Selenium concentrations in waters tributary to and in the vicinity of the Kesterson National Wildlife Refuge, Fresno and Merced counties, California

Abstract

Analyses were made for selenium in waters and other materials of the Kesterson National Wildlife Refuge. Analyses were also made of source agricultural drainage waters from the San Luis Drain discharged into the refuge, and surrounding irrigation supply and return waters. concentrations range from 140 to 1,400 micrograms per liter (ug/L) in irrigation drain waters supplied to the San Luis Drain. The selenium supplied to the Kesterson National Wildlife Refuge is to a small extent precipitated in sodium sulfate (thenardite) but a higher concentration was found in an algal mat. Most other waters of the area contain less than detectable (<2 ug/L) concentrations of selenium. -2 Oxidation of organic matter and reduction of selenate (SeO4 ) to selenite -2 (SeO3 ) were found to be necessary for a quantitative analysis of total selenium. INTRODUCTION The United States Fish and Wildlife Service (U.S.F. &W.S.) reported to the U.S. Geological Survey (U.S.G.S.) that unusually high rates of mutation occurred in hatchlings of wild waterfowl (up to 40% for coots) in the Kesterson National Wildlife Refuge (Felix Smith, oral commun., July, 7 1983). The U.S.F. & W.S. further stated that analyses of hatchling tissue showed high selenium (Se) concentrations. Information on Se concentrations in fish from the Kesterson Reservoir and San Luis Drain was released later in a report by the U.S. Bureau of Reclamation (February, 1984). Concentrations of Se were as much as 100 times higher than those of fish from the Volta Wildlife Refuge comparison test area. A map of California (No. 214-308-5165), Central Valley Project, San Luis Unit, West San joaquin Division by the Bureau of Reclamation in September, 1975 gives a description of the San Luis Drain Federal Facility: (San Luis Drain) will be a concrete-lined canal extending 188 miles from the vicinity of Kettleman City to the lower San Joaquin-Sacramento Delta. The Drain will convey and dispose of subsurface irrigation return flows from the San Luis Service area. A feature of the Drain is the Kesterson Reservoir area where water is stored and regulated. The reservoir is designated as a National Wildlife Refuge for the conservation and management of wildlife and recreation. Predictions about the mobility of Se are given by Lakin in a chapter in Selenium in Agriculture (1961). He stated that in regions of low rainfall -2 and alkaline soils, part of the Se would occur as selenate (SeO^ ). -2 As SeO4 , it would be available to vegetation and readily transported in ground water. In contrast, are regions of acid environment where Se would tend to occur in ferric hydroxide precipitates as basic ferric selenite This form is more stationary and presumably of low availability to plants. The areas supplying water to the San Luis Drain have low rainfall, approximately 10 inches annually, (National Oceanic and Atmospheric Administration, 1981). Because of the potential hazards of mutagens in water, the U.S.G.S. initiated a study of the waters in and tributary to the Kesterson National Wildlife Refuge. Other water supplies in the area were studied to provide a basis for comparison with the Kesterson water supply. The study included but was not limited to analyses for Se. The chemistry of Se is complex, especially in natural systems where a range of oxidation states may be expected and a variety of biochemical effects may be anticipated. Further complications were expected in analytical procedures because large variations in concentrations of solutes lead to complex matrix effects. A broad analytical experience with wide ranges of inorganic solutes in water facilitated this study (Presser and Barnes, 1974). FIELD AND HYDROLOGIC RELATIONS Maps of the study area are shown in Figures 1 and 2. Approximately 80 miles of the San Luis Drain are now completed, from Bur re 1, 20 miles southwest of Fresno in the south to Kesterson in the north. Figure 1 shows sample locations in the vicinity of the Kesterson National Wildlife Refuge. Figure 2 shows sample locations of inflows into the San Luis Drain. The two areas are not contiguous. Figure 3 is a map of Kesterson National Wildlife Refuge distributed by the State of California, Department of Fish and Game. The evaporation ponds are numbered 1 through 12. The San Luis Drain borders the ponds on the east. The only visible entries from the San Luis Drain into the Kesterson ponds are into ponds 2 and 12. The water evaporates as it flows from pond to pond in a northerly direction from pond 2 to pond 11 where flow