RICERCA ITALIANA     

BIOTIC AND ABIOTIC PROCESSES AFFECTING THE MOBILITY AND BIOAVAILABILITY OF TOXIC ELEMENTS IN THE SOIL-PLANT SYSTEM

Università degli Studi di Napoli "Federico II"

Abstract

We intend to carry out researches on abiotic and biotic processes which influence the mobility of As, Cu and Cr in soil environments and their bioavailability and toxicity for microorganisms and plants.
Heavy metals and metalloids easily interact with soil components (clay minerals, microorganisms, organic matter, Fe and Al oxides, enzymes and so on). However, abiotic and biotic components should not be considered as separate entities but rather as a united system constantly in close association and interactions with each other in terrestrial environment. It is essential that scientists interested in different disciplines related to environmental soil chemistry, soil biochemistry, soil microbiology, plant nutrition and plant biochemistry interact each other to seek understanding the mechanisms regarding the mobility and bioavailability of xenobiotics in the soil-plant system.
Chemical, physico-chimical and mineralogical analyses of soil samples of polluted sites will be carried out and then a multistep selective sequential extraction will be used to characterize different species such as exchangeable, bound to carbonates, metal-organic complex-bound, amorphous mineral colloid-bound, crystalline Fe oxide-bound, and residual. On these soils, the microbial biomass, some soil enzymatic activities, soil respiration, substrate-induced respiration as well as taxonomical and functional diversity of the bacterial communities will be performed. Furthermore, we >>>

Principal Investigator

Antonio VIOLANTE Università degli Studi di NAPOLI "Federico II"

Research Objectives

Researches on the factors which may influence the mobility and phytoavailability of Cu, As and Cr deserve particular attention because their presence in soils and other environments is of great concern. In fact, these elements are included in the U.S. Environmental Protection Agency's list of priority pollutants.
In order to know the potential toxicity of a trace element in soil environments it is necessary to study the factors which affect its mobility and bioavailability for plants and microorganisms.
The mere presence of a toxic element in soil may not adversely affect either a single organism or a community of organisms if that element is not in a biologically, chemically, or physically unavailable chemical form. It is accepted that total soil heavy metal content alone is not a good measure of bioavailability and not a very useful tool to determine the potential risks from soil contamination. The mobility and bioavailability, and then potential toxicity of a heavy metal in the soil depend on its concentration in soil solution, the nature of its association with other soluble species and the soil's ability to release the heavy metal from the solid phase to replenish that removed from the soil solution by the plants.
Heavy metals and metalloids easily interact with soil components (clay minerals, microorganisms, organic matter, Fe and Al oxides, enzymes and so on). However, abiotic and biotic components should not be considered as separate entities >>>

First Results

- Speciation of different forms of Cu and As in polluted soils. Definition of efficient and reproducible analytical methodologies to measure trace metals of environmental concern.
- To correlate the relative importance of the fractions of a heavy meta

Timescale

24 months

National and international background

Researches on the factors which may influence the mobility and phytoavailability of copper, arsenic and chromium deserve particular attention because their presence in soils and other environments is of great concern (Adriano, 1992). These elements are included in the U.S. Environmental Protection Agency's list of priority pollutants. They exist in more than one oxidation state [As(V), As(III) or Cu(I), Cu(II)] and some of them may be present as cations (Cr3+) and anions (chromate) (Sparks, 1995; Jackson, 1998). These toxic elements have deleterious effects on humans through contamination of the food chain or drinking waters, such as disorders of the heart and circulatory system, cancer, anemia, liver disfunction and so on. Arsenic pollution toxicity and increased appearance in the biosphere has triggered public and political concern (Huang et al., 1998; 2002; Frankerberg, 2002; Violante et al. 2002). As(III) is more mobile and about 200 times more toxic than As(V). The presence of As in the environment is attributable both to the parent materials and to anthropogenic waste. Arsenic may lead to contamination of both agricultural soils and surface waters and sediments in areas where mining and smelting are present (Smith et al., 1998; ). In many countries indiscriminate use of arsenical pesticides until the mid-1900 has led to extensive contamination of soil worldwide. Many countries (including Italy) are severely affected by the arsenic crisis, but the situation is >>>