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. 2020 Apr 15;17(8):2727.
doi: 10.3390/ijerph17082727.

Exploring the Environmental Exposure to Methoxychlor, α-HCH and Endosulfan-sulfate Residues in Lake Naivasha (Kenya) Using a Multimedia Fate Modeling Approach

Yasser Abbasi  1 , Chris M Mannaerts  1
Affiliations

Exploring the Environmental Exposure to Methoxychlor, α-HCH and Endosulfan-sulfate Residues in Lake Naivasha (Kenya) Using a Multimedia Fate Modeling Approach

Yasser Abbasi et al. Int J Environ Res Public Health. .

Abstract

Distribution of pesticide residues in the environment and their transport to surface water bodies is one of the most important environmental challenges. Fate of pesticides in the complex environments, especially in aquatic phases such as lakes and rivers, is governed by the main properties of the contaminants and the environmental properties. In this study, a multimedia mass modeling approach using the Quantitative Water Air Sediment Interaction (QWASI) model was applied to explore the fate of organochlorine pesticide residues of methoxychlor, α-HCH and endosulfan-sulfate in the lake Naivasha (Kenya). The required physicochemical data of the pesticides such as molar mass, vapor pressure, air-water partitioning coefficient (KAW), solubility, and the Henry's law constant were provided as the inputs of the model. The environment data also were collected using field measurements and taken from the literature. The sensitivity analysis of the model was applied using One At a Time (OAT) approach and calibrated using measured pesticide residues by passive sampling method. Finally, the calibrated model was used to estimate the fate and distribution of the pesticide residues in different media of the lake. The result of sensitivity analysis showed that the five most sensitive parameters were KOC, logKow, half-life of the pollutants in water, half-life of the pollutants in sediment, and KAW. The variations of outputs for the three studied pesticide residues against inputs were noticeably different. For example, the range of changes in the concentration of α-HCH residue was between 96% to 102%, while for methoxychlor and endosulfan-sulfate it was between 65% to 125%. The results of calibration demonstrated that the model was calibrated reasonably with the R2 of 0.65 and RMSE of 16.4. It was found that methoxychlor had a mass fraction of almost 70% in water column and almost 30% of mass fraction in the sediment. In contrast, endosulfan-sulfate had highest most fraction in the water column (>99%) and just a negligible percentage in the sediment compartment. α-HCH also had the same situation like endosulfan-sulfate (e.g., 99% and 1% in water and sediment, respectively). Finally, it was concluded that the application of QWASI in combination with passive sampling technique allowed an insight to the fate process of the studied OCPs and helped actual concentration predictions. Therefore, the results of this study can also be used to perform risk assessment and investigate the environmental exposure of pesticide residues.

Keywords: QWASI model; fate modeling; multimedia; organochlorine pesticides; passive sampling.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Schematic profile of the lake Naivasha and representation of the QWASI model (reproduced partly from Whelan (2013) [28]) for different environmental compartments.
Figure 2
Figure 2
Results of the sensitivity analysis for α-HCH in Lake Naivasha.
Figure 3
Figure 3
Results of the sensitivity analysis for methoxychlor in Lake Naivasha.
Figure 4
Figure 4
Results of the sensitivity analysis for endosulfan–sulfate in Lake Naivasha.
Figure 5
Figure 5
Comparison of the average measured and estimated concentrations of pesticide residues in the aquatic phase of Lake Naivasha.
Figure 6
Figure 6
The D values of different processes that affect the fate of contaminants.
Figure 7
Figure 7
Mass balance diagram of different pesticides (α-HCH, endosulfan–sulfate and Methoxychlor) residues in the lake Naivasha.
Figure 7
Figure 7
Mass balance diagram of different pesticides (α-HCH, endosulfan–sulfate and Methoxychlor) residues in the lake Naivasha.
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