Fitoakumulasi Logam Berat Pb dan Cr pada Rhizophora mucronata di Sekitar Kawasan Bekas Tambang Bauksit, Pulau Bintan

Abstract

Bintan Island has a high potential for bauxite mining. Many ex-mining areas have not been reclaimed properly, resulting in erosion and accumulation of heavy metals Pb and Cr which are high in the sediment (red-mud) and deposited in the roots of mangrove forests on the coast of Bintan. Rhizophora mucronata is one of the species that dominates the Bintan mangrove forest. The purpose of this study was to determine the phytoaccumulation of Pb and Cr metals in R. mucronata in the former bauxite mining area ofBintan Island. This research was conducted by survey, digested and analysed using Atomic Absorption Spectrophotometer (AAS). The concentrationof Pb and Cr in the sediment, as well as the roots, stems and leaves of R. mucronata were used for the analysis of phytoaccumulation types. The results of the Pb concentration test were higher than Cr. Based on the sampling location, the concentration of Pb metal accumulation in the sediment is Tembeling <Sei Carang <Wacopek <Senggarang, while Cr metal is Tembeling <Wacopek <Sei Carang <Senggarang. The highest metals accumulation in R. mucronata was found in the roots (Pb = 3,3482 ppm, Cr = 0,7664 ppm), while the leaves (Pb = 1,1076 ppm, Cr = 0,0413 ppm) had the lowest concentration. Based on the type of accumulation, R. mucronata absorbs Pb metal with a rhizofiltration mechanism (TF <1), which means that the roots of R. mucronata effectively translocate Pb as a pollutant to its body from the soil. In addition, the bio-concentration factor (BCF) concentration of R. mucronata <1 indicates the role of R. mucronata as a plant that accumulates very little Pb (low accumulator/non-hyperaccumulator). This adaptation mechanism is important information in the rehabilitation of mangrove areas using R. mucronata, because it can still live and grow in an environment contaminated with Pb metal by absorbing a little Pb from the soil and translocating it effectively in its organs.

Sustainability of mangrove forest management in the former bauxite mining area on Bintan Island

“…On the other hand, it was reported that the sediment fraction in Carang River, Tanjungpinang City is dominated by sand (74.65-97.7%), while the Tembeling Tanjung and Wacopek in Bintan Regency are dominated by gravelly sand to slightly gravelly sand. 14 And also the survey results and sediment analysis, 13 the sediment fraction is dominated by sand and silt. This type of fraction is still classified as suitable for mangrove life, as evidenced by the results of observations in the field of mangrove life conditions that mangrove density is still found which is classified as rare to very dense.…”

“…The reported values obtained from the analysis of metal contents in the area indicated non-compliance with the environmental quality standard. 12 The results from the previous study 13 showed that the environmental conditions around the former bauxite mining area on Bintan Island are not polluted but have been contaminated with heavy metals from mining activities. The conclusion was derived based on the Pollutant Load Index (PLI) value which was <1 for Pb and Cr, and the Geo-Accumulation Index (I_geo) which was 0<I_geo<1 for Pb and Cr.…”

“…The survey 13 found 11 mangrove species at the site, namely Avicennia alba, A. marina, Rhizophora apiculata, R. mucronata, Ceriops tagal, Bruguiera gymnorhiza, B. cylindrical, Sonneratia alba, Xylocarpus granatum, X. mollucensis, and Lumnitzera littorea. The most dominant species were R. mucronata, R. apiculata, and A. marina with mangrove density values classified as moderate (1300 trees/Ha) to damaged (678 trees/Ha).…”

“…Based on the results from a study, 13 the accumulation of heavy metal, Pb, in the sediment was found between 0.06 and 0.24 ppm. Besides, the concentration of Pb found in the leaves of R. mucronata was between 0.04 and 0.37 ppm, 0.05-0.71 ppm in the stems, and 0.08-0.87 ppm in the roots.…”

“…The environmental conditions around the former bauxite mining area are classified as uncontaminated but already contaminated by heavy metal content. 13 This assessment is obtained from the calculation of the geoaccumulation index as the level of water pollution and environmental pollution load. However, based on the health level of the mangroves, it is classified as experiencing mild to moderate damage, with the sources of damage being roots (21%) as well as roots and lower stems (17%).…”