In Hawaii, past use of arsenical pesticides has left elevated levels of arsenic (As) in some soils. Sorption isotherms of an Andosol and an Acrisol showed that the former required 1100 mg/kg, and the latter 300 mg/kg of added As to maintain 0.20 mg As/L in solution, the maximum allowable As level in streams/rivers in Hawaii. Greenhouse experiments were conducted on an Andosol (315 mg/kg total As), which was amended with 0, 5 g/kg compost, 5 g Fe/kg as amorphous Fe(OH)<sub>3</sub>, or 250 mg P/kg as Ca(H<sub>2</sub>PO<sub>4</sub>)<sub>2</sub>, and on a low-As (15 mg/kg) Acrisol, which was spiked with 0, 150 or 300 mg As/kg as Na<sub>2</sub>HAsO<sub>4</sub>.7 H<sub>2</sub>O. Brake fern (Pteris vittata L.) was used as the test plant. Arsenic concentration in the fern fronds averaged 355 mg/kg in the Andosol, and 2610 and 1270 mg/kg (from consecutive plantings, 2 and 12 months after As addition, respectively) in the Acrisol spiked with 300 mg/kg of As. Chemical reactions, as suggested by sequential extractions, likely controlled the availability and uptake of soil As. Mehlich-3 extraction could be used to identify As-contaminated soils and potential phytoremediation as it correlated well with bioaccessible As and with As in fern fronds.
Arsenic reactions and brake fern (Pteris vittata L.) uptake in tropical soils
