根迹土壤根诱导的化学变化对植物吸收重金属的影响

It is increasingly recognized that metal bioavailability is a better indicator of the potential for phytoremediation than the total metal concentration in soils; therefore, an understanding of the inffuence of phytoremediation plants on metal dynamics at the soil-root interface is increasingly vital for the successful implementation of this remediation technique. In this study, we investigated the heavy metal and soil solution chemical changes at field moisture, after growth of either Indian mustard (Brassica juncea) or sunffower (Helianthus annuus L.), in long-term contaminated soils and the subsequent metal uptake by the selected plants. In addition, the fractions of free metal ions in soil solution were determined using the Donnan membrane technique. After plant growth soil solution pH increased by 0.2-1.4 units and dissolved organic carbon (DOC) increased by 1-99 mg L^-1 in all soils examined. Soluble Cd and Zn decreased after Indian mustard growth in all soils examined, and this was attributed to increases in soil solution pH (by 0.9 units) after plant growth. Concentrations of soluble Cu and Pb decreased in acidic soils but increased in alkaline soils. This discrepancy was likely due to a competitive effect between plant-induced pH and DOC changes on the magnitude of metal solubility. The fractions of free Cd and Zn ranged from 7.2% to 32% and 6.4% to 73%, respectively, and they generally decreased as pH and DOC increased after plant growth. Metal uptake by plants was dependant on the soil solution metal concentration, which was governed by changes in pH and DOC induced by plant exudates, rather than on the total metal concentrations. Although plant uptake also varied with metal and soil types, overall soluble metal concentrations in the rhizosphere were mainly inffuenced by root-induced changes in pH and DOC which subsequently affected the metal uptake by plants.     

堆肥, 石灰和磷酸二铵对铜尾矿土壤重金属的植物有效性的影响

Soil samples from a historic copper mine tailing site at the Parys Mountain,North Wales (UK) were amended with green waste compost (GC),GC+30% sewage sludge (GCS),lime and diammonium phosphate (DAP),to determine the effect of amendments on DTPA-and Ca (NO₃) ₂-extractable metals in the mine tailing and on the phytoavailability of heavy metals by a lettuce (Lactuca sativa L.).Both compost were added at the rate of 10% by weight,lime was added as calcium carbonate equivalent (pH = 7) and DAP at a 2300 mg kg^-1 soil level.The experiment was arranged in randomised complete design with three replicates in pots under control environment.Addition of lime resulted in the largest reduction in metal extractability with DTPA and Ca (NO₃) ₂ and phytoavailability of Cu,Fe and Zn while DAP was effective in lowering Pb extractability and phytoavailability.With exception of Zn,all other metals extracted decreased with time after amendment applications.The distribution of heavy metals between and within the four procedures of potentially bioavailable sequential extraction (PBASE) varied significantly (P < 0.001).Stronger relationships were noted between the metals extracted with PBASE SE1 and Cu,Pb (P < 0.01) and Fe (P < 0.001) in the lettuce.These results indicate that addition of lime is sufficient to restore the vegetative cover to a high metal mine waste while DAP is good for stabilizing Pb,but its detrimental role on plant growth and the risk associated with presence of N in DAP (through N leaching) may restrict its chances for remediation of contaminated sites.     

两种矿山生态型香薷对铜的吸收、分布和积累特性研究

Two ecotypes of Elsholtzia, Elsholtzia splendens and E. argyi, are dominant plants growing on Cu and Pb-Zn smelters, respectively. Samples of the two ecotypes and the corresponding soils from fields of a copper mining area and a Pb-Zn mining area of Zhejiang Province, China, were analyzed to investigate Cu or Zn tolerance of these two ecotypes. Effects of nine Cu levels (0, 5, 10, 20, 40, 80, 160, 240 and 320 mg Cu L^-1 as CuSO₄·5H₂O) on growth and uptake, translocation and accumulation of Cu in these two ecotypes were examined in a solution culture experiment. The experimental results showed that dry weights (DW) of shoots and roots were depressed, and growth of E. splendens was less depressed than that of E. argyi when treated with ≥ 5 mg Cu L^-1. Concentrations of Cu in shoots of E. splendens and E. argyi exceeded 1 000 mg kg^-1 DW at ≥ 40 mg Cu L^-1. The maximum Cu accumulated in the shoots of Cu-treated E. splendens and E. argyi reached 101 and 142 μg plant^-1. Furthermore, analysis of plant samples from the fields showed that these two ecotypes can tolerant excess heavy metals and produced high dry matter, and E. splendens can accumulate 11.7 mg Cu plant^-1 grown on the Cu smelter. Therefore, E. splendens and E. argyi could be good plants for phytoremediation.     

大棚土壤接种丛枝菌根真菌增强黄瓜枯萎病抑制水平

A pot experiment was conducted to study the plant growth and fruit yields of cucumber (Cucumis sativus L.) on a greenhouse soil with or without inoculation of arbuscular mycorrhizal fungi (AMFs) and Fusarium oxysporum f. sp. cucumerinum under unsterilized conditions. Two AMF inocula were tested: only one AMF strain Glomus caledonium 90036 and an AMF consortium mainly consisting of Glomus spp. and Acaulospora spp. There were four treatments including no inoculation (control), inoculation with F. oxysporum but without mycorrhizae (FO), inoculation with F. oxysporum and G. caledonium (FO+M1), and inoculation with F. oxysporum and the AMF consortium (FO+M2). Cucumber plants were harvested at weeks 3 and 9 after transplanting. Compared with the control, the FO treatment without AMF inoculation had less biomass both at weeks 3 and 9 (P < 0.05) and had higher incidence of Fusarium wilt and produced no cucumber fruit at week 9. Both FO+M1 and FO+M2 treatments had higher mycorrhizal colonization than the treatments which received no AMF inoculation at week 3 (P < 0.05), but only the FO+M2 treatment elevated plant biomass, decreased the incidence of Fusarium wilt, and improved cucumber yields to the same level as the control at week 9. The results indicated that the AMF consortium could suppress Fusarium wilt of cucumber and, therefore, showed potential as a biological control agent in greenhouse agroecosystems.     

三种植被类型植物根系对崇明岛海岸带稳定性的影响

Coastal erosion is currently a major problem along the southern coast of Chongming Island, Shanghai. To enhance the erosion protection ability of coastal shelterbelts, two woody tree species, Taxodium ascendens and Salix babylonica, were planted separately into Phragmites australis + Scirpus mariqueter communities in 2006. Two years later, we investigated whether either of these experiments reduced erosion and increased stability in the native herbaceous plant community. We also examined soil stability and root length density under T. ascendens added, S. babylonica added and native herbaceous vegetation conditions along an intertidal gradient from the soil surface to a depth of 40 cm in each experiment, thus to determine the capacity of T. ascendens and S. babylonica to contribute to shoreline stabilization. Topsoil under the native vegetation had greater stability at the middle and higher intertidal zones because its soil stability index and root length density were significantly higher than in the T. ascendens or S. babylonica planted communities. The effect of T. ascendens on soil stability was not generally better than that of the native vegetation. Only at the 20-30 cm soil depth of the middle intertidal zone and in the 10-20 cm layer of the higher intertidal zone the soil stability index and root length densities under the T. ascendens added condition were significantly higher (P < 0.05) than those of the native vegetation. The S. babylonica planted soil had greater stability in the deeper soil layer than the soil under either the native vegetation or the T. ascendens added condition, and its soil stability index and root length density were significant higher (P < 0.05) than those of other vegetation conditions at the 30-40 cm soil depth for the lower intertidal zone and at the 20-40 cm layer for middle and higher intertidal zones.     

热带土壤上连续9年施入污水污泥后重金属Zn, Cd和Pb的分离研究

A long-term field experiment was carried out in the experiment farm of the Sao Paulo State University, Brazil, to evaluate the phytoavailability of Zn, Cd and Pb in a Typic Eutrorthox soil treated with sewage sludge for nine consecutive years, using the sequential extraction and organic matter fractionation methods. During 2005-2006, maize (Zea mays L.) was used as test plants and the experimental design was in randomized complete blocks with four treatments and five replicates. The treatments consisted of four sewage sludge rates (in a dry basis) : 0.0 (control, with mineral fertilization), 45.0, 90.0 and 127.5 t ha^-1, annually for nine years. Before maize sowing, the sewage sludge was manually applied to the soil and incorporated at 10 cm depth. Soil samples (0-20 cm layer) for Zn, Cd and Pb analysis were collected 60 days after sowing. The successive applications of sewage sludge to the soil did not affect heavy metal (Cd and Pb) fractions in the soil, with exception of Zn fractions. The Zn, Cd and Pb distributions in the soil were strongly associated with humin and residual fractions, which are characterized by stable chemical bonds. Zinc, Cd and Pb in the soil showed low phytoavailability after nine-year successive applications of sewage sludge to the soil.     

磁性土壤中Cu和Zn污染的指示作用

Concentrations of copper （Cu） and zinc （Zn） and various magnetic parameters in contaminated urban roadside soils were investigated using chemical analysis and magnetic measurements. The results revealed highly elevated Cu and Zn concentrations as well as magnetic susceptibility in the roadside soils. The mean concentrations of Cu and Zn in these roadside soils were almost twice those in average Chinese soils, with the mean magnetic susceptibility of the roadside soils reaching about 179 ×10^-8 m^3 kg^-1. This enhanced magnetic susceptibility was attributed to the presence of anthropogenic soft ferrimagnetic particles. A low frequency-dependent susceptibility （2.5%± 1.0%） observed in the roadside soils indicated the coarse multidomain （MD） ferrimagnetic grains to be the dominant contributor to magnetic susceptibility. The Cu and Zn concentration of the soils had highly significant linear correlations with magnetic susceptibility （P 〈 0.01）, anhysteretic remanent magnetization （P 〈 0.01）, and saturation isothermal remanent magnetization （P 〈 0.01）. This suggested that heavy metals were associated with ferrimagnetic particles in soils, which were attributed to input of traffic emissions and industrial activities. Scanning electron microscopy and energy dispersive X-ray spectra of magnetic extracts of the roadside soils further suggested the llnk between the magnetic signal and concentrations of heavy metals. Thus, the magnetic parameters could provide a proxy measure for the level of heavy metal contamination and could be a potential tool for the detection and mapping of contaminated soils.     

高产生物能植物蓖麻作为铜污染土壤上潜在植物修复剂

Copper (Cu) contamination in the environment has been increased during the years with agricultural and industrial activities.Biotechnological approaches are needed for bioremediation in these areas. The aims of this study were i) to evaluate the phytoremediation capacity of the high-yielding bioenergy plant castor bean (Ricinus communis L.) in vineyard soils (Inceptisol and Mollisol) contaminated with Cu and a Cu mining waste; ii) to characterize the castor bean as a Cu phytoremediation plant; and iii) to evaluate the nutrient uptake by castor bean. Castor bean plants cultivated in soil with toxic levels of Cu for 57 d exhibited high phytomass production, a high tolerance index of roots’ fresh mass and shoots’ dry mass, a high level of Cu phytoaccumulation in the roots and also, a robust capacity for Cu phytostabilization. Furthermore, castor bean plants did not significantly deplete soil nutrients(such as N, P, and Mg) during cultivation. Plants cultivated in Inceptisol, Mollisol and Cu mining waste exhibited a strong potential for Cu phytoaccumulation, with values of 5 900, 3 052 and 2 805 g ha-1, respectively. In addition, the castor bean’s elevated phytomass production and strong growth in Cu-contaminated soils indicated a high level of Cu phytoaccumulation and a potential application in biofuels. These findings indicate that the castor bean is a efcient hyperaccumulator of Cu and a potential candidate plant for the phytoremediation of Cu-contaminated soil.     

施用碱稳定污泥污水土壤经γ-辐照后土壤溶液中Cu和Zn的变化

A glasshouse pot experiment was conducted to study changes in the solubility of copper and zinc in the soil-plant system following heavy application of sewage sludge and partial sterilisation of the sludge/soil mixture. A slightly acid sandy loam was mixed with alkaline stabilised and composted urban sewage sludge solids (Agri-Soil, 180 t hm^-2), and the soil/sludge mixture was-irradiated (10 kGy). The contrasts without the application of sewage sludge and-irradiation were also included in the experiment. Perennial ryegrass (Lolium perenne cv. Magella) was grown on irradiated and unirradiated soils for 50 days. Soil solution samples were obtained using soil suction samplers immediately before plant transplantation and every ten days thereafter. The soil solution samples were used directly for determination of Cu and Zn, toget her with pH, electrical conductivity (EC) and absorbance at wavelength 360 nm (A₃₆₀). Applicat ion of Agri-Soil led to a substantial increase in dissolved Cu and a significant decrease in dissolved Zn in the soil solution and these effects were accompanied by increased soil solution pH, EC and A₃₆₀. The alkaline sludge product (Agri-Soil) in combination with-irradiation also led to a pronounced elevation of Cu and A₃₆₀ but a marked decline in EC, indicating an increase in dissolved organic compounds and a decrease in the ionic strength of the soil solution. The dissolved Cu and Zn, EC and A₃₆₀ usually decreased while the pH increased after plant grow th for 50 days.     

土地利用方式和施肥对潮棕壤氨氧化细菌活性和群落组成的影响

The effects of long-term (19 years) different land use and fertilization on activity and composition of ammonia-oxidizing bacteria (AOB) in an aquic brown soil were investigated in a field experiment in Liaoning Province, China. The 19-year experiment conducted from 1990 to 2008 involved seven treatments designed: cropping rotation of soybean-corn-corn with no fertilizer (control, CK), recycled manure (RM), fertilizer nitrogen (N), phosphorous (P) and potassium (K) (NPK), NPK+RM, and no-crop bare land, mowed fallow, and non-mowed fallow. The results showed that the potential nitrification rates of the RM, NPK+RM, mowed fallow, and non-mowed fallow treatments were significantly higher (P < 0.05) than those of the CK and NPK treatments, indicating that the long-term applications of recycled manure and return of plant residues both significantly increased the activity of AOB. Although the application of NPK did not enhance soil potential nitrification because of decreased pH, available K had an important effect on potential nitrification. Denaturing gradient gel electrophoresis (DGGE) fingerprint profiles showed that no-crop treatments had an increase in the diversity of the AOB community compared to the CK, RM, and NPK treatments, implying that agricultural practices, especially tillage, had an adverse effect on the soil AOB community. The NPK+RM treatment had the most diverse DGGE patterns possibly because of the increased available P in this treatment. A phylogenetic analysis showed that most of the DGGE bands derived belonged to Nitrosospira cluster 3, not Nitrosospira cluster 2. These demonstrated that different land use and fertilization significantly influenced the activity and composition of the AOB community by altering the soil properties, mainly including pH, total C, available K, and available P.     

4种改良剂对铅锌尾矿污染土壤中光叶紫花苕生长及重金属吸收特性的影响

通过盆栽试验研究了铅锌尾矿污染土壤中施用有机肥、石灰、蛭石和白云石等4种改良剂对光叶紫花苕生长发育、叶绿素及重金属Cu、Cd、Pb、Zn积累特性的影响,并分析了施用改良剂后土壤pH和有效态重金属含量的变化。结果表明,与对照相比,不同改良剂及其不同施用水平均能不同程度地提高土壤pH,显著降低土壤各重金属有效态含量,并显著抑制了Cd、Pb向光叶紫花苕地上部转移,降低了重金属在光叶紫花苕植株地上部的积累,改善了光叶紫花苕的生长和发育,光叶紫花苕株高、地上部鲜重和地下部鲜重、叶绿素含量均有不同程度增加,其中株高和地上部鲜重增加达到显著水平。4种改良剂的不同处理水平对光叶紫花苕地下部重金属含量影响均达显著水平。     

Arbuscular mycorrhizal fungi mediated uptake of nutrient elements by Chinese milk vetch (<Emphasis Type="Italic">Astragalus sinicus</Emphasis> L.) grown in lanthanum spiked soil

A greenhouse experiment was conducted to study the effect of mycorrhizal colonization by Gigaspora margarita, Glomus intraradices, and Acaulospora laevis on nutrient uptake of K, Ca, Mg, Cu, Zn, Fe, and Mn by Astragalus sinicus L. in soils spiked with lanthanum at five rates (0, 1, 5, 10, and 20 mg kg⁻¹). Lanthanum application significantly decreased the concentrations of K, Ca, Mg, Cu, Zn, and Fe in shoots and the concentrations of Cu and Zn in roots. Mycorrhizal treatments markedly improved uptake of nutrients, and these results are important since nutrient deficiency often occurs in contaminated sites.     

Effect of biodegradable chelating agents on heavy metals phytoextraction with Mirabilis jalapa and on its associated bacteria

The application of chelating agents can be associated with phytoremediation in order to reduce the time required for remediation of heavy metal contaminated soils. The present work has the purpose to test the use of easily biodegradable chelating agents in the assisted phytoextraction process and to evaluate their effect on soil and Mirabilis jalapa plant associated bacteria. Two easily biodegradable chelating agents were used (EDDS and MGDA) in two different dosages (4 and 8 mmol/kg of soil). Metal concentration in soil solution, in leaves and in leachate were determined during the phytoextraction process, while at the end of the experiment metal concentration was evaluated separately in roots, stalk and leaves. In untreated reactors Zn and Pb were accumulated in the roots, but only Zn was translocated to the shoots. Both chelating agents demonstrated to be very effective in Pb and Zn mobilization in soil solution. After chelate treatment, accumulation and translocation of the two metals was different: unaffected with regard to Zn and enhanced with regard to Pb. The chelating agents seem to have a positive influence on bacterial communities of bulk soil and rhizosphere by mitigating the selective pressure caused by Pb and Zn, whereas the endophytes are less affected.     

Arsenic and Heavy Metal Uptake and Accumulation in Native Plant Species from Soils Polluted by Mining Activities

Arsenic and heavy metal (specifically Cd, Cr, Cu, Ni, Pb, and Zn) uptake, translocation, and accumulation in ten native plant species spontaneously growing in soils polluted by mining activities were studied, with a focus on future phytoremediation work in polluted soils. Plant and soil samples were collected in the vicinity of the Mónica mine (NW Madrid, Spain). Soil analysis showed the ability of native plants for growing in soils with high concentration levels of Cd, Cu, Pb, Zn, and especially As. From these elements, the highest percentage of extractable elements was found for Cd and the lowest for Pb. A highly significant correlation was observed between total and extractable element concentrations in soils, except for Cu, indicating that total concentration is the most relevant factor for element mobility in these soils. Extractable elements in soils were better correlated with concentrations in plants than total elements in soils; thus, extraction methods applied are suitable to estimate the element phytoavailable fraction in soils, which depends on the plant species and not only on the element mobility in soils. High element concentrations were found in the aboveground parts of Corrigiola telephiifolia (As and Pb), Jasione montana (Cd and Zn), and Digitalis thapsi (As, Cd, Cu, Pb and Zn). However, considering the translocation and accumulation factors, together with the concentration levels found in roots and aboveground parts, only C. telephiifolia could be considered a Pb accumulator and an As hyperaccumulator plant, which could be used for future phytoremediation work in soils polluted with As.     

EDDS对海州香薷修复重金属复合污染土壤的田间效应

两年田间小区试验研究了加入易降解络合剂EDDS后污染土壤及修复植物海州香薷地上部Cu、Zn、Pb含量及地下水水质变化。结果显示,添加EDDS能在一定程度上提高海州香薷对Cu、Zn、Pb的吸收量,但是对地下水水质影响不大,符合国家III类地下水水质标准。EDDS强化海州香薷修复复合污染土壤有一定的应用前景,且对于地下水的潜在淋滤风险较小,但是在应用期间应注意对环境因素特别是降水及地下水的影响。     

Heavy‐metal mobilization and uptake by mycorrhizal and nonmycorrhizal willows (Salix × dasyclados)

Ectomycorrhizal fungi have been shown to affect metal transfer from the soil to the host plant, but the use of these fungi for increased phytoextraction of heavy metals has been scarcely investigated. Therefore, a two‐factorial pot experiment was conducted with Salix × dasyclados and (1) two contaminated soils with different concentrations of NH₄NO₃‐extractable metals and (2) two strains of the ectomycorrhizal fungus Paxillus involutus (one strain originating from a noncontaminated site—Pax1, and another from a contaminated site—Pax2). The inoculation with Pax2 increased the phytoavailability of Cd in the soils. Inoculation with both fungal strains increased the stem and root biomass, but had no effect on metal concentrations in the stems. Decreased Cd and increased Cu concentrations were observed in the roots of inoculated willows. The inoculation with P. involutus increased Cd (up to 22%), Zn (up to 48%), and Cu content in the stems. Decreased Pb content (Cu and Pb content were always <1 mg per plant) occurred in the stems from plants at the soil with the higher concentration of NH₄NO₃‐extractable metals. Contrary to this, in the soil with lower concentrations of NH₄NO₃‐extractable metals, the inoculation had no significant effects on the total uptake of Zn and Cu and even caused decreased Cd (Pax2) and Pb (Pax1) contents in the stems. Strain Pax2 had higher colonization densities, but the plants had lower mycorrhizal dependencies in the contaminated soils than after inoculation with the strain Pax1. Generally, metal extractability in the soils substantially affected the mycorrhizal dependency and heavy‐metal uptake of the willows. We concluded, that the inoculation with P. involutus offers an opportunity to particularly increase the phytoextraction of Zn, but the metal extractability and fungal strain effects have to be tested.     

Accumulation of Copper,Lead, and Zinc by In Situ Plants Inoculated with AM Fungi in Multicontaminated Soil

Pot and field experiments were conducted to (1) evaluate bioavailability of copper (Cu), lead (Pb), and zinc (Zn) in contaminated soil and phytoremediation potential by in situ plants, B. pilosa var. radiate and Passiflora foetida var. hispida, as inoculated with arbuscular mycorrhizal (AM) fungi, and (2) compare the results of pot and field experiments. The B. pilosa var. radiate plant inoculated with AM fungi had significantly greater Cu concentrations in the shoots and roots than noninoculated plants. Passiflora foetida var. hispida plant inoculated with AM fungi also had significantly greater Cu and Pb concentrations in the roots than noninoculated plants. As the root dry weight of Passiflora foetida var. hispida inoculated with AM fungi dramatically increased, the root Cu, Pb, and Zn content of Passiflora foetida var. hispida inoculated with AM fungi increased by 9–14 times, as compared with the noninoculated plants. The AM fungi have potential to either promote plant growth or increase heavy‐metal accumulation. The values of element translocation proportion from root to shoot were Zn > Cu > Pb for both plant species in pot and field experiments. For both plant species, the results of the pot and field experiments were significantly different. The concentration values of the pot experiment were greater in comparison to the field experiment, and some values were significantly greater than those in the field experiment.     

Effects of multiple heavy metal contamination and repeated phytoextraction by Sedum plumbizincicola on soil microbial properties

The threat of heavy metal contamination to food and human health in south and east China has become a public concern as industrial development continues. The aims of this study were to investigate the influence of repeated phytoextraction over a two-year period by successive crops of the Zn and Cd hyperaccumulator Sedum plumbizincicola on multiple metal contaminated soils and to assess recovery of soil quality. Total and NH₄OAc-extractable Zn and Cd concentrations were significantly reduced in planted soils compared to unplanted soils. Microbial biomass C (C_mic), basal respiration and microbial quotient (qM) were significantly and positively correlated and soil metabolic quotient (qCO₂) was negatively correlated with heavy metal concentrations in unplanted soils (P < 0.05). However, C_mic, basal respiration and qM values increased significantly after phytoremediation by five crops over two years compared to unplanted soil. Urease, β-glucosidase, neutral phosphatase and arylsulfatase activities also increased significantly with decreasing heavy metal contents and hydrolase activity was enhanced in planted soil (P < 0.05) compared to the unplanted control. The data indicate the capacity of S. plumbizincicola to extract Zn and Cd from contaminated soil and also that phytoremediation had beneficial effects on soil microbial and hydrolase activities, with the metal phytoextraction procedure restoring soil quality.     

The transfer of heavy metals to barley plants from soils amended with sewage sludge with different heavy metal burdens

Purpose

Our main aim objective was to evaluate the transfer of Cd, Cr, Cu, Ni, Pb and Zn to barley (Hordeum vulgare) grown in various soils previously amended with two sewage sludges containing different concentrations of heavy metals. This allowed us to examine the transfer of heavv metals to barley roots and shoots and the occurrence of restriction mechanisms as function of soil type and for different heavy metal concentration scenarios.

Material and methods

A greenhouse experiment was performed to evaluate the transfer of heavy metals to barley grown in 36 agricultural soils from different parts of Spain previously amended with a single dose (equivalent to 50 t dry weight ha^?1) of two sewage sludges with contrasting levels of heavy metals (common and spiked sludge: CS and SS).

Results and discussion

In soils amended with CS, heavy metals were transferred to roots in the order (mean values of the bio-concentration ratio in roots, BCF_Roots, in brackets): Cu (2.4)?~?Ni (2.3)?>?Cd (2.1)?>?Zn (1.8)?>?Cr (0.7)?~?Pb (0.6); similar values were found for the soils amended with SS. The mean values of the soil-to-shoot ratio were: Cd (0.44)?~?Zn (0.39)?~?Cu (0.39)?>?Cr (0.20)?>?Ni (0.09)?>?Pb (0.01) for CS-amended soils; Zn (0.24)?>?Cu (0.15)?~?Cd (0.14)?>?Ni (0.05)?~?Cr (0.03)?>?Pb (0.006) for SS-amended soils. Heavy metals were transferred from roots to shoots in the following order (mean values of the ratio concentration of heavy metals in shoots to roots in brackets): Cr (0.33)?>?Zn (0.24)?~?Cd (0.22)?>?Cu (0.19)?>?Ni (0.04)?>?Pb (0.02) for CS-amended soils; Zn (0.14)?>?Cd (0.09)?~?Cu (0.08)?>?Cr (0.05)?>?Ni (0.02)?~?Pb (0.010) for SS-amended soils.

Conclusions

Soils weakly restricted the mobility of heavy metals to roots, plant physiology restricted the transfer of heavy metals from roots to shoots, observing further restriction at high heavy metal loadings, and the transfer of Cd, Cu and Zn from soils to shoots was greater than for Cr, Ni and Pb. Stepwise multiple linear regressions revealed that soils with high sand content allowed greater soil-plant transfer of Cr, Cu, Pb and Zn. For Cd and Ni, soils with low pH and soil organic C, respectively, posed the highest risk.     

Improvement of phytoremediation effects with help of different fertilizer

Abstract

Phytoremediation is increasingly used to remediate metal contaminated soils. However, in order to provide technically efficient phytoremediation of contaminated sites the plant yield and metal uptake have to be enhanced dramatically. The aim of the study was to find appropriate combination of plant species and fertilizers capable of improving yields of the plants and stimulate a transfer of metals to more available to the plants forms. Wheat Triticum vulgare was used for the phytoremediation research. To increase yield of crops and enhance mobility of metals in the rhizosphere the soils were amended with three fertilizers (urea, horse manure, and “ispolin”). Short-term (36 d) vegetation test showed that concentrations of heavy metals in the plants grown in contaminated soil (from site 2) were significantly higher than those in the plants grown in clean soil (from site 1). Growth of wheat resulted in a decrease of Cd content in the soil. Amendment of the contaminated soil with urea enhanced the effect and the decrease of Cd concentration in the soil was more significant. The best effect was demonstrated after application of ispolin: concentrations of Cd, Cu, Pb, and Zn in the rhizosphere decreased 1.2–1.4 times as compared with those in the initial contaminated soil (the decrease was statistically significant).