Bush bean (Phaseolus vulgaris) was exposed to atmospheric deposition of As, Cd and Pb in a polluted and a reference area. The atmospheric deposition of these elements was significantly related to the ...concentrations in leaves, stems and pods at green harvest. Surprisingly there was also a clear relation for As and Pb in the seeds at dry harvest, even though these seeds were covered by the husks. Root uptake of accumulated atmospheric deposits was not likely in such a short term experiment, as confirmed by the fact that soil pore water analysis did not reveal significant differences in trace element concentrations in the different exposure areas. For biomonitoring purposes, the leaves of bush bean are the most suitable, but also washed or unwashed pods can be used. This means that the obtained relationships are suitable to estimate the transfer of airborne trace elements in the food chain via bush bean.
•Atmospheric deposition of trace elements accumulates in bean leaves, stems and pods.•Also thoroughly washed green pods are suitable for biomonitoring.•Even the non-exposed bean seeds accumulate As and Pb deposits to some extend.•A migration of trace elements from the husks to the seeds is most likely.
In a polluted area, atmospheric deposition of trace elements on the above-ground plant parts is influencing their concentration, even in the seeds.
Phytoextraction has been proposed as an alternative remediation technology for soils polluted with heavy metals or radionuclides, but is generally conceived as too slow working. Enhancing the ...accumulation of trace pollutants in harvestable plant tissues is a prerequisite for the technology to be practically applicable. The chelating aminopolycarboxylic acid, ethylene diamine tetraacetate (EDTA), has been found to enhance shoot accumulation of heavy metals. However, the use of EDTA in phytoextraction may not be suitable due to its high environmental persistence, which may lead to groundwater contamination. This paper aims to assess whether ethylene diamine disuccinate (EDDS), a biodegradable chelator, can be used for enhanced phytoextraction purposes. A laboratory experiment was conducted to examine mobilisation of Cd, Cu, Cr, Ni, Pb and Zn into the soil solution upon application of EDTA or EDDS. The longevity of the induced mobilisation was monitored for a period of 40 days after application. Estimated effect half lives ranged between 3.8 and 7.5 days for EDDS, depending on the applied dose. The minimum observed effect half life of EDTA was 36 days, while for the highest applied dose no decrease was observed throughout the 40 day period of the mobilisation experiment. Performance of EDTA and EDDS for phytoextraction was evaluated by application to
Helianthus annuus. Two other potential chelators, known for their biodegradability in comparison to EDTA, were tested in the plant experiment: nitrilo acetic acid (NTA) and citric acid. Uptake of heavy metals was higher in EDDS-treated pots than in EDTA-treated pots. The effects were still considered insufficiently high to consider efficient remediation. This may be partly due to the choice of timing for application of the soil amendment. Fixing the time of application at an earlier point before harvest may yield better results. NTA and citric acid induced no significant effects on heavy metal uptake.
Developing new sources of organic Se has potential benefit for animal production and human nutrition via animal-based foods enriched in Se. The objectives of this trial were to compare ...L-selenomethionine with another organic Se source, Se-enriched yeast (SelPlex 2300), and sodium selenite, an inorganic Se source, against a commercial control diet. The effect of source and the dosage of Se supplementation on Se in eggs and blood variables was investigated. Ten treatments were used with 18 laying hens per group. In addition to the control diet, the control diet was supplemented with L-selenomethionine, Se-enriched yeast, or sodium selenite at 0.1, 0.3, or 0.5 mg/kg of Se. The feeding trial lasted 8 wk. Birds in the different treatment groups all showed good performance. At d 0 and 56, Se and glutathione peroxidase (GPx) were analyzed in 10 blood samples per group. After supplementing the diets for 56 d, significantly higher Se levels in serum and egg contents were reached for the Se-supplemented groups compared with the control. Supplementing 0.3 and 0.5 mg/kg of L-selenomethionine or Se-enriched yeast instead of 0.1 mg/kg significantly increased the serum Se levels, whereas no significant increase was found for sodium selenite. No effect of Se source or dosage was observed on serum GPx levels. Selenium in eggs was significantly affected by dosage and source of Se. The Se supplementation level in the feed was reflected in the eggs, with the highest and lowest values for 0.5 and 0.1 mg/kg, respectively, and values in between for the 0.3 mg/kg supplementation level. A dose response was most pronounced for L-selenomethionine, followed by Se-enriched yeast, and was least when Se was added as sodium selenite. It can be concluded that Se from organic sources was more bioavailable than the inorganic Se source as evidenced by blood and egg Se levels. Within the organic Se sources, L-selenomethionine showed higher Se transfer to eggs than Se-enriched yeast.
This study reports results of total arsenic (Astot) and various As species in 75 samples of cereals and cereal products bought on the Belgian market. In addition to rice, the samples were wheat, ...pasta, bread and some breakfast cereals.
The inorganic species arsenite (AsIII) and arsenate (AsV), and the organic As compounds dimethyl arsinate (DMA) and monomethyl arsonate (MA) were the only As species detected. Mean Astot was 0.150 ± 0.089 mg kg−1 in rice and 0.012 ± 0.008 mg kg− in the non-rice cereals. The inorganic arsenic fraction (Asi = AsIII + AsV) dominated in all samples and was in the range 55%–100%. Significantly higher Astot and Asi concentrations were observed in white rice and brown rice compared to Basmati rice. Within the group of non-rice cereals bread and pasta showed significantly lower concentrations compared to wheat. All 30 rice samples were conform to the European maximum limits for Asi, laid down in Commission Regulation (EU) 2015/1006. Although regulatory limits certainly can help to protect consumer health, our results suggest that the currently fixed European maximum levels are, in Belgium, not expected to have any impact on the human exposure to Asi, which is a known carcinogenic substance.
•Asi concentrations in rice were on average 0.107 ± 0.072 mg kg−1 versus 0.012 ± 0.008 mg kg−1 in non-rice cereals.•The inorganic arsenic fraction (Asi = AsIII + AsV) dominated in all samples and was in the range 55%–100% of Astot.•All rice samples under study were conform to the European maximum limits for Asi.•EU MLs for Asi in rice will probably not have any impact on dietary exposure to Asi of the general Belgium population.•Asi intake through cereals by Belgium adults was 0.04 μg kgbw−1 d−1 and 74 times lower than the BMDL0.5 proposed by JECFA.
A soil column leaching experiment was used to gain insight into the long-term metal immobilization capacity of cyclonic ashes (CAH) compared to lime (LIME). Twenty six years of rainfall were ...simulated. Initially, all amended soils were brought to an equal soil pH. This was done to obtain optimal conditions for the detection of metal immobilization mechanisms different from just a pH effect. During the simulation period, soil pH in all treatments decreased in parallel. However, the evolution of metal mobility and phytoavailability showed a clearly distinct pattern. The strong reduction in metal immobilizing efficiency observed in the lime treatment at the end of the simulation period was much less pronounced, or even absent, in the CAH treatments. Moreover, metal accumulation in plants grown on the CAH amended soil was significantly lower compared to the untreated and the lime treated soil. CAH + SS treatment delivered the strongest reductions in metal mobility and bioavailability.
In a soil column leaching experiment, simulating 26 years of rainfall, application of cyclonic ashes resulted in a more durable metal immobilization compared to lime.
Worldwide there are numerous regions where conventional agriculture is affected by the presence of elevated amounts of plant-available trace elements, causing economic losses and food and feed ...quality and safety. The Belgian and Dutch Campine regions are a first-class example, with approximately 700
km
2 diffusely contaminated by historic atmospheric deposition of Cd, Zn and Pb. Primary land use in this region is agriculture, which is frequently confronted with crops exceeding the European standards for heavy metal contents in food and feed-stuffs. Phytoremediation as a soil remediation technology only appears feasible if the produced biomass might be valorised in some manner. In the current case, we propose the use of energy maize aiming at risk-reduction and generation of an alternative income for agriculture, yet in the long run also a gradual reduction of the pollution levels. Since the remediation aspect is demoted to a secondary objective with sustainable risk-based land use as first objective, we introduce the term ‘phytoattenuation’: this is in analogy with ‘natural attenuation’ of organic pollutants in soils where also no direct intended remediation measures but a risk-based management approach is implemented. In the current field experiment, cultivation of energy maize could result in 33,000–46,000
kW
h of renewable energy (electrical and thermal) per hectare per year which by substitution of fossil energy would imply a reduction of up to 21
×
10
3
kg
ha
−1
y
−1 CO
2 if used to substitute a coal fed power plant. Metal removal is very low for Cd and Pb but more significant for Zn with an annual reduction of 0.4–0.7
mg
kg
−1 in the top soil layer.
Remediation of soil pollution is one of the many current environmental challenges. Anthropogenic activity has resulted in the contamination of extended areas of land, the remediation of which is both ...invasive and expensive by conventional means. Phytoextraction of heavy metals from contaminated soils has the prospect of being a more economic in situ alternative. In addition, phytoextraction targets ecotoxicologically the most relevant soil fraction of these metals, i.e. the bioavailable fraction. Greenhouse experiments were carried out to evaluate the potential of four high biomass crop species in their potential for phytoextraction of heavy metals, with or without with the use of soil amendments (EDTA or EDDS). A calcareous dredged sediment derived surface soil, with high organic matter and clay content and moderate levels of heavy metal pollution, was used in the experiments. No growth depression was observed in EDTA or EDDS treated pots in comparison to untreated controls. Metal accumulation was considered to be low for phytoextraction purposes, despite the use of chelating agents. The low observed shoot concentrations of heavy metals were attributed to the low phytoavailability of heavy metals in this particular soil substrate. The mobilising effects induced by EDTA in the soil were found to be too long-lived for application as a soil amendment in phytoextraction. Although EDDS was found to be more biodegradable, higher effect half lives were observed than reported in literature or observed in previous experiments. These findings caution against the use of any amendment, biodegradable or otherwise, without proper investigation of its effects and the longevity thereof.
In a lysimeter set-up, compost addition to an industrial contaminated soil slightly reduced phytotoxicity to bean seedlings. The “Phytotoxicity Index” (on a scale from 1 to 4) decreased from 3.5 to ...2.8. The same treatment also reduced metal accumulation in grasses: mean Zn, Cd and Pb concentrations decreased respectively from 623 to 135, from 6.2 to 1.3 and from 10.7 to <6
mg
kg
−1 dry weight. When combined with inorganic metal immobilizing amendments, compost had a beneficial effect on plant responses additional to the inorganic amendments alone. Best results were obtained when using compost (C)
+
cyclonic ashes (CA)
+
steel shots (SS). The “Phytotoxicity Index” decreased to 1.7, highest diversity of spontaneously colonizing plants occurred, and metal accumulation in grasses reduced to values for uncontaminated soils. Based on the first year evaluation, C
+
CA
+
SS showed to be an efficient treatment for amendment assisted phytostabilization of the contaminated Overpelt soil.
Compost
+
cyclonic ashes
+
steel shots was an effective treatment for amendment-assisted phytostabilization of contaminated soil.
Production of food crops on trace element-contaminated agricultural lands in the Campine region (Belgium) can be problematic as legal threshold values for safe use of these crops can be exceeded. ...Conventional sanitation of vast areas is too expensive and alternatives need to be investigated. Zea mays on a trace element-contaminated soil in the region showed an average yield of 53 ± 10 Mg fresh or 20 ± 3 Mg dry biomass ha−1. Whole plant Cd concentrations complied with legal threshold values for animal feed. Moreover, threshold values for use in anaerobic digestion were met. Biogas production potential did not differ between maize grown on contaminated and non-contaminated soils. Results suggested favorable perspectives for farmers to generate non-food crops profitably, although effective soil cleaning would be very slow. This demonstrates that a valuable and sustainable alternative use can be generated for moderately contaminated soils on which conventional agriculture is impaired.
•Zea mays on trace element-contaminated soil has an average yield of 20 ± 3 Mg DW ha−1.•Whole plant Cd concentrations complied with legal threshold values for animal feed.•Biogas production did not differ from maize grown on non-contaminated soils.•Perspectives are favorable for farmers to generate non-food crops profitably.•Effective soil cleaning would be very slow.
Energy maize cultivation constitutes a sustainable alternative use of trace element-contaminated agricultural soils.
The potential of short rotation coppice (SRC) for phytoremediation of contaminated sites and simultaneous generation of bio-energy by conversion of the produced biomass has been discussed in previous ...publications. The current study compares five species of
Salix spp. in their ability to extract and accumulate heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) in harvestable plant parts. The species used in this study were:
Salix dasyclados ‘Loden’,
Salix triandra ‘Noir de Villaines’,
Salix fragilis ‘Belgisch Rood’,
Salix purpurea
×
Salix daphnoides ‘Bleu’,
Salix schwerinii ‘Christina’. The comparison was conducted in a pot experiment in open air over the course of a growing season on three different soil types: a moderately contaminated dredged sediment derived surface soil (A1), a heavily polluted sediment derived surface soil (A2) and a sandy soil with moderately elevated concentrations due to atmospheric deposition by historic smelter activities (A3). In addition, the effects of soil treatment with 2.5
mmol
kg
−1 ethylene diamine disuccinate (EDDS) on metal accumulation in stems and leaves were evaluated for one
Salix clone (Loden). Of the five clones tested, Christina, Loden and Belgisch Rood exhibited the highest Cd and Zn concentrations and therefore deserve further attention in field validation. A first estimation of the order of magnitude of Cd and Zn that could potentially be annually extracted with these clones, resulted in 5–27
kg
ha
−1 for Zn and 0.25–0.65
kg
ha
−1 for Cd, based on the soil type. However, biomass production in field situations will mainly determine metal removal. Treatment with EDDS exhibited distinct differences in inducing metal removal on the various soils. Uptake of Cd and Zn could not be enhanced in A1, whereas in A2 and A3 removal of these metals could be increased by 50–100% after treatment. In all soils EDDS treatment also had a distinct effect on Cu uptake.
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