Integrated multiphase ecological risk assessment of heavy metals for migratory water birds in wetland ecosystem: A case study of Dongzhangwu Wetland, China

Abstract

Wetland is an important feature of the landscape that provides beneficial services. However, with the ever-increasing heavy metal load, the quality of wetlands is deteriorating. Dongzhangwu Wetland in Hebei, China, was taken as our study site. It provides breeding and foraging grounds to migratory water birds such as Little Egret (Egretta garzetta), Great Egret (Ardea alba), and Grey Heron (Ardea cinerea). The current study aimed to quantify heavy metals exposure hazard and risk to the water migratory birds by employing a non-destructive approach. Oral intake was considered the main exposure route to calculate total exposure via multiple phases. The concentrations of Cr, Zn, Cu, Pb, As, Ni, Mn, and Cd were investigated in water, soil and food compartments of three different habitat components (Longhe River, Natural Pond and Fish Pond). The results showed: (1) The trend of potential daily dose (PDD) was Mn > Zn > Cr > Pb > Ni > Cu > As > Cd while for hazard quotient (HQ) was Cr > Pb > Cu > Zn > As > Ni > Mn > Cd, making Cr, Pb, Cu, Zn, and As the priority pollutants in all habitats, with Natural Pond eliciting the highest exposure. (2) The cumulative heavy metal exposure, explained by the integrated nemerow risk index, characterized all three habitats for all the birds in high exposure risk category. (3) The exposure frequency index identified that all the birds are frequently exposed to heavy metals from multiple phases in all three habitats. (4) Little Egret is at the highest pedagogy of exposure from single or multiple heavy metal(s) in all three habitats. A rigorous management plan for identified priority pollutants is required to improve wetland functioning and ecological services. Decision-makers could use the developed tissue residue objectives for protecting Egret species in Dongzhangwu Wetland as benchmarks.