Concentrations Of Hazardous Elements Research Articles

Assessing pollution degree and human health risks from hazardous element distribution in soils near gold mines in a Colombian Andean region: Correlation with phytotoxicity biomarkers

The assessment of human health risk due to the presence of hazardous elements in the environment is now necessary for environmental management and legislative initiatives. This study aims to determine the contamination by As, Cd, Pb, and Cr in soils near gold mines in three municipalities located in the Andean region of Colombia. One of the main objectives of the study is to explore possible correlations between the Lifetime Cancer Risk (LCR) and phytotoxicity biomarkers using a simple and rapid-response plant model, radish (Raphanus sativus L.). In the municipality of Yalí, Puerto Berrío, and Buriticá, the hazardous elements concentrations ranged from 8.1 to 35.5, 1.7 to 892, and 5.8 to 49.8 for As, 0.1 to 4.6, 0.1 to 65.2, and 0.5 to 18.2 for Cd, 18.5 to 201.3, 13.0 to 1908, and 189 to 2345 for Pb, and 5.4 to 118.4, 65.4 to 301, and 5.4 to 102.3 for Cr, respectively. The results showed that the biomarkers intracellular H2O2 concentration, antioxidant activity, and radicle elongation exhibited significant (P < 0.05) variations associated with the concentration of hazardous elements in the soils. Significant correlations (P < 0.05, r > 0.58) were found between the biomarkers and the LCR for Cd, Pb, and Cr, but not for As. The results using biomarkers reveal that soil pH and organic matter content are important variables that control the bioavailability of these elements in the soil. The use of indicators like LCR alone has limitations and should be accompanied by the use of biomarkers that allow for a better understanding of the biological system's response to exposure to potentially toxic elements. The results obtained show the urgent need to implement public policies to minimize exposure to hazardous substances in areas near gold mining projects.

Evaluation of single particle morphological characteristics and human health risks in different functional areas

Purpose This study aims to better understand the morphological characteristics of single particle and the health risk characteristics of heavy metals in PM2.5 in different functional areas of Handan City. Design/methodology/approach High resolution transmission electron microscopy was used to observe the aerosol samples collected from different functional areas of Handan City. The morphology and size distribution of the particles collected on hazy and clear days were compared. The health risk evaluation model was applied to evaluate the hazardous effects of particles on human health in different functional areas on hazy days. Findings The results show that the particulate matter in different functional areas is dominated by spherical particles in different weather conditions. In particular, the proportion of spherical particles exceeds 70% on the haze day, and the percentage of soot aggregates increases significantly on the clear day. The percentage of each type of particle in the teaching and living areas varied less under different weather conditions. Except for the industrial area, the size distribution of each type of particle in haze samples is larger than that on the clear day. Spherical particles contribute more to the small particle size segment. Soot aggregate and other shaped particles contribute more to the large size segment. The mass concentrations of hazardous elements (HEs) in PM2.5 in different functional areas on consecutive haze pollution days were illustrated as industrial area &gt; traffic area &gt; living area &gt; teaching area. Compared with the other functional areas, the teaching area had the lowest noncarcinogenic risk of HEs. The lifetime carcinogenic risk values of Cr and As elements in each functional area have exceeded residents’ threshold levels and are at high risk of carcinogenicity. Among the four functional areas, the industrial area has the highest carcinogenic and noncarcinogenic risks. But the effects of HEs on human health in the other functional areas should also be taken seriously and continuously controlled. Originality/value The significance of the study is to further understand the morphological characteristics of single particles and the health risks of heavy metals in different functional areas of Handan City. the authors hope to provide a reference for other coal-burning industrial cities to develop plans to improve air quality and human respiratory health.

A review of heavy metal risks around e-waste sites and comparable municipal dumpsites in major African cities: Recommendations and future perspectives

In Africa, the effects of informal e-waste recycling on the environment are escalating. It is regularly transported from developed to developing nations, where it is disassembled informally in search of precious metals, thus increasing human exposure to harmful compounds. Africa has a serious problem with e-waste, as there are significant facilities in Ghana and Nigeria where imported e-waste is unsafely dismantled. however, because they are in high demand and less expensive than new ones, old electronic and electrical items are imported in large quantities, just like in many developing nations. After that, these objects are frequently scavenged to recover important metals through heating, burning, incubation in acids, and other techniques. Serious health hazards are associated with these activities for workers and individuals close to recycling plants. At e-waste sites in Africa, there have been documented instances of elevated concentrations of hazardous elements, persistent organic pollutants, and heavy metals in dust, soils, and vegetation, including plants consumed as food. Individuals who handle and dispose of e-waste are exposed to highly hazardous chemical substances. This paper examines heavy metal risks around e-waste sites and comparable municipal dumpsites in major African cities. Elevated concentrations of these heavy metals metal in downstream aquatic and marine habitats have resulted in additional environmental impacts. These effects have been associated with unfavourable outcomes in marine ecosystems, such as reduced fish stocks characterized by smaller sizes, increased susceptibility to illness, and decreased population densities. The evidence from the examined studies shows how much e-waste affects human health and the environment in Africa. Sub-Saharan African nations require a regulatory framework that includes specialized laws, facilities, and procedures for the safe recycling and disposal of e-waste.

Screening and evaluation of bamboo shoots: Comparing the content of trace elements from 100 species

Hundreds of bamboo shoots have been reported to be edible, but the accumulation of trace elements and hazardous elements in bamboo shoots is poorly understood. Here, 100 bamboo species have been evaluated by screening elements including B, Fe, Mn, Cu, Zn, Cd, Pb and As in bamboo shoots using different assessment systems. Bamboo shoots displayed different morphological characteristics, and large differences were found in the concentration of elements. Most bamboo shoots were rich in Fe and Zn and low concentrations of hazardous elements, but the concentration of Cd and Pb exceeded the maximum permissible limits of tuber vegetables in some bamboo species. Different bamboo shoots were ranked differently in the four assessment systems, and the comprehensive evaluation assigned final scores to all 100 bamboo shoots. This study provides valuable recommendations for selecting high-quality bamboo shoots that are rich in trace elements nutrition while minimizing the potential for hazardous element accumulation.

Characterization and optimization of eco-friendly cementitious materials based on titanium gypsum, fly ash, and calcium carbide residue

• Cementitious materials was prepared by FA, TG, CCR based on RSM under ambient curing. • The influences of FA, TG, CCR or their interaction on different ages was analyzed. • The transformation behavior of Fe 3+ in FTC system was observed. • The hydration mechanism, environmental performance of FTC materials was investigated. Titanium gypsum (TG), fly ash (FA) and calcium carbide residue (CCR) are harmful industrial by-products that need to be addressed. In this study, TG, FA and CCR were selected to prepare the eco-friendly FA-TG-CCR (FTC) cementitious materials. Respond surface methodology (RSM) was undertaken to optimize and understand the influence of design factors of m(TG/FA), m(CCR/FA) and W/B on compressive strength, and the mechanical properties, microstructure, hydration mechanism and environmental performance of FTC cementitious materials were investigated. The morphology and structure were characterized by X-ray diffraction (XRD), thermogravimetry- differential scanning calorimetry (TG-DSC) and Scanning electron microscopy energy dispersive X-ray (SEM-EDX), the concentration of hazardous elements was determined via inductively coupled plasma optical emission spectrometer (ICP-OES). The results show that the optimal mixture with RSM methodology (m(TG/FA) = 30.80 %, m(CCR/FA) = 27.85 %, W/B = 0.62) reached 18.93 MPa at 28 days of curing, which confirmed via experimental verification. The FTC cementitious materials are mainly consist with C-(A)-S-H, ettringite; the existence of Fe 3+ was disadvantageous to early age strength, however partial Fe 3+ participated in the formation of Fe-ettringite as the curing time increased, which is beneficial to later age strength. The leaching results indicate that the FTC materials can effectively consolidate the heavy metal ions in raw materials, and the leaching concentration of ions all meet the Chinese Standard for Pollution Control on the Landfill Site of Municipal Solid Waste. Therefore, the synergistic of FTC material offers a novel approach to the efficient utilization of original TG and other industrial by-product wastes.

Cancer Incidence in Volcanic Areas: A Systematic Review

Background:There are more than 1,000 active volcanoes worldwide with inhabitants within 100 km of them. Volcanoes spill several toxic metals and spew pollution through gasses, causing soil and water contamination. The dangerously active volcanoes place the nearby population at risk for volcanic hazards. This review aimed to determine whether people living in these volcanic areas have higher risk of cancer and more attention should be given to this danger. Methods:A systematic literature search was conducted of PUBMED, Science Direct, SCOPUS, Proquest, and Google Scholar, and from citation searching. We assessed the quality of the studies and extracted the incidence rate of cancer in the volcanic areas compared to non-volcanic areas. Results: The search identified 360 articles, with 11 studies meeting our selection criteria. The results reported the incidence of cancer in children was predominantly in volcanic areas with girls suffering as much as 1.4 per 100,000 per year. The highest cancer age standardized incidence rates for females, males, and overall calculation in volcanic areas were reported as 31.7/100,000/year in Catania, 10.34/100,000/year in Furnas, and 38.3/100,000/year in Catania-Messina-Enna for thyroid cancer. We observed the increasing incidence of carcinoma for some types of cancer in volcanic areas. Conclusion:Cancer incidence in volcanic areas was higher than non-volcanic areas and it is caused by multifactorial conditions. The concentrations of hazardous elements of volcanic products vary among volcanoes and are related to the harmful risk for the inhabitants. The negative effects of volcanic products to human health should be given more consideration.

Definition of the hydrogeochemical background of the Novosibirsk urban agglomeration natural waters

Based on the results of field and chemical-analytical work in 2018-2021 for the first time, the characteristics of the hydrogeochemical background for the natural waters of the Novosibirsk urban agglomeration were substantiated. It has been established that the background concentrations of chemical elements in surface and ground waters decrease in the order from Si to In. Hydrogeochemical anomalies were established in the distribution of As, U, Ti, Li, Al, Si, Mn, Fe, Br, I, Sb, which served as the basis for compiling a map of the degree of pollution of the natural waters of the city of Novosibirsk. Among the surface waters, the most polluted are the waters of the rivers: Inya (near the village of Novolugovoe), 2nd Eltsovka (near the Chemical Concentrates Plant), Plyushchikha (near Vilyuiskaya Street), Eltsovka (in Nizhnyaya Eltsovka), Kamyshenka (in Inyushensky Bor), as well as rivers Ob (in the Zaeltsovsky forest). It should be noted that the concentrations of hazardous elements in the Kamyshenka, Plyushchikha and 2 Eltsovka rivers decrease towards their mouths. The least polluted with toxic elements were the waters of the Tula and Kamenka rivers, the studied lakes and backwaters, the Gorsky and Tulinsky flooded quarries, as well as the samples taken in the standpipe near the Bugrinsky bridge.

Use of combined tools for effectiveness evaluation of tailings rehabilitated with designed Technosol.

Soil and water characteristics and biogeochemical processes can be improved by the application of an integrated technology based on circular economy: designed Technosol. The evaluation of the effectiveness of the superficial application of a designed Technosol, with andic and eutrophic properties, on the rehabilitation of sulfide tailings of a uranium mine (Fé mining area, Spain) was the aim of this study. After 20months of the Technosol application, the tailing rehabilitation status (Rehabilitated tailing) was compared to a non-rehabilitated tailing (Tailing). To assess the rehabilitation of these systems, several properties were analyzed: chemical characteristics of the materials and their leachates, soil enzymatic activities (dehydrogenase, β-glucosidase, acid phosphatase and urease), basal respiration and several plant endpoints from direct and indirect bioassays and pot experiment using Lolium perennse L. and Trifolium pratense L.. Potentially toxic concentrations of Co, Mn and Ni were identified in both available fraction and leachates, pointing out the serious environmental risk posed by the tailing. The improvement of overall physicochemical properties in the rehabilitated tailing materials (e.g., decrease of thehazardous element concentrations in leachates and available fraction, and improvement of thefertility and structure) allowed a quick plant cover with pasture species and provided a suitable habitat for active microbial community (evaluated by increasing dehydrogenase activity and basal respiration). This improvement in the rehabilitated tailing contributed to a significant decrease in the ecotoxicological risk and the spread of hazardous elements. The field application of this specific Technosol was a promising and lasting solution for rehabilitation of this type of tailings.

Effects of membrane filter material and pore size on turbidity and hazardous element concentrations in soil batch leaching tests

Soil batch leaching tests are conducted worldwide to quantify the leaching of hazardous substances from contaminated soil. In the extracts of soil batch leaching tests, some inorganic substances such as arsenic and lead are released both in colloidal and dissolved form. Recent studies have found that soil colloidal particles with small diameters persist in the filtrate even after the extracts are filtered through a membrane filter (MF) with a pore size of 0.45 μm, and they might affect the concentration of arsenic or lead. This study evaluated the effects of 0.45- or 0.4-μm MF materials on filtrate turbidity and leaching concentrations of inorganic hazardous elements during batch leaching tests. Turbidity and arsenic and lead concentrations in the filtrates of the tested soil samples varied greatly depending on the MF material. These findings indicate that the MF material affects the removal rate of colloidal arsenic or lead and therefore affects the results of leaching tests.

A critical assessment on resource recovery from electronic waste: Impact of mechanical pre-treatment

Commonly used pre-treatments during e-waste recycling, e.g., manual dismantling, removal of components, size reduction, crushing etc. can cause significant local area contamination and environmental pollution. This study seeks to critically assess the impact of mechanical pre-treatments on average resource recovery, generation of high-value material concentrates and on concentrations of hazardous elements. Two sets of initial processing were carried out on a variety of waste printed circuit boards (PCBs). Electronic components were not removed from these boards. In Set I, PCBs were powdered using sorting, crushing, hammering followed by separation into heavy and light fractions through froth floatation. In Set II, PCBs were cut into small sized pieces. These were heat treated in a horizontal furnace in inert atmosphere at 850 °C for 15 min, followed by in-depth characterization of pyrolysis residues. The average recovery of main metal copper was quite comparable for both sets (Set I: 27.6 wt %; Set II: 26.3 wt %). In case of precious metals, there were higher recoveries for Au and Ti in Set I, whereas Ag, Pd, Pt showed better recoveries in Set II. A mixed trend was observed for minor metals Mn, Zn Sn, Sb and Si. In Set I, most elements showed a mixed presence in the heavy and light fractions after pyrolysis. On the other hand, Set II showed a significantly higher elemental segregation and generation of high value concentrates. Potential toxic hazardous elements (Pb, Cr, Co, Cd, Be) were detected in much higher amounts in Set I as compared to Set II. Waste processing under Set II was found to be more efficient, cost-effective and eco-friendly as compared to Set I. This study suggests a fresh look at traditional labour-intensive e-waste recycling practices towards limiting social and environmental impacts while enhancing the efficiency and cost-effectiveness of resource generation from e-waste.

Leaching of hazardous elements from Mozambican coal and coal ash

Large-scale coal mining is being carried out in Tete province, Mozambique. This area is also being planned to become a large coal fired power production hub serving electricity to neighboring countries in southern Africa. Thus, huge amounts of coal will be burned, resulting in the generation of a large quantity of coal ash. High concentrations of hazardous elements are often released from coal and coal ash causing negative impacts to human health and the environment. Therefore, it is important to understand the possibility of hazardous elements leaching. Aqueous batch leaching experiments under ambient conditions were conducted using six coal samples and their ash. Most of the coal leached very low concentrations of hazardous elements. However, an absence of carbonate minerals gave rise to higher acidity levels. This resulted in elevated leaching concentrations of manganese and iron, regardless of their contents. Burning coal resulted in higher contents of hazardous elements in the ash. However, leaching concentrations of most of the elements from the ash samples were still lower than the environmental standards. Chromium and manganese were enriched in slightly acidic leachates regardless of their contents while higher arsenic than the permitted level was leached from the ash containing the highest arsenic content that generated neutral pH leachate. These findings highlight a possibility of hazardous elements contamination from Mozambican coal and coal ash. Therefore, the storage of coal and disposal of coal wastes and ash in Tete Province should be done carefully and monitored to avoid the contamination in the region.

Distinction of strontium isotope ratios between water-soluble and bulk coal fly ash from the United States

Coal ash is one of the largest industrial waste streams in the United States and contains elevated concentrations of hazardous elements that could pose environmental and human health risks. Due to the relatively high strontium concentrations in coal ash and the distinctive 87Sr/86Sr ratios, strontium isotopes have been utilized to trace coal ash contaminants in impacted water resources. While previous studies have characterized the Sr isotope ratios for the water-soluble Sr derived from coal ash, the strontium isotopic composition of the bulk coal ash has not been systematically evaluated. In the current study, we report the 87Sr/86Sr ratios of bulk and water-soluble Sr in fly ash derived from coals of the three major coal-producing basins in the U.S., the Appalachian Basin, Illinois Basin, and Powder River Basin. The data show a wide range of 87Sr/86Sr ratios in the bulk fly ash samples (0.710788–0.722311), with the most radiogenic 87Sr/86Sr ratios in fly ash originating from Illinois Basin coals (0.718029 ± 0.003365; n = 16), followed by those from Appalachian Basin coals (0.712641 ± 0.000860; n = 16), and those from Powder River Basin coals (0.711663 ± 0.000489; n = 7). The 87Sr/86Sr ratios in the water leachates are significantly lower than the 87Sr/86Sr ratios of the bulk fly ash for Illinois Basin and Appalachian Basin (0.711660 ± 0.001172 and 0.710694 ± 0.000317, respectively, p-value < 0.01), whereas there is no significant difference for the Powder River Basin fly ash (0.711666 ± 0.000456, p-value = 0.13). These isotopic differences most likely reflect the different mineralogical compositions of the studied fly ash and the differential solubility of carbonate phases with low 87Sr/86Sr ratios relative to more radiogenic silicate phases. Overall, the distinction between the strontium isotope ratios of bulk fly ash versus water-soluble fly ash is important, as it refines the application of strontium isotopes as a forensic tracer for tracking coal ash spills and contamination in the environment.

Elemental Composition and Organic Petrology of a Lower Carboniferous-Age Freshwater Oil Shale in Nova Scotia, Canada.

A 59 m-thick section of a freshwater oil shale interbedded with marlstone of Lower Carboniferous (Tournaisian) age from the Big Marsh area in Antigonish Basin, Nova Scotia, Canada, was examined using reflected light microscopy, Rock-Eval pyrolysis, X-ray diffractometry analysis, inductively coupled plasma-mass spectrometry for elemental analysis, and prompt γ for boron concentration. The oil shale was deposited in a lacustrine environment based on geology, sedimentology, variation in organic matter, and boron content (28–54 ppm). Organic petrology classified the oil shale into three broadly distinct types. Type A oil shale is a coastal facies shale containing terrestrially derived macerals, such as vitrinite and inertinite, sporinite, with some lamalginite, and amorphous bituminous matrix. Type B oil shale was deposited in a shallow-water facies and contains mostly lamalginite and some vitrinite and sporinite. Type C oil shale is a relatively deep-water facies, associated with open-water Torbanite-type oil shale and contains mostly Botryococcus colonial telalginite. The oil shale is thermally mature (Tmax is 441–443 °C). Total organic carbon (TOC) varies from 5.8 to 7.3 wt %, and the hydrogen index is between 507 and 557 mg HC/g TOC. The rate of sedimentation as determined by the Th/U ratio indicates possibility of three sedimentation periods: an irregular but mostly slow rate of sedimentation from the base of the section up to 68 m, followed by a regular and slow rate between 68 and 53 m, and a regular and fast rate between 53 m and the top of the section. The higher Th/U ratio during deposition of the shallow-water facies was due to the input of allochthonous U. The redox conditions, as reflected in the variation of Cr to Mo, U, and Ni + V, indicate that the oil shale was deposited under suboxic–dysoxic conditions. The high organic productivity by phytoplankton and bacteria is characterized by a low Cr and high V/Cr ratio and suboxic conditions. In contrast, the well-oxygenated and uniform, warm-temperature upper water level supports a dysoxic environment. Variation of Sr/Ca vs Mn/Ca ratios indicates that most samples have low values, a characteristic of colder water and high terrigenous influx. The post-Archean Australian shale (PAAS)-normalized rare earth elements (REEs) follow three trends. Type A oil shale has the highest concentration of total REEs (648 ppm) and light REEs (LREEs, 605 ppm) as compared with type C (269 and 233 ppm), which are less than half of type A. Type B oil shale has the lowest total REEs (184 ppm) and LREEs (152 ppm). The concentration of heavy REEs decreased from 43 ppm in type A oil shale to 36 ppm in type C oil shale. Comparison of PAAS-normalized REEs for the three oil shale types indicates a reduction of the negative Eu anomaly with depth, which is possibly related to sedimentary sorting as a result of accumulation of fine sediments in the deeper water zone of the lake. The concentration of most elements of environmental concern is similar to and/or lower than the world shale. However, there are instances of higher concentrations of hazardous elements (e.g., As, Cd, Mo, and Se).

The Use of High-Alloyed EAF Slag for the Neutralization of On-Site Produced Acidic Wastewater: The First Step Towards a Zero-Waste Stainless-Steel Production Process

Recycling of steelmaking slags has well-established applications, such as their use in cement, asphalt, or fertilizer industries. Although in some cases, such as the electric arc furnace (EAF) high-alloyed stainless-steel production, the slag’s high metal content prevents its use in such applications. This forces companies to accumulate it as waste. Using concepts such dematerialization, waste management, industrial symbiosis, and circular economy, the article drafts a conceptual framework on the best route to solving the landfilling issue, aiming at a zero-waste process re-design. An experimental part follows, with an investigation of the use of landfill slag as a substitute of limestone for the neutralization of acidic wastewater, produced by the rinsing of steel after the pickling process. Neutralization of acidic wastewater with both lime and slag samples was performed with two different methods. Two out of four slag samples tested proved their possible use, reaching desired pH values compared to lime neutralizations. Moreover, the clean waters resulting from the neutralizations with the use of both lime and slag were tested. In terms of hazardous element concentrations, neutralization with slag yielded similar results to lime. The results of these trials show that slag is a potential substitute of lime for the neutralization of acidic wastewater.

Assessment of water treatment residuals as sorbent material in permeable reactive barriers: Application to a copper‐contaminated site

AbstractThe objective of this study is to design a pilot‐scale permeable reactive barrier (PRB) for the removal of copper from groundwater in Keweenaw Peninsula, Michigan. The reactive material selected for the barrier is drinking water treatment residuals (WTR)—the residuals of alum coagulants used in a local drinking water treatment plant. Physical and chemical properties of the WTR were determined. Synthetic precipitation leaching procedure tests indicated the concentrations of hazardous elements leached from the residuals do not exceed U.S. Environmental Protection Agency limits and, hence, can be safely recycled as PRB material. Batch reactor tests showed that equilibrium sorption of copper is high and fits a Langmuir‐type isotherm. Site characterization studies included groundwater flow direction, pore water velocity, and contaminant concentration to determine optimal dimensions and placement of the PRB. Permeameter tests were performed with various mixtures of the WTR and an inert support material (pea gravel) to determine the ideal mix to match the hydraulic conductivity of the field site. Kinetic and column experiments were conducted to understand the significance of chemical and physical mass transfer limitations. Based on the results, dimensions of a PRB to meet the Michigan Department of Environmental Quality target level of 0.031 milligrams per liter (mg/L) total Cu were calculated.

Observational Study Unveils the Extensive Presence of Hazardous Elements in Beached Plastics from Lake Geneva

Over 3000 samples of plastic litter have been retrieved from twelve pebble beaches around the shores of Lake Geneva. The plastic stock consisted of identifiable objects of various size and colour, including bottles, bottle tops, cotton buds, pens, toys and straws, an heterogeneous assortment of fragments whose origin was either discernible or unknown, and pieces or blocks of expanded polymer (polystyrene or polyurethane foam). Analysis of 670 samples by portable x-ray fluorescence (XRF) spectrometry revealed high concentrations of hazardous elements or compounds among many plastics. These included Cd, Hg and Pb (with maximum concentrations of 6760, 810 and 23,500 ppm, respectively) as stabilisers in PVC-based materials and/or brightly-coloured sulphide or chromate pigments in primary and secondary plastics, and Br (with a maximum concentration of 27,400 ppm) as a proxy for brominated flame retardants in both plastics and foams. The abundance of hazardous elements in beached plastics that have been restricted or banned reflect the age and residence time of the plastic stock in the lake, coupled with a relatively high length of shoreline to surface area of the system. The migratability of hazardous elements from the polymeric matrix is likely to determine their environmental impacts and is recommended as a future area of research.

Soil stabilization by ground bottom ash and red mud

This paper presents results of a compressive investigation conducted on weathered soil stabilized with ground bottom ash (GBA) and red mud (RM). The effects of water/binder ratio, RM/GBA ratio, chemical activator (NaOH and Na2SiO3) and curing time on unconfined compressive strength of stabilized soils were examined. The results show that the water/binder ratio of 1.2 is optimum ratio at which the stabilized soils have the maximum compressive strength. For 28 days of curing, the compressive strength of soils stabilized with alkali-activated GBA and RM varies between 1.5 MPa and 4.1 MPa. The addition of GBA, RM and chemical activators enhanced strength development and the rate of strength improvement was more significant at the later age than at the early age. The potential environmental impacts of stabilized soils were also assessed. The chemical property changes of leachate from stabilized soils were analyzed in terms of pH and concentrations of hazardous elements. The observation revealed that the soil mixture with ground bottom ash and red mud proved environmentally safe.

Distributions of environmentally hazardous elements in the Tertiary oil shale deposits from NW Anatolia, Turkey: A statistical analysis

ABSTRACTThe environmentally hazardous element concentrations (As, Cd, Cr, Cu, Hg, Mn, Pb, S, and Zn) and element–organic matter relations of the oil shale deposits in six different fields in NW Anatolia, Turkey, were investigated and the characteristics of fields were compared. The enrichment factor (EF) for most of the trace elements in the studied oil shales generally show enrichment patterns for all the fields. Only Cr, Hg, and Pb for oil shale samples from the Bahçecik field samples and Hg for oil shale samples from the Gölpazarı field samples are depleted. Arsenic in the Bahçecik field samples and Hg in the Himmetoğlu field samples are neither depleted nor enriched. The lowest and highest element enrichments in these fields are determined to be Hg and S, respectively. In general, all elements have high concentrations in the Beypazarı and Seyitömer fields and low concentrations in the Himmetoğlu, Bahçecik, and Gölpazarı (except for As) fields. A positive correlation at significance level of p ≤ 0.05 was observed for total organic carbon content with Cd in four of the fields, with Cu and S in two fields and with Cr, Mn, and Zn in only one field.

Interaction of contaminated sediment from a salt marsh with estuarine water: evaluation by leaching and ecotoxicity assays and salts from leachate evaporation

Wastes from a former Portuguese steel plant were deposited between 1961 and 2001 on the riverbank of a tributary of the Tagus River creating a landfill connected to the river, posing a potential contamination risk to the Tagus estuary ecosystem. This study aims to assess the transfer of chemical elements from contaminated sediments to the estuarine water from cycles of sediment leaching so as to evaluate the ecotoxicity of the leachates, and to analyze the solid phases crystallized from those leachates. Landfill sediment and estuarine water samples were collected during low tide. Sediment samples were analyzed for pH, electric conductivity (EC), Corg, NPK, and iron oxides. Leaching assays (four replicates) were done using estuarine water (200 cm3/replicate) and 1.5 kg of sediment per reactor. Each reactor was submitted to four leaching processes (0, 28, 49, and 77 days). The sediment was kept moist between leaching processes. Sediment (total (acid digestion) and available fraction (diluted organic acid extraction-Rhizo)) elemental concentrations were determined by inductively coupled plasma–instrumental neutron activation analysis (ICP/INAA). Leachates, and estuarine and sediment pore waters were analyzed for metals/metalloids by ICP/mass spectrometry (MS) and carbonates/sulfate/chloride by standard methodologies. Ecotoxicity assays were performed in leachates and estuarine and pore waters using Artemia franciscana and Brachionus plicatillis. Aliquots of the leachates were evaporated to complete dryness (23–25 °C) and crystals analyzed by X-ray powder diffraction (XRD). Sediment with pH = 8 and high EC and Corg was contaminated with As, Cd, Cr, Cu, Pb, and Zn. The element concentrations in the available fraction of the sediment were low compared to the sediment total concentrations (<1 % for Rhizo extraction). The concentrations of potentially hazardous elements in the estuarine water were relatively low, except for Cd. Concentrations of hazardous elements in the leachates were very low. Calcium, K, Mg, Na, and chloride concentrations were high but did not vary significantly among the four leaching experiments. Total concentrations of carbonate were much higher in leachates than in estuarine water. Both estuarine water and leachates showed negligible toxicity. Crystals identified in the solids obtained from the leachates by evaporation were halite, anhydrite, epsomite, dolomite, and polyhalite. The sediment showed the capacity to retain the majority of the potentially hazardous chemical elements. Remobilization of chemical elements from sediment by leaching was essentially negligible. The variation of total concentrations of Ca, carbonate, and sulfate in leachates indicates that the sediment contained reactive sulfides. Due to its composition, the sediment seems to be a dynamic system of pollution control, which should not be disturbed.

Potential of Tamarix africana and other halophyte species for phytostabilisation of contaminated salt marsh soils

Salt marsh plants are colonising wastes from a steel plant deposited on the Coina River Banks posing a potential contamination risk to the Tagus estuary ecosystem. The objectives of this study were to assess the uptake, accumulation and translocation of hazardous elements/nutrients in three spontaneous halophytic species, to evaluate the capacity of Tamarix africana to stabilise a contaminated salt marsh soil, and to evaluate the ecotoxicity of the pore water and elutriates from phytostabilised soils. The work comprises the following: fieldwork collection of soil samples from Coina River (an affluent of Tagus River) bank landfill, estuarine water and spontaneous plants (Aster tripolium, Halimione portulacoides and Sarcocornia sp.), and greenhouse studies (microcosm assay) with T. africana growing in one landfill salt marsh soil, for 97 days, and watered with estuarine water. Soils were analysed for pH, EC, Corganic, NPK, iron and manganese oxides. Soils total (acid digestion) elemental concentrations were determined by ICP/INAA. Estuarine waters, plants roots and shoots (acid digestion), soils available fraction (diluted organic acids extraction-RHIZO or pore water), and salts collected from the T. africana leaves surface were analysed for metals/metalloids (ICP-MS). Ecotoxicity assays were performed in T. africana soil elutriates and pore waters using Artemia franciscana and Brachionus plicatillis. Soils were contaminated, containing high total concentrations of arsenic, cadmium, chromium, copper, lead and zinc. However, their concentrations in the available fraction were <4 % of the total. The estuarine waters were contaminated with cadmium, but negligible ecotoxicological effect was observed. The spontaneous plants had significant uptake of the above elements, being mostly stored in the roots. Elemental concentrations in the shoots were within the normal range for plants. These species are not hazardous elements accumulators. Tamarix africana was well adapted to the contaminated saline soils, stored the contaminants in the roots, and had small concentrations of hazardous elements in the shoots. Excretion of hazardous elements by the salt glands was also observed. Elutriates from soils with and without plant did not show ecotoxicity. The salt marsh species play an important role in the stabilisation of the soils in natural conditions. Tamarix africana showed potential for phytostabilisation of saline-contaminated soils. The low translocation of the elements from roots to shoots and/or active excretion of the elements by the salt glands was a tolerance mechanism in T. africana.