Evaluation of the Impact of and Management Strategies for Diazinon and Chlorpyrifos in Newport Bay

Abstract

Our study evaluated the efficacy of strategic management alternatives designed to reduce the level of toxicity in urban runoff being discharged within the Newport Bay Watershed, in Orange County, California. We first identified the key pollutants responsible for the aquatic toxicity in freshwater and saltwater environments, which were determined to be two organophosphate (OP) pesticides, Diazinon and Chlorpyrifos. We traced the major contributors of these pesticides to a corresponding landuse and developed export rate coefficients for each pesticide over coarse landuse classes. Model-based predictions were then used to evaluate the persistence of these pollutants over an array of scenarios, simulating base-case, policy-related usage restrictions and management practices aimed at improving water quality. Our watershed modeling analysis established that after the phase-out Diazinon would persist in all stormflow events in exceedance of the numeric criteria for aquatic toxicity while Chlorpyrifos concentrations appeared to be more moderate with respect to the criterion limits. Based on the results of our cost-effective analysis, we recommend the installation of several infiltration basins in conjunction with supplemental public education programs as a means to reduce the OP pesticiderelated toxicity. In order to maintain and restore the ecological integrity of the Bay, we also recommend further usage restrictions on both pesticides throughout the watershed.

Uncertainty assessment in watershed‐scale water quality modeling and management: 1. Framework and application of generalized likelihood uncertainty estimation (GLUE) approach

“…Model simulation was performed for a 3‐year period from 1 October 1996 to 30 September 1998, using weather data from the National Climate Data Center station Piru 2 ESE (34°24'N, 118°45'W) located within the Santa Clara River Watershed. The application rates of diazinon on different land uses, ranging from 0.8 g/ha‐month to 2.7 g/ha‐month (see Table 1), were estimated from data for the Newport Bay area (Orange County, CA) [ California Department of Pesticide Regulation , 1998; Harrison et al , 2005].…”

Uncertainty assessment in watershed‐scale water quality modeling and management: 2. Management objectives constrained analysis of uncertainty (MOCAU)

“…Model simulation was performed for the 3‐year period from 1 October 1996 to 30 September 1999, using weather data from the National Climate Data Center station Piru 2 ESE (34°24′N, 118°45′W) located within the Santa Clara River Watershed. The application rates of diazinon on different land uses, ranging from 0.8 g/ha‐month to 2.7 g/ha‐month, were estimated from data for the Newport Bay area (Orange County, CA) [ California Department of Pesticide Regulation , 1998; Harrison et al , 2005].…”

Chemical Introductions to Estuarine and Coastal Systems

“…However, in many communities around the world, storm water runoff flows directly into water bodies without passing through a collecting sewer (Brady et al, 2006), or it is collected in combined sewer systems (Welker, 2007a(Welker, , 2007b. While the majority of this load originates from agricul tural practices, locally the urban pesticide load can, in some cases, be rather significant as well (Harrison et al, 2005). While the majority of this load originates from agricul tural practices, locally the urban pesticide load can, in some cases, be rather significant as well (Harrison et al, 2005).…”