بيومونيتورينگ و ارزيابي آلودگي جيوه در تالاب بين المللي انزلي با استفاده از گياهان آب زي

Biomonitoring and assessment of mercury pollution in Anzali international wetland using aquatic plants

Heavy metals cause environmental problems in water ecosystems. These elements enter the environment as a result of industrial and agricultural activities as well as urban wastewater. Then, they accumulate in the bodies of aquatic organisms through the food chain. As part of the food chain and due to their capability of absorbing heavy metals, aquatic plants can show the relative increase of these elements in water or in the sediment of ecosystems. In this research, to determine the extent of mercury accumulation in some aquatic plants and the role of aquatic plants in absorbing mercury, to identify the capacity of the different plant organs for absorbing mercury, and to determine a suitable bioindicator for mercury pollution among the aquatic plants of Anzali international wetland in Southern Caspian Sea, plants were sampled from the east and west of the wetland and the contiguous sediment and water in the summer of 2005. Three species (Ceratophyllum demersum, Typha latifolia, Phragmites australis) were collected. Before mercury analysis, the plants were divided into various morphological tissues. The mercury content of the plants was analyzed using Leco AMA 254 Mercury Analyzer after they were dried and ground. The results show that in general, plants exhibited higher metal concentrations than the contiguous sediment and water. It indicates the role of aquatic plants in transferring mercury in the food chain. The comparison between the morphological tissues of the sampled plants revealed that roots consistently presented higher metal concentrations than either the stems or the leaves. The submerged species Ceratophyllum demersum accumulated the highest levels of mercury. A significant correlation was found between these plants and the pollution of the studied region. Therefore, these plants can be used as biomonitors for mercury pollution in Anzali wetland.