Browsing by Author "De Wael, Karolien"

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    Spatial Monitoring of Organohalogen Compounds in Surface Water and Sediments of a Rural-Urban River Basin in Tanzania
    (Elsevier, 2013-02) Hellar-Kihampa, Harieth; De Wael, Karolien; Lugwisha, Esther H. J.; Malarvannan, Govindan; Covaci, Adrian; Van Grieken, René
    The presence of persistent organic pollutants in Tanzanian environment is not well monitored despite the existing pollution potential from a number of sources. In this study, we investigated for the first time, the concentration profiles of different organohalogen compounds such as organochlorine pesticide residues (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in environmental samples (water and sediments) from the Pangani river basin (PRB). The PRB is one of the largest drainage basins in Tanzania, with its watershed exposed to multiple input sources of trace organic contaminants. Surface water and sediments were sampled from 12 representative stations of diverse characteristics and land-use practices, in three distinct seasons, and extracted by liquid-liquid and Soxhlet extraction methods, respectively. Water samples were analyzed by GC-ECD for OCPs only, while sediment samples were analyzed for OCPs, PCBs and PBDEs by GC/MS. Seven compounds, dominated by HCH isomers (510-4460pg/L) and DDT analogs (160-1460pg/L),were detected in the water samples. These concentrations are far below the WHO guidelines for drinking water quality. A total of 42 compounds (8 OCPs, 28 PCB congeners and 6 PBDE congeners) were detected in the sediment samples. Their respective total concentration ranges were 245-10,230; 357-11,000 and 38-2175pg/g dry weight. The spatial distribution patterns and Hierarchical Cluster Analysis reflected the impact of historical agricultural usage in sugarcane plantations (OCPs), and urbanization (PCBs and PBDEs). Risk assessment using sediment quality guidelines indicated no ecotoxicological risks. The results we have found provide preliminary data on levels of the organic contaminants in Pangani river basin as a new insight on the environmental quality of the area.
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    Water Quality Assessment in the Pangani River Basin, Tanzania: Natural and Anthropogenic Influences on the Concentrations of Nutrients and Inorganic Ions
    (Taylor and Francis, 2013) Hellar-Kihampa, Harieth; De Wael, Karolien; Lugwisha, Esther H. J.; Van Grieken, René
    The ongoing rapid expansions of human activities and population dynamics have a potential impact on the environmental quality of the Pangani River basin, one of the largest water resources in Tanzania, including possible loadings of different kinds of micro-contaminants. However, the specific extent of the impacts is not well investigated. In this work, we assessed the environmental quality of the basin, based on the seasonal characterization of physicochemical water and sediment parameters, dissolved inorganic ions and nutrient loads. The contributions of geochemical processes and land-use practices were evaluated by multivariate correlations and principal component analysis (PCA). Hierarchical cluster analysis was used to classify similar water quality stations and identify the most and least enriched ones. Surface waters were slightly alkaline, characterized by low total dissolved solids (48–652 mg/L). Extremely low oxygen concentration (2.0 mg/L) was also a cause of concern at one station. The Na+ and HCO− 3 ions provided the dominant cation and anion, respectively. The PCA identified the weathering of carbonate- and Na+-bearing rocks, gypsum dissolution and atmospheric deposition of sea salt as the major factors controlling the ionic composition, contributing more than 60% of the spatial variance. The concentration profiles of the chemical species showed a generally low level of anthropogenic inputs, except at a few locations where nitrate and nitrite were significantly enriched above the limits of safe exposure, with patterns indicating influences of farming and livestock-keeping. A seasonal difference was observed, with lower ion concentrations during the rainy season, likely due to the dilution effect of increased water discharge. This study provides new insights into the environmental quality of the basin and indicates the need for continuous monitoring and assessment of the chemical species in the area.