**1. Introduction**

and bioaccumulation as indicators. Science of the Total Environment 2012;414 187–

[40] Appel, C., Ma, L. Concentration, pH, and surface charge effects on cadmium and

[41] Yang JY; Yang XE., He ZL., Li TQ., Shentu JL., Stoffella PJ. Effects of pH, organic acids, and inorganic ions on lead desorption from soils. Environmental Pollution

[42] Ming H., He WX, Lamb DT., Megharaj M., Naidu R. Bioavailability of lead in conta‐ minated soil depends on the nature of bioreceptor Ecotoxicology and Environmental

[43] Cheyns K., Peeters S., Delcourt D., Smolders E. Lead phytotoxicity in soils and nu‐ trient solutions is related to lead induced phosphorus deficiency. Environmental Pol‐

[44] Bigham J M., Schwertmann U., Traina SJ., Winland RL., Woolf M. Schwertmannite and the chemical modelling of iron in acid sulfate waters. Geochim. Cosmochim. Ac‐

[45] Yu J-Y., Heo B., Cho J-P., Chang H-W. Apparent solubilities of schwertmannite and ferrihydrite in natural stream waters polluted by mine drainage. Geochim. Cosmo‐

lead sorption in three tropical soils. J. Environ. Qual. 2002;31 581-589.

197.

2006;143 9-15.

Safety 2012;78 344–350.

798 Environmental Risk Assessment of Soil Contamination

lution 2012;164 242-247.

ta 1996;60 2111–2121.

chim. Acta 1999;63 3407–3416.

Metals are chemically very reactive in the environment, which results in their mobility and bioavailability to living organisms. Metals can be present in all environmental compart‐ ments as different species, with the TMs associated with different ligands, but never being irreversibly transformed or metabolized, and in those meaning metals are different from or‐ ganic compounds. People can be exposed to high levels of toxic metal by breathing air, drinking water, or eating food that contains it. As a consequence, metals get into the human body by different routes - by inhaling, over skin, and ingestion of contaminated food. The issue of toxicity is usually merely a matter of quantity, with the range varying for each ele‐ ment.

## **1.1. Why we need to study trace metals in soils?**

Soil is an important compartment of the environment in which anthropogenic loading of trace metals puts ecosystems and their inhabitants at a health risk. Repeated use of metalenriched chemicals, fertilizers, and organic amendments such as sewage sludge as well as wastewater may cause contamination at a large scale. So far, it is believed that most soils in Europe have not been significantly enriched in trace metals by anthropogenic activity. This is changing as livestock production expands, fertilizer application increases, and biosolids and effluent applications to agricultural soils become more common. Accumulation of trace metals in soil has potential to restrain the soil functions, cause toxicity to plants, and enter the food chain.

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Many chemical reactions are responsible for the behaviour of TMs in soils, but the most im‐ portant processes that control their bioavailability and mobility are precipitation-dissolu‐ tion, adsorption-desorption, and complexation. The ability of soils to adsorb metal ions from aqueous solution is of special interest and has consequences for both agricultural issues such as soil fertility and environmental questions such as remediation of polluted soils and waste deposition [1].

Metal-soil interaction is such that when metals are introduced at the soil surface, their mobi‐ lisation does not occur to any great extent unless the metal retention capacity of the soil is overloaded, or metal interaction with the associated waste matrix enhances mobility [2]. The most important interfaces involved in TMs transformation in soils are mineral groups com‐ monly found in soil: aluminosilicates, oxides and organic matter. Through their surface elec‐ trochemical properties, these soil minerals control adsorption, transformation, and release behaviour of chemical constituents (e.g. nutrients and contaminants) to water and soil solu‐ tion [3]. Furthermore, soil-surface electrochemical properties vary between soil types and depend on factors such as parent material, climate, and vegetation.

So that, full understanding and prediction of chemical behaviour of an element in the terres‐ trial environment is possible only by identification of all forms in which that element can be found in soil under different environmental conditions. Copper is one of the major toxic metals, and a highly reactive one, as well. Elevated levels of Cu in agricultural soils result from the use of Cu-containing compounds to control plant diseases and from application of manure or sewage sludge. These applications may lead to gradual accumulation of Cu in the soil and thereby increase Cu toxicity toward crop and beneficial microorganisms. In this article, the actual risk of high concentrations of copper and its mobility in vineyard soils is reviewed considering sources, chemical processes in soil and biogeochemical behaviour of copper as well as impact on agroecosystem and environment in general.

#### **1.2. Sources and behaviour of copper in soils**

Copper occurs in the Earth's crust at concentrations between 25-75 mg kg-1, with the aboun‐ dance pattern that shows the tendency for the concentration in mafic igneous rocks (60-120 mg kg-1) and argillaceous sediments (40-60 mg kg-1), but it is rather excluded from the carbo‐ nate rocks (2-10 mg kg-1) [4]. Values for soil contents generally range worldwide from 1 to 140 mg kg-1 depending on the nature of the soil parent material.

In soil solids and solution copper occurs almost exclusively as the divalent cation Cu2+, and the reduction of Cu2+ to Cu+ and Cuo is possible under reducing conditions. As a chacophile, copper associates with with sulfide in the very soluble minerals, Cu2S and CuS. Being very reactive in soil, copper is found in all matrix components. Most of the colloidal soil material (clay minerals, oxides of Mn, Al i Fe, and organic matter) adsorb copper strongly, and in‐ creasingly so as the pH is raised [5]. For copper, specific adsorption, which is not significant for the most of metal ions, seems to play a more important then nonspecific adsorption. Amorphous and cristalline oxides of Fe and Al easy adsorb Cu2+, regardless the excess of al‐ kali metals in the solution [6]. However, the most important sink for Cu is soil organic mat‐ ter, and its complexation with organic matter is one of the most efficient mechanisms of Cu2+ retention in soil [7]. This restricts Cu bioavailability, but also considerably reduces the risks of phytotoxicity of the accumulated anthropogenic input and its vertical migration. Organi‐ cally complexed Cu2+ is bound more tightly than any other divalent transition metal and of low lability these complexes results in limiting copper bioavailability. This prevents copper mobility and its transport through soil to underground, and reduces substantially the risk of the groundwater contamination.

#### **1.3. Anthropogenic inputs and copper contamination of cultivated soils**

Many chemical reactions are responsible for the behaviour of TMs in soils, but the most im‐ portant processes that control their bioavailability and mobility are precipitation-dissolu‐ tion, adsorption-desorption, and complexation. The ability of soils to adsorb metal ions from aqueous solution is of special interest and has consequences for both agricultural issues such as soil fertility and environmental questions such as remediation of polluted soils and waste

Metal-soil interaction is such that when metals are introduced at the soil surface, their mobi‐ lisation does not occur to any great extent unless the metal retention capacity of the soil is overloaded, or metal interaction with the associated waste matrix enhances mobility [2]. The most important interfaces involved in TMs transformation in soils are mineral groups com‐ monly found in soil: aluminosilicates, oxides and organic matter. Through their surface elec‐ trochemical properties, these soil minerals control adsorption, transformation, and release behaviour of chemical constituents (e.g. nutrients and contaminants) to water and soil solu‐ tion [3]. Furthermore, soil-surface electrochemical properties vary between soil types and

So that, full understanding and prediction of chemical behaviour of an element in the terres‐ trial environment is possible only by identification of all forms in which that element can be found in soil under different environmental conditions. Copper is one of the major toxic metals, and a highly reactive one, as well. Elevated levels of Cu in agricultural soils result from the use of Cu-containing compounds to control plant diseases and from application of manure or sewage sludge. These applications may lead to gradual accumulation of Cu in the soil and thereby increase Cu toxicity toward crop and beneficial microorganisms. In this article, the actual risk of high concentrations of copper and its mobility in vineyard soils is reviewed considering sources, chemical processes in soil and biogeochemical behaviour of

Copper occurs in the Earth's crust at concentrations between 25-75 mg kg-1, with the aboun‐ dance pattern that shows the tendency for the concentration in mafic igneous rocks (60-120 mg kg-1) and argillaceous sediments (40-60 mg kg-1), but it is rather excluded from the carbo‐ nate rocks (2-10 mg kg-1) [4]. Values for soil contents generally range worldwide from 1 to

In soil solids and solution copper occurs almost exclusively as the divalent cation Cu2+, and

copper associates with with sulfide in the very soluble minerals, Cu2S and CuS. Being very reactive in soil, copper is found in all matrix components. Most of the colloidal soil material (clay minerals, oxides of Mn, Al i Fe, and organic matter) adsorb copper strongly, and in‐ creasingly so as the pH is raised [5]. For copper, specific adsorption, which is not significant for the most of metal ions, seems to play a more important then nonspecific adsorption. Amorphous and cristalline oxides of Fe and Al easy adsorb Cu2+, regardless the excess of al‐ kali metals in the solution [6]. However, the most important sink for Cu is soil organic mat‐ ter, and its complexation with organic matter is one of the most efficient mechanisms of Cu2+

is possible under reducing conditions. As a chacophile,

depend on factors such as parent material, climate, and vegetation.

copper as well as impact on agroecosystem and environment in general.

140 mg kg-1 depending on the nature of the soil parent material.

and Cuo

**1.2. Sources and behaviour of copper in soils**

the reduction of Cu2+ to Cu+

deposition [1].

800 Environmental Risk Assessment of Soil Contamination

Trace elements in general enter an agroecosystem through both natural and anthropogenic processes. The latest includes TEs inputs through use of agrochemicals, farm manure, bio‐ solids and composts, industrial and municipal waste, irrigation, and wet and/or dry depos‐ its. Being widely used, copper is a common metal pollutant released to environment as a result of man's activities. Copper is an essential nutrient, but in excess in soils it becomes toxic to plants and some micro-organisms, disrupting nutrient-cycling and inhibiting the mineralisation of essential nutrients such as nitrogen and phosphorus. Some species accu‐ mulate copper. Toxic effects on fish and other aquatic organisms have also been observed. For humans, excess amount of this trace metal can have serious health effects.

Elevated levels of copper in agricultural soils result from the use of Cu-containing com‐ pounds to control plant diseases and from application of manure or sewage sludge. In‐ creased concentration of Cu in soils under long-term production of grapevine, citrus and other fruit crops have been recorded in numerous studies. The Bordeaux mixture, an effi‐ cient agent for prevention of vine «Downy Mildew», *Plasmopara viticola*, has been routinely used in Europe since the end of the 19th century with its concentrations and the number of treatments depending on weather conditions, infection intensity and vineyard management. The century-old practice of using Cu-sulphates and other copper containing fungicides to protect grapevine, but also other agricultural crops, in temperate and tropic climatic regions, resulted in significant Cu accumulation in soils [8]. Most of the copper accumulated in leaves and soil by spraying will be retained in topsoil through the biological cycle and till‐ age [9-11]. Comparison of copper contents of 110 to 1500 mg kg-1 with its usual content in agricultural soils (20 – 30 mg kg-1) points to their connection with such practice [12]. Copper can be either a micro nutrient or a toxic element which depends on the copper concentra‐ tion. Determination of the total content of metals in soils is an important step in estimating the hazards to the vital roles of soil in the ecosystem, and also in comparison with the quali‐ ty standards in terms of the effects of pollution and sustainability of the system.

From the ecotoxicological point of view, it is equally important to determine the bioavaila‐ bility of Cu accumulated in vineyards, i.e., the fraction of the total metal content in soil that can be utilized by biota [13]. It depends on the soils properties, temperature, water content and aeration, and also on plant species. The toxicity of copper is essentially observed in acid soils, but not in calcareous soils and for copper contents as high as those reported in vine‐ yard soils. A number of authors have found positive correlation between copper retention and pH [14, 15] and sum of bases or exchangeable calcium [16]. The bioavailability of copper has also been reported to decrease when the cation exchange capacity or the level of organic matter increases [5, 15]. Various electrolytes such as water, buffered or unbuffered salt solu‐ tions, chelating agents, diluted acids or a mix of these reagents can be used to estimate the biavailability of copper in soils (reviews given by [17, 18]).

#### **1.4. Fractionation and bioavailability of copper in soils**

The concepts of «bio-availability» and «bio-accessibility» were introduced to express wheth‐ er the actual concentration of a toxic element would have effects on organisms [19]. The main challenge that comes out from the assessment of loads of trace and toxic metals is the methodology of determination or prediction of the trace element content in a soil that results in toxicity [20]. Trace element mobility and bioavailability is determined by their transfer be‐ tween the soil solid phase and the soil solution [21], and trace element in soils can be divid‐ ed into inert and the potentially toxic labile fraction [22]. Thus, the impact of trace metals on soil and the surrounding environment in most cases cannot be predicted simply by measur‐ ing their total concentration. This is because only soluble and mobile fractions have the po‐ tential to leach or to be taken up by plants, and enter the food chain. Furthermore, Cu content in the plants usually does not well correspond to the total soil copper content [23].

Water-soluble and exchangeable copper fractions are considered to be bioavailable; copper complexed with oxide, carbonate and organic matter are potentially bioavailable fractions; and mineral fraction is considered to be non-bioavailable [24]. However, fractionation does not provide information about species of metals in soil. Metal speciation is one of the most important properties that determine the behavior and toxicity of metals in the environment. Chemical speciation of an element refers to its specific form characterized by a different iso‐ topic composition, molecular structure, and electronic or oxidation state [25]. Speciation is the process of identification and determination of different chemical and physical forms of elements present in a sample [26]. TMs speciation is determined by their reactivity and physical and chemical properties of the soil. Metals are very reactive in the environment and can relatively easy change form in soil, making their speciation non stable. Among many chemical processes that are involved in the transformation of TEs in soils, precipitation-dis‐ solution, adsorption-desorption and complexation are the most important in controlling their bioavailability and mobility. Metals that occur in cationic forms have a higher ability of binding to negatively charged soil colloids, and are thus less bioavailable, but more easily accumulate in soil, unlike the anionic forms that are mainly present in soil solution and are more bioavailable, but are more readily leached from the soil. Formation of complexes with soil organic matter, adsorption onto the surfaces of clays and Fe and Mn oxides regulate the behavior of copper in the soil [23]. Thus, copper bioavailability in soil depends on soil pH, redox potential, CEC, amount and nature of organic matter and soil minerals [27].

Chemical extractions are used for soil copper bioavailability predictions, often in compari‐ son with its content in plants [23]. Copper is not readily mobile in plants and root concentra‐ tion is considered to be a good indicator of the plant copper content. It has been assumed that the factors affecting metal fractionation and bioavailability in soil include root-induced pH changes, metal binding by root exudates, root-induced microbial activities and root de‐ pletion as a consequence of plant uptake [28]. In the root developing zone, rhizosphere, processes that control the mobility, transformation and toxicity of metals in soil are under direct influence of plant roots and may differ from those in bulk soil. Thus, root activities can considerably modify TM speciation in the rhizosphere. Metal plant root adsorption is determined by ionization of negatively charged binding sites for metal on root surfaces. Cupric ions bind to a specific carrier on the root cell plasmalemma surface [29] and plant uptake depends on the available copper in the soil and the nutritional status of a plant [30]. Soil pH determines aqueous metal speciation, affecting metal sorption and desorption on the solid phase [31], but plant roots as well. As the degree of biotic ligands ionization in‐ creases with pH, the metal ion root adsorption increases. Vice versa, the adsorption capacity of the plant root for cupric ion decreases with decreasing solution pH. Rhizosphere pH modifications by plant are a known occurrence and root zone alkalization may decrease the exposure of plant roots to copper by promoting formation of organic complexes and reduc‐ ing copper solubility throughout rhizosphere area [32]. Furthermore, plant may directly de‐ crease copper bioavailability near roots by excretion of metal-binding compounds that can complex the free cupric ions [33].

matter increases [5, 15]. Various electrolytes such as water, buffered or unbuffered salt solu‐ tions, chelating agents, diluted acids or a mix of these reagents can be used to estimate the

The concepts of «bio-availability» and «bio-accessibility» were introduced to express wheth‐ er the actual concentration of a toxic element would have effects on organisms [19]. The main challenge that comes out from the assessment of loads of trace and toxic metals is the methodology of determination or prediction of the trace element content in a soil that results in toxicity [20]. Trace element mobility and bioavailability is determined by their transfer be‐ tween the soil solid phase and the soil solution [21], and trace element in soils can be divid‐ ed into inert and the potentially toxic labile fraction [22]. Thus, the impact of trace metals on soil and the surrounding environment in most cases cannot be predicted simply by measur‐ ing their total concentration. This is because only soluble and mobile fractions have the po‐ tential to leach or to be taken up by plants, and enter the food chain. Furthermore, Cu content in the plants usually does not well correspond to the total soil copper content [23].

Water-soluble and exchangeable copper fractions are considered to be bioavailable; copper complexed with oxide, carbonate and organic matter are potentially bioavailable fractions; and mineral fraction is considered to be non-bioavailable [24]. However, fractionation does not provide information about species of metals in soil. Metal speciation is one of the most important properties that determine the behavior and toxicity of metals in the environment. Chemical speciation of an element refers to its specific form characterized by a different iso‐ topic composition, molecular structure, and electronic or oxidation state [25]. Speciation is the process of identification and determination of different chemical and physical forms of elements present in a sample [26]. TMs speciation is determined by their reactivity and physical and chemical properties of the soil. Metals are very reactive in the environment and can relatively easy change form in soil, making their speciation non stable. Among many chemical processes that are involved in the transformation of TEs in soils, precipitation-dis‐ solution, adsorption-desorption and complexation are the most important in controlling their bioavailability and mobility. Metals that occur in cationic forms have a higher ability of binding to negatively charged soil colloids, and are thus less bioavailable, but more easily accumulate in soil, unlike the anionic forms that are mainly present in soil solution and are more bioavailable, but are more readily leached from the soil. Formation of complexes with soil organic matter, adsorption onto the surfaces of clays and Fe and Mn oxides regulate the behavior of copper in the soil [23]. Thus, copper bioavailability in soil depends on soil pH,

redox potential, CEC, amount and nature of organic matter and soil minerals [27].

Chemical extractions are used for soil copper bioavailability predictions, often in compari‐ son with its content in plants [23]. Copper is not readily mobile in plants and root concentra‐ tion is considered to be a good indicator of the plant copper content. It has been assumed that the factors affecting metal fractionation and bioavailability in soil include root-induced pH changes, metal binding by root exudates, root-induced microbial activities and root de‐ pletion as a consequence of plant uptake [28]. In the root developing zone, rhizosphere,

biavailability of copper in soils (reviews given by [17, 18]).

802 Environmental Risk Assessment of Soil Contamination

**1.4. Fractionation and bioavailability of copper in soils**

In this article, the actual risk of high concentrations of copper and its mobility in vineyard soils is reviewed considering sources, chemical processes in soil and biogeochemical behav‐ iour of copper as well as impact on agroecosystem and environment in general.
