Heavy metal pollution in surface water of four lakes (Naivasha, Elementaita, Nakuru, and Bogoria) of the Great Rift Valley in Kenya, East Africa was investigated in this study. Eight heavy metals including chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), lead (Pb), cadmium (Cd), and mercury (Hg) were determined using inductively coupled plasma-mass spectrometer (ICP-MS). Among the tested heavy metals, Cd and Hg were detected in all surface water samples. The concentrations of Cr, Cd, Ni, and Pb were relatively lower than those of other metals in the four lakes. Results of Kohonen self-organizing map indicated that all the sampling sites in four lakes of the Great Rift Valley in Kenya could be classified into three different groups based on the heavy metal pollution. Lake Naivasha and Nakuru had characteristics of low concentrations of Cr, Ni, Cu, As, and Hg. Lake Bogoria was characterized by high levels of Ni, Cu, Cd, and Hg, and low levels of Pb, Cr, Zn, and As. Lake Elementaita showed characteristics of high concentrations of As and Hg and low concentrations of Pb, Ni, Cu, and Cd. Source identification using principal component analysis (PCA) indicated that anthropogenic factor played an increasingly important role in the heavy metal pollution of four lakes of the Great Rift Valley in Kenya, East Africa. Analysis of non-carcinogenic health risks of heavy metals indicated Hg and As in Lake Elementaita and Hg in Lake Bogoria may pose adverse health effects to local residents via ingestion route.Abbreviations: HQ, hazard quotient; ICP-MS, inductively coupled plasma-mass spectrometry; PC, principle component; PCA, principal component analysis; SOM, nself-organizing map.(1 of 8) 1600825

Surface water quality closely correlating with human health suffered increasing organochlorine pesticide (OCP) pollution due to the intensive anthropogenic activities in megacities. In the present study, 112 water samples collected from 14 lakes and 11 drinking water source sites in Wuhan were detected for the residues of OCPs in November 2013 and July 2014, respectively. The ΣOCPs ranged from 5.61 to 13.62 ng L in summer with the maximum value in Yezhi Lake and 3.18 to 7.73 ng L in winter with the highest concentration in Yandong Lake. Except dichlorodiphenyltrichloroethanes (DDTs), OCP concentrations in summer were significantly higher than those in winter mostly due to the non-point source pollution including land runoff in summer. Source apportionment of hexachlorocyclohexanes (HCHs) and DDTs revealed the historical use of technical HCH and lindane and the new input of DDT, respectively. The spatial distribution of OCPs was not uniform in the surface water of Wuhan because of the significant influence of land development and fishery. The risk assessments showed the heptachlor, and heptachlor epoxide in most sampling sites exceeded the threshold set by the European Union, indicating the possible adverse effects for aquatic lives. Negligible non-carcinogenic risks for drinking and bathing as well as carcinogenic risks for bathing were found in the surface water. However, the total carcinogenic risks of all OCPs (∑Rs) caused by drinking in summer were higher than the safe level of 10 in all sampling sites. It was implied that the surface water in Wuhan was not safe for directly drinking without effective purification.