Sorption of Cu(II) onto vineyard soils: Macroscopic and spectroscopic investigations

Application of X-ray based modern instrumental techniques to determine the heavy metals in soils, minerals and organic media

To evaluate the environmental concerns associated with heavy metals (HMs) during their translocations in food chains, it is crucial to gather data on the types of HMs present in soils in order to ascertain their toxicity and potential to migrate. An overview of the findings from several physical techniques used to determine and identify the HMs, sediments, individual minerals, and organic components in contaminated agricultural and industrial soils, is provided in this review article. These studies cover a variety of X-ray-based analytical techniques, including most widely used ones like X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray diffraction, and less popular ones X-ray fluorescence, etc. When compared to techniques that rely on laboratory radiation sources, synchrotron radiation offers more precision and efficiency. These methods could pinpoint the primary mechanisms influencing the soil's ability to transport contaminants and track their subsequent migration up the food chain.

Copper (Cu) speciation in organic-waste (OW) amended soil: Instability of OW-borne Cu(I) sulfide and role of clay and iron oxide minerals

The geochemistry of copper (Cu) is generally assumed to be controlled by organic matter in soils. However, the role of clay and iron oxide minerals may be understated. Soil density fractionation, X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS) were combined to assess the long-term behavior of Cu in an agricultural soil subject to organic waste application. Two unprecedented molecular environments of natural Cu (i.e. Cu inherited from the parent rock) in soils are reported: Cu dimer in the interlayer of vermiculite and Cu structurally incorporated within hematite. Moreover, the soil naturally containing Cu-vermiculite, Cu-hematite, but also Cu-kaolinite (Cu_total = 122 mg·kg^-1) was amended over 11 years with Cu-rich pig slurry in which Cu was 100 % Cu(I) sulfide. Natural Cu associated with clay and iron oxide minerals persisted in the amended soil, but the exogenous Cu(I) sulfide was unstable. The increase in Cu concentration in the amended soil to 174 mg·kg^-1 was accounted for the increase of Cu sorbed to kaolinite and Cu bound to organic matter. These results are important for better understanding the natural occurrence of Cu in soils and for assessing the environmental impacts of organic waste recycling in agricultural fields.

Relationship of Selected Soil Properties with the Micronutrients in Salt-Affected Soils

The present study aimed to assess the relationship of soil properties in salt-affected soils. The soil samples were collected from 14 districts of Pakistan. Soil salinity and sodicity are the common features of the arid and semiarid regions. The effects of the salt’s interactions with soil micronutrients have not been well studied. Therefore, saline and non-saline soil samples were collected from different locations. The microelements (Fe, Cu, Mn, and Zn) were fractionated into water-soluble, exchangeable, carbonate, Fe + Mn oxide, organic, and residual fractions. Univariate and multivariate analysis (PCA) was carried out to determine the linear relationship between soil properties and micronutrients fractions. Results showed that the magnitude of micronutrients appeared to be affected by the salinity in soils. In saline soil, the Fe fractions differed in the order of residual > organic bound > Fe + Mn bound > carbonate bound > exchangeable > water soluble. Iron fractions varied in the non-saline soils as residual > Fe + Mn bound > organic bound > exchangeable > carbonate bound > water soluble. Copper concentration was higher in the residual and carbonate forms, and the amount was lower in the exchangeable and water-soluble forms under both saline and non-saline conditions. The water-soluble Mn fraction was lower, and the residual Mn fraction was proportionately higher than other forms of Mn in soils. Zinc was found mostly in the residual fraction in both saline and non-saline soils. The mobility factor of micronutrients in non-saline soil was greater than in saline soil. PCA revealed that organic matter (OM) and pH directly affected the fractionation of Cu, Mn, Zn, and Fe in soil. Thus, it could be inferred that salts can bring changes to the composition of micronutrients depending on the nature of the soil and the magnitude of salts.

NOM-mineral interaction: Significance for speciation of cations and anions

In this study, the nano-scale spatial distribution of natural organic matter (NOM) on the surface of iron (hydr)oxides and its relevance to oxyanion (PO₄^3-) and metal cation (Cd²⁺ and Cu²⁺) adsorption to the assemblage of oxide (goethite) and NOM (humic acids (HA) or fulvic acids (FA)) was investigated with experiments and advanced surface complexation modeling. Both the linear additive Multi-Surface model (MSM) and the more sophisticated Natural Organic Matter-Charge Distribution (NOM-CD) model were used. The MSM model ignores the effects of NOM-mineral interaction on ion adsorption, whereas the NOM-CD model considers this effect. The results showed that with the increase of NOM loading on oxides, deviation between the MSM and NOM-CD model became bigger for PO₄^3-, but smaller for Cd²⁺ and Cu²⁺. Oxyanions bind mainly to oxides and therefore the competitive effect of NOM cannot be neglected, which explains the large difference between these two models for PO₄^3-. On the contrary, at a relatively high NOM loading, a large fraction of NOM extends further away from the surface of oxides. Thus for metal cations that bind mainly to NOM, the influence of NOM-mineral interaction on their adsorption is small and the results of the MSM and NOM-CD model are similar. In top soils, the NOM loading on oxides is often high, therefore the linear additive MSM is applicable for metal cation speciation calculations as reported in many literatures. An approach based on the NOM-CD model was proposed, which can not only calculate the macroscopic solid-solution distribution of both cations and anions, but can also provide information regarding their microscopic surface speciation.

Assessment of Copper and Heavy Metals in Family-Run Vineyard Soils and Wines of Campania Region, South Italy

Copper-based phytosanitary treatments are widely employed in viticulture for combating the fungal diseases of European grape (Vitis vinifera L.). Herein we evaluated copper accumulation in the soil of a 50-year-old still productive vineyard in South Italy in comparison with samples taken from a ‘control’ area in which grapevines had never been cultivated, as well from an abandoned vineyard, now planted with cereals and forage crops, both close to the main area under investigation. Even though the heavy metal contents detected were not of concern for soils nor for wine, Cu accumulates in the soil in amounts significantly higher than the (grapevine free) control and remains at detectable concentrations also in abandoned vineyards where spraying activities had ceased about 20 years before this study. Despite the long Cu residence times in soil, the wine produced with grapes of the same vineyard showed Cu levels low enough to be safely used for human consumption, probably due to mechanisms of metal precipitation occurring during wine maturation, which are typically accompanied by sedimentation processes in artisanal production. However, this should not diminish the urgency of decreasing the copper usage as antifungal remedy in viticulture to prevent copper contamination of the agricultural soils.

Response of wheat, pea, and canola to micronutrient fertilization on five contrasting prairie soils

A polyhouse study was conducted to evaluate the relative effectiveness of different micronutrient fertilizer formulation and application methods on wheat, pea and canola, as indicated by yield response and fate of micronutrients in contrasting mineral soils. The underlying factors controlling micronutrient bioavailability in a soil-plant system were examined using chemical and spectroscopic speciation techniques. Application of Cu significantly improved grain and straw biomass yields of wheat on two of the five soils (Ukalta and Sceptre), of which the Ukalta soil was critically Cu deficient according to soil extraction with DTPA. The deficiency problem was corrected by either soil or foliar application of Cu fertilizers. There were no significant yield responses of pea to Zn fertilization on any of the five soils. For canola, soil placement of boric acid was effective in correcting the deficiency problem in Whitefox soil, while foliar application was not. Soil extractable Cu, Zn, and B concentration in post-harvest soils were increased with soil placement of fertilizers, indicating that following crops in rotation could benefit from this application method. The chemical and XANES spectroscopic speciation indicates that carbonate associated is the dominant form of Cu and Zn in prairie soils, where chemisorption to carbonates is likely the major process that determines the fate of added Cu and Zn fertilizer.

Role of water chemistry on stability, aggregation, and dissolution of uncoated and carbon-coated copper nanoparticles

Intentional or accidental release of copper nanoparticles (Cu-NPs) from consumer products during manufacturing, use, and end-of-life management could pose health and ecological risks. This paper presents a detailed study on the role of water chemistry on the fate of uncoated and carbon-coated Cu-NPs dispersed in aqueous cetyltrimethylammonium bromide (CTAB) surfactant in the presence and absence of humic acids (HAs). A range of water chemistry and HAs had minimum impact on hydrodynamic diameter and zeta-potential values of uncoated and carbon-coated Cu-NPs. The water pH significantly (p < 0.001) affected the aggregation of uncoated Cu-NPs unlike that of carbon-coated Cu-NPs; however, the presence of HAs increased the stability of uncoated Cu-NPs. Although CTAB is considered as an efficient dispersant to stabilize Cu-NPs, the effect descended with time for uncoated Cu-NPs. The dissolution of Cu over time decreased with increasing pH for both uncoated (0.5-50% weight) and carbon-coated (0.5-40% weight) Cu-NPs. However, carbon-coated Cu-NPs exhibited significant dissolution (p < 0.001) at neutral pH than uncoated Cu-NPs may be due to the additional carbon it acquired during coating. Increasing HAs concentration from 0 to 15 mg L^-1 at pH 5.5 inhibited aggregations but enhanced dissolution of the uncoated and carbon-coated Cu-NPs. These findings inform risk analysis of Cu-NPs including how Cu-NPs fate, mobility and bioavailability are modulated by particles coating and dispersant, HAs presence, water chemistry and exposure time in dispersion media.

Characterization of colloid-size copper-based pesticide and its potential ecological implications

The intensive use of Cu-based pesticides in agriculture could have an unintended impact on the ecosystems and human health via different exposure pathways. This paper presents the results of experiments involving colloidal stability, aggregation, and dissolution of Cu₂O commercial pesticide under various environmental conditions in view of ecological implications. The investigated pesticide contains ∼750 g kg^-1 Cu (75% weight of product), Cu₂O particles with sizes < 1 μm, and nominal size fraction of Cu₂O nanoparticles. The co-presence of Ca²⁺ (20 mM) and humic acid (HA, 15 mg L^-1) significantly modulates (p < 0.001) the colloidal stability and mobility of particles. The dissolution of Cu at pH 5.5 was about 85%, 90%, and 75% weight more than the dissolution of Cu at pH 7.0, pH 8.5, and pH 7.0 and pH 8.5 combined, respectively in all dispersions. However, increasing HA content from 0 to 15 mg L^-1 reduced the dissolution of Cu by 56%, 50%, and 40% weight at pH 5.5, 7.0, and 8.5, respectively. Thus, pH below 7.0 is a critical factor to control the dissolution and bioavailability of Cu that may pose ecotoxicity and environmental pollution, whereas pH above 7.0 and the presence of HA attenuate the pH effect. These findings provide insight into how the potential mobility and bioavailability of Cu is modulated by the water chemistry under various environmental scenarios and media.

Adsorption behaviors of fungicide-derived copper onto various size fractions of aggregates from orchard soil

Although the gradual accumulations of Cu in orchard soils due to the application of Cu-based fungicides have been widely reported, limited information is available about the retention characteristics of fungicide-derived Cu in soil, especially in various size soil aggregates. This study described the adsorption characteristics of Cu from commonly used fungicide, Bordeaux mixture (CuSO₄ + Ca(OH)₂), onto various aggregate fractions (2000-1000, 1000-500, 500-250, 250-106, and <106 μm) of orchard soil. The Cu(NO₃)₂ was selected as a comparison. Two different types of adsorption experiments were conducted as follows: variable pH and variable Cu concentration experiments. The adsorption processes of Bordeaux mixture and Cu(NO₃)₂ onto the studied soil samples followed well with the Freundlich isotherm, and the adsorption isotherms were the S shaped. The adsorption amounts of Cu from different Cu compounds differed, and Bordeaux mixture can result in more Cu retention in soil than Cu(NO₃)₂. The adsorption ability of different size soil aggregates varied, and it was mainly governed by soil properties. The findings of this study suggested that both the chemical compositions of Cu compounds and the soil physical structure should be taken into account when performing soil Cu retention experiments with fungicide-derived Cu.

Chemical and structural characterization of copper adsorbed on mosses (Bryophyta)

The adsorption of copper on passive biomonitors (devitalized mosses Hypnum sp., Sphagnum denticulatum, Pseudoscleropodium purum and Brachythecium rutabulum) was studied under different experimental conditions such as a function of pH and Cu concentration in solution. Cu assimilation by living Physcomitrella patents was also investigated. Molecular structure of surface adsorbed and incorporated Cu was studied by X-ray Absorption Spectroscopy (XAS). Devitalized mosses exhibited the universal adsorption pattern of Cu as a function of pH, with a total binding sites number 0.05-0.06 mmolg(dry)(-1) and a maximal adsorption capacity of 0.93-1.25 mmolg(dry)(-1) for these devitalized species. The Extended X-ray Absorption Fine Structure (EXAFS) fit of the first neighbor demonstrated that for all studied mosses there are ∼4.5 O/N atoms around Cu at ∼1.95 Å likely in a pseudo-square geometry. The X-ray Absorption Near Edge Structure (XANES) analysis demonstrated that Cu(II)-cellulose (representing carboxylate groups) and Cu(II)-phosphate are the main moss surface binding moieties, and the percentage of these sites varies as a function of solution pH. P. patens exposed during one month to Cu(2+) yielded ∼20% of Cu(I) in the form of Cu-S(CN) complexes, suggesting metabolically-controlled reduction of adsorbed and assimilated Cu(2+).

Copper Speciation in Variably Toxic Sediments at the Ely Copper Mine, Vermont, United States

At the Ely Copper Mine Superfund site, Cu concentrations exceed background values in both streamwater (160-1200 times) and sediments (15-79 times). Previously, these sediment samples were incubated with laboratory test organisms, and they exhibited variable toxicity for different stream sites. In this study we combined bulk- and microscale techniques to determine Cu speciation and distribution in these contaminated sediments on the basis of evidence from previous work that Cu was the most important stressor in this environment and that variable observed toxicity could have resulted from differences in Cu speciation. Copper speciation results were similar at microscopic and bulk scales. The major Cu species in the more toxic samples were sorbed or coprecipitated with secondary Mn (birnessite) and Fe minerals (jarosite and goethite), which together accounted for nearly 80% of the total Cu. The major Cu species in the less toxic samples were Cu sulfides (chalcopyrite and a covellite-like phase), making up about 80-95% of the total Cu, with minor amounts of Cu associated with jarosite or goethite. These Cu speciation results are consistent with the toxicity results, considering that Cu sorbed or coprecipitated with secondary phases at near-neutral pH is relatively less stable than Cu bound to sulfide at lower pH. The more toxic stream sediment sites were those that contained fewer detrital sulfides and were upstream of the major mine waste pile, suggesting that removal and consolidation of sulfide-bearing waste piles on site may not eliminate all sources of bioaccessible Cu.

Soil organic matter and salinity affect copper bioavailability in root zone and uptake by Vicia faba L. plants

Processes that control the mobility, transformation and toxicity of metals in soil are of special importance in the root-developing zone. For this reason, there is a considerable interest in understanding trace elements (TEs) behavior in soil, emphasising the processes by which plants take them up. Increased root-zone salinity can affect plant TEs uptake and accumulation in plant tissue. Furthermore, copper (Cu) complexation by soil organic matter (SOM) is an effective mechanism of Cu retention in soils, controlling thus its bioavailability. Therefore, a greenhouse pot experiment was conducted to study the effects of soil Cu contamination in a saline environment on faba bean (Vicia faba L.) element uptake. Treatment with NaCl salinity was applied (control, 50 mM NaCl and 100 mM NaCl) on faba bean plants grown in a control and in a soil spiked with Cu (250 and 500 mg kg(-1)). Low and high SOM content trial variants were studied. Cu accumulation occurred in faba bean leaf, pod and seed. Cu contamination affected plant element concentrations in leaves (Na, Ca, Mg, Mn), pod (Zn, Mn) and seed (Mn, Mo, Zn). Root-zone salinity also affected faba bean element concentrations. Furthermore, Cu contamination-salinity and salinity-SOM interactions were significant for pod Cu concentration, suggesting that Cu phytoavailability could be affected by these interactions. Future research will be focused on the mechanisms of Cu translocation in plant and adaptation aspects of abiotic stress.

Speciation and distribution of copper in a mining soil using multiple synchrotron-based bulk and microscopic techniques

Molecular-level understanding of soil Cu speciation and distribution assists in management of Cu contamination in mining sites. In this study, one soil sample, collected from a mining site contaminated since 1950s, was characterized complementarily by multiple synchrotron-based bulk and spatially resolved techniques for the speciation and distribution of Cu as well as other related elements (Fe, Ca, Mn, K, Al, and Si). Bulk X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that soil Cu was predominantly associated with Fe oxides instead of soil organic matter. This agreed with the closest association of Cu to Fe by microscopic X-ray fluorescence (U-XRF) and scanning transmission X-ray microscopy (STXM) nanoanalysis, along with the non-occurrence of photoreduction of soil Cu(II) by quick Cu L3,2-edge XANES spectroscopy (Q-XANES) which often occurs when Cu organic complexes are present. Furthermore, bulk-EXAFS and STXM-coupled Fe L3,2-edge nano-XANES analysis revealed soil Cu adsorbed primarily to Fe(III) oxides by inner-sphere complexation. Additionally, Cu K-edge μ-XANES, L3,2-edge bulk-XANES, and successive Q-XANES results identified the presence of Cu2S rather than radiation-damage artifacts dominant in certain microsites of the mining soil. This study demonstrates the great benefits in use of multiple combined synchrotron-based techniques for comprehensive understanding of Cu speciation in heterogeneous soil matrix, which facilitates our prediction of Cu reactivity and environmental fate in the mining site.

Sorption behavior of Cd, Cu, Pb, and Zn and their interactions in phytoremediated soil

The aim of our study was to compare the sorption properties of a contaminated soil before and after two types of phytoremediation (natural phytoextraction vs. phytostabilization with dolomite limestone (DL) application). Soil from a pot experiment in controlled greenhouse conditions performed for two vegetation periods was used for the study. Lead, as the main contaminant in the studied soil, was easily desorbed by Cu, especially due to the increased affinity of Cu for soil organic matter; hence input of Cu to the studied soil can present another environmental risk in soils contaminated with other metals (such as Pb). In addition, the sorption behavior of chosen metals from single-element solutions differed from multielement solutions. The obtained results proved the different sorption behavior of metals in the single-element solution compared to the multi-element ones. Soil sorption behavior of Cd, Cu, and Zn decreased with the presence of the competitive metals; nevertheless, Pb sorption potential was not influenced by other competitive metals. Natural phytoextraction showed no significant effect on the sorption of Cd, Cu, Pb, and Zn onto the soil On the other hand, phytostabilization associated with DL application improved the soil sorption efficiency of all chosen metals, especially of Cu.

Chemical and structural status of copper associated with oxygenic and anoxygenic phototrophs and heterotrophs: possible evolutionary consequences

Copper adsorption on the surface and intracellular uptake inside the cells of four representative taxons of soil and aquatic micro-organisms: aerobic rhizospheric heterotrophs (Pseudomonas aureofaciens), anoxygenic (Rhodovulum steppense) and oxygenic (cyanobacteria Gloeocapsa sp. and freshwater diatoms Navicula minima) phototrophs were studied in a wide range of pH, copper concentration, and time of exposure. Chemical status of adsorbed and assimilated Cu was investigated using in situ X-ray absorption spectroscopy. In case of adsorbed copper, XANES spectra demonstrated significant fractions of Cu(I) likely in the form of tri-coordinate complexes with O/N and/or S ligands. Upon short-term reversible adsorption at all four studied micro-organisms' cell surface, Cu(II) is coordinated by 4.0 ± 0.5 planar oxygens at an average distance of 1.97 ± 0.02 Å, which is tentatively assigned to the carboxylate groups. The atomic environment of copper incorporated into diatoms and cyanobacteria during long-term growth is similar to that of the adsorbed metal with slightly shorter distances to the first O/N neighbor (1.95 Å). In contrast to the common view of Cu status in phototrophic micro-organisms, XAFS failed to detect sulfur in the nearest atomic environment of Cu assimilated by freshwater plankton (cyanobacteria) and periphyton (diatoms). The appearance of S in Cu 1st coordination shell at 2.27-2.32 Å was revealed only after long-term interaction of Cu with anoxygenic phototrophs (and Cu uptake by soil heterotrophs), suggesting Cu scavenging in the form of sulfhydryl, histidine/carboxyl or a mixture of carboxylate and sulfhydryl complexes. These new structural constraints suggest that adsorbed Cu(II) is partially reduced to Cu(I) already at the cell surface, where as intracellular Cu uptake and storage occur in the form of both Cu(I)-S linked proteins and Cu(II) carboxylates. Obtained results allow to better understand how, in the course of biological evolution, micro-organisms elaborated various mechanisms of Cu uptake and storage, from passive adsorption and uptake to active, protein-controlled surface reduction, and intracellular storage.

Effect of spent mushroom substrate applied to vineyard soil on the behaviour of copper-based fungicide residues

The effect of the addition of spent mushroom substrate (SMS) to the soil as an amendment on the distribution and/or fate of copper from a copper-based fungicide applied to a vineyard soil in La Rioja (N. Spain) was studied. The study was carried out on experimental plots amended or not with SMS at rates of 40 and 100 t ha(-1). The variation in total Cu content in the topsoil (0-10 cm) and in the soil profile (0-50 cm), and the distribution of Cu in different fractions of the topsoil were studied as a function of the dose of Cu added (5 and 10 kg ha(-1)) and of the time elapsed since application (0-12 months). In addition, the changes in the chemical properties (solid organic carbon (OC), dissolved organic carbon (DOC) and pH) of the soils were studied. A greater capacity for Cu retention by the amended soils than by the unamended one was observed only when the fungicide was applied at the high dose. No effect of the amendment rate was noted on this retention capacity. The metal content in the topsoil decreased over time in step with the disappearance of the OC in the amended soil due to its oxidation, mineralization and/or leaching. This decrease in total Cu content was possibly due to the formation of soluble Cu complexes with the DOC, which facilitated its transport through the soil. A re-distribution of Cu in the different soil fractions was also observed over time, mainly from the organic to the residual fraction. The results obtained indicate that the increase in OC due to the application of SMS at the rates used does not lead to any significant increase in the persistence of Cu in the soil over time. Of greater interest would be the assessment of the risk for groundwater quality, owing to possible leaching of the fungicide enhanced by the SMS when SMS and Cu-based fungicides are jointly applied to vineyard soils.

Immobilization of copper in contaminated sandy soils using calcium water treatment residue

Chemical remediation has attracted increasing attention for heavy metal contaminated soils because of its relatively low cost and high efficiency. In this study laboratory incubation and column leaching experiments were conducted to understand the mechanisms of copper (Cu) immobilization by calcium water treatment residue (Ca-WTR) and to estimate the optimal rate for remediating Cu-contaminated soils. The results showed that Ca-WTR amendment significantly raised soil pH and decreased water soluble and exchangeable Cu by 62-90% in the contaminated soils. Most of the bioavailable Cu was converted into more stable Cu fractions, i.e. oxides-bound and residual Cu. The cumulative amount of Cu in the leachate after 10 leaching events was reduced by 80% and 73%, respectively for the two tested soils at the Ca-WTR rate of 20 g kg(-1) for Alfisol and 100 g kg(-1) for Spodosol. These results indicate that Ca-WTR is effective in raising soil pH and converting labile Cu to more stable forms in the contaminated soils. A pH value of 6.5 was found to be critical for lowering Cu availability in the soils. Based on this criterion and pH response curve to Ca-WTR application, the optimal rates of Ca-WTR can be estimated for different Cu-contaminated soils.

Carbon paste electrodes modified with biosolids, soils and biocomposites utilized to study the interaction between organic matter and copper

Carbon paste electrodes (CPEs) modified with a biosolid, two types of soils with different amounts of organic matter (OM), and two biocomposites (soils mixed with a biosolid) were used to assess and compare the Cu(II) ion retention properties of the organic matter contained in the samples. The accumulation of Cu(II) on the surface of the modified carbon paste electrodes (MCPEs) was performed under open-circuit conditions. When comparing the response of the MCPEs while assessing parameters such as pH, preconcentration time, and adsorption/desorption capacity, it was found that the reaction mechanism of the two soils is different between the soils and dissimilar from the biosolid; while the biocomposites show reaction mechanisms that are intermediate between those of the soils and the biosolid. This was proven with the use of infrared spectroscopy, since the FTIR spectra show similarities between the two soils and significant differences between the soils and the biosolid.

Pesticidal copper (I) oxide: environmental fate and aquatic toxicity

Besides being a naturally occurring element and an essential micronutrient, copper is used as a pesticide, but at generally higher concentrations. Copper, unlike organic pesticides, does not degrade, but rather enters a complex biogeochemical cycle. In the water column, copper can exist bound to both organic and inorganic species and as free or hydrated copper ions. Water column chemistry affects copper speciation and bioavailability. In all water types (saltwater, brackish water, and freshwater), organic ligands in the water column can sequester the majority of dissolved copper, and therefore, organic ligands play the largest role in copper bioavailability. In freshwater, however, the geochemistry of a particular location, including water column characteristics such as water hardness and pH, is a significant factor that can increase copper bioavailability and toxicity. In most cases, organic ligand concentrations greatly exceed copper ion concentrations in the water column and therefore provide a large buffering capacity. Hence, copper bioavailability can be grossly overestimated if it is based on total dissolved copper (TDCu) concentrations alone. Other factors that influence copper concentrations include location in the water column, season, temperature, depth, and level of dissolved oxygen. For example, concentrations of bioavailable copper may be significantly higher in the bottom waters and sediment pore waters, where organic ligands degrade much faster and dissolved copper is constantly resuspended and recycled into the aquatic system. Aquatic species differ greatly in their sensitivity to copper. Some animals, like mollusks, can tolerate high concentrations of the metal, while others are adversely affected by very low concentrations of copper. Emerging evidence shows that very low, sublethal copper levels can adversely affect the sense of smell and behavior of fish. The developmental stage of the fish at the time of copper exposure is critical to the reversibility of sensory function effects. The fish olfactory system may be the most sensitive structure to copper pollution. The major factors that influence copper-induced toxicity are dissolved organic carbon and water salinity. Dissolved organic carbon reduces copper toxicity by sequestering bioavailable copper and forming organic complexes with it. Salinity, on the other hand, influences copper bioavailability at the biological action site and also affects metal biodistribution and bioaccumulation in the organism. Therefore, the salinity gradient can increase or decrease copper toxicity in different aquatic species. In some killifish, copper may affect different organs at different times, depending on the water salinity. The most studied and best explained copper toxicity mechanisms involve inhibition of key enzymes and disruption of osmoregulation in the gill. Other toxicity mechanisms may involve reactive oxygen species generation and changes of gene transcription in the fish olfactory signaling pathway. More studies are needed to evaluate the potential magnitude of copper remobilization from the sediment that may result from climate change and its effects on surface waters. Moreover, the environmental exposure, fate, and ecotoxicity of emerging metal nanoparticles, including nanocopper, will require additional studies as new forms of copper appear from application of nanotechnology to copper compounds.

Contamination of vineyard soils with fungicides: a review of environmental and toxicological aspects

The contamination of agricultural soils with inorganic (Cu-based) and organic pesticides (including their residues) presents a major environmental and toxicological concern. This review summarizes available studies published on the contamination of vineyard soils throughout the world with Cu-based and synthetic organic fungicides. It focuses on the behavior of these contaminants in vineyard soils and the associated environmental and toxicological risks. The concentrations of Cu in soils exceed the legislative limits valid in the EU in the vast majority of the studied vineyards. Regarding the environmental and toxicological hazards associated with the extensive use of fungicides, the choice of fungicides should be performed carefully according to the physico-chemical properties of the soils and climatic and hydrogeological characteristics of the vine-growing regions.

Molecular characterization of copper in soils using X-ray absorption spectroscopy

Bioavailability of Cu in the soil is a function of its speciation. In this paper we investigated Cu speciation in six soils using X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and synchrotron-based micro X-ray fluorescence (mu-XRF). The XANES and EXAFS spectra in all of the soils were the same. mu-XRF results indicated that the majority of the Cu particles in the soils were not associated with calcium carbonates, Fe oxides, or Cu sulfates. Principal component analysis and target transform of the XANES and EXAFS spectra suggested that Cu adsorbed on humic acid (HA) was an acceptable match. Thus it appears that Cu in all of the soils is primarily associated with soil organic matter (SOM). Theoretical fitting of the molecular structure in the soil EXAFS spectra revealed that the Cu in the soils existed as Cu atoms bound in a bidentate complex to O or N functional groups.

Retention of copper originating from different fungicides in contrasting soil types

This work described the retention of Cu from two different commonly used pesticides, the Bordeaux mixture (CuSO(4)+Ca(OH)(2)) and Cu-oxychloride (3Cu(OH)(2).CuCl(2)), and from Cu(NO(3))(2) in contrasting soil types (Leptosol, Chernozem, Cambisol). Thermodynamic modeling showed that Cu speciation was similar in all fungicide solutions. However, the retention of Cu differed with the fungicide used (maximum retention from the Bordeaux mixture) which indicates that different retention processes occurred in the studied soils. The suggested mechanisms include: specific and non-specific adsorption (especially on soil organic matter), precipitation of newly formed phases, such as CuO, Cu(OH)(2), Cu(2)(OH)(3)NO(3), CuCO(3)/Cu(2)(OH)(2)CO(3) and in the case of the Bordeaux mixture, precipitation of various Cu-hydroxysulfates. These phases were identified by the speciation model. The retention of fungicide-derived Cu in the studied soil types followed well the Freundlich isotherm and was directly controlled by the chemical form of Cu. This fact should be taken into account for both environmental and practical applications.

Speciation of Cu in a contaminated agricultural soil measured by XAFS, micro-XAFS, and micro-XRF

Contamination of agricultural soils with Cu as a result of fungicide application and spills threatens environmental quality and reduces soil quality for crop growth. In this paper advanced spectroscopic and microscopic methods were used to elucidate the Cu speciation in a calcareous soil contaminated since the 1940s. Microscopically focused synchrotron-based XRF (micro-SXRF) was used to map the elemental distribution in the soils. Results indicated that most of the Cu was not associated with metal oxides, silicates, phosphates, or carbonates. Bulk and microscopically focused X-absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra indicated thatthe Cu in the soil was predominantly Cu adsorbed on soil organic matter (SOM). Interpretation of the fitting results suggests that the Cu is complexed to SOM via bidentate inner-sphere coordination with carboxyl or amine ligands. Results presented in this paper provide detailed information on the molecular coordination of Cu in a contaminated soil. Such information is critical for understanding the long-term fate and best management practices for Cu in the environment.