Metal Concentrations In Plant Tissues Research Articles

Assessment of Metal Pollution in Sediments and Their Bioaccumulation in Phragmites australis from Shoor River, Iran

ABSTRACT Heavy metal contamination is a serious global issue that threatens both environmental and human health. This study investigated the levels of 12 heavy metals in sediments, roots, stems, and leaves of Phragmites australis (common reed) from a river in Iran, using an inductively coupled plasma optical emission spectrometer (ICP-OES). The sediment metal concentration order was: Aluminum (Al) > Iron (Fe) > Manganese (Mn) > Zinc (Zn) > Magnesium (Mg) > Nickel (Ni) > Chromium (Cr) > Lead (Pb) > Copper (Cu) > Arsenic (As) > Vanadium (V) with Cadmium (Cd) below detection limit. Concentrations of As, Ni, Pb, and Zn in the sediments exceeded background values. According to sediment quality guidelines (SQGs), metal concentrations were between the threshold effect level (TEL) and the probable effect level (PEL), remaining below the severe effect level (SEL), except for Ni. Average metal concentrations in plant tissues were lower than in sediment samples, with roots showing higher levels of Cd, V, Cu, Pb, Zn, As, Al, Mg, and Fe than in the shoots, while leaves had higher Ni, Cr, and Mn. The bioaccumulation factor of less than 1 (except for V) indicates limited bioavailibility of these metals.

Influence of municipal waste treated sludge on the quality attributes of African marigold (Tagetes erecta)

Using treated sludge to amend soil in agriculture presents opportunities and challenges, particularly concerning the augmentation of heavy metals in cultivated plants. This research looks into how applying treated sludge affects the buildup of heavy metals in African marigold (Tagetes erecta), a popular ornamental plant that could potentially help with phytoremediation. Several treatment combinations were imposed, out of which treated sludge at 2.5 t/ha showed promising results. The effect of incorporating treated sludge was found to be better in terms of using conventional manures like Farm Yard Manure and Vermicompost in quantitative terms. The sludge processed at the treatment plant underwent strict treatment procedures, resulting in odourless material that can be used as an organic amendment with nutrients. Heavy metal concentrations in plant tissues were analyzed using Inductively Coupled Plasma Mass Spectrometry (ICPMS) to assess the uptake and accumulation of heavy metals by African marigolds. Results indicated that treated sludge application did not significantly influence the accumulation and bioavailability of heavy metals in African marigolds. The treated sludge helped plants grow better and absorb nutrients; it did not cause higher levels of harmful heavy metals like cadmium and lead in the plants. The levels of heavy metals found were lower than what is considered unsafe for plants. In addition, treated sludge can serve as a soil conditioner to enhance the physicochemical properties of the soil.

Modified diatomite for soil remediation and its implications for heavy metal absorption in Calendula officinalis

BackgroundAmong different adsorbents, natural and inorganic compounds such as diatomite are important and advantageous in terms of high efficiency and cost-effectiveness, and function in stabilizing heavy metals in the environment. Calendula officinalis, a plant known as a high accumulator of heavy metals, was cultivated in soil treated with varying concentrations of modified diatomite to demonstrate the efficiency of modified diatomite in stabilizating of heavy metals in soils,ResultsThe modification of diatomite aimed to enhance Calendula officinalis adsorptive properties, particularly towards heavy metals such as lead (Pb), Zinc (Zn), Chromium (Cr), Nickle (Ni), and Copper (Cu), common contaminants in industrial soils. The experimental design included both control and treated soil samples, with assessments at regular intervals. Modified diatomite significantly decreased the bioaccumulation of heavy metals in contaminated soils except Zn, evidenced by decreased DTPA extractable heavy metals in soil and also heavy metal concentrations in plant tissues. Using 10% modified diatomite decreased 91% Pb and Cu, 78% Cr, and 79% Ni concentration of plants compared to the control treatment. The highest concentration of Zn in plant tissue was observed in 2.5% modified diatomite treatment. Remarkably, the application of modified diatomite also appeared to improve the nutrient profile of the soil, leading to enhanced uptake of key nutrients like phosphorus (P) 1.18%, and potassium (K) 79.6% in shoots and 82.3% in roots in Calendula officinalis. Consequently, treated plants exhibited improved growth characteristics, including shoots and roots height of 16.98% and 12.8% respectively, and shoots fresh and dry weight of 48.5% and 50.2% respectively., compared to those in untreated, contaminated soil.ConclusionThe findings suggest promising implications for using such amendments in ecological restoration and sustainable agriculture, particularly in areas impacted by industrial pollution.

A new hyperaccumulator plant (Spergularia rubra) for the decontamination of mine tailings through electrokinetic-assisted phytoextraction

The screening of new effective metal hyperaccumulators is essential for the development of profitable phytoremediation projects in highly degraded environments such as mining areas. The goal of this research was to analyze the phytoextraction potential of the native plant Spergularia rubra to decontaminate and eventually recover metals (phytomining) from the mine tailings (belonging to an abandoned Pb/Zn Spanish mine) in which it grows spontaneously. To do so, the ability of this plant species to accumulate metals was evaluated both under natural conditions and through simple and electrokinetically assisted phytoextraction tests using alternating current and different combinations of voltage gradient (1/2 V cm−1) and application time (6/12 h per day). The complete duration of the greenhouse trial was 64 days, although alternating current was applied only during the last 14 days. The results obtained demonstrated the exceptional effectiveness of S. rubra for metal hyperaccumulation and growth without affecting toxicity in highly contaminated mining waste. Zn was the metal accumulated to a higher extent in the shoots, reaching concentrations up to 17,800 mg kg−1; Pb was mainly accumulated in the roots reaching a maximum concentration of 8709 mg kg−1. Cu and Cd were accumulated to a lesser extent but the bioconcentration factors were much >1. It has been proved that S. rubra is a hyperaccumulator species for Zn and Cd both in natural and greenhouse conditions and, very probably, Pb in wild conditions. The application of AC current did not significantly increase metal concentrations in plant tissues but it was able to increase the aerial biomass of S. rubra by 49.8 %. As a result, the phytoextraction yields of all metals were significantly improved as compared to wild conditions (up to 86 % for Zn). It could open new expectations about the economic viability of recovering high-value metals from mine tailings.

Investigations Concerning Heavy Metals Dynamics in Reynoutria japonica Houtt.-Soil Interactions.

Reynoutria japonica Houtt (RJ) is an extremely invasive plant species, found nowadays in a wide range of habitats, including those polluted with heavy metals (HM). The aim of this study was to investigate HM dynamics in RJ-soil interactions in five habitats historically polluted with HM located in Baia Mare city, Romania. The concentrations of major metal elements (Cd, Cu, Pb, Zn) in plant tissues (roots, stems, leaves) and soil samples collected from the study sites were analyzed via portable ED-XRF spectroscopy (converted), and the translocation factor (TF) and bioconcentration factor (BCF) were calculated. The mean values of HM in soil samples collected from the study sites exceeded the threshold limit values established by Romanian legislation. Generally, the highest concentration of Cd was recorded in the above-ground part of the plant (stem and leaves), while for Cu, Pb and Zn, the highest values (with few exceptions) were recorded in the root. The metal transfer was highly effective from soil to RJ, such that all four of the HM studied exceeded the normal range of metals in a plant. Analysis of metal concentrations in plant tissues showed an efficient movement of Cd and Zn to the above-ground parts of the plant, a tendency particularly pronounced in the case of Cd (TF and BCF > 1), while Pb was the least bioaccumulated HM. It may be concluded that RJ is able to tolerate high concentrations of HM, being a good phytoextractor for Cd and Zn.

Physicochemical characteristics and microbial communities of rhizosphere in complex amendment-assisted soilless revegetation of gold mine tailings

Amendment-assisted soilless revegetation is a promissing ecological restoration method of mine tailings because of its eco-friendliness and low-cost. However, it is difficult to establish the plant community during ecological restoration because of its nutrient deficiency and heavy metal toxicity. In this study, the complex amendment, consisting of 1% peat, 1% sludge and 4% bentonite, was used to assist tall fescue to revegetate gold mine tailings. The variation in physicochemical characteristics and microbial community diversity and composition of rhizosphere tailings were investigated. The complex amendments significantly promoted tall fescue growth with an increase of 35.33% in shoot length and 27.19% in fresh weight. The improved plant growth was attributed to the reduction in heavy metal accumulation and the variation in the characteristics of rhizosphere tailing microecology. The heavy metal concentrations in plant tissues were decreased by 27.71–53.44% in the amended groups. Compared with the control, the available nitrogen (N), phosphorus (P) and potassium (K) levels in TA (without plant cultivation) and TPA (with plant cultivation) were also enhanced by 36.67–49.09% and 42.21–71.47%, respectively. Besides, the amendments introduced more exclusive operational taxonomic units (OTU) and increased the relative abundance of ecologically beneficial microbes in the rhizosphere. Overall, this study provides insight into amendment-assisted soilless revegetation and its effects on microecology to expand ecological restoration of gold mine tailings.

Assessment of the Streptomyces-plant system to mitigate the impact of Cr(VI) and lindane in experimental soils.

Phytoremediation techniques have been proposed as ecological methods to clean up contaminated sites. This study is aimed to evaluate the effect of the Streptomyces sp. Waksman & Henrici and Zea mays L. plant system on the dissipation of Cr(VI) and/or lindane from a co-contaminated soil, being 2mgkg-1 of lindane and 150mgkg-1 of chromium used. Lindane dissipation was improved in the presence of plant-microorganism association; however, Cr(VI) removal was higher when plants or the microorganism were separately. In co-contaminated systems, chromium content in plant tissues was lower than metal content in plants grown only with Cr(VI), suggesting that lindane could interfere with metal accumulation in the plant. The high malondialdehyde (MDA) concentration detected in non-inoculated plants grown with chromium could be consequence of high metal concentration in plant tissues. Interestingly, plants inoculated with Streptomyces sp. Z38 growing with Cr(VI) showed decrease in MDA concentration, indicating that the bacterium could activate defense mechanisms in the plant. Also, inoculated plants showed the highest value of superoxide dismutase activity. Lettuce plants used as bioindicators grew better in biologically treated soils compared with lettuce grown on non-treated soil. The results presented in this work provide the basis that will allow the optimization of future trials on a larger scale.

Heavy metals accumulation and translocation in native plants grown on tailing dumps and human health risk

The heavy metal concentration in plant tissues of Ranunculus ficaria, Plantago major, Taraxacum officinale, and Achillea millefolium, frequently consumed or used in traditional medicine, collected from one of radioactive area of Romania, not been previously reported by any research group. The content of Cr, Mn, Ni, Cu, Zn, Cd, Pb were determined by ICP-MS. To evaluate the level of pollution, the plants are examined to determine the EDI, HRI and TTHQ values, to reach a judgment about whether their consumption is risky or not in terms of human health. The high amounts of Cd, Mn and Pb, in tissues of Taraxacum officinale and Plantago major, lead to the fact that the ecosystem in which these species are growing should be evaluated by the authorities in terms of environmental pollution. DIM and HRI data showed that A. millefiori and R. ficaria can be safely used by locals, while T. officinale and P. major are thought to pose a risk in terms of heavy metals. Accumulation of metals by both roots and leaves in T. officinale and P. major was proportional to the metal concentration in the tailings dumps, while Cr, Mn, Cd, and Pb content exceeded the maximum permissible daily levels.

Influence of biochar and organic soil amendments on bioavailability and immobilization of copper and lead to common cocklebur in acidic sandy loam soil

Application of amendments may help to alter soil physicochemical properties and the bioavailability of metals. A pot experiment was carried out using a metal accumulator plant common cocklebur (Xanthium strumarium L.). The plant was grown in contaminated soil with copper (Cu) and lead (Pb) at four different concentrations of each metal (150, 250, 300, and 350 mg kg−1 soil). Soil amendments hardwood biochar (HWBC), farmyard manure (FYM), and vermicompost (VC) were applied at 2.77 g kg−1 rate. The amendments were effective in maintaining plant health under metal exposure. VC improved the chlorophyll stability index and dry biomass of plants, which was followed by FYM and HWBC. Decreased in peroxidase activity and metal concentration in plant tissues under the amendments disclosed their effectiveness to reduce metal toxicity. VC application reduced Pb concentration in plant up to 52.94%, while FYM reduced Cu uptake up to 30.03 % by the plant. The speciation study revealed the potentiality of the tested amendments to cause a reduction in bioavailable form of the metals. The order of efficiency to reduce exchangeable fraction of Cu was HWBC (29.2–69.0 %) > FYM (5.9–44.5 %) > VC (5.7–33.8 %). However, to reduce exchangeable fraction of Pb the order was VC (41.8–74.9 %) > FYM (30.2–60.0 %) > HWBC (18.5–26.9 %). Less bioavailable fractions (excluding exchangeable and carbonate bound) of Cu and Pb was found maximum at FYM and VC amendment respectively indicate higher efficacy of them to immobilize Cu and Pb in acidic sandy loam soil inducing reduce possibility of metal contamination in the food chain.

Trace element accumulation potential in lemongrass varieties (Cymbopogon species) and prediction through regression model equations followed by path analysis: a field study

A field investigation was conducted to monitor the trace element accumulation pattern and potential in lemongrass varieties when cultivated in varying concentrations of tannery sludge contaminated soils. Regression model equations were developed to predict the trace elements concentration in lemongrass plant parts. Model efficiency values ranged between 0.53 and 0.85 for roots and 0.50 to 0.77 for shoots. R2 for all the equations was high and ranged between 0.52 and 0.95 for roots and 0.50 to 0.91 for shoots. Path analysis coefficients revealed the status of interdependence between soil properties and heavy metal concentrations in plant tissues and their translocation pattern in the same. TF > 1 for Ni and Pb was recorded in all test varieties at different tannery sludge concentrations in soil and for Cd in Suwarna variety grown in sole TS. BAF>1 and BAC>1 for Ni and Pb was observed for all test varieties. BCF>1 for Cr was found in Suwarna variety at sole tannery sludge. It can be concluded that lemongrass can accumulate lead and nickel in its harvestable plant parts. Hence, it can act as a suitable phytoextractor for the same metals. Range of essential oil content (percentage) varied in all test varieties i.e. Shikhar (1.04–1.29), Krishna (0.94–1.05), Suwarna (0.82–0.95) and Chirharit (0.87–1.06) at different tannery sludge concentrations. Moreover, heavy metal content in the essential oil of all test varieties was found to be within the permissible limits, hence cultivation of lemongrass can be recommended at metal contaminated sites with minimum risk of food chain contamination.

Effects of Amendments with Different C/N/P Ratios on Plant and Soil Properties of a Pb-Zn Mine Tailings

A field trial was conducted with abandoned Pb-Zn mine tailings to evaluate the effectiveness of amendments with different C/N/P ratios on plant growth, soil nutrients and enzyme activities, and heavy metal concentrations in plant tissues and the mine tailings. The following results were noted. ①The application of amendments with different C/N/P ratios promoted plant growth and development. The vegetation cover and biomass increased from 2.0%-20.0% and 9.4-115 g·m-2 at 6 months to 62.5%-98.5% and 389-2358.3 g·m-2 at 30 months, respectively. ②When compared with the control tailings, the mean values of organic carbon, water organic carbon, nitrate nitrogen, and available phosphorus in the treatments with different C/N/P ratios increased 6.0%-93.3%, 1.3%-49.3%, 12.3%-214.7%, and 2.7%-81.3%, respectively. Similarly, the addition of amendments with different C/N/P ratios enhanced the soil enzyme activities of dehydrogenase, β-glucosidase, urease, and phosphatase 0.3-2.8, 0.1-1.4, 0.1-0.6, and 0.1-0.5 times those in the tailings. ③The addition of amendments with different C/N/P ratios decreased the concentrations of diethylenetriamine pentaacetate (DTPA)-extracted Cd, Cu, Pb, and Zn in the mine tailings and the accumulation of Cd, Cu, Pb, and Zn in plant tissues in different degrees. DTPA-Cd, DTPA-Cu, DTPA-Pb, and DTPA-Zn decreased 2.5%-40.2%, 1.4%-25.6%, 1.4%-15.2%, and 0.4%-24.9%, respectively, compared with the control tailings. ④Pearson's correlation coefficients showed that the vegetation cover and biomass were correlated positively with the soil nutrient elements and enzyme activities and negatively with DTPA-extractable metal concentrations. No correlations were observed between the plant metal concentrations and soil DTPA-extractable metal concentrations, nutrient elements, and enzyme activities. Generally, amendments with different C/N/P ratios aided phytostabilization of some types of mine tailings is the preferred option for full remediation of these mine wastelands.

Assessment of toxic impact of metals on proline, antioxidant enzymes, and biological characteristics of Pseudomonas aeruginosa inoculated Cicer arietinum grown in chromium and nickel-stressed sandy clay loam soils.

Considering the heavy metal risk to soil microbiota and agro-ecosystems, the study was designed to determine metal toxicity to bacteria and to find metal tolerant bacteria carrying multifarious plant growth promoting activities and to assess their impact on chickpea cultivated in stressed soils. Metal tolerant strain SFP1 recognized as Pseudomonas aeruginosa employing 16S rRNA gene sequence determination showed maximum tolerance to Cr (400μg/ml) and Ni (800μg/ml) and produced variable amounts of indole acetic acid, HCN, NH3, and ACC deaminase and could solubilize insoluble phosphates even under Cr (VI) and Ni stress. Metal tolerant P. aeruginosa reduced toxicity of Cr (VI) and Ni and concomitantly enhanced the performance of chickpea grown under stressed and conventional soils. At 144mgCrkg-1, the measured parameters of a bacterial strain was significantly enhanced, but it was lower compared to those recorded at 660mgNikg-1. The strain SFP1 demonstrated maximum increase in seed yield (81%) and grain protein (16%) at 660mgNikg-1 over uninoculated and untreated control. Stressed plants had more proline, antioxidant enzymes, and metal concentrations in plant tissues. P. aeruginosa, however, remarkably declined the level of stress markers (proline and APX, SOD, CAT, and GR), as well as with Cr (VI) and Ni uptake by chickpea. Conclusively, P. aeruginosa strain SFP1 due to its dual metal tolerant ability, capacity to secrete plant growth promoting regulators even under metal stress and potential to mitigate metal toxicity, could be developed as microbial inoculant for enhancing chickpea production in Cr and Ni contaminated soils.

Baseline water quality of municipal ponds and metal removal ability of Typha latifolia L. from sewage and industrial wastewaters

ABSTRACTMunicipal effluent of three rural settings of Islamabad was assessed for physicochemical and microbiological parameters by collecting wastewater from inlet and center of ponds. Results showed that water quality was comparatively better at the center as Typha latifolia plants were growing toward the center of ponds. In another study, the wastewater treatment ability of T. latifolia was investigated by growing them in industrial and municipal effluent under greenhouse conditions. Water and plant samples were collected periodically (3rd, 10th, 17th, 24th, and 31st day after transplanting) for the measurement of Pb, Cu, and Cd concentrations. A decrease in heavy metal concentration of both effluents was observed as the experiment progressed and metal removal percentages ranged between 81% and 96%. Complementary the increase in metal concentration in plant tissues was observed over experimental period. Among plant tissues, metal concentration of Pb was highest i.e. 362 mg kg−1 in roots and 313 mg kg−1 in shoots at end of experiment. Pb, Cu, and Cd concentrations were higher in roots than shoots and hence translocation factors were less than 1.0. Metal removal efficiency was better from industrial wastewater and was in order of Pb > Cu > Cd. T. latifolia can be used for remediation of heavy metal-polluted wastewater.

Accumulation and Tolerance of Mangroves to Heavy Metals: a Review

Mangroves are under increasing heavy metal (HM) pollution pressure from human activities because of the rapid industrialization and urbanization in coastal areas. Field and laboratory experiments showed that the tolerance of mangrove plants to HM stress is normally a mixture of metal avoidance and scavenging of reactive oxygen species (ROS). In this review, related studies during the past few decades on the accumulation and tolerance of mangrove to HMs have been synthesized. In mangroves, metal accumulation mainly occurred at the root level with restricted transport to the aerial portions of the plant. The common founded HMs, such as copper, zinc, cadmium, chromium, and mercury, generally showed high bioconcentration factor in roots, while the concentration factors for these metals in leaves were usually much lower than one. The limited translocation of the toxic metals to the aerial parts renders the mangrove plants a high endurance ability to high levels of HM stress. To protect the cellular components from oxidative damage by HMs, mangroves have developed both enzymatic and nonenzymatic antioxidant mechanisms to scavenge the ROS. In some circumstances, the changes of antioxidative enzyme activity were usually in accordance with the changes of toxic metal concentrations in plant tissues. However, the responses of antioxidative enzymes in mangroves to HM stress varied with plant species, metal type, and concentration, as well as the duration of the treatment time. More toxicity tests are needed with early life stages of mangroves to determine threshold effect concentrations under more realistic conditions.

Edible wild plants growing in contaminated floodplains: implications for the issuance of tribal consumption advisories within the Grand Lake watershed of northeastern Oklahoma, USA.

Metal releases from the Tri-State Mining District (TSMD) that is located in southwestern Missouri, southeastern Kansas, and northeastern Oklahoma, have contaminated floodplain soils within the Neosho and Spring river watersheds of the Grand Lake watershed. Since the Oklahoma portion of the watershed lies within ten tribal jurisdictions, the potential accumulation of metals within plant species that are gathered and consumed by tribal members, as well as the resulting metal exposure risks to tribal human health, was a warranted concern for further investigation. Within this study, a total of 36 plant species that are commonly consumed by tribes were collected from floodplain areas that were previously demonstrated to have elevated soil metal concentrations relative to reference sites. A significant, positive correlation was shown for metal concentrations in plant tissues versus soil (n=258; Cd: R=0.72, p=0.00; Pb: R=0.52, p=0.00; and Zn: R=0.70, p=0.00). Additionally, a significant difference in metal concentration distributions existed between reference and impacted plant samples (n=210, p=0.00 for all metals). These results proved that floodplain soils are a major contamination pathway for metal accumulation within plants, and the source of metal contamination is the result of mining releases from the TSMD. Metal accumulation within plants was found to vary according to specific metal and plant species. The lowest dietary exposure out of all plant organs sampled were associated with fruit, whereas the highest was associated with roots, stem/leaves, and low-lying leafy greens. Metals in plants were compared to weekly dietary intake limits established by the Joint FAO/WHO Expert Committee on Food Additives. Based on specific serving sizes established within this study for tribal children and adults, many plant species had sufficient concentrations to warrant tribal consumption restrictions within the floodplains of Elm Creek, Grand Lake, Lost Creek, Spring River, and Tar Creek. Importantly, these results highlighted the necessity for the issuance of plant consumption advisories for tribal communities in the watershed. A consumption restriction guide on the number of allowable servings of each species per week at specific streams was developed within this study for tribal children and adults. Results also demonstrated that soil metal concentrations do not need to be exceptionally elevated relative to reference sites in order for plants to accumulate sufficient metal concentrations to exceed dietary limits for one serving. Therefore, the exposure risk associated with the consumption of plants cannot be accurately predicted solely from metal concentrations within soils, but must be based on metal concentrations within specific plant tissues on a site-by-site basis. A weekly consumption scenario was created within this study in order to better understand the potential metal dietary exposures to child and adult tribal members who consume multiple servings of multiple plant species per day, as well as benthic invertebrates and fish from the watershed. These findings demonstrated that plants pose a greater consumption exposure risk for tribal members than benthic invertebrates or fish. Therefore, without the consideration of exposure risks associated with the consumption of plants within future human health risk assessments, tribal health risks will be severely underestimated.

Fraction distribution and migration of heavy metals in mangrove-sediment system under sulphur and phosphorus amendment

ABSTRACT In this study, mangrove seedlings (Kandelia obovata (S. L.)) were cultivated in rhizo-boxes, which contain sediments collected from natural mangrove forest and modified with different rates of sulphate and phosphate. The fraction distributions of Zn, Cd, Cu, Ni and Pb in rhizosphere and non-rhizosphere sediments were studied by using a sequential extraction method. Metal concentrations in plant tissues and iron plaque on root surface were also determined to reveal migration variation of heavy metals in the plant-sediment system. The results showed that the activities of K. obovata roots enhance the reducible metals while reducing acid-extractable and oxidisable metals; sulphur amendment benefits the combination of metal ions with S2– and therefore reduces the bioavailability of metal pollutants; addition of sulphur also improves the content of iron plaque on the root surface, which plays an important role in metal accumulation by K. obovata root tissue; the addition of sulphur markedly reduces the concentration of Cd in roots, but significantly enhanced the concentrations of Cu, Zn, Ni and Pb in roots. The results indicate that sulphur and phosphorus content in mangrove sediment, and the growth of mangrove plant can significantly influence the migration of heavy metals in the mangrove wetland ecosystem.

Mobility and uptake of zinc, cadmium, nickel, and lead in sludge-amended soils planted to dryland maize and irrigated maize-oat rotation.

Sludge application to agricultural lands is often limited mainly because of concerns about metal accumulation in soils and uptake by crops. The objective of the study was to test the following hypotheses: (i) in the short to medium term (5-10 yr), the application of good-quality sludge according to crop N requirements will not lead to significant accumulation of water-soluble metal fractions in soil, (ii) mobility and uptake of metals is higher under irrigated than dryland systems, and (iii) metal concentrations in plant tissue could reach phytotoxic levels before the soil reaches environmental threshold levels. Field plots were arranged in a randomized complete block design comprising four replications of three treatments (0, 8, and 16 Mg ha yr anaerobically digested municipal sludge) planted to dryland maize and irrigated maize-oat rotation. Soil and plant samples were collected after 7 yr of treatment application for selected metal analyses. A large fraction of the Zn, Ni, and Pb in the soil profile was ethylenediaminetetraacetic acid extractable (46-79%). Saturated paste-extractable fractions of Cd and Pb were <1 mg kg. Plant uptake of Cd, Pb, and Ni under irrigation was double that for dryland systems. Concentrations of the metals considered in plant tissue of both cropping systems remained well below phytotoxic levels, except for Zn under dryland maize, which received 16 Mg sludge ha yr. Metal concentrations in the soil remained far below total maximum threshold levels. Therefore, hypotheses 1 and 3 were accepted for the metals considered, and hypothesis 2 was rejected for Zn.

Application of 65Zn and 54Mn isotopic dilution for evaluation of available soil manganese and zinc fractions in Western Slovak region

This paper mapped the accumulation and availability of zinc and manganese in young wheatgrass plants (Triticum aestivum L.) grown in typical agricultural soil (Calcic Phaenozem) of Western Slovakia. For estimation of zinc and manganese availability the biological, chemical and radiochemical methods with application of 65Zn and 54Mn isotopic dilution and gamma spectrometry were used. Radiochemical and statistical analyses of obtained metal concentrations in plant tissues, soil samples, soil extracts and isotopically exchangeable fractions (E-values) confirmed the significant correlations mainly between wheatgrass concentrations and E-values. Results showed the important role of isotopic dilution methods for quantification of available metal fractions.

Metal Uptake in Plants and Health Risk Assessments in Metal‐Contaminated Smelter Soils

AbstractMetal pollution is an important concern because of its potential to affect human health. Metals such as lead and cadmium can enter soil via the food chain and exceed normal limits, producing harmful effects. In this study, six common garden and residential plant species were grown in soils from Spelter, WV, USA, contaminated with a variety of metals including lead (Pb), zinc (Zn), cadmium (Cd), and copper (Cu). Plant species included radish, carrot, chicory, spinach, lettuce, and clover. Metal concentrations in plant tissues were compared with metal concentration in soil by a multi‐step chemical extraction. The largest accumulation of Pb (126 mg kg−1) and Zn (1493 mg kg−1) was seen in radish roots, with Cd (40 mg kg−1) having the largest accumulation in carrot roots. Comparisons of plant availability with soil chemical extractions indicated that the combined soluble and exchangeable fractions could estimate available Zn and Cd for all six plant species. For Pb and Cu, however, the comparisons indicate that these two elements were not readily available in Spelter soils. A health risk assessment was carried out for residents at Spelter on the basis of edible tissue concentrations and publicly available consumption data. Uptake of Cd by carrot roots was about five times more than the regulatory limits for men, eight times more for women, and 12 times more for children. On the basis of the results, carrot and lettuce grown in these soils have the potential to cause toxicological problems in men, women, and young children resulting from Cd and Zn accumulation. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Retention and distribution of Cu, Pb, Cr, and Zn in a full-scale hybrid constructed wetland receiving municipal sewage

This study was conducted to investigate the retention and distribution of Cu, Pb, Cr, and Zn in a hybrid constructed wetland (CW) that consists of both vertical baffled flow wetlands (VBFWs) and horizontal subsurface flow wetlands (HSSFs) with unique flow regimes and oxygen distribution. The heavy metal concentrations in water, sediments, and plant tissues in the hybrid CW were analysed. The removal of heavy metals from the water stream in the monitoring period was not statistically significant. Metal concentrations in the sediments generally decreased along the wastewater treatment process. The reductive anaerobic condition in the VBFW may promote the sulphate reduction and form highly insoluble Cu, Pb, and Zn sulphides, resulting in the higher concentration of the bivalent cations in the VBFW sediments than the corresponding values in the HSSF; however, the aerobic and anoxic environments in the HSSF enhanced the removal of Cr with the co-precipitation of iron and manganese oxides, and their hydroxides. Metal concentrations in plant tissues were not significantly influenced by the concentrations in sediments, while roots contained statistically higher metal concentrations than stems and leaves. The sediments stored 94.01, 86.31, 95.85, and 89.51% of the total Cu, Pb, Cr, and Zn retained in the hybrid CW system, respectively, while only small fractions (<10%) were accumulated in the harvestable macrophyte tissues. It is important to clean not only the accessible sediments in free water surface tank and ponds but also the embedded sediments in vegetated beds for the sustainable removal of heavy metals.