Rongxue Cui

Multispecies toxicity test for silver nanoparticles to derive hazardous concentration based on species sensitivity distribution for the protection of aquatic ecosystems

Abstract With increasing concerns about the release of silver nanoparticles (AgNPs) into the environment and the risks they pose to ecological and human health, a number of studies of AgNP toxicity to aquatic organisms have been conducted. USEPA and EU JRC have published risk assessment reports for AgNPs. However, most previous studies have focused on the adverse effects of AgNPs on individual species. Hazardous concentration (HC) of AgNPs for protection of aquatic ecosystems that are based on species sensitivity distributions (SSDs) have not yet been derived because sufficient data have not been available. In this study, we conducted multispecies toxicity tests, including acute assays using eight species from five different taxonomic groups (bacteria, algae, flagellates, crustaceans and fish) and chronic assays using six species from four different taxonomic groups (algae, flagellates, crustaceans and fish). Using the results of these assays, we used a SSD approach to derive an AgNP aquatic HC5 (Hazard concentrations at the 5% species) of 0.614 μg/L. To our knowledge, this is the first report of a proposed HC of AgNPs for the protection of aquatic ecosystems that is based on SSDs and uses chronic toxicity data.

Polystyrene nanoplastics inhibit reproduction and induce abnormal embryonic development in the freshwater crustacean Daphnia galeata

We assayed the toxicity of polystyrene nanoparticles (PS-NP, 52 nm) to Daphnia galeata. Survival and reproduction were significantly decreased in individuals exposed to 5 mg/L of PS-NP for 5 days, and embryos showed abnormal development, including a low hatching rate. Using fluorescence confocal microscopy, we recorded the transfer of PS-NP from the external surface of the body to the internal organs, including the thoracic appendices, ovaries, caudal appendices, and brood chamber, as well as PS-NP storage in lipid droplets. Although embryos were exposed to PS-NP in the brood chamber, they did not internalize PS-NP. Exposed D. galeata adults that were not pregnant stored significantly fewer lipid droplets than did the control group, and the lipid droplets that they did store were smaller; meanwhile, there were no significant changes in lipid storage in exposed pregnant individuals. Some embryos showed a high level of lipid storage, a response that occurs when embryos experience an abnormal state, and these embryos showed a very low hatching rate. However, the offspring of exposed adults showed normal survival and lipid storage. This study provides visual evidence that confirms the transfer and effects of PS-NP in Daphnia species, and suggests a relationship between toxicity and lipid storage.

Exoenzyme activity in contaminated soils before and after soil washing: ß-glucosidase activity as a biological indicator of soil health

It is essential to remediate or amend soils contaminated with various heavy metals or pollutants so that the soils may be used again safely. Verifying that the remediated or amended soils meet soil quality standards is an important part of the process. We estimated the activity levels of eight soil exoenzymes (acid phosphatase, arylsulfatase, catalase, dehydrogenase, fluorescein diacetate hydrolase, protease, urease, and ß-glucosidase) in contaminated and remediated soils from two sites near a non-ferrous metal smelter, using colorimetric and titrimetric determination methods. Our results provided the levels of activity of soil exoenzymes that indicate soil health. Most enzymes showed lower activity levels in remediated soils than in contaminated soils, with the exception of protease and urease, which showed higher activity after remediation in some soils, perhaps due to the limited nutrients available in remediated soils. Soil exoenzymes showed significantly higher activity in soils from one of the sites than from the other, due to improper conditions at the second site, including high pH, poor nutrient levels, and a high proportion of sand in the latter soil. Principal component analysis revealed that ß-glucosidase was the best indicator of soil ecosystem health, among the enzymes evaluated. We recommend using ß-glucosidase enzyme activity as a prior indicator in estimating soil ecosystem health.

Determination of the soil hazardous concentrations of bisphenol A using the species sensitivity approach

This study describes the determination of the species sensitivity distribution (SSD)-based soil hazardous contamination of bisphenol A for environmental risk assessment. We conducted a battery of bioassays, including acute assays using eight species from six different taxonomic groups and chronic assays using five species from four different taxonomic groups. We determined that our dataset satisfied Australia & New Zealands guidelines for applying the SSD methodology. Finally, the chronic soil HC5 and HC50 values for bisphenol A were estimated to be 13.7 and 74.7mg/kg soil, respectively, for soil ecosystem protection against chronic exposure using the data generated from this and previous studies. Because the soil standard values of bisphenol A for protection of the soil ecosystem are not currently available, the HC values of bisphenol A that we suggested based on the SSD approach would be applied as fundamental data to establish soil standards of bisphenol A for soil ecosystem protection. To our knowledge, this is the first study reporting the soil hazardous concentration of bisphenol A for environmental risk assessment.

In Situ Evaluation of Crop Productivity and Bioaccumulation of Heavy Metals in Paddy Soils after Remediation of Metal-Contaminated Soils

Soils contaminated with heavy metals have been reused for agricultural, building, and industrial uses following remediation. This study assesses plant growth and bioaccumulation of heavy metals following remediation of industrially contaminated soil. The soil was collected from a field site near a nonferrous smelter and was subjected to laboratory- and field-scale studies. Soil from the contaminated site was remediated by washing with acid or mixed with soil taken from a distant uncontaminated site. The activities of various soil exoenzymes, the rate of plant growth, and the bioaccumulations of six heavy metals were measured to assess the efficacy of these bioremediation techniques. Growth of rice (Oryza sativa) was unaffected in acid-washed soil or the amended soil compared to untreated soil from the contaminated site. The levels of heavy metals in the rice kernels remained within safe limits in treated and untreated soils. Rice, sorghum (Sorghum bicolor), and wheat (Triticum aestivum) cultivated in the same soils in the laboratory showed similar growth rates. Soil exoenzyme activities and crop productivity were not affected by soil treatment in field experiments. In conclusion, treatment of industrially contaminated soil by acid washing or amendment did not adversely affect plant productivity or lead to increased bioaccumulation of heavy metals in rice.

Species Sensitivity Distributions for Nonylphenol to Estimate Soil Hazardous Concentration

Nonylphenol is an endocrine-disrupting chemical that mimics estrogenic activity. Few studies have investigated the soil ecotoxicity of nonylphenol in the environment, based on probabilistic approaches. The present study generated soil toxicity data for nonylphenol through bioassays that determined the acute and chronic species sensitivity distributions and estimated the hazardous concentrations of nonylphenol in soil in order to protect soil ecosystems. We used eight soil-based organisms from six taxonomic groups for acute assays and five soil-based organisms from four taxonomic groups for chronic assays. The hazardous concentration values of nonylphenol in soil, based on acute and chronic species sensitivity distributions, were estimated using compiled data from the present study, as well as previous studies. This is the first study that generated sufficient data to develop species sensitivity distributions for nonylphenol in soil, and to determine hazardous concentrations of nonylphenol for soil environments.

Development of water quality criteria of ammonia for protecting aquatic life in freshwater using species sensitivity distribution method

Ammonia is deemed one of the most important pollutants in the freshwater environment because of its highly toxic nature and ubiquity in surface water. This study thus aims to derive the criteria for ammonia in freshwater to protect aquatic life because there are no water quality criteria for ammonia in Korea. Short-term lethal tests were conducted to perform the species sensitivity distribution (SSD) method. This method is widely used in ecological risk assessment to determine the chemical concentrations to protect aquatic species. Based on the species sensitivity distribution method using Korean indigenous aquatic biota, the hazardous concentration for 5% of biological species (HC5) value calculated in this study was 44mg/L as total ammonia nitrogen (TAN). The value of the assessment factor was set at 2. Consequently, the criteria for ammonia were derived as 22mg/L at pH7 and 20°C. When the derived value was applied to the monitoring data nationwide, 0.51%, 0.09%, 0.18%, 0.20%, and 0.35% of the monitoring sites in Han River, Nakdong River, Geum River, Youngsan River, and lakes throughout the nation, respectively, exceeded this criteria. The Ministry of Environment in Korea has been considering introducing water quality standard of ammonia for protecting aquatic life. Therefore, our results can provide the basis for introducing the ammonia standard in Korea.

Characteristics and Toxicity Sensitivity of Korean Dominant Species Daphnia galeata for Ecotoxicity Testing: Comparative Study with Daphnia magna

Water flea is a widely used test species in the aquatic ecotoxicity test. In Korea, D. magna is currently used as a standard test species, however that do not inhabit in the Korean aquatic ecosystem. In this study, Daphnia galeata, which is a dominant species in the Korean aquatic ecosystem, was collected from domestic lake and investigated to suggest the D. galeata for ecotoxicity assessment in Korea. We investigated the characteristics, life span, and toxicity sensitivity compared with D. magna. The life span test of D. galeata was performed in this study, and then the results were compared to the sensitivity with D. magna to confirm the applicability for ecotoxicity assessment. The 48h-L(E)C50 values for seven heavy metals (As, Cd, Cr, Cu, Hg, Ni, and Zn) of D. galeata and D. magna were collected and analyzed. As a results, shorter lifetime, less reproduction, smaller body size of D. galeata were observed compared with D. magna. D. galeata was similar or more sensitive than D. magna for seven heavy metals. Therefore, we propose that D. galeata is a suitable test species for ecotoxicity testing in Korea.

Soil ecotoxicity study of DEHP with respect to multiple soil species

Di (2-ethylhexyl) phthalate or DEHP is classified as an endocrine-disrupting chemical. It is used as a plasticizer and pesticide additive. Moreover, it has a half-life of about 150-300 days. Thus, it is present in the soil environment and soil risk assessments for DEHP are needed. However, a number of studies have focused on the effects of DEHP in a single soil species. In this study, we conducted acute and chronic toxicity testing for DEHP using varied soil species, including plants, earthworms, soil algae, Collembola, and soil nematodes. In the plant toxicity test, no effect was observed at very high concentration except at some endpoints, and no effect was observed in the earthworm toxicity test. However, there were adverse effects on soil algae, Collembola, and nematodes. Notably, in the Collembola assays, the survival of adults decreased significantly at very high concentrations, whereas reproduction was hindered at low concentrations. Similar inhibition of reproduction was noted in the soil nematode assay. This suggests that DEHP has a greater influence on fertility than survival in the adult test species. However, besides hindered reproduction, no effect was observed on soil species at environmentally relevant concentrations.

Ecological hazard assessment of methyl ethyl ketone using the species sensitivity distribution approach in a soil ecosystem

Methyl ethyl ketone (MEK) is a common and widely used industrial solvent. However, few studies have investigated its toxicity, or its effects as a contaminant in soil ecosystems. In this study, acute and chronic toxicity data for MEK were generated, and ecological risk based on a species sensitivity distribution was assessed. Seven soil organisms from six taxonomic groups were used for acute toxicity tests and five soil organisms from four taxonomic groups were used for chronic toxicity tests. Acute and chronic soil HC5 (hazardous concentration for 5% of species) values for MEK were estimated as 53.04 and 2.593 mg MEK/kg dry soil, respectively. This is the first study to conduct battery testing for MEK; it specifies hazardous concentrations, warns of the need for accident preparedness, and points to serious potential hazards of MEK at various levels of the soil ecosystem which can translate into greater environmental damage with implications for human health. The specific sensitivity levels determined may serve as a benchmark for establishing soil standards and strategies for ecosystem protection in the face of accidental contamination.