Potential macrophytes as bioindicator of heavy metals in runoff from areas with acid sulfate soil

Abstract

The oxidation of pyrite produces high concentrations of ferrous ions and sulfuric acid, which in turn attacks clay minerals and produces high concentrations of monomeric Aluminum (Al) and other acid-soluble metals. Subsequent leaching of these toxic products into adjacent water bodies is rapidly increasing the stress on ecosystems. High concentrations of metals are usually associated with acidic drainage. Most metals are more water-soluble in acidic conditions and therefore metal accumulation in plants depends on the plant species, types of soil, environment and agricultural practice. The aim of the study is to monitor heavy metal runoff from acid sulfate fresh water body through plant-based technology. Therefore, objectives have been set up as follow: 1) to study physico-chemical properties of acid sulfate soil fresh water bodies, 2) to assess amounts of five (5) toxic metals (Al, As, Fe, Mn, Ni) in acidic fresh water bodies in Selangor and 3) to identify potential macrophytes as phytoindicator in acid sulfate soil fresh water bodies. The study has been conducted at fourteen (14) different sites in Selangor in areas of acid sulfate soil. Methodology of water sampling, nutrient analysis using HACH Salicylate method and ICP-MS for testing heavy metal was used. Comparing all the sampled plant species from research areas, it can be concluded that the pH observed were high and less acidic (5 – 6). The DO is low (3.5 -4mg/L) with high level of Ammoniacal nitrogen that leads to excessive nutrient and water pollutants. The growth of the macrophytes was also affected by other environmental parameters, such as temperature, pH and DO resulting with I.aquatica > N.stellata > P.stratiotes > L.palustris > U.aurea as potential biomonitoring agents for unhealthy aquatic ecosystem environment. The concentration of Ammoniacal nitrogen (NH3-N) was found substantially higher for N.stellata, L.palustris and U.aurea,which are classified under class III according to NWQS. P.stratiotes generates a great potential to be a phytoindicator for the run off of Al, Fe and Mn from acid sulfate soil. The potential macrophytes for biomonitoring for heavy metal run-off (Al, Fe and Mn) were P.stratiotes. As for the concentration of Ni, the significant phytoindicators were N.stellata and P.stratiotes; and for As the indicator was L.palustris. Among these six species analyzed, the most potential macrophytes to indicate unhealthy environment of acid sulfate soil are P.stratiotes and N.stellata, as they are present in low DO level, high pH, high concentration of NH3-N and tolerant of Al, Fe, Mn, and Ni. Keywords: heavy metal, phytoindicator, bioindicator, acid sulfate soil.