A Laboratory Study on Revegetation and Metal Uptake in Native Plant Species from Neutral Mine Tailings

Lygeum spartum, Zygophyllum fabago and Piptatherum miliaceum are typical plant species that grow in mine tailings in semiarid Mediterranean areas. The aim of this work was to investigate metal uptake of these species growing on neutral mine tailings under controlled conditions and their response to fertilizer additions. A neutral mine tailing (pH of soil solution of 7.1–7.2) with high total metal concentrations (9,100 and 5,200 mg kg^?1 Zn and Pb, respectively) from Southern Spain was used. Soluble Zn and Pb were low (0.5 and <0.1 mg l^?1, respectively) but the major cations and anions reached relatively high levels (e.g. 2,600 and 1,400 mg l^?1 Cl and Na). Fertilization caused a significant increase of the plant weight for the three species and decreased metal accumulation with the exception of Cd. Roots accumulated much higher metal concentrations for the three plants than shoots, except Cd in L. spartum. Shoot concentrations for the three plants were 3–14 mg kg^?1 Cd, 150–300 mg kg^?1 Zn, 4–11 mg kg^?1 Cu, and 1–10 mg kg^?1 As, and 6–110 mg kg^?1 Pb. The results indicate that neutral pH mine tailings present a suitable substrate for establishment of these native plants species and fertilizer favors this establishment. Metal accumulation in plants is relatively low despite high total soil concentrations.     

华南大宝山矿周边土壤和大豆的重金属污染

Concentrations of Pb, Cd, Cu, Zn, Cr and Ni in soybean (Glycine max L.) grown near the Dabaoshan Mine were investigated, and their potential risk to the health of inhabitants was estimated. In the Fandong (FD) and Zhongxin (ZX) villages, which are near the Dabaoshan mineral deposit, concentrations of Pb (0.34 mg kg^-1 for FD), Cd (0.23 mg kg^-1 for ZX) and Cr (1.14 and 1.75 mg kg^-1 for FD and ZX, respectively) in the seeds of soybean exceeded the tolerance limit set by Chinese standards. The estimated daily intakes (EDIs) from consumption of soybean seeds for FD inhabitants were 0.570, 0.170, 38.550, 142.400, 1.910 and 14.530 μg d^-1 kg^-1 boby weight for Pb, Cd, Cu, Zn, Cr and Ni, respectively. Our results indicate that soybeans grown in the vicinity of the Dabaoshan Mine accumulate some metals, and the seeds pose a potential health risk to the local inhabitants.     

Heavy Metal Content in Lettuce Plants Grown in Biosolids Compost

The objective of this work was to evaluate the affects of the application of composted biosolids on the accumulation of heavy metals (Cd, Cu, Ni, Pb and Zn) in lettuce leaves. Pots containing different proportions (0 to 100%) of composted biosolids were used to grow lettuce plants under greenhouse conditions. Dry and fresh weight, leaf area and Cd, Cu, Ni, Pb and Zn uptake were determined after harvest. It was found that the dry and fresh matter productions of the plants were significantly lower in the control treatment. The addition of composted biosolids caused a 20 and 40% increase in biomass accumulation. Cd and Pb concentrations in leaves were below detection limits (0.05 mg kg^?1) in all treatments. Zn concentration in leaves increases as compost proportion decreases, ranging from 57.2 to 80.4 mg kg^?1. Composted biosolids application increased the Cu and Ni plant concentrations, ranging from 5.1 to 9.8 mg Cu kg^?1 and 2.3 to 3.7 mg Ni kg^?1. In all treatments the proportions of heavy metals in plants were below the international standards of toxicity. The results allow us to suggest that, in short-term applications, composted biosolids could be used as soil amendment for lettuce production, without toxic effects in the chemical composition of the plant.     

Heavy‐Metal Contamination of Soil and Vegetables in Wastewater‐Irrigated Agricultural Soil in a Suburban Area of Hanoi,Vietnam

The To Lich and Kim Nguu Rivers, laden with untreated waste from industrial sources, serve as sources of water for irrigating vegetable farms. The purposes of this study were to identify the impact of wastewater irrigation on the level of heavy metals in the soils and vegetables and to predict their potential mobility and bioavailability. Soil samples were collected from different distances from the canal. The average concentrations of the heavy metals in the soil were in the order zinc (Zn; 204 mg kg^?1) > copper (Cu; 196 mg kg^?1) > chromium (Cr; 175 mg kg^?1) > lead (Pb; 131 mg kg^?1) > nickel (Ni; 60 mg kg^?1) > cadmium (Cd; 4 mg kg^?1). The concentrations of all heavy metals in the study site were much greater than the background level in that area and exceeded the permissible levels of the Vietnamese standards for Cd, Cu, and Pb. The concentrations of Zn, Ni, and Pb in the surface soil decreased with distance from the canal. The results of selective sequential extraction indicated that dominant fractions were oxide, organic, and residual for Ni, Pb, and Zn; organic and oxide for Cr; oxide for Cd; and organic for Cu. Leaching tests for water and acid indicated that the ratio of leached metal concentration to total metal concentration in the soil decreased in the order of Cd > Ni > Cr > Pb > Cu > Zn and in the order of Cd > Ni > Cr > Zn > Cu > Pb for the ethylenediaminetetraaceitc acid (EDTA) treatment. The EDTA treatment gave greater leachability than other treatments for most metal types. By leaching with water and acid, all heavy metals were fully released from the exchangeable fraction, and some heavy metals were fully released from carbonate and oxide fractions. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the vegetables exceeded the Vietnamese standards. The transfer coefficients for the metals were in the order of Zn > Ni > Cu > Cd = Cr > Pb.     

Plant uptake of metals,transfer factors and prediction model for two contaminated regions of Kosovo

The bioavailability and plant uptake of heavy metals (HM), as well as finding the most reliable methods for the prediction of availability, continues to be one of the most crucial problems in agricultural and environmental studies. In agricultural soils from two regions in Kosovo, known for its metal pollution, we collected 60 soil and plant samples (wheat, corn, potatoes, and grass). Heavy metals were extracted from soil with aqua regia (pseudototal concentration), NH₄OAc‐EDTA (potential bioavailable), and NH₄NO₃ (mobile fraction), plant samples were digested with HNO₃/H₂O₂ (microwave assisted extraction). The pseudo total content of Cd, Pb, and Zn showed high value in Mitrovice (mean: Cd–2.92, Pb–570.15, and Zn–522.86 mg kg^?1), whereas in Drenas region Ni and Cr showed high value with a mean 258.54 and 203.22 mg kg^?1. Also, the potential bioavailability and mobile form of these metals were increased in Mitrovice (mean: Cd–1.59, Pb–217.05, Zn–522.86 mg kg^?1, respectively Cd–0.17, Pb–0.64, and Zn–15.45 mg kg^?1), compared to Drenas. Cd and Pb were elevated in potato tubers (mean Cd–0.48 and Pb–0.85 mg kg^?1). The TF was higher for micronutrients (Zn and Cu) than for non‐essential metals (Cd and Pb). Multiple regression analysis showed a good model for prediction of Cd, Pb and Zn content in plant with significance 99.9%, whereas this model was not significant for Cu, Cr, and Ni. Soil pH played a significant role in the content of Cd and Zn in wheat and potato plants. Clay content also showed significance in Cd concentration in wheat and potato plants, while carbon content was significant for Cd in grass plants, as well as for Zn in wheat and grass plants.     

Hg, Cu, Pb, Cd, and Zn Accumulation in Macrophytes Growing in Tropical Wetlands

The concentrations of Hg, Cu, Pb, Cd, and Zn accumulated by regional macrophytes were investigated in three tropical wetlands in Colombia. The studied wetlands presented different degrees of metal contamination. Cu and Zn presented the highest concentrations in sediment. Metal accumulation by plants differed among species, sites, and tissues. Metals accumulated in macrophytes were mostly accumulated in root tissues, suggesting an exclusion strategy for metal tolerance. An exception was Hg, which was accumulated mainly in leaves. The ranges of mean metal concentrations were 0.035?C0.953 mg g^?1 Hg, 6.5?C250.3 mg g^?1 Cu, 0.059?C0.245 mg g^?1 Pb, 0.004?C0.066 mg g^?1 Cd, and 31.8?363.1 mg g^?1 Zn in roots and 0.033?C0.888 mg g^?1 Hg, 2.2?C70.7 mg g^?1 Cu, 0.005?C0.086 mg g^?1 Pb, 0.001?C0.03 mg g^?1 Cd, and 12.6?C140.4 mg g^?1 Zn in leaves. The scarce correlations registered between metal concentration in sediment and plant tissues indicate that metal concentrations in plants depend on several factors rather than on sediment concentration only. However, when Cu and Zn sediment concentrations increased, these metal concentrations in tissues also increased in Eichhornia crassipes, Ludwigia helminthorriza, and Polygonum punctatum. These species could be proposed as Cu and Zn phytoremediators. Even though macrophytes are important metal accumulators in wetlands, sediment is the main metal compartment due to the fact that its total mass is greater than the corresponding plant biomass in a given area.     

Heavy Metal Concentration Survey in Soils and Plants of the Les Malines Mining District (Southern France): Implications for Soil Restoration

Mining activities generate spoils and effluents with extremely high metal concentrations of heavy metals that might have adverse effects on ecosystems and human health. Therefore, information on soil and plant metal concentrations is needed to assess the severity of the pollution and develop a strategy for soil reclamation such as phytoremediation. Here, we studied soils and vegetation in three heavily contaminated sites with potential toxic metals and metalloids (Zn, Pb, Cd, As, TI) in the mining district of Les Malines in the Languedoc region (southern France). Extremely high concentrations were found at different places such as the Les Aviniéres tailing basins (up to 160,000 mg kg^?C1 Zn, 90,000 mg kg^?C1 Pb, 9,700 mg kg^?C1 of As and 245 mg kg^?C1 of Tl) near a former furnace. Metal contamination extended several kilometres away from the mine sites probably because of the transport of toxic mining residues by wind and water. Spontaneous vegetation growing on the three mine sites was highly diversified and included 116 plant species. The vegetation cover consisted of species also found in non-contaminated soils, some of which have been shown to be metal-tolerant ecotypes (Festuca arvernensis, Koeleria vallesiana and Armeria arenaria) and several Zn, Cd and Tl hyperaccumulators such as Anthyllis vulneraria, Thlaspi caerulescens, Iberis intermedia and Silene latifolia. This latter species was highlighted as a new thallium hyperaccumulator, accumulating nearly 1,500 mg kg^?C1. These species represent a patrimonial interest for their potential use for the phytoremediation of toxic metal-polluted areas.     

Remediation of a Sandy Soil Contaminated with Cadmium,Nickel, and Zinc using an Insoluble Polyacrylate Polymer

Abstract

This study was carried out to investigate whether an insoluble polyacrylate polymer could be used to remediate a sandy soil contaminated with cadmium (Cd) (30 and 60 mg Cd kg^?1 of soil), nickel (Ni) (50 and 100 mg Ni kg^?1 of soil), zinc (Zn) (250 and 400 mg Zn kg^?1 of soil), or the three elements together (30 mg Cd, 50 mg Ni, and 250 mg Zn kg^?1 of soil). Growth of perennial ryegrass was stimulated in the polymer‐amended soil contaminated with the greatest amounts of Ni or Zn, and when the three metals were present, compared with the unamended soil with the same levels of contamination. Shoots of plants cultivated in the amended soil had concentrations of the metals that were 24–67% of those in plants from the unamended contaminated soil. After ryegrass had been growing for 87 days, the amounts of water‐extractable metals present in the amended soil varied from 8 to 53% of those in the unamended soil. The results are consistent with soil remediation being achieved through removal of the metals from soil solution.     

Effect of cadmium toxicity on micronutrient concentration,uptake and partitioning in seven rice cultivars

Heavy metal uptake, translocation and partitioning differ greatly among plant cultivars and plant parts. A pot experiment was conducted to determine the effect of cadmium (Cd) levels (0, 45 and 90 mg kg^?1 soil) on dry matter yield, and concentration, uptake and translocation of Cd, Fe, Zn, Mn and Cu in seven rice cultivars. Application of 45 mg Cd kg^?1 soil decreased root and shoot dry weight. On average, shoot and root Cd concentrations and uptake increased in all cultivars, but micronutrients uptake decreased following the application of 45 mg Cd kg^?1. No significant differences were observed between 45 and 90 mg kg^?1 Cd levels. On average, Cd treatments resulted in a decrease in Zn, Fe and Mn concentrations in shoots and Zn, Cu and Mn concentrations in roots. Differences were observed in Cd and micronutrient concentrations and uptake among rice cultivars. Translocation factor, defined as the shoot/root concentration ratio indicated that Cu and Fe contents in roots were higher than in shoots. The Mn concentration was much higher in shoots. Zinc concentrations were almost similar in the two organs of rice at 0 and 45 mg Cd kg^?1. A higher Cd level, however, led to a decrease in the Zn concentration in shoots.     

Influence of pH on the release and chemical fractionation of heavy metals in sediment from a suburban drainage stream in an arid mine-based oasis

Purpose

The objectives of this study were to explore the influences of pH on the release of Cu, Zn, Cd, Pb, Ni, and Cr in sediments derived from the upstream, middle, and downstream reaches of Dongdagou stream in Gansu Province, Northwest China, and to examine the fractionation changes of heavy metals in the sediments after reaching their release equilibrium under different pH conditions.

Materials and methods

Sediment samples were obtained using a stainless steel grab sampler to collect the uppermost 10 cm of sediment from the channel bed. The pH-dependent release experiment was conducted in the solid-to-liquid ratio of 1:20 at different pH values (2, 4, 6, 8, 10, and 12) at room temperature. The total Cu, Zn, Cd, Pb, Ni, and Cr concentrations in the sediments were digested using an acid digestion mixture (HNO₃ + HF + HClO₄) in an open system. Metal fractionation of selected sediments was obtained using the Tessier sequential extraction procedure. Heavy metal concentrations in the samples were determined using atomic absorption spectrophotometry.

Results and discussion

The mean concentrations of heavy metals in sediments decreased in the following order: Zn (1676.67 mg kg^?1) > Pb (528.65 mg kg^?1) > Cu (391.34 mg kg^?1) > Cr (53.48 mg kg^?1) > Ni (34.27 mg kg^?1) > Cd (11.53 mg kg^?1). Overall, the solubility of Cu, Zn, Cd, Pb, and Ni decreased with increasing pH, and they were strongly released at pH 2. Moreover, the solubility of Cr increased with increasing pH, and its release was highest at pH 12. After reaching the release equilibrium of heavy metals under different pH conditions, the percentages of organic Cu, Zn, Cd, and Fe-Mn oxyhydroxide Pb decreased, compared to their initial fractions. The residual fractions of Ni and Cr were dominant, regardless of pH.

Conclusions

The average concentrations of Cu, Zn, Cd, and Pb in sediments were highly elevated compared with the soil background values in Gansu Province, China. The results of this pH-dependent release experiment showed that the release behaviors of Cu, Zn, Pb, and Cr followed an asymmetric V-shaped pattern, whereas Cd and Ni followed an irregular L-shaped pattern. The changes in the release of heavy metals in sediments were related to their redistribution between chemical fractionations.

     

Anthropogenic Heavy Metal Pollution in the Surficial Sediments of the Keratsini Harbor, Saronikos Gulf, Greece

The contents of ten elements [Cd, Pb, W, Zn, Mn, As, Se, Cr, Cu, and organic carbon (C_org)] have been determined in the surficial sediments of Keratsini harbor, Saronikos Gulf, Greece. The contamination of the sediments was assessed on the basis of geoaccumulation index and to corresponding sediment quality guidelines (SQGs) effects range low/effects range median. The results revealed highly elevated Cd, Pb, W, Zn, As, Se, Cr, Cu, and C_org values (Cd, 190–1,763 mg kg^?1; Pb, 521–1,263 mg kg^?1; W, 38–100 mg kg^?1; Zn, 409–6,725 mg kg^?1; Mn, 95–1,101 mg kg^?1; As, not detectable–1,813 mg kg^?1; Se, not detectable–58 mg kg^?1; Cr, 264–860 mg kg^?1; Cu, 195–518 mg kg^?1; and C_org, 0.69–4.41%). The enrichment of metals in the sediments results from the contribution of the central Athens sewage outfall through which the waste of the Attica basin ends up in Keratsini harbor as well as from industrial and ship contaminants.     

Trace metals in the forest floor at saddleback mountain,maine in relation to aspect,elevation, and cover type

The objectives of this study were to obtain information about trace metal levels in a montane ecosystem in western Maine, and to compare these results to levels of trace metals reported in the literature for other areas of New England. Forest floor samples were collected at Saddleback Mountain, Maine from sites along two elevational transects on the western and eastern slopes. Five sites were located on the western slope, each in a different vegetation zone, and three sites were selected on the eastern slope, each corresponding in elevation and vegetation type as closely as possible to three of the western sites. Forest floor samples were collected as 15 x 15 cm blocks to the surface of the underlying mineral soil and sectioned into 2 cm depth increments. Zinc and Cr concentrations in the forest floor were significantly greater on the western slope (118 and 3.7 mg kg^?1, respectively), whereas Pb concentration was greater on the eastern slope (80 mg kg^?1) Cadmium, Cr, Cu, Ni, V, and Zn contents were significantly greater on the western slope (45, 83, 79, 143, and 1432 mg in ^?2, respectively). Copper, Ni, Cd, and Zn concentrations and contents in the forest floor decreased with increasing elevation, and no trends of increasing trace metal contents with increasing elevation were evident. Trace metal concentrations and contents were always lower in the deepest increment of the forest floor as compared to the surface increment (except for Cr), but concentration and content trends with depth varied. Chromium tended to increase with depth where a depth trend was evident. Overall, forest floor trace metal levels were strongly related to forest stand type and forest floor properties.     

Influences of Cadmium and Zinc Interaction and Humic Acid on Metal Accumulation in Ceratophyllum Demersum

Interactions between Zn and Cd on the accumulation of these metals in coontail, Ceratophyllum demersum were studied at different metal concentrations. Plants were grown in nutrient solution containing Cd (0.05–0.25 mg l^?1) and Zn (0.5–5 mgl^?1). High concentrations of Zn caused a significant decrease in Cd accumulation. In general, adding Cd solution decreased Zn accumulation in C. demersum except at the lowest concentration of Zn in which the Zn accumulation was similar to that without Cd. C. demersum could accumulate high concentrations of both Cd and Zn. The influence of humic acid (HA) on Cd and Zn accumulation was also studied. HA had a significant effect on Zn accumulation in plants. 2 mg l^?1 of HA reduced Zn accumulation at 1 mg l^?1 level (from 2,167 to 803 mg kg^?1). Cd uptake by plant tissue, toxicity symptoms and accumulation at 0.25 and 0.5 mg l^?1, were reduced (from 515 to 154 mg kg^?1 and from 816 to 305 mg kg^?1, respectively) by addition of 2 mg l^?1 of HA. Cd uptake reached a maximum on day 9 of treatment, while that of Zn was observed on day 15. Long-term accumulation study revealed that HA reduced toxicity and accumulation of heavy metals.     

Bioremediation of Co-contamination of Crude Oil and Heavy Metals in Soil by Phytoremediation Using Chromolaena odorata (L) King & H.E. Robinson

The capability of Chromolaena odorata (L) to grow in the presence of different concentrations of three heavy metals in crude oil-contaminated soil and its capability to remediate the contaminated soil was investigated using pot experiments. C. odorata plants were transplanted into contaminated soil containing 50,000 mg kg^?1 crude oil and between 100 and 2,000 mg kg^?1 of cadmium, nickel, and zinc and watered weekly with water containing 5% NPK fertilizer for 180 days. C. odorata did not show any growth inhibition in 50,000 mg kg^?1 crude oil. Plants in experiments containing 2,000 mg kg^?1 Cd showed little adverse effect compared to those in Zn-treated soil. Plants in 1,000 and 2,000 mg kg^?1 Ni experiments showed more adverse effects. After 180 days, reduction in heavy metals were: 100 mg kg^?1 experiments, Zn (35%), Cd (33%), and Ni (23%); 500 mg kg^?1, Zn (37%), Cd (41%), and Ni (25%); 1,000 mg kg^?1, Zn (65%), Cd (55%), and Ni (44%); and 2,000 mg kg^?1, Zn (63%), Cd (62%), and Ni (47%). The results showed that the plants accumulated more of the Zn than Cd and Ni. Accumulation of Zn and Cd was highest in the 2,000 mg kg^?1 experiments and Ni in the 500 mg kg^?1 experiments. Crude oil was reduced by 82% in the experiments that did not contain heavy metals and by up to 80% in the heavy metal-treated soil. The control experiments showed a reduction of up to 47% in crude oil concentration, which was attributed to microbial action and natural attenuation. These results show that C. odorata (L) has the capability of thriving and phytoaccumulating heavy metals in contaminated soils while facilitating the removal of the contaminant crude oil. It also shows that the plant??s capability to mediate the removal of crude oil in contaminated soil is not significantly affected by the concentrations of metals in the soil.     

Accumulation of Metals in the Sediment and Reed Biomass of a Combined Constructed Wetland Treating Domestic Wastewater

This study assessed the accumulation of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the sediment and biomass of P. australis (Cav.) Trin. ex Steud. in a combined constructed wetland (CW) designed for the treatment of domestic wastewater of 750 population equivalents. The CW consists of two vertical subsurface flow (VSSF) reed beds followed by two horizontal subsurface flow (HSSF) reed beds. The sediment in the VSSF reed bed was contaminated with Cu (201 ?±? 27 mg kg^?1 DM) and Zn (662 ?±? 94 mg kg^?1 DM) after 4 years of operation. Concentrations of Cd, Cu, Pb and Zn in the sediment generally decreased along the treatment path of the CW. On the contrary, higher Al, Cr, Fe, Mn and Ni concentrations were observed in the sediment of the inlet area of the HSSF reed bed. Redox conditions were presumably responsible for this observed trend. Metal concentrations in the reed biomass did not show excessive values. Accumulation in the aboveground reed biomass accounted for only 0.5 and 1.4% of, respectively, the Cu and Zn mass load in the influent. The sediment was the main pool for metal accumulation in the CW.     

Metal uptake in maize, willows and poplars on impoldered and freshwater tidal marshes in the Scheldt estuary

Foliar Cd and Zn concentrations in Salix, Populus and Zea mays grown on freshwater tidal marshes were assessed. Soil metal concentrations were elevated, averaging 9.7 mg Cd kg^?1 dry soil, 1100 mg Zn kg^?1 dry soil and 152 mg Cr kg^?1 dry soil. Cd (1.1–13.7 mg kg^?1) and Zn (192–1140 mg kg^?1) concentrations in willows and poplars were markedly higher than in maize on impoldered tidal marshes (0.8–4.8 mg Cd kg^?1 and 155–255 mg Zn kg^?1). Foliar samples of maize were collected on 90 plots on alluvial and sediment‐derived soils with variable degree of soil pollution. For soil Cd concentrations exceeding 7 mg Cd kg^?1 dry soil, there was a 50% probability that maize leaf concentrations exceeded public health standards for animal fodder. It was shown that analysis of foliar samples of maize taken in August can be used to predict foliar metal concentrations at harvest. These findings can therefore contribute to anticipating potential hazards arising from maize cultivation on soils with elevated metal contents.     

Trace metals in sediments and aquatic plants from the Xiangjiang River, China

Purpose

The metal concentrations and Pb isotopic composition in sediments and plants from the Xiangjiang River, China, were investigated to understand the contamination and potential toxicity of metals in sediments; to determine the accumulation and distribution of metals in plant tissues; and to trace the possible pollution source of Pb in sediments and plants.

Materials and methods

Sediments and plants were collected from 43 sampling sites in the study region. After sediments were air-dried and passed through a 63-??m sieve, they were acid-digested and DTPA-extracted for determination of total and bioavailable metals. The plants were separated into roots, leaves, and stems; dried; cut into pieces; and digested with HNO₃?CH₂O₂. Metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) and Pb isotopic composition were analyzed by inductively coupled plasma-mass spectrometry.

Results and discussion

Maximum As, Cd, Cr, Cu, Ni, Pb, and Zn concentrations in sediments were 47.18, 55.81, 129.5, 161.6, 160.4, 430.7, and 1,098.8?mg?kg^?1, respectively. The bioavailable fractions of As, Cd, Cu, Pb, and Zn had significant linear relationship with their corresponding total contents in sediments while no significant relationship was observed between bioavailable and total contents of Cr and Ni. In general, plant tissues showed higher As, Cd, Cu, Pb, and Zn concentrations and lower Cr and Ni concentrations compared with sediments. The ²⁰⁶Pb/²⁰⁷Pb ratios decreased in the order of total > bioavailable > stems ?? leaves > roots. A strong linear correlation was observed between the ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁶Pb/²⁰⁷Pb ratios of the plant tissues, sediments, and the possible pollution sources of Pb in the Xiangjiang River.

Conclusions

As, Cd, Cu, Pb, and Zn demonstrated higher contamination levels in sediments and plants compared with Cr and Ni. Cd had highest potential ecological risk. The Pb from anthropogenic sources with low ²⁰⁶Pb/²⁰⁷Pb ratios was preferentially associated with the bioavailable fractions in sediments and accumulated in roots. The Pb in plant tissues is mainly derived from the Pb in sediment and is taken up through the sediment-to-root pathway.     

Heavy Metal Pollution in Soils Around the Abandoned Mine Sites of the Iberian Pyrite Belt (Southwest Spain)

This paper investigates the pollution load of selected trace elements in 32 soil samples collected around 21 different mining areas of the Iberian Pyrite Belt (Southwest Spain), integrating chemical data with soil parameters to help understand the partitioning and mobility of pollutants. The minesoils are depleted in acid neutralising minerals and show limiting physicochemical properties, including low pH values and very high anomalies of potentially hazardous metals. The total concentrations of As (up to 1,560 mg kg^?1) and certain heavy metals (up to 2,874 mg kg^?1 Cu, 6,500 mg kg^?1 Pb, 6,890 mg kg^?1 Zn, 62 mg kg^?1 Hg and 22 mg kg^?1 Cd) are two orders of magnitude above the soil background values. The close association of Cd and Zn with the carbonate content in lime-amended minesoils suggests metal immobilisation through adsorption and/or co-precipitation mechanisms, after acid neutralisation, whereas As and Pb are similarly partitioned into the soil and mostly associated with iron oxy-hydroxides.     

Heavy metal pollution by long range atmospheric transport in natural soils of Southern Norway

Natural surface soils in Southern Norway are strongly contaminated by metals from atmospheric deposition. Except from local pollution with Cu, Ni and to a limited extent Pb around the town of Kristiansand, this large-scale contamination can be ascribed to long-range atmospheric transport from other parts of Europe. Zinc, As, Cu, and Pb are all found in excessive concentrations in the surface layer of natural soils throughout the region, and in particular within a zone of about 20 to 40 km from the coast. In this zone the elements appear at the following concentrations or higher in the A₀ layer (typical levels in other parts of Norway little affected by air pollution in parantheses): Zn, 120(30) mg kg^?1; As, 4(0.5) mg kg^?1; Cd, 2(0.2) mg kg^?1; Pb, 160(15) mg kg^?1. Possible harmful effects to soil biological processes of this contamination cannot be excluded.     

Potential of Borago officinalis, Sinapis alba L. and Phacelia boratus for Phytoextraction of Cd and Pb from Soil

Heavy metal phytoextraction is a soil remediation technique, which makes use of plants in removing contamination from soil. The plants must thus be tolerant to heavy metals, adaptable to soil and climate characteristics, and able to take up large amounts of heavy metals. Most of the high biomass productive plants such as, maize, oat and sunflower are plants, which do not grow in cold climates or need intensive care. In this study three “weed” plants, Borago officinalis; Sinapis alba L. and Phacelia boratus were investigated for their ability to tolerate and accumulate high amounts of Cd and Pb. Pot experiments were performed with soil containing Cd and Pb at concentrations of up to 180 mg kg^?1 and 2,400 mg kg^?1 respectively. All three plants showed high levels of tolerance. Borago officinalis; and Sinapis alba L. accumulated 109 mg kg^?1 and 123 mg kg^?1 Cd, respectively at the highest Cd spiked soil concentration. Phacelia boratus reached a Cd concentration of 42 mg kg^?1 at a Cd soil concentration of 100 mg kg^?1. In the case of Pb, B. officinalis and S. alba L. displayed Pb concentrations of 25 mg kg^?1 and 29 mg kg^?1, respectively at the highest Pb spiked soil concentration. Although the Pb uptake in P. boratus reached up to 57 mg kg^?1 at a Pb spiked soil concentration of 1,200 mg kg^?1, it is not suitable for phytoextraction because of its too low biomass.