Trace Element Distribution and Enrichment in the Stream Sediments of the Lake Togo Watersheds (South of Togo)
A. Avumadi1, 2, K. Gnandi2, J.L. Probst1
1. Laboratoire d’Ecologie Fonctionnelle et Environnement (EcoLab); Université de Toulouse; CNRS; UPS; INPT; Avenue de l’Agrobiopole, 31326 Castanet-Tolosan cedex, France.
2. Laboratoire des Sciences de la Terre, Faculté des sciences, Université de Lomé, B.P 1515, Lomé, Togo.
Abstract: To evaluate the level of sediment contamination in watershed of lake Togo (south of Togo), the concentrations of twelve trace elements, TE (As, Sn, Cr, Co, Ni, Cu, Zn, Zr, Cd, Pb, Th, U) are analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) in eighteen stream sediment samples from Zio and Haho rivers draining into the lake Togo and from lake Togo itself. The results obtained allow to characterize each sediment sample by its TE geochemical distribution pattern. Average TE concentration in the finest fractions (< 63 µm) is ranked from the hightest to the lowest content: Cr>Ni>Zn>Cu>Co>Pb> Th> Sn>U>As>Cd. The degree of contamination of these stream sediments is evaluated by calculating sediment quality parameters such as enrichment factors (EF), anthropogenic and naturel contribution. Globally, 70% of TE have an EF lower than 1.5, particularly for As, Sn, Co, Cu, Zn, Pb, Th and U. However, 30% of the samples are more contaminated (1.5<EF<6), particularly for Ni, Cr, Cd from one sampling point to another. Nevertheless, the anthropogenic contribution could represent only 18% of the total content, 82% originating from natural rock weathering processes. A single chemical extraction by EDTA allows to assess the non-residual (labile) fractions for Zio and Haho river sediments. For Co, Cu, Cd and Pb, the EDTA extracted fractions represent respectively 38%, 32%, 25% and 24% of the total concentration. The EF values are subjected to multivariate statistical analysis in order to evaluate the origins of TE in the study area. Most of TE are controlled by clay, oxi-hydroxide minerals and organic matter.
Keywords: Trace metals, stream sediments, enrichment factor, labile fraction, natural and anthropogenic contributions.
Pages: 87 – 114 | Full PDF Paper
Siti Yasmin Y. & Muhamad Afizzul M.
Geoinformation Programme, Forestry and Environment Division, Forest Research Institute of Malaysia (FRIM), 52109 Kepong, Selangor Darul Ehsan, Malaysia.
Abstract: Forest plays an important role as habitat for flora and fauna. However, due to land use conversion activity conducted by human, the forest area are continually decreasing and facing fragmentation. This study is aimed to evaluate the spatial patterns and determine the status of fragmentation among three major forest types in Peninsular Malaysia namely inland forest, mangrove forest and peat swamps forest. The input data required are forest cover was generated from Landsat-8 imagery acquired throughout year 2016. The input data then was evaluated using an open source spatial statistical package software called FRAGSTATS. Ten landscape metrics consist of percentage land cover, number of patches, patch density, largest patch index, mean patch size, edge density, mean shape index, mean core index, mean nearest-neighbor distance and interspersion and Juxtaposition index were generated using FRAGSTATS. From the result obtained, we found that inland forest encounter the least fragmentation, followed by peat swamps forest and mangroves forest.
Keywords: spatial patterns, forest, FRAGSTATS, fragmentation.
Pages: 115 – 124 | Full PDF Paper