Fertilizer amendment for improving the phytoextraction of cadmium by a hyperaccumulator <Emphasis Type="Italic">Rorippa globosa</Emphasis> (Turcz.) Thell

Purpose  

Two main pathways of phytoremediation of heavy metal-contaminated soils are phytostabilization and phytoextraction. Some soil amendments can strengthen phytostabilization or phytoextraction through either reducing heavy metal bioavailability in soil or increasing the heavy metal accumulation capacity of the hyperaccumulator (enhancing heavy metal concentration or shoot biomass of the hyperaccumulator). Urea and chicken manure are often used as fertilizers. This research will explore their effects on a newly found hyperaccumulator, Rorippa globosa (Turcz.) Thell., phytoremediating cadmium (Cd).     

Root system responses of hyperaccumulator Solanum nigrum L. to Cd

Purpose

Though phytoremediation is an important technology for remedying heavy metal-contaminated soils, hyperaccumulation mechanism, especially in root, is still less known.

Materials and methods

Pot culture experiment was used to explore the tolerance mechanism of a cadmium (Cd) hyperaccumulator Solanum nigrum L. by determining the main root traits compared to the non-hyperaccumulator Solanum melongena L. (cultivar name Liaoqie 3) in the same plant family.

Results and discussion

The total root lengths, total root surface areas, and total root volumes of S. nigrum were not significantly decreased (p?<?0.05) compared to their controls when Cd spikes were lower than 20 mg kg^–1. However, the abovementioned three factors of S. melongena were significantly decreased (p?<?0.05) when 20 mg kg^–1 of Cd was spiked. By contrast, S. nigrum showed stronger tolerance to Cd. In addition, S. nigrum showed all Cd hyperaccumulator characteristics, i.e., a Cd hyperaccumulator. S. melongena was a non-Cd hyperaccumulator.

Conclusions

These results indicated that root trait can be a factor of hyperaccumulation because of strong tolerance to Cd.     

Application of bioassays with <Emphasis Type="Italic">Enchytraeus crypticus</Emphasis> and <Emphasis Type="Italic">Folsomia candida</Emphasis> to evaluate the toxicity of a metal-contaminated soil,before and after remediation

Purpose  

A contaminated soil was amended to reduce bioavailability of metals (As, Cd, Cu, Pb, and Zn) and to modify its potential environmental impacts. Reproduction toxicity tests using two different soil invertebrates, Enchytraeus crypticus and Folsomia candida, were used to evaluate efficiency of soil amendments to reduce metal availability.     

Evaluation of the mayfly <Emphasis Type="Italic">Ephoron virgo</Emphasis> for European sediment toxicity assessment

Purpose  

The mayfly Ephoron virgo plays a key role in the ecological recovery in large European rivers. The larvae spend their life in the sediment and are therefore exposed to contaminants in various ways. In this study, the use of E. virgo as a test species for whole sediment bioassays was evaluated. The sensitivity was compared with Hexagenia limbata (a North American mayfly recommended for standard sediment testing). Lead (Pb) was used as a model contaminant.     

Chronic toxicity of contaminated sediments on reproduction and histopathology of the crustacean <Emphasis Type="Italic">Gammarus fossarum</Emphasis> and relationship with the chemical contamination and in vitro effects

Purpose  

The aim of the present study was to investigate possible relationships between the sediment contaminants and the occurrence of intersex in situ. Two of the studied sediments were from polluted sites with increased occurrence of intersex crustaceans (Lake Pilnok, black coal mining area in the Czech Republic, inhabited by the crayfish Pontastacus leptodactylus population with 18% of intersex; creek Lockwitzbach in Germany with Gammarus fossarum population with about 7% of intersex).     

Intercropping with hyperaccumulator plants decreases the cadmium accumulation in grape seedlings

In this experiment, four cadmium (Cd) hyperaccumulator species (Crassocephalum crepidioides, Galinsoga parviflora, Sigesbeckia orientalis, and Solanum nigrum) were intercropped with grape (Vitis vinifera) cuttings together in Cd-containated soil to study the effects of intercropping with the Cd-hyperaccumulator plants on growth and Cd accumulation of grape seedlings. Compared with the monoculture, intercropping with S. nigrum increased the biomass of grape seedlings, but intercropping with the other three hyperaccumulator species decreased the grape seedling biomass. Intercropping with S. nigrum increased chlorophyll a and total chlorophyll contents in leaves of grape seedlings compared with the monoculture, whereas intercropping with the other three hyperaccumulator species showed either a decrease or no effect. Intercropping with hyperaccumulator plants had no significant effects on chlorophyll b and carotenoid contents in leaves of grape seedlings compared with the monoculture. Compared with the monoculture, intercropping with C. crepidioides, G. parviflora, S. nigrum and S. orientalis significantly decreased Cd contents in shoots of grape seedlings by 78.7%, 12.7%, 29.8% and 26.5%, respectively. Therefore, intercropping with hyperaccumulator plants can decrease Cd accumulation in grape, and intercropping with S. nigrum can also promote grape seedling growth.     

Hyperaccumulative property of Solanum nigrum L. to Cd explored from cell membrane permeability,subcellular distribution,and chemical form

Purpose

The aim of this article was to explore the hyperaccumulative property from cell membrane permeability, subcellular distribution, and chemical form of Solanum nigrum L. to Cd compared to the nonhyperaccumulator Solanum melongena L. (cultivar name Liaoqie 3) in the same plant family.

Materials and methods

Soil pot culture experiment was conducted, and the cell membrane permeability, subcellular distribution, and chemical forms of Cd in S. nigrum and S. melongena were determined.

Results and discussion

The results showed that the tolerance of S. nigrum to Cd was higher and owned all Cd hyperaccumulator characteristics. The relative electric conductivities in root and leaf were higher of S. nigrum than S. melongena, but the malondialdehyde concentrations in former were roughly lower than that in latter. Cd concentration ratio in cell wall, NaCl extractable form, and HAc (acetic acid) extractive form were higher in root, stem, and leaf of S. nigrum.

Conclusions

Compared to S. melongena, stronger Cd tolerance, higher cell membrane permeability with intact cell membrane, weak Cd forms in subcellular distribution, and relative lower bioactivity speciation may be part reasons of S. nigrum hyperaccumulating Cd.     

Spatial heterogeneity effects of Zn/Cd-contaminated soil on the removal efficiency by the hyperaccumulator Sedum alfredii

Purpose

We aimed to examine the effects of spatial heterogeneity on Zn/Cd removal efficiency by the Zn/Cd hyperaccumulator Sedum alfredii grown on agricultural soil contaminated with mine waste.

Materials and methods

Field-collected metal-contaminated agricultural soils were arranged in pots either homogeneously or heterogeneously in “half” or “quarter” patterns. Young shoots of S. alfredii were grown on these substrates in a greenhouse.

Results and discussion

The efficiency of Zn and Cd removal from soil by S. alfredii was highest in the “quarter” pattern heterogeneous treatment, in which the percentages of total soil Zn and Cd extracted were 8.02 and 7.27, respectively. Comparing the two heterogeneous treatments, the amounts of Zn and Cd accumulated in S. alfredii shoots were significantly greater in the “quarter” pattern heterogeneous treatment than in the “half” pattern treatment.

Conclusions

We concluded that the efficiency of Zn/Cd removal increased as the scale of spatial heterogeneity decreased from “half” to “quarter”. These results may have important implications for the efficiency of phytoremediation by hyperaccumulators in the field.     

Biodegradation of pyrene and catabolic genes in contaminated soils cultivated with Lolium multiflorum L

Background, aim, and scope  

In the soil environment, polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) are of great environmental and human health concerns due to their widespread occurrence, persistence, and carcinogenic properties. Bioremediation of contaminated soil is a cost-effective, environmentally friendly, and publicly acceptable approach to address the removal of environmental contaminants. However, bioremediation of contaminants depends on plant–microbe interactions in the rhizosphere. The microorganisms that can mineralize various PAHs have PAH dioxygenase genes like nahAc, phnAc, and pdo1. To understand the fate of pyrene in rhizospheric and non-rhizospheric soils in the presence or absence of Pb, pyrene biodegradation, bacterial community structure, and dioxygenase genes were investigated in a pot experiment.     

Amaranthus Tricolor Has the Potential for Phytoremediation of Cadmium‐Contaminated Soils

Phytoremediation is a developing technology that uses plants to clean up pollutants in soils. To adopt this technology to cadmium (Cd)–contaminated soils efficiently, a Cd hyperaccumulator with fast growth rate and large biomass is required. In the present study, we selected Caryophyllales as a potential clade that might include Cd hyperaccumulators because this clade had a high mean concentration of zinc (Zn), which is in the same element group as Cd. Three species in Caryophyllales and three species in different clades were grown with Cd. Among them, Amaranthus tricolor showed high accumulating ability for Cd under both water‐culture and soil‐culture conditions, whereas Brassica juncea, a known Cd hyperaccumulator, accumulated high concentrations of Cd in shoots only under water‐culture conditions. This result suggests that A. tricolor has Cd‐solubilizing ability in rhizosphere. Because A. tricolor has large biomass and high growth rate, this species could be useful for phytoremediation of Cd‐contaminated fields.     

Enhanced nitrate reduction and current generation by <Emphasis Type="Italic">Bacillus</Emphasis> sp. in the presence of iron oxides

Purpose  

Fe(III) has been reported as a strictly competitive electron acceptor with respect to other substrate reductions by dissimilatory Fe(III)-reducing bacteria (DIRB). However, the effect of Fe(III) oxides on the substrate reduction by other microorganisms remain unknown. The aims of this study were to investigate the effects of iron oxides on the nitrate reduction and current generation by Bacillus sp., in which the nitrate and carbon anodes served as soluble and insoluble electron acceptors, respectively.     

接种微生物对土壤中Cd、Pb、Zn生物有效性的影响

针对提高植物修复土壤重金属污染的效果,以印度芥菜作为重金属富集植物,通过盆栽试验研究了巨大芽胞杆菌和胶质芽胞杆菌的混合微生物制剂(A处理)和黑曲霉发酵液(B处理)对植物修复Cd、Pb、Zn污染土壤的作用效果。结果表明:巨大芽胞杆菌和胶质芽胞杆菌的混合微生物制剂,不仅可以促进富集植物的生长,使其印度芥菜的生物量提高24.73%,并且可促进土壤Cd、Pb、Zn的活化,使土壤Cd、Pb、Zn有效态含量分别提高15.02%、7.65%和2.23%,增强富集植物对土壤的Cd、Pb、Zn富集吸收,使印度芥菜对土壤Cd、Pb、Zn的提取量分别提高52%、121%和23%,显著提高其植物修复效果。从对植物生理生化指标的影响来看,A处理对植株的伤害程度要低于B处理,它是一种有助于植物修复Cd、Pb、Zn污染土壤的微生物制剂,在植物修复领域有较高的利用价值。然而,黑曲霉混合发酵液不适于促进植物修复应用。     

Leachability of cadmium, lead, and zinc in a long-term spontaneously revegetated slag heap: implications for phytostabilization

Purpose

For abandoned slag heaps, the spontaneous establishment of a vegetation cover is usually considered beneficial as it represents a means of phytostabilization. However, for slag containing heavy metals, such a vegetation cover has a potential long-term effect on the fate of the metals. The objective of this study was to investigate how the long-term spontaneous revegetation of a slag heap can affect the fractionation and the leachability of Cd, Zn, and Pb.

Materials and methods

Soils from two plots covered by either Armeria maritima or Agrostis tenuis and a bare plot soil were sampled from a slag heap from a zinc smelting plant and characterized. The Community Bureau of Reference (BCR) sequential extraction scheme was adopted to determine the metal pools. The leachability of Cd, Pb, and Zn was assessed by means of a leaching column experiment.

Results and discussion

Long-term presence of a plant cover increased the proportion of Zn in the most mobile fraction and Pb in the fraction bound to organic matter. Cd distribution was relatively unaffected. Overall, the metal leachability was enhanced in the revegetated soils, notably due to higher organic anion release. However, responses of metal behavior to revegetation depended on the established plant species. The highest leachability of Cd was found in the soil covered by Agrostis tenuis, while the highest leachability of both Zn and Pb was observed in the soil below Armeria maritima.

Conclusions

Any remediation strategy for metal-rich waste dumps by phytostabilization should take into careful consideration the potential long-term mobilization effect of plant establishment on heavy metals. We conclude that, when using pioneer plants for phytostabilization purposes, preference should be given to pseudo-metallophyte over hyperaccumulator species.     

Distribution of As, Cd, Pb, and Zn in redox features of mine-waste impacted wetland soils

Purpose

Wetland soils of the Coeur d??Alene (CdA) River Basin of northern Idaho, USA are contaminated with toxic elements released during mining activities. In this paper, we report results from a multi-scale investigation of total As, Cd, Pb, and Zn distributions along a transect of these contaminated soils.

Materials and methods

Four sites along an 80-m transect were established at the Black Rock Slough wetland in CdA River Basin. The elevation difference between the upslope and lowland site was 1.1?m. Soils were sampled from three depths, down to 45?cm. Redoximorphic features were isolated from the soils and categorized into five types of cemented particles, and Fe-enriched and depleted soil masses. Soils and isolated soil separates were analyzed for total elemental concentration.

Results and discussion

Within soil profiles, contaminants are enriched in surface horizons as compared to the original depositional profiles. Enrichment was more dramatic in the upland sites than the lowland sites. Fe-enriched masses that ranged in size from a few millimeters to several centimeters were also enriched in As, Pb, and Zn. At the smallest scale investigated, five different soil aggregate types ranging in size from 1 to 2?mm in diameter had distinct contaminant associations: Fe-cemented aggregates were elevated in As and Zn; Mn-cemented aggregates had more than five times as much Pb as the bulk soil; root channels were elevated in As; and charcoal particles were elevated in all contaminants, particularly Pb and Cd.

Conclusions

Results show that in wetland soils pedogenic processes differentially distribute contaminants amongst the redoximorphic features. The distribution is affected by landscape position and water table influence. At the pedon scale, there is an enrichment of As, Cd, Pb, and Zn in surface horizons, suggesting that upward flux of contaminants is occurring. This contaminant redistribution should be considered in design of management and remediation strategies.     

Soil contamination by organic and inorganic pollutants at the regional scale: the case of Piedmont,Italy

Background, aim, and scope  

Diffuse soil contamination has often been neglected in scientific literature, as most studies focus on contaminants from point-sources (either of industrial or agricultural origin). However, soil pollution from diffuse sources is recognized as one of the major soil threats by the EU Soil Thematic Strategy. In fact, some pollutants are nowadays ubiquitarious in the soil system, and they have to be considered for the implementation of environmental legislation, the definition of clean-up values in remediation activities and, more generally, for a sustainable management of rural areas. In the literature large scale studies on diffuse contamination are few and scattered and often do not consider a wide range of contaminants, the effect of land use, the vertical variability and the potential natural contribution. Aim of this work was to provide an overview of the diffuse soil contamination on a regional scale for a large set of contaminants. Soil inorganic (Cd, Cr, Ni, Pb, Cu, Zn) and organic contaminants (polychlorinated dibenzo-p-dioxins(PCDD), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs) as well as other soil general parameters were investigated on a 18 × 18 km grid covering a whole Italian region heavily industrialized and intensively cultivated. Soils were sampled at different depths both for natural–undisturbed soil and for agricultural–plow soil. Differences in the trends of investigated contaminants, as a consequence of land use, vertical variability, natural or geogenic origin, relationships among contaminants, and with main soil properties, were explored by means of enrichment factors, bi- and multi-variate statistics.     

Combined bioremediation of soil co-contaminated with cadmium and endosulfan by <Emphasis Type="Italic">Pleurotus eryngii</Emphasis> and <Emphasis Type="Italic">Coprinus comatus</Emphasis>

Purpose

The subjects of this study were to investigate the remediating potential of the co-cultivation of Pleurotus eryngii and Coprinus comatus on soil that is co-contaminated with heavy metal (cadmium (Cd)) and organic pollutant (endosulfan), and the effects of the co-cultivated mushrooms on soil biochemical indicators, such as laccase enzyme activity and bacterial counts.

Materials and methods

A pot experiment was conducted to investigate the combined bioremediation effects on co-contaminated soil. After the mature fruiting bodies were harvested from each pot, the biomass of mushrooms was recorded. In addition, bacterial counts and laccase enzyme activity in soil were determined. The content of Cd in mushrooms and soil was detected by the flame atomic absorption spectrometry (FAAS), and the variations of Cd fractions in soil were determined following the modified BCR sequential extraction procedure. Besides, the residual endosulfan in soil was detected by gas chromatography-mass spectrometry (GC-MS).

Results and discussion

The results indicated that co-cultivation of P. eryngii and C. comatus exerted the best remediation effect on the co-contaminated soil. The biomass of mushroom in the co-cultivated group (T group) was 1.57–13.20 and 19.75–56.64% higher than the group individually cultivated with P. eryngii (P group) or C. comatus (C group), respectively. The concentrations of Cd in the fruiting bodies of mushrooms were 1.83–3.06, 1.04–2.28, and 0.67–2.60 mg/kg in T, P, and C groups, respectively. Besides, the removal rates of endosulfan in all treatments exceeded 87%. The best bioremediation effect in T group might be caused by the mutual promotion of these two kinds of mushrooms.

Conclusions

The biomass of mushroom, laccase activity, bacterial counts, and Cd content in mushrooms were significantly enhanced, and the dissipation effect of endosulfan was slightly higher in the co-cultivated group than in the individually cultivated groups. In this study, the effect of co-cultivated macro fungi P. eryngii and C. comatus on the remediation of Cd and endosulfan co-contaminated soil was firstly reported, and the results are important for a better understanding of the co-remediation for co-contaminated soil.

     

Integrated approach of metal removal and bioprecipitation followed by fungal degradation of organic pollutants from contaminated soils

This study reports the assessment of a novel process combining sequential treatments of a historically contaminated soil from the ACNA site (Cengio, Savona, Italy), a decommissioned industrial area. The soil was leached with 0.5 M citric acid leading to a removal of metals in the following order: Pb (74.2%) > Cu (72.6%) > Zn (40.2%) > Ni (55.7%) > Cd (41.5%) > Cr > (21.7%) Co > (19%) Fe (8.2%) with a concomitant low removal of organic contaminants (12%). The leachate was then incubated with the metal-resistant Klebsiella oxytoca strain BAS-10, capable of using residual citrate to produce an iron gel that co-precipitated metals. Concomitantly, the leached solid waste was bioaugmented with the autochthonous isolate of Allescheriella sp. DABAC 1 leading to a complete degradation of several organic contaminants, including trichlorobenzene, naphtalene, dichloroaniline and pentachloroaniline. The overall removals of organic contaminants by the fungus were 44.3% and 63.8% in non-leached and leached soil.     

Chemical extraction to assess the bioavailability of chlorobenzenes in soil with different aging periods

Purpose  

Bioavailability is mainly influenced by aging and desorption of contaminants in soil. The purpose of this study was to investigate the desorption kinetics of chlorobenzenes (CBs) in soil and to investigate whether chemical extractions are suitable for the bioavailability assessment of CBs in soil.     

Arbuscular mycorrhizal fungi optimize the acquisition and translocation of Cd and P by cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) plant cultivated on a Cd-contaminated soil

Purpose

Fruiting vegetables are generally considered to be safer than other vegetables for planting on cadmium (Cd)-contaminated farms. However, the risk of transferring Cd that has accumulated in the stems and leaves of fruiting vegetables is a major issue encountered with the usage of such non-edible parts. The objective of this study was to resolve the contribution of arbuscular mycorrhizal (AM) fungi to the production of low-Cd fruiting vegetables (focusing on the non-edible parts) on Cd-contaminated fields.

Materials and methods

An 8-week pot experiment was conducted to investigate the acquisition and translocation of Cd by cucumber (Cucumis sativus L.) plants on an unsterilized Cd-contaminated (1.6 mg kg^?1) soil in response to inoculation with the AM fungus, Funneliformis caledonium (Fc) or Glomus versiforme (Gv). Mycorrhizal colonization rates of cucumber roots were assessed. Dry biomass and Cd and phosphorus (P) concentrations in the cucumber shoots and roots were all measured. Soil pH, EC, total Cd, phytoavailable (DTPA-extractable) Cd, available P, and acid phosphatase activity were also tested.

Results and discussion

Both Fc and Gv significantly increased (P?<?0.05) root mycorrhizal colonization rates and P acquisition efficiencies, and thus the total P acquisition and biomass of cucumber plants, whereas only Fc significantly increased (P?<?0.05) soil acid phosphatase activity and the available P concentration. Both Fc and Gv significantly increased (P?<?0.05) root to shoot P translocation factors, inducing significantly higher (P?<?0.05) shoot P concentrations and shoot/root biomass ratios. In contrast, both Fc and Gv significantly decreased (P?<?0.05) root and shoot Cd concentrations, resulting in significantly increased (P?<?0.05) P/Cd concentration ratios, whereas only Gv significantly decreased (P?<?0.05) the root Cd acquisition efficiency and increased (P?<?0.05) the root to shoot Cd translocation factor. Additionally, AM fungi also tended to decrease soil total and phytoavailable Cd concentrations by elevating plant total Cd acquisition and soil pH, respectively.

Conclusions

Inoculation with AM fungi increased the P acquisition and biomass of cucumber plants, but decreased plant Cd concentrations by reducing the root Cd acquisition efficiency, and resulted in a tendency toward decreases in soil phytoavailable and total Cd concentrations via increases in soil pH and total Cd acquisition by cucumber plants, respectively. These results demonstrate the potential application of AM fungi for the production of fruiting vegetables with non-edible parts that contain low Cd levels on Cd-contaminated soils.

     

A non-invasive observation parameter to complement sediment bioassays using <Emphasis Type="Italic">Myriophyllum aquaticum</Emphasis>

Purpose  

The objective of this study was to modify a sediment contact protocol to a multiwell plate exposure system which supplements measurement of the fresh weight change (FWC) using the non-invasive effective quantum yield of energy conversion at photosystem II (PS II) reaction centres (Y(II)) in parallel. Since Y(II) is a functional parameter and FWC represents a whole-plant structural response, the determination of a more pronounced response in one of these parameters may hint at the mode of action of contaminants. By the observation of Y(II) at different time points, extrapolation of effect development over time may be gained from modelling.