Micro- (M-BC) and nano-biochar (N-BC) particles are ready to be disintegrated from biochar (BC), which is extensively applied to remediate heavy metal-contaminated soil. Still, its effects on the remediation efficiency remain poorly understood. This study investigated the interactions between the BC particles (M-BC and N-BC) and Eisenia foetida (E. foetida) in cadmium (Cd)-contaminated soils. Results indicated that M-BC has weak negative effect on E. foetida with survival rates of >= 85% as it is failed to be internalized. The interactive effects between M-BC/N-BC and Cd reduced the mobility of Cd, leading to low avoidance behavior of E. foetida. The synergistic effect of 0.1% M-BC and E. foetida caused pH regulation, BC diffusion and alternation of soil microbial community in the soil. This favored the remediation of Cd-contaminated soils with 56.2% Cd fixation efficiency identified. Conversely, internalization of Cd-loaded N-BC by E. foetida was recorded when 0.1% N-BC was amended in the soil. This triggered DNA damage, antioxidant suppression, antiapoptotic inhibition, digestion impairment, reproductive decline, and survival rates reduction (55%) in E. foetida, indicating the essential role of E. foetida in the soil is likely to be depressed. These findings are helpful to understand the potential negative effects of BC application in soil remediation.
Salinization of soil is a serious global environmental issue, particularly in agricultural lands. Saline farmland not only endangers grain production but also affects the survival of soil fauna. Earthworms, as soil ecosystem engineers, play a crucial role in maintaining soil health and enhancing global agricultural production. However, the response of earthworms to natural saline soil stress remains poorly understood. To explore this, we investigated the effects of natural saline soil from Dongying City, Shandong Province, China, on the growth, survival, reproduction, antioxidation, and defense-related gene expression of the earthworm Eisenia foetida. Our findings demonstrate that the growth rate, survival rate, and cocoon production of E. foetida decrease under exposure to natural saline soil in a dose-dependent manner. Elevated levels of DNA damage in coelomocytes and increased reactive oxygen species (ROS) were observed. Additionally, antioxidant enzymes, such as superoxide dismutase (SOD) and catalase (CAT), increased under stress. The mRNA levels of Cyp450 and Hsp70 also rose in response to saline soil exposure. Furthermore, the activity of Na+/K+-ATPase and the expression of the osmotic sensor gene
Biochar-supported nanoscale zero-valent iron (nZVI@BC) has been widely used in heavy metal contaminated soil for remediation. However, studies on the soil ecological effects of nZVI@BC were rare. In this study, nZVI@BC was synthesized by the liquid phase reduction and GnZVI@BC was prepared by a green synthesis method which was reduced by green tea extract instead of NaBH4. Earthworms (Eisenia foetida) as indicator organisms were exposed to Cd-contaminated soil. The immobilization effects and enrichment in earthworms of Cd were measured. Besides, oxidative stress, DNA damage, gene expression and transcriptomics of earthworms were deeply explored. The results indicated that the immobilization efficiency of BC, nZVI@BC and GnZVI@BC for Cd was 76.01%, 85.49%, and 80.76%, respectively. The effects of Cd on superoxide dismutase, glutathione Stransferase, peroxidase, and catalase in earthworms reduced, reactive oxygen species and malondialdehyde contents decreased, and DNA damage was relieved. In addition, the gene toxicity of Cd to earthworms was restrained, and the genes expression of sod, cat and gst tended to be stable. With nZVI@BC, the main pathways affected by the differential genes were cellular oxidative phosphorylation and transforming growth factor-beta signaling pathways. With GnZVI@BC, there were mainly structure of the cell phagosome, metabolism of taurine, hypotaurine, and alanine processes. This study will provide references for ecological risk assessment of nZVI@BC in practical applications.
Cyclic C6O4 (cC(6)O(4), CAS number 1190931-27-1) is a perfluoralkyl ether PFAS used as a polymerization aid in the synthesis of fluoropolymers and produced in Italy since 2011 as substitute of PFOA. To date, available ecotoxicological information on cC(6)O(4) is related to regulatory requirements and limited to data on aquatic organisms, while the information on the effects for terrestrial organisms is completely lacking. This work reports the first ecotoxicological data of cC(6)O(4) on terrestrial invertebrates: short- and long-term toxicity of cC(6)O(4) on Eisenia foetida (Savigny, 1826), exposed to spiked soil under laboratory conditions, was investigated evaluating the earthworm survival and growth (observed after 7, 14 and 28 days of exposure), and reproduction (observed after an exposure period of 56 days). Furthermore, also bioaccumulation was investigated (28 days of exposure); overall results are discussed in comparison with literature data available for legacy PFAS. cC(6)O(4) did not cause significant mortality on earthworms, for any of the tested concentrations and exposure periods (NOEC: > 1390 mg/kg d.w.), while the reproduction (measured as juveniles production) appears to be a more sensitive endpoint (EC50: 10.4 mg/kg d.w., EC10: 0.8 mg/kg d.w.). The observed adverse effects occur at levels significantly higher than realistic soil concentrations and cC(6)O(4) appears to be less toxic than PFOA and PFOS. As for bioaccumulation, the results indicate a negligible bioaccumulation potential of cC(6)O(4), whose Biota-Soil Bioaccumulation Factors (BSAF) are significantly lower than all other considered PFAS.
Nanoplastics may adsorb other pollutants in the environment due to their high specific surface area and small size. We used earthworms as experimental organisms to evaluate the ecotoxicity of NPs and Ni combined pollution at the individual and cellular levels. The results showed that when only 20 mg/L Ni2+ was added to the combined pollution system, the antioxidant system of earthworm coelomocytes was destroyed to a certain extent, the ROS level increased, the cell viability decreased significantly, and the redox balance was destroyed. With the introduction of PS-NPs and the increase of concentration, the oxidative damage in the coelomocytes of earthworms gradually increased, and finally tended to be stable when the maximum concentration of 50 mg/L PS-NPs and Ni were exposed together. At the animal level, the activities of CAT and SOD decreased within 28 days of exposure, and the combined pollution showed a synergistic effect. At the same time, it promoted the synthesis of GST in earthworms, improved their detoxification ability and reduced oxidative damage. The changes of T-AOC and MDA showed that the combined pollution caused the accumulation of ROS and caused more serious toxicological effects. With the increase of exposure time, the antioxidant system of earthworms was continuously destroyed, and the oxidative damage was serious, which induced more serious lipid peroxidation and caused the damage of earthworm body wall structure.