Bioavailability of Apparent Fulvic Acid Complexed Copper to Fish Gills

Received: 25 February 1999/Accepted: 16 November 1999     

Bioavailability of Copper and Zinc in Mining Soils

The soil-contact exposure pathway can be the main driver of ecological risk assessments. There is currently no standard method to measure bioavailability of metals in soil to ecological receptors, yet the influence of metal bioavailability on toxicity has been known for decades and is a major factor influencing risk to ecological receptors. Bioavailability is to a large degree governed by varying soil characteristics within and among sites, yet ecological screening benchmarks are often derived on a total-concentration basis. We compared a calcium chloride (CaCl₂) extraction, cyclodextrin extraction, simulated earthworm gut (SEG) test, earthworm kinetic bioaccumulation test, and metal residues in plant tissues with a battery of invertebrate and toxicity tests using mining soils consisting of high organic-matter content cocontaminated with copper (Cu) and zinc (Zn). Earthworm (Eisenia andrei) tissue concentrations of Cu and Zn were regulated and were not predictive of invertebrate toxicity. All chemical measures of bioavailability correlated with several biological responses; however, CaCl₂-extractable Cu and SEG-extractable Cu and Zn best predicted effects to E. andrei. Total Cu concentrations in soil best correlated with effects to plants. Overall, a chemical measure was the best predictor of toxicity to each organism compared with biological measures, although the exact measure was dependent on organism and end point. Chemical-extraction techniques provide relatively quick, inexpensive indicators of essential metal bioavailability compared with biological measures; however, no single measure was indicative of all effects to all organisms.     

Toxicity and Bioavailability of Copper Herbicides (Clearigate, Cutrine-Plus, and Copper Sulfate) to Freshwater Animals

In designing aquatic herbicides containing copper, an important goal is to maximize efficacy for target species while minimizing risks for nontarget species. To have a margin of safety for nontarget species, the concentration, duration of exposure (i.e., uptake), and form (i.e., species) of copper used for herbicidal properties should not elicit adverse effects on populations of nontarget species. To determine the potential for risk or adverse effects (conversely the margin of safety), data regarding the comparative toxicity of copper-containing herbicides are crucial. A series of comparative toxicity experiments was conducted, including baseline estimates of toxicity (LC50s, LOECs), sensitive species relationships (thresholds and exposure-response slopes), and bioavailability of toxic concentrations and forms of copper 7 days after initial herbicide application. Aqueous 48-h toxicity experiments were performed to contrast responses of Daphnia magna Strauss, Hyalella azteca Saussure, Chironomus tentans Fabricius, and Pimephales promelas Rafinesque to copper herbicides: Clearigate(R), Cutrine(R)-Plus, and copper sulfate. D. magna was the most sensitive aquatic animal tested for all three herbicides; 48-h LC50s for organisms exposed to Clearigate, Cutrine-Plus, and copper sulfate were 29.4, 11.3, and 18. 9 microg Cu/L, respectively. In terms of potency (calculated from the linearized portion of the exposure-response curves, which included 50% mortality), D. magna was the most sensitive animal tested. Organisms exposed to Clearigate, Cutrine-Plus, and copper sulfate had exposure-response slopes of 2.55, 8.61, and 5.07% mortality/microg Cu/L, respectively. Bioavailability of Clearigate and Cutrine-Plus was determined by comparing survival data (LC50s) of test organisms exposed to herbicide concentrations during the first and last 48-h of a 7-day exposure period. Even in these relatively simplified water-only exposures, a transformation of copper to less bioavailable species over time was observed with a 100-200% decrease in toxicity (i.e., an increase in 48-h LC50s) for all four test animals. This series of laboratory experiments provides a worst-case scenario for determining the risk associated with the manufacturer's recommended application rates of Clearigate (100-1,000 microg Cu/L), Cutrine-Plus (200-1,000 microg Cu/L), and copper sulfate (100-500 microg Cu/L) in natural waters for four nontarget freshwater animals.     

Copper Speciation and Microbial Activity in Long-Term Contaminated Soils

Most soil quality guidelines do not distinguish among the various forms of metals in soils; insoluble, nonreactive, and nonbioavailable forms are deemed as hazardous as highly soluble, reactive, and toxic forms. The objective of this study was to better understand the long-term effects of copper on microorganisms in relation to its chemical speciation in the soil environment. Carbon mineralization processes and the global structure of different microbial communities (fungi, eubacteria, actinomycetes) are still affected after more than 50 years of copper contamination in 20 soils sampled from two different agricultural sites. The microbial respiration lag period (LP) preceding the beginning of mineralization process increases with the level of soil copper contamination and is not significantly affected by other environmental factors such as soil pH and soil organic matter (SOM) content. The total copper concentration showed the best correlation with the LP when each site is considered separately. However, when considering the whole set of data, soil solution free Cu²⁺ activity (pCu²⁺) is the best predictor of Cu toxicity determined by LP (quite likely because pCu²⁺ integrates the soil physicochemical variability). The maximum mineralization rate (MMR), even if well correlated with the pCu²⁺, appears not to be a good biomonitor of copper contamination in soils since it is highly sensitive to soil characteristics such as SOM content. This study emphasizes the importance of the physicochemical properties of the environment on soil heavy metal toxicity and on soil toxicological measurements. These properties must be characterized in soil toxicological studies with respect to (1) their interactions with heavy metals, and (2) their direct impact on the selected biological test. The measurement of pCu²⁺ to characterize the level of soil contamination and of lag period as a bioindicator of metal effects in the soil are recognized as useful tools for the evaluation of the biological quality of soils. Received: 30 May 1998/Accepted: 14 September 1998     

Speciation and Size Distribution of Copper and Zinc in Urban Road Runoff

The impact of pollutants from road runoff on receiving water bodies becomes increasingly serious. However, less is known about the study on the distribution of metal speciation in particles with different sizes, and the interaction among metal speciation. Our research is aimed at investigating speciation distribution of copper (Cu) and zinc (Zn) in particles and the interaction among metal speciation. Stainless steel sieves in different sizes were used to accomplish filtration scheme. Sequential extraction procedures contained five steps for the chemical fractionation of metals. Flame atomic absorption spectrometry (Shimadzu, AA-6800) was used to determine the concentration of metal speciation. Speciation distribution of Cu was similar to that of Zn. Size distribution implied that small particles (<75 μm) determined the distribution for both Cu and Zn, as well as their migration. Correlation analysis indicated that the interaction among speciation of Cu was different from that of Zn.     

Sensitivity to Copper in a Ciliate as a Possible Component of Biological Monitoring in the Lagoon of Venice

The impact of copper was studied in cultures of the microbenthic organism Euplotes vannus (Ciliophora, Hypotrichida). This ciliate was isolated from sediment collected from a particular area in the Lagoon of Venice, which may be considered almost unpolluted by heavy metals. The effects of copper exposure in the laboratory on growth, metal accumulation, total acid-soluble thiol levels, and glutathione levels were examined, together with morphological alterations. E. vannus exhibited tolerance toward copper up to a concentration exposure of 0.2 μg Cu/ml, at which cell growth rate overlapped that of controls. Copper accumulated up to 239 μg/g dry wt after exposure to 0.4 μg Cu/ml, and morphological alterations were evident in cells exposed to concentrations from this value upward. Processes of vegetative reorganization involving nuclear apparatus, membranelles, cirri, and cortex could be observed after 4 days of exposure to 0.4 μg Cu/ml. Laboratory experiments with cultures of ciliates of cosmopolitan distribution such as Euplotes species in controlled conditions indicated the value of these organisms, which constitute a simple model for a monitoring system suitable for prediction in multicellular organisms. Received: 25 August 1997/Accepted: 10 March 1998     

Bioavailability and Speciation of Heavy Metals in Polluted Soil as Alleviated by Different Types of Biochars

Bulletin of Environmental Contamination and Toxicology - Biochar is an important material for remediation of contaminated soils, however, different biochars have variable effects on bioavailability...     

Toxicity and Bioaccumulation of Copper to Black Bindweed (Fallopia convolvulus) in Relation to Bioavailability and the Age of Soil Contamination

The use of ecotoxicity test results obtained in the laboratory for prediction of effects of potentially toxic concentrations of chemicals in the field is hampered by several factors differing between the laboratory and the field situations. One important factor is the binding of test chemicals to soil, which is affected by the age of the contamination and soil type. The present study investigated the effect of contamination age by introducing an aging period of 1 to 12 weeks between mixing the test substance, copper sulfate, in with soil and introducing the test plant, Fallopia convolvulus (L.) A. Löve. Copper accumulation, emergence of cotyledons, and growth were assessed and related to total (boiling with HNO₃) and 0.01 M CaCl₂- and DTPA-extractable soil copper concentrations. Aging of the copper-contaminated soil had only small effects on bioaccumulation of copper, copper toxicity, and extractable soil copper fractions. Soil copper had no effect on emergence of cotyledons. Estimated EC₅₀ values for shoot and root growth averaged 280 mg Cu/kg. Effects on growth in these laboratory-treated soils were much more severe than in a study performed in soil from an old copper-contaminated field site. Neither CaCl₂- nor DTPA-extractable copper fractions could explain all of the differences in effects between aged spiked soil and field soil. The accumulation pattern for roots and shoots of F. convolvulus indicated that excessive copper was accumulated and adsorbed mainly by the fine roots, whereby the copper concentrations of other plant parts were kept low until the plant was no longer able to maintain this regulation. An internal threshold for effects on growth of about 20 mg Cu/kg shoot dry weight was estimated, coinciding with a soil copper concentration of approximately 200 mg/kg.     

Testing the Underlying Chemical Principles of the Biotic Ligand Model (BLM) to Marine Copper Systems: Measuring Copper Speciation Using Fluorescence Quenching

Speciation of copper in marine systems strongly influences the ability of copper to cause toxicity. Natural organic matter (NOM) contains many binding sites which provides a protective effect on copper toxicity. The purpose of this study was to characterize copper binding with NOM using fluorescence quenching techniques. Fluorescence quenching of NOM with copper was performed on nine sea water samples. The resulting stability constants and binding capacities were consistent with literature values of marine NOM, showing strong binding with \(\log K\) values from 7.64 to 10.2 and binding capacities ranging from 15 to 3110 nmol mg \({\text {C}}^{-1}.\) Free copper concentrations estimated at total dissolved copper concentrations corresponding to previously published rotifer effect concentrations, in the same nine samples, were statistically the same as the range of free copper calculated for the effect concentration in NOM-free artificial seawater. These data confirms the applicability of fluorescence spectroscopy techniques for NOM and copper speciation characterization in sea water and demonstrates that such measured speciation is consistent with the chemical principles underlying the biotic ligand model approach for bioavailability-based metals risk assessment.     

QSARs for the Chronic Toxicity of Halogenated Benzenes to Bacteria in Natural Waters

No abstract available.     

Copper Bioavailability and Fractionation in Copper-Contaminated Sandy Soils in the Wet Subtropics (Southern Brazil)

We studied the distribution, bioavailability and speciation of copper in subtropical sandy soils exposed to long-term applications of copper-based fungicide. In the surface horizon of the contaminated soils, bioavailable copper surpasses the toxic threshold for plants up to several times. Mobile fractions of copper predominate in top layers, contributing to contamination spreading downward to groundwater. Copper accumulates on the underlying iron hydroxide barrier in quantities comparable to total copper concentrations in the surface horizon. Despite the impediment of the geochemical barrier, most applied copper reaches the aquifer, contaminating the groundwater.     

Speciation and Bioavailability of Metals in Sediments from a Stream Impacted by Abandoned Mines in Maoshi Town,Southwest of China

Bulletin of Environmental Contamination and Toxicology - The speciation of metals in surface sediments, as well as metal concentrations in muscle and liver of sharpbelly Hemiculter leucisculus from...     

Effect of Natural Dissolved Humic Material on Bioavailability and Acute Toxicity of Fenpropathrin to the Grass Carp,Ctenopharyngodon idellus

The effects of aquatic humic acids on the bioconcentration and acute toxicity of fenpropathrin were evaluated using grass carp,Ctenopharyngodon idellus, in laboratory freshwater systems. The results demonstrated that both bioavailability and acute toxicity decreased in the presence of aquatic humic acid 5 and 10 mg/liter. In addition, the extent of influence increased with increasing concentration of aquatic humic acid.     

Bioavailability of cyanide and metal-cyanide mixtures to aquatic life

Cyanide can be toxic to aquatic organisms, and the U.S. Environmental Protection Agency has developed ambient water-quality criteria to protect aquatic life. Recent work suggests that considering free, rather than total, cyanide provides a more accurate measure of the biological effects of cyanides and provides a basis for water-quality criteria. Aquatic organisms are sensitive to free cyanide, although certain metals can form stable complexes and reduce the amount of free cyanide. As a result, total cyanide is less toxic when complexing metals are present. Cyanide is often present in complex effluents, which requires understanding how other components within these complex effluents can affect cyanide speciation and bioavailability. The authors have developed a model to predict the aqueous speciation of cyanide and have shown that this model can predict the toxicity of metal-cyanide complexes in terms of free cyanide in solutions with varying water chemistry. Toxicity endpoints based on total cyanide ranged over several orders of magnitude for various metal-cyanide mixtures. However, predicted free cyanide concentrations among these same tests described the observed toxicity data to within a factor of 2. Aquatic toxicity can be well-described using free cyanide, and under certain conditions the toxicity was jointly described by free cyanide and elevated levels of bioavailable metals.     

Lack of Evidence for Metallothionein Role in Tolerance to Copper by Natural Populations of Daphnia longispina

No abstract available.     

Effects of Soil Amendments on the Extractability and Speciation of Cadmium,Lead, and Copper in a Contaminated Soil

The effects of chemical amendments including zeolite, compost and mesoporous molecular sieves (MCM-41) on the extractability and speciation of heavy metals (Cd, Pb and Cu) in a contaminated soil were investigated. Results showed that the application of soil amendments decreased Cd, Pb and Cu uptake by the shoots of pakchoi, up to 44.2–53.2%, 30.2–42.7% and 16.9–22.1%, respectively, compared with the control. Among the three amendments, zeolite and MCM-41 were more efficient in reducing Cd and Cu uptake, while compost was more efficient in reducing Pb uptake by the plants. The growth of pakchoi was improved in amended soils due to the action of chemical amendments.     

Copper Speciation and Accumulation in the Gill Microenvironment of Carp (Cyprinus carpio) in the Presence of Kaolin Particles

Carp were exposed to copper adsorbed on kaolin particles at various concentrations (0–2.4 mg/L), and net accumulation due to elevated adsorbed copper in the surrounding water was observed. Copper speciation in the water and fish gill microenvironment was modeled in the presence and absence of kaolin using a chemical speciation program (MINTEQA2). The adsorption affinity constants of kaolin for copper at various pH values used in the speciation calculations were experimentally determined, and the quantitative relationship between the affinity constant and pH was modeled. Copper accumulations in fish gills exposed to kaolin-adsorbed copper was then observed. The results indicate that desorption occurred in the fish gill microenvironment due to both mucus competition of copper and slight increase in water pH. Furthermore, the available copper species increased as a result of desorption, causing a net accumulation of Cu by the gills. Received: 15 June 2001/Accepted: 2 November 2001