Harmful Trace Elements Research Articles

Geochemical characteristics of No. 6 coal from Nanyangpo Mine, Datong coalfield, north China: Emphasis on the influence of hydrothermal solutions

This paper discusses the volcanic influence on the mineralogical and elemental geochemistry of No. 6 coal from Nanyangpo Mine in the Datong coalfield, north China. Sixteen samples (14 coal and 2 partings) were analyzed by different geochemical methods. The results revealed that the No. 6 coal is a medium–high volatility, highly calorific, bituminous coal with a low-ash and medium-sulfur content. The minerals mainly consisted of kaolinite, calcite, dolomite, and pyrite. In addition, traces of apatite, sphalerite, and anatase were also found. Calcite, dolomite, and pyrite in the coal samples were mainly derived from epigenetic hydrothermal solutions, whereas kaolinite and apatite originated from volcanic ash. Harmful trace elements including Pb, Cu, Mo, Tl, and Hg in the No. 6 coal samples were higher than those of common global coals. These harmful elements mainly occurred in sulfide minerals, which were probably influenced by hydrothermal inputs.

Distribution of Potential Harmful Trace Elements and Potential Ecological Risk in the Jiulongchi Wetland of Fanjing Mountain, Southwest China.

In order to understand the distribution and ecological risk of potential harmful trace elements (PHTEs) in the high altitude areas of the Fanjing Mountain World Natural Heritage Property, 30 surface samples including soil and plants were collected in April, 2019 in the Jiulongchi wetland which lies in the saddle between the New Jinding Peak of Fanjing Mountain and Fenghuang Peak. The contents of 23 major and trace elements were determined, and the pollution characteristics and potential ecological risk of 11 PHTEs (Mn, V, Zn, Cr, Co, Ni, Cu, As, Cd, Sb and Pb) were discussed. The element contents showed significant differences in plant and soil samples. Enrichment factor and single-factor pollution index demonstrated that Mn, Zn, Co, As and Cd in the soil were in a clean state. The potential ecological risk index and pollution load index indicated an overall good ecological condition of Jiulongchi wetland, with a weak pollution degree. Comparisons of relevant studies showed the anthropogenic activities have considerable impacts on the pollution status of PHTEs with significant spatial differences in Fanjing Mountain. Multivariate statistical analysis proved that Pb and Sb were main pollutants of the soil in the Jiulongchi wetland, and the mining and smelting of minerals such as mercury, manganese and lead-zinc ore in the adjacent areas could be the main pollution sources through atmospheric deposition. This study could provide targeted strategies for the environmental protection and management of the Property and give scientific evidence for the pollution prevention in southwest China.

Room temperature solvent extraction for simple and fast determination of total concentration of Ca, Cu, Fe, Mg, Mn, and Zn in bee pollen by FAAS along with assessment of the bioaccessible fraction of these elements using in vitro gastrointestinal digestion

Background and aimBee pollen is recognized to be a source of different nutrients, including minerals. As a food supplement, its quality and safety due to concentrations of essential macro- and microelements, and harmful trace elements has to be verified. Fast and simple element analysis of bee-collected pollen can be regarded as an important part of its quality assurance and control. The present study aimed at developping a new method for determination of selected elements (Ca, Cu, Fe, Mg, Mn, Zn) of bee pollen based on solvent extraction and completely avoiding a high temperature treatment with concentrated reagents. In addition, in vitro gastrointestinal digestion was used to assess bioavailability of elements from this food supplement. MethodsBee pollen samples were dried and pulverized. Total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn were determined by flame atomic absorption spectrometry (FAAS) in sample solutions obtained by wet digestion (WD) in concentrated HNO3 or alternatively by solvent extraction (SE) with diluted solutions of HNO3. Gastrointestinal digestion was mimicked using simulated solutions of gastric and intestinal juices followed by determination of Ca, Cu, Fe, Mg, Mn and Zn concentrations in the bioaccessible fraction by FAAS. ResultsA new simple and fast method for determination of total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn in bee pollen was developed and validated. The method combined room temperature, two-hour SE with 0.5 mol L−1 HNO3 with FAAS measurements versus simple standard solutions. It provided precision within 1–5 % and trueness better than 8%, and was shown to be suitable for fast analysis of different polyfloral bee pollens. In vitro gastrointestinal digestion revealed that elements were well (70–85 % for Ca, Mg) and fairly (27–43 % for Cu, Fe, Mn, and Zn) bioaccessible from bee pollen. By pouring with water and swelling overnight, bioaccessibility of studied elements from such prepared bee pollen was increased on average by less than 15 % (Mn), 20 % (Ca, Cu, Fe, Zn) or 30 % (Mn). ConclusionsAvoiding long-lasting, high-temperature wet digestion with concentrated reagents, the proposed sample treatment along with FAAS provided precise and true results of total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn in bee pollen. The method was simple and fast, and enabled to analyze a higher number of samples. Simulated gastrointestinal digestion of bee pollen have shown for the first time that Ca and Mg are the most bioaccessible from this bee product. Bioaccessibility of Cu, Fe, Mg, and Zn from bee pollen are close to or lower than 40 %.

Enhanced Weathering and related element fluxes – a cropland mesocosm approach

Abstract. The weathering of silicates is a major control on atmospheric CO2 at geologic timescales. It was proposed to enhance this process to actively remove CO2 from the atmosphere. While there are some studies that propose and theoretically analyze the application of rock powder to agricultural land, results from field experiments are still scarce. In order to evaluate the efficiency and side effects of Enhanced Weathering (EW), a mesocosm experiment was set up and agricultural soil from Belgium was amended with olivine-bearing dunite ground to two different grain sizes, while distinguishing setups with and without crops. Based on measurements of Mg, Si, pH, and DIC, the additional weathering effect of olivine could be confirmed. Calculated weathering rates are up to 3 orders of magnitude lower than found in other studies. The calculated CO2 consumption by weathering based on the outlet water of the mesocosm systems was low with 2.3–4.9 tCO2km-2a-1 if compared with previous theoretical estimates. Suspected causes were the removal or dilution of Mg as a weathering product by processes like adsorption, mineralization, plant uptake, evapotranspiration, and/or preferential flow, not specifically addressed in previous EW experiments for CO2 consumption. The observation that Mg concentrations in the upper soil layers were about 1 order of magnitude higher than in the outlet water indicates that a careful tracking of weathering indicators like Mg in the field is essential for a precise estimate of the CO2 consumption potential of EW, specifically under global deployment scenarios with a high diversity of ecosystem settings. Porewater Mg∕Si molar ratios suggest that dissolved Si is reprecipitating, forming a cation-depleted Si layer on the reactive mineral surface of freshly ground rocks. The release of potentially harmful trace elements is an acknowledged side effect of EW. Primarily Ni and Cr are elevated in the soil solution, while Ni concentrations exceed the limits of drinking water quality. The use of olivine, rich in Ni and Cr, is not recommended, and alternative rock sources are suggested for the application.

Nehézfém- és egyéb toxikus mikroelem-terhelés tartamhatása a főtermés mennyiségére szabadföldi kísérletben

Összefoglalás Dolgozatunkban a Kádár Imre által 1991 tavaszán meszes csernozjom talajon 13 potenciálisan toxikus mikro-/károselem (Al, As, Ba, Cd, Cr, Cu, Hg, Mo, Ni, Pb, Se, Sr és Zn) 0-90-270-810 kg ha−1 szintjeivel beállított szabadföldi tartamkísérlet 1-20. évi főtermés veszteség eredményeit értékeljük. Első megközelítésben, a főtermések relatív termésben kifejezett százalékos terméscsökkenéseit az egyes elemek átlagos fitoxicitása sorrendjében mutattuk be. A 90-270-810 kg ha−1 kezelések átlagában az egyes elemek fitotoxicitása az alábbi sorrendben csökkent: Se > Cr > Cd > Al > Pb > As > Mo > Hg > Cu > Ni > Zn > Ba > Sr. A legkisebb – a kontroll %-ában kifejezett - relatív terméseket, azaz a legnagyobb fitotoxikus hatást a Se, a Cr és a Cd mutattak, míg legkevésbé fitotoxikusnak a Ni, a Zn, a Ba és a Sr bizonyultak. A fitotoxikus évek számát illetően az elemek sorrendje az alábbiak szerint alakult: Se = As > Cr > Cd > Hg > Cu = Zn > Al = Mo > Ni = Pb > Ba = Sr. Legtöbb évben a Se, az As, a Cr és a Cd, míg legkevesebb évben a Ni, a Pb, a Ba és a Sr voltak fitotoxikusak. Átlagos terméscsökkentő hatásukat tekintve a Se, a Cr és a Cd már a 90 kg ha−1 adagtól, a Pb és a Hg a 270 kg ha−1 adagtól, míg az As és a Mo a legnagyobb, 810 kg ha−1 adagtól/adagnál mutatott 10%-nál nagyobb terméscsökkenést a fitotoxikus évek átlagában. Mind a fitotoxikusság mértéke, mind a fitotoxikus évek száma tekintetében, általában, a legnagyobb növényi károsodások az anionos formában kijuttatott elemekhez voltak köthetők, ezen belül is, főleg a nem esszenciális mikroelemekhez. Második megközelítésben, a fitotoxicitás mértékét a kísérleti növények, ill a kísérlet beállítása óta eltelt idő függvényében is nyomon követtük. A kísérleti növények közül legnagyobb terméscsökkenéseket a napraforgó, a spenót és az őszi árpa, míg legkisebbeket a harmadik, a második és az első éves lucerna növényekben kaptunk. Az idő múlásával egyre kisebb terméscsökkenéseket tapasztaltunk, a kísérlet 13. évétől kezdve az átlagos fitotoxicitás mértéke még a 10%-ot sem érte el. Megkülönböztetett figyelemmel kell nyomon kísérni a kadmiumot, amely az idő múlásával egyre kevésbé volt fitotoxikus, viszont még a kísérlet 18. évében is igen nagy könnyen oldható elemtartalmakat mutatott a talaj szántott rétegében.

Spatial Distribution and Ecological Risk Assessment of Potentially Harmful Trace Elements in Surface Sediments from Lake Dali, North China

Potentially harmful trace element (PHTE) pollution in lakes has important implications for regional management in North China, yet is seldom investigated. Surface sediments from 13 sites in Lake Dali were collected for PHTE analysis. Combined with the enrichment factor, potential ecological risk index, and multivariate statistical analysis, the spatial distribution and ecological risk of the pollutants were studied. The results showed that the contamination levels of As, Cd, Cr, Cu, Ni, Pb, and Zn were minor to moderate. Cd, Cr, Cu, Ni, Zn, and part of Pb pollution were mainly attributed to atmospheric deposition with the development of industry in North China, and As pollution resulted from the agricultural use of chemical fertilizers and As-containing pesticides. For the overall lake, the southwest part requires the most management, and targeted measures should be tailored to mitigate the ecological risk of PHTE pollution.

Nehézfém- és egyéb toxikus mikroelem-terhelés tartamhatása a talajból mért visszanyerési százalékuk alakulására szabadföldi kísérletekben

Összefoglalás Dolgozatunkban Kádár Imre 1991 tavaszán meszes csernozjom talajon 13 potenciálisan toxikus mikro- / károselem (Al, As, Ba, Cd, Cr, Cu, Hg, Mo, Ni, Pb, Se, Sr és Zn) 0-90-270-810 kg ha−1 szintjeivel beállított szabadföldi tartamkísérlete 1-20. évi talajvizsgálati-, illetve talaj visszanyerési százalék eredményeit értékeltük. A LE-oldható (NH4-acetát+EDTA) és „összes” (cc.HNO3+cc.H2O2) elemtartalmak aboszlút értékeinek változásai mellett figyelemmel kísértük az elemek visszanyerési százalékainak időbeni változásait is. A kísérlet 4. évében a legnagyobb talaj LE-oldható visszanyerési százalékokat a kationos formában kiadott elemek esetében kaptunk, míg az anionos formában kijuttatottak (Se, As, Mo, Cr) az elemsorrend második felében, illetve a végén helyezkedtek el. A kísérlet 18. évére a legtöbb elem LE módszer szerint kimutatott oldhatósága, és így visszanyerési százaléka kisebb-nagyobb mértékben csökkent. Legnagyobb csökkenéseket a Sr, Pb, Zn, míg legkisebbeket a Mo, Cr és Cd elemek mutattak. A tápláléklánc szennyeződése szempontjából kedvezőtlen, hogy a kijuttatott karcinogén Cd jelentős hányada maradt a könnyen oldható frakcióban, és ez a frakció a 14 év alatt is csak minimálisan csökkent a meszes csernozjom talajon. Az elemek átlagában, a LE-oldható elemtartalomban mért visszanyerési százalék 1994-ben 41%, míg 2008-ban 22% volt. A 14 év alatt tehát az átlagos, LE-oldható elemtartalomban mért visszanyerési százalék 19 abszolút %-kal csökkent, azaz gyakorlatilag megfeleződött. Az egyes elemek „összes” elemtartalomban a kísérlet 4. évében mért visszanyerési százalékának sorrendje a LE-oldható tartalmaknál leírtakhoz hasonlóan alakult; a legkisebb visszanyerési százalékokat itt is az anionos formában kijuttatott elemeknél kaptunk. Míg a LE-oldható tartalmaknál a Hg, addig az „összes” elemtartalmaknál a Cd, mint nehézfém ékelődött be az anion formában kijuttatott elemek közé. A kísérlet 18. évében az „összes” elemtartalomban mért visszanyerési százalékok esetében a legnagyobb csökkenéseket a Se, Sr, Pb, míg legkisebbeket a Cd, Mo és Cr elemek mutattak. Az utóbbi három elem közül humán egészségügyi szempontból a Cd tekinthető a legveszélyesebbnek. Az elemek átlagában, az „összes” elemtartalomban mért visszanyerési százalék 1994-ben 81%, míg 2008-ban 49% volt. A 14 év alatt tehát az átlagos összes elemtartalomban mért visszanyerési százalék 32 abszolút %-kal Csökkent. A meszes csernozjom, meszes homok, és savanyú, agyagos vályog textúrájú barna erdőtalajon beállított károselem-terheléses tartamkísérlet adatainak tanúsága szerint a LE-oldható elemtartalomban kifejezett, és az „összes” elemtartalomban kifejezett visszanyerési százalékok egymáshoz viszonyított aránya inkább elem-, mint talajtulajdonság-függő. Úgy találtuk, hogy a három, egymástól jelentősen eltérő tulajdonságú talajon viszonylag azonos időben, azonos mennyiségben és azonos formában kijuttatott potenciálisan káros elemeknek a LE-oldható elemtartalomban mért visszanyerési százalékok és ”összes” (cc.HNO3+cc.H2O2-oldható) elemtartalomban mért visszanyerési százalékok arányainak sorrendje állandó, tehát a talajtulajdonságoktól független volt. Ezen felismerés alapján fogalmaztuk meg a Szabó-Csathó-Kádár-féle potenciálisan toxikus talaj-mikroelem kiterjeszthetőségi szekvens megnevezést. Természetesen ezen hipotézisünket még számos más talajtípuson, hasonló feltételekkel beállított tartamkísérletben is szükséges lenne bizonyítani.

In vitro assessment of oral and respiratory bioaccesibility of trace elements of environmental concern in Greek fly ashes: Assessing health risk via ingestion and inhalation

Fly ash engender significant environmental and human health problems due to enhanced contents of potentially harmful trace elements (TrElems). This study aims to evaluate human exposure to TrElems via a combined ingestion (i.e., oral bioaccessibility) and inhalation (i.e., respiratory bioaccessibility) pathway. Five fly ash samples were collected from power plants operating in the main lignite basins of Greece, while the ingestible (<250 μm) and inhalable (<10 μm) particle size fractions were utilized. The Unified Bioaccessibility Method (UBM) was utilized to assess the oral bioaccessibility, while the respiratory bioaccessible fractions were extracted using the Artificial Lysosomal Fluid (ALF). All studied FAs exhibited significantly higher contents in Ba, Cr, Ni, V and Zn. Cadmium was presented relative enriched in the finer size fraction (<10 μm), while Ba, Co, Cr, Cu, Mn, Ni and V were depleted. The UBM-extractable concentrations fluctuated greatly among the studied FAs, while notably lower bioaccessible contents were recorded in the gastrointestinal phase. On the other hand, ALF-extractable concentrations were surprisingly higher than the corresponding UBM-extractable ones in the gastric phase. The oral bioaccessibility of the studied TrElems ranged from 12.5 to 100%, while respiratory bioaccessibility presented high values exceeding 45% on average. A significant effect of fly ash type on human bioaccessibility was revealed. Thus, high-Ca FAs exhibited significantly higher bioaccessibility of the studied TrElems via ingestion, while a relatively higher bioaccessibility via inhalation was observed for high-Si FAs. Regarding non-carcinogenic health risk via ingestion and inhalation, Cr and Co exhibited the highest HQing and HQinh values, however there were significantly lower than safe level (HQ < 1). On the contrary, Cr was the dominant contributor to carcinogenic risk with CR values being well above threshold or even tolerable risk levels.

Geochemical signature of superhigh organic sulphur Raša coals and the mobility of toxic trace elements from combustion products and polluted soils near the Plomin coal-fired power station in Croatia

In the northern Adriatic coast of Croatia, combustion of super-high organic sulphur rich Raša coal was common between 1970 and 2000. These Late Paleocene coals are enriched in a number of trace elements. This work aims to provide a detailed study on the distinctive geochemical patterns of the Raša coal and investigate the environmental effects of the coal and combustion by-products on the area. Several analytical techniques were used to study the mode of occurrence, distribution, levels and solubility of major and trace elements in the Raša coal, fly ash, slag and soils in an area within 10 km from the power station. Due to the sulphur-rich calcareous depositional environment of the Raša coal, the combustion by-products are enriched in S and Ca. Fly ash and slag are enriched in potentially harmful trace elements i.e. Se, Mo, Hg, V and U. Similar enrichment pattern was found for soils suggesting that resuspension and deposition of airborne coal and fly ash particles, transport of gaseous species in the flue gas by dominant winds and/or leaching from ash deposits may have affected the wider environment. Whilst a large number of trace elements were found to be poorly soluble across samples, the leachable concentrations of Se, Cr and Mo in fly ash and slag are noteworthy. Their organic association in coal enhances volatilisation during combustion and then further condensation on ash particles as readily soluble oxyanionic species. Other oxyanionic metalloids such as As or V were insoluble in fly ash and slag, due to precipitation of solubility-limiting Ca-bearing species.

Distribution characteristics and migration patterns of hazardous trace elements in coal combustion products of power plants

Trace elements in coal produce migration and enrichment after combustion, the enrichment and release of hazardous trace elements will cause effective harmful to human health and the environment. In this paper, the distribution characteristics and occurrence state of hazardous trace elements in coal combustion products were studied by measuring the concentration of harmful trace elements in coal, slag, coarse ash, fine and fly ash. The experimental study of step-by-step chemical extraction was carried out, the migration and transformation model of trace elements in coal combustion process was investigated. The results show that the trace elements are easily enriched in fine particles of coal ash. The occurrence state of elements in combustion products has changed obviously, and the concentration of residual state has increased for example aluminosilicates. According to the enrichment index REI (Relative Enrichment Index), hazardous elements can be classified into three categories: (I) The elements left in both solid waste slag and fly ash are Cr, Mn and Ni (REI > 0.85); (II) The elements left in solid waste are Be, Co, Cu, Zn, Cd, Ba, Pb and U (0.1 < REI < 0.85); (III) The elements mainly volatilized into the atmosphere are few, only Sb (REI < 0.1).

Effect of occurrence mode of heavy metal elements in a low rank coal on volatility during pyrolysis

The harmful trace elements will be released during coal utilization, which can cause environment pollution and further endangering human health, especially for heavy metal elements. Compared to combustion, the release of heavy metal elements during coal pyrolysis process, as a critical initial reaction stage of combustion, has not received sufficient attention. In the present paper, a low rank coal, from Xinjiang province in China, was pyrolyzed in a fixed bed reactor from room temperature, at atmospheric pressure, with the heating rate of 10 °C/min, and the final pyrolysis temperature was from 400 to 800 °C with the interval of 100 °C. The volatility of heavy metal elements (including As, Hg, Cd and Pb) during pyrolysis process was investigated. The results showed the volatility of all heavy metal elements increased obviously with increasing temperature, and followed the sequence as Hg > Cd > As > Pb, which was mainly caused by their thermodynamic property and occurrence modes in coal. The occurrence modes of heavy metals were studied by sink-and-float test and sequential chemical extraction procedure, and it can be found that the heavy metal elements were mainly in the organic and residual states (clay minerals) in the raw coal. And most of the organic heavy metals escaped during the pyrolysis process, the remaining elements were mainly in the residual state, and the elements in Fe–Mn state also tended to remain in the char.

Suppression processes of anionic pollutants released from fly ash by various Ca additives.

Harmful trace elements, which are initially included in the coal fly ash, have the potential to be leached when coal fly ash comes in contact with water. This causes a risk of pollutant species being released, considering the long lifetime of building structures where coal fly ash was applied. Some Ca additives effectively function to suppress the release of anionic pollutants; however, the detailed suppression processes remains unclear. In this work, the influences of various Ca additives on the released anionic pollutants (B, F, S, As, and Cr) was systematically investigated. According to the comprehensive results of solution data with the solid characterization, the 60% hydroxylated calcined dolomite (HCD 60) was the best Ca additive for the suppression of different anionic pollutants since this Ca source not only simply provides an alkaline reagent but also supplies MgO and Mg(OH)2, which affect the phase transformation that accompanies with hydration. The phase transformation occurs from Ca(OH)2 to ettringite via hydrocalumite, which is the most important suppression processes of released pollutants. The precipitation of Ca salts is another pathway to immobilize these pollutants. In this scheme, MgO and Mg(OH)2 were proven to enhance the formation of ettringite and hydrocalumite, respectively.

Centennial records of cadmium and lead in NE China lake sediments

Cores (15 to 40 cm of depth) were collected from 11 lakes of the Songnen Plain in northeastern China to reconstruct changes in potentially harmful trace element (PHTE) inputs as tracers of human activities. In each profile, most PHTE enrichment factors do not differ significantly from the pre-industrial values (EF < 1.5), except for Cd (EF = 2–5.5). This shows that detrital material accounts for a large part of the PHTE supply to the Songnen Plain lakes. Radiometric dating of the cores (210Pb, 137Cs) showed that Cd contamination started from the mid-20th century and sharply increased in the 1980s', a pattern that matches the rapid economic and industrial growth of China. Comparison with other records in China suggests that a large part of the anthropogenic Cd in these lakes is likely local in origin. Although the Cd inputs, controlled by carbonate minerals, probably originated from a combination of sources, an intensification in agricultural practices, through the use of chemical fertilizers, manure and wastewater would explain these discrepancies between records. These findings highlight the importance of local factors on the Cd geochemical cycle in China. The large anthropogenic component of the Cd inventory compared to other PHTEs (Cu, Ni, Pb, Sb, V, Zn) and its high toxicity indicate that it should be prioritized in future environmental management.

Ecological risk assessment and distribution of potentially harmful trace elements in lake sediments of Songnen Plain, NE China

In order to understand the distribution and the ecological risk of the potentially harmful trace elements (PHTEs) in lake sediments of Songnen Plain, northeast (NE) China, an integrated survey of PHTEs (As, Cd, Cr, Cu, Ni, Pb, Zn and Ti) was conducted in July 2015 in 11 shallow lakes adjacent to Qiqihar and Daqing. The enrichment factor (EF) and Index of geoaccumulation (Igeo) results showed that Cd was obviously enriched in all lakes and reached the moderate pollution level. A comparison of PHTE concentrations in the lake sediments from 2005 to 2015 found the PHTEs pollution status doubled. Multivariate statistical analysis identified the heavy industries of petroleum and steel in the cities close to lakes and excessive agricultural fertilizing in the region as possible pollution sources of the PHTEs. The Håkanson index method (RI) and the sediment quality guidelines (SQGs) were used to assess the potential risk of PHTEs in sediments. The risk degree of 11 lakes had reached a medium level of potential ecological risk except for one lake which had a low potential ecological risk status. The Songnen Plain has been significantly affected by anthropogenic activities and this study provides an effective reference for the environmental protection and management of lakes (heavy metal pollution and control) around the heavy industrial cities of China and the world.

English

Assessment and distribution of the concentration of potentially harmful trace elements (PHTEs) is important for environmental health management. The concentrations of thirteen PHTEs were determined in the stream sediments and rocks samples from the underlying bedrock with the use of inductively coupled plasma-mass spectrometry (ICP-MS). Multivariate statistics and principal component analyses were used to identify and characterize trace elemental associations in the system. Trace elements ranged from 0.01 mg/kg as found in Cd concentration to 1591.00 mg/kg as found in Mn. Trace element concentrations vary from one location to another. The geochemistry of the underlying rocks including granite, quartzite and banded gneiss were far lower in metal concentration compared to that of the stream sediments. The concentrations of U (0.40 – 14.40 mg/kg), Mn (51.00 - 1591 mg/kg) and La (7.10 – 364.90 mg/kg) were of great concern to the ecosystem because of their relatively higher values in the stream sediments compared with the control, which is the average earth crust values. The results of enrichment factor and ecological risk index showed that Cu, Pb, As and Cd did not raise any eco-toxicological concern. From the results of the other elements analysed, there were considerable lower metal enrichment in terms of contamination status when compared with the background values. Metals such as Cr, Mn, Pb, Zn, Cu, Ni, V, As, Th, Cd, and La were positively correlated with each other (r = 0.51 - 0.95), which indicated analogous sources of geochemical characteristics. However, from the result, it is seen that there is considerable input of the metal concentration in the stream sediments possibly from man induced activities of these PHTEs in the drainage system of the catchment areas. Key words: Harmful trace elements, ecological risk, ecosystem, Okemesi, Ijero, stream sediment.

Study of harmful trace elements and rare earth elements in the Permian tectonically deformed coals from Lugou Mine, North China Coal Basin, China

The No.2-1 coal (Early Permian-Shanxi Formation) in the Lugou Mine, Xinmi coalfield, Northern China, is a characteristic tectonically deformed coal. A total of 15 coal bench samples were considered, including 13 bench samples, one roof, and one floor. In this study, the content, distribution, and occurrence of harmful trace elements and rare earth elements (REE) (HR) were investigated by low-temperature ashing prior to powder X-ray diffraction (LTA-XRD), X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS), and field emission scanning electron microscopy equipped with energy-dispersive X-ray analysis (FESEM-EDX). The results showed that the No. 2-1 coal is a low-medium ash yield (23%) and ultralow sulfur content (0.32%) meager coal. Minerals detected in this coal included clay minerals such as kaolinite, illite, and smectite, and non-clay minerals such as quartz, calcite, ankerite, tobelite, pyrite, and anatase. Compared with the Clarke values, selenium is unusually enriched (6.51 μg/g, CC = 130.20.), and arsenic is enriched (13.15 μg/g, CC = 7.31), while the content of other elements is normal: mercury (0.24 μg/g, CC = 2.40), vanadium (49.09 μg/g, CC = 0.36), chromium (38.77 μg/g, CC = 0.39), manganese (16.90 μg/g, CC = 0.02), lead (21.65 μg/g, CC = 1.73), cobalt (13.98 μg/g, CC = 0.56), nickel (22.76 μg/g, CC = 0.30), and ∑REE (96.20 μg/g, CC = 1.40). It is necessary to pay special attention to selenium and arsenic due to their potential impact on environment. By analyzing the trace element contents in vertical and adjacent layers, and the REE distribution patterns, we concluded that the coal seam has turned into a typical tectonically deformed coal due to the strong tectonic destruction and plastic deformation, yet we found no evidence that this could cause local enrichment or redistribution of the HR in the coal seam. The analysis of the correlation between the HR and ash yield, percentage of minerals, and main inorganic element content using FESEM-EDX showed that the majority of vanadium, chromium, lead, nickel, and REE mainly originate from kaolinite or illite, while mercury and selenium originate from pyrite.

Release Behavior of Se from Coal into Aqueous Solution

The release of harmful trace elements from solid such as coal into the water is closely related to human health. The aim of this paper is to study the release procedure of selenium (Se) from coal in aqueous solution. Effects of contact time, pH, and temperature were investigated via a set of batch release tests. Experimental results were also analyzed from the aspects of dynamics and thermodynamics. Batch release tests showed that the release capacity of Se increasees with the increase of contact time and temperature, and it is higher in strong acid or alkaline conditions than in neutral conditions. Dynamic fitting analyses indicated that the release model of Se from coal into water is different with different pH values, and the applicability of different models suggested that the release mechanism of Se is multiple. The first-order kinetics fitting demonstrated that the release procedures of Se from coal into the water with the initial solution pH of 3 and 11 are two-stage release processes. And the best...

Total reflection X-ray fluorescence as a convenient tool for determination of trace elements in microscale gasoline and diesel

Quantitative determination of trace elements like S, Fe, Cu, Mn and Pb in gasoline and S in diesel is of great importance due to the growing concerns over air pollution, human health and engine failure caused by utilization of gasoline and diesel with these harmful elements. A method of total reflection X-ray fluorescence (TXRF) was developed to measure these harmful trace elements in gasoline and diesel. A variety of factors to affect measurement results, including TXRF parameters, microwave-assisted digestion conditions and internal standard element and its addition, were examined to optimize these experimental procedures. The hydrophobic treatment of the surface of quartz reflectors to support the analyte with neutral silicone solutions could prepare thin films of gasoline and diesel digestion solutions for subsequent TXRF analysis. The proposed method shows good potential and reliability to determine the content of harmful trace elements in gasoline and diesel with high sensitivity and accuracy without drawing different standard calibration curves, and can be easily employed to screen gasoline and diesel in routine quality control and assurance.

Volatilization of mercury in coal during conventional and microwave drying and its potential guidance for environmental protection

During the thermal drying process of coal, the sufficient attention has been paid to the changes in the properties of coal before and after the drying process. However, the volatility characteristics of harmful trace elements in coal during the drying process are always neglected to date, whereas the volatilization of harmful trace elements not only has significant effects on the surrounding atmosphere environment but also influence the following utilization of dried coal. In this study, the volatility characteristics of both the moisture and mercury in the coal sample during conventional (electric blast oven) and microwave (microwave oven) drying processes were investigated. In addition, the changes in the surface properties of coal before and after the drying process were studied using X-ray photoelectron spectroscopy (XPS) analysis. The results show that the moisture content of coal decreases in non-line format (decreases slowly at the first and then quickly according to the drying time) in the conventional drying process, while it decreases in line format in the microwave drying. The microwave drying process needs much shorter time required to obtain the dried coal of a certain moisture content than the conventional drying process. Under the same volatilization rate of moisture, the volatilization rate of mercury in the microwave drying process is always greater than that in the conventional drying process. Nearly half or more (49.73% and 59.26%, respectively) of the mercury in the coal slime evaporates into the atmosphere after the drying processes. XPS results show the content of CC and CH groups on the coal surface increased, but the CO content decreased after the drying processes and the microwave drying process has a stronger ability to remove oxygen-containing functional groups than the conventional drying process.

Environmental impact and potential use of coal fly ash and sub-economical quarry fine aggregates in concrete

The Israeli quarry industry produces 57 Mt of raw material and ∼4–6Mt of associated sub-economical by-products annually. These sub-economical quarry fines are not used because production and transportation costs considerably exceed their retail value. Therefore these by-products, are stored in large piles of fine grain size particles, create environmental risks to their surrondings.This paper evaluates the possibility of mixing the sub-economical quarry by-products of two Israeli quarries with sub-economical Class F coal fly ash (<20wt.% CaO) to form an economical aggregate sand substitute to be used as a concrete filler product.To study the feasibility of the aggregate as partial substitute to sand in concrete several analyses, including leaching experiements (EN12457-2), analytical techinques (SEM-EDX, ICP-MS, ICP-AES, and XRD), as well as an analysis of the mechanical and chemical properties of the concrete aggregate (strength, workability, and penetration) were performed. Scrubbing quarry waste with coal fly ash was found to be very effective for reducing the leaching rate of potentially harmful trace elements. In addition, adding fly ash with quarry fines as partial substitute to sand enhanced the performance of the concrete mixture and the properties of the fresh and harden concrete.