Anthropogenic Sources of Heavy Metals in the Indian Ocean Coast of Kenya

Abstract

Water and surface sediment samples from Rivers Sabaki, Ramisi and Vevesi that flow into the Indian Ocean coast of Kenya were analysed for heavy metals. The sediment concentrations of exchangeable cations (in microg/g) for Co, Cu, Mn, Ni, Pb, Sn and Zn ranged from 0.10 to 506.75 (for Mn at Sabaki), constituting between 2% and 20% of the total metal concentrations obtained by digestion with strong acid. Cu, Mn, Ni, Pb and Zn were more leachable with 0.1 N HCl. The total dissolved metal in water and the total sediment concentrations for Ag, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sn and Zn are given in the text. For dissolved metals, the metal/Mn ratios indicated higher concentrations of Ag in Sabaki River, Cd in Ramisi, Ni in Sabaki and Pb in Ramisi, respectively. In sediments, the metal/Mn ratios showed higher enrichment of Ag in Ramisi, Cd in Sabaki and Vevesi, and Zn in Sabaki, respectively. Enrichment factors showed elevated levels of Cd, Pb and Zn in sediment in River Sabaki and River Vevesi that were due to anthropogenic inputs through Athi River. The total dissolved metal concentration ranges for the three rivers were comparable with those ranges reported in rivers in South Africa but the sediment concentrations were below those of rivers in Europe and Asia where anthropogenic addition of some of the toxic elements such as Cu, Pb and Cd is evidently higher.

Spatial Distribution of Heavy Metals in the Surface Sediments of the Southern Coast of Pacitan, Indonesia

“…Hydrographic data illustrated the actual data range for marine environment with high temperature, seawater range of salinity and slightly alkaline condition [2] and [25] for temperature and pH. However, DO in this study was found to be the highest compared to both studies.…”

“…However, DO in this study was found to be the highest compared to both studies. Water quality parameters could change the bioavailability of metals in the pore waters and the release rate of metals from sediments [7], thus can modify heavy metals chemistry and toxicity on aquatic life [2]. For example, the study [25] found that metals especially Pb experienced flocculation better at lower salinity level and thus reduced its concentration in the environment due to changing of the metal to the particulate phase.…”

“…It is the most concerning heavy metal pollutant in the environment. The input of Pb to the environment comes from many different sources such as from anthropogenic activities, soil and water-borne Pb, and also atmospheric inputs from industrial processes and combustion of fuels and waste materials [2] that make it present in a higher concentration than the other types of heavy metals. Higher concentration of Pb at Pantai Watu Karung and Pantai Soge compared to the concentration at Pantai Teleng Ria and Pantai Pancer clearly showed the effect of lower pH value especially at Pantai Watu Karung (pH = 7.92).…”

“…Heavy metals enter aquatic systems from natural sources (i.e. weathering of rock and soil), as well as from anthropogenic activities [1][2][3]. Aquatic sediments accumulate heavy metals by adsorption or precipitation processes.…”

“…The distributions of heavy metals have been extensively studied and reported elsewhere [1,[11][12][13]. However, studies on the distribution of heavy metals in Indonesia, especially in the southern ocean, are scarce, with limited publication.…”