Interaction of lime, organic matter and fertilizer on growth and uptake of arsenic and mercury by Zorro fescue (Vulpia myuros L.)

The Sulphur Bank Mercury Mine (SBMM) is an abandoned open pit mine located on the eastern shores of Clear Lake, California. Revegetation efforts have been difficult because the mine-soils at SBMM have low pH, low fertility and elevated As and Hg concentrations. In a greenhouse study, we examined the interactions of lime, N, P and OM additions with respect to plant growth, and As and Hg uptake. Three selected acidic mine-soils from the site containing high (164 mg/kg) (S-H), medium (123 mg/kg) (S-M) and low (31 mg/kg) (S-L) total As content were planted to the Eurasian annual grass, Zorro fescue (Vulpia myuros L.). The Hg concentrations for these soils varied between 1700 and 3000 mg/kg with S-L > S-H congruent to S-M. A factorial design used 3 soils, 2 lime, 2 N, 2 P and 2 OM treatments with treatments replicated three times. Multiple regression analyses indicated a strong relationship between As plant uptake, root length density (RLD) and soluble As. A highly significant linear relationship between Hg uptake and RLD for plants growing on the three soils illustrated the importance of plant root characteristics in influencing Hg uptake. Soluble As decreased in the order S-H > S-M > S-L in positive correlation with P and DOC but in inverse relationship to oxalate extractable Fe. Lime and OM additions correlated negatively with soluble Hg and Hg tissue concentration due to either Hg adsorption to OM or to inorganic surfaces. Addition of lime increased dry matter yield and Hg uptake in all three soils.