Perfluorooctane sulfonate (PFOS) and other fluorochemicals in fish blood collected near the outfall of wastewater treatment plant (WWTP) in Beijing

Perfluorinated compounds (PFCs) were measured in zooplankton and five fish species collected from Gaobeidian Lake, which receives discharge from wastewater treatment plant (WWTP) in Beijing, China. The mean total PFCs in five fish were in the order: crucian carp > common carp > leather catfish > white semiknife carp > tilapia. Perfluorooctane sulfonate (PFOS) occurred at the greatest concentrations, with mean concentrations ranging from 5.74 to 64.2 ng/ml serum. Perfluorodecanoic acid (PFDA) was the second dominant PFC in fish samples except for common carp in which perfluorooctane sulfonamide (PFOSA) was dominant. A positive linear relationship (r² = 0.85, p < 0.05) was observed between ln PFOS concentrations (ln ng/ml) and trophic level (based on δ¹⁵N) if tilapia was excluded. The risk assessment showed that PFOS might not pose an immediate risk to fish in Gaobeidian Lake.     

Flows across high aspect ratio street canyons: Reynolds number independence revisited

The Reynolds number for flow in a street canyon, Re?=?U_refH/ν (where U_ref is a reference velocity, H the street canyon height, and ν the kinematic viscosity), cannot be matched between reduced-scale experiments and full-scale field measurements. This mismatch is often circumvented by satisfying the Re independence criterion, which states that above a critical Re (Re_c), the flow field remains invariant with Re. Re_c?=?11,000 is often adopted in reduced-scale experiments. In deep street canyons with height-to-width aspect ratio ≥?1.5, reduced-scale experiments have shown two recirculation vortices induced by the mean flows, but full-scale field measurements have observed only one vortex. We investigated this discrepancy by conducting water channel experiments with Re between 10⁴ and 10⁵ at three aspect ratios. The canyons with aspect ratio 1.0 have Re_c?=?11,000, the canyons with aspect ratio 1.5 have Re_c between 31,000 and 58,000, while the canyons with aspect ratio 2.0 have Re_c between 57,000 and 87,000. Therefore, the widely adopted Re_c?=?11,000 is not applicable for canyons with aspect ratio greater than 1.5. Our results also confirm that there is only one vortex in deep canyons at high Re. This single-vortex flow regime could change our fundamental understanding of deep canyons, which are often assumed to exhibit multiple-vortex flow regimes. Applications such as numerical model validation based on the multiple-vortex regime should be revisited. Our experimental data with Re up to 10⁵ could be used to validate numerical models at high Re.     

水源水中不同分子量区间有机物的分布及控制对策

通过超滤膜法研究了澳门水源水中不同分子量区间有机物的分布特性 .结果显示 :1)澳门水源水中总有机碳 (TOC)的主体有机物分子量在 10 0 0以下 ,传统工艺对这类水体的有机物去除效率较低 .2 )澳门水源水中可生物降解溶解性有机碳(BDOC)主要与分子量小于 10 ,0 0 0的有机物相关 .3)三种水源水中不同分子量区间BDOC TOC比率的变化也非常大 ,表明能有效控制TOC的水处理工艺未必能够导致相同的BDOC处理效果 ,所以不一定可以有效保证饮用水的生物稳定性 .4 )澳门水源水中有机物含量很低 ,不必增加其它工艺来控制水中有机物 ;如果在水源水质恶化的突发事件情况下 ,可以采用投加粉末活性炭的方法加以控制 .     

Determination of polybrominated diphenyl ethers in soil and sediment from an electronic waste recycling facility

In this study samples of ten species of fish were analyzed for concentrations of organochlorine pesticides, PCBs and heavy metals (Pb, Cd, and Cu). Fish were captured using electric fishing on ten sites along the Dr?me river (Rh?ne-Alpes region). Quantitative determination of the organochlorine and PCBs compounds was performed by gas chromatography-electron-capture detection (GC-ECD). The concentrations of heavy metals were determined by atomic absorption spectrophotometry. Samples contained detectable concentrations of lindane, PCBs, and heavy metals but at concentrations below the maximum residue limit (MRL). Non-parametric statistical analysis was performed to distinguish groups of sites with different levels of contamination. PCBs concentrations increased along the river with four groups of sites significantly different from each other. Cadmium concentrations were below the MRL. Lead contamination showed two groups significantly different and a repartition similar to PCBs. Copper contamination was correlated with the localization of vineyards. We assessed the potential effects of contamination the otter (Lutra lutra). The concentrations of all pollutants analyzed in fish sampled in this study are lower than the threshold values described in literature. The Dr?me river is relatively unpolluted river, and the establishment of otter populations should not be affected by pollution.     

The trophic linkage between zooplankton and benthic suspension feeders: direct evidence from analyses of bivalve faecal pellets

Using radiotracer (¹⁴C) and microscopic observation, we demonstrated that mussels (Mytilus edulis and Perna viridis) could be predators of mesozooplankton (rotifer Brachionus plicatilis). At radio-labelled rotifer densities of 0.1, 0.2, 0.5, 1.0 individual ml⁻¹, faecal pellets of mussels showed different degrees of radio signals and most of the faecal pellets were expelled 4 h after pulse feeding on rotifers. The maximum gut retention time (GRT) of ¹⁴C-labelled rotifers in the digestive diverticula did not o show any significant difference between the two mussel species or the different densities of rotifers, and the averaged GRT was 43.4±3.06 h (mean ± SE). At a rotifer density of 4.5 individual ml⁻¹, rotifer lorica pieces and rotifer bodies without eggs were found in faeces of M. edulis, while in the pseudofaeces, only complete rotifer bodies were found.     

Remediation of a nonachloro biphenyl congener with zero-valent iron in subcritical water

Dechlorination of a nonachloro biphenyl congener with zero-valent iron in water under high temperature and pressure was investigated over time. Temperature has the main influence on the speed of dechlorination. Determination of polychlorinated biphenyls (PCBs) according to the grade of chlorination was performed by gas chromatography with mass selective detection in single ion monitoring mode. Dechlorination results in a variety of lower chlorinated biphenyls. The level of chlorination decreases with time. The amount of PCB molecules decreases to one-third within 90 min at 250 degrees C and 100 atm. However, no increase of biphenyl could be detected over time. A first-order kinetic model fitted the data obtained.     

土壤电动修复中菲迁移的数值模拟

针对菲污染土壤修复建模的问题,通过对电动力学作用下菲污染土壤的迁移现象的室内模拟实验,确定了影响菲迁移的电渗流、电迁移、对流和弥散4个主要过程,建立了电动力学作用下菲在污染土壤中的迁移模型;运用COMSOL Multiphysics 5.3软件结合迁移模型的各项方程和选取的参数对菲的迁移过程进行了模拟计算。结果表明:当孔隙率分别为0.33、0.38、0.43和0.48时,菲的最大迁移率分别为31.89%、34.78%、37.97%和41.74%;当电压从0.5 V·cm~(-1)增加至2 V·cm~(-1)的过程中,电渗流通量增大,最大迁移率可达到44.35%;修复区域的浓度均呈"碗状"分布,模拟计算得到在中间靠近阳极区域的菲的浓度达到最小值2.14 mol·m~(-3),迁移率最大为38%。模拟计算的菲迁移分布结果与实验所得结果相吻合,证明该模型用于电动修复多环芳烃污染土壤的适用性。     

Determination of ozone in outdoor and indoor environments using nitrite-impregnated passive samplers followed by ion chromatography

An improved ion chromatographic (IC) method has been developed for the separation of nitrate in filter extracts in the presence of high concentrations of nitrite. This analytical method was successfully used for an indirect measurement of ozone (O3) in outdoor and indoor air, following its collection using a nitrite-impregnated passive sampler. The limit of detection and the limit of quantification, using the modified IC method, were 6 microg l(-1) (3sigma) and 20 microg l(-1) (10sigma), respectively. Improved detection limits and low baseline noise were obtained with the use of eluent generator and high-capacity ion exchange column. The optimized method was used for assessing O3 concentration in both indoor and outdoor environments of 28 child care centers (CCCs) located in different parts of Singapore. The O3 concentrations ranged from 0.1 to 11.95 parts per billion (ppb) in indoor and from 3.2 to 21.7 ppb in outdoor environments during the study period. It was found that, among the CCCs investigated in this study, air-conditioned CCCs and those located in close proximity to traffic emissions had significantly lower O3 concentrations indoors.