Pollutant Exposure for Chinese Wetland Birds: Ecotoxicological Endpoints and Biovectors

Levels
of heavy metals and organic contaminants in main waters
from China were reviewed from literature data to assess the ecological
risks of pollutants for wetland birds and the biotransport of pollutants
mediated by migratory wetland birds. Cr, Cu, and Pb and polycyclic
aromatic hydrocarbons (PAHs) dominated in sediments, with higher concentrations
in rivers and estuaries than in lakes and seas. Plants are the main
dietary sources of less hydrophobic organic pollutants, while sediment
is the primary source of more hydrophobic PAHs in birds. The hazard
index (HI) for birds was mainly contributed by mercury (Hg) and polybrominated
diphenyl ethers (PBDEs) and ranked as piscivore > omnivore >
herbivore.
Pollutant exposure risks to birds depend on the biomagnification potential
of pollutants, food items of birds, and pollution levels in habitats.
Migratory birds are important biovectors of persistent and bioaccumulative
pollutants that may serve as a vital geochemical cycling process in
addition to atmospheric deposition. This study provided a comprehensive
overview of water environment pollution in China and the potential
risks for high trophic level wetland birds in aquatic ecosystems.
The results also identified the pollution hotspots of wetland birds
and habitats, which provide new insights into bird conservation and
biodiversity protection.