Mengchang He

Distributions of polycyclic aromatic hydrocarbons in the Daliao River Estuary of Liaodong Bay, Bohai Sea (China).

The distributions of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in the aqueous phase, suspended particulate matter (SPM), sediment, and pore water of the Daliao River Estuary in Liaodong Bay, Bohai Sea (China). Total PAH concentrations ranged from 139.16 to 1717.87ngL(-1) in surface water, from 226.57 to 1404.85ngL(-1) dry weight in SPM, from 276.26 to 1606.89ngg(-1) dry weight in sediments, and from 10.20 to 47.27microgL(-1) in pore water. PAH concentrations were at relatively moderate levels in water, SPM, sediment and pore water in comparison with those reported for other estuary and marine systems around the world. Sedimentary PAH concentrations decreased offshore owing to active deposition of laterally-transported river-borne particles. PCA analysis of the possible PAH source suggested petrogenic and pyrolytic PAH inputs in the studied region.

Adsorption of antimony onto iron oxyhydroxides: adsorption behavior and surface structure.

Antimony is detected in soil and water with elevated concentration due to a variety of industrial applications and mining activities. Though antimony is classified as a pollutant of priority interest by the United States Environmental Protection Agency (USEPA) and Europe Union (EU), very little is known about its environmental behavior and adsorption mechanism. In this study, the adsorption behaviors and surface structure of antimony (III/V) on iron oxides were investigated using batch adsorption techniques, surface complexation modeling (SCM), X-ray photon spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS). The adsorption isotherms and edges indicated that the affinity of Sb(V) and Sb(III) toward the iron oxides depended on the Sb species, solution pH, and the characteristics of iron oxides. Sb(V) adsorption was favored at acidic pH and decreased dramatically with increasing pH, while Sb(III) adsorption was constant over a broad pH range. When pH is higher than 7, Sb(III) adsorption by goethite and hydrous ferric oxide (HFO) was greater than Sb(V). EXAFS analysis indicated that the majority of Sb(III), either adsorbed onto HFO or co-precipitated by FeCl3, was oxidized into Sb(V) probably due to the involvement of O2 in the long duration of sample preservation. Only one Sb-Fe subshell was filtered in the EXAFS spectra of antimony adsorption onto HFO, with the coordination number of 1.0-1.9 attributed to bidentate mononuclear edge-sharing ((2)E) between Sb and HFO.

Distribution, partitioning and sources of polycyclic aromatic hydrocarbons in Daliao River water system in dry season, China.

Eighteen polycyclic aromatic hydrocarbons (PAHs) were analyzed in 29 surface water, 29 suspended particulate matter (SPM), 28 sediment, and 10 pore water samples from Daliao River water system in dry season. The total PAH concentration ranged from 570.2 to 2318.6 ng L(-1) in surface water, from 151.0 to 28483.8 ng L(-1) in SPM, from 102.9 to 3419.2 ng g(-1) in sediment and from 6.3 to 46.4 microg l(-1) in pore water. The concentration of dissolved PAHs was higher than that of particulate PAHs at many sites, but the opposite results were generally observed at the sites of wastewater discharge. The soluble level of PAHs was much higher in the pore water than in the water column. Generally, the water column of the polluted branch streams contained higher content of PAHs than their mainstream. The environmental behaviors and fates of PAHs were examined according to some physicochemical parameters such as pH, organic carbon, SPM content, water content and grain size in sediments. Results showed that organic carbon was the primary factor controlling the distribution of the PAHs in the Daliao River water system. Partitioning of PAHs between sediment solid phase and pore water phase was studied, and the relationship between logK(oc) and logK(ow) of PAHs on some sediments and the predicted values was compared. PAHs other than naphthalene and acenaphthylene would be accumulated largely in the sediment of the Dalaio River water system. The sources of PAHs were evaluated employing ratios of specific PAHs compounds and different wastewater discharge sources, indicating that combustion was the main source of PAHs input.

Aliphatic and polycyclic aromatic hydrocarbons in the Xihe River, an urban river in China's Shenyang City: distribution and risk assessment.

The characteristics of petroleum hydrocarbons and the risks they pose to the ecosystem were studied in the Xihe River, which is an urban river located in Shenyang, China. High levels of aliphatic hydrocarbons (AHc) and polycyclic aromatic hydrocarbons (PAHs) were observed in the river due to the discharge of wastewater from industrial and municipal facilities for a long period of time. High-molecular-weight hydrocarbons, including unresolved complex mixtures (UCM) of n-alkanes between n-C16 and n-C32 and of PAHs with four to six rings, were the dominant hydrocarbons in the river, particularly in suspended particulate matter (SPM) and sediments. The AHc was mainly from petrogenic sources, whereas PAHs was from both pyrolytic and petrogenic source inputs. Our results suggest that there is a high risk of toxicity for the soils and groundwater of the study area. The overall toxicity in the sediments can be described using the toxic equivalent (TEQ) of dibenzo[a,h]anthracene (DBA) based on benzo(a)pyrene (TEQ(BaP)) and dioxins (TEQ(TCDD)) toxic equivalent concentrations. The TEQ values for benzo(a)pyrene (TEQ(BaP)) and dioxins (TEQ(TCDD)) presented a consistent assessment of sediment PAHs.

Phosphorus sorption and fraction characteristics in the upper, middle and low reach sediments of the Daliao river systems, China

Stream sediments play an important role in the transport and storage of phosphorus in the stream ecosystems. This research investigated the sorption and fraction of P in the sediments of a long-term seriously contaminated river, the Daliao river system, using isotherm sorption and selective sequentially extraction tests. Results indicated that the total content of P in the sediments was 479-1202 mg kg(-1), depending on iron content in the sediments. The content of potential bioavailable P, including soluble and loosely bound P, Al bound P, Fe bound P, and reductant soluble P was only 10-20% of total P in the sediments of the Hun river and Taizi river, while it was 40-55% in the sediments of the Daliao river, the downstream of the river system. Equilibrium phosphorus concentration without net P sorption (EPC(0)) was from 0.05 to 0.54 mg L(-1), with an increasing trend from upstream to downstream, indicating increasingly release potential. On the other hand, the upstream sediment generally sorbed more P than the downstream sediment for each river at the same equilibrium P concentration. The binding energy constant of P on the strong sites of the sediments generally decreased from 2.24 to 2.65 L mg(-1) at upstream to 0.41 L mg(-1) at downstream or estuary, suggesting that the strong binding sites have been occupied and partly saturated by the phosphate added by point and diffuse sources along the river. On the other hand, molar ratio of Fe to TP contents in the sediments showed sorption capacity of the sediments to P might be under-saturated. The added or sorbed P by the isotherm test was primarily bound to Fe oxides and secondly to Al oxides. Long-term pollution of the river lead to the decrease of P sorption capacity of the river sediment and the increase of P release potential.

Temporal and spatial distribution of atmospheric antimony emission inventories from coal combustion in China

A multiple-year inventory of atmospheric antimony (Sb) emissions from coal combustion in China for the period of 1980-2007 has been calculated for the first time. Specifically, the emission inventories of Sb from 30 provinces and 4 economic sectors (thermal power, industry, residential use, and others) are evaluated and analyzed in detail. It shows that the total Sb emissions released from coal combustion in China have increased from 133.19 t in 1980 to 546.67 t in 2007, at an annually average growth rate of 5.4%. The antimony emissions are largely emitted by industrial sector and thermal power generation sector, contributing 53.6% and 26.9% of the totals, respectively. At provincial level, the distribution of Sb emissions shows significant variation. Between 2005 and 2007, provinces always rank at the top five largest Sb emissions are: Guizhou, Hunan, Hebei, Shandong, and Anhui.

Comparison of polycyclic aromatic hydrocarbons in sediments from the Songhuajiang River (China) during different sampling seasons

The Songhuajiang River watershed is the important industrial and foodstuff base in the northeast part of China. However, the increasing population, industrial and agricultural activities around the Songhuajiang River lead to the introduction of contaminants and the possibility of polluting the river. This investigation represents an extensive study of the spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in the sediment samples collected from the Songhuajing River in flood season (August, 2005) and icebound season (December, 2005) by using the gas chromatography-mass spectrometry (GC/MS) analyses. In flood season, the total PAHs concentrations in sediments ranged from 84.44 ng g−1 to 14938.73 ng g−1, with average concentration of 2430.37 ng g−1. In icebound season, the total PAHs concentrations in sediments ranged from 23.61 ng g−1 to 15310.25 ng g−1, with average concentration of 1825.60 ng g−1. Compared to the concentration of PAHs between central sediment and riverbank-exposed sediment at some stations, the concentration in exposed sediment was higher than that in the central sediment in the upstream of river. It was also observed that the concentration of PAHs in flood season was higher than that in icebound season. The level of PAHs in the sediments of Songhua River was higher in comparison with values reported from other river and marine systems in the world. The most contaminated sediment samples were found in the upstream area of Songhuajiang River located near Jilin petrochemical industrial company for both flood and icebound seasons. The 4–6 ring PAHs were dominated in sediments due to their higher persistence. There was positive correlation between total PAHs concentration in sediment samples and TOC or LOI (r = 0.62 and r = 0.58, P < 0.01, n = 31). The calculated ratio of selected PAH and principal component analysis (PCA) suggests the contamination source of PAHs were combined inputs of pyrolytic and petrogenic contamination, due to the discharge from municipal and industrial wastewater runoff and atmospheric fallout.

Comparative sorption of benzo[α]phrene to different humic acids and humin in sediments

Sediment/soil organic matter (SOM) is the predominant sorbents for hydrophobic organic compounds (HOCs). The identification and comparison of sorption characterization of HOCs by different organic matter fractions are essential to predict the fate and transport of HOCs in soils and sediments. The objectives of this paper are to compare the sorption of benzo[alpha]phrene (BaP) to the humic acid (HA) and humin (HM) extracted from different sediments. The HA and HM were extracted with 0.1M NaOH from five sediments in different areas in China, and their sorption isotherms for BaP were determined. All sorption isotherms were nonlinear and nonlinearity increased in the order HA<sediment<HM. BaP sorption capacities on the HA fractions were significantly related to their aliphaticity, but negatively correlated to aromatic carbon. However, more aromatic carbon in HM fractions can result in higher K(oc) values of BaP than HA. This implied the importance of both aliphatic and aromatic groups in BaP sorption. HM contributed to 54-92% of the total sorption depending on initial concentrations, clearly indicating the dominance of HM in BaP sorption by the sediments.

Contamination and ecological risk assessment of toxic trace elements in the Xi River, an urban river of Shenyang city, China.

The objectives of this study were to assess the enrichment, contamination, and ecological risk posed by toxic trace elements in the sediments of the Xi River in the industrialized city of Shenyang, China. Surface sediment and sediment core were collected; analyzed for toxic trace elements; and assessed with an index of geoaccumulation (Igeo), enrichment factor (EF) value, potential ecological risk factor (Er), ecological risk index (RI), and probable effect concentration quotient (PECQ). Elemental concentrations (milligram per kilogram) were 8.5–637.9 for As, 6.5–103.9 for Cd, 12.2–21.9 for Co, 90.6–516.0 for Cr, 258.1–1,791.5 for Cu, 2.6–19.0 for Hg, 70.5–174.5 for Ni, 126.9–1,405.8 for Pb, 3.7–260.0 for Sb, 38.4–100.4 for V, and 503–4,929 for Zn. The Igeo, EF, Er, and PECQ indices showed that the contamination of Cd and Hg was more serious than that of As, Cr, Cu, Ni, Pb, Sb, and Zn, whereas the presence of Co and V might be primarily from natural sources. The Igeo index for Cr and Ni might underestimate the degree of contamination, potentially as a result of high concentrations of these elements in the shale. The RI index was higher than 600, indicating a notably high ecological risk of sediment for the river. The average PECQ for As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn ranged from 1.4 to 4.1 for surface sediment and from 5.2 to 9.6 in the sediment cores, indicating a high potential for an adverse biological effect. It was concluded that the sediment in the Xi River was severely contaminated and should be remediated as a hazardous material.

Effect of structural variations on sorption and desorption of phenanthrene by sediment organic matter.

Sorption and desorption isotherms of phenanthrene (PHE) on sediment organic matter (SOM) prepared at different combustion temperature were studied to examine the impact of SOM structure on sorption and desorption. With the increase of combustion temperature from 0 to 400°C, the aromatic groups (-CC) in SOM samples increased, while the aliphatic groups (-CH, -CH(2)) and polar structures (-C-O, -OH) decreased. When the combustion temperature increased to 500°C, aliphatic structures, polar structures and most aromatic structures were burnt out, and the mineral materials were dominant in the sample. The increase of combustion temperature decrease the sorption isotherm nonlinearity index n value, and enhanced the adsorption capacity and desorption hysteresis for PHE on SOM. However, higher n value, lower sorption capacity and sorption irreversibility were presented in the sample treated at 500°C (T500). Positive correlations between single-point organic carbon-normalized distribution coefficient log K(oc) values and aromatic carbon (p<0.01) and negative correlations between log K(oc) values and aliphaticity or H/C ratios (p<0.05) were observed. There was a negative relation between hysteresis index (HI) value and aromatic carbon (p<0.01) and a negative trend of the sorption isotherm nonlinearity index n values and aromatic carbon (p<0.01). The above results indicated the dominance of aromatic structures in the sorption nonlinearity, sorption capacity and desorption hysteresis of PHE on SOM.