Biochar alleviates the toxicity of imidacloprid and silver nanoparticles (AgNPs) to Enchytraeus albidus (Oligochaeta)

Abstract

The present study investigated the use of biochar for the alleviation of the toxic effects of a nanosilver colloidal dispersion and a chloronicotinyl insecticide. The survival and reproduction of the potworm Enchytraeus albidus were assessed after exposure to imidacloprid and silver nanoparticles (AgNPs). E. albidus was exposed to 0, 25, 50, 100, 200, and 400 mg imidacloprid/kg and 0, 5, 25, 125, and 625 mg Ag/kg for 21 days in 10% biochar amended and non-biochar amended OECD artificial soil. In both exposure substrates, the effects of imidacloprid on survival were significant in the two highest treatments (p < 0.01). No biochar effect was observed as survival was statistically similar in both soils after exposure to imidacloprid. In the case of AgNPs, significant mortality was only observed in the highest AgNP treatments in both the amended and non-amended soils (p < 0.05). Nevertheless, statistically greater survival occurred in the biochar-amended treatment (p < 0.05). Reproduction results showed a more pronounced biochar effect with an EC = 22.27 mg imidacloprid/kg in the non-amended soil and a higher EC = 46.23 mg imidacloprid/kg in the biochar-amended soil. This indicated a 2-fold decrease in imidacloprid toxicity due to biochar amendment. A similar observation was made in the case of AgNPs where a reproduction EC = 166.70 mg Ag/kg soil in the non-amended soil increased to an EC > 625 mg Ag/kg soil (the highest AgNP treatment) in the amended soil. This indicated at least a 3.7-fold decrease in AgNPs toxicity due to biochar amendment. Although more studies may be needed to optimize the easing effects of biochar on the toxicity of these chemicals, the present results show that biochar could be useful for the alleviation of the toxic effects of imidacloprid and silver nanoparticles in the soil.

Reproduction and biomarker responses of Eisenia fetida after exposure to imidacloprid in biochar-amended soil

“…However, this concentration (w/w, i.e., 400 mg/kg of dry soil) could not be used in the present study because imidacloprid has been reported to have a median lethal concentration (LC 50 ) ranging from 2 to 4 mg/kg of dry soil in earthworms such Eisenia fetida, Aporrectodea nocturna and Allolobophora icterica (Luo et al 1999;Zang et al 2000;Capowiez et al 2005). For the purpose of the present study, therefore, Aphicide Plus ® was used to make the following nominal concentration series of imidacloprid, following the method of Nyoka et al (2018): 0 (negative control) 0.75, 1.5, 2.25, and 3 mg/kg of dry soil.…”

“…Although designed to control agricultural pests such as the Russian wheat aphid (Diuraphis noxia)according to the manufacturer-imidacloprid has been found to be deleterious to non-target organisms. Adverse effects include mortality, weight loss, sperm deformity, decrease in reproduction, nervous breakdown and more (Capowiez et al 2005;Luo et al 1999;Nyoka et al 2018;Suchail et al 2001;Zang et al 2000). At a very low concentration (0.1 μg/L), imidacloprid was found to cause significant mortality in honeybees (Apis mellifera) after 10-day exposure (Suchail et al 2001).…”

“…At a very low concentration (0.1 μg/L), imidacloprid was found to cause significant mortality in honeybees (Apis mellifera) after 10-day exposure (Suchail et al 2001). Nyoka et al (2018) documented a reproduction EC 50 of 22 mg/kg after exposing the potworm Enchytraeus albidus to imidacloprid. In two laboratory studies conducted using Eisenia fetida, an LC 50 of 2.3 mg/kg and evidence of sperm deformity were reported following a 14-day exposure to imidacloprid (Luo et al 1999;Zang et al 2000).…”

High Rates of Biochar Soil Amendment Cause Increased Incidences of Neurotoxic and Oxidative Stress in Eisenia fetida (Oligochaeta) Exposed to Glyphosate

“…Prior to exposure, the earthworms were allowed to empty their guts overnight, and were weighed. Ten adult E. fetida were exposed to 500 g of each treatment of glyphosate in biochar-amended and non-amended soils, which were then incubated at 20 ± 1 • C (in a Labcon low temperature incubator) for 96 h. This exposure duration was chosen not only to fill a gap in the literature, because similar studies on biochar typically last longer [17,20,23,24] but also to increase our likelihood of observing biomarker responses, which can peak in the early days of such an exposure and vanish after relatively longer exposure durations [18]. All exposures were made in triplicates.…”

“…Biochar results from biomass pyrolysis under the limited presence or complete absence of oxygen at temperatures greater than 250 • C. Because of its stability and absorbent properties, some view biochar amendment as a means to mitigate the effects of chemicals in soils [14,15]. Such toxicity mitigating abilities have been shown after soil amendment in the cases of the spring onion Allium cepa exposed to carbofuran and chlorpyrifos [16], the potworm Enchytraeus albidus exposed to imidacloprid and silver nanoparticles [17] and several earthworms species exposed to fomesafen, chlorantraniliprole, mesotrione, and imidacloprid [15,[18][19][20]. Despite these beneficial attributes, some have found that biochar amendment reduces the efficacy of soil pest management efforts due to its absorbent capacities [21,22] or worse causes direct harm to soil organisms such as earthworms [23][24][25][26].…”