Ecotoxicity of eluates obtained from Basamid? contaminated soils is pH dependent: A study with Hydra viridissima, Xenopus laevis and Danio rerio

Agrochemicals are mostly used to deplete pests and treat diseases in terrestrial agro-ecosystems. However, their transport through the soil, by leaching and/or runoff, may cause them to reach aquatic systems. Environmental parameters, such as soil pH, can affect this transport, by influencing the magnitude of agrochemicals degradation and chemical reaction. This work aimed at investigating the influence of soil pH on the toxicity of eluates obtained from Basamid (R) contaminated soils to Hydra viridissima, Xenopus laevis and Danio rerio. For this, a natural soil with pH amended to 5.5, 6.5 and 7.5, was spiked with the recommended dose (RD) of Basamid (R) (145 mg dazomet/kg soil) and eluates (Ba-E) were prepared with the respective species culture medium. Dilutions of the eluates (0.14-100%), obtained from the three soils (Ba-E 5.5, Ba-E 6.5 and Ba-E 7.5, corresponding to soil spiked with Basamid (R) RD at soil pH of 5.5, 6.5 and 7.5, respectively), were used to expose the organisms. Results showed that for H. viridissima increased soil alkalinity provoked less mortality comparatively to lower soil pH [LD50,96h of Ba-E 5.5: 10.6% and LD50,96h of Ba-E 7.5: 21.2%]. As for X. laevis and D. rerio Ba-E lethal ecotoxicity was similar across soil pH (LD50,96h varied from 5.7 to 6.9% and from 2.1 to 4.3%, respectively). For malformations, 20% effect dilution (ED) in H. viridissima was significantly higher at Ba-E 7.5 (ED20,96h: 17.4%), comparatively to Ba-E 5.5 and Ba-E 6.5 (ED20,96h: 7.9% and 7.7%, respectively). From the three tested organisms and based on both lethal and sublethal effects, H. viridissima presented the highest tolerance to Basamid (R) eluates and soil pH was a major factor determining the fumigant toxicity, with higher soil pH levels inducing, lower toxicity. The eluates obtained from soils contaminated with RD of Basamid (R) induced severe effects to the three aquatic species.

Automated summary

This study aimed to investigate the influence of soil pH on the toxicity of eluates obtained from Basamid (R) contaminated soils to three aquatic species. The results showed that higher soil alkalinity decreased mortality of H. viridissima, while it had similar lethal ecotoxicity on X. laevis and D. rerio across different soil pH levels. H. viridissima exhibited the highest tolerance to Basamid (R) eluates, and soil pH was a major factor in determining the fumigant toxicity.