Nuno Durães

Comparison of adipocere formation in four soil types of the Porto (Portugal) district.

Four typical soils of the Porto (Portugal) area were characterized and used to study the decomposition of buried pieces of pork meat under controlled laboratory experiments (an 8 month experiment with a relatively high soil moisture and a 1 month experiment with relatively low soil moisture). The soils types were: organic, sandy, gravel and clay-gravel soils. Soils were characterized for their grain size distribution, pH, water content, organic matter percentage and mineral composition. Four free fatty acids (myristic, palmitic, oleic and stearic) were analysed (using a methodology based on an extraction step followed by a derivatization reaction and high performance liquid chromatography analysis) in soil samples as a sign of adipocere formation. The direct sensorial analysis of the buried sample residues and the free fatty acids profiles of the sampled soils showed that sandy and clay-gravel soils (in a low moisture environment) slowed the normal decomposition process promoting the formation of adipocere. Nevertheless, this apparent soil effect is indirect and a consequence of the different water retention and permeability of the soils. Thus, the water content of the soils is a crucial factor for adipocere formation.

Assessment of metal pollution in a former mining area in the NW Tunisia: spatial distribution and fraction of Cd, Pb and Zn in soil

This study aims to evaluate the impact of the former mining Touiref district (NW Tunisia) on the spatial distribution of metal contamination. In order to characterize the metal content of the tailings and to assess how far the soils from the district could be impacted by metals, a sampling campaign was conducted. According to the spatial distribution concentration maps of potential toxic elements (PTE), the highest concentrations occur near the flotation tailings and in mining facilities and decrease abruptly with distance. These results confirm that wind is the main agent capable of dispersing metals in a W–E direction, with concentrations exceeding the standards of soil quality for Cd, Pb and Zn over several hundred metres away from the source, facilitated by the small-size fraction and low cohesion of tailings particles. Chemical fractionation showed that Pb and Cd were mainly associated with the acid-soluble fraction (carbonates) and Fe-(oxy) hydroxides, while Zn was mainly associated with Fe-(oxy) hydroxides but also with sulphides. Thus, the immobilization of metals in solution may be favoured by the alkaline conditions, promoted by carbonates dissolution. However, being carbonate important-bearing phases of Cd and Pb (but also for Zn), the dissolution facility of these minerals may enhance the release of metals, particularly far away from the mine where the physicochemical conditions can be different. Also, the metal uptake by plants in these alkaline conditions may be favoured, especially if secondary phases with high sorption ability are reduced at this site. A remediation plan to this area is needed, with particularly attention in the confinement of the tailings.

Integrating geochemical (surface waters, stream sediments) and biological (diatoms) approaches to assess AMD environmental impact in a pyritic mining area: Aljustrel (Alentejo, Portugal)

Aljustrel mines were classified as having high environmental hazard due to their large tailings volume and high metal concentrations in waters and sediments. To assess acid mine drainage impacted systems whose environmental conditions change quickly, the use of biological indicators with short generation time such as diatoms is advantageous. This study combined geochemical and diatom data, whose results were highlighted in 3 groups: Group 1, with low pH (1.9-5.1) and high metal/metalloid (Al, As, Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn; 0.65-1032 mg/L) and SO4 (405-39124 mg/L) concentrations. An acidophilic species, Pinnularia aljustrelica, was perfectly adapted to the adverse conditions; in contrast, teratological forms of Eunotia exigua were found, showing that metal toxicity affected this species. The low availability of metals/metalloids in sediments of this group indicates that metals/metalloids of the exchangeable fractions had been solubilized, which in fact enables metal/metalloid diatom uptake and consequently the occurrence of teratologies; Group 2, with sites of near neutral pH (5.0-6.8) and intermediate metal/metalloid (0.002-6 mg/L) and SO4 (302-2179 mg/L) concentrations; this enabled the existence of typical species of uncontaminated streams (Brachysira neglectissima, Achnanthidium minutissimum); Group 3, with samples from unimpacted sites, showing low metal/metalloid (0-0.8 mg/L) and SO4 (10-315 mg/L) concentrations, high pH (7.0-8.4) and Cl contents (10-2119 mg/L) and the presence of brackish to marine species (Entomoneis paludosa). For similar conditions of acidity, differences in diversity, abundance and teratologies of diatoms can be explained by the levels of metals/metalloids.

Chemistry and FT-IR spectroscopic studies of plants from contaminated mining sites in the Iberian Pyrite Belt, Portugal

Abstract Semi-aquatic and native plants collected from a mining site in the Iberian Pyrite Belt were analysed. Semi-aquatic plants showed enrichment of Cu (1.2-11 times), Zn (1.3-6 times), Pb (5-8 times) and As (24-1300 times) relative to typical concentrations in plants of the same species growing at uncontaminated sites. Translocation factors indicate limited internal metal transportation from roots to shoots. Infrared spectroscopy identified aromatic and aliphatic C-H (CH2) groups, S-O complexes and kaolinite in semi-aquatic plants.

Inorganic Pollutants in Soils

Abstract Soil is a major reservoir for Potential Toxic Elements (PTEs). These PTEs can occur in various forms in soil and different bonding forces keep them bound to soil particles. The high concentrations, form and availability of PTEs in environment, can compromise the soil ecosystem and the growth of plants. At the end of the chain PTEs may entering in human body by direct (inhalation or ingestion of soil particles) or indirect (plant consumption) routes, which may cause physiological or metabolic disruptions. This chapter discusses the PTEs, their sources and implications for soils, and the methodologies used for monitoring such pollutants in soil. In addition, three case studies are presented: one related with agricultural Cu inputs in vineyard soils of Douro Region (Portugal) by its use as fungicide on grapes; another focused in urban soil pollution in Athens (Greece); and the last one related to a typical mining pollution case with As in Mexico.

Distribution, Transport and Fate of Pollutants

Abstract Soil is a complex dynamic system of critical importance for life on Earth. As natural and anthropogenic processes continuously use soil as sink or pathway to potentially toxic elements (PTEs) and organic pollutants (OPs), it is crucial to understand their distribution, transport, and fate. This chapter provides a brief and focused overview about the migration of PTEs and OPs in soil. The physical, chemical, and biological mechanisms of soil were analyzed and discussed, due to the influence that exert on the pollutants behavior (form, availability, and toxicity), as well as in the release and retention processes that affect their migration. Thus, the fate of these pollutants is outlined by the pollutants intrinsic characteristics and by the action of soil abiotic and biotic mechanisms. Modeling pollutants in soil is a key tool to the study and understanding of the complex leaching and transport processes involved on this.