Effect of linear alkylbenzene sulfonate on the uptake of microcystins by Brassica oleracea and Solanum tuberosum

Abstract

Background: Globally, hypereutrophic conditions in major water reservoirs used for irrigation purposes, promote the co-existence of cyanotoxins and other pollutants such as linear alkylbenzene sulfonate (LAS). LAS is known to alter the permeability of membranes and promote the uptake of other pollutants by plants. In light of the potential human health risks and prevailing hypereutrophic conditions in some catchments in South Africa, we investigated the combined effects of LAS and microcystins (MCs) on food plants when cyanobacteria infested water is used to irrigate terrestrial crops.

Methods: To understand the potential risks, pot-culture experiments were conducted to assess the effect of LAS on the accumulation of MCs in Brassica oleracea (cabbage) and Solanum tuberosum (potato) plants. The plants were watered with dam water containing 3.48 mg L ^-1 of the LAS (sodium dodecyl sulfate) and MCs (MC-LR: 10.47 ± 3.879; 6.158 ± 4.127 for MC-RR and 8.160 ± 2.544 for MC-YR μg L ^-1) for 20 days.

Results: The presence of LAS, at environmentally relevant concentrations in the irrigation water, did not enhance the uptake of MCs in the two plants, as demonstrated by statistically insignificant differences in the means of the treatments (with and without LAS). In addition, the presence of LAS, high pH, electrical conductivity (EC), and cyanotoxins in the water did not affect the total chlorophyll or the well-being of the plants. However, in some cases the levels of MCs bioaccumulated by the two plants exceeded the WHO recommended tolerable daily intake (TDI).

Conclusions: These findings imply that the tested levels of LAS and MCs did not have any synergic effects on the two plant species, but irrigating food crops with such water still poses a human health risk.

Keywords: Brassica oleracea; Linear alkylbenzene sulfonate; Microcystins; Solanum tuberosum; combined effects.

Figure 1.. Calibration curves obtained for (a) Microcystin-RR (MC-RR); (b) MC-YR; and (c) MC-LR; in B. oleracea leaf extract.

Figure 2.. MRM chromatograms of quantification ions for the three MCs, (a) MC-RR; (b) MC-YR and (c) MC-LR at a concentration of 100 μg L ^-1.

Figure 3.. Total chlorophyll in (i) cabbage ( Brassica oleracea) leaves (ii) potato ( Solanum tuberosum) leaves, after 20 days of exposure to the four treatments.