Chemical speciation of metals from marine sediments: Assessment of potential pollution risk while dredging, a case study in southern Sweden.

Contamination associated with metals is a critical concern related to their toxicity, persistence, and bio-accumulation. Trace elements are partitioned into several chemical forms, which some are more labile during fluctuations in the environment. Studying the distribution of metals between the different chemical fractions contributes to assess their bioavailability and to identify their potential risk of contamination to surrounding environments. This study concerns the speciation of metals (Pb, Cr, Ni, Zn and Fe) from sediments coming out from Malmfjärden bay, Sweden. The aim was to assess the potential risk of metal pollution during present and future dredging as well as while using dredged sediments in beneficial uses. The Tessier speciation procedure was chosen, and the results showed that low concentrations of metals were associated with the exchangeable fraction. In contrast, the major concentrations were linked to the residual part. The risk indexes (contamination factor and risk assessment code) showed that, during dredging activities, there is a low concern of pollution for Cr, Ni and Fe and a medium risk for Pb and Zn. Additionally, in all elements, the sum of non-residual concentrations was below the Swedish limits for using dredged sediments in sensitive lands. The findings suggested that the investigated metals in Malmfjärden sediments are related to low risks of spreading during using in beneficial uses.

Geophysical investigation of glass 'hotspots' in glass dumps as potential secondary raw material sources.

This study investigates the potential for Electrical Resistivity Tomography (ERT) to detect buried glass 'hotspots' in a glass waste dump based on results from an open glass dump investigated initially. This detection potential is vital for excavation and later use of buried materials as secondary resources. After ERT, test pits (TPs) were excavated around suspected glass hotspots and physico-chemical characterisation of the materials was done. Hotspots were successfully identified as regions of high resistivity (>8000 Ωm) and were thus confirmed by TPs which indicated mean glass composition of 87.2% among samples (up to 99% in some). However, high discrepancies in material resistivities increased the risk for introduction of artefacts, thus increasing the degree of uncertainty with depth, whereas similarities in resistivity between granite bedrock and crystal glass presented data misinterpretation risks. Nevertheless, suitable survey design, careful field procedures and caution exercised by basing data interpretations primarily on TP excavation observations generated good results particularly for near-surface materials, which is useful since glass waste dumps are inherently shallow. Thus, ERT could be a useful technique for obtaining more homogeneous excavated glass and other materials for use as secondary resources in metal extraction and other waste recycling techniques while eliminating complicated and often costly waste sorting needs.

Radiometrical and physico-chemical characterisation of contaminated glass waste from a glass dump in Sweden.

Around former glass factories in south eastern Sweden, there are dozens of dumps whose radioactivity and physico-chemical properties were not investigated previously. Thus, radiometric and physico-chemical characteristics of waste at Madesjö glass dump were studied to evaluate pre-recycling storage requirements and potential radiological and environmental risks. The material was sieved, hand-sorted, leached and scanned with X-Ray Fluorescence (XRF). External dose rates and activity concentrations of Naturally Occurring Radioactive Materials from 238U, 232Th series and 40K were also measured coupled with a radiological risk assessment. Results showed that the waste was 95% glass and dominated by fine fractions (<11.3 mm) at 43.6%. The fine fraction had pH 7.8, 2.6% moisture content, 123 mg kg-1 Total Dissolved Solids, 37.2 mg kg-1 Dissolved Organic Carbon and 10.5 mg kg-1 fluorides. Compared with Swedish EPA guidelines, the elements As, Cd, Pb and Zn were in hazardous concentrations while Pb leached more than the limits for inert and non-hazardous wastes. With 40K activity concentration up to 3000 Bq kg-1, enhanced external dose rates of 40K were established (0.20 µSv h-1) although no radiological risk was found since both External Hazard Index (Hex) and Gamma Index (Iγ) were <1. The glass dump needs remediation and storage of the waste materials under a safe hazardous waste class 'Bank Account' storage cell as a secondary resource for potential future recycling.

Physicochemical and toxicological characterization of hazardous wastes from an old glasswork dump at southeastern part of Sweden.

More than 34 old glasswork sites in the southeastern part of Sweden pose a permanent threat to human and environmental health due to the presence of toxic trace elements in open dumps with glass waste. The possibility of leaching of trace elements from different fractions of the disposed waste needed to be assessed. In the present investigation, leachate from a mixture of soil and waste glass of particle sizes of less than 2 mm (given the name fine fraction) was characterized by analyzing the pH (7.3), total organic content (TOC < 2%), organic matter content (4.4%), moisture content (9.7%), chemical oxygen demand (COD, 163 mg/kg) and trace elements content, being the values in accordance to the Swedish guidelines for landfilling of inert materials. However, very high trace elements content was found in the fine fraction as well as in all colors of waste glass, whose values were compatible to hazardous waste landfill class. Tests with Lepidium sativum growing in the fine fraction as substrate revealed chronic toxicity expressed as inhibition of root biomass growth in 11 out of 15 samples. Additionally, leachate from fine fractions posed acute toxicity to genetically modified E. coli (Toxi-Chromotest). This study highlights the importance of combining physicochemical characterization with toxicity tests for both solid waste and leachate obtained from different waste fractions for proper hazardousness assessment supporting decision making on remediation demands.

Chemical extraction of trace elements from hazardous fine fraction at an old glasswork dump.

Old glassworks sites have been always associated with contamination by different trace elements like Pb, Cd, As, Zn and others. The mixture of soil and waste glass of particle sizes <2 mm at one of the oldest Swedish glassworks (the Pukeberg) was studied by analyzing the trace elements content, organic content (3.6%) and pH (7.4). The results showed hazardous concentrations of Pb (1525 mg/kg), Ba (1312 mg/kg), Sb (128 mg/kg), Cd (36 mg/kg), As (118 mg/kg), Zn (1154 mg/kg) and Co (263 mg/kg) exceeded the Swedish guidelines of contaminated soil. Batch chemical extraction by the chelating agents EDTA, DTPA and the biodegradable NTA were performed to study the effect of chelating agent concentration and mixing time on the extraction efficiencies by following a Box-Wilson design of experiments. The results displayed good extraction efficiencies (less than 41%) of Pb, Cd, As and Zn by the EDTA, DTPA and NTA, which seemed depends on the type of chelator. In addition, high correlation between the extraction efficiencies, the chelators concentration and mixing time was found based on the statistical and experimental results.

Pilot scale aided-phytoremediation of a co-contaminated soil.

A pilot scale experiment was conducted to investigate the aided-phytoextraction of metals and the aided-phytodegradation of petroleum hydrocarbons (PHC) in a co-contaminated soil. First, this soil was amended with compost (10% w/w) and assembled into piles (Unp-10%C). Then, a phyto-cap of Medicago sativa L. either in monoculture (MS-10%C) or co-cropped with Helianthus annuus L. as companion planting (MSHA-10%C) was sown on the topsoil. Physico-chemical parameters and contaminants in the soil and its leachates were measured at the beginning and the end of the first growth season (after five months). In parallel, residual soil ecotoxicity was assessed using the plant species Lepidium sativum L. and the earthworm Eisenia fetida Savigny, 1826, while the leachate ecotoxicity was assessed using Lemna minor L. After 5months, PH C10-C40, PAH-L, PAH-M PAH-H, Pb and Cu concentrations in the MS-10%C soil were significantly reduced as compared to the Unp-10%C soil. Metal uptake by alfalfa was low but their translocation to shoots was high for Mn, Cr, Co and Zn (transfer factor (TF) >1), except for Cu and Pb. Alfalfa in monoculture reduced electrical conductivity, total organic C and Cu concentration in the leachate while pH and dissolved oxygen increased. Alfalfa co-planting with sunflower did not affect the extraction of inorganic contaminants from the soil, the PAH (M and H) degradation and was less efficient for PH C10-C40 and PAH-L as compared to alfalfa monoculture. The co-planting reduced shoot and root Pb concentrations. The residual soil ecotoxicity after 5months showed a positive effect of co-planting on L. sativum shoot dry weight (DW) yield. However, high contaminant concentrations in soil and leachate still inhibited the L. sativum root DW yield, earthworm development, and L. minor growth rate.

Reduction-melting extraction of trace elements from hazardous waste glass from an old glasswork's dump in the southeastern part of Sweden.

At the southeastern part of Sweden, old art and crystal waste glass has been identified as a hazardous waste due to high weight concentrations of Pb (32.398%), Cd (0.085%), and As (1.976%). The reduction-melting technique was used to investigate the extraction of these trace elements from powder waste glass of particle size < 1 mm. Following a factorial design technique, the experimental results of the reduction-melting method showed that 99.9% of Pb, 100% of Cd, and 99% of As could be extracted. For a batch of 10 g powder waste glass, the found experimental and theoretical optimum operating conditions were 1100 °C of melting temperature, 5 g of Na2CO3, 2 g of carbon, and 120 min of melting time. The reduction-melting method displayed promising results which might help in recycling the extracted trace elements and glass compared to the current used solution of landfilling as hazardous wastes.

Characterisation of excavated fine fraction and waste composition from a Swedish landfill.

The present research studies the characterisation and the physico-chemical properties of an excavated fine fraction (<10 mm) from a Swedish landfill, the Högbytorp. The results showed that the fine fraction represents 38% by mass of the total excavated wastes and it contains mainly soil-type materials and minerals. Higher concentrations of zinc, copper, barium and chromium were found with concentrations higher than the Swedish Environmental Protection Agency (EPA) for contaminated soil. The found moisture and organic contents of the fine fraction were 23.5% and 16.6%, respectively. The analysed calorific value (1.7 MJ kg-1), the potential of CH4 (4.74 m3 t-1 dry matter) and Total Organic Carbon (TOC) (5.6%) were low and offer low potential of energy. Sieving the fine fraction further showed that 80% was smaller than 2 mm. The fine represents a major fraction at any landfill (40%-70%), therefore, characterising the properties of this fraction is essential to find the potential of reusing/recycling or safely redisposing.

Effect of Medicago sativa L. and compost on organic and inorganic pollutant removal from a mixed contaminated soil and risk assessment using ecotoxicological tests.

Several Gentle Remediation Options (GRO), e.g., plant-based options (phytoremediation), singly and combined with soil amendments, can be simultaneously efficient for degrading organic pollutants and either stabilizing or extracting trace elements (TEs). Here, a 5-month greenhouse trial was performed to test the efficiency of Medicago sativa L., singly and combined with a compost addition (30% w/w), to treat soils contaminated by petroleum hydrocarbons (PHC), Co and Pb collected at an auto scrap yard. After 5 months, total soil Pb significantly decreased in the compost-amended soil planted with M. sativa, but not total soil Co. Compost incorporation into the soil promoted PHC degradation, M. sativa growth and survival, and shoot Pb concentrations [3.8 mg kg(-1) dry weight (DW)]. Residual risk assessment after the phytoremediation trial showed a positive effect of compost amendment on plant growth and earthworm development. The O2 uptake by soil microorganisms was lower in the compost-amended soil, suggesting a decrease in microbial activity. This study underlined the benefits of the phytoremediation option based on M. sativa cultivation and compost amendment for remediating PHC- and Pb-contaminated soils.

Particle size characterization of oak wood leachate: chemical oxygen demand and toxicity distribution within different fractions.

Oak wood leachate obtained from two storage facilities (storage pound and ditch) in a wood-based industry, and leachate generated by a laboratory leaching test, were characterized in seven categories regarding particle size distribution (PSD) (raw leachate, ≤ 20 µm, ≤ 10 µm, ≤ 1.2 µm, ≤ 13 nm, ≤ 5 nm and ≤ 2 nm). The PSD followed a normal distribution model with a correlation coefficient (r) varying from 82 to 88. Each fraction was analysed regarding chemical oxygen demand, polyphenols and acute toxicity in toxicity assays with Artemia salina, Vibrio fischeri and Lactuca sativa. Fractions with particles >1.2 µm were more toxic to A. salina and V. fisheri than fractions with particles ≤ 1.2 µm. No toxic effect was observed for L. sativa. The results suggest that polyphenols are the main toxic compounds in oak wood leachate. A conspicuous difference was found between field and laboratory samples.