RESUMEN
This study aimed to establish ecotoxicologically acceptable Cu concentrations for soil-residing species by integrating the biotic ligand model and the species sensitivity distribution. Statistical analyses were performed on 35 soil solution samples collected from four distinct land use sites: residential, agricultural, forested, and industrial regions. The environmental parameters of these samples, including pH, dissolved organic carbon (DOC), Ca2âº, Mg2âº, Kâº, and Na⺠concentrations, exhibited wide variations across the four regions. Specifically, pH and the concentrations of Mg2âº, Kâº, and Na⺠showed significant variability. Additionally, a strong correlation was observed between pH and Ca2âº, as well as between the DOC concentration and Mg2⺠and Naâº. Using the biotic ligand model, we derived the half-maximal effective activities of Cu (EC50{Cu2+}) for 10 soil organisms based on the chemical compositions of the soil solution samples. Additionally, a species sensitivity distribution approach was employed to determine the 5% hazardous concentration (HC5) for soil biota, which was closely associated with DOC and Na⺠concentrations, with Mg2⺠playing a secondary role. We attributed these relationships to the formation of DOC complexes that mitigate Cu toxicity, along with competitive interactions with cations. Notably, HC5 values did not differ significantly across sampling sites (p = 0.523). Clustering based on environmental factors grouped the samples into four clusters, each containing soils from different land use types. However, the third cluster included an outlier from agricultural soil due to its unusually high pH and DOC levels. These findings suggest that it is crucial to consider site-specific soil characteristics when determining ecotoxicologically acceptable Cu concentrations, and soil solution characteristics do not always align with specific land use patterns.
Asunto(s)
Cobre , Ecotoxicología , Monitoreo del Ambiente , Contaminantes del Suelo , Suelo , Contaminantes del Suelo/análisis , Cobre/análisis , Suelo/química , República de Corea , Monitoreo del Ambiente/métodos , AgriculturaRESUMEN
The biotic ligand model (BLM) was applied to derive ecotoxicologically acceptable Cu concentrations at 12 monitoring stations in the Han River Basin, South Korea, considering temporal variations in water characteristics. During the monitoring period, pH, dissolved organic carbon (DOC), and water temperature varied instantaneously, resulting in spatiotemporal variations in the half-maximal effective concentrations (EC50[Cu]T) of Daphnia magna. The effect of dissolved Ca2+ concentration was evaluated to determinate EC50[Cu]T using the Visual MINTEQ 3.1 speciation model. Dissolved Ca2+ concentration was directly proportional to EC50[Cu]T values, indicating that a higher Ca2+ in the solution will result in the lesser toxic effects on D. magna due to the competition between Ca2+ and Cu2+ ions. The Ca2+ concentration was set at 0.4 mM while deriving EC50[Cu]T, which is the geometric mean concentration in the Han River Basin. The lower confidence limit (LCL) of EC50[Cu]T was 28.7-67.8 µg/L in the monitoring stations. Among the water characteristics, DOC was more strongly positively correlated with EC50[Cu]T than that with pH and temperature. DOC concentration was significantly related to Cu2+ activity, pH was less explicitly related to EC50[Cu]T than to DOC, and water temperature had the weakest correlation coefficient. Compared to the 5% hazardous concentration (HC5) derived from the toxicity data for 171 aquatic species and Cu criteria in different countries, the computed LCL concentrations had similar orders of magnitude. With more information on actual Ca2+ concentrations at monitoring sites, a more accurate Cu concentration that reflects spatiotemporal variations of water characteristics can be obtained.
Asunto(s)
Ríos , Contaminantes Químicos del Agua , Animales , Cobre/análisis , Daphnia , Concentración de Iones de Hidrógeno , Ligandos , Agua , Contaminantes Químicos del Agua/análisisRESUMEN
Biotic ligand model (BLM) was extended to predict the toxicity of inorganic arsenate (iAs(V)) to the luminescent bacteria, Aliivibrio fischeri. As the pH increased from 5 to 9, the HAsO42- form predominated more than the H2AsO4- form did, and the EC50[As]T (50% effective iAs(V) concentration) decreased drastically from 3554⯱â¯393 to 39⯱â¯6⯵M; thus, the HAsO42- form was more toxic to A. fischeri than H2AsO4-. As the HPO42- activity increased from 0 to 0.44â¯mM, the EC50{HAsO42-} values (50% effective HAsO42- activity) increased from 31⯱â¯6 to 859⯱â¯128⯵M, indicating that the toxicity of iAs(V) decreased, owing to the competition caused by the structural similarity between iAs(V) and phosphate ions. However, activities of Ca2+, Mg2+, K+, SO42-, NO3-, and HCO3- did not significantly affect the EC50{HAsO42-} values. The BLM was reconstructed to take into account the effects of pH and phosphate, and the conditional binding constants for H2PO4-, HPO42-, H2AsO4-, and HAsO42- to the active binding sites of A. fischeri were obtained; 3.424 for logKXH2PO4, 4.588 for logKXHPO4, 3.067 for logKXH2AsO4, and 4.802 for logKXHAsO4. The fraction of active binding sites occupied by iAs(V) to induce 50% toxicity (fmix50%) was found to be 0.616.
Asunto(s)
Arseniatos/toxicidad , Concentración de Iones de Hidrógeno , Modelos Biológicos , Modelos Químicos , Fosfatos/química , Contaminantes del Suelo/toxicidad , Aliivibrio fischeri/efectos de los fármacos , LigandosRESUMEN
The effectiveness of in situ stabilization in the long-term As-contaminated soil was assessed. In situ stabilization of As was conducted through a Fe-based sorbent amendment. Chemical extractability of As was first determined by solubility/bioavailability research consortium extraction method and any change in human health risk through oral ingestion was characterized. Also, nonspecifically bound As in soil was determined by five-step sequential extraction. The results indicate that such extractable fractions of As decreased, and consequently risk through oral ingestion decreased probably due to hematite transformed from both the goethite in the original soil and the Fe-based sorbent, which was identified through the X-ray absorption spectroscopy. In ecotoxicity test with Hordeum vulgare, root and shoot elongation and germination rate decreased which was contrary to the chemical extraction data. Such increase in As toxicity is because of increased exchangeable Ca2+ concentration causing As accumulation in the membrane surface of H. vulgare. Also, adsorption of phosphorus onto the Fe-based sorbent decreased available phosphorus concentration causing phosphorus deficiency for growth. Our results demonstrate that the effectiveness of in situ stabilization should be evaluated by means of both chemical extractability and biological response, as chemical analysis alone may not be sufficient to assess the ecotoxicity.