An 87-year sedimentary record of mercury contamination in the Old Yellow River Estuary of China

A sediment core, spanning from the year 1925 &plusmn; 3.03 to 2012, was collected for analyzing historical distribution of mercury (Hg) in the Old Yellow River Estuary (OYRE), China. The Hg concentrations in the sediment core ranged from 14 to 351 ng g&minus;1, with the high values occurred in the middle layers (1960&ndash;1996), which may be resulted from intensive human activities during this period, such as oil exploitation and booming of petrochemical industry, salt chemical industry and chlor-alkali plants. A significant positive correlation was found between THg and loss on ignition (LOI). The main fraction of Hg existed in residual part while the fraction that was easy to leach out from sediments accounted for only a small portion according to the results of BCR sequential extraction procedure. Multiple ecological risks indices and guidelines of Hg indicated that the sedimentary record presented an &ldquo;intermediate state&rdquo; for Hg contamination in the OYRE.</p

CONCENTRATIONS AND SOURCES OF POLYCYCLIC AROMATIC HYDROCARBONS IN WATER AND SEDIMENTS FROM THE HUAIHE RIVER, CHINA

Surface water and sediments were collected from eleven locations on the middle region of Huaihe River to evaluate the environmental effects of urban and industrial activities. The concentrations of sixteen polycyclic aromatic hydrocarbons (PAHs) in water and sediments were between 1.2-5.1 mu g/L and 72-139 ng/g, respectively. High levels of PAHs in water were recorded in comparison to those of other countries, while the concentrations in sediments were low to moderate levels. A weak positive correlation was observed (R-2 = 0.49, P = 0.13) between PAHs and total organic carbon in water. However, a significant positive correlation (R-2 = 0.79, P = 0.004) was found in sediments, which indicated that total organic carbon was a factor in PAH levels in sediments but not in water. The parent ratios were studied by principal component analysis that showed the PAHs from water were predominantly derived from coal combustion (34%), oil spills (49%), and vehicular emissions (17%), while the major PAH sources to sediments were coal combustion. Using the ecological toxic equivalency factor index, it was concluded that the PAHs levels may provide a potential risk in water but not in sediments.</p

Concentration and Fractionation of Heavy Metalsin the Old Yellow River Estuary, China

A sequential extraction procedure was applied to determine the concentration and fractionation characteristics of eight heavy metals (HMs) (Cu, Zn, Pb, Cd, Cr, Fe, Mn, and Ni) in a sediment core collected from the old Yellow River Estuary, China. The results revealed that the mean deposition rate of this sediment core, which spanned 87 yr (1925&ndash;2012), was approximately 0.5 cm yr&minus;1. The mean concentrations and ranges of HMs were Cu: 26.9 (18.3&ndash;38.5), Zn: 76.4 (51.0&ndash;107), Pb: 37.3 (17.8&ndash;53.8), Cd: 0.23 (0.20&ndash;0.27), Cr: 84.7 (45.5&ndash;116), Fe: 24,000 (16,500&ndash;31,700), Mn: 709 (388&ndash;1020), and Ni: 36.1 (24.8&ndash;47.2) mg kg-1 (dry weight). Six HMs (Cu, Zn, Cr, Cd, Fe, and Ni) were present in their highest proportion in the residual fraction; their lowest proportion was observed in the exchangeable fraction. Lead primarily existed in the oxidizable or residual fraction. Manganese was mainly presented in the exchangeable fraction. The risk assessment code results revealed that the sediments displayed a low risk for Cu, Zn, Pb, Cr, Cd, Fe, Mn, and Ni. The HMs Cu, Zn, Cr, Cd, Mn, and Ni displayed minor enrichment in the sediment core, whereas for Pb, moderate contamination enrichment was observed. Overall, an increase in I geo and total concentration of HMs occurred since 1925 and reached a maximum value around 1980, after which there was a larger fluctuation or decline until 2012. We also found that the degree of HM pollution during the 1976&ndash;1996 period was less serious than before 1976. All the sediment samples exceeded the effect range low (ERL) for Ni, whereas 56.1, 7.32, and 17.1% exceeded the ERL values for Cr, Cu, and Pb; no samples exceeded the ERL for Zn or Cd.</p

Synthesis, characterization and aging study of kaolinite-supported zero-valent iron nanoparticles and its application for Ni(II) adsorption

Kaolinite-supported zero-valent iron nanoparticles (kaolinite-nZVI) were prepared by a liquid-phase reduction under ambient atmosphere. The synthesized kaolinite-nZVI particles exist on the surface of clays or form a chain independently. A good dispersion of the swelling black sheer was observed to affix to the surface of kaolinate, and a complete core-shell structure may protect the iron oxide from more hydration. Synthesized nanoparticles were used to adsorb Ni(II) from aqueous solution. It was found that the adsorption of Ni(II) on kaolinite-nZVI was highly pH-dependent, following pseudo second-order kinetics model. The Langmuir isotherm model fits well with the Ni(II) adsorption on kaolinite-nZVI. Kaolinite-nZVI was more times useful, and showed a better adsorption capacity (9.24 mg/g) than nZVI (8.69 mg/g), kaolinite(1.61 mg/g) and ZVI (4.58 mg/g). These works promote the granulation, storage and transportation of nZVI, greatly enhancing the promising in environmental applications.</p

Investigation on Structural and Thermodynamic Characteristics of Perhydrous Bituminous Coal by Fourier Transform Infrared Spectroscopy and Thermogravimetry/Mass Spectrometry

Perhydrous bituminous coal has multi-purpose industrial applications determined mainly by its structural and thermodynamic parameters. The Huainan coalfield in China has a large reserve of perhydrous bituminous coal resource. However, little information is available concerning its physicochemical characteristics. In this study, perhydrous bituminous coal samples from number 13-1 and 8 coal seams were selected from 11 Huainan coal mines. The Fourier transform infrared spectroscopy (FTIR) showed that the chemical structures of perhydrous coal were characterized by relatively low aromaticity, implying that the process of hydrogen enrichment during coalification influenced the reactivity of aromatization and condensation of coal macromolecules. The thermogravimetry/mass spectrometry (TG/MS) experiments were conducted at different heating rates (10, 20, and 30 degrees C/min). At the heating rate of 20 degrees C/min, number 13-1 coal seam had similar pyrolysis characteristics as number 8 coal seam. Three pyrolysis stages could be divided at this heating rate, and the main pyrolysis temperature range is 300-600 degrees C. Variation in heating rates mainly affected the primary pyrolysis stage (450-550 degrees C) of perhydrous coals. With the increase of heating rates, the maximum weight loss rate of coal and the releasing rates of gaseous species increased. The second- and third-order reaction parameters fitted better representations of the non-isothermal pyrolysis processes of perhydrous coals from the Pan4 coal mine. The apparent activation energy was calculated with values ranging from 78 to 307 kJ/mol.</p

Influences of magmatic intrusion on the macromolecular and pore structures of coal: Evidences from Raman spectroscopy and atomic force microscopy

Magmatic intrusion into coal-bearing sequences can significantly affect the rank of the intruded coal and change the macromolecular and pore structures. Here, we use Raman microscope and Atomic force microscope (AFM) to obtain quantitative information on these transformations. Six coal samples of different ranks taken from a magmatic intrusion zone of Huainan Coalfield, China, were studied. The Raman spectra were fitted with a combination of 8 Lorentzian bands and 1 Gaussian band. We found that the macromolecular structures in coals of different ranks have significant relationships with Raman spectral parameters, particularly the band area ratios (I-D1/I-G, I-D2/I-G, I-D3/I-G, I-D4/I-G and I-G/I-All). With the increase of coal rank, I-D1/I-G, I-D2/I-G, I-D3/I-G and I-D4/I-G show trends of decreasing intensity, suggesting an enhanced orientation of aromatic hydrocarbons. Observations by Atomic force microscopy indicate that the pore parameters (e. g. amount, size, shape) are quite different for different ranks of coals. The pore size of low-rank bituminous coal is much larger than high-rank anthracite and pore abundance is higher in the former. In addition, there is also good correspondence between the surface topography of coal grains and coal rank.</p

Mercury-binding forms in coals and their geological provenances in coals of different types

Mercury (Hg) is an element of environmental and geological significance. Quantification of different Hg-binding forms is crucial to understand geological Hg provenances and associated geochemical processes during coal formation. In this study, seven coal samples were selected, according to coal rank (i.e., middle volatile bituminous, C-3; low volatile bituminous, C-2; anthracite, C-1), chemical anomalies (high S coal, IBC-105; high Cl coal, C22650) and sampling environment (fresh coal, LH; weathered coal LHW), to determine their Hg-binding forms using well-established sequential extraction procedures coupled with sink-float experiment. In the thermally metamorphosed samples C-1 and C-2, a comparative enrichment of total Hg relative to C-3 is observed. Silicate- and organic-bound Hg are the dominant Hg-binding forms in C-1, suggesting possible Hg sources from magma silicate and secondary Hg enrichment by adsorption. Sulfide- and organic-bound Hg are the most abundant Hg-binding forms in IBC-105, whereas only organic-bound Hg dominates in CC22650. Weathering processes are suggested to transform the abundant sulfide-bound Hg in LH to silicate- and organic-bound Hg in its weathering product LHW.</p

Synthesis and Characterization ofMontmorillonite-Supported Zero-ValentIron Nanoparticles with Application forPreconcentration of Zinc

Montmorillonite-supported zero-valent iron nanoparticles (nZVImontmorillonite) were prepared by liquid-phase reduction under ambient atmosphere. Transmission electron microscope images indicated that the presence of montmorillonite decreased the aggregation and the size of iron nanoparticles. A portion of the gaps in the supporting material was filled with nanoparticles. Irregular angular shaped shells were also observed. X-ray diffraction indicated that the reduction rate had a substantial effect on the morphology and size of nanoparticles. nZVI-montmorillonite showed higher adsorption capacity for Zn(II) (9.9038 mg/g) compared to nZVI (9.4190 mg/g), montmorillonite (1.8835 mg/g), and zero-valent iron powder (5.8568 mg/g). The material can be used for several repeated applications.</p

Distribution and fate of environmentally sensitive elements (arsenic, mercury, stibium and selenium) in coal-fired power plants at Huainan, Anhui, China

The present study has investigated the distribution of arsenic (As), mercury (Hg), stibium (Sb) and selenium (Se) in feed coal and its combustion by-products in two pulverized coal-fired power plants at Huainan city, Anhui province, China, both of which burned the bituminous coals. Experimental analysis of simultaneously sampled coal, bottom ash, fly ash and FGD products showed that the concentrations of As, Hg, Sb and Se in coal were in the ranges of typical Chinese power plants reported by others publications. Mercury was found to be the most volatile, whereas Sb was the least volatile. The overall material balances of As, Hg, Sb and Se were established based on the operation parameters of their respective boiler. The average removal efficiencies of As, Hg, Sb and Se by the ESP unit were 83%, 16%, 100%, and 72%, respectively, whereas those by the FGD process were 61%, 80%, 0% and 55%, respectively. The stack emission proportions of As, Hg and Se were 6%, 17% and 13%, respectively. And the total annual emissions of As, Hg and Se from two coal-fired power plants were estimated at 0.46 t, 0.04 t and 2.27 t, respectively.</p

Occurrence, Sources, and Potential Toxicity of PolycyclicAromatic Hydrocarbons in Surface Soils from the Yellow RiverDelta Natural Reserve, China

A total of 46 surface soil samples collected from the experimental area, buffer area, and core area of the Yellow River Delta Natural Reserve (YRDNR), China, and an adjacent area outside the reserve were analyzed for 23 PAHs including highly carcinogenic dibenzopyrene isomers. The total concentrations ranged from 87.2 to 319 ng/g for ∑23PAHs and 79.2 to 311 ng/g for ∑16PAHs with average concentrations of 133 and 119 ng/g, respectively. Pearson correlation analysis implied that the total polycyclic aromatic compound (PAH) concentrations had a significant positive correlation with the total organic carbon content on the condition that four sites with abnormal values were removed. Low molecular-weight 2- to 3-ring PAHs predominated in the present study. Source diagnostics based on PAHs isomer ratios, principal component analysis, and multiple linear regression suggested that petroleum contributed most to the PAH contamination in the YRDNR, whereas a potential toxicity assessment using BaPeq indicated that the four dibenzopyrenes were the major carcinogenic PAH contributors in the area under investigation, although their concentrations only represented a small proportion of the total PAH concentrations