PHOSPHATE FERTILIZER ENHANCES ARSENIC UPTAKE BY APRICOT LINERS GROWN IN LEAD-ARSENATE-ENRICHED SOIL

Phosphate fertilizer additions to soils containing lead arsenate (LA) pesticide residues can increase As solubility. Apricot (Prunus armenia ca L.) rootstock liners were grown in nondraining pots containing Burc h loam soil that received a factorial treatment combination: 1) LA enr ichment [no added LA (-LA), and LA added at 138 mg Pb/kg and 50 mg As/ kg (+LA)]; 2) fertilizer type [monoammonium phosphate (MAP) and its su lfur analog ammonium hydrogen sulfate (AHS)]; and 3) fertilizer anion rate (0-26.1 mol/m3 soil). Measured response variables were soil salin ity and pH, plant biomass, and plant As and Pb concentrations. Both MA P and AHS increased soil electrical conductivity (EC) and decreased so il pH, with AHS usually being more salinizing and acidifying than MAP was at equivalent rates. Adding LA reduced shoot and root mass and inc reased As and Pb concentration in shoots and roots. Shoot and root mas s were inversely related to soil EC in the -LA soil but not in the +LA soil. Adding MAP increased shoot and root As concentration in the +LA soil, but adding AHS had no effect. Fertilizer type and rate did not influence shoot As concentration or root Pb concentration in the -LA s oil or shoot Pb concentration in either the +LA or -LA soil. Adding AH S to the +LA soil increased root Pb concentration. These results are c onsistent with a P-enhanced solid-phase As release mechanism, which co nsequently increases plant uptake of soil As. Phosphate amendment had no effect on soil Pb phytoavailability.