Temporal and spatial variations of organochlorine pesticides (OCPs) and phthalates affecting the quality of water and sediment from Loskop Dam, South Africa

Abstract

Organochlorine pesticides (OCPs) and phthalates are amongst the most emphasized man-made environmental contaminants, due to their prevalence, persistence and potential to induce adverse effects in organisms. In addition to prevailing industrial and domestic activities, their presence in the environment is exacerbated by leaching from associated materials, run-off and emissions. The Loskop Dam in the Mpumalanga Province, South Africa, is located on the Olifants River, which flows through a hub of industrial and agricultural activities. Research aimed at monitoring the levels of OCPs and phthalate contamination in South Africa, particularly in the Olifants catchment, has been limited and is restricted to short-term monitoring. In this study, the spatial and temporal variations of 21 OCPs and 7 phthalates in water and sediments from Loskop Dam were evaluated over a 3-year period (2015–2017). Annual average OCP levels ranged from 0.013±0.006 to 0.36±0.13 μg/L in water and from below the limit of detection to 2.4±1.2 µg/kg in sediments. Phthalates were present at average concentrations ranging from 0.023±0.041 to 2.1±1.5 μg/L and 20±0.63 to 55±6.9 µg/kg in water and sediments, respectively. The levels of OCPs and phthalates were greatest in autumn, attributed to higher input sources and concentration effects due to lower water levels. Phthalates were present at greater quantities at the inlet, while OCP accumulation was observed at the upper reaches of the dam. This may be an indication of the differences in input sources and translocation of these compounds, related to the topography of the dam and variability in water flow rates. These findings are important in highlighting the environmental and health concerns that may arise in the Olifants catchment area. After considering the outcomes of this study, we propose the implementation of regular and stringent monitoring strategies, which include surveys of OCPs and phthalates for Loskop Dam and similar water systems globally.

Review of scientific literature on available methods of assessing organochlorine pesticides in the environment

“…Poor recovery can result in erroneous results and compromise the accuracy and reliability of the analysis and can occasionally result in false negatives. Analyte breakdown in the instrument can result in low recoveries, for example DDT and endrin are most likely to breakdown in the GC inlet [ 71 ]. Large matrix effects have been reported by the US Department of Agriculture in residue analysis at low spike concentration (with 50–150 % recoveries) which cannot be entirely removed by cleanup procedures (Dana Ayu Mustofa et al, 2022).…”

“…Then, the temperature was increased to 175 °C with a ramp of 30 °C/min and then kept for 4 min. Next, the oven temperature was increased to 225 °C with a ramp of 3 °C/min and kept at this final temperature for 10 min” [ 141 ] Water, sediment 25 Water: 6.3–21; sediment: 1.3–4.1 Water: 21–68 ng/mL; sediment: 4.2–14 CRM: 79.2 to 117; Water: 46.6 to 119; sediment: 86.7–117 Water: 0.05–20; sediment: 0.7–17 GC-MS: “initial temperature of 50 °C, held for 1 min, ramped at 5 °C/min to 180 °C, held for 3 min, and increased to 300 °C at 10 °C/min, maintained for 7 min, equating to a total run time of 49 min” [ 71 ] Water, Soil, sediment 20 Surrogate: 65 and 105 <15 GC-ECD: “The oven temperature program began at 100 °C, held for 1 min, raised to 200 °C at 4 °C·min −1 , then to 230 °C at 2 °C·min −1 , and ramped to 280 °C at 8 °C·min −1 , and held for 15 min” [ 142 ] Water, planktons and corals 8 MDL: Seawater: 2 e−09-1.6e-08: marine biota; 0.0009–0.0013 74–110 GC-MS/MS: “The oven temperature was programmed as follows: 80 °C for 5min, at 20 °C min-1 to 160 °C, at 4 °C min −1 to 240 °C, at 10 °C min −1 to 295 °C with a final hold for 2min”. RT: 11.4–26.3 [ 89 ] Water, biota 16 MDL: 3.3e -07-1.25 e−06 75–89 5.9 [ 143 ] lake 12 0.01 40–100 GC-MS/MS: “The GC programming was as: The primary temperature was 70 °C and hold for 2 min, then ramped up to 150 °C at 25 °C/min, then ramped up to 200 °C at 3 °C/min, finally ramped up to 280 °C at 8 °C/min and hold for 10 min” [ 144 ] Gas and particulate phase 13 …”