Accumulation and bioaccessibility of trace elements in wetland sediments

Abstract

Accumulation of trace metals in sediment can cause severe ecological impacts. In this study, determination of elemental concentrations in water and sediment was done. Shadegan wetland is one of the most important wetlands in southwest of Iran and is among the Ramsar-listed wetlands.
Wastewaters from industries, urban activities and agricultural run off are released into this unique wetland in the region. In the present  investigation, 12 sampling stations were selected for water and sediment collection in Shadegan wetland during winter, 2009. Physico-chemical parameters such as pH, electrical conductivity (EC), turbidity and salinity of water and pH, EC, total organic materials (TOM), grain size fraction and elements (Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, V and Zn) in sediments were measured. Also, macrobenthos communities were identified in sediments due to their important role in ecosystem health. Subsequently, lithogenous and anthropogenic portions of trace metals in sediment, trace elements bioaccessibility, along with Igeo and IPOLL indices were measured. According to obtained results, trace elements including Cu (39.5%), Pb (26%), Cr (24.1%), Cd (16.4%) and Zn (13.6%) had highest anthropogenic portion in study area. The two pollution indices used in the present investigation (Igeo and IPOLL) are indicative of different pollution intensity in Shadegan aquatic environment. The low pollution intensity values computed by Igeo might be acceptable for metals that have low anthropogenic values (less than 15% of their total concentrations). But higher anthropogenic values (16 to almost 40% of total concentration) for other studied metals show that an IPOLL pollution
intensity formula is more reliable. Moreover, bioaccessibility concentrations amount for Ni, V, Pb and Co had strong and positive meaningful  relationship with Cu, Cr and Cd.

Key words: Heavy metals, accumulation, aquatic environment, IPOLL index, Shadegan wetland.