Interactions of metals affect their distribution in tissues of Phragmites australis

Culms of Phragmites australis were grown in vermiculite in a greenhouse. Some plants were exposed to 1000 microg/g Cu or Pb or Zn, or combinations of two or three of those metals. When plants reached senescence, they were harvested and analyzed for metal concentrations in upper leaves, lower leaves, stems and roots. While all metals accumulated in highest concentrations in the roots, Zn accumulated in aboveground tissues far more than the other metals. Furthermore, the concentration of any one metal in the different tissues was affected by the presence of other metals. The amount of copper in upper leaves increased when Zn was also present with the Cu. The amount of Cu in roots was increased in the presence of Pb and/or Zn. The amount of Zn in lower leaves was reduced when Cu was also present along with Zn. Thus, when combinations of metals were present, the distribution of metals was altered. The most important interactions appeared to be of Cu and Zn, which may reflect competition for binding sites on metal-binding proteins.     

EDDS and EDTA-enhanced zinc accumulation by Solanum nigrum inoculated with arbuscular mycorrhizal fungi grown in contaminated soil

The effect of two different chelating agents [EDTA and EDDS (S,S-ethylenediaminedissucinic acid)] on Zn tissue accumulation in Solanum nigrum L. grown in a naturally contaminated soil was assessed. Under those conditions, the response of the plant to the inoculation with two different isolates of arbuscular mycorrhizal fungi (AMF)--Glomus claroideum and Glomus intraradices--was also studied. Plants grown in the local contaminated soil (Zn levels of 433mg kg(-1)) accumulated up to 1191mg kg(-1) of Zn in the roots, 3747mg kg(-1) in the stems and 3409mg kg(-1) in the leaves. S. nigrum plants grown in the same soil spiked with extra Zn (Zn levels of 964mg kg(-1)) accumulated up to 4735, 8267 and 7948mg Zn kg(-1) in the leaves, stems and roots, respectively. The addition of EDTA promoted an increase in the concentration of Zn accumulated by S. nigrum of up to 231% in the leaves, 93% in the stems and 81% in the roots, while EDDS application enhanced the accumulation in leaves, stems and roots up to 140, 124 and 104%, respectively. In the stems, the presence of Zn was predominantly detected in the cortex collenchyma cells, the starch sheath and the internal phloem and xylem parenchyma, and the addition of chelating agents did not seem to have an effect on the localisation of accumulation sites. The devise of a chelate-enhanced phytoextraction strategy, using chelating agents and AMF, is discussed.     

The use of a sequential leaching procedure for heavy metal fractionation in green liquor dregs from a causticizing process at a pulp mill

A five-stage sequential leaching procedure was used to fractionate heavy metals (Cd, Cu, Pb, Cr, Zn, Fe, Mn, Ni, Co, As, V, Ba and Ti) in green liquor dregs into the following fractions: (1) water-soluble fraction (H2O), (2) exchangeable fraction (CH3COOH), (3) easily reduced fraction (HONH3Cl), (4) oxidizable fraction (H2O2 + CH3COONH4), and (5) residual fraction (HF + HNO3 + HCl). The green liquor dregs were derived from a causticizing process at a pulp mill at Kemi, Northern Finland. According to the leaching studies, the leachability of heavy metals in the water-soluble fraction varied between 0.5 and 2 mg kg(-1) expressed on a dry weight (d.w.) basis, indicating relatively low bioavailability of the metals. However, the concentration of Mn (2065 mg kg(-1); d.w.) showed a strong and of Zn (17.6 mg kg(-1); d.w.), Ni (39.7 mg kg(-1); d.w.) and Ba (32.0 mg kg(-1); d.w.) slightly tendency to be extracted in the exchangeable fraction. In addition, Zn, Mn, Ni, Co, V and Ba showed clear leachability in the easily reduced fraction, as well as Cd, Cu, Cr, Zn, Mn, As and Ba in the oxidizable fraction. For Cd, Cu, Cr, Zn, Mn, Ni, Co, Ba and Ti, the sum of leachable heavy metal concentrations in fractions 1-5 agreed relatively well with the "total" heavy metal concentrations. Recoveries of the sum of fractions 1-5 were 84-56% of those obtained by the US EPA method 3052 (i.e. concentrations obtained after microwave oven digestion with a mixture of HF and HNO3).     

Efficacy of various amendments for amelioration of fly-ash toxicity: growth performance and metal composition of Cassia siamea Lamk

Plants of Cassia siamea Lamk were grown in garden soil (control), fly-ash (100%) and fly-ash amended by various ameliorants (cowdung manure, press-mud, garden soil; 1:1, w/w). The plants survived in fly-ash (100%) though their growth was less in comparison to the treatments. Fly-ash+press-mud (1:1, w/w) proved to be the best combination as growth (total biomass, leaf number, photosynthetic area, total chlorophyll and protein) was significantly high in this treatment followed by cowdung manure and garden soil. Leaves and roots accumulated significant amount of Cu, Zn, Ni and and Fe. However, the concentration of all the metals was more in roots than leaves except Ni. Although, fly-ash contains high amount of metals but the metal uptake was more in the plants grown in fly-ash+press-mud mixture. Inspite of high metal availability in fly-ash and press-mud mixture, plant growth was good. This might be attributed to the some metal detoxification mechanism active in this treatment. The present study concluded that C. siamea seems to be a suitable plant for developing a vegetation cover on fly-ash dumps.     

Heavy metal accumulation in Halimione portulacoides: intra- and extra-cellular metal binding sites

Salt marsh plants can sequestrate and inherently tolerate high metal concentrations found in salt marsh sediments. This work intended to understand the Halimione portulacoides (L.) Aellen strategies to prevent metal toxicity, by investigating the metal location in different plant organs and in the cell. A sequential extraction was performed on leaves, stems and roots of H. portulacoides in order to determine and compare the metal (Zn, Pb, Co, Cd, Ni and Cu) concentration in several fractions of the plant material (ethanolic, aqueous, proteic, pectic, polissacaridic, lenhinic and cellulosic). This study shows that all plant organs of H. portulacoides mostly retain metals in the cell wall (65% is the average for all studied metals stored in the root cell wall, 55% in the stems and 53% in the leaves), and the metal content in the intracellular compartment is much lower (21% in roots, 25% in stems and 32% in leaves). High levels of heavy metal in the sedimentary environment do not cause toxicity to H. portulacoides, because H. portulacoides immobilizes them in different cell compartments (cell wall+proteic fraction+intracellular) outside key metabolic sites.     

Evaluation of heavy metal contents in co-composts of poultry manure with barley wastes or chestnut burr/leaf litter

The presence of heavy metals in composts is a main cause of adverse effects on animal and human health, transmitted through the food chain from the soil, groundwater and plants. In this study, the contents of Zn, Cd, Pb and Cu present in co-composts of poultry manure (liquid or solid) with a co-composting material (barley wastes or chestnut burr/leaf litter) were assessed. A compost of solid manure was used as control because a compost cannot be obtained from the liquid manure. The original solid poultry manure showed a Zn content of 2134+/-75 mg/kg, exceeding the current legal limit in Spain of 1100 mg/kg. In the solid poultry manure co-compost with chestnut burr/leaf litter and barley wastes, Zn content decreased to 813+/-25 mg/kg and 883+/-37 mg/kg, respectively. The contents in heavy metals (Zn, Cd, Pb and Cu) of the co-composts were under the maximum limit permitted under the Spanish legislation, excepting for the Zn level in liquid poultry manure co-composted with chestnut burr/leaf litter.     

Accumulation of heavy metals in native Andean plants: potential tools for soil phytoremediation in Ancash (Peru)

Metal contamination is a recurring problem in Peru, caused mainly by mine tailings from a past active mining activity. The Ancash region has the largest number of environmental liabilities, which mobilizes high levels of metals and acid drainages into soils and freshwater sources, posing a standing risk on human and environmental health. Native plant species spontaneously growing on naturally acidified soils and acid mine tailings show a unique tolerance to high metal concentrations and are thus potential candidates for soil phytoremediation. However, little is known about their propagation capacity and metal accumulation under controlled conditions. In this study, we aimed at characterizing nine native plant species, previously identified as potential hyperaccumulators, from areas impacted by mine tailings in the Ancash region. Plants were grown on mine soils under greenhouse conditions during 5 months, after which the concentration of Cd, Cu, Ni, Pb, and Zn was analyzed in roots, shoots, and soils. The bioaccumulation (BAF) and translocation factor (TF) were calculated to determine the amount of each metal accumulated in the roots and shoots and to identify which species could be better suited for phytoremediation purposes. Soil samples contained high Cd (6.50–49.80 mg/kg), Cu (159.50–1187.00 mg/kg), Ni (3.50–8.70 mg/kg), Pb (1707.00–4243.00 mg/kg), and Zn (909.00–7100.00 mg/kg) concentrations exceeding national environmental quality standards. After exposure to mine tailings, concentrations of metals in shoots were highest in Werneria nubigena (Cd, 16.68 mg/kg; Cu, 41.36 mg/kg; Ni, 26.85 mg/kg; Zn, 1691.03 mg/kg), Pennisetum clandestinum (Pb, 236.86 mg/kg), and Medicago lupulina (Zn, 1078.10 mg/kg). Metal concentrations in the roots were highest in Juncus bufonius (Cd, 34.34 mg/kg; Cu, 251.07 mg/kg; Ni, 6.60 mg/kg; Pb, 718.44 mg/kg) and M. lupulina (Zn, 2415.73 mg/kg). The greatest BAF was calculated for W. nubigena (Cd, 1.92; Cu, 1.20; Ni, 6.50; Zn, 3.50) and J. bufonius (Ni, 3.02; Zn, 1.30); BCF for Calamagrostis recta (Cd, 1.09; Cu, 1.80; Ni, 1.09), J. bufonius (Cd, 3.91; Cu, 1.79; Ni, 18.36), and Achyrocline alata (Ni, 137; Zn, 1.85); and TF for W. nubigena (Cd, 2.36; Cu, 1.70; Ni, 2.42; Pb, 1.17; Zn, 1.43), A. alata (Cd, 1.14; Pb, 1.94), J. bufonius (Ni, 2.72; Zn, 1.63), and P. clandestinum (Zn, 1.14). Our results suggest that these plant species have a great potential for soil phytoremediation, given their capability to accumulate and transfer metals and their tolerance to highly metal-polluted environments in the Andean region.     

Uptake and distribution of Zn, Cu, Cd, and Pb in an aquatic plant Potamogeton natans

A better understanding of metal uptake and translocation by aquatic plants can be used to enhance the performance of constructed wetland systems for stormwater treatment. Specifically, this study examines whether the uptake of Zn, Cu, Cd, and Pb by Potamogeton natans is via the leaves, stems, or roots, and whether there is translocation from organs of uptake to other plant parts. Competition between the metals at uptake and at the level of the cell wall-bound part of the metals accumulated in stem and leaf tissue was also examined. The results show that Zn, Cu, Cd, and Pb were taken up by the leaves, stems, and roots, with the highest accumulation found in the roots. At the elevated metal concentrations common in stormwater the uptake of Cu, but not of Zn, Cd, or Pb, by the roots was somewhat limited at uptake due to competition with other metals. Between 24% and 59% of the metal content was bound to the cell walls of the plant. Except in the case of Pb, the cell wall-bound fraction was generally smaller in stems than in leaves. No translocation of the metals to other parts of the plant was found, except for Cd which was translocated from leaf to stem and vice versa. Dispersion of metals from sediment to water through P. natans is therefore unlikely.     

Biological and ecophysiological reactions of white wall rocket (Diplotaxis erucoides L.) grown on sewage sludge compost

We studied the effects of sewage sludge compost on white wall rocket (Diplotaxis erucoides L.) compared with mineral fertilization and control (without any fertilizer) in a greenhouse experiment. The plants grown on the compost-amended soil showed a different growth dynamic: a significant delay in flowering and a bigger root system. Both the compost and the fertilization treatments increased biomass and seed yield. Heavy metal (Cu, Cd, Zn, Ni) distribution within the plant was in the following order: roots > leaves > stems, except for zinc which was homogeneously distributed. The balance of mineral nutrition was not affected by treatments. Zinc was the trace element which was most taken up. Unlike many species of Brassicaceae, white wall rocket is not a hyperaccumulator. Although sewage sludge compost improved plant growth, delay in flowering shows that it is necessary to take precautions when spreading sewage sludge in natural areas.     

Copper resistance of Calluna vulgaris originating from the pollution gradient of a Cu-Ni smelter, in southwest Finland

The copper (Cu) resistance of 1-year-old seedlings of heather (Calluna vulgaris) was tested in a greenhouse experiment. The plant material originated from seeds collected from three peatland sites located 1.2 km to the NW, and 2.5 and 5.5 km to the NE of the Harjavalta Cu-nickel (Ni) smelter, SW Finland. The plants were watered with a nutrient solution containing five different levels of Cu (1, 10, 22, 46 and 100 mg l(-1)). Cu clearly decreased the length growth of shoots, shoot and root biomass of C. vulgaris. More than 50% of the seedlings exposed to the highest Cu treatment died. C. vulgaris accumulated high amounts of Cu, the living old roots containing a maximum of 2200 mg kg(-1) Cu and the living stems 1300 mg kg(-1) Cu. Discolouring leaves contained higher Cu concentrations than green leaves. The results indicate Cu accumulation in roots and root-to-shoot transport. Some differences were found between the responses of the three seed provenances, but none of the populations proved to be more resistant to Cu than the others in all the measured responses.     

中国商品有机肥重金属分析

测定了来自10个地区不同生产原料的118个商品有机肥样品的重金属含量.结果表明:(1)商品有机肥样品中的Cd、Hg、Pb、Cr、As、Zn、Cu、Ni的平均值分别为0.600、0.120、7.34、84.30、9.45、202.91、91.06、11.01 mg/kg.(2)河南、湖北、上海的商品有机肥中8种重金属平均值均较高;内蒙古的商品有机肥中Cr平均值为20.32 mg/kg,广西的商品有机肥中Zn平均值为51.36mg/kg,远低于所有样品中Cr和Zn平均值.(3)以猪粪为主要生产原料的商品有机肥中重金属平均值最高.(4)Cr超过中国商品有机肥重金属限量标准、欧盟生态标志法的重金属限量标准、加拿大堆肥重金属限量标准(A级)和加拿大堆肥重金属限量标准(B级);As、Cd超过中国商品有机肥重金属限量标准、欧盟生态标志法的重金属限量标准和加拿大堆肥重金属限量标准(A级);Cu、Zn超过欧盟生态标志法的重金属限量标准和加拿大堆肥重金属限量标准(A级);Hg超过加拿大堆肥重金属限量标准(A级);Pb超过中国商品有机肥重金属限量标准;Ni均未超标.     

Assessment of macro and microelement accumulation capability of two aquatic plants

The concentrations of four macroelements (C, N, P, S) and eight trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) were measured in the leaves and roots of the emergent plant, Phragmites communis Trin., and in the shoots and roots of the submersed Najas marina L., taken from Lake Averno (Naples, Italy). Phragmites communis leaves showed higher concentrations of carbon, nitrogen and phosphorus than roots, while the roots exhibited significantly higher concentrations of sulphur and trace metals. Najas marina roots also showed higher concentrations of sulphur and trace metals than shoots, but these differences were less marked than in Phragmites communis except for sulphur. Sulphur was the only macronutrient to show the highest concentrations in the roots. Phragmites communis roots had higher values of Cr, Cu, Fe, Mn and Ni than Najas marina roots. By contrast, Cd, Cr, Fe, Ni, Pb and Zn concentrations were higher in Najas marina shoots than in Phragmites communis leaves. Phragmites communis, available through the year, showing high capability to accumulate trace metals in the roots, appears a good monitor of lake contamination, better than Najas marina.     

Influence of cadmium on antioxidant capacity and four microelement concentrations in tomato seedlings (Lycopersicon esculentum)

Tomato (Lycopersicon esculentum) seedlings were grown in four cadmium (Cd) levels of 0-10 microM in a hydroponic system to analyze the antioxidative enzymes, Cd concentration in the plants, and the interaction between Cd and four microelements. The results showed that there was a significant increase in malondialdehyde (MDA) concentration, and superoxide dismutase (SOD) and peroxidase (POD) activities in the plants subjected to 1-10 microM Cd. This indicates that Cd stress induces an oxidative stress response in tomato plants, characterized by an accumulation of MDA and increase in activities of SOD and POD. Root, stem and leaf Cd concentrations increased with its exposure Cd level, and the highest Cd concentration occurred in roots, followed by leaves and stems. A concentration- and tissue-dependent response was found in the four microelement concentrations to Cd stress in the tomato leaves, stems and roots. Regression analysis showed that there was a significantly negative correlation between Cd and Mn, implying the antagonistic effect of Cd on Mn absorption and translocation. The correlation between Cd and Zn, Cu and Fe were inconsistent among leaves, stems and roots.     

The effects of soil amendments on heavy metal bioavailability in two contaminated Mediterranean soils

Two heavy metal contaminated calcareous soils from the Mediterranean region of Spain were studied. One soil, from the province of Murcia, was characterised by very high total levels of Pb (1572 mg kg(-1)) and Zn (2602 mg kg(-1)), whilst the second, from Valencia, had elevated concentrations of Cu (72 mg kg(-1)) and Pb (190 mg kg(-1)). The effects of two contrasting organic amendments (fresh manure and mature compost) and the chelate ethylenediaminetetraacetic acid (EDTA) on soil fractionation of Cu, Fe, Mn, Pb and Zn, their uptake by plants and plant growth were determined. For Murcia soil, Brassica juncea (L.) Czern. was grown first, followed by radish (Raphanus sativus L.). For Valencia soil, Beta maritima L. was followed by radish. Bioavailability of metals was expressed in terms of concentrations extractable with 0.1 M CaCl2 or diethylenetriaminepentaacetic acid (DTPA). In the Murcia soil, heavy metal bioavailability was decreased more greatly by manure than by the highly-humified compost. EDTA (2 mmol kg(-1) soil) had only a limited effect on metal uptake by plants. The metal-solubilising effect of EDTA was shorter-lived in the less contaminated, more highly calcareous Valencia soil. When correlation coefficients were calculated for plant tissue and bioavailable metals, the clearest relationships were for Beta maritima and radish.     

Translocation of metals from fly ash amended soil in the plant of Sesbania cannabina L. Ritz: effect on antioxidants

The plants of Sesbania cannabina Ritz grown on different amendments of fly ash (FA), have shown a high accumulation of metals (Fe, Mn, Zn, Cu, Pb and Ni). The highest accumulation of Fe the and lowest level of Ni were recorded in these plants. The different amendments of fly ash with garden soil (GS) were extracted with DTPA and the levels of metals were found to be decreased with an increase in fly ash application ratio from 10% to 50% FA. The analysis of the results showed an increase in the level of malondialdehyde (MDA) content of the roots for all the exposure periods. The maximum increases of 136% (roots) and 120% (leaves) were observed in MDA content at 100% FA after 30 d of growth of the plant, compared to GS. The level of antioxidants was found to increase for all the exposure periods in the roots of the plants to combat metal stress. At 30 d, the maximum increase of 57% (ascorbic acid) and 78% (free proline) was observed in the roots of the plants grown on 100% and 10% FA, respectively, as compared to their respective GS. At 90 d, a maximum increase of 42% (cysteine) and 117% (NPSH) was recorded in the roots of the plants grown on 25% and 100% FA, respectively, as compared to their respective GS. In leaves, a significant increase in antioxidants i.e. cysteine, NPSH and free proline content was recorded after 30 d, whereas no such trend was observed for the rest of the exposure periods. The chlorophyll and carotenoid contents increased with an increase in the FA amendment ratio from 10% to 50% FA for all the exposure periods as compared to GS. In both roots and leaves, the level of protein content increased in all the amendments and 100% FA at 30 d as compared to GS. Thus, there is a balance in the level of MDA content and level of antioxidants in the plants at 90 d. In view of its tolerance, the plants may be used for phytoremediation of metals from fly ash contaminated sites and suitable species for plantation on fly ash land fills.     

Growth performance and biochemical responses of three rice (Oryza sativa L.) cultivars grown in fly-ash amended soil

The disposal of fly-ash (FA) from coal-fired power stations causes significant economic and environmental problems. Use of such contaminated sites for crop production and use of contaminated water for irrigation not only decreases crop productivity but also poses health hazards to humans due to accumulation of toxic metals in edible grains. In the present investigation, three rice cultivars viz., Saryu-52, Sabha-5204, and Pant-4 were grown in garden soil (GS, control) and various amendments (10%, 25%, 50%, 75% and 100%) of FA for a period of 90 days and effect on growth and productivity of plant was evaluated vis-a-vis metal accumulation in the plants. The toxicity of FA at higher concentration (50%) was reflected by the reduction in photosynthetic pigments, protein and growth parameters viz., plant height, root biomass, number of tillers, grain and straw weight. However, at lower concentrations (10-25%), FA enhanced growth of the plants as evident by the increase of studied growth parameters. The cysteine and non-protein thiol (NP-SH) content showed increase in their levels up to 100% FA as compared to control, however, maximum content was found at 25% FA in Saryu-52 and Pant-4 and at 50% FA in Sabha-5204. Accumulation of Fe, Si, Cu, Zn, Mn, Ni, Cd and As was investigated in roots, leaves and seeds of the plants. Fe accumulation was maximum in all the parts of plant followed by Si and both showed more translocation to leaves while Mn, Zn, Cu, Ni and Cd showed lower accumulation and most of the metal was confined to roots in all the three cultivars. As was accumulated only in leaves and was not found to be in detectable levels in roots and seeds. The metal accumulation order in three rice cultivars was Fe > Si > Mn > Zn > Ni > Cu > Cd > As in all the plant parts. The results showed that rice varieties Saryu-52 and Sabha-5204 were more tolerant and could show improved growth and yield in lower FA application doses as compared to Pant-4. Thus, Sabha-5204 and Saryu-52 are found suitable for cultivation in FA amended agricultural soils for better crop yields.     

Ascorbic acid, β-carotene,sugars, phenols,and heavy metals in sweet potatoes grown in soil fertilized with municipal sewage sludge

Municipal sewage sludge (MSS) used for land farming typically contains heavy metals that might impact crop quality and human health. A completely randomized experimental design with three treatments (six replicates each) was used to monitor the impact of mixing native soil with MSS or yard waste (YW) mixed with MSS (YW +MSS) on: i) sweet potato yield and quality; ii) concentration of seven heavy metals (Cd, Cr, Mo, Cu, Zn, Pb, and Ni) in sweet potato plant parts (edible roots, leaves, stem, and feeder roots); and iii) concentrations of ascorbic acid, total phenols, free sugars, and β-carotene in sweet potato edible roots at harvest. Soil samples were collected and analyzed for total and extractable metals using two extraction procedures, concentrated nitric acid (to extract total metals from soil) as well as CaCl₂ solution (to extract soluble metals in soil that are available to plants), respectively. Elemental analyses were performed using inductively coupled plasma mass spectrometry (ICP-MS). Overall, plant available metals were greater in soils amended with MSS compared to control plots. Concentration of Pb was greater in YW than MSS amendments. Total concentrations of Pb, Ni, and Cr were greater in plants grown in MSS+YW treatments compared to control plants. MSS+YW treatments increased sweet potato yield, ascorbic acid, soluble sugars, and phenols in edible roots by 53, 28, 27, and 48%, respectively compared to plants grown in native soil. B-carotene concentration (157.5 μg g^?1 fresh weight) was greater in the roots of plants grown in MSS compared to roots of plants grown in MSS+YW treatments (99.9 μg g^?1 fresh weight). Concentration of heavy metals in MSS-amended soil and in sweet potato roots were below their respective permissible limits.     

Heavy metals contents in agricultural topsoils in the Ebro basin (Spain). Application of the multivariate geoestatistical methods to study spatial variations

In this work the content of seven heavy metals (Cd, Cr, Cu, Hg, Ni, Pb and Zn) and other parameters (the pH, organic matter, carbonates and granulometric fraction) in agricultural topsoil in the Ebro basin are quantified, based on 624 samples collected according to an 8 by 8 km square mesh. The average concentrations (mg/kg) obtained were: Cd 0.415+/-0.163, Cr 20.27+/-13.21, Cu 17.33+/-14.97, Ni 20.50+/-22.71, Pb 17.54+/-10.41, Zn 17.53+/-24.19 and Hg 35.6+/-42.05 microg/kg. The concentration levels are relatively low in areas of high pH and low organic matter content concentration. The results of factor analysis group Cd, Cu, Hg, Pb and Zn in F1 and Cr y Ni in F2. The spatial heavy metals component maps based on geostatistical analysis, show definite association of these factors with the soil parent material. The local anomalies (found in Cu, Zn and Pb) are attributed to anthropogenic influence.     

Ascorbic acid, β-carotene, sugars, phenols, and heavy metals in sweet potatoes grown in soil fertilized with municipal sewage sludge

Municipal sewage sludge (MSS) used for land farming typically contains heavy metals that might impact crop quality and human health. A completely randomized experimental design with three treatments (six replicates each) was used to monitor the impact of mixing native soil with MSS or yard waste (YW) mixed with MSS (YW +MSS) on: i) sweet potato yield and quality; ii) concentration of seven heavy metals (Cd, Cr, Mo, Cu, Zn, Pb, and Ni) in sweet potato plant parts (edible roots, leaves, stem, and feeder roots); and iii) concentrations of ascorbic acid, total phenols, free sugars, and β-carotene in sweet potato edible roots at harvest. Soil samples were collected and analyzed for total and extractable metals using two extraction procedures, concentrated nitric acid (to extract total metals from soil) as well as CaCl? solution (to extract soluble metals in soil that are available to plants), respectively. Elemental analyses were performed using inductively coupled plasma mass spectrometry (ICP-MS). Overall, plant available metals were greater in soils amended with MSS compared to control plots. Concentration of Pb was greater in YW than MSS amendments. Total concentrations of Pb, Ni, and Cr were greater in plants grown in MSS+YW treatments compared to control plants. MSS+YW treatments increased sweet potato yield, ascorbic acid, soluble sugars, and phenols in edible roots by 53, 28, 27, and 48%, respectively compared to plants grown in native soil. B-carotene concentration (157.5 μg g?1 fresh weight) was greater in the roots of plants grown in MSS compared to roots of plants grown in MSS+YW treatments (99.9 μg g?1 fresh weight). Concentration of heavy metals in MSS-amended soil and in sweet potato roots were below their respective permissible limits.     

Metal accumulation in aquatic macrophytes from southeast Queensland,Australia

To determine the extent of metal accumulation in some aquatic macrophytes from contaminated urban streams in southeast Queensland, plants were sampled from six sites, along with contiguous sediments. In all, 15 different species were collected, the most common genera being Typha (Cattails or Bulrushes) and Persicaria (Knotweeds). Before heavy metal analysis, plants were further separated into various morphological tissues, and five selected samples were separated into various physiological tissues. The cadmium, copper, lead and zinc content of the plants were analysed using flames AAS. In general, plant roots exhibited higher metal concentrations than the contiguous sediments. Of the metals of interest, only for zinc was there a relatively clear pattern of increasing accumulation in aquatic macrophytes with increasing sediment metal concentrations. Comparison between morphological tissues of the sampled plants found that roots consistently presented higher metal concentrations than either the stems or leaves, however unlike previous studies, this investigation revealed no consistent trend of stems accumulating more metals than the leaves. For Typha spp., metal concentrations followed the order of roots > rhizomes > leaves, while for Persicaria spp. the order was roots > leaves > stems. The submerged species Myriophyllum aquaticum accumulated the highest levels of metals overall (e.g. Zn 4300 micrograms g-1 dry weight and Cd 6.5 micrograms g-1), and the emergent macrophytes also exhibited relatively high metal contents in their roots. The leaves of the submerged and floating-leafed species collected contained relatively high quantities of the four metals of interest, compared with the leaves of emergent aquatic macrophytes. In the Typha rhizome and Persicaria stem samples analysed for internal variation in metal content, there was a pattern of increasing metal concentrations towards the external sections of the stem, both for subterranean stems (rhizomes) and above-substrate stems. For Persicaria stems, no clear pattern was observed for cadmium and lead, the two metals investigated that are not required by plants for survival.