Remediated marine sediment as growing medium for lettuce production: assessment of agronomic performance and food safety in a pilot experiment.

BACKGROUND: The use of reclaimed dredged sediments as growing media may offer a profitable alternative to their disposal as a waste and at the same time meets the need of peat-substitute substrates in horticulture. When sediments are reused to cultivate food crops, issues related to human health rise due to potential accumulation of contaminants in the product. This pilot study aimed at verifying the suitability of a reclaimed dredged port sediment, used pure or mixed with peat, as a growing medium for lettuce cultivation. RESULTS: The pure sediment caused a reduction in crop yield, probably due to its unsuitable physical properties, whereas the mixture sediment-peat and pure peat resulted in the same yield. Although the sediment contained potentially phytotoxic heavy metals and some organic pollutants, no symptoms of plant toxicity were noted. Besides, no organic contaminants were detected in lettuce heads, and heavy metals amounts were not hazardous for consumers. Conversely, plants grown in the sediment were particularly rich in minerals like Ca, Mg and Fe, and showed higher concentrations of organic acids and antioxidants. CONCLUSION: The use of the sediment as a growing medium for lettuce was shown to be safe for both inorganic and organic contaminants. Nevertheless, considering crop yield results, the mixture of the sediment with other materials is recommended in order to produce a substrate with more suitable physicochemical properties for vegetable cultivation. © 2019 Society of Chemical Industry.

Assessment of a particle size fractionation as a technology for reducing heavy metal, salinity and impurities from compost produced by municipal solid waste.

A physical fractionation of a compost obtained by municipal solid wastes (MSW) was conducted by dry-sieving process, to quantify coarse impurities and assess the distribution of nutrients, heavy metals and salinity values in particle size fractions of 2, 1.2-2, 0.8-1.2, 0.4-0.8, 0.2-0.4, 0.1-0.2 and <0.1mm diameter. The whole unfractionated compost and all physical fractions were analyzed for the same chemical parameters. The results showed that the studied compost was of a low grade due to high salinity and heavy metal concentrations, and the presence of coarse impurities, mainly glass. The physical fractionation analysis showed that heavy metal and base cations concentrations, and salinity values significantly increased with decreasing of particle size, whereas macro nutrients such as C, N and P were more evenly distributed among the different particle size fractions. Overall, our results showed that the removal of selected particle size fractions <0.8mm and coarse impurities (e.g. glass impurity >2mm) could significantly improve the compost quality without reduce its fertilization potential. We concluded that particle size fractionation is a feasible and sustainable approach to improve composted MSW materials for their safe recycle in agriculture.

Selecting chemical and ecotoxicological test batteries for risk assessment of trace element-contaminated soils (phyto)managed by gentle remediation options (GRO).

During the past decades a number of field trials with gentle remediation options (GRO) have been established on trace element (TE) contaminated sites throughout Europe. Each research group selects different methods to assess the remediation success making it difficult to compare efficacy between various sites and treatments. This study aimed at selecting a minimum risk assessment battery combining chemical and ecotoxicological assays for assessing and comparing the effectiveness of GRO implemented in seven European case studies. Two test batteries were pre-selected; a chemical one for quantifying TE exposure in untreated soils and GRO-managed soils and a biological one for characterizing soil functionality and ecotoxicity. Soil samples from field studies representing one of the main GROs (phytoextraction in Belgium, Sweden, Germany and Switzerland, aided phytoextraction in France, and aided phytostabilization or in situ stabilization/phytoexclusion in Poland, France and Austria) were collected and assessed using the selected test batteries. The best correlations were obtained between NH4NO3-extractable, followed by NaNO3-extractable TE and the ecotoxicological responses. Biometrical parameters and biomarkers of dwarf beans were the most responsive indicators for the soil treatments and changes in soil TE exposures. Plant growth was inhibited at the higher extractable TE concentrations, while plant stress enzyme activities increased with the higher TE extractability. Based on these results, a minimum risk assessment battery to compare/biomonitor the sites phytomanaged by GROs might consist of the NH4NO3 extraction and the bean Plantox test including the stress enzyme activities.

Assessment of zerovalent iron for stabilization of chromium, copper, and arsenic in soil.

Stabilization of soil contaminated with trace elements is a remediation practice that does not reduce the total content of contaminants, but lowers the amounts of mobile and bioavailable fractions. This study evaluated the efficiency of Fe(0) to reduce the mobility and bioavailability of Cr, Cu, As and Zn in a chromated copper arsenate (CCA)-contaminated soil using chemical, biochemical and biotoxicity tests. Contaminated soil was stabilized with 1% iron grit. This treatment decreased As and Cr concentrations in leachates (by 98% and 45%, respectively), in soil pore water (by 99% and 94%, respectively) and in plant shoots (by 84% and 95%, respectively). The stabilization technique also restored most of analyzed soil enzyme activities and reduced microbial toxicity, as evaluated by the BioTox test. After stabilization, exchangeable and bioaccessible fractions of Cu remained high, causing some residual toxicity in the treated soil.