Toxic metal contamination and distribution in soils and plants of a typical metallurgical industrial area in southwest of China

In this work, the total and each fraction concentration of toxic metals (Pb, Zn, Cu and Cd) in soils as well as in plants from a typical metallurgical industrial area in southwest of China were determined. The obtained experimental results demonstrated that the total toxic metal content in contaminated soils was in the order of Zn > Pb > Cu > Cd. Modified microwave-assisted extraction showed that the distributions of each fraction of toxic metals in soils were different and some soil properties may play a role in the fraction distributions. The content of Cu, Zn, Cd and Pb in different vegetables ranged from 9.82 ± 1.02 to 39.3 ± 1.13 mg kg^?1, 1,321 ± 10.50 to 3,153 ± 11.30 mg kg^?1, 4.47 ± 0.21 to 18.9 ± 0.37 mg kg^?1 and 28 ± 1.2 to 102 ± 1.5 mg kg^?1, respectively. And the accumulation of toxic metals in plants was in the order of Cd > Zn > Cu > Pb. The bioconcentration factor (BCF) values of Cd, Zn, Cu and Pb in the different tissues of plants were in the range of 0.03–0.43, 0.027–0.35, 0.014–0.12 and 0.004–0.051, respectively. The distribution of each toxic metal in plants indicated that the ability for plants to accumulate toxic metals in different tissues followed the sequence of leaf > stem.     

Pollution assessment and source apportionment of arsenic,lead and copper in selected soils of Khuzestan Province,southwestern Iran

Due to the intensified industrial activities and excessive application of agrochemicals and organic waste materials over the last few decades, there is a great concern about the accumulation of potentially toxic elements (PTEs) in soils from north of Khuzestan Province, southwestern Iran. Therefore, a comparative study with a total number of 300 composite soil samples (0–10 cm) from industrial, urban, agricultural, forest, and rangelands; and 26 samples from the major types of soils parent materials was conducted to examine sources, pollution status, and the effects of soil properties, land use types, and the local lithology on the total concentrations of As, Pb, and Cu (measured using atomic absorption spectrometer (AAS) equipped with graphite furnace) in the soils studied. The mean values of Pb and Cu were 12.2?±?4.6 and 13.5?±?7.6 mg kg^?1, respectively, slightly higher than the background values of the study area, but lower than the guideline values of Iranian Environmental Quality Standard for Soils. However, the mean values of As (1.72?±?1.15 mg kg^?1) were lower than both background values and the guideline values of Iranian Environmental Quality Standard for soils. The greatest values of the geo-accumulation index (I _geo), enrichment factor (EF), and the concentrations of Pb, Cu, and As were arranged as industrial > urban > agriculture > rangelands = forest land uses. The results also indicated that concentrations of all PTEs were greater in soils as compared to those in parent materials. Using principal component analysis (PCA), the origin of Cu and Pb with moderate to high enrichments was attributed to the inputs from both natural and anthropogenic sources. However, As was found to be mainly influenced by lithogenic origin.     

Characterization and low-cost treatment of an industrial arid soil polluted with lead sulfide in northern Chile

Lead (Pb) dust exposure can have detrimental environmental and human health effects. Improperly enclosed stockpiles of Pb concentrates can cause dust emissions, subsequent pollution of the soil and environmental risk. The aim of this work was to study Pb form, distribution and immobilization (by using eggshell and seashell) in an industrial arid soil near a storage area of Pb mineral concentrates in northern Chile. High amounts of sulfur (S; 9900 mg kg^?1) and Pb (6530 mg kg^?1) were found in the polluted soil. The energy-dispersive X-ray spectroscopy analysis revealed a lead sulfide (PbS: galena). Metallic Pb particles, which were between 41 and 46 µm, were identified in the soil. After eggshell and seashell (20%) were applied, the soil pH increased from 6.0 to 7.84 and 8.07, respectively. In the studied soil, the leaching test showed a 59 mg L^?1 average Pb extractable concentration. After 240 days, extractable Pb by toxicity characteristics leaching procedure decreased to 4.79 mg L^?1 (93.3%) with the application of seashell at 20% compared with a decrease of 33.33 mg L^?1 (53.6%) using eggshell. Pb in the polluted soil was mainly found in the exchangeable fraction (66%), followed by the reducible (24%), residual (7%) and oxidizable (6%) fractions. According to the risk assessment code, the contaminated soil before treatment was classified as very high risk. Adding eggshell (20%) and seashell (20%) decreased the exchangeable fractions to 39 and 35%, respectively. Applying these liming materials achieved Pb immobilization in the soil, but the soil remained in the high environmental risk category. We conclude that the application of seashell waste, resulting from high aquaculture activity, opens an interesting window to the treatment of contaminated arid soils.     

Phytoremediation assessment of native plants growing on Pb–Zn mine site in Northern Tunisia

Pollution by heavy metals presents an environmental concern, and their toxicity threats soil, water, animals and human health. Phytoremediation can be used as a solution to remediate contaminated soils. The aim of this study was to identify native plants collected from tailings: material of Pb–Zn mine sites of Fedj Lahdoum and Jebel Ressas (two abandoned mines located, respectively, in the northwest of Tunisia and in the south of Tunis City). The tolerance of plant to heavy metals (lead, zinc and cadmium) is evaluated. Soil samples were collected and analyzed for Pb, Zn and Cd concentration. The total soil Pb, Zn and Cd are, respectively, reached 6132 mg kg^?1, 11,052 mg kg^?1 and it doesn’t exceed 479 mg kg^?1 for Cd. The highest content of Zn in plants was detected in shoots of Rumex bucephalophorus (1048 mg kg^?1), and the highest Pb concentration was detected in roots of Chrysopogon zizanioides (381 mg kg^?1), while for Cd Silene colorata it accumulated the highest content in roots (51 mg kg^?1). From all plants, only 12 have a translocation factor for Pb which is higher than one. Among all plants, only 17 have a translocation factor that is higher than one for Zn, while for Cd only 13 plants indicate TF > 1. As for the biological absorption coefficient, all samples indicate a rate which is lower than one. These plants can be primarily hyper accumulators and useful in remediation of lead- and zinc-contaminated soils after further biochemistry researches in mechanism of accumulation and translocation of heavy metals in plants.     

Multivariate statistical analysis of heavy metals in foliage dust near pedestrian bridges in Guangzhou, South China in 2009

The heavy metal content of particulate matter was investigated in the city of Guangzhou in southern China. Samples of urban foliage near 36 pedestrian bridges were analyzed to determine their Zn, Pb, Cu, Cr, V, Ni, and Co contents after digestion in a mixture of strong acids composed of HNO₃, HCl, HF, and HClO₄. The results revealed a severe heavy metal pollution compared with the background levels in Chinese soils, except for Co and V. The mean concentrations of Zn (1,024 mg kg^?1), Pb (233 mg kg^?1), Cu (203 mg kg^?1), Cr (118 mg kg^?1), V (41.9 mg kg^?1), Ni (41.4 mg kg^?1), and Co (11.3 mg kg^?1) in urban dust were higher than the reference levels, and were highest in samples located near high-traffic areas. Multivariate statistical methods (correlation analysis, principal-components analysis, and clustering analysis) were used to identify the possible sources of the metals. Three main pollutant sources are assigned: Zn, Cu and Ni levels were strongly correlated and were possibly related to combustion processes and vehicles; Pb, Cr and Co were mainly derived from traffic sources, combined with soil sources; and V mainly originated from natural sources.     

Chelate enhanced phytoremediation of soil containing a mixed contaminant

Greenhouse tests were conducted to study the effect of chelates on the phytoextraction of cadmium and lead, and the rhizodegradation of used engine oil present as a mixed contaminant in a sandy soil. Indian mustard plants were grown in test pot soil for 30 days and chelates ethylenediamine tetraacetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS) were individually applied to the test soil. The soil was spiked earlier with 50 mg kg^?1 of CdCl₂, 500 mg kg^?1 of PbCl₂ and 500 mg kg^?1 of used engine oil to form the mixed soil contaminant. At the same concentration of chelates, EDTA was found to be more effective than EDDS in increasing the concentration of metal contaminants Cd and Pb in the plant. Compared to EDDS, EDTA was also more effective in promoting rhizodegradation of the organic contaminant formed by used engine oil. The study demonstrated that the application of chelates to soils containing mixed contaminants such as heavy metals (Cd and Pb) and organics (used engine oil) can simultaneously assist metal accumulation at higher concentrations in the biomass of Indian mustard plant and also reduce the amount of used engine oil in the soil through rhizodegradation.     

The use of multivariate statistical analysis of geochemical data for assessing the spatial distribution of soil contamination by potentially toxic elements in the Aljustrel mining area (Iberian Pyrite Belt,Portugal)

Aljustrel mine is located in SW Portugal, in the western sector of the Iberian Pyrite Belt. The Aljustrel village was developed around the exploitations of massive polymetallic sulphides that occur in the area (4 orebodies mined, 2 in exploration phase). The pyrite ore was extensively exploited from 1850 to 1993, when production was discontinued. A mining restart occurred in 2008, only during a few months. The objectives of the study were to assess the levels of soil contamination, to determine associations between the different chemical elements and their spatial distribution, as well as to identify possible sources of contamination that can explain the spatial patterns of soil pollution in the area. Principal component analysis combined with spatial interpretation successfully grouped the elements according to their sources and provided evidence about their geogenic or anthropogenic origin. From this study, it is possible to conclude that soils around Algares/Feitais tailing deposits, Estéreis and Águas Claras mine dams and S. João mine show severe contamination. The highest concentrations of As (up to 3,936 mg kg^?1) and certain heavy metals (up to 321.7 mg kg^?1 for Bi, 5,414 mg kg^?1 for Cu, 20,000 mg kg^?1 for Pb, 980.6 mg kg^?1 for Sb, and 22 mg kg^?1 Cd) were obtained near Algares area while the highest concentration of Cd (up to 61.6 mg kg^?1) and Zn (up to 20,000 mg kg^?1) were registered in samples collected in the S. João area. The highest pollution load index (>4.0) was recorded at the Algares area where the metal concentrations exceed typical soil background levels by as much as two orders of magnitude.     

Lead enrichment, adsorption and speciation in urban garden soils under long-term wastewater irrigation in northern Nigeria

Unsafe lead (Pb) concentrations in leafy vegetables raised in urban and peri-urban agricultural production systems have been reported across cities in Northern Nigeria, even though Pb concentrations in soils are within regulatory safe levels. This study examined the soil enrichment, adsorption and chemical species of Pb in urban garden fields irrigated with untreated wastewater at three industrial locations in Kano, northern Nigeria. Total Pb in the soil profiles ranged from 9 to 91 mg kg^?1 and decreased rapidly from the surface to the subsurface layer, but attaining nearly constant concentration at depth ≥1.2 m in the profiles. The potentially labile Pb maintained fairly constant concentration with depth up to 0.9 m, but decreased fairly rapidly with depth thereafter. There was a significant Pb enrichment of the soils, extending up to 30–60 cm depth in the soil profiles. The adsorption of Pb by the soils increased drastically with pH, and attained maximum adsorption at pH ≥ 7.0 in the surface layer, and at pH ≥ 6 in the subsurface layer. The surface soils adsorbed between 85 and 97 % of added Pb at pH ≤ 5. Free Pb²⁺ activities in soil solution accounted for between 46 and 87 % at pH 5–7 of total dissolved Pb (Pb_T). The quantifiable chemical species of Pb in solution consisted mainly of PbOH⁺, PbSO ₄ ^· , PbCl⁺ and PbOH ₂ ^· which accounted for between 0.9 and 26 % of Pb_T in soil solution at pH ≥ 5.0, but declining to between 0.1 and 2.1 % at pH ≥ 7.5. There was no apparent equilibrium between Pb²⁺ activities and known Pb-compounds in the soils. It was concluded from the data that reports of excess Pb concentrations in leafy vegetables raised in these soils are consistent with high free Pb²⁺ activities maintained in soil solution by these predominantly sandy-textured soils.     

Chemical stabilization of metals in the environment: a feasible alternative for remediation of mine soils

Initial risk assessment characterization carried out in a tailing pond, called “El Lirio”, came from metal mining showed that these soils have low fertility; low amounts of nitrogen, organic carbon, phosphorous, and carbonates; and high concentrations of total metals (10,719 mg Zn kg^?1, 2,821 mg Pb kg^?1, and 30 mg Cd kg^?1), diethylenetriaminepentaacetic acid (DTPA)-extractable metals, and water-soluble metals, which suggest an urgent need for remediation. Different amendments have been selected, including three anthropogenic wastes: pig manure, sewage sludge, and lime; all were added to the constructed plots in the mine pond. The objectives were to: (1) reduce acid mine drainage, metal mobilization, and toxicity and (2) provide nutrients which enable plant establishment. Results showed an increase in pH, electrical conductivity, total nitrogen, organic carbon, and equivalent calcium carbonate contents. Although water- and DTPA-extractable Zn, Pb, and Cd were reduced, there was an increment in DTPA- and water-extractable Cu due to the addition of organic matter. The amendments also enhanced the establishment of plants. This study constitutes the first stage of a successful remediation programme that can be applied in similar mining areas. The chemical stabilization of metals is a cost-effective alternative for remediation of mine areas in SE Spain.     

Mineral components in a peat deposit: looking for signs of early mining and smelting activities in Silesia–Cracow region (Southern Poland)

The results of investigations (SEM/EDS and AAS) of a peat deposit, spanning 13,000 years of peat accumulation, are shown. The peat deposit is located in a region of shallow occurrence of Zn–Pb ores, near Tarnowskie Góry town, within the Cracow–Silesia district (southern Poland). Exploitation of lead, silver and iron during the medieval times (Twelfth and thirteenth century) was confirmed by historical documents whereas there are no unambiguous data showing that there was metal mining during the Romanian or earlier times in the region. The peat deposit is located within the influence of atmospheric Pb and Zn emission from a nearby Zn–Pb smelter. Two vertical peat profiles were investigated (120 and 140 cm depth of profile) showing variable concentrations of Zn up to 713 mg kg^?1, Pb up to 317 mg kg^?1, Cd up to 13 mg kg^?1 and Tl up to 31 mg kg^?1. The highest concentrations were recorded for the uppermost peat layers. SEM and EDS investigations revealed the occurrence of metalbearing, submicroscopic mineral components: Fe, Mn, Ti and Zn oxides and Zn and Pb carbonates. The top layer of the deposit contained Zn, Pb and Cd sulphides. The occurrence of aggregates of Au–Ag, Cu–Zn and Au–Ag–Cu alloys can be possibly related to pre-historical mining and smelting or be explained by geochemical transformations. The preservation of carbonates and oxides in the peat is discussed, indicating a generally neutral to alkaline peat water chemistry and maintenance of an oxidized environment in the fen.     

Soil contamination by metals with high ecological risk in urban and rural areas

Industrial development, intensive agriculture and fast urbanization have caused the metal contents of soils to increase to many times the allowable limits. To assess this impact on urban and rural soils, we quantified the Cd, Cr, Cu, Pb, Ni and Zn contents of 258 soil samples from the Recife metropolitan region (RMR). The objectives of the study were to estimate the probability of ecological risk, to determine the spatial pattern of the metals’ accumulation in the soil and to identify potential sources for the metals using a multivariate geostatistical approach. Mean concentrations of Zn, Cr, Pb, Cu, Ni and Cd in soils were 65.2, 17.9, 16.5, 12.8, 6.3 and 1.5 mg kg^?1, respectively. The results demonstrated that the Cd was anthropogenic in origin, the Cr and Ni were lithogenic (natural) in origin and the Cu, Pb and Zn were mixed in origin. Cd contaminated 91% of the samples; the median content of Cd (1.4 mg kg^?1) was three times the quality reference value for soil. The Cd contents of sugarcane fields exceeded the allowable limit (3.0 mg kg^?1) for agricultural areas. The spatial variability of the metals in the RMR showed that metallurgy, cement production, vehicle exhaust and vehicular traffic were the main sources of metals in urban areas, while phosphate-based fertilizers were the main sources in rural areas. More than 80% of the metropolitan region surveyed in the study was at moderate to high ecological risk.     

An evaluation of trace metal distribution and environmental risk in sediments from the Lake Kalimanci (FYR Macedonia)

Pollution from mining activities is a significant problem in several parts of the Republic of Macedonia. A geochemical study of the surficial sediments of Lake Kalimanci in the eastern part of the Republic of Macedonia was carried out to determine their elemental compositions and to evaluate the pollution status of lake sediments by employing an enrichment factor (EF). The major and trace element contamination in surficial lake sediments was studied to assess the effects of metalliferous mining activities. The mean concentrations of major elements (wt%) Si 23.5, Al 7.9, Fe 6.6, Mg 1.3, Ca 3.8, Na 1.1, K 2.3, Ti 0.4, P 0.2, Mn 0.6 and trace elements ranged within Mo 1.0–4.6 mg kg^?1, Cu 144.4–1,162 mg kg^?1, Pb 1,874–16,300 mg kg^?1, Zn 2,944–20,900 mg kg^?1, Ni 21.7–79.3 mg kg^?1, Cd 16.5–136 mg kg^?1, Sb 0.6–3.6 mg kg^?1, Bi 3.0–24,3 mg kg^?1 and Ag 1.4–17.3 mg kg^?1. The EF ranged within 0.12–590.3. Among which, Cd, Pb, Zn and As have extremely severe enrichment. The data indicate that trace elements had extremely high concentrations in Lake Kalimanci surficial sediments owing to the anthropogenic addition of contaminants.     

Lead in drinking water and human blood in Riyadh City, Saudi Arabia

Concentrations of lead (Pb) in domestic water and blood plasma in the Olya and Al-Batha regions of Riyadh City, Saudi Arabia were correlated (r ²?=?0.03, p?<?0.0072 and r ²?=?0.37, p?<?0.00092, respectively). Greater concentrations of Pb in domestic water of Olya and Al-Batha (0.0119 and 0.03 mg/l, respectively) were greater than concentrations of Pb in bottled water and was also greater than the concentration of 0.01 mg Pb/l recommended by both the World Health Organization US Environmental Protection Agency (USEPA). In Al-Batha, 52.2 % of the population had concentrations of Pb in blood that exceeded 10 μg Pb/dl, which is the concentration used by USEPA to classify people as being at risk from effects of Pb. In Al-Batha, 17.5 and 22.5 % of the population exceeded 20–40 and >40 μg Pb/dl, respectively. In Olya, 37 and 10 % of the population had concentrations of Pb in blood that exceeded 10 and 20–40 μg Pb/dl, respectively, while none of the concentrations of PB exceeded 40 μg Pb/dl.     

Lead isotopic ratios in source apportionment of heavy metals in the street dust of Kolkata,India

Street dust from 29 locations, in some of the busiest parts of north and south Kolkata, was analysed for heavy metal composition. The decreasing order of average metal concentrations (mg kg^?1) found was Mn (390) > Pb (380) > Zn (300) > As (96) > Cu (61) > Cr (40) > Co (13) > Ag (2.1). The heavy metal composition of the Kolkata dust was compared with reported data for other cities. Enrichment factors of Pb and As were high. Multivariate statistical analysis of the heavy metals and analysis of lead isotopic ratios of the dust revealed a predominant anthropogenic influence in the contamination. The range of lead isotopic ratios found in the dust was between 0.8789 and 0.8998 with a mean Pb concentration of 383 mg kg^?1. The three Pb isotope plots of street dust, diesel and rainwater clustered linearly, while coal did not fit into this trend. The highest 207/206 lead isotopic ratio obtained was from diesel with a mean value of 0.9015, followed by the rainwater sample. The application of the binary mixing model showed that about 66.86% of lead contamination in the street dust was sourced from the atmosphere. The two components extracted by the principal component analysis explained 64.34% of the total variance. Vehicular and industrial emissions appeared to be an important contributor to the accumulation of heavy metals in the dust. The health risk assessment study of the dust indicated carcinogenic risk associated with As and Cr.     

Uptake of hazardous elements by spring onion (<Emphasis Type="Italic">Allium fistulosum</Emphasis> L.) from soil irrigated with different types of water and possible health risk

Bio-concentration of elements such as Mo, As, Se, Fe, Cu, Zn, Ni and Pb was analyzed in spring onion (Allium fistulosum L.) in three different locations of central Punjab, Pakistan. At location GW, relatively low level of hazardous elements was found in spring onion, suggesting that groundwater is a safe source of water for irrigating food crops. The pH of soil at wastewater irrigation was found less acidic (pH 7.4) than the other sites. The range of concentration in the different samples of spring onion was as follows: 6.15–8.16 mg kg^?1 for Mo, 2.77–4.28 mg kg^?1 for As, 0.395–0.705 mg kg^?1 for Se, 36.73–48.17 mg kg^?1 for Fe, 10.58–16.26 mg kg^?1 for Cu, 28.87–39.79 mg kg^?1 for Zn, 6.66–8.75 mg kg^?1 for Ni and 4.33–6.09 mg kg^?1 for Pb, respectively. High bio-concentration of Zn (15.37) from soil to spring onion was found at canal water irrigated location. The estimated daily intake of metal for spring onion was less, but the health risk index was higher than 1 for Mo, As, Cu, Pb and Ni, respectively. This was due to higher proportion of spring onion in diet, which consequently increased the health risk index for metals. Therefore, it is recommended to avoid growing vegetables in untreated urban and rural wastewater containing elevated amounts of metals.     

Assessment of heavy metal contamination levels of street dust in the city of Lublin,E Poland

Heavy metals are constantly emitted into the environment and pose a major threat to human health, particularly in urban areas. The threat is linked to the presence of Cd, Cr, Cu, Ni, Pb, and Zn in street dust, which consists of mineral and organic particles originating from the soil, industrial emitters, motor vehicles, and fuel consumption. The study objective was to determine the level of street dust contamination with trace metals in Lublin and to indicate their potential sources of origin. The analyses were carried out with an energy-dispersive X-ray fluorescence spectrometer. The sampling sites (49) were located within the city streets characterised by varying intensity of motor traffic. The following mean content values and their variation (SD) were determined: Cd: 5.1?±?1.7 mg kg^?1, Cr: 86.4?±?23.3 mg kg^?1, Cu: 81.6?±?69.2 mg kg^?1, Ni: 16.5?±?3.9 mg kg^?1, Pb: 44.1?±?16.4 mg kg^?1, and Zn: 241.1?±?94.6 mg kg^?1. The level of pollution was assessed with several widely used geochemical indices (geoaccumulation index, enrichment factor, pollution index, index of ecological risk, and potential ecological risk index). For most of the indices, the mean (median) values are arranged in the following manner: Zn?>?Cu(or Cd)?>?Pb?>?Ni?>?Cr. In general, street dust in Lublin does not show pollution with Cr, Ni, and Pb. I_geo and EF indices show moderate levels for Cu, Cd, and Zn; their presence in street dust is linked with anthropogenic factors (motor traffic). A significant threat is posed by Cd, and more than half of the samples show considerable pollution with cadmium (median for the index of ecological risk: 151). The spatial pattern of indices and the results of statistical analyses (CA, PCA) indicate three groups of elements: (1) Cr and Ni: natural origin; (2) Pb: mixed origin; and (3) Cd, Cu, and Zn: anthropogenic origin (mainly motor vehicle traffic). Higher content values for metals of anthropogenic origin in street dust indicate that it is a source of pollution of soil and air in the city.     

Assessment of heavy metals in sediment and in suspended particles affected by multiple anthropogenic contributions in harbours

La Goulette, Rades and Sidi Bou Said harbours are considered as the most important commercial and tourist ports in the Gulf of Tunis. They are located on the northeast coast of Tunis and receive industrial and municipal wastewaters from Tunis city. The contamination level of copper, lead, zinc, cadmium, manganese, iron, total nitrogen and total organic carbon in the surface sediments was assessed on the basis of the enrichment index factors and corresponding to sediment quality guidelines. The results revealed moderate to highly elevated concentrations near to the sites of intense industrial, shipping and/or commercial activities suggesting a direct influence of these sources. In winter and summer, concentrations varied for cadmium, 0.28–1.40 mg kg^?1; lead, 18–217 mg kg^?1; zinc, 87–459 mg kg^?1; copper, 8–121 mg kg^?1; manganese, 208–254 mg kg^?1; and for iron, 24–40 g kg^?1. Furthermore, in summer the concentration of the total organic carbon and the total nitrogen contents range between 4.3–6.5 % and 0.06–0.49 % with an average value of 5.9 and 0.15 %, respectively. Whereas, in winter, total organic carbon and the total nitrogen concentrations varied between 2.3–9.6 % and 0.03–0.22 % with an average value of 6.1 and 0.14 %, respectively. The levels of lead, copper, zinc and iron in suspended particulate matter content range between 3.1–27.5 mg kg^?1; 0.4–11.7 mg kg^?1; 1–1.5 mg kg^?1; 1.2–1.7 g kg^?1, respectively. This study revealed that heavy metals pollution is mainly localized in the commercial (Rades) and fishing (La Goulette) harbours and not in the yachting (Sidi Bou Said) harbour.     

Role of rhizosphere and soil properties for the phytomanagement of a salt marsh polluted by mining wastes

The goal of this study was to evaluate the soil properties and their modifications within the rhizosphere of spontaneous vegetation as key factors to assess the phytomanagement of a salt marsh polluted by mining wastes. A field survey was performed based on a plot sampling design. The results provided by the analyses of rhizospheric soil (pH, electrical conductivity (EC), organic carbon, total nitrogen, etc.) and metal(loid)s’ phytoavailability (assessed by EDTA) were discussed and related to plant metal uptake. The averages of pH and EC values of the bulk soil and rhizospheric samples were in the range of neutral to slightly alkaline (pH 7–8) to saline (>2 dS m^?1), respectively. Heavy metal and As concentrations (e.g. ~600 mg kg^?1 As, ~50 mg kg^?1 Cd, ~11,000 mg kg^?1 Pb) were higher in the rhizosphere for both total and EDTA-extractable fraction. Phragmites australis uptaked the highest concentrations in roots (e.g. ~66 mg kg^?1 As, ~1,770 mg kg^?1 Zn) but not in shoots, for which most of plant species showed low values for Zn (<300 mg kg^?1) but not for Cd (>0.5 mg kg^?1) or Pb (~20–40 mg kg^?1). Vegetation distribution in the studied salt marsh looked to be more affected by salinity than by metal pollution. The free availability of water for plants and the incoming nutrient-enriched effluents which flow through the salt marsh may have hindered the metal(loid)s’ phytotoxicity. The phytomanagement of these polluted areas employing the spontaneous vegetation is a good option in order to improve the ecological indicators and to prevent the transport of pollutants to nearby areas.     

Impact of parent rock and topography aspect on the distribution of soil trace metals in natural ecosystems

The concentration and dynamic of soil trace metals in natural ecosystems, in particularly, is dependent on the lithology of parent rock as well as topography and geopedological processes. To ascertain more knowledge for this dependency, soils on three parent rocks involving peridotite, pegmatite, and dolerite in two contrasting topography aspects were investigated. The total values of Fe, Mn, Zn, Cu, and Ni were determined and compared for different soil pedons. The concentration of Fe, Mn, and Ni were highest in soils developed from peridotite (127, 1.8 g kg^?1, and 218 mg kg^?1, respectively), intermediate in soils derived from dolerite (81, 1.3 g kg^?1, and 166 mg kg^?1, respectively), and least in soil developed from pegmatite (50, 0.23 g kg^?1, and 20 mg kg^?1, respectively). The values of Zn and Cu, originated from different parent rocks, were in order of dolerite (78 mg kg^?1) > peridotite (77 mg kg^?1) > pegmatite (28 mg kg^?1) and pegmatite (121 mg kg^?1) > peridotite (111 mg kg^?1) > dolerite (28 mg kg^?1), respectively. For most of the studied pedons, profile metals distribution differed among the soils: The values of Fe, Cu, and Ni were enriched in the cambic horizons mainly as result of release, mobilization, and redistribution of the studied metals during geopedological processes, whereas those of Zn and Mn were concentrated in the surface horizons. Probably due to greater weathering rate of trace metal-bearing rocks on north-facing slope, the content of the trace metals along with the geoaccumulation index (I _geo) and the degree of soil contamination (C _d) were higher than on south-facing slope. Based on assessment of soil pollution indices, the soils were categorized as unpolluted [I _geo ≤ 0 (class 0)], unpolluted to moderately polluted levels [0 < I _geo < 1 (class 1)], and very low [C _d < 1.5 (class 0)] to low degree of contamination [1.5 < C _d < 2 (class 1)].     

Effects of natural and calcined poultry waste on Cd, Pb and As mobility in contaminated soil

The reuse of waste materials as soil additives could be a welcome development in soil remediation. The mobility of Cd, Pb and As in a contaminated soil was investigated using natural and calcined poultry wastes (eggshell and chicken bone), CaCO₃ and CaO at different application rates (0, 1, 3 and 5 %). The chemical composition accompanied with mineralogical composition indicated that CaCO₃ and CaO were the major components in natural and calcined eggshells, respectively, while hydroxyapatite (HAP) dominated the natural and calcined chicken bones. The results showed that soil pH tended to increase in response to increasing application rates of all soil additives. The effectiveness of the additives in reducing Cd, Pb and As mobility was assessed by means of chemical extractions with 0.1 N HCl for Cd and Pb or 1 N HCl for As, according to Korean Standard Test (KST) method. Both calcined eggshell and chicken bone were equally effective with CaO or CaCO₃ in reducing the concentration of 0.1 N HCl-extractable Cd from 6.17 mg kg^?1 to below warning level of 1.5 mg kg^?1, especially at the highest application rate. The application of calcined eggshell, CaO and CaCO₃ also decreased the concentration of 0.1 N HCl-extractable Pb from 1,012 mg kg^?1 to below warning level of 100 mg kg^?1. The Pb concentration decreased significantly with an increasing application rate of chicken bone, but remained above warning level even at the highest application rate. On the contrary, natural and calcined chicken bones led to a significant increase in the mobility of As when compared with the control soil. These findings illustrate that calcined eggshell in particular is equally effective as pure chemical additives in stabilizing Cd and Pb in a contaminated agricultural soil. The presence of As in metal-contaminated soils should be taken into consideration when applying phosphate-containing materials as soil additives, because phosphate can compete with arsenate on adsorption sites and result in As mobilization.