Trace Metal Concentrations In Soils Research Articles

Multipotential Trace Metal Concentrations in Soil Associated with the Ecological and Human Health Risk near the Rooppur Nuclear Power Plant, Pabna, Bangladesh

Multipotential Trace Metal Concentrations in Soil Associated with the Ecological and Human Health Risk near the Rooppur Nuclear Power Plant, Pabna, Bangladesh

Exploring the Potential Risk of Heavy Metal Pollution of Edible Cultivated Plants in Urban Gardening Contexts Using a Citizen Science Approach in the Project “Heavy Metal City-Zen”

Urban gardening has become increasingly popular, creating green oases in cities; however, many of these activities are undertaken in areas of high traffic density or on ex-brown field sites. As a consequence, there are still some barriers to the adoption of these urban gardening practices for food production. One of the public concerns is the transfer of urban pollutants such as heavy metals into the consumer’s food chain, however, city-wide data is often difficult and expensive to collect. In the citizen science project described herein, we conducted simple citizen-led common collaborative experiments in urban community gardens. These data provided information on the potential risk of heavy metal contaminants and ways in which to mitigate those risks in an urban gardening context. Generally, values were below guideline thresholds, however, at a few garden sites, soil trace metal concentrations (Pb, Cd, Zn) exceeded Austrian recommended limits. Moreover, only at two sites were plant trace metal concentrations shown to be above European food standards limits. Given the citizen’s positive response to the project, we suggest expanding this study to the whole of Vienna, giving newly established gardens a chance to predetermine the risks posed by their local soils.

Comparing Trace Elements (As, Cu, Ni, Pb, and Zn) in Soils and Surface Waters among Montane, Upland Watersheds and Lowland, Urban Watersheds in New England, USA

Trace element biogeochemistry from soils to rivers is important for toxicity to aquatic ecosystems. The objective of this study was to determine whether trace element exports in contrasting watersheds are controlled by their abundance in soil, current land uses in the watershed, or geologic processes. Upland soils and river water samples were collected throughout the Deerfield watershed in southern Vermont and western Massachusetts and in the Quinebaug and Shetucket watersheds of eastern Connecticut. Soil concentrations were only an important predictor for dissolved Fe export, but no other trace element. Soil pH was not correlated with normalized dissolved exports of trace elements, but DOC was correlated with normalized dissolved Pb and Ni exports. The limited spatial and depth of soil sampling may have contributed to the poor correlation. Surprisingly, linear regressions and principal component analysis showed that human development was associated with higher soil trace metal concentrations but not significantly correlated with dissolved trace elements export. Instead, forest abundance was a strong predictor for lower Cu, Pb, and Zn soil concentrations and lower As, Fe, Ni and Pb dissolved exports across the watersheds. Dissolved exports of Al, K, and Si suggest that enhanced mineral dissolution in the montane watersheds was likely an important factor for matching or exceeding normalized pollutant trace element exports in more urbanized watersheds. Further studies are needed to evaluate subsurface/hyporheic controls as well as soil–surface water interface to quantify exchange and transport.

Badania stężeń metali śladowych w gruntach w pobliżu dróg o różnym natężeniu ruchu samochodowego

Motor transport affects the state of the natural environment and results in the accumulation of trace metals in roadside soils. The trace metal concentrations in roadside soils depend mainly on the distance from the road and the traffic intensity. The aim of the investigations was to determine the range of the environmental impact of the (Cracow-Zakopane) transport route and the effect of traffic intensity on the concentrations of trace metals in the soil. Three road sections differing in their traffic intensity were selected for this purpose. The concentrations of Cr, Cu, Ni, Pb and Zn in soil samples taken from a depth of 0-30 cm at a distance of 5, 10, 50 and 100 metres from the road were spectrophotometrically determined. The metal concentrations in the surroundings of the Cracow-Myślenice road carrying heavy traffic were found to be several times higher than the ones in the soils near the Łopuszna-Dursztyn local road with low traffic intensity. The largest differences in trace metal concentrations in the soils were found for nickel (four times higher concentrations along the Cracow-Myślenice road) at all the considered distances and for copper (three times higher) at the distances of 5 and 10 metres. In comparison with the reference areas, in the vicinity of the investigated roads the concentrations of Cr, Cu, Ni, Pb and Zn in the soil were found to be elevated. The fact that the concentrations of the trace metals decrease with increasing distance from the road's edge clearly indicates the traffic-related origin of the contaminants.

Evaluating the potential of topsoil magnetic pollution mapping across different land use classes

Soil magnetic measurements are used increasingly to estimate the impact of airborne, combustion-related particulate matter (PM) pollution in dense measurement grids. Although many studies have proven the potential of topsoil magnetic measurements in environmental monitoring, their application is not straightforward when factors such as parent material or land use have to be accounted for. Often, the influence of land use on the soil magnetic signal is circumvented by targeting forest soils, where deposited magnetic particles are best preserved in the topsoil. However, when large forests are absent, e.g. in densely populated areas or environments with more heterogeneous land use, this approach often impedes reliable and comprehensive spatial sampling. We evaluated if topsoil magnetic pollution mapping across different land use classes, against a homogeneous geological environment of sandy soils, could help increase the spatial reliability of results in regional scale surveys. Although detailed magnetic property analysis and evaluation of trace metal concentrations in soils on arable land, forest and pasture showed the impact of atmospheric pollution, topsoil susceptibility measurements did not allow delineating the magnetic footprint of PM pollution. Land use strongly influenced the distribution of magnetic particles through soil, and the evaluation of anomalous magnetic topsoil enhancement required the integration of downhole susceptibility soundings. We conclude that topsoil susceptibility mapping remains a useful tool to evaluate PM pollution impact, yet its application potential across land use classes is limited.

Structural Properties of Aqueous Solutions at the (100) and (101) Goethite Surfaces by Molecular Dynamics Simulation.

Trace metal concentrations in soils and sediments are often controlled by adsorption to iron oxides such as goethite in both natural and contaminated systems. Because of goethite's importance as an adsorbent, its interaction with aqueous solutions has been studied extensively. Nonetheless, despite the use of numerous analytical and computational tools, the properties of goethite-aqueous solution interfaces are not fully understood. In this research, we investigate the interaction of water and aqueous NaCl, MgCl2, and BaCl2 solutions ranging in concentration from 0.1 to 4 M, with two goethite surfaces, (100) and (101), using classical molecular dynamics simulation. In the past, the (100) surface has been studied the most because of its simplicity; however, goethite crystals in the environment exhibit other prominent surfaces like the (101) surface which may exhibit very different adsorption properties than the (100) surface. The (100) surface has three surface sites; one is an under-coordinated Fe3+ which interacts strongly with water affecting the interfacial water structure, another site remains deprotonated and forms a hydrogen bond to the only hydroxylated surface site. The (101) surface is terminated with five hydroxyl groups that do not interact as strongly with water as the under-coordinated Fe3+ ion and that form a more corrugated surface structure. As a result, the (101) goethite-solution interface exhibits less water structure, weaker electric double layer oscillations, and more inner-sphere ion adsorption, especially for Cl- and Ba2+ ions. The fundamental differences in interfacial properties for these surfaces suggest that the adsorption properties of one goethite surface cannot be averaged to represent goethite interfaces present in soils and sediments.

Effect of brewery spent diatomite sludge on trace metal availability in soil and uptake by wheat crop, and trace metal risk on human health through the consumption of wheat grain

Soil plays a crucial role in food safety as it determines the composition of food at the beginning of the food chain. However, the quality of soil resources in terms of their potential impact on human health caused by harmful elements is poorly understood in Ethiopia due to lack of reliable and appropriate experimental data. In this study, a field experiment was conducted to evaluate trace metal accumulation in soils amended with brewery spent diatomite sludge (BSDS) in comparison to control, recommended inorganic fertilizers (RIF) and integrated BSDS & RIF (BSDS:RIF). Trace metals uptake by wheat crop and the degree of soil contamination, and human health risk were investigated. BSDS application significantly increased the concentration of trace metals (Cu, Zn, Pb and Ni) in soil compared to that in the control, the RIF, and BSDS:RIF applications. It also significantly increased the concentration of Cu, Zn, Pb and Ni in the wheat grain compared to that in the control and the RIF, but the increase was not significantly different from that in BSDS:RIF amendment. All trace metal concentrations in soil and wheat grain (except Pb in wheat grain) were below the maximum permissible limits in some European countries of agricultural soils, and the maximum permissible limit of FAO/WHO. The degree of soil contamination from each of the treatments was below the maximum acceptable degree of contamination. The Health Risk Index (HRI) was <1 for all metals in all treatments. Thus, we conclude that consumption of wheat grain grown on soils amended with BSDS and BSDS:RIF has no human risks and has low likelihood of human exposure to trace metals.

Soil trace metal content does not affect the distribution of the hyperaccumulator Noccaea caerulescens in the Vosges Mountains (France)

Noccaea caerulescens is a pseudo-metallophyte known to hyperaccumulate Zn, Cd and Ni, and a model species for the study of the hyperaccumulation of trace metals. However, information about its ecology is rather scarce. The aim of this work was thus to determine if soil metal content was the main factor responsible for the distribution of N. caerulescens. During 4 years, the Vosges Mountains (north eastern France) were explored during the flowering season. Plants and their rooting soil were analyzed for their trace element content (Cd, Mn, Ni and Zn). The ecological amplitude of N. caerulescens was analyzed using Maximum Entropy Modelling (MaxEnt). Only five populations of the 67 recorded were found on metalliferous soils. All the recorded populations presented a Zn-hyperaccumulator phenotype, whereas only two presented a Cd and/or Ni-hyperaccumulator phenotype. The spatial distribution of mineralized areas did not explain the spatial distribution of the species. The MaxEnt distribution model suggested that the principle explanatory factors were the annual precipitation, soil use and underlying geology. Trace metal concentrations in soils are not the main drivers of N. caerulescens distribution in the Vosges Mountains. Instead, pedological and climatic factors along with recent human activity are the main factors of the colonization of the massif.

Assessment of the Spatial Distribution of Metal(Oid)s in Soils Around an Abandoned Pb-Smelter Plant.

Todos os Santos (All Saints) Bay area, NE-Brazil, is known for one of the most important cases of urban lead (Pb) contamination in the world. The main objective of this work was to assess and interpret the spatial distribution of As, Cd, Hg, Pb, and Zn in "background" soils of this environmentally impacted bay area, using a combination of geostatistical and multivariate analytical methods to distinguish between natural and anthropogenic sources of those metal(oid)s in soils. We collected 114 topsoil samples (0.0-0.2 m depth) from 38 sites. The median values for trace metal concentrations in soils (mg kg-1) followed the order Pb (33.9) > Zn (8.8) > As (1.2) > Cd (0.2) > Hg (0.07), clearly reflecting a Pb-contamination issue. Principal component analysis linked Cd, Pb, and Zn to the same factor (F1), chiefly corroborating their anthropogenic origin; yet, both Pb and Zn are also influenced by natural lithogenic sources. Arsenic and Hg concentrations (F2) are likely related to the natural component alone; their parent material (igneous-metamorphic rocks) seemingly confirm this hypothesis. The heterogeneity of sources and the complexity of the spatial distribution of metals in large areas such as the Todos os Santos Bay warrant, the importance of multivariate and geostatistical analyses in the interpretation of environmental data.

Bioaccumulation of Trace Metals in Selected Plants within Amin Bazar Landfill Site, Dhaka, Bangladesh

The presence of trace metals in landfill soil and plants pose a risk to the environment and human health. This study was conducted to determine trace metal concentrations in soil and different plant parts that grow in the Amin Bazar landfill, Bangladesh, to evaluate the possible human health risk on consumer. The collected soil and plant samples were analyzed for trace metals using a Flame Atomic Absorption Spectrophotometer. The mean concentrations of trace metal found in the soil were in the following order: zinc (Zn) > manganese (Mn) > lead (Pb) > copper (Cu) > chromium (Cr) > nickel (Ni). Considering all selected plant species, the mean concentrations of trace metals were in the following order: Zn > Ni > Mn > Cu. On the other hand considering all measured trace metals, the accumulation trend in plant species were in the following order: Carica papaya > Enhydra flactuans > Amaranthus gangeticus > Ipomoea aquatica > Sesbania cannabina > Musa sapientum. Pb and Cr were not accumulated in the studied plant species. Translocation factor (TF), bioaccumulation factor (BAF) and bioaccumulation coefficient (BAC) were calculated for the assessment of mobility of trace metals from root to shoot, soil to shoot and soil to whole plant, respectively. TF values showed that the plant species effectively translocate trace metals from roots to the shoots, suggesting that they are suitable for phytoextraction. According to BAF all studied plants were excluders for all metals except Ni, and according to BAC, all studied plants were hyperaccumulators of Ni. The daily metal intake and health risk index values of the studied metals, except of Ni, indicated that there is a relative absence of health risks associated with the ingestion of contaminated edible parts of plants.

Accumulation and distribution of trace metals within soils and the austral cordgrass Spartina densiflora in a Patagonian salt marsh

Concentrations of Cd, Cu, Fe, Pb, and Zn were determined in soils and in below- and above-ground structures of Spartina densiflora in a Patagonian salt marsh (San Antonio, Río Negro, Argentina). Also, the relationship between trace metal concentrations in soils and plants was investigated to improve our knowledge regarding the ability of this plant species to take up and accumulate trace metals from the soil. Our results indicate that, within the studied salt marsh, soil trace metal concentrations follow a decreasing concentration gradient toward the sea. They show moderate pollution and a potentially negative biological effect in one site of the salt marsh. While below-ground structures reflect the soil metal concentration pattern, this is not so evident in above-ground concentrations. Also, S. densiflora is able to absorb a limited amount of metals present in the soil, the soil bioaccumulation factor being lower in sites where soil metal concentration is higher.

Trace metal concentrations in Spartina densiflora and associated soil from a Patagonian salt marsh

The objectives of this study were to (i) assess in situ trace metal concentrations in soil and in Spartina densiflora in a Patagonian salt marsh (Rawson, Chubut, Argentina) and (ii) investigate the relationship between trace metal concentrations in soils and in plants to improve our knowledge regarding the ability of S. densiflora to take up and accumulate trace metals from the soil within its native region. Our results indicate that the soil and S. densiflora exhibit low metal concentrations in the Rawson salt marsh. S. densiflora accumulates Zn in below- and above-ground plant structures and Cr in below-ground parts. These results suggest at the time of this study there is scarce human impact associated with metals in the Rawson salt marsh.

Accumulation and risks of polycyclic aromatic hydrocarbons and trace metals in tropical urban soils

The study deals with the combined contribution of polycyclic aromatic hydrocarbons (PAHs) and metals to health risk in Delhi soils. Surface soils (0-5 cm) collected from three different land-use regions (industrial, flood-plain and a reference site) in Delhi, India over a period of 1 year were characterized with respect to 16 US Environmental Protection Agency priority PAHs and five trace metals (Zn, Fe, Ni, Cr and Cd). Mean annual ∑16PAH concentrations at the industrial and flood-plain sites (10,893.2 ± 2826.4 and 3075.4 ± 948.7 μg/kg, respectively) were ~15 and ~4 times, respectively, higher than reference levels. Significant spatial and seasonal variations were observed for PAHs. Toxicity potentials of industrial and flood-plain soils were ~88 and ~8 times higher than reference levels. Trace metal concentrations in soils also showed marked dependencies on nearness to sources and seasonal effects. Correlation analysis, PAH diagnostic ratios and principal component analysis (PCA) led to the identification of sources such as coal and wood combustion, vehicular and industrial emissions, and atmospheric transport. Metal enrichment in soil and the degree of soil contamination were investigated using enrichment factors and index of geoaccumulation, respectively. Health risk assessment (incremental lifetime cancer risk and hazard index) showed that floodplain soils have potential high risk due to PAHs while industrial soils have potential risks due to both PAHs and Cr.

Changes During a Century in Trace Element and Macronutrient Concentrations of an Agricultural Soil

Surface soil and subsoil samples collected in 2012 from a long-term agronomic experimental field at Cornell University were digested in concentrated nitric-perchloric acid and analyzed for macro- nutrient and trace element concentrations by ICP-OES (inductively coupled plasma optical emission spectrometry) and ICP-MS (inductively coupled plasma mass spectrometry). Archived soil samples, taken from the same field nearly a century earlier (1913), were simultaneously analyzed by the same methods to determine any temporal trends in acid- soluble soil elemental composition that might have resulted from agri- cultural practices and amendments or from diffuse pollution at this semirural site. Modest increases in surface soil concentrations of several macronutrients (P, Ca, Mg, K) were observed between 1913 and 2012, probably attributable to fertilizer and lime amendments. Most trace ele- ments showed either no significant concentration increase (Zn, Ba, Mn) or a small increase (Ni, Cr) in the surface soil. The greatest relative in- crease in surface soil trace metal concentrations was for arsenic (81%), followed by lead (40%) and cadmium (33%), although acid-soluble concentrations of these toxic metals in 2012 remained in the range con- sidered typical for background levels in uncontaminated agricultural soils of this region. Cadmium measured in acid digests by ICP-OES was shown to overestimate total soil Cd at these low near-background con- centrations, with both ICP-MS and a flame atomic absorption method using a preconcentration step for Cd in extracts providing results more consistent with known total soil Cd concentrations of certified standards.

Development of the Diffusive Gradients in Thin Films Technique for the Measurement of Labile Gold in Natural Waters

Gold is a precious metal that exists in most soils, sediments, and natural waters at extremely low concentrations (<1 μg/kg). The diffusive gradients in thin films (DGT) technique, used extensively for measuring trace metal concentrations in soils, sediments, and waters, has potential for geochemical exploration for gold, but has not been developed for this metal. This work investigates the possibility of measuring labile gold using DGT by introducing a new binding layer based on activated carbon. The performance of this new technique was assessed using gold(III) chloride in solution by: (1) determining the diffusion coefficient of gold(III) in hydrogels; (2) determining the uptake of gold(III) chloride by the new activated carbon binding layer; (3) determining an elution methodology for the binding layer and evaluating its efficiency; (4) assessing the capacity of the activated carbon binding layer to adsorb gold; (5) determining the effect of pH and ionic strength (as NaCl) on performance, and (6) assessing the selectivity of the new binding layer for gold. It was found that the diffusion coefficient of gold(III) increased as solution pH decreased. The diffusion coefficient also increased at high ionic strength (≥0.1 M NaCl). Accounting for these phenomena, the DGT technique behaved predictably under all tested conditions. The technique can potentially be used as a geochemical exploration tool for gold in soils and in aqueous environments, with method detection limits as low as 0.9 ng/L for a 7-day deployment.

Trace metals in the coastal soils developed from estuarine floodplain sediments in the Croatian Mediterranean region

Fertile soils in the River Neretva estuary were developed by fluvial sedimentation and deposition of the eroded soil material from the karst hills within the catchment. After extensive reclamation, two reclaimed land zones (fluvial terraces and lower-laying terraces) have been delineated, both used for agriculture. The main objectives of this study were to evaluate soil chemical and geochemical properties in reclaimed zones that differ mainly in topography, soil types and agricultural land use. The origin of the trace metals in the arable soils was studied using multivariate statistics, and interpolation maps of trace metals were produced using GIS and geostatistics. Soil trace metal concentrations do not exceed a threshold value established by the Croatian Government regulation, with exception of copper. Comparative analysis of the main soil properties and trace metal concentrations in the study area showed a pronounced spatial variation and differences between two reclaimed zones in soil organic matter content, bioavailable P and total concentrations of Cd and Cu. Factor analysis in the area of the lower-laying terraces showed grouping of bioavailable P and K, organic matter content and pH (negative loading) in the component associated mostly with the land use. In the area of the fluvial terraces, bioavailable P and total Cd were grouped in the same component that may be explained by the traditional small farm agriculture and overuse of mineral fertilizers. In the whole study area, processes of secondary salinization were determined, accompanied by the raised chloride and sodium concentration measured in the saturation soil extract.

Trace metal assessment in soils in a small city and its rural surroundings, Pensacola, FL, USA

This study assesses the origin and pollution of trace metals in surface soils in a region with contrasting land uses (urban vs. rural). Principal component analysis (PCA) reveals that Cr and Ni are predominantly of geogenic origin. These two trace metals are also the only ones with statistically significant correlations with soil particle size and organic matter content. Copper, Pb and Zn, and possibly Hg, are of anthropogenic origin, but their concentrations rarely reach levels described as strongly polluted by pollution indexes. The concentrations of these anthropogenic trace metals are statistically not different in urban and rural areas, except for Pb that is higher in the urban area. This general lack of a difference between the two land uses indicates that the influence of this small urban area on trace metal concentrations in soils is minor. Lead and Zn have the most, but still a modest number, of strongly polluted sites, mainly in an industrial part of the city. GIS analysis shows that, based on the pollution load index (PLI), overall concentrations of trace metals also reach their highest levels in that industrial area. These observations indicate that the influence of industry on trace metal pollution in soil exceeds that of other urban activities in the region. Local background concentrations were found to be very different from general crustal background concentrations. This demonstrates the importance of the careful selection of a background type in studies like this.

Assessing risk to human health from tropical leafy vegetables grown on contaminated urban soils

Fifteen tropical leafy vegetable types were sampled from farmers' gardens situated on nine contaminated sites used to grow vegetables for commercial or subsistence consumption in and around Kampala City, Uganda. Trace metal concentrations in soils were highly variable and originated from irrigation with wastewater, effluent discharge from industry and dumping of solid waste. Metal concentrations in the edible shoots of vegetables also differed greatly between, and within, sites. Gynandropsis gynandra consistently accumulated the highest Cd, Pb and Cu concentrations, while Amaranthus dubius accumulated the highest Zn concentration. Cadmium uptake from soils with contrasting sources and severity of contamination was consistently lowest in Cucurbita maxima and Vigna unguiculata, suggesting these species were most able to restrict Cd uptake from contaminated soil. Concentrations of Pb and Cr were consistently greater in unwashed, than in washed, vegetables, in marked contrast to Cd, Ni and Zn. The risk to human health, expressed as a ‘hazard quotient’ (HQ M), was generally greatest for Cd, followed successively by Pb, Zn, Ni and Cu. Nevertheless, it was apparent that urban cultivation of leafy vegetables could be safely pursued on most sites, subject to site-specific assessment of soil metal burden, judicious choice of vegetable types and adoption of washing in clean water prior to cooking.

Five-Year Change in Soil Profile Chemical Properties as Affected by Broiler Litter Application Rate

The broiler (Gallus gallus domesticus) industry generates large quantities of nutrient- and trace metal-enriched litter. Broiler litter (BL) is typically land applied as a nutrient source for forages. Continual annual BL applications can increase nutrient and trace metal concentrations in soil over time, creating the potential for negative environmental impacts. The objective of this study was to determine the long-term effects of BL application rate on soil profile chemical properties in a Captina silt loam (fine-silty, siliceous, active, mesic, Typic Fragiudult) with a history of BL applications. Broiler litter was applied annually at 0, 5.6, and 11.2 Mg of dry weight-based litter ha−1 during a 5-year period. Soil was sampled in 10-cm increments to 90 cm and characterized for pH, electrical conductivity, organic matter, dissolved organic C, P saturation, and acid-recoverable (P, K, Ca, Mg, S, Na, Fe, Mn, Zn, Cu, Al, As, Cd, Cr, and Se), Mehlich-3-extractable (P, K, Ca, Mg, Na, Fe, Mn, Zn, and Cu), and water-soluble (P, K, Ca, Mg, S, Na, Fe, Mn, Zn, Cu, Al, As, Cd, Cr, and Se) soil nutrient and trace metals. Soil nutrient and trace metal contents generally increased with continued BL application for 5 years in the Mehlich-3-extractable and water-soluble pools. Soil properties affected by litter treatment generally increased over time in the top 20 cm as litter rate increased. It seems that continued annual application of BL to soil with a history of BL application will continue to accumulate Mehlich-3-extractable and water-soluble soil nutrient and trace metals near the soil surface. A decrease in soil nutrient and trace metal contents when BL applications ceased generally did not occur. Therefore, it seems that decreases in most soil chemical property magnitudes caused by the cessation of BL applications will require more than 5 years and could continue to pose potential negative environmental consequences.

Microbial activities and trace element contents in an urban soil

Soil biological properties are influenced by trace metals. The main sources of these pollutants in the urban areas are industrial plants, power stations, domestic heating systems and motor vehicles. The aim of this work was to evaluate, in relation to distance from urban roads, soil trace metal concentrations (Pb, Cu, Cr, Cd and V) and their influence on C-microbial biomass as well as on soil respiration and enzyme activities (phosphatase glucosidase, galactosidase, xylanase, cellulase, trealase, protease and invertase). The samplings were carried out at four sites, along a route that goes from Giannone Street to Passionisti Street, two heavily travelled roads at two different times of the year (spring and autumn). Heavy metal contents and microbial activities were highest at the sites near the roads. The highest values of microbial activities were found in the inner site; here, on the contrary, the lowest concentrations of heavy metals were measured. Significant and negative correlations were found between microbial activity and heavy metal contents.