Distributions, sources and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in subsurface water of urban old industrial relocation areas: A case study in Shenyang, China

Spatiotemporal distributions and ecological risk of polycyclic aromatic hydrocarbons in the surface seawater of Laizhou Bay, China

The spatial-temporal distribution, source, and potential ecological risk of polycyclic aromatic hydrocarbons (PAHs) in surface seawater from Laizhou Bay were investigated. The total PAH (ΣPAH) concentrations ranged from 277 to 4393 ng/L with an average of 1178 ng/L, thereby suggesting a relatively moderate to high PAH exposure level in Laizhou Bay in comparison to other bays in the world. The composition patterns and source apportionment results revealed that the coal, biomass burning, diesel emissions, and petroleum combustion as well as the combination of these processes were the dominant sources of PAHs in the surface water, which were closely associated with sail process and sewage effluents. The ecological risk assessment indicated that benzo(a)pyrene (BaP), phenanthrene (Phe), luoranthene (Flua), and naphthalene (Nap) would exist ecological risks in most of surface seawater sites, but the probabilistic risk assessment (PRA) results showed that the current level of risk is not as severe as the risk quotient (RQ) results revealed.

Spatiotemporal distribution, source apportionment and ecological risk assessment of PBDEs and PAHs in the Guanlan River from rapidly urbanizing areas of Shenzhen, China

In this study, nine congeners of polybrominated diphenyl ethers (PBDEs) and sixteen congeners of polycyclic aromatic hydrocarbons (PAHs) were measured in water samples to elucidate their spatial distribution, congener profiles, sources and ecological risks in the Guanlan River during both the dry season (DS) and the wet season (WS). The concentration of Σ₉PBDE ranged from 58.40 to 186.35 ng/L with an average of 115.72 ng/L in the DS, and from 8.20 to 37.80 ng/L with an average of 22.15 ng/L in the WS. Meanwhile, the concentration of Σ₁₆PAHs was ranged from 121.80 to 8371.70 ng/L with an average of 3271.18 ng/L in the DS and from 1.85 to 7124.25 ng/L with an average of 908.11 ng/L in the WS. The concentrations of PBDEs and PAHs in the DS were significantly higher than those in the WS, probably due to the dilution of the river during the rainy season. Moreover, the spatial distribution of pollutants revealed decreasing trend in the concentration from upstream to downstream and almost identical pattern was observed during both seasons. The source apportionment suggested that penta-BDE and to some extent octa-BDE commercial products were major sources of PBDEs in the study area. However, the sources of PAHs were mainly comprised of fossil fuels and biomass burning, followed by the petroleum products and their mixtures. The results of the ecological risk assessment indicated PBDEs contamination posed high ecological risks, while PAHs exhibited low or no ecological risks in the study area. Consistent with the environmental levels, the ecological risks of pollutants were relatively lower in the WS, compared to that in the DS. The results from this study would provide valuable baseline data and technical support for policy makers to protect the ecological environment of the Guanlan River.

Impact of secondary effluent from wastewater treatment plants on urban rivers: Polycyclic aromatic hydrocarbons and derivatives

The growing population in urban area impacted the water quality of the urban rivers receiving treated municipal wastewater. Polycyclic aromatic hydrocarbons (PAHs) and their derivatives (SPAHs) are corresponding to the population density. In this study, the concentrations of 16 PAHs and 17 SPAHs, including 4 methyl PAHs (MPAHs), 4 oxygenated PAHs and 9 chlorinated PAHs were investigated in the major urban rivers receiving the effluent from 5 major wastewater treatment plants (WWTPs) in the mega city Beijing. The concentrations of ΣSPAHs (307 ± 68 ng/L) were similar to ΣPAHs (321 ± 92 ng/L) in the total phase (aqueous + particulate) suggesting that SPAHs in the urban rivers should be taken into consideration. The lower concentrations of ΣPAHs and ΣMPAHs in this study than the wastewater receiving rivers and WWTPs effluent previously (2010-2013), as well as the lower concentration in the heating seasons than the non-heating season in the investigated year implied the reduction of coal combustion for heating and power generation in recent years. Although WWTPs effluent was theoretically the only source to the urban rivers in the investigated season, April and November, PAHs and SPAHs in most rivers were demonstrated to be originated from other unknown sources besides the WWTPs effluent. The reduction from the original source, coal combustion (33% and 30%), was more efficient than from the wastewater treatment upgrading (15%) for the reduction of PAHs and SPAHs in the urban rivers.

Polycyclic aromatic hydrocarbons (PAHs) in an urban river at mid and high latitudes: A case study in Siping, a traditional industrial city in Northeast China

The occurrence, spatial distribution, seasonal variation, sources, and ecological risks of polycyclic aromatic hydrocarbons (PAHs) in overlying water and surface sediments from Tiaozi River, which is an urban river running through the downtown of Siping City, a traditional industrial city of northeastern China, were investigated. The total PAH concentrations (ΣPAHs) in water varied from 473.5 to 2674.3 ng/L with a mean value of 1272.6 ng/L and ranged from 601.5 to 2906.3 ng/g with a mean value of 1534.4 ng/g in sediments. Both the individual and total PAH concentrations in water and sediments decreased from upstream to downstream, and the average ΣPAHs between the four seasons in water and sediments decreased in the following order of winter> autumn> spring> summer. The composition of the PAHs was characterized by an abundance of PAHs from 2 rings to 4 rings, and the predominant components were naphthalene, chrysene, and benzo(a)anthracene. The identification of the source indicated that coal combustion could be the main contributor to the PAHs. The equivalent toxic concentrations of benzo[a]pyrene in the water ranged from 11.5 to 33.1 ng/L, which were much higher than the concentration limit, suggesting that PAHs in the water could cause potential risks. The risk assessment of PAHs in sediments also showed that PAHs could cause negative effects on aquatic organisms in this river.

Biosurfactant-assisted phytoremediation of multi-contaminated industrial soil using sunflower (Helianthus annuus L.)

This study evaluated the use of commercial rhamnolipid biosurfactant supplementation in the phytoremediation of a soil via sunflower (Helianthus annuus L.) cultivation. The soil, obtained from an industrial area, was co-contaminated with heavy metals and petroleum hydrocarbons. The remediation tests were monitored for 90 days. The best results for removal of contaminants were obtained from the tests in which the sunflower plants were cultivated in soil with 4 mg kg^-1 of the rhamnolipid. Under these conditions, reductions of 58% and 48% were obtained in the total petroleum hydrocarbon (TPH) and polycyclic aromatic hydrocarbon (PAH) concentrations, respectively; reductions in the concentrations of the following metals were also achieved: Ni (41%), Cr (30%), Pb (29%), and Zn (20%). The PCR-DGGE analysis of soil samples collected before and after the treatments verified that the plant cultivation and biosurfactants supplementation had little effect on the structure of the dominant bacterial community in the soil. The results indicated that sunflower cultivation with the addition of a biosurfactant is a viable and efficient technology to treat soils co-contaminated with heavy metals and petroleum hydrocarbons.