The relationship and impact of pH, ORP, and elemental contents on arsenic remediation by Cyperus papyrus (L.) under submerged soil conditions

Abstract

Arsenic remediation in wetlands is very important to the ecosystem. Phytoremediation efficiency is high and environment-friendly. Cyperus papyrus (L.) can highly selective accumulation arsenic from soil in large quantities. This objective study aimed to investigate variation of pH, redox potential, available phosphorus, extractable iron, exchangeable aluminum, exchangeable calcium and exchangeable magnesium for arsenic remediation in submerged soil by C. papyrus (L.). Experimental design was a 3 × 4 factorial design in a completely randomized experiment (CRD) included two factors. The first factor was the arsenic speciation consisting of arsenite and arsenate. The second factor was the cultivation periods of C. papyrus (L.) including 15, 30, 45 and 60 days. The result indicated that the mean comparison using DMRT of redox potential, total arsenic accumulation of C. papyrus (L.), exchangeable calcium and extractable iron were significantly different among all soil treatment groups (P-value < 0.01). The pH mean and exchangeable magnesium content were significantly different between arsenite and arsenate treated soil with control soil (P-value < 0.01 and 0.05). The amounts of available phosphorus and exchangeable aluminum were not significantly different among all soil types. The variation in group of three soil types during cultivation period 60 days showed that pH, redox potential, available phosphorus, extractable iron, exchangeable aluminum, exchangeable calcium and exchangeable magnesium were statistically significant (P-value < 0.01). The results of comparison among three treatment soils at each cultivating period demonstrated that redox potential, total arsenic accumulation, extractable iron, exchangeable aluminum, exchangeable calcium and exchangeable magnesium were significantly different among all cultivation periods (P-value < 0.01). pH was no significant difference on 15 days and available phosphorus was significant difference on 15 and 30 days (P-value < 0.01 and 0.05). Multiple regression analysis indicated that predictive factors of total arsenic accumulation of C. papyrus (L.) were arsenic speciation, redox potential, pH, and cultivation period. The model explained 85.2% in the regression model. The regression model was -339.542 + 20.249 (arsenic speciation) - 0.322 (Eh) + 52.681 (pH) – 0.987 (cultivating day).