Comparison of heavy metal concentrations in groundwater in a mangrove wetland and a bald beach in Dongzhaigang National Nature Reserve (DNNR), China

A mangrove transect (M–M′) and a bald beach transect (B–B′) were selected in Dongzhaigang National Nature Reserve, China for conducting a comparative study about groundwater chemical characteristics. It was found that the average concentration of Cl − in groundwater sampled from M–M′ was much lower than that of B–B′. However, concentrations of heavy metals Ba, Mn, Pb, Sb in groundwater of M–M′ were significantly higher than those of B–B′. The average concentrations of Ba, Mn, Pb, Sb were 0.13, 0.83, 0.25 and 0.32 mg/L in M–M′, respectively, and 0.09, 0.27, 0.19 and 0.21 mg/L in B–B′, respectively. Both transects were affected by the human activities such as aquacultures. The high concentration of Sb in the groundwater of transect M–M′ may be mainly due to high concentration of Sb in the Yanfeng River. The higher concentrations of Ba, Mn, Pb in groundwater in M–M′ might be attributed to the accumulating and enriching effects of the mangrove systems on heavy metals. The mechanism of accumulating and enriching need to be further investigated in the future.