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Concentrations of the investigated heavy metals in the representative samples of vegetable growing media differed significantly – the highest concentrations were in the root zone of pumpkin, and the lowest – in the root zone of tomato. Only cadmium exhibited higher concentrations in the root zone of pumpkin and zucchini exceeding maximum permissible limits according to LAND 20-2001. Concentrations of all other metals in the root zone of the investigated vegetables were below limit values valid for the 1st category sewage sludge. Mean concentrations of nitrogen, phosphorus and potassium in the root zone was quite different for the three selected plant species, but comparably high bioavailable concentrations of the primary plant nutrients showed potential for this sludge to be used in agriculture or forestry. Concentrations of Cr, Ni and Pb in the sewage sludge were far below the critical range, while Cd, Zn and Cu concentrations were within the range or even above critical soil concentration values suggested in the reviewed literature. While average heavy metal concentrations in different parts of the investigated vegetables (pumpkin, zucchini and tomato) were much lower than the suggested critical ones, and was within the range (Cu, Zn, Cr and Ni) or even lower (Cd and Pb) than normal HM level in plants. Concentration of all of the investigated heavy metals was significantly lower in vegetable fruits than in the roots and no metal accumulation in the vegetable biomass (roots as well as aboveground parts) was observed – all accumulation coefficients were below unity. [ABSTRACT FROM AUTHOR]

Sewage sludge is a rest product deriving from the wastewater treatment plants. It is rich in nutrients and essential elements. Therefore sludge on-land utilisation can create an added value by recovering energy from biomass produced on marginal lands. However, widespread on-land recycling of sewage sludge might be limited due to high heavy metal content. Health organisations show an increasing concern about the risks posed to the environment and human health as many countries worldwide already are facing the heavy metal contamination problem. In the scientific literature it can be found, that high total heavy metal content is not directly related to an intensive metal uptake by plants. In this study samples were collected from three woody plant species (black locust, silver birch and aspen) growing directly on the sewage sludge in a storage site near Kaunas, Lithuania. Heavy metal content was detected separately in the leaves, stems and roots. It was determined that nearly all analysed heavy metals (lead, chromium, nickel, copper and zinc) were accumulated within normal range despite high total concentrations in the growing media, and only cadmium was accumulated at elevated concentration. Based on bioaccumulation factor, aspen could be considered as a Cd-accumulator and used for phytoremediation purposes. [ABSTRACT FROM AUTHOR]

Alkaline soil additives used in this study, as cement kiln dust and lime mud, resulted in significant rise of the pH in contaminated soil and sludge mixtures, while buffering capacity of the sludge appeared to be much stronger than that of the soil. Total concentrations of the investigated trace elements in the tested samples in most cases were above limit values given in Lithuanian environmental normative documents HN 60:2015 and LAND 20:2005; Cd, Zn and Pb concentrations exceeding MPCs by 2-10 times. Nickel, cadmium and copper in the sludge appeared to be the most mobile elements, their EDTA-extractable fraction reaching 30-50% from the total. The tested industrial by-products in most cases significantly reduced trace element mobility. Immobilizing effect in the contaminated soil was from low to moderate, while impact on the reduction of Cd, Pb, Zn, Cr, Ni, As, Se, Hg mobility in the sludge was much stronger. Alkaline treatment was not so effective to reduce mobility of Cu and As in the soil, but immobilising effect of lime mud on these elements in the sludge was significant. A multivariate data analysis model with two principle components explained 94% of the data variation. The most distinctive factor, separating samples, was the origin of the two tested metal-rich substrates: contaminated soil and sewage sludge. Contaminated soil could be distinguished by high concentrations of As, Tl, Hg and Pb. Both alkaline treatments on sewage sludge were more effective, thus scores are further from the origin, although, difference between kiln dust and lime mud immobilising effectiveness was not so significant. Application of alkaline amendments: cement kiln dust and lime mud, proved to have strong immobilizing effect on the most of the investigated trace elements, and usage of local by-products for contaminated soil (sludge) remediation purposes could be seen as an environmentally friendly, cost-effective and safe disposal alternative. [ABSTRACT FROM AUTHOR]

EU countries agreed upon increasing the use of renewable energy, which strongly stimulates usage of biofuels. Biomass ash is generated as a residue product in large volumes as a result of biomass combustion. Heavy metal content in the ashes is the main hinder for further ash utilization in agriculture, forestry and construction sector. Aim of this study was to assess potential of biomass ash to be used as pavement base, also to evaluate risks associated with heavy metals contained in ash as well as their leaching possibility. Ash elemental analysis showed that biomass was burned efficiently, and organic carbon content in ash samples was below 2%. The limiting trace element was cadmium, which concentration in ash exceeded maximum permissible value, restricting ash recycling in forestry or agriculture. Leaching test showed that there is no threat to the environment when such waste material is used in road construction as base layer. All leaching values were below permissible concentrations or even below ICP detection limits. Compaction tests of layers made from gravel/ash mixtures revealed that biomass ash could be successfully used in road construction industry. Results showed that the strongest mixed layer was from 80% gravel and 20% ash. The compaction of this mixture was the highest, only the second best result showed pure 100% gravel, while the least compacted was 50% ash and 50% gravel mixture. [ABSTRACT FROM AUTHOR]

There are about 3,000-4,000 heavy metal contaminated sites across Lithuania. According to Lithuanian legal framework, the only way to manage this pollution is ex-situ cleaning which requires excavation, transporting, storage place and later monitoring. This indicates the urgent need of innovative technologies that would be not only cost-effective but also environmentally friendly and have a public acceptance. Such technologies are natural and chemically enhanced phytoextractions. Both technologies incorporate plants that can accumulate excessive amounts of heavy metals. During continuous phytoextraction plants accumulate heavy metals throughout all vegetation period and are harvested together with heavy metals when desired biomass is gained. At chemically assisted phytoextraction metal binding chelates are added to increase heavy metal uptake by plants. Since phytoextraction is considered as promising green technology, many efforts are laid to find the most suitable hyperaccumulator plants as well as ecologically safe chelating agents. This paper intends to overview latest researches done at phytoextraction field and look over this kind of remediation possibilities in Lithuania. [ABSTRACT FROM AUTHOR]