Towards a multi-bioassay-based index for toxicity assessment of fluvial waters

Evaluating ecotoxicological assays for comprehensive risk assessment of toxic metals present in industrial wastewaters in the Republic of Korea

Toxicity tests represent a rapid, user-friendly and cost-effective means to assess the impact of wastewater quality on aquatic ecosystems. There are not many cases where wastewater management standards are set based on various bio-based ecotoxicity values. Here, we tested a novel multitaxon approach to compare standard water quality indices to toxicity metrics obtained from ecotoxicity tests, conducted using aquatic organisms representing several trophic levels (Aliivibrio, Ulva, Daphnia, and Lemna), for 99 industrial wastewater samples from South Korea. For five wastewater samples, the concentrations of Se, Zn, or Ni exceeded the permissible limits (1, 5, and 3 mg L^-1, respectively). All the four physiochemical water quality indices tested were positively correlated with Se and Pb concentrations. The toxicity unit (TU) scores indicated a declining sensitivity to pollutants, in the order Lemna (2.87) >Daphnia (2.24) >Aliivibrio (1.78) >Ulva (1.42). Significant correlations were observed between (1) Cd and Ni, and Aliivibrio, (2) Cu and Daphnia, (3) Cd, Cu, Zn, and Cr and Lemna, and (4) Cu, Zn, and Ni and Ulva. Daphnia-Lemna and Lemna-Ulva were found to be good indicators of ecologically harmful Se and Ni contents in wastewater, respectively. We suggest that regulatory thresholds based on these bioassays should be set at TU = 1 for all the species or at TU = 1 for Aliivibrio and Ulva and TU = 2 for Daphnia and Lemna, if the number of companies whose wastewater discharge exceeds the allowable TU levels is <1 % or 5 % of the total number of industries, respectively. Taken together, these findings could help in establishing a rapid, ecologically relevant wastewater quality assessment system that would be useful for developing strategies to protect aquatic ecosystems.

Effects of NaHSO3 on Cellular Metabolic Energy, Photosynthesis and Growth of Iris pseudacorus L

According to the law of energy conservation, the energy consumed by plants to resist adversity is equal to the difference between photosynthetic energy and growth energy consumption and cellular metabolic energy in plants. The cellular metabolic energy is calculated based on the electrical signals in plants. This study mainly investigated the effect of NaHSO3 on the growth and energy traits of the aquatic plant Iris pseudacorus L. and explored the effect of NaHSO3 on energy consumption in the process of plant development. In this study, NaHSO3 was used for simulating sulfur pollution in water medium. During the 20-day experiment period, the response of I. pseudocorus to the polluted water sources simulated by adding different concentrations of NaHSO3 (0, 0.5, 2, 4, 10 mmol·L−1) was monitored, and the internal mechanism of the relationship between the forms of energy and the removal of sulfur pollution was analyzed. After the 20-day exposure experiment, the growth and nutrient absorption capacity were significantly inhibited, and this inhibition proved to be concentration-dependent. In addition, high concentrations (4 and 10 mmol·L−1) of NaHSO3 might affect photosynthesis by disrupting cell membrane systems as it may interfere with membrane proteins and lipids and thus alter membrane integrity. Therefore, the cellular metabolic energy was increased and the sulfur absorption by I. pseudocorus was promoted under the low concentration (0.5 mmol/L−1) compared with the control, the role of NaHSO3 in promoting the growth of I. pseudocorus is much greater than its toxic effect under low concentrations. Under the hydroponic culture which contained 0.5 mmol·L−1 of NaHSO3, I. pseudocorus grew well and absorbed more sulfur. The results can be used as a reference for the cultivation of aquatic plants dealing with sulfur pollution, and dilution strategy can be set up to treat water medium that is seriously polluted with sulfur.

Assessment of five live-cell characteristics in periphytic diatoms as a measure of copper stress

Metal pollution of fluvial systems remains a major problem and biomonitoring can be a useful tool for assessing the metal contamination. To assess their potential as new bioindicators of copper stress, we treated a field-collected live periphytic diatom community (dominated by Amphora, Navicula, and Nitzschia) with dissolved Cu under optimal growth conditions. We studied the effects of Cu on five live-cell attributes: motility, protoplasmic content, lipid body number and biovolume, and frustule morphology. In all three genera, motility and protoplasmic content decreased, whereas the LB number, biovolume and deformity increased when Cu and exposure time increased. The sensitivity to Cu was highest for % MF, % CPC and % BCLB in Navicula and the LB number and deformity in Nitzschia. Amphora appeared to be more tolerant to Cu in comparison with other genera. The five cell attributes were inter-related. A heatmap showed that a recommended indicator for rapid screening of Cu toxicity was % BCLB for Amphora and % MF for Navicula and Nitzschia. % MF might be the most common representative indicator that can be applied to all three genera to evaluate the lethal effects of Cu stress if only one of the five cell attributes must be selected.

Metal concentrations and biological effects from one of the largest mining disasters in the world (Brumadinho, Minas Gerais, Brazil)

The rupture of the Brumadinho mining tailings dam in Brazil is considered one of the largest mining disasters in the world, resulting in 244 deaths and 26 missing people, in addition to the environmental consequences. The present study aims to evaluate the concentrations of multiple elements and the biological effects on water and sediments of the Paraopeba River after the Brumadinho Dam rupture. The tailings are formed by fine particulate material with large amounts of Fe, Al, Mn, Ti, rare earth metals and toxic metals. In the water, the levels of Fe, Al, Mn, Zn, Cu, Pb, Cd and U were higher than those allowed by Brazilian legislation. In the sediments, Cr, Ni, Cu and Cd levels were higher than the established sediment quality guidelines (TEL-NOAA). The differences in metal concentrations in the water and sediments between the upstream and downstream sides of the dam illustrate the effect of the tailings in the Paraopeba River. Toxicological tests demonstrated that the water and sediments were toxic to different trophic levels, from algae to microcrustaceans and fish. The fish exposed to water and sediments containing mine ore also accumulated metals in muscle tissue. This evaluation emphasizes the necessity of long-term monitoring in the affected area.