Water quality and evaluation of pesticides in lakes in the Ridge Citrus region of central Florida

Pesticides and nitrate in groundwater underlying citrus croplands, Lake Wales Ridge, central Florida, 1999-2005.

“…However, the pesticide concentrations in the lakes typically were lower than those in groundwater, often by an order of magnitude or more, likely reflecting chemical degradation and dilution as the groundwater moves through the surficial aquifer and into the lakes, and the increased opportunity for biogeochemical degradation (including photolysis), adsorption, and dilution of pesticides within the lakes. The Ridge lake concentrations also were high relative to national surface-water pesticide concentrations reported by the USGS National Water-Quality Assessment (NAWQA) Program (Choquette and Kroening, 2009), consistent with the groundwater national comparison.…”

“…The frequency of detection of specific pesticides in groundwater samples as a proportion of LWRM Network wells, and sampled lakes (Choquette and Kroening, 2009) on the Ridge, generally was greater than the areal extent of their estimated usage in orange orchards statewide (figs. 3 and 4).…”

“…8). Several of the triazine degradates are the products of multiple parent pesticides (Scribner and others, 1999), but simazine likely is the primary source of HS, DDA, DIA, and DIHA in groundwater underlying the Lake Wales Ridge citrus areas based on several factors (Choquette and Kroening, 2009), and simazine is the only triazine pesticide applied in Florida's citrus croplands.…”

Sampling history and 2009--2010 results for pesticides and inorganic constituents monitored by the Lake Wales Ridge Groundwater Network, central Florida

“…Compared to non-citrus areas, samples from the wells in citrus land-use yielded greater (p<0.05) concentrations of: aluminum, chloride, fluoride, magnesium, manganese, nitrate plus nitrite, total nitrogen (N), potassium, strontium, sulfate, and specific conductance. Elevated concentrations of calcium, magnesium, chloride, sulfate, potassium, and nitrate, and higher specific conductance have been documented in other studies of groundwater and lakes in ridge citrus compared to non-citrus areas (Stauffer, 1991;Sacks and others, 1998;Choquette and Kroening, 2009). These studies noted agrichemicals, including fertilizers, soil amendments, and some pesticide formulations, as well as irrigation water from the Upper Floridan aquifer as potential sources of these chemicals.…”

“…Samples from selected Ridge lakes ( fig. 1) yielded concentrations of some pesticides that were among the highest observed in USGS national pesticide sampling in streams (Choquette and Kroening, 2009). In statewide sampling of about 4,000 Florida drinking-water wells during the 1990s, 89 percent of the 584 wells that yielded nitrate concentrations above the U.S. Environmental Protection Agency (USEPA) drinking-water standard were located in the ridge citrus region of central Florida (Graham and Alva, 1998).…”