长江重点江段水体中多环芳烃及其衍生物的分布及健康风险

研究了长江攀枝花、宜宾、泸州、重庆、涪陵、三峡、岳阳、武汉、九江和南京共计10个重点江段枯水期和丰水期表层水中19种多环芳烃(PAHs)及其15种衍生物(SPAHs)的分布和来源,评估了长江PAHs类污染的健康风险及时空差异.结果表明,长江表层水中∑PAHs、∑SPAHs平均浓度分别为(147.3±59.8)、(73.2±29.7) ng·L^-1,检出率分别为82.9%、69.5%,其中2~3环(S)PAHs所占比例为79%.在SPAHs中,∑NPAHs(硝基取代PAHs)、∑MPAHs(甲基取代PAHs)、∑OPAHs(氧化PAHs)的平均浓度分别为(27.0±4.5)、(24.7±15.5)、(17.1±11.9) ng·L^-1.根据分子比值法及主成分分析可知,长江重点江段PAHs主要来源于生物质、化石及液体燃料燃烧,SPAHs主要来源于燃烧源和光化学转化,SPAHs及PAHs通过大气沉降汇入水体.采用毒性当量因子浓度计算对长江重点江段PAHs进行健康风险评估,结果表明在枯水期具有致癌性PAHs的∑TEQ_BaP值(苯并芘毒性当量)较高,其中岳阳、武汉江段的BaP毒性当量浓度高于我国地表水规定阈值,应当高度重视长江流域PAHs在枯水期引起的健康风险.     

Polycyclic aromatic hydrocarbons (PAHs) in a sediment core from Lake Taihu and their associations with sedimentary organic matter

Sediment core is the recorder of polycyclic aromatic hydrocarbon (PAH) pollutions and the associated sedimentary organic matter (SOM), acting as crucial supports for pollution control and environmental management. Here, the sedimentary records of PAHs and SOM in the past century in Lake Taihu, China, were reconstructed from a 50-cm sediment core. On the one hand, the presence of PAHs ranged from 8.99 to 199.2 ng/g. Vertically, PAHs declined with the depth increased, and the sedimentation history of PAHs was divided into two stages with a discontinuity at 20 cm depth. In composition, PAHs in the sediment core were dominated by three-ring PAHs (44.6% ± 9.1%, mean ± standard deviation), and were followed by four-ring (27.0% ± 3.3%), and five-ring (12.1% ± 4.0%) PAHs. In toxicity assessment, the sedimentary records of benzo[a]pyrene-based toxic equivalency were well described by an exponential model with R-square of 0.95, and the environmental background toxic value was identified as 1.62 ng/g. On the other hand, different components of SOM were successfully identified by n-alkane markers (p < 0.01) and the variations of SOM were well explained (84.6%). A discontinuity of SOM was recognized at 22 cm depth. Association study showed that the sedimentary PAHs were associated with both anthropogenic and biogenic SOM (p < 0.05) with explained variances for most individual PAHs of 60%. It indicated the vertical distributions of PAHs were driven by sedimentary SOM. Therefore, environmental processes such as biogenic factors should attract more attentions as well as PAH emissions to reduce the impacts of PAHs.     

Diffusive gradients in thin films (DGT) probe for effectively sampling of per- and polyfluoroalkyl substances in waters and sediments

The passive sampling technique, diffusive gradients in thin films (DGT) has attracted increasing interests as an in-situ sampler for organic contaminants including per- and polyfluoroalkyl substances (PFAS). However, its effectiveness has been questioned because of the small effective sampling area (3.1 cm²). In this study, we developed a DGT probe for rapid sampling of eight PFAS in waters and applied it to a water-sediment system. It has a much larger sampling area (27 cm²) and as a result lower method quantification limits (0.15 – 0.21 ng/L for one-day deployment and 0.02 – 0.03 ng/L for one-week deployment) and much higher (by > 10 factors) sampling rate (100 mL/day) compared to the standard DGT (piston configuration). The sampler could linearly accumulate PFAS from wastewater, was sensitive enough even for a 24 hr deployment with performance comparable to grab sampling (500 mL). The DGT probe provided homogeneous sampling performance along the large exposure area. The use of the probe to investigate distributions of dissolved PFAS around the sediment-water interface was demonstrated. This work, for the first time, demonstrated that the DGT probe is a promising monitoring tool for trace levels of PFAS and a research tool for studying their distribution, migration, and fate in aquatic environments including the sediment-water interface.     

基于原位被动采样技术研究巢湖沉积物和水体中PAHs的垂直分布及其界面交换

沉积物-水体界面处分子扩散是污染物的一个重要地球化学过程,也是判断沉积物是否为上层水体中污染物汇或源的主要依据.本研究利用低密度聚乙烯膜(LDPE)为吸附相的原位被动采样器,同步确定了巢湖西半湖南淝河入湖口处不同深度的上层水体和沉积物孔隙水中13种多环芳烃(PAHs)浓度,并计算了它们在沉积物-水体界面的分子扩散通量.结果表明,3种性能参考化合物(PRCs)在上层水体中的解析速率较沉积物孔隙水中大,相应地,水体中LDPE膜对PAHs的吸附速率高于沉积物孔隙水.水体中13种PAHs总浓度(130～250 ng·L~(-1))低于沉积物孔隙水(180～253 ng·L~(-1)),且均以低环PAHs为主.2～3环PAHs浓度在上层水体中无明显的垂直变化,但4～6环PAHs浓度呈现随深度增加而降低的趋势.沉积物孔隙水中PAHs浓度的垂直变化规律反映了历史强排放过程.研究区域PAHs在沉积物-水体界面的交换通量变化范围为-384～1445 ng·m~(-2)·d~(-1),除Flu和Pyr外,其它PAHs均从沉积物向水体释放,反映了底部沉积物是上层水体中PAHs的重要二次污染源.     

Source apportionment of polycyclic aromatic hydrocarbons (PAHs) in a sediment core from Lake Dagze Co, Tibetan Plateau, China: Comparison of three receptor models

Receptor models are a useful tool for identifying sources of polycyclic aromatic hydrocarbons (PAHs) in multiple environmental media. In this study, three different receptor models (including the principal component analysis-multiple linear regression (PCA-MLR), positive matrix factorization (PMF), and Unmix models) were used to apportion the sources of 16 priority PAHs in a sediment core of Lake Dagze Co. The ∑PAHs (sum of all 16 measured PAHs) concentrations ranged from 51.89 to 132.82 ng/g with an average of 80.39 ng/g. The ∑PAHs were dominated by 2-3 ring PAHs, accounting for 80.12% on average, thereby indicating that they mainly originated from biomass and coal combustion and/or from long-range atmospheric transportation. The three models produced consistent source apportionment results. The greatest contributor to ∑PAHs was biomass combustion, followed by coal combustion, vehicle emissions, and petrogenic sources. Moreover, the temporal variation of the common sources was well-correlated among models. The multi-method comparison and evaluation results showed that all three models were useful tools for source apportionment of PAHs, with the PMF model providing better results than the PCA-MLR and Unmix models. The temporal trends of factor contributions were verified by PAHs with different ring numbers. Significant correlations were found between the simulated concentrations of each source factor and the PAHs with different ring numbers (P<0.01), except for the petrogenic source identified by the Unmix model (P>0.05). This study can provide useful information for further investigation of source apportionment of PAHs in the sediment cores.     

Functional groups assisted-photoinduced electron transfer-mediated highly fluorescent metal-organic framework quantum dot composite for selective detection of mercury (II) in water

The presence of toxic mercury (II) in water is an ever-growing problem on earth that has various harmful effect on human health and aquatic living organisms. Therefore, detection of mercury (II) in water is very much crucial and several researches are going on in this topic. Metal-organic frameworks (MOFs) are considered as an effective device for sensing of toxic heavy metal ions in water. The tunable functionalities with large surface area of highly semiconducting MOFs enhance its activity towards fluorescence sensing. In this study, we are reporting one highly selective and sensitive luminescent sensor for the detection of mercury (II) in water. A series of binary MOF composites were synthesized using in-situ solvothermal synthetic technique for fluorescence sensing of Hg²⁺ in water. The well-distributed graphitic carbon nitride quantum dots on porous zirconium-based MOF improve Hg²⁺ sensing activity in water owing to their great electronic and optical properties. The binary MOF composite (2) i.e., the sensor exhibited excellent limit of detection (LOD) value of 2.4 nmol/L for Hg²⁺. The sensor also exhibited excellent performance for mercury (II) detection in real water samples. The characterizations of the synthesized materials were done using various spectroscopic techniques and the fluorescence sensing mechanism was studied.     

UV/H2O2 oxidation of tri(2-chloroethyl) phosphate: Intermediate products, degradation pathway and toxicity evaluation

Tri(2-chloroethyl) phosphate(TCEP) with the initial concentration of 5 mg/L was degraded by UV/H₂O₂ oxidation process. The removal rate of TCEP in the UV/H₂O₂ system was 89.1% with the production of Cl-and PO₄^3- of 0.23 and 0.64 mg/L. The removal rate of total organic carbon of the reaction was 48.8% and the pH reached 3.3 after the reaction. The oxidative degradation process of TCEP in the UV/H₂O₂ system ...     

Highly inhibited transport of dissolved thallium(I) in manganese oxide-coated sand: Chemical condition effects and retention mechanisms

Thallium contamination in water can cause great danger to the environment. In this study, we synthesized manganese oxide-coated sand (MOCS) and investigated the transport and retention behaviors of Tl(I) in MOCS under different conditions. Characterization methods combined with a two-site nonequilibrium transport model were applied to explore the retention mechanisms. The results showed that Tl(I) mobility was strongly inhibited in MOCS media, and the retention capacity calculated from the fitted model was 510.41 mg/g under neutral conditions. The retention process included adsorption and oxidative precipitation by the manganese oxides coated on the sand surface. Cotransport with the same concentration of Mn(II) led to halving Tl(I) retention due to competition for reactive sites. Enhanced Tl(I) retention was observed under alkaline conditions, as increasing pH promoted electronegativity on the media surface. Moreover, the competitive cation Ca²⁺ significantly weakened Tl(I) retention by occupying adsorption sites. These findings provide new insights into understanding Tl(I) transport behavior in water-saturated porous media and suggest that manganese oxide-coated sand can be a cost-effective filter media for treating Tl-contaminated water.