2000
ABSTRACT This paper reports assessments of nonpoint-source (NPS) ground water vulnerability due t... more ABSTRACT This paper reports assessments of nonpoint-source (NPS) ground water vulnerability due to pesticide leaching for the Canary Island of Tenerife. Index-based estimates of contamination potential were made for the pesticides Carbofuran and ...
Journal of Environment Quality, 2012
Precious groundwater resources across the United States have been contaminated due to decades-lon... more Precious groundwater resources across the United States have been contaminated due to decades-long nonpoint-source applications of agricultural chemicals. Assessing the impact of past, ongoing, and future chemical applications for large-scale agriculture operations is timely for designing best-management practices to prevent subsurface pollution. Presented here are the results from a series of regional-scale vulnerability assessments for the San Joaquin Valley (SJV). Two relatively simple indices, the retardation and attenuation factors, are used to estimate near-surface vulnerabilities based on the chemical properties of 32 pesticides and the variability of both soil characteristics and recharge rates across the SJV. Th e uncertainties inherit to these assessments, derived from the uncertainties within the chemical and soil data bases, are estimated using fi rst-order analyses. Th e results are used to screen and rank the chemicals based on mobility and leaching potential, without and with consideration of data-related uncertainties. Chemicals of historic high visibility in the SJV (e.g., atrazine, DBCP [dibromochloropropane], ethylene dibromide, and simazine) are ranked in the top half of those considered. Vulnerability maps generated for atrazine and DBCP, featured for their legacy status in the study area, clearly illustrate variations within and across the assessments. For example, the leaching potential is greater for DBCP than for atrazine, the leaching potential for DBCP is greater for the spatially variable recharge values than for the average recharge rate, and the leaching potentials for both DBCP and atrazine are greater for the annual recharge estimates than for the monthly recharge estimates. Th e data-related uncertainties identifi ed in this study can be signifi cant, targeting opportunities for improving future vulnerability assessments.
Journal of Contaminant Hydrology, 1999
This paper reports an index-based regional-scale characterization of non-point source groundwater... more This paper reports an index-based regional-scale characterization of non-point source groundwater contamination potential for the agricultural areas on the Canary Island of Tenerife. The relative leaching potential for 24 pesticides was quantitatively assessed and ranked using the Ž . Leaching index Li for the soil, landcover, and recharge conditions in Tenerife. The uncertainty in the Li estimates, due to uncertainties in the soil, recharge, and chemical data, were accounted for using first-order uncertainty analysis. Several of the pesticides considered in this study were Ž assessed to be potential leachers. The soil insecticide Carbofuran 2,3-dihydro-2,2-dimethyl-7-ben-. zofuranyl-n-methylcarbamate was found to have the greatest leaching potential for the soil, landcover, and recharge conditions across Tenerife. q 1999 Elsevier Science B.V. All rights reserved.
Journal of Applied …, 2003
Since flow cytometry allows rapid, simultaneous and quantitative measurements related to cell mor... more Since flow cytometry allows rapid, simultaneous and quantitative measurements related to cell morphology and physiologicy, the lipid-specific fluorescent dye, Nile Red, was employed for the in vivo lipid quantification of Crypthecodinium cohnii, a heterotrophic marine dinoflagellate rich in polyunsaturated long chain fatty acids. The fluorescence signal was linearly correlated with the neutral and polar lipid content as determined by gravimetric techniques. A significant correlation of NR signal was also observed between the polar to neutral lipid ratio and docohexaenoic acid per cell. The results demonstrate a method for rapid lipid quantification that can be used in the selection, isolation and culture control of C. cohnii clones with high lipid and DHA content.
Journal of the American Water Resources Association, 2000
Agriculture is the leading cause of regional-scale nonpoint source (NPS) pollution in the world t... more Agriculture is the leading cause of regional-scale nonpoint source (NPS) pollution in the world today. Indices of pesticide leaching in the vadose zone are well suited for estimating the spatial accumulation and distribution of NPS pollutants in the near surface. In this study the Attenuation Factor (AF) and the Leaching index (Li) are used to assess the near-surface leaching potential for 32 important agrochemicals for world average agricultural soil properties and recharge rates. The AF and Li indices both require the same input data and appear to work well for nonpolar chemicals. In the effort reported here the AF and Li indices produced similar results for the 32 agrochemicals. Pesticides with high and moderate leaching potential are identified. The AF estimates were more constant than the Li estimates for changes in the compliance depth and recharge rate. The AF index is simpler to use than the Li index and, therefore, is more likely to be employed in the future for screening/ranking agrochemicals relative to regional-scale NPS ground water vulnerability. (KEY TERMS: Attenuation Factor (AF); ground water vulnerability; Leaching index (Li); nonpoint source (NPS) pollution; pesticide leaching.)
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Papers by Ricardo Diaz Diaz