Characteristics and Assessment of Trace Elements (Hg, As, Sb, Se, and Bi) in Mire Surface Water from the Changbai Mountains, Northeastern China

Knowledge about trace elements such as mercury (Hg), arsenic (As), antimony (Sb), selenium (Se), and bismuth (Bi) in mire surface water is limited. We studied 105 surface water samples collected from 50 mires in the Changbai Mountains (CBM), northeastern China, investigated the characteristics of these five elements, and assessed the quality of the mire surface water. Hg and Sb in all investigated mires exceeded the guideline values (level V) for surface water set by the State Environmental Protection Administration of China by 92% and 2%, respectively. Inputs of Hg and Sb into surface water were predominantly derived from atmospheric wet deposition and following surface runoff at a regional scale. Concentrations of Sb were influenced by the acidity of mire water and were positively linked with As. Concentrations of As, Se, and Bi were within their allowable ranges (level I), and were not related to any investigated factors at a regional scale. At a local scale, As was influenced by redox conditions; Se was predominantly input from surface runoff; and concentrations of Bi decreased along with strong water table fluctuations and surface runoff. The water quality index (WQI) and the metal index (MI) indicated that 56% of mire surface water was poor for drinking, and 40% was moderately affected for agriculture and general landscape purposes. Early detection of potential risks from these trace elements to organisms is important, and attention should be predominantly paid to Hg and Sb in surface water of mires connected to principal local rivers and streams in these regions.