8273 - Laserfiche WebLink

Home Browse Search

National Irrigation Water Quality Program Guidelines Biotic Effects I I large-mouth bass (Micropterus salmoides) from Pinfeather Lake had deformed fins, jaws, heads, and eyes; waterborne arsenic concen- trations at the time were 0.54 mg/L. Abiotic Factors Affecting Bioavailability Water Many factors influence arsenic toxicity in water, including water temperature, pH, organic content, phosphate concentration, suspended soils, the presence of other substances and oxidants, and arsenic speciation. A study by McGeachy and Dixon (1990) confirmed that more arsenic is taken up as the water temperature increases. Sediment Higher levels of arsenic in sediment were correlated with levels in macrophytes in a study done by Tanner and Clayton (1990), but other studies (Cain et al. 1992, Smith et al. 1992) reported low bioavailability and little partitioning of arsenic from contaminated sediments. Long and Morgan (1990) and Long et al. (1995) made a comprehensive evaluation of chemical concentrations in sediments that were associated with adverse biological effects. They concluded that arsenic concentrations of 8.2 mg/kg dw or less do not usually produce adverse effects, but concen- trations of 70 mg/kg or higher usually do. Although many of the data evaluated were for estuarine and marine sediments, Hull and Suter (1994) concluded that those screening levels also were appropriate for freshwater sediments until more specific guidelines become available. However, it is also recommended that these concentrations be compared to local background levels when possible. (2) Tables 2, 3, and 4 at the end of this chapter list the reported biotic effects of arsenic in water, sediment, and diet, respectively. I Plants I I I I Arsenic is not an essential element in plants (Kabata-Pendias and Pendias 1992), although small increases in yield have been observed for several species at low levels of soil arsenic (Woolson 1975). Some forms of arsenic, such as sodium arsenate and arsenic trioxide, are extremely toxic to plants. Arsenic uptake seems to be passive (Bodek et al. 1988) from terrestrial soil to plants. The major symptoms of arsenic toxicity in plants are red-brown necrotic spots on old leaves, yellowing or browning of the roots, wilting of new leaves, and depressed tillering (Kabata-Pendias and Pendias 1992). Sensitive species such as spinach (Spinacia oleracea) showed 40-percent reduction in growth when exposed to As (V) at 10 mg/kg in soil (table 3). Low concen- trations of As (V) in water (1-15.2 pg/L) have been reported to inhibit certain aquatic plants, resulting in noticeable changes throughout the ecosystem. Sanders and Cibik (1985) have reported consequen~ changes in the composi- tion and succession of species and in predator- prey relations in chronic studies. I I I I I I I I Amphibians/Reptiles Very few studies have investigated the effects of arsenic on amphibians and reptiles. Khangarot et al. (1985) determined the acute toxicity of As (m) to tadpoles (Rana hexadactyla). Under the conditions of pH 6.1, temperature 15 oC, and total hardness 20 mg/L (calcium carbonate), they found that a concentration of 249 pg As/L I I I I