Effectiveness of a Constructed Wetland with Carbon Filtration in Reducing Pesticides Associated with Agricultural Runoff

The Salinas Valley in Monterey County, California, USA, is a highly productive agricultural region. Irrigation runoff containing pesticides at concentrations toxic to aquatic organisms poses a threat to aquatic ecosystems within local watersheds. This study monitored the effectiveness of a constructed wetland treatment system with a granulated activated carbon (GAC) filter installation at reducing pesticide concentrations and associated toxicity to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus. The wetland was supplied with water pumped from an impaired agricultural and urban drainage. Across five monitoring trials, the integrated system’s average pesticide concentration reduction was 52%. The wetland channel and GAC filtration components individually provided significant treatment, and within each, pesticide solubility had a significant effect on changes in pesticide concentrations. The integrated treatment system also reduced nitrate by 61%, phosphate by 73%, and turbidity by 90%. Input water was significantly toxic to C. dubia and H. azteca in the first trial. Toxicity to C. dubia persisted throughout the system, whereas toxicity to H. azteca was removed by the channel, but there was residual toxicity post-GAC. The final trial had significant input toxicity to H. azteca and C. dilutus. The channel reduced toxicity to H. azteca and removed toxicity to C. dilutus. GAC filtration reduced H. azteca toxicity to an insignificant level. There was no input toxicity in the other three trials. The results demonstrate that a wetland treatment system coupled with GAC filtration can reduce pesticide concentrations, nutrients, suspended particles, and aquatic toxicity associated with agricultural runoff.

Environmental concerns about the massive use of disinfectants during COVID-19 pandemic: an overview on aquatic toxicity

Many public health measures to mitigate the spread of SARS-CoV-2 were adopted worldwide, and particularly to the environmental measure of regular cleaning and disinfection of surfaces, the increased use of disinfectant products raises environmental concerns. Quaternary ammonium compounds (QACs), povidone-iodine (PVP-I), chloroxylenol (PCMX) and chlorhexidine (CHX) are the active ingredients of most disinfectant products due to their effectiveness against various microbiological agents. Although presenting antimicrobial efficacy, these biocides have been associated with impacts on aquatic life. For instance, QACs can induce toxicity to Aliivibrio fischeri and fish (different species). Gill and liver damages are verified in Cyprinus carpio after exposure to PVP-I. CHX induces toxic effects on algae, crustaceans, and fish embryos. PCMX can induce genotoxicity to rainbow trout and malformations on zebrafish embryos, as well as it can reduce the reproduction rate of Caenorhabditis elegans. Thus, the potential to cause negative consequences on human and environmental health has resulted in activities from the U.S. and European agencies to favor the use of safer and greener disinfectant products during the COVID-19 pandemic. This review article summarizes the main findings on the impacts of disinfectants (the most used) on aquatic life. This information may help prioritize disinfectants with lower impacts on the aquatic environment for daily use, and especially for high-frequency use as verified in the COVID-19 pandemic. Furthermore, this review may help identify knowledge gaps on the aquatic hazard of disinfectants, which may drive future studies on this matter and, lastly, contribute to the development of sustainable products.

Synthesis, Characterisation, Photocatalytic Activity, and Aquatic Toxicity Evaluation of TiO2 Nanoparticles

Imidacloprid (IMD) is a toxic pesticide, and is one of the eight most widely used pesticides globally. Heterogeneous photocatalysis has often been investigated in recent years and can be successfully applied to remove imidacloprid from water. However, less investigated is the toxic effect of both the photocatalyst and the pesticide on aquatic life. Titanium dioxide (TiO2) remains the most effective photocatalyst, provided it is not toxic to the aquatic environment. This study investigated the TiO2 synthesis, characterisation, and photocatalytic activity on imidacloprid degradation and the toxicity of TiO2 nanoparticles and imidacloprid on the green algae Chlorella vulgaris. In the photodegradation process of IMD (initial concentration of 20 mg/L), electrons play an essential role; the degradation efficiency of IMD after 6 h increased from 69 to 90% under UV irradiation when holes (h+) scavengers were added, which allowed the electrons to react with the pollutant, resulting in lowering the recombination rate of electron-hole charge carriers. Growth inhibition of Chlorella vulgaris and effective concentration (EC50) were determined to study the toxic effect of TiO2 nanoparticles and imidacloprid. The EC50 increased from 289.338 mg/L in the first 24 h to 1126.75 mg/L after 96 h Chlorella vulgaris algal age, when the toxicant was TiO2. When IMD was the aquatic toxicant, a decrease in EC50 was observed from 22.8 mg/L (24 h) to 0.00777 mg/L (120 h), suggesting a long-term high toxicity level when pesticides in low concentrations are present in an aquatic environment.

Insight Into The Aquatic Toxicity And Ecological Risk of Bisphenol B, And Comparison With That of Bisphenol A

As one of the alternatives of 2,2-bis(4-hydroxyphenyl)propane (bisphenol A, BPA), 2,2-bis(4-hydroxyphenyl)butane (bisphenol B, BPB) has not gained sufficient concerns so far, due to the limited concentration and toxicity data available. In this study, the acute toxicity of BPB to three aquatic organisms, i.e., Tetradesmus obliquus, Daphnia magna and Danio rerio, was investigated, and it showed that Daphnia magna was the most sensitive organism with the half effective concentration (EC50) of 3.93 mg/L. Thereout, the screened Daphnia magna was exposed to BPB for 21 days to explore the chronic toxicity. Results indicated that BPB restricted the body length of parent Daphnia magna and reduced the total number of broods and neonates. The no-observed effect concentration of BPB to Daphnia magna was as low as 0.01 mg/L, which was two orders of magnitude lower than that reported 0.86–5.00 mg/L of BPA. Furthermore, the ecological risk of BPB was quantitatively assessed using the risk quotient (RQ) method. Obviously, although the environmental concentrations and detectable rate of BPB were much lower than that of BPA, its ecological risk was not necessarily lower. Hence, BPB should not be ignored in the future environmental monitoring and management.

Aquatic Toxicity Effects and Risk Assessment of ‘Form Specific’ Product-Released Engineered Nanomaterials

The study investigated the toxicity effects of ‘form specific’ engineered nanomaterials (ENMs) and ions released from nano-enabled products (NEPs), namely sunscreens, sanitisers, body creams and socks on Pseudokirchneriella subcapitata, Spirodela polyrhiza, and Daphnia magna. Additionally, risk estimation emanating from the exposures was undertaken. The ENMs and the ions released from the products both contributed to the effects to varying extents, with neither being a uniform principal toxicity agent across the exposures; however, the effects were either synergistic or antagonistic. D. magna and S. polyrhiza were the most sensitive and least sensitive test organisms, respectively. The most toxic effects were from ENMs and ions released from sanitisers and sunscreens, whereas body creams and sock counterparts caused negligible effects. The internalisation of the ENMs from the sunscreens could not be established; only adsorption on the biota was evident. It was established that ENMs and ions released from products pose no imminent risk to ecosystems; instead, small to significant adverse effects are expected in the worst-case exposure scenario. The study demonstrates that while ENMs from products may not be considered to pose an imminent risk, increasing nanotechnology commercialization may increase their environmental exposure and risk potential; therefore, priority exposure cases need to be examined.

Aquatic Toxicity Integrated Testing and Assessment Strategies (ITS) for Difficult Substances: Case Study With Thiochemicals

Background An Integrated Testing and Assessment Strategy (ITS) for aquatic toxicity of 16 thiochemicals to be registered under REACH revealed 12 data gaps, which had to be filled by experimental data. These test results are now available and offer the unique opportunity to subject previous estimates obtained by read-across (analogue and category approaches) to an external validation. The case study thiochemicals are so-called difficult substances due to instability and poor water solubility, challenging established ITS. Results The new experimental data confirm the previous predictions of acute aquatic toxicity with the new test results indicating a 2-5 times lower toxicity than previously predicted. The previous predictions thus are conservative and closer to the experimental results than expected. The good agreement can be attributed to the fact that we had limited the extrapolations to narrow chemical groups with similar SH-group reactivities. The new experimental data further strengthen and externally validate the existing trends based on similarity in chemical structures, mode of action (MoA), water solubility and stability of source and target compounds in aquatic media. Based on the new experimental data, reliable revised PNECs could be derived and the REACH requirements for these thiochemicals are largely fulfilled. Appropriately adapted ITS are therefore able to reduce in vivo tests with fish even for difficult substances and replace them with alternative information. Conclusions Both experimental and alternative information for difficult substances such as thiochemicals that are rapidly transformed in water are subject to considerable uncertainty. For example, the use of nominal, initial or time-weighted average concentrations, contribute variability in the determination of aquatic toxicity. The use of nominal concentrations is likely to be the most appropriate choice as it reflects realistic worst-case environmental conditions in these cases. In general, uncertainties in (historical) test results and alternative information (read-across) must be considered in terms of how much uncertainty is acceptable for environmental protection on the one hand and how much certainty is technically feasible on the other.

Assessment of Toxicity and Biodegradability of Poly(vinyl alcohol)-Based Materials in Marine Water

Due to the continuous rise in conventional plastic production and the deficient management of plastic waste, industry is developing alternative plastic products made of biodegradable or biobased polymers. The challenge nowadays is to create a new product that combines the advantages of conventional plastics with environmentally friendly properties. This study focuses on the assessment of the potential impact that polyvinyl alcohol (PVA)-based polymers may have once they are released into the marine environment, in terms of biodegradation in seawater (assessed by the percentage of the Theoretical Oxygen Demand, or % ThOD, of each compound) and aquatic toxicity, according to the standard toxicity test using Paracentrotus lividus larvae. We have tested three different materials: two glycerol-containing PVA based ones, and another made from pure PVA. Biodegradation of PVA under marine conditions without an acclimated inoculum seems to be negligible, and it slightly improves when the polymer is combined with glycerol, with a 5.3 and 8.4% ThOD achieved after a period of 28 days. Toxicity of pure PVA was also negligible (<1 toxic units, TU), but slightly increases when the material included glycerol (2.2 and 2.3 TU). These results may contribute to a better assessment of the behavior of PVA-based polymers in marine environments. Given the low biodegradation rates obtained for the tested compounds, PVA polymers still require further study in order to develop materials that are truly degradable in real marine scenarios.