In the present study, ionic liquid-modified silica-coated magnetic nanoparticles (Fe₃O₄@SiO₂@IL) were synthesized and applied as adsorbents for extraction and determination of paraquat (PQ) followed by high-performance liquid chromatography. For assurance of the extraction efficiency, the obtained results were compared with those obtained by bared magnetic nanoparticles (MNPs). Experimental design and response surface methodology were used for optimization of different parameters which affect extraction efficiency of paraquat using both adsorbents. Under the optimized conditions, extraction recoveries in the range of 20–25 and 35–40 % with satisfactory repeatability values (RSDs%, n = 4) less than 5.0 % were obtained for bared MNPs and Fe₃O₄@SiO₂@IL, respectively. The limits of detection were 0.1 and 0.25 μg/L using Fe₃O₄@SiO₂@IL and bared MNPs, respectively. The linearity was obtained in the range of 0.25 to 25 μg/L and 0.5 to 25 μg/L for Fe₃O₄@SiO₂@IL and bared MNPs, respectively, with the coefficients of determination better than 0.9950. Finally, Fe₃O₄@SiO₂@IL was chosen as superior adsorbent due to more dispersion ability, higher extraction recovery, lower detection limit, as well as better linearity and repeatability. Calculated errors (%) were in the range of 3 to 10 % depicting acceptable accuracy for the analysis of PQ by the proposed method. Finally, the method was successfully applied for extraction and determination of PQ in some water and countryside soil samples.

The removal of artificial sweetener saccharin (SAC) in aqueous solution by electrochemical advanced oxidation using electro-Fenton process was performed. Experiments were carried out in an undivided cylindrical glass cell with a carbon-felt cathode and a Pt or boron-doped diamond (BDD) anode. The removal of SAC by electrochemically generated hydroxyl radicals followed pseudo-first-order kinetics with both Pt and BDD anode. The absolute rate constant of the SAC hydroxylation reaction was determined for the first time using the competition kinetic method and found to be (1.85 ± 0.01) × 10⁹ M⁻¹ s⁻¹. The comparative study of TOC removal efficiency during electro-Fenton treatment indicated a higher mineralization rate with BDD than Pt anode. The identification and evolution of short-chain carboxylic acids and inorganic ions formed during oxidation process were monitored by ion-exchange chromatography and ion chromatography, respectively. The assessment of toxicity of SAC and/or its reaction by-products during treatment was performed using Microtox® method based on the Vibrio fischeri bacteria luminescence inhibition. Results showed that the process was able to efficiently detoxify the treated solution.

Eutrophication is one of the greatest threats to global freshwater ecosystems. The phytoplankton responses to nutrient inputs vary in different water bodies, so it is particularly important to determine the nutrient thresholds and synergistic interactions between nutrients in different freshwater ecosystems. Field sampling and bioassay experiments were conducted to determine the thresholds of soluble reactive phosphorus (SRP), nitrate-nitrogen (NO₃-N), and ammonium-nitrogen (NH₄-N) in Miyun Reservoir. A separate nutrient addition bioassay was designed to assess the synergistic interactions between these nutrients. Chlorophyll a (Chl a) concentrations were used to estimate phytoplankton biomass. The results showed the following: (1) nutrient threshold bioassay indicated that eutrophication thresholds of SRP, NO₃-N, and NH₄-N should be targeted at below 0.04 mg P L⁻¹, 0.5 mg N L⁻¹, and 0.3 mg N L⁻¹, respectively, to limit the growth of phytoplankton. (2) The stimulatory effect of “NH₄-N plus P” on phytoplankton biomass was greater than “NO₃-N plus P” at the same N concentration, and “NH₄-N plus NO₃-N” did not show such associated stimulatory effect as “NH₄-N plus P” or “NO₃-N plus P”. (3) The average concentrations of total phosphorus (TP), NO₃-N, and NH₄-N in Miyun Reservior were 0.017 mg P L⁻¹, 0.620 mg N L⁻¹, and 0.143 mg N L⁻¹, respectively. The reservoir-wide average Chl a is below 20 μg L⁻¹ on an annual basis. (4) Ammonium was an important factor for the growth of phytoplankton and inputs of both NH₄-N and NO₃-N should be reduced to control bloom formation. Our findings imply that although P load reduction is important, appropriate reductions of all forms of N in watershed is recommended in the nutrient management strategy for Miyun Reservoir.

This study was conducted on Holothuria polii, Holothuria tubulosa, and Holothuria mammata collected from five stations with different depths in the Northern Mediterranean Sea. The body walls and guts of these holothurians were examined in terms of interactions of 10 metals (iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), chromium (Cr), cobalt (Co), vanadium (V), nickel (Ni), cadmium (Cd), and lead (Pb)) and one metalloid (arsenic (As)) using a multivariate analysis, and interspecies differences were determined. The multivariate analysis of variance (MANOVA) revealed significant differences between the species in terms of metal(loid) accumulations. The principal component analysis (PCA) showed a more association between H. tubulosa and H. polii with regard to the accumulation. The cluster analysis (CA) located Pb concentrations of the guts to the farthest place from all elements regardless of the species. A correlation analysis displayed that the element concentrations of the guts were more closely related to each other compared with those of the walls. The most inconsistent element in terms of correlations was the gut Fe contents. Accordingly, while Fe concentrations of H. mammata and H. tubulosa were correlated with all elements (except Pb) in divalent metal transporter 1 (DMT1) (divalent cation transporter 1 (DCT1) or natural resistance-associated macrophage protein 2 (NRAMP2)) belonging to the NRAM protein family, this was not the case in H. polii. Consequently, significant relationships between accumulated metal(loid)s that changed by tissues and sea cucumber species were observed.

Pb pollution caused by shooting sport activities is a serious environmental problem that has increased considerably in recent decades. The aims of this study were firstly to analyze Pb pollution in soils from a trap shooting range abandoned in 1999, secondly to study the effectiveness of different extractants [CaCl₂, DTPA, NH₄OAc, low molecular weight organic acids (LMWOA), and bidistilled water (BDW)] in order to determine Pb bioavailability in these soils, and finally to evaluate the phytoremediation ability of spontaneous vegetation (Agrostis capillaris L.). To this end, 13 soils from an old trap shooting range (Galicia, NW Spain) were studied. It was found that Pb levels in the soils were higher than 100 mg kg⁻¹, exceeding the generic reference levels, and three of these samples even exceeded the USEPA threshold level (400 mg kg⁻¹). In general, the reagent that best represents Pb bioavailability and has the greatest extraction efficiency was CaCl₂, followed by DTPA, NH₄OAc, LMWOA, and BDW. A. capillaris Pb contents ranged between 9.82 and 1107.42 mg kg⁻¹ (root) and between 6.43 and 135.23 mg kg⁻¹ (shoot). Pb accumulation in roots, as well as the presence of secondary mineral phases of metallic Pb in the adjacent soil, showed the phytostabilization properties of A. capillaris.

Our previous study has proven that waterborne hydrogen peroxide can affect the arsenic releasing process from arsenopyrite powder, but little is known about the change of morphology and element constitutes on arsenopyrite surface. In this study, a simulated experiment was conducted to examine the effects of hydrogen peroxide (at a concentration range of 5–50 μM) on the abiotic oxidation of arsenopyrite cubes. Scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS) were used to characterize the changes of microstructure morphology and elemental species on arsenopyrite surface. The results showed that micromolar level of H₂O₂ accelerated the release of arsenic and iron but passivated the sulfur release from arsenopyrite surfaces. As(III) oxidation in solution was enhanced at the early part of the experiment, but the release of As(III) was facilitated at the latter part. As(V) concentrations in solution increased along with the elevated H₂O₂ dosage level. The SEM images showed different surface microstructure on the surface of CK and all the treatments. EDS results showed that the ratios of S/Fe, Fe/As, and S/As in bulk arsenopyrite revealed evident increasing trend along with the increase of H₂O₂ dosage level. As the result of surface leaching, the XPS results did not show significant trend, while it suggests that H₂O₂ accelerated the formation of Fe–As oxidized layer on the arsenopyrite surface.

The concentrations and gas-particle partitioning of atmospheric polycyclic aromatic hydrocarbons (PAHs) were intensively measured in the Hengchun Peninsula of southern Taiwan. The concentrations of total PAH (Σ₃₈PAH), including gas and particle phases, ranged from 0.85 to 4.40 ng m⁻³. No significant differences in the PAH levels and patterns were found between the samples taken at day and at night. The gas phase PAH concentrations were constant year-round, but the highest levels of particle-associated PAHs were found during the northeast monsoon season. Long-range transport and rainfall scavenging mechanisms contributed to the elevated levels in aerosols andΣ₃₈PAH concentrations. Results from principal component analysis (PCA) indicated that the major sources of PAHs in this study were vehicular emissions. The back trajectories demonstrated that air mass movement driven by the monsoon system was the main influence on atmospheric PAH profiles and concentrations in the rural region of southern Taiwan. Gas-particle partition coefficients (K ₚ) of PAHs were well-correlated with sub-cooled liquid vapor pressures (P ᵒ L) and demonstrated significant seasonal variation between the northeast (NE) and the southwest (SW) monsoon seasons. This study sheds light on the role of Asian monsoons regarding the atmospheric transport of PAHs.

The recent outbreaks of dengue, chikungunya, and Zika virus highlighted the pivotal importance of mosquito vector control in tropical and subtropical areas worldwide. However, mosquito control is facing hot challenges, mainly due to the rapid development of pesticide resistance in Culicidae and the limited success of biocontrol programs on Aedes mosquitoes. In this framework, screening botanicals for their mosquitocidal potential may offer effective and eco-friendly tools in the fight against mosquitoes. In the present study, the essential oil (EO) obtained from the medicinal plant Origanum scabrum was analyzed by GC-MS and evaluated for its mosquitocidal and repellent activities towards Anopheles stephensi, Aedes aegypti, Culex quinquefasciatus, and Culex tritaeniorhynchus. GC-MS analysis showed a total of 28 compounds, representing 97.1 % of the EO. The major constituents were carvacrol (48.2 %) and thymol (16.6 %). The EO was toxic effect to the A. stephensi, A. aegypti, C. quinquefasciatus, and C. tritaeniorhynchus larvae, with LC₅₀ of 61.65, 67.13, 72.45, and 78.87 μg/ml, respectively. Complete ovicidal activity was observed at 160, 200, 240, and 280 μg/ml, respectively. Against adult mosquitoes, LD₅₀ were 122.38, 134.39, 144.53, and 158.87 μg/ml, respectively. In repellency assays, the EOs tested at 1.0, 2.5, and 5.0 mg/cm² concentration of O. scabrum gave 100 % protection from mosquito bites up to 210, 180, 150, and 120 min, respectively. From an eco-toxicological point of view, the EO was tested on three non-target mosquito predators, Gambusia affinis, Diplonychus indicus, and Anisops bouvieri, with LC₅₀ ranging from 4162 to 12,425 μg/ml. Overall, the EO from O. scabrum may be considered as a low-cost and eco-friendly source of phytochemicals to develop novel repellents against Culicidae.

A pilot-scale side-stream reactor process with single-stage sludge alkaline treatment was employed to systematically investigate characteristics of excess sludge hydrolysis and acidification with alkaline treatment and evaluate feasibility of recovering a carbon source (C-source) from excess sludge to enhance nutrient removal at ambient temperature. The resulting C-source and volatile fatty acid specific yields reached 349.19 mg chemical oxygen demand (COD)/g volatile suspended solids (VSS) d⁻¹ and 121.3 mg COD/g VSS d⁻¹, respectively, the process had excellent C-source recovery potential. The propionic-to-acetic acid ratio of the recovered C-source was 3.0 times that in the influent, which beneficially enhanced biological phosphorus removal. Large populations and varieties of hydrolytic acid producing bacteria cooperated with alkaline treatment to accelerate sludge hydrolysis and acidification. Physicochemical characteristics indicated that recovered C-source was derived primarily from extracellular polymeric substances hydrolysis rather than from cells disruption during alkaline treatment. This study showed that excess sludge as carbon source was successfully recycled by alkaline treatment in the process.

The fate of six human-use drugs was assessed and predicted in mesocosms designed to mimic shallow constructed wetlands during the onset of fall and senescence. Mesocosms were monitored for 28 days after the addition of carbamazepine, clofibric acid, fluoxetine and naproxen (nominal initial concentrations of 5 μg/L each), sulfamethoxazole, and sulfapyridine (nominal initial concentrations of 150 μg/L each), with and without phosphorous (P) addition at 1.6 mg/L. We hypothesized that addition of P would stimulate primary productivity and enhance removal of pharmaceuticals from the water column. Carbamazepine, clofibric acid, fluoxetine, and naproxen had half-lives of 8.7, 11, 1.5, and 2.5, and 8.6, 11.0, 1.4, and 2.5 days in treatments with and without P amendment, respectively. Sulfamethoxazole and sulfapyridine had half-lives of 17 and 4.9 days in mesocosms with P amendment and 17 and 4.7 days without amendment. A concurrent pulse of P with pharmaceuticals did not significantly enhance the removal of these compounds. Predicted half-lives from modeling efforts were consistent with observed values, with photolysis the greatest contributor to chemical attenuation.