Arsenic Concentrations in Florida Surface Soils: Influence of Soil Type and Properties

through the food chain via uptake from contaminated soils may adversely affect human health (Arnt et al., Background As concentrations in soils are important for defining 1997). While the regulations governing As contaminawhether a soil is polluted. Arsenic concentrations in 441 taxonomically tion in waters are well defined, the regulatory cleanup and geographically representative surface soils were determined using EPA Method 3052 (HCl-HNO3-HF digestion). Cumulative distribugoals for remediation of contaminated soils are still untion plots indicate that As concentrations follow a log-normal distribuder development and may vary greatly among countries, tion and depend on soil type. Sample geometric mean(GM) (the states, and land uses. For example, the regulatory limits exponential mean of the log-transformed distribution) As concentraset by the Ministry of Environment of Canada for As tions (mg kg 1 ) generally follow the soil taxonomic order of Histosols contamination in agricultural, industrial, and residential (2.35) Inceptisols (0.98), Mollisols (0.72) Ultisols (0.51) Alfisols soils are 25, 50, and 25 mg kg 1, respectively (Arnt et (0.39), and Entisols (0.36) Spodosols (0.18). The highest As concenal., 1997). In contrast, those for the United Kingdom trations were found in soils that occur exclusively or prevalently in are set at 10 mg kg 1 for domestic gardens and 40 mg wetlands, such as Hemists (3.16–9.44), Saprists (0.15–11.7), Aquents kg 1 for parks, playing fields, and open spaces (O’Neill, (0.10–50.6), Aquolls (0.03–3.34), and Aquepts (0.03–38.2). Both linear 1990). Variations of this type are also found in the U.S. and multiple regressions indicate soil properties (clay, pH, cationregulatory guidelines (Association for Environmental exchange capacity [CEC], organic C, and total Al), especially total Health of Soils, 1998). The New Jersey Department Fe and P, are important factors affecting natural background concenof Environmental Protection (NJDEP) has set a state trations of As in Florida soils. Arsenic release from bedrock (limecleanup criterion of 20 mg kg 1 for both residential and stone) and As bioaccumulation by aquatic organisms are possible nonresidential soils based on background soil As levels explanations for relatively high As in those wetland soils. The use of a single regulatory value criterion for As contamination in soil cannot (Barringer et al., 1998; NJDEP, 1998). The current soil provide an adequate assessment given the natural variation in soil cleanup goals set by the Florida Department of EnvironAs. Baseline soil-As concentration, which was defined as 95% of the mental Protection (FDEP) for As in residential and expected range of background As concentrations in different soil industrial soils are 0.80 and 3.7 mg kg 1, respectively categories, is necessary for properly assessing potential As contami(Tonner-Navarro et al., 1998), based on direct exposure. nation. Variations in these guidelines indicate a need for standardizing how cleanup criteria are established. In cases where the risk-based criteria are lower than the method P concerns over As pollution in both soils detection limit (NJDEP, 1998) or are below the siteand waters have substantially increased in recent specific background level, it is reasonable to use the years (Association for the Environmental Health of latter two as the cleanup criteria (Association for EnviSoils, 1998; Research Triangle Institute, 1998). Long ronmental Health of Soils, 1998). Therefore, it is imporsuspected to be responsible for bladder, kidney, liver, tant to obtain accurate As background concentrations lung, and skin cancers, inorganic As has been listed by for different soils to prevent unrealistically low mandatory guideline levels (Kabata-Pendias and Pendias, the USEPA as a Class A human carcinogen (Research 1992; Davies, 1992). To obtain the accuracy required Triangle Institute, 1998). The current maximum allowfor regulation purpose, As background levels in soils able levels of As for oral intake and drinking water should be based on a sufficiently large database. These are set at 0.3 g kg 1 d 1 and 50 g L 1, respectively data can then be used as a reference to compare with (USEPA, 1998). However, the World Health Organizasite-specific As concentrations (Breckenridge and Crocktion has recently begun to press for stricter consumption ett, 1995) in determining whether or not a particular standards and has recommended lowering the As drinksoil type is contaminated. ing water standard to 10 g L 1 (Research Triangle The main source of As in soils is the parent materials Institute, 1998). The USEPA is currently under pressure from which the soil is derived. Atmospheric deposition from the National Research Council to lower its current contributes significantly to the geochemical cycle of As drinking water standard of 50 g As L 1 to 20 g As (Smith et al., 1998). Also, bioconcentration of As by L 1 to adequately protect public health (Christen, 1999). lowland plants and aquatic organisms, such as algae, In addition to concerns over As contamination in seagrass (Halophila Thouars), and lower invertebrates water sources, it is also known that dietary intake of As (Otte et al., 1990; Cullen and Reimer, 1989; Strom et al., 1992) contributes to elevate As concentrations in M. Chen*, Institute of Geography and Natural Resources, Chinese lowland soils. Doyle and Otte (1997) found that salt Academy of Sciences, Beijing 100101, China. L.Q. Ma, and W.G. marshes could act as effective sinks for As and other Harris, Soil and Water Science Dep., University of Florida, Gainesville, FL 32611-0290. Approved for publication as Florida Agricultural Experiment Station Journal Series No. R-07010. Received 15 Sept. Abbreviations: CEC, cation-exchange capacity; ENP, Everglades Na2000. *Corresponding author ([email protected]) and current tional Park; FDEP, Florida Department of Environmental Protection; address: Everglades Education and Research Center, University of GM, geometric mean; GSD, geometric standard deviation; NJDEP, Florida, 3200 E. Palm Beach Road, Belle Glade, FL 33430. New Jersey Department of Environmental Protection; UBC, upper baseline concentration. Published in Soil Sci. Soc. Am. J. 66:632–640 (2002).