THE INFLUENCE OF ARSENIC CHEMICAL FORM AND CONCENTRATION ON SPARTINA PATENS AND SPARTINA-ALTERNIFLORA GROWTH AND TISSUE ARSENIC CONCENTRATION

Arsenic (As) uptake by two perennial coastal marsh grasses growing in hydroponic conditions was studied in relation to the chemical form and concentration of As added to nutrient solution. A 4x3x2 factorial exp eriment was conducted with treatments consisting of four As chemical f orms [arsenite, As(III); arsenate, As(V); monomethyl arsonic acid, MMA A; and dimethyl arsinic acid, DMAA], three As concentrations (0.2, 0.8 , and 2.0 mg As L-1) and two plant species (Spartina patens and Sparti na alterniflora). Arsenic phytoavailability and phytotoxicity were pri marily determined by the As chemical form present in the nutrient solu tion, though As concentration also influenced both As availability and toxicity. Application of As(V) increased root, shoot and total dry ma tter production; this positive plant growth response may be linked wit h P nutrition. Organic arsenicals and As(III) were the most phytotoxic species to both marsh grasses when plant growth was considered. Arsen ic uptake and transport in plant were species-specific. Phytoavailabil ity of As followed the trend DMAA << MMAA congruent to As(V) < As(III) . Root and shoot As concentrations significantly increased with increa sing As application rates to the rooting medium, regardless of the As chemical form. Upon absorption, inorganic arsenicals and MMAA were mai nly accumulated in the root system, while DMAA was readily translocate d to the shoot.