Water Research 186 (2020) 116350 Contents lists available at ScienceDirect Water Research journal homepage: www.elsevier.com/locate/watres Occurrence, distribution, spatio-temporal variability and source identification of n-alkanes and polycyclic aromatic hydrocarbons in water and sediment from Loskop dam, South Africa Mathapelo Pearl Seopela a,b,∗ , Robert Ian McCrindle a , Sandra Combrinck c , Wilma Augustyn a a Department of Chemistry, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa b Department of Chemical Sciences, University of Johannesburg, PO Box 524 Auckland Park, 2006, South Africa c Department of Pharmaceutical Sciences, Tshwane University of Technology, Private Bag X680, Pretoria 0001, South Africa a r t i c l e i n f o Article history: Received 6 May 2020 Revised 29 July 2020 Accepted 26 August 2020 Available online 26 August 2020 Keywords: Source apportionment n-Alkanes PAHs Diagnostic ratios Chemometric analysis a b s t r a c t In this study, the spatial and temporal variations in the levels of C8-C40 n-alkanes and 18 polycyclic aromatic hydrocarbons (PAHs) in water and sediment from Loskop Dam (Mpumalanga Province South Africa), were investigated between 2015 and 2017. In addition, their sources, which have not been well defined, were also studied over the period. This water body is sourced from a historically contaminated water body, the Olifants River, which flows through areas where a range of industrial and agricultural activities take place. Mass crocodile and fish mortalities have been recorded in this aquatic system, and contamination by organic pollutants were highlighted as a contributing factor. The total average n-alkane concentrations in water and sediments ranged from 0.574±00811 to 18.8±1.39 μg/L and 4760±243 to 30700±906 μg/kg, respectively. Similarly, PAHs were detected at total average concentrations of between 0.150±00494 and 49.8±6.86 μg/L in water and 61.6±5.95 to 2618±300 μg/kg. n-Alkane and PAH diag- nostic ratios indicated a mixture of sources of these compounds, attributed to terrestrial, submerged and floating plant material, as well as petrogenic and pyrogenic combustion. Inlet, middle and upper segment site clustering was observed with non-metric multidimensional scaling (NMDS) and hierarchical cluster analysis (HCA), mainly driven by the prevalence of PAHs at the inlet sites and n-alkanes in the upper reaches. By using indicator compounds, the sources of contamination could be predicted. The strategy described here can be applied to any water body for continuous long-term monitoring of pollutant levels and to identify sources attributing to water pollution. © 2020 Elsevier Ltd. All rights reserved. 1. Introduction Many countries conduct monitoring programs that evaluate temporal and spatial trends in the physicochemical and biologi- cal aspects of environmental systems, particularly of freshwater re- sources (Abbaspour, 2011; Gazzaz et al., 2012). While risks posed by man-made chemicals can be directly evaluated by applying tar- geted mitigation strategies, those that are derived from biogenic, terrestrial, as well as anthropogenic sources, are difficult to de- termine and trace back to initial sources (Gazzaz et al., 2012). These include n-alkanes and PAHs, which occur naturally as com- plex mixtures (Ficken et al., 2000; Yunker et al., 2002; Neff et al., 2005; Wang et al., 2013; Chevalier et al., 2015; Wang et al., 2018). These contaminants have been detected in water, fish, coals, flood- plain soils and river sediments in the vicinity of coal mines and ∗ Corresponding author at. E-mail addresses: 37178857@nwu.ac.za, mpseopela@uj.ac.za (M.P. Seopela). processing industries by numerous researchers (Mici ´ c et al., 2011; Seopela et al., 2016; Wang et al., 2018). Their inherent physico- chemical properties make their detection and source apportion- ment challenging, but crucial. In addition, the assessment of these compounds in aquatic systems is of particular importance since they may pose a risk to a range of organisms (Gazzaz et al., 2012; Venturini et al., 2015). The traditional approach for evaluating the sources of contam- inants in the environment is through the use of indices. These in- clude individual compound abundances, as a proxy to estimate the sources (Venturini et al., 2015; Wang et al., 2018; Pinheiro et al., 2017). The most widely applied and well-studied compounds for source apportionment are n-alkanes and PAHs (Yunker et al., 2002; de Souza et al., 2011; Wang et al., 2018; Pinheiro et al., 2017). Their relative abundances are used to explicate differences be- tween natural and anthropogenic input of these compounds in wa- ter (Ji-xiang and Jia, 2011; Syakti et al., 2017; Yang et al., 2018; Xu et al., 2020), sediment (Yunker et al., 2002; de Souza et al., 2011; https://doi.org/10.1016/j.watres.2020.116350 0043-1354/© 2020 Elsevier Ltd. All rights reserved.