The concentrations of Cu, Co, Zn, Ni, V, and Cr in topsoils at six sites located along the lower slopes of Mt. Cameroon were assessed for their potential toxicity to humans and the ecosystem. Soils were collected from horizons down to a depth of 70？cm and analysed for trace element concentration by ICP-MS technique. The Dutch soil quality standards which use %clay/silt and organic matter content to derive target values were used to assess the contamination levels of the soils. The content of these soils was also compared to the United Kingdom ICRCL “soil trigger” values. Zinc and Cu values were persistently below the normal value (A) and occurred in the lower elevation, the region of extreme weathering, while Cr and V values were above the intervention (C) values. The high content of Cr in common fertilisers poses a potential risk in toxicity in the higher elevations experiencing lower weathering rates, where soil Cr levels are elevated. 1. Introduction Many trace elements are essential macro- and micronutrients for humans, plant growth, and the maintenance of healthy ecosystems. Micronutrients like Cu, Mn, Se, and Zn can be toxic at high concentrations in the soil. Trace elements unknown to be essential to plant growth, such as barium (Ba), cadmium (Cd), chromium (Cr), lead (Pb), and nickel (Ni), are toxic at high concentrations or under certain environmental conditions in soils. One of the major factors controlling soil trace element content is the parent rock material. Soils vary across landscapes and rock weathering and other soil-forming processes may result in the addition or removal of these elements from the soil. High background concentrations of trace elements, whether from natural or anthropogenic sources, could result in mobilization and release into surface and subsurface waters and subsequently incorporation into the food chain. Soil factors such as organic matter, type and amount of clay, pH, and cation exchange capacity (CEC) influence the quantity of trace elements available for mobilization and release or sorption in a soil . Regulations to protect humans and the environment from toxicities and deficiencies related to trace elements are primarily based on soil quality reference values which are being developed in many countries. Many countries that have not developed their own formal guidelines follow the “Dutch standard” to support decision-making in assessing and monitoring soil quality. The Dutch are improving their soil quality in light of new scientific work particularly with regard to the impact of listed substances on living
P. R. J. Danneman and J. G. Robberse, “Ecotoxicological risks assessment as a base for development of soil quality criteria,” in Contaminated Soil ’90, F. Arendt, H. Hinsenfelt, and W. J. van den Brink, Eds., pp. 157–164, Kluwer Academic Publisher, Dordrecht, The Netherlands, 1990.
G. W. van Barneveld, “Agroclimatic conditions of West Africa and Cameroon,” in Proceedings of the 3rd International Forum on Soil Taxonomy and Agro-Technology Transfer, H. Ikawa and G. Y. Tsuji, Eds., Benchmark Soils Project Technical Report 10, pp. 121–133, University of Hawaii, 1987.
C. E. Suh, R. S. J. Sparks, J. G. Fitton et al., “The 1999 and 2000 eruptions of Mount Cameroon: eruption behaviour and petrochemistry of lava,” Bulletin of Volcanology, vol. 65, no. 4, pp. 267–281, 2003.
V. E. Manga, C. E. Suh, C. M. Agyingi, and E. M. Shemang, “Mineralogy and geochemistry of soils developed along the slopes of Mt. Cameroon, West Africa,” Journal of African Earth Sciences, vol. 81, pp. 82–93, 2013.
Interdepartmental Committee on the Redevelopment of Contaminated Land, ICRCL 59/83 Guidance on the Assessment and Redevelopment of Contaminated Land, Code EPTSSP187-5RH3, CEDP/EPTS, Romney House, London, UK, 2nd edition, 1987.
H. Sato, S. Aramaki, M. Kusakabe, et al., “Geochemical difference of basalts between polygenetic and monogenetic volcanoes in the central part of the Cameroon volcanic line,” Geochemical Journal, vol. 24, no. 6, pp. 357–370, 1990.
V. B. Che, K. Fontijn, G. G. J. Ernst et al., “Evaluating the degree of weathering in landslide-prone soils in the humid tropics: the case of Limbe, SW Cameroon,” Geoderma, vol. 170, pp. 378–389, 2012.
G.-L. Zhang, J.-H. Pan, C.-M. Huang, and Z.-T. Gong, “Geochemical features of a soil chronosequence developed on basalt in Hainan Island, China,” Revista Mexicana de Ciencias Geológicas, vol. 24, no. 2, pp. 261–269, 2007.
J. D. Hem, C. E. Roberson, and C. J. Lind, “Study and interpretation of the chemical characteristics of natural water,” U.S. Geological Survey Water Supply Paper 2254, US Geological Survey, Alexandria, Va, USA, 1985.
E. J. M. Temminghoff, S. E. A. T. M. van der Zee, and F. A. M. de Haan, “Copper mobility in a copper-contaminated sandy soil as affected by pH and solid and dissolved organic matter,” Environmental Science and Technology, vol. 31, no. 4, pp. 1109–1115, 1997.
L. Knudsen, “Status of micronutrient demand of Danish crops,” in Essential Trace Elements for Plants, Animals and Humans, G. Thorvaldsson and R. S. Jónsdóttir, Eds., NFJ Seminar no. 370, Reykjavík, Iceland, August 2005.
M. Korhonen, M. Rinne, and P. Huhtanen, “Effects of soil characteristics and fertiliser application on grass yield and chemical composition including mineral and trace element content—farm scale studies in Finland 1995–2004,” in Essential Trace Elements for Plants, Animals and Humans, G. Thorvaldsson and R. S. Jónsdóttir, Eds., NFJ Seminar no. 370, Reykjavík, Iceland, August 2005.
F.-Y. Wu, W.-Y. Wu, H.-W. Kuo, C.-S. Liu, R.-Y. Wang, and J.-S. Lai, “Effect of genotoxic exposure to chromium among electroplating workers in Taiwan,” Science of the Total Environment, vol. 279, no. 1–3, pp. 21–28, 2001.
H. D. Poulsen, “Trace elements in animal nutrition,” in Essential Trace Elements for Plants, Animals and Humans, G. Thorvaldsson and R. S. Jónsdóttir, Eds., NFJ Seminar no. 370, Agricultural University of Iceland, Reykjavík, Iceland, 2005.
M. F. Benedetti, A. Dia, J. Riotte et al., “Chemical weathering of basaltic lava flows undergoing extreme climatic conditions: the water geochemistry record,” Chemical Geology, vol. 201, no. 1-2, pp. 1–17, 2003.