Ice phase as an important factor on the seasonal variation of polycyclic aromatic hydrocarbons in the Tumen River, Northeastern of China

Multimedia distribution, dynamics, and seasonal variation of PAHs in Songhua wetland: Implications for ice-influenced conditions

The knowledge of polycyclic aromatic hydrocarbons (PAHs) in wetlands remains limited. There is a research need for the dynamics between interfaces of multimedia when ice is present in this fragile ecosystem. In this study, sediment, open-water, sub-ice water, and ice samples were collected from the Songhua wetland to study the behaviors of PAHs with and without influences from ice. The concentration of all individual PAHs in sub-ice water (370-1100 ng/L) were higher than the open-water collected from non-ice-covered seasons (50-250 ng/L). Enrichment of PAHs in the ice of wetland was found, particularly for high-molecular-weight PAHs (HMW). This could be attributed to the relatively lower polarity of hydrocarbons compounds, making them more likely to remain in the ice layer during freezing. Source assessments reveal common sources for sub-ice water and ice, which differ from those in the open water in non-ice-covered seasons. This difference is primarily attributed to heating activities in the Harbin during winter. The average percentage contributions were 79% for sub-ice water and 36% for ice related to vehicle exhausts and coal combustion. Additionally, wood burning contributed 25% to sub-ice water and 62% to ice. Sediment in the wetland was found to serve as a final deposit particularly for heavier PAHs, especially those with 6 rings. Sediment also has the potential to act as a source for the secondary emission of low-molecular-weight PAHs (LMW) congeners into the water. PAHs in wetland displayed low ecological risk, while HMW PAHs with relative higher ecological risk is recommended to be further monitored.

Occurrence, distribution, and potential ecological risks of antibiotics in a seasonal freeze-thaw basin

Antibiotics have gained increasing attention as pharmaceuticals widely existing in human society. Under low temperature conditions, antibiotics tend to have higher environmental persistence, which poses a potential threat to ecological environment, but research on antibiotics in low-temperature basins is still lacking. Therefore, for investigating occurrence, spatio-temporal distributions, and ecological risks of antibiotics in a seasonal freeze-thaw basin, rivers in Tumen River basin were selected and sampled, including 25 samples during the river-freezing season and 27 samples during the non-freezing season. Overall, climate characteristics of different latitudes and renewal frequency of antibiotics are important factors that lead to diversity of antibiotics in basins. Eleven target antibiotics were detected and their average concentrations during the river-freezing season (0.83-27.5 ng L-1) were lower than that during the non-freezing season (2.80-45.30 ng L-1), severely impacted by river flow, ice sealed-melting, and local feeding practices. In addition, total antibiotic concentrations are usually highest in downstream areas of human settlements, receiving input from husbandry and sewage, respectively. Through ecological risk assessment, norfloxacin and amoxicillin posed high risks to algae, which were identified as high-risk pollutants in basin.

Spatial distribution and ecological risks of polycyclic aromatic hydrocarbons in sea ice and seawater from northern Liaodong Bay, China

To better understand the spatial distribution and ecological risks of polycyclic aromatic hydrocarbons especially in low latitude coastal productive areas, PAHs in sea ice were examined for the first time in northern Liaodong bay of China in December 2020. Results showed ΣPAHs were dominated by 2- and 3-ring, with the mean concentration of 241.9 ng L^-1 and 202.8 ng L^-1 in sea ice and seawater, respectively, suggesting a moderate ecological risk based on Risk Quotients assessment. Ice enrichment factors were greater than 1 at 82% of the sampling sites, reflecting enrichment of PAHs in sea ice. The characteristic compounds ratios demonstrated PAHs mainly derived from petrogenic sources, while combustion was another crucial source for PAHs in sea ice via atmospheric deposition. This helps to better elucidate pollution status, potential sources and risk assessment of PAHs in productive coastal oceans especially during ice-covered period for contamination control and environmental management.

Polycyclic Aromatic Hydrocarbons in the Estuaries of Two Rivers of the Sea of Japan

The seasonal polycyclic aromatic hydrocarbon (PAH) variability was studied in the estuaries of the Partizanskaya River and the Tumen River, the largest transboundary river of the Sea of Japan. The PAH levels were generally low over the year; however, the PAH concentrations increased according to one of two seasonal trends, which were either an increase in PAHs during the cold period, influenced by heating, or a PAH enrichment during the wet period due to higher run-off inputs. The major PAH source was the combustion of fossil fuels and biomass, but a minor input of petrogenic PAHs in some seasons was observed. Higher PAH concentrations were observed in fresh and brackish water compared to the saline waters in the Tumen River estuary, while the PAH concentrations in both types of water were similar in the Partizanskaya River estuary, suggesting different pathways of PAH input into the estuaries. The annual riverine PAH mass flux amounted to 0.028 t/year and 2.5 t/year for the Partizanskaya River and the Tumen River, respectively. The riverine PAH contribution to the coastal water of the Sea of Japan depends on the river discharge rather than the PAH level in the river water.

Distribution and Photochemistry of Polycyclic Aromatic Hydrocarbons in the Baotou Section of the Yellow River During Winter

In this study, ice and water samples were collected from seven sites along the Baotou section of the Yellow River during winter 2013. Total polycyclic aromatic hydrocarbon (PAH) concentrations in the ice and in the water under the ice ranged from 21.3 to 59.4 ng L(-1), and from 38.3 to 222.4 ng L(-1), respectively. The average concentration in water under the ice was approximately 2.5 times greater than the average concentration in the ice phase. Four-ring PAHs dominated and accounted for 68.2 and 76.0 % of the total PAHs in ice and water, respectively. PAH concentrations were highest at sampling site S2 and were also relatively high at sites S4 and S5. PAH sources in ice and in water under the ice were similar. Three components were selected to represent the coal-combustion sources of PAHs. Because it was the main pollutant, and its concentrations were the highest, we examined the photodegradation behavior of fluoranthene and investigated the effects of light-sensitive materials (H2O2, acetone, and sediment) on fluoranthene photodegradation in the ice phase. Results showed that low H2O2 concentrations promoted photoconversion in the initial stage of the reaction and that degradation rates decreased later in the reaction. Likewise, high H2O2 concentrations promoted photoconversion. As acetone concentrations increased, the rates of fluoranthene-degradation decreased. Sediments may also have decreased the degradation rate of fluoranthene.

Long-range atmospheric transport and the distribution of polycyclic aromatic hydrocarbons in Changbai Mountain

The Changbai (also known as "Baekdu") Mountain, on the border between China and North Korea, is the highest mountain (2750 m) in northeastern China. Recently, this mountain region has experienced a dramatic increase in air pollution, not only because of increasing volumes of tourism-derived traffic but also because of the long-range transport of polluted westerly winds passing through major industrial and urban cities in the eastern region of China. To assess the relative importance of the two sources of pollution, 16 polycyclic aromatic hydrocarbons (PAHs) as model substances were determined in the mountain soil. A total of 32 soil samples were collected from different sides of the mountain at different latitudes between July and August of 2009. The ∑PAH concentrations were within the range 38.5-190.1 ng g(-1) on the northern side, 117.7-443.6 ng g(-1) on the southern side, and 75.3-437.3 ng g(-1) on the western side. A progressive increase in the level of ∑PAHs with latitude was observed on the southern and western sides that face the westerly wind with abundant precipitation. However, a similar concentration gradient was not observed on the northern side that receives less rain and is on the leeward direction of the wind. The high-molecular-weight PAH compounds were predominant in the soils on the southern and western sides, while low-molecular-weight PAHs dominated the northern side soils. These findings show that the distribution of PAHs in the mountain soil is strongly influenced by the atmospheric long-range transport and cold trapping.

Source contributions and spatiotemporal characteristics of PAHs in sediments: Using three-way source apportionment approach

Polycyclic aromatic hydrocarbon (PAHs) were measured in sediments from 29 sites throughout Taihu Lake in China during 2 seasons to investigate spatiotemporal characteristics and source contributions using a 3-way source apportionment approach to positive matrix factorization (PMF3). Seasonal and spatial variations of levels and toxicity suggested higher individual carcinogenic PAH concentrations and toxic equivalent quantity (TEQ) in the flooding season. Three-way PAHs dataset (PAH species, spatial variability, and seasonal variability) was analyzed by PMF3, and its results were compared with a widely used 2-way model (PMF2). Consistent results were observed: vehicular emission was the most important contributor (67.08% by PMF2 and 61.83% by PMF3 for the flooding season; 54.21% by PMF2 and 52.94% by PMF3 for dry season), followed by coal combustion and wood combustion in both seasons. The PMF-cluster analysis was employed to investigate spatial variability of source contributions. Findings can introduce the 3-way approach to apportion sources of PAHs and other persistent organic pollutants (POPs) in sediments, offering the advantage of accounting for information on 3-way datasets.