Pb Concentrations In Plants Research Articles

Use of BCR sequential extraction procedures for soils and plant metal transfer predictions in contaminated mine tailings in Sardinia

PurposeThe total concentration of trace elements in soils does not always represent the fraction available for organisms and/or plants because they accumulate in several geochemical forms. The bioavailable concentration of Zn and Pb in mine tailing soils and its relation to the concentration in the leaves of plants growing there are analysed. Materials and methodsThe three-step sequential extraction BCR method was used to analyse samples from mine tailing and uncontaminated soils. The correlations of the Zn and Pb contents in the three BCR steps with the total concentrations of both trace elements in soils and plants and with the soil characteristics were determined. Three plant species were analysed: Dittrichia viscosa, Euphorbia pithyusa subsp. cupanii, Cistus salviifolius. The study area was situated in the Sulcis-Iglesiente biogeographic sector (SW Sardinia, Italy). Results and discussionThe soils with the highest total concentration of trace elements also presented the greatest metal availability. In general, the ratios of Pb and Zn concentrations in the BCR steps and the respective total concentrations in the soils were similar. The mine tailing soils registered high values for total Zn and Pb and also showed the highest percentages of these trace elements in the first two BCR fractions. However, the uncontaminated soils gave the highest percentages in the residual fraction. The total Pb concentration in the soils correlated with the concentrations found in the first two BCR steps (BCR1 and BCR2) and in the residue. For Zn, positive correlations were found with the three BCR steps. The correlations between the element extractions in the BCR steps and the soils characteristics depended on the particular soil type. Plant characteristics determined the correlations between the Pb and Zn concentration in leaves and soils. Specifically, none of the plants studied showed significant correlations between the Pb concentration and that found in the BCR steps. The opposite occurred for Zn whose concentration in plants appeared to be positively correlated with the concentrations found in the three BCR steps. ConclusionsThe Pb concentrations in plants and in the BCR steps were not indicative of the bioavailability of this element in the soil. On the contrary, the Zn concentration in the leaves showed the bioavailability of this element in the soil and the constituents to which it was related. The BCR method proved to be appropriate in case of Zn showing the existing correlations with the soil constituents and the plant contents.

Enhanced Scirpus triqueter phytoremediation of pyrene and lead co-contaminated soil with alkyl polyglucoside and nitrilotriacetic acid combined application

This study aimed to evaluate the effect of combination of alkyl polyglucoside (APG) and nitrilotriacetic acid (NTA) on improving the efficiency of phytoremediation for pyrene and lead (Pb) co-contaminated soil by Scirpus triqueter. Seedlings of S. triqueter with a similar size and biomass (3 g/pot) were grown on 2-month aged soil contaminated with 184.5 mg kg−1of pyrene and 454.3 mg kg−1 of Pb at pH = 8.3. After growth for 10 days, different doses of APG and NTA were added into the soil. After 60 days, the height of plants, Pb concentrations in plants, and pyrene amounts in soil were determined. Combined application of NTA and APG with lower dosage (1 + 1 g kg−1 soil and 1 + 2 g kg−1 soil) had no notable negative influence on the growth of S. triqueter. Moreover, significant synergy on Pb accumulation in S. triqueter was achieved with APG and NTA combined application. Besides, the dissipation of pyrene from soil after 60-day planting was increased in APG and NTA treatments when compared with the control treatments. Application of APG alone or combined with NTA had greater effect on enhancing dissipation of pyrene from soil than NTA alone. This study demonstrated that the remediation of Pb and pyrene co-contaminated soil by S. triqueter can be enhanced by combined application of APG and NTA. Long-term evaluation of this strategy is needed in co-contaminated field sites.

A three-year experiment confirms continuous immobilization of cadmium and lead in contaminated paddy field with biochar amendment

Heavy metal contamination in croplands has been a serious concern because of its high health risk through soil-food chain transfer. A field experiment was conducted in 2010–2012 in a contaminated rice paddy in southern China to determine if bioavailability of soil Cd and Pb could be reduced while grain yield was sustained over 3 years after a single soil amendment of wheat straw biochar. Contaminated biochar particles were separated from the biochar amended soil and microscopically analyzed to help determine where, and how, metals were immobilized with biochar. Biochar soil amendment (BSA) consistently and significantly increased soil pH, total organic carbon and decreased soil extractable Cd and Pb over the 3 year period. While rice plant tissues’ Cd content was significantly reduced, depending on biochar application rate, reduction in plant Pb concentration was found only in root tissue. Analysis of the fresh and contaminated biochar particles indicated that Cd and Pb had probably been bonded with the mineral phases of Al, Fe and P on and around and inside the contaminated biochar particle. Immobilization of the Pb and Cd also occurred to cation exchange on the porous carbon structure.

Effects of lead on anatomy, ultrastructure and concentration of nutrients in plants Oxycaryum cubense (Poep. & Kunth) Palla: a species with phytoremediator potential in contaminated watersheds

Lead (Pb) has been highlighted as a major pollutant of both terrestrial and aquatic ecosystems, causing negative impacts to these environments. The concentration of Pb in plants has increased in recent decades, mainly due to anthropogenic activities. This study has as a hypothesis that the species Oxycaryum cubense (Poep. & Kunth) Palla, abundant in aquatic environments, has the potential to be used a phytoremediator. The plants were grown in a hydroponic system with Pb in increasing concentrations (0, 4, 8, 16 and 32 mg l(-1)) for 15 days. Inductively coupled mass spectrometer (ICP OES) was used to determine the concentration of mineral nutrients and lead. Optical and transmission electron microscopy were used for the analysis of cellular damage induced by lead in roots and leaves. Ultrastructural alterations were observed as disorganization of thylakoids in the chloroplast and disruption of mitochondrial membranes in cells of leaf tissues of plants subjected to increasing Pb concentrations. There was accumulation of Pb, especially in the root system, affecting the absorption and translocation of some mineral nutrients analysed. In roots, there was reduction in the thickness of the epidermis in plants treated with Pb. This species was shown to be tolerant to the Pb concentrations evaluated, compartmentalizing and accumulating Pb mainly in roots. Due to these results, it may be considered a species with phytoremediation capacity for Pb, with potential rizofiltration of this metallic element in contaminated watersheds.

Lead and Arsenic Uptake by Leafy Vegetables Grown on Contaminated Soils: Effects of Mineral and Organic Amendments.

To assess strategies for mitigating Pb and As transfer into leafy vegetables from contaminated garden soils, we conducted greenhouse experiments using two field-contaminated soils amended with materials expected to reduce metal phytoavailability. Lettuce and mustard greens grown on these soils were analysed by ICP-MS, showing that some Pb and As transfer into the vegetables occurred from both soils tested, but plant Pb concentrations were highly variable among treatment replicates. Soil-to-plant transfer was more efficient for As than for Pb. Contamination of the leaves by soil particles probably accounted for most of the vegetable Pb, since plant Pb concentrations were correlated to plant tissue concentrations of the immobile soil elements Al and Fe. This correlation was not observed for vegetable As concentrations, evidence that most of the soil-to-plant transfer for this toxic metal occurred by root uptake and translocation into the above-ground tissues. A follow-up greenhouse experiment with lettuce on one of the two contaminated soils revealed a lower and less variable foliar Pb concentration than observed in the first experiment, with evidence of less soil particle contamination of the crop. This reduced transfer of Pb to the crop appeared to be a physical effect attributable to the greater biomass causing reduced overall exposure of the above-ground tissues to the soil surface. Attempts to reduce soil Pb and As solubility and plant uptake by amendment at practical rates with stabilizing materials including composts, peat, Ca phosphate, gypsum and Fe oxide, were generally unsuccessful. Only Fe oxide reduced soluble As in the soil, but this effect did not persist. Phosphate amendment rapidly increased soil As solubility but had no measurable effect on either soil Pb solubility or concentrations of Pb or As in the leafy vegetables. The ineffectiveness of these amendments in reducing Pb transfer into leafy vegetables is attributed in this study to the low initial Pb solubility of the studied soils and the fact that the primary mechanism of Pb transfer is physical contamination.

Soil–plant interactions and the uptake of Pb at abandoned mining sites in the Rookhope catchment of the N. Pennines, UK — A Pb isotope study

This paper examines Pb concentrations and sources in soil, grass and heather from the Rookhope catchment in the North Pennines, UK, an area of historical Pb and Zn mining and smelting. Currently, the area has extensive livestock and sports shooting industries. Risk assessment, using the source-pathway-receptor paradigm, requires the quantification of source terms and an understanding of the many factors determining the concentration of Pb in plants. A paired soil and vegetation (grass and heather) geochemical survey was undertaken. Results showed no direct correlation between soil (total or EDTA extractable Pb) and vegetation Pb concentration. However, regression modelling based on the Free-Ion Activity Model (FIAM) suggested that the underlying mechanism determining grass Pb concentration across the catchment was largely through root uptake. Spatial patterns of 206/207Pb isotopes suggested greater aerosol deposition of Pb on high moorland and prevailing wind facing slopes. This was evident in the isotopic ratios of the heather plants. Pb isotope analysis showed that new growth heather tips typically had 206/207Pb values of ~1.14, whilst grass shoots typically had values ~1.16 and bulk soil and peat ~1.18. However, the 206/207Pb ratio in the top few cm of peat was ~1.16 suggesting that grass was accessing Pb from a historical/recent pool of Pb in soil/peat profiles and consisting of both Pennine ore Pb and long-range Pb deposition. Isotope Dilution assays on the peat showed a lability of between 40 and 60%. A simple source apportionment model applied to samples where the isotope ratios was not within the range of the local Pennine Pb, suggested that grass samples contained up to 31% of non-Pennine Pb. This suggests that the historical/recent reservoir of non-Pennine Pb accessed by roots continues to be a persistent contaminant source despite the principal petrol Pb source being phased out over a decade ago.

Acumulação e translocação de elementos vestigiais em Cistus Ladanifer L. de áreas mineiras da FPI portuguesa

The accumulation and translocation of As, Cu, Pb and Zn in different Cistus ladanifer L. populations colonizing mine areas of Brancanes, Sao Domingos, Chanca and Caveira (Portuguese Iberian Pyrite Belt) and two control areas (Caldeirao and Pomarao) was evaluated. Soils from Sao Domingos and Caveira presented the greatest total concentrations of As, Cu and Pb. Brancanes and Chanca mine areas might be considered in natural attenuation processes relatively to the past mining activity that cessed about one century ago. Plants are, except those from Caveira mine area, Zn accumulators. The concentration of Pb in plants (aerial part) from the control and Sao Domingos areas are within the range considered phytotoxic. Trace elements concentrations in plants are below the domestic animal toxicity limits. Cistus ladanifer might be used in phytostabilization programs of other mine areas as trace elements concentrations in soils did not influence the behaviour of the different plant populations.

Delonix regia and Casuarina equisetifolia as passive biomonitors and as bioaccumulators of atmospheric trace metals

The suitability of two common and ubiquitously distributed and exotic ornamental plant species in Nigeria– Delonix regia and Casuarina equisetifolia as biomonitors and as effective bioaccumulators of atmospheric trace metals (Cd, Pb, Zn and Cu) has been evaluated. Bark and leaf samples from these plant species were collected in June and July 2006 at five locations in Benin City. Four of the sampling sites were in areas of high traffic density and commercial activities, the fifth site is a remote site, selected to act as a control and also to provide background information for the metals. The plant samples were collected and processed using standard procedures and trace metals were determined using atomic absorption spectrometer. The bark of the plants was able to bioaccumulate the trace metals, especially Pb which originates from anthropogenic contributions in the city. The Pb range of 20.00–70.00 μg/g measured for the bark samples of D. regia, exceeded the normal plant Pb concentration of 0.2–20.0 μg/g and most Pb data available in literature. The bark of the plants was observed to accumulate more metals compared to the leave, while D. regia was found to be slightly better than C. equisetifolia in trace metal uptake efficiency. Spatial variations in the distributions of Pb and Zn were significant ( p < 0.05), and the continuous use of leaded fuel in Nigeria was identified as the predominant source of Pb in the atmosphere.

Expression of the Phytochelatin Synthase TaPCS1 in Transgenic Aspen, Insight into the Problems and Qualities in Phytoremediation of Pb

The response of Populus tremula × tremuloides cv. Etrepole transgenic lines expressing the phytochelatin synthase TaPCS1 for Pb tolerance and accumulation was studied. In a hydroponic experiment, the concentrations of Pb in plants did not differ significantly between any of the transgenic lines assayed and the wild type (wt) plants, with any of the Pb solutions tested. However, total biomass and Pb accumulation were significantly higher in transgenic lines (PTa3, PTa5, PTa10) than in the control (wt) line when the plants were grown in solutions containing 0.75 and 1.5 mM Pb. The PTa3 and PTa5 lines accumulated 1.7 times more Pb than the wt plants. A concentration of 3.0 mM Pb was found to be toxic for both transgenic and wt plants. Biomass production was higher in transgenic lines PTa3 and PTa5 than in the wt plants growing in M4 mining soil, accumulating more Pb and Zn than in the wt plants. When the plant material was grown in soil M15, none of the parameters differed significantly between the transgenic and wt plants. The different response in soils M4 and M15 indicated that the physicochemical properties of the soil play a determinant role in the phytoremediation potential.

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils. Bidens maximowicziana is a new Pb hyperaccumulator, which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb. The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues. The Pb distribution order in the B. maximowicziana was: leaf > stem > root. The effect of amendments on phytoremediation was also studied. The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application. Compared with CK (control check), EDTA application promoted translocation of Pb to overground parts of the plant. The Pb concentrations in overground parts of plants was increased from 24.23–680.56 mg/kg to 29.07–1905.57 mg/kg. This research demonstrated that B. maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil, especially, combination with EDTA.

Lead toxicity in Brassica pekinensis Rupr.: Effect on nitrate assimilation and growth

Lead is a major heavy-metal contaminant in the environment that has various anthropogenic and natural sources. To study the phytotoxic effects of Pb on the popular vegetable Chinese cabbage (Brassica pekinensis Rupr.) via depression of nitrogen assimilation, pot culture experiments with three concentrations of treatment with Pb (0, 4, and 8 mmol/kg dry soil) were carried out. Our results demonstrated adverse effects of Pb on nitrogen assimilation and plant growth. The addition of Pb in the soil resulted in elevated accumulation of Pb in the shoots of the plants: Pb concentrations of 14.3, 202.3, and 418.2 mg/kg (DW) in the shoots were detected with the 0, 4, and 8 mmol/kg treatments, respectively. Compared to the control, Pb exposure (4 and 8 mmol/kg) significantly decreased shoot nitrate content (71% and 80% of the control), nitrate reductase activity (104% and 49% of the control), and free amino acid content (81% and 82% of the control), indicating decreased nitrogen assimilation in the plants. The effect of Pb also was shown by the progressive decline in shoot biomass with increasing Pb concentration in plant shoots and in the soil. However, at the treatment levels used in this study, lead did not induce visible toxic symptoms. The lowest-concentration Pb treatment (4 mmol/kg) stimulated chlorophyll b content but did not influence chlorophyll a content. The results suggested that the toxicity of Pb to the plants occurred at least partly via depression of nitrogen assimilation.

Prediction of Zinc, Cadmium, Lead, and Copper Availability to Wheat in Contaminated Soils Using Chemical Speciation, Diffusive Gradients in Thin Films, Extraction, and Isotopic Dilution Techniques

To predict the availability of metals to plants, it is important to understand both solution- and solid-phase processes in the soil, including the kinetics of metal release from its binding agent (ligand and/or particle). The present study examined the speciation and availability of Zn, Cd, Pb, and Cu in a range of well-equilibrated metal-contaminated soils from diverse sources using several techniques as a basis for predicting metal uptake by plants. Wheat (Triticum aestivum L.) was grown in 13 metal-contaminated soils and metal tissue concentrations (Zn, Cd, Pb, and Cu) in plant shoots were compared with total soil metal concentrations, total soluble metal, and free metal activities (pM2+) in soil pore waters, 0.01 M CaCl2-extractable metal concentrations, E values measured by isotope dilution, and effective metal concentrations, C(E), measured by diffusive gradients in thin films (DGT). In the DGT technique, ions are dynamically removed by their diffusion through a gel to a binding resin, while E values represent the isotopically exchangeable (labile) metal pools. Free metal activities (Zn2+, Cd2+, and Pb2+) in soil pore waters were determined using a Donnan dialysis technique. Plant Zn and Cd concentrations were highly related to C(E), while relationships for Zn and Cd with respect to the other measures of metals in the soils were generally lower, except for CaCl2-extractable Cd. These results suggest that the kinetically labile solid-phase pool of metal, which is included in the DGT measurement, played an important role in Zn and Cd uptake by wheat along with the labile metal in soil solution. Plant Pb concentrations were highly related to both soil pore water concentrations and C(E), indicating that supply from the solid phase may not be so important for Pb. Predictions of Cu uptake by wheat from these soils by the various measures of Cu were generally poor, except surprisingly for total Cu.

Assessment of Lead Exposure in Thohoyandou, South Africa

Lead levels in different environmental media (soil, grass leaves, water, ceramics, pencil, paint, crayons and cosmetics) were determined to assess the major sources of lead exposure in Thohoyandou, South Africa. Soil and plant leaves were used as indicators of Pb pollution from vehicle exhaust emissions. After digestion with concentrated acids (HNO3, HCl and HClO4) Pb concentrations were determined in triplicate using a flame atomic absorption spectrometer. The mean Pb concentrations at the kerb of selected busy roads were 205.5 ± 90, 273.0 ± 90 and 312.8 ± 81 μg g−1 and 154.7 ± 67, 182.9 ± 76 and 240.6 ± 66 μg g−1 for soil and plant leaves (dry weight) respectively. These concentrations were substantially higher than the values found on soils 50 m away from the roads (97.4 ± 11 μg g−1). Pb concentrations in plants collected further away from the road (50 m) were substantially lower (71.8 ± 9.0 μg g−1). The observed levels on soil are lower than the UK critical value of 500 μg g−1 for gardens and allotments; and 2000 μg g−1 for parks and open space as well as the Canadian values for agricultural (375 μg g−1), residential (500 μg g−1 and industrial (1000 μg g−1). From these data it was clear that Pb concentrations in soil samples were substantially higher than the levels obtained for plant leaves. The Pb levels in green crayons, blue crayons, pencils (from China & Germany), were 10650 ± 75.2, 8200 ± 52.4, 1160 ± 50.2, 79 ± 10.1 μg g−1 for the inner contents; and 4870 ± 58.1, 5650 ± 55.5, 1950 ± 46.6, 60 ± 12.9 μg g−1 for the outer surface paint respectively. The ceramics showed Pb levels of 630 ± 50.3 μg g−1 (saucer) and 560 ± 32.2 μg g−1 (cup), while the inner contents and outer surface paint showed 480 ± 32.4 and 318 ± 21.2 μg g−1 of Pb respectively. Early morning tap water flush gave a Pb level of 20.6 ± 5.6 μg Pb l−1. This value is higher than the WHO and FDA maximum permissible concentrations of 10 μg l−1 and 15 μg l−1 respectively.

In Situ Stabilization of Soil Lead Using Phosphorus and Manganese Oxide

In situ stabilization of Pb contaminated soils can be accomplished by adding P and Mn(IV) oxide. However, the long-term efficacy of in situ stabilization under continual P removal through plant growth is unknown. Moreover, the effects these treatments have on phytoavailability of other metals (Cd and Zn) commonly associated with Pb in soil are not well understood. Greenhouse experiments using sudax [Sorghum vulgare (L.) Moench] and Swiss chard [Beta vulgaris (L.) Koch] were carried out to evaluate the effects of plant growth on soil Pb bioavailability to humans after addition of P and other amendments, and the effects of these treatments on Pb, Cd, and Zn phytoavailability in three metal-contaminated soils. Eight treatments were used: zero P; 2500 mg of P as triple superphosphate (TSP); 5000 mg of P as TSP or phosphate rock (PR); 5000 mg of Mn oxide/kg; and combinations of Mn oxide and P as TSP or PR. The addition of P and/or Mn oxide significantly reduced bioavailable Pb, as measured by the physiologically based extraction test (PBET), in soils compared with the control even after extensive cropping. The PBET data also suggested that removal of P from soluble P sources by plants could negate the beneficial effects of P on bioavailable Pb, unless sufficient soluble P was added or soluble P was combined with Mn oxide. In general, Ph, Cd, and Zn concentrations in shoot tissues of sudax and Swiss chard were reduced significantly by TSP and did not change with the addition of PR. The combination of PR and Mn oxide significantly reduced Pb concentrations in plants compared with the control.

In Situ Stabilization of Soil Lead Using Phosphorus and Manganese Oxide

In situ stabilization of Pb contaminated soils can be accomplished by adding P and Mn(IV) oxide. However, the long-term efficacy of in situ stabilization under continual P removal through plant growth is unknown. Moreover, the effects these treatments have on phytoavailability of other metals (Cd and Zn) commonly associated with Pb in soil are not well understood. Greenhouse experiments using sudax [Sorghum vulgare (L.) Moench] and Swiss chard [Beta vulgaris (L.) Koch] were carried out to evaluate the effects of plant growth on soil Pb bioavailability to humans after addition of P and other amendments, and the effects of these treatments on Pb, Cd, and Zn phytoavailability in three metal-contaminated soils. Eight treatments were used: zero P; 2500 mg of P as triple superphosphate (TSP); 5000 mg of P as TSP or phosphate rock (PR); 5000 mg of Mn oxide/kg; and combinations of Mn oxide and P as TSP or PR. The addition of P and/or Mn oxide significantly reduced bioavailable Pb, as measured by the physiologically based extraction test (PBET), in soils compared with the control even after extensive cropping. The PBET data also suggested that removal of P from soluble P sources by plants could negate the beneficial effects of P on bioavailable Pb, unless sufficient soluble P was added or soluble P was combined with Mn oxide. In general, Pb, Cd, and Zn concentrations in shoot tissues of sudax and Swiss chard were reduced significantly by TSP and did not change with the addition of PR. The combination of PR and Mn oxide significantly reduced Pb concentrations in plants compared with the control.

Macrophytes as indicators of bioavailable Cd, Pb and Zn flow in the river Przemsza, Katowice Region

A 5 km stretch of the river Przemsza, in southern Poland, was investigated with the aim of finding out if a gradient of metal pollution was present along the river and to determine the bioavailable flow of Cd, Pb and Zn between water, sediment and submerged macrophytes. In situ experiments in pots as well as experiments in sealed jars were performed by using Potamogeton pectinatus and Myriophyllum verticillatum. These were planted in polluted sediment from 3 localities along the river and in unpolluted sediment in order to find out if metals were taken up by the shoots or roots. After 6 weeks exposure, plants, sediment and water were analysed for their metal contents. The unpolluted sediment accumulated heavy metals, indicating addition of metals from the water, while the polluted sediment instead released metals to the water. The plants accumulated heavy metals, but the absence of differences in metal content in plants grown in unpolluted and polluted sediment indicated that the metals were accumulated mainly by the leaves from the water. Increasing concentrations of Pb in plants indicated an increasing down-stream gradient of Pb. There were also higher concentrations of Cd and Zn in shoots of both plant species downstreams compared with upstreams.

Metal distribution in the Arctic ecosystems of the Chukotka Peninsula, Russia

The goal of this work was to determine the background levels of metals in the arctic ecosystems of Chukotka. We investigated the degree of natural variation in metals found in plants and soils, related to the underlying rock type. We determined Ca, Mg, K, Fe, Mn, Zn, Cu, Ni, Cr, Co, and Pb concentrations in plants and soils on acidic, carbonate, and ultrabasic rocks in different regions of Chukotka, and compared the main soil characteristics, total element content, and mobile forms of elements in substrates of different basicity. We also investigated correlations between the element concentrations in plants and the element content available to plants in the corresponding soils. The study of 200 plant species from 37 families revealed genotypical taxonomic differences in mineral composition at the species and family level. The taxa characterized by high metal accumulation are given.