Distribution characteristics, bioaccumulation and trophic transfer of heavy metals in the food web of grassland ecosystems

Abstract

In this study, according to the classification of biological “classes” and the different trophic levels of the food web, the distribution characteristics, bioaccumulation of heavy metals (HMs) and their trophic transfer in the food web of typical grassland ecosystems were studied and predicted. The results indicated that the accumulation of toxic As was the highest in small mammals and reptiles, Cu was the highest in insects, and the micronutrient Zn in large mammals was higher than that in plants. The metal transfer factor (MTF) by plants at the first trophic level showed that Leymus chinensis had the best ability to absorb HMs from soil. The trophic transfer factor (TTF) of HMs in the second-trophic level insects, birds and some mammals were Zn > As > Cu > Ni > Pb > Co = Cr > Mn > V, in which, biomagnified on Zn, As, and Cu. Organisms at the third trophic level including birds, reptiles and some mammals had the strongest accumulation ability for Pb, V and As, and all were biomagnified. The biomagnification on As and Co of the fourth trophic level Siberian weasel was obviously higher than that of Dione’s rat-snake, which had significant biomagnification effect on As by preying on Steppe toad-headed agama. The study showed that the bioaccumulation levels of HMs in organisms at different trophic levels varied significantly with species, prey, and organ type, but they all showed strong bioaccumulation capacity to toxic As, which indicated that As could produce certain toxic effects on animals in the food web through trophic transfer. In addition, organisms at low-trophic levels were more likely to biomagnify Zn, while organisms at high-trophic levels were more likely to biodilute Pb.