Remediating Garden Soils: EDTA-Soil Washing and Safe Vegetable Production in Raised Bed Gardens

Soil remediation is an important practice in the restoration of heavy metal-contaminated soils and reduce the heavy metal exposure of the local population. Here, we investigated the effect of an ex-situ soil washing technique, based on ethylenediaminetetraacetic acid (EDTA) as a chelating agent, on a contaminated Cambisol. Lead, Cd and Zn were investigated in different soil fractions, drainage water and four vegetables from August 2019 to March 2021. Three treatments consisting of (C) contaminated soil, (W) washed soil and (WA) washed soil amended with vermicompost and biochar were investigated in an outdoor raised bed set up. Our results showed that the total and bioavailable metal fractions were significantly reduced but failed to meet Austrian national guideline values. Initial concentrations in the soil leachate increased significantly, especially for Cd. Vegetables grown on the remediated soil took up significantly lower amounts of all heavy metals and were further reduced by the organic amendment, attaining acceptable values within EU guideline values for food safety. Only spinach exceeded the thresholds in all soil treatments. The increase in soil pH and nutrient availability led to significantly higher vegetable yields

The Response of Artificial Aging to Sorption Properties of Biochar for Potentially Toxic Heavy Metals

This paper evaluates the effect of simulated conditions of artificial aging on sorption capacity of two types of biochar. These were produced by slow pyrolysis from different feedstock - beech wood chips (BC A) and garden green waste residues (BC B). Cadmium served as a model for potentially toxic metals. Twenty freeze-thaw cycles were used to simulate physical aging. The determination of biochar physicochemical properties showed main changes in CEC and SA values of aged sorbents. The maximum sorption capacities of aged BC A sorbent were higher by about 26 % and aged BC B sorbent by about 20% compared to Qmax of non-aged biochar. Qmax of aged BC B peaked at 9.4 mg g-1 whereas BC A sorbed significantly less Cd. FT-IR analyses confirmed the changes in structural composition and content of functional groups on biochar surfaces. The artificial physical aging model was assessed as an efficient tool for investigation of natural weathering conditions

Wood-derived-biochar combined with compost or iron grit for in situ stabilization of Cd, Pb, and Zn in a contaminated soil

In situ stabilization of Cd, Pb, and Zn in an Austrian agricultural soil contaminated by atmospheric depositions from a smelter plant was assessed with a pine bark chip-derived biochar, alone and in combination with either compost or iron grit. Biochar amendment was also trialed in an uncontaminated soil to detect any detrimental effect. The pot experiment consisted in ten soil treatments (% w/w): untreated contaminated soil (Unt); Unt soil amended with biochar alone (1%: B1; 2.5%: B2.5) and in combination: B1 and B2.5 + 5% compost (B1C and B2.5C), B1 and B2.5 + 1% iron grit (B1Z and B2.5Z); uncontaminated soil (Ctrl); Ctrl soil amended with 1 or 2.5% biochar (CtrlB1, CtrlB2.5). After a 3-month reaction period, the soil pore water (SPW) was sampled in potted soils and dwarf beans were grown for a 2-week period. The SPW Cd, Pb, and Zn concentrations decreased in all amended-contaminated soils. The biochar effects increased with its addition rate and its combination with either compost or iron grit. Shoot Cd and Zn removals by beans were reduced and shoot Cd, Pb, and Zn concentrations decreased to common values in all amended soils except the B1 soil. Decreases in the SPW Cd/Pb/Zn concentrations did not improve the root and shoot yields of plants as compared to the Ctrl soil

Exploring the Potential Risk of Heavy Metal Pollution of Edible Cultivated Plants in Urban Gardening Contexts Using a Citizen Science Approach in the Project “Heavy Metal City-Zen”

Urban gardening has become increasingly popular, creating green oases in cities; however, many of these activities are undertaken in areas of high traffic density or on ex-brown field sites. As a consequence, there are still some barriers to the adoption of these urban gardening practices for food production. One of the public concerns is the transfer of urban pollutants such as heavy metals into the consumer’s food chain, however, city-wide data is often difficult and expensive to collect. In the citizen science project described herein, we conducted simple citizen-led common collaborative experiments in urban community gardens. These data provided information on the potential risk of heavy metal contaminants and ways in which to mitigate those risks in an urban gardening context. Generally, values were below guideline thresholds, however, at a few garden sites, soil trace metal concentrations (Pb, Cd, Zn) exceeded Austrian recommended limits. Moreover, only at two sites were plant trace metal concentrations shown to be above European food standards limits. Given the citizen’s positive response to the project, we suggest expanding this study to the whole of Vienna, giving newly established gardens a chance to predetermine the risks posed by their local soils

Biochar-Compost Additions Have Strong Short-Term Effects on Carbon and Nitrogen Emissions from an Agricultural Soil

Biochar (BC) application to agricultural soils has become a promising strategy for mitigation of soil-borne greenhouse gas (GHG) emissions, i.e., carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), but little is known about the effects on nitric oxide (NO) and dinitrogen (N2) fluxes. We conducted a short-term field experiment to evaluate the effects of BC with compost and additional fertilizer on different soil GHG fluxes. Application of 1% BC-compost showed no significant effect on CH4 and CO2 fluxes but lowered NO and N2O fluxes compared to the control without BC-compost. The addition of N to BC-compost (0.5% BC-compost + 175 kg N) showed a small mitigation potential for CH4 whereas N2O and NO fluxes significantly increased for one week after the application. The N2:N2O ratio shifted towards N2O production after the application of N-enriched BC-compost. During storage of pure N-enriched BC-compost, high gaseous losses in the form of NO (71.2 ± 2 µg N g−1 h−1), N2O (1319 ± 101 µg N g−1 h−1), and N2 (337.8 ± 93 µg N g−1 h−1) were measured. Approximately 31% of applied N was lost in gaseous form even in the presence of BC. To avoid this, an optimized strategy to balance easily available N from compost and fertilizer with the amount of BC should be developed

Biochar-Compost Additions Have Strong Short-Term Effects on Carbon and Nitrogen Emissions from an Agricultural Soil

Biochar (BC) application to agricultural soils has become a promising strategy for mitigation of soil-borne greenhouse gas (GHG) emissions, i.e., carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), but little is known about the effects on nitric oxide (NO) and dinitrogen (N2) fluxes. We conducted a short-term field experiment to evaluate the effects of BC with compost and additional fertilizer on different soil GHG fluxes. Application of 1% BC-compost showed no significant effect on CH4 and CO2 fluxes but lowered NO and N2O fluxes compared to the control without BC-compost. The addition of N to BC-compost (0.5% BC-compost + 175 kg N) showed a small mitigation potential for CH4 whereas N2O and NO fluxes significantly increased for one week after the application. The N2:N2O ratio shifted towards N2O production after the application of N-enriched BC-compost. During storage of pure N-enriched BC-compost, high gaseous losses in the form of NO (71.2 ± 2 µg N g−1 h−1), N2O (1319 ± 101 µg N g−1 h−1), and N2 (337.8 ± 93 µg N g−1 h−1) were measured. Approximately 31% of applied N was lost in gaseous form even in the presence of BC. To avoid this, an optimized strategy to balance easily available N from compost and fertilizer with the amount of BC should be developed.ISSN:2073-439

How to manage plant biomass originated from phytotechnologies ? Gathering perceptions from end-users

A questionnaire survey was carried out in 4 European countries to gather end-user's perceptions of using plants from phytotechnologies in combustion and anaerobic digestion (AD). 9 actors of the wood energy sector from France, Germany and Sweden, and 11 AD platform operators from France, Germany and Austria were interviewed. Questions related to installation, input materials, performed analyses, phytostabilization and phytoextraction. Although the majority of respondents did not know phytotechnologies, results suggested that plant biomass from phytomanaged areas could be used in AD and combustion, under certain conditions. As a potential advantage, these plants would not compete with plants grown on agricultural lands, contaminated lands being not suitable for agriculture production. Main limitations would be related to additional controls in process’ inputs and end-products and installations that might generate additional costs. In most cases, price of phytotechnologies biomass was mentioned as a driver to potentially use plants from metal-contaminated soils. Plants used in phytostabilisation or phytoexclusion were thought to be less risky and, consequently, benefited from a better theoretical acceptance than those issued from phytoextraction. Results were discussed according to national regulations. One issue related to the regulatory gap concerning the status of the plant biomass produced on contaminated land

SUMATECS - SUstainable MAnagement of Trace Element Contaminated Soils : a SNOWMAN-ERANET funded project

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