Antioxidant Enzyme Activity and Lipid Peroxidation in Aporrectodea caliginosa Earthworms Exposed to Silver Nanoparticles and Silver Nitrate in Spiked Soil

Silver nanoparticles (AgNPs) from industrial use, discharged via the land application of sewage sludge, are interacting with soil biota, including earthworms. In affected organisms, excessive production of reactive oxygen species can result in lipid peroxidation, shifting the balance between oxidants and antioxidants to cause oxidative stress. We determined selected lower-tier biomarkers such as antioxidant responses and lipid peroxidation in Aporrectodea caliginosa earthworms exposed to soils spiked with AgNPs or silver nitrate (AgNO₃ ). Aporrectodea caliginosa were exposed to AgNPs at 0 (control), 0.3, 3, 30, and 300 mg/kg or Ag⁺ (as AgNO₃ ) at 0, 0.03, 0.3, 3, and 10 mg/kg in soil for 4 wk. At 1, 2, 3, and 4 wk, the activity of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, as well as lipid peroxidation (malondialdehyde content), increased as a function of concentration, with a much larger response for Ag⁺ than AgNPs. Given the likelihood of ever-increasing AgNP concentrations in soil, where AgNPs can transform to ionic Ag (Ag⁺ ), our findings of antioxidant response to oxidative stress in a common indicator organism even at an environmentally realistic exposure concentration of 0.03 mg/kg demonstrate that AgNPs may affect soil fertility and, thus, agricultural production. Evaluating selected lower-tier biomarkers offers a meaningful assessment of AgNPs and Ag⁺ effects on terrestrial earthworms. Environ Toxicol Chem 2020;39:1257-1266. © 2020 SETAC.

A sensitive optical-based test method for the locomotor activity of earthworms

The outdated test methodologies for terrestrial animals have limited the progress of soil ecotoxicology to some extent. To improve the behavioral testing of earthworms, a terrestrial model animal, a sensitive optical-based method for detecting locomotor activity was established. The method measured the fine quantified position offsets of each earthworm in place of a conventional overall response rate, which provided the feasibility for accurate analyses and comparisons. By setting appropriate thresholds, the time proportions of medium and burst states (mid-burdur%) could be an optimized endpoint with an ideal balance in output stability and sensitivity. In addition, we chose the head-end, which is the most flexible part of the earthworm, other than whole body to further elevate the sensitivity in indicating the changed traits. Using octopamine, serotonin, and a serial-dose of lindane exposure, the practice credibility of the test method was validated. Our developed locomotor test method overcame the innate characteristics of the earthworm, and was expected to provide a powerful phenotypic tool for ecological and ecotoxicological studies using earthworms and similar invertebrates.

Life Cycle Impact and Benefit Trade-Offs of a Produced Water and Abandoned Mine Drainage Cotreatment Process

A cotreatment process for produced water and abandoned mine drainage (AMD) has been established and demonstrated at the pilot-scale. The present study evaluates the potential of the proposed process to aid in management of two high volume wastewater resources in Pennsylvania. A systems-level approach is established to evaluate the primary trade-offs, including cotreatment process environmental impacts, transportation impacts, and environmental benefits realized from precluding direct AMD release to the environment. Life cycle impact assessment was used to quantify the environmental and human health impacts as well as to identify "hot spots" of the cotreatment process. Electricity use was found to be the dominant contributor to all impact categories. Extending the system boundary to include transportation of the two wastewaters to a to-be-determined cotreatment site revealed the important impact of transportation. An optimization approach was employed (using the region of Southwest Pennsylvania) to evaluate minimization of transportation distance considering the location and number of treatment sites. Finally, a quantitative analysis of environmental benefits realized by precluding direct AMD release to the environment was performed. The results suggest that the magnitude of benefit realized in treating a highly polluted AMD is greater than the magnitude of impacts from the cotreatment process.

Nerve conduction velocity as a non-destructive biomarker in the earthworm Aporrectodea caliginosa exposed to insecticides

Earthworms are important and useful soil organisms, but in agricultural soils, they are potentially exposed to a wide variety of pesticides. Insecticides represent the highest threat to earthworms and many are neurotoxic. There is a need for a reliable, relevant, simple biomarker to assess the sub-lethal effects of neurotoxic insecticides on earthworms under laboratory or field conditions. The Aporrectodea caliginosa earthworms were exposed to 0 (control), 0.5×, 1× (normal field application rate), and 5× concentrations of a carbamate (Pirimor®) and an organophosphate (Lorsban®) insecticides. The nerve conduction velocity (NCV) of the medial giant fibers of A. caliginosa earthworm was recorded on days 0, 1, 2, 3, 4, and 7 to quantify sub-lethal neurotoxic effects. Acetylcholinesterase (AChE) enzyme activity of A. caliginosa homogenates was measured at the conclusion of the experiment. Pirimor® but not Lorsban® induced a significant decrease in NCV on days 3, 4, and 7 at 1× and 5× doses. A significant dose-dependent decrease was observed on AChE activity to Pirimor® at the doses used but not Lorsban®. A clear relationship is observed between AChE activity and NCV in the case of Pirimor®. This study showed that NCV is a sensitive biomarker that correlates well with classical biomarker measurements such as AChE enzyme activity. This technique could be used to study the impact of insecticides on earthworms and also their recovery.