Chemical speciation and risk assessment of cadmium in soils around atypical coal mining area of China

The distribution characteristics of Cadmium (Cd) fractions in soils around a coal mining area of Huaibei coalfield were investigated, with the aim to assess its ecological risk. The total Cd concentrations in soils ranged from 0.05 to 0.87 mg/kg. The high percentage of phyto-available Cd (58%) when redox or base-acid equilibria changed. Soil pH was found to be a crucial factor affecting soil Cd fraction, and carbonate-bound Cd can be significantly affected by both organic matter and pH of soils. The static ecological evaluation models, including potential ecological risk index (PERI), geo-accumulation index (Igeo) and risk assessment code (RAC), revealed a moderate soil Cd contamination and prensented high Cd exposure risk in studied soils. However, the dynamic evaluation of Cd risk, determined using a delayed geochemical hazard (DGH), suggested that our studied soils can be classified as median-risk with a mean probability of 24.79% for Cd DGH. These results provide a better assessment for the risk development of Cd contamination in coal mining areas

A comparative study on the mineralogy, chemical speciation, and combustion behavior of toxic elements of coal beneficiation products

The huge demand for high-quality coal in China has resulted in increased generation of preparation plant wastes of various properties. A series of beneficiation products collected from a preparation plant were characterized to understand their petrographic and mineralogical characteristics, as well as thermochemical and trace element behavior during combustion. The minerals in the Luling preparation plant wastes from Huaibei coalfield mainly included kaolinite and quartz, with minor calcite, ankerite, pyrite, illite, chalcopyrite, albite, K-feldspar, anatase/rutile, and iron-oxide minerals. Massive clay lumps of terrigenous origin, cleat-infilling carbonate, and pyrite of epigenetic origin were prone to be enriched in the middlings and coal gangue. Minor or trace heavy minerals also reported to the preparation plant wastes. The contents of low-density density vitrinite and liptinite were enhanced in the clean coal, while inertinite-maceral group were enriched in the middlings. The modes of occurrences of toxic elements differed between raw coal and the waste products; and their transformation behavior during heavy medium separation is largely controlled by clay minerals (V, Cr, Co, Sb, and Pb), carbonate minerals (Co and Pb), sulfide minerals (As, Cu, Ni, Cd, and Zn) and organic matters (V, Cr, Se, and Cu). Three groups were classified based on the volatile ratio (Vr) of toxic elements. Group 1 includes the highly volatile element Se with Vr &gt; 85%; Group 2 contained elements As, Pb, Zn, Cd and Sb, with the Vr in the range of 20&ndash;85% and V, Cr, Co, Ni and Cu with Vr less than 20% were placed into Group 3. Thermal reactivity of coal inferred from the combustion profiles could be significantly improved after coal beneficiation, whereas the increased inorganic components probably inhibited the thermal chemical reaction of wastes.<br style="line-height: normal; text-align: -webkit-auto; text-size-adjust: auto;" /

Operating conditions-induced changes in product yield andcharacteristics during thermal-conversion of peanut shell to biochar inrelation to economic analysis

The influences of pyrolysis conditions on the products yield distribution and physico-chemical characteristics of biochar derived from peanut shell in a fixed-bed reactor were investigated in this study. The pyrolysis conditions included the pyrolysis temperature (300&ndash;700 &deg;C), retention time (15&ndash;90 min), heating rate (1&ndash;10 &deg;C min&minus;1), gas flow rate (20&ndash;200 mL min&minus;1) and feedstock particle size (&lt;0.075, 0.075&ndash;0.150, 0.150&ndash;0.300 and 0.300&ndash;2.00 mm). Various analytical techniques were used to characterize the biochar for ultimate and proximate analyses, higher heating value (23.99&ndash;30.44 MJ kg&minus;1), pH (8.11&ndash;12.89), electrical conductivity (22.78&ndash;34.44 mS cm&minus;1), surface functional groups (acidic, carboxylic and basic groups), Fourier transform infrared spectroscopy analysis, pore volume (0.055&ndash;1.241 cm3 g&minus;1) and specific surface area (7.12&ndash;20.96 m2 g&minus;1). The results demonstrated that the temperature predominantly regulated the product yields distribution and characteristics of produced biochar. Furthermore, the heating rate considerably influenced the biochar proximate composition, micropore surface area and pore size. Particle size had significant influences on biochar surface porosity and bio-oil yield. The economic analysis of the pyrolysis system indicated its feasibility and superiority with a positive net present value of 12.07 &times; 106 USD after twenty-five years of operation

Presence of arsenic, mercury and vanadium in aquatic organisms of LaizhouBay and their potential health risk

This study aims at describing and interpreting concentrations of arsenic (As), mercury (Hg) and vanadium (V) in seven species of fish, three species of shellfish, one species of crab and two species of shrimp from the typical estuary-bay ecosystem. Arsenic, Hg and V differed among species, and the highest As, Hg and V were observed in shellfish. The stable nitrogen (&delta;15N) and carbon (&delta;13C) isotopes were determined to investigate the trophic interactions between fluctuating environment and aquatic species. Arsenic concentrations in samples were found negatively correlated with &delta;15N, implying biodilution effect of As through the food web, while Hg concentrations in samples were positively correlated with &delta;15N, indicating their biomagnification effect. The estimated daily intake values of Hg and V in this study were all below the oral reference dose. However, elevated As intakes of some aquatic organisms suggested a potential risk for frequent consumers

Heavy metals (As, Hg and V) and stable isotope ratios (δ13C and δ15N) infish from Yellow River Estuary, China

The Yellow River Estuary is a significant fishery, but at present there are few studies about the concentrations of arsenic (As), mercury (Hg) and vanadium (V) in fish from this area, which might cause potential health risk to fish consumers. The aim of this study was to research on the accumulation and potential sources of heavy metals in the fish of the Yellow River Estuary. Arsenic, Hg, V and stable isotope ratios (&delta;15N and &delta;13C) in 11 species of 129 fish were analyzed. Results showed that the concentrations of As and Hg were all lower than the guideline levels established by international organizations and legal limits by several countries. The mean concentrations of V in samples in this study were significantly higher than the results of previous studies on other regions. Arsenic, Hg and V significantly differed across species (P&nbsp;&lt;&nbsp;0.05), which might be due to the different foraging habitats and dietary habits of the studied fish. Values of &delta;15N and &delta;13C in fish from the study area ranged from 5.1&permil; to 14.6&permil; and from &minus;&nbsp;27.6&permil; to &minus;&nbsp;14.5&permil;, indicating a wide range of trophic positions and energy sources. There was evidence of bioaccumulation of Hg, which could be explained by the positive correlation between Hg concentrations and &delta;15N in fish. Through estimation of daily intake of inorganic As (iAs), Hg and V via fish consumption, the heavy metal contamination level of fish samples fell in an acceptable range, indicating no potentially hazardous for human health

Variations of concentration and composition of polycyclic aromatichydrocarbons in coals in response to dike intrusion in the Huainancoalfield in eastern China

Although extensive studies have been conducted on coals influenced by igneous intrusion, the changes of concentration and composition of polycyclic aromatic hydrocarbons (PAHs) in coals responding to this kind of geological rapid heating are largely unknown. In the present study, thirteen coal samples, including unaltered coal, thermally altered coal and a dike-coal contact sample were collected along a transect approaching an igneous dike intrusion from the No. 3 coal seam of the Zhuji coal mine in Huainan coalfield, China. These samples represent a broad range of coal ranks ranging from high volatile A bituminous to anthracite. Vitrinite reflectance (%Ro) profiles indicate a progressive increase in %Ro value from ambient levels of 0.87&ndash;1.02% to 5.16% and include an alteration occurring out to 3.6 m from the dike. Bulk chemical composition from proximate and ultimate analyses shows the typical trend with distance from the dike. The total amount of extractable PAHs (RPAH35), US-EPA priority pollutant PAHs (RPAH16) and carcinogenic PAHs (RPAH8) range from 3.4&ndash;81.1 lg/g, 2.5&ndash;28.7 lg/g and 0.7&ndash;16.9 lg/g, respectively. PAH concentrations vary regularly with coal rank, reaching a maximum in low volatile bituminous coal (1.62 %Ro), located 3.5 m from the dike. This rank is higher than reported for coals not affected by contact metamorphism. Contact metamorphism has a dramatic effect on the coalification process and results in a different relationship between the PAH maximum concentration and coal rank. The igneous dike intrusion also has a significant effect on PAH distributions, where the proportions of 4&ndash;6 ring PAHs decrease toward the coal-dike contact and PAHs are dominated by those with 2 and 3 rings. The thermally altered coals show a decrease in alkylation compared with that of the unaltered coals, and the dealkylation process is apparently accompanied by the cross linking reaction of PAHs to form a more compact structure of organic macromolecule.</p

Thermal behavior and Raman spectral characteristics of step-heatingperhydrous coal: Implications for thermal maturity process

Perhydrous coal (PHC) had been widely investigated; however, a systematic research on the relationship between the structure of PHC and its thermal reactivity was rarely reported in the previous studies. The PHC was widely developed in the Carboniferous-Permian coal-bearing strata in the northern and eastern regions of the Huainan coalfield. In this study, we chose No. 13-1 PHC as the research object. Based on the macroscopic observation of No. 13-1 PHC of the borehole #9-3 and its logging response, a typical PHC sample was selected and pyrolyzed using a thermogravimetric analyzer (TGA) to acquire a set of coal samples after pyrolysis with wide range of random vitrinite reflectance (% VRo) from 0.86 to 7.79%. The thermal evolution process of PHC before and after pyrolysis was investigated by atomic force microscopy (AFM) and Raman spectroscopy. Research results show that: 1) in the experimental temperature range, the reflectance (VRo) range of PHC varied greatly; 2) with the increase of pyrolysis temperature, the Raman spectra of PHC changed significantly in the D band of disordered structure and the G band of ordered structure and the orderliness of its macromolecule particle arrangement was increasing gradually; 3) the relationship between the thermal reactivity of PHC and its Raman structure parameters was established, the FWHM of G-band can be used as indicators of the degree of thermal evolution of PHC; 4) compared with the G FWHM of normal coal with different rank, the thermal reaction temperature of PHC was advanced. Under the premise of comparable reaction temperature, the thermal maturity of PHC was gradually higher than that of bituminous coal, and slightly lower than anthracite, indicating that the actual PHC thermal maturity was suppressed by a higher amount of hydrogen

Distribution, Origin, and Characteristics ofn-Alkanes in Surface Soils from the Yellow RiverDelta Natural Reserve, China

A total of 46 surface soil samples were collected from the Yellow River Delta Natural Reserve (YRDNR) and the adjacent area of the reserve. These samples were analyzed for thirty n-alkanes (C-10-C-39) using gas chromatography-mass spectrometry. Twenty-four n-alkanes (C-12-C-35) were detected in the samples. In most of the samples, bimodal distribution pattern was observed, whereas unimodal distribution pattern was identified in only a few samples. The total concentrations of n-alkanes in the YRDNR varied from 0.361 to 1.16 mg kg(-1) (mean, 0.643 mg kg(-1)), which is higher than the outside area of natural reserve (0.516 mg kg(-1)). The soil was contaminated by oil fields located in the natural reserve with low contamination level. Diagnostic ratios and principal component analysis indicated that mixed sources of pollution, such as aquatic organisms, terrestrial higher plants, and oil-related hydrocarbons, has contributed to the hydrocarbon contamination of the area. Some sorts of remedial measures are necessary for protecting the ecological environment of the natural reserve. The results from the present research work are of great significance for developing effective counter measures to reduce the adverse effects of anthropogenic activities to the estuarine wetland ecosystem

Bioavailability and mobility of heavy metals in soilin vicinity of a coal mine from Huaibei, China

This study investigated the concentrations of Co, Cr, Cu, Mn, Ni, Pb and Zn in surface soil and corn cob samples collected from agricultural fields near a coal mine from Huaibei, China. Meanwhile, the mobility and availability of heavy metals in soil samples were evaluated by a modified three-step The European Community Bureau of Reference (BCR) sequential extraction procedure. The total concentrations of metals in soil pose no ecological threats to the local plants. Transfer factors of essential metals, Cu and Zn, as well as those of non-essential metal Pb, were higher than those of the remained metals. The results of BCR fractionation analysis revealed that the acid soluble, reducible and oxidizable fractions of the Mn, Pb and Zn were higher than those of the residual fraction, suggesting that these elements may be more bioavailable. The pH and organic matter contents of soil were significant parameters affecting speciation of metals in soil samples. Hierarchical cluster analysis indicated significant correlations between metal levels in corn grains and more available (acid soluble and reducible) fractions in soil, indicating that heavy metals in the first two fractions were more available for corn crops. The elevated mobility and bioavailability of Pb in soil are of great concern in the study area

Tracking historical mobility behavior and sources of lead in the 59-year sediment core from the Huaihe River using lead isotopiccompositions

A historical perspective of past 59 years (1955-2014) for contamination and isotopic composition of Pb in sediment core system of the Huaihe River, Huainan City, Anhui Province of China is presented. Detailed investigation regarding changes in Pb sources, enrichment factor, sequential extraction and isotopic analysis revealed that high Pb concentrations were detected along the core, especially during the first two decades (1955-1974). Large variations in Pb isotopic compositions were observed, with 206Pb/207Pb and 208Pb/207Pb values ranging from 1.1504-1.1694, and 2.0817-2.1380, respectively. Diverse Pb sources were identified for sediment contamination over the time. Among anthropogenic sources, metallurgic dust and leaded petrol were on top during 1955-1974, especially when the Great Leap Forward Movement (1958-1960) was in progress in China, the time numerous small industries were established without wastewater treatment facility. However, coal and coal combustion were recognized as the primary sources of Pb emissions for the recent four decades (1974-2014) due to tremendous increase of coal consumption for power and heat generation. Unleaded vehicle exhaust, waste incineration and industrial emission were also sources of Pb during the years 1974-2014. Our estimates based on geochemical and lead isotopic approaches have shown that anthropogenic Pb contributions varied from 4.35 to 92.01%, and 13.28-99.06%, respectively. Assessment of lead speciation indicated an overwhelming presence of reducible fraction (Fe-Mn hydro-(oxides)) in the sediment core, except during 1995-1997, which was thought to be affected by water pollution accidents caused by heavy rainfall