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The selective capture of copper from strongly acidic solutions is of vital importance from the perspective of sustainable development and environmental protection. Metal organic frameworks (MOFs) have attracted the interest of many scholars for adsorption due to their fascinating physicochemical characteristics, including adjustable structure, strong stability and porosity. Herein, pz-UiO-66 containing a pyrazine structure is successfully synthesized for the efficient separation of copper from strongly acidic conditions. Selective copper removal at low pH values is accomplished by using this material that is not available in previously reported metal—organic frameworks. Furthermore, the material exhibits excellent adsorption capacity, with a theoretical maximum copper uptake of 247 mg/g. As proven by XPS and FT-IR analysis, the coordination of pyrazine nitrogen atoms with copper ions is the dominant adsorption mechanism of copper by pz-UiO-66. This work provides an opportunity for efficient and selective copper removal under strongly acidic conditions, and promises extensive application prospects for the removal of copper in the treatment for acid metallurgical wastewater. [ABSTRACT FROM AUTHOR]

The concentration and composition of nutrients, such as N, P, and Si, respond to biogeochemical processes and in turn, impact the phytoplanktons' community structure and primary production. In this study, historical data was systematically analyzed to identify long-term variations in nutrient trends, red tide frequency, phytoplankton community abundance, and dominant species succession in the southern Yellow Sea (SYS). Results showed that N/P concentration ratios dramatically increased as a function of increasing dissolved inorganic nitrogen concentrations, and Si/N concentration ratios were generally larger than 1, indicating that N limitation morphed to P limitation and potentially to Si limitation, which impacted the phytoplankton community. Furthermore, inter-annual trends over the past 50 years show that phytoplankton community abundance has been higher in spring and summer, relative to autumn and winter. Moreover, with respect to red tide frequency, diatom abundance gradually decreased, while that of dinoflagellates gradually increased. Dominant species succession showed that the phytoplankton community exhibited an evident tendency to transform from diatoms to dinoflagellates. These research results clearly depict the presence of an important correlation between the phytoplankton community and nutrient structure in the SYS. [ABSTRACT FROM AUTHOR]

Parent and alkylated polycyclic aromatic hydrocarbons (alkyl-PAHs), which are a class of important toxic components of crude oil especially in the marine environment, exhibit adverse effects on aquatic life and potentially pose a human health risk. However, the lack of chronic toxicity data is one of the hindrances for alkyl-PAHs when assessing their ecological risks. In this study, predicted no-effect concentrations (PNECs) in seawater and marine sediment for ten parent- and alkyl-PAHs were derived by applying species sensitivity distributions (SSDs) and quantitative structure-activity relationships (QSARs). The local area, Dalian Bay, where an oil-spilled accident happened in 2010, was chosen as a case site to assess ecological risks for ten PAHs in surface seawaters and marine sediments. Their PNECs in seawater and sediment for protecting aquatic organisms in marine ecosystems were calculated and recommended in the range of 0.012–2.79 μg/L and 48.2–1 337 ng/g (dry weight), respectively. Overall, the derived PNECs for the studied PAHs in seawater and marine sediment were comparable to those obtained by classical methods. Risk quotient results indicate low ecological risks to ecosystems for ten parent- and alkyl-PAHs in surface seawaters and surface sediments from the Dalian Bay. These findings provide a first insight into the PNECs and ecological risks of alkyl-PAHs, emphasizing the role of the computational toxicology in ecological risk assessments. The use of QSARs has been identified as a valuable tool for preliminarily assessing ecological risks of emerging pollutants, being more predictable of real exposure scenarios for risk assessment purposes. [ABSTRACT FROM AUTHOR]

Antibiotics are ubiquitous pollutants in aquatic systems and can exist as different dissociated species depending on the water pH. New knowledge of their multivariate photochemical behavior (i.e., the photobehavior of different ionized forms) is needed to improve our understanding on the fate and possible remediation of these pharmaceuticals in surface and waste waters. In this study, the photochemical degradation of aqueous tetracycline (TC) and its dissociated forms (TCH20, TCH−, and TC2−) was investigated. Simulated sunlight experiments and matrix calculations indicated that the three dissociated species had dissimilar photolytic kinetics and photooxidation reactivities. TC2− photodegraded the fastest due to apparent photolysis with a kinetic constant of 0.938 ± 0.021 min−1, followed by TCH− (0.020 ± 0.005 min−1) and TCH20 (0.012 ± 0.001 min−1), whereas TCH− was found to be the most highly reactive toward •OH (105.78 ± 3.40 M−1 s−1), and TC2− reacted the fastest with 1O2 (344.96 ± 45.07 M−1 s−1). Water with relatively high pH (e.g., ~ 8-9) favors the dissociated forms of TCH− and TC2− which are most susceptible to photochemical loss processes compared to neutral TC. The calculated corresponding environmental half-lives (t1/2,E) in sunlit surface waters ranged from 0.05 h for pH = 9 in midsummer to 3.68 h for pH = 6 in midwinter at 45° N latitude. The process was dominated by apparent photolysis (especially in summer, 62-91%), followed by 1O2 and •OH oxidation. Adjusting the pH to slightly alkaline conditions prior to UV or solar UV light treatment may be an effective way of enhancing the photochemical removal of TC from contaminated water.Aqueous multiple photochemical behavior of dissociated tetracycline (TCH20, TCH−, and TC2−) is first comprehensively reported on revealing the phototransformation kinetics and implications for the fate in surface waters. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) were measured in atmospheric samples collected from the North Pacific to the Arctic Ocean between July and September 2012 to study the atmospheric concentration characteristics of PCBs and their gas/particle partitioning. The mean concentration of 26 PCBs (vapor plus particulate phase) (ΣPCBs) was 19.116 pg/m with a standard deviation of 13.833 pg/m. Three most abundant congeners were CB-28, −52 and −77, accounting for 43.0% to ΣPCBs. The predominance of vapor PCBs (79.0% to ΣPCBs) in the atmosphere was observed. ΣPCBs were negative correlated with the latitudes and inverse of the absolute temperature (1/ T). The significant correlation for most congeners was also observed between the logarithm of gas/particle partition coefficient (log K) and 1/ T. Shallower slopes (from −0.15 to −0.46, average −0.27) were measured from the regression of the logarithm of sub-cooled liquid vapor pressures (log p) and log K for all samples. The difference of the slopes and intercepts among samples was insignificant ( p>0.1), implying adsorption and/or absorption processes and the aerosol composition did not differ significantly among different samples. By comparing three models, the J-P adsorption model, the octanol/air partition coefficient ( K) based model and the soot-air model, the gas/particle partitioning of PCBs in the Arctic atmosphere was simulated more precisely by the soot-air model, and the adsorption onto elemental carbon is more sensitive than the absorption into organic matters of aerosols, especially for low-chlorinated PCB congeners. [ABSTRACT FROM AUTHOR]

Predicted no-effect concentration (PNEC) is often used in ecological risk assessment to determine low-risk concentrations for chemicals. In the present study, native marine species were selected for toxicity testing. The PNECs for three polycyclic aromatic hydrocarbons (PAHs), specifically phenanthrene (Phe), pyrene (Pyr), and benzo[ a]pyrene (BaP), were derived from chronic and acute toxicity data with log-normal statistical methods. The achieved PNECs for Phe, Pyr, and BaP were 2.33, 1.09, and 0.011 μg/L, respectively. In Jinzhou Bay and the Shuangtaizi River Estuary of Liaodong Bay in the Bohai Sea, China, the surface water concentrations of the three PAHs were analyzed by gas chromatography-mass spectrometry. Based on two probabilistic ecological risk assessment (PERA) methods, namely probabilistic risk quotient and joint probability curve, the potential risk of Phe, Pyr, and BaP in Jinzhou Bay and Shuangtaizi River Estuary was assessed. The same order of ecological risk (BaP > Phe > Pyr) was found by both models. Our study considered regional characteristics of marine biota during the calculation of PNECs, and the PERA methods provided probabilities of potential ecological risks of chemicals. Within the study area, further research on BaP is required due to its high potential ecological risk. [ABSTRACT FROM AUTHOR]

Samples of gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs) were collected at three sampling stations (Xiaomai Island, Laohutan, and Zhangzi Island) in the north Yellow Sea, China during November 2008 and September 2009 to study their atmospheric transport potential and the gas/particle distributions. The composition of PAHs was dominated by gaseous compounds. The percentages of the particle-phase PAHs to the total concentrations were found to be higher during the heating period than the non-heating period. The ratios of naphthalene and acenaphthene to phenanthrene, chrysene and dibenzo( a, h)anthracene showed an increasing trend from Xiaomai Island to Zhangzi Island, which can be called as the local atmospheric distillation of PAHs. Gas/particle partitioning coefficients ( K) and their relationship with the sub-cooled liquid vapor pressures ( pº) of PAHs were investigated. The regressions of log K versus log pº gave significant correlations for all samples of the three sites with r values in the range 0.56-0.66 ( p < 0.01). Both Junge-Pankow adsorption model and octanol-air partition coefficient absorption model tended to underestimate the sorption for most PAHs, but the absorption model appeared to be more suitable for predicting the particle fraction of PAHs than the Junge-Pankow model. [ABSTRACT FROM AUTHOR]

Dioxin-like polychlorinated biphenyls (PCBs) are a class of toxic and persistent chemicals that are often found in the environment. The determination of dioxin-like PCBs in Fildes Peninsula, Antarctica, is reported in this paper. Dioxin-like PCBs were widely distributed in Antarctic soil and moss with concentration of 2.23-27.2 pg/g in soil and 10.4-812 pg/g in moss. The highest concentrations were found in the Ardley Island area and the lowest concentrations on the west coast. The contribution of PCB-118 to the ΣPCBs ranged from 36.0% to 69.6% in soil, and 17.2% to 43.4% in moss. The congener specific patterns in soil and moss were similar. Long-range atmospheric transport is thought to be the main source of PCBs detected on King George Island. The ΣPCBs toxic equivalent (TEQ) in soil was 0.400×10 to 516×10 pg (TEQ)/g with a mean value of 147×10 pg (TEQ)/g. PCB-126 had the largest contribution (81.1%) to the ΣPCBs TEQ in soil. The ΣPCBs TEQ in moss ranged from 2.90×10 to 1.19 pg/g with a mean value of 0.482 pg/g. PCB-126 was also the largest contributor (91.4%) to the ΣPCBs TEQ in moss. The mean TEQ in moss was about 40 times that in soil. [ABSTRACT FROM AUTHOR]

Three extraction techniques have been recently used for the quantitative extraction of semi-volatile organic pollutants in sediments, i.e. accelerated solvent extraction (ASE), microwave assisted extraction (MAE) and ultrasonic assisted extraction (UAE). However, their extraction efficiencies have rarely been quantitatively compared using rigorous mathematical methods. In this paper, one-way analysis of variance (ANOVA) was employed to evaluate the performance of ASE, MAE and UAE in the overall extraction of PCBs, DDTs and HCHs by analysis of their recoveries from the Standard Reference Material IAEA-417, a sediment sample certified by many international laboratories. Conclusions were drawn at a significance level of P ≤ 0.05. No significant differences were found among the mean values for method recoveries using ASE, MAE and UAE. The mean values for real recoveries using ASE and MAE were nearly identical, but the real recovery using UAE was much lower. The concentrations of all PCBs, DDTs and HCHs except for CB52 and o,p′-DDT using UAE were the lowest. Comparing the results obtained using ASE with MAE, the concentrations of CB28, CB52, CB138, α-HCH, β-HCH, p,p′-DDE and p,p′-DDD were nearly identical, while the concentrations of other compounds were significantly different. Based on the low recoveries, it was concluded that UAE is a relatively inefficient extraction method, while ASE and MAE are equivalent methods. Taking into consideration the relative standard deviation (RSD) values, solvent volume, extraction time, and purchasing costs of the apparatus, MAE was considered superior to ASE for extraction of PCBs, DDTs and HCHs. [ABSTRACT FROM AUTHOR]

The article cites a study on evaluation of methyltin and butyltin pollution in Guanting Reservoir and its Downriver Yongding River in Beijing, China. Water samples from these waterbodies were collected at the late fall in 2000. Butyltin compounds in water samples were monitored by capillary gas chromatography with a laboratory-made flame photometric detector using quartz surface-induced tin emission after in-situ hydride derivatization and solid phase microextraction. Results of the study revealed the wide occurrence of methyltin and butyltin compounds in Guanting reservoir and its downriver-Yongding river.

Reports that trace pollutants in the surface water of the Arctic region have been analyzed by the capillary gas chromatography with the micro-electron capture detector (GC-μECD), the gas chromatography-mass spectrometry (GC-MS) and the inductively coupled plasmas-mass spectrometry (ICP-MS). How the ration of α-/γ-HCH indicates the different pesticide composition between these two regions and is the potential marker for the source of the OCPs.