2019 Vol. 38, No. 2
Biochar with a specific surface area (SSA) 341.27 m2·g-1 was first prepared by pyrolysis of stems of Typha in a nitrogen atmosphere. Then BC@BiOBr photocatalyst was prepared under hydrothermal conditions using the prepared biochar. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction(XRD), Zeta potential sizer, UV-Vis DRS spectroscopy and Photoluminescence (PL) were employed to characterize the properties of the pre-catalysts. The results showed that both BC@BiOBr and BiOBr catalysts were BiOBr sheets, of which BC@BiOBr catalyst was assembled from about 1 μm BiOBr sheet. The two catalysts were BiOBr crystal phase, but the amorphous BC was not detectable. According to the measurement of the surface charge for the reactant precursor and biochar, it was speculated that in the preparation process the positively charged bismuth hydroxide sedimentation was highly dispersed on the negatively charged biochar due to electrostatic attraction, as reflected by SEM observation that the biochar was formed as the core wrapped by BiOBr tablets. Therefore, the BC@BiOBr has similar crystallinity, morphology and SSA to BiOBr. However, the visible light response of BC@BiOBr was effectively improved as compared with BiOBr, resulting from BC@BiOBr clusters structure on the biochar surface. This may be due to effective inhabitation of the recombination between photogenerated holes and electrons formed on BC@BiOBr clusters. Rhodamine B (RhB) was used as a substrate probe to test the degradation rate of the catalyst under visible light irradiation for 90 min. It was found that BC@BiOBr had higher visible light photocatalytic activity (93.1%) than BiOBr (71.4%). As a result, BC@BiOBr had higher visible light catalytic activity than BiOBr, probably attributed to the formation of more oxygen radical.
Secondary organic aerosols (SOA) contribute significantly to fine aerosol particles in atmosphere. Therefore, accurate evaluation of their sources and formation is pivotal to fully understand their impacts on the environment, climate and human health. With the progress of the research, it has been found that the oxidation of primary low-volatility organic compounds (LVOCs), which was assumed originally to non-reactive, is an important contributor to the formation of SOA and is turning into a research focus. In this review, we outline the latest development on the oxidation of LVOCs and the corresponding formation of SOA, which consists of (1) the main oxidation mechanism, (2) the latest experimental processes, (3) the typical field measurements, and (4) the model studies. Due to the difficulties of their gas chromatograph detection, complexity of reactions, variability of atmosphere environment, uncertainty of modelling and so on, the major challenges ahead in laboratory, field and modeling studies of LVOCs oxidation are discussed. The discussion is believed to be helpful for future research directions, as well as for control strategy of pollution in China.
Acetylacetone (AA) can act as a photoactivator to enhance the transformation of pollutants, such as dyes, nitrate, and arsenate. However, the underlying mechanisms behind these reactions are unclear yet. In this work, structure-activity relationship in the UV/AA process was investigated by employing a series of α-substituted AA derivatives(AAs). In order to figure out the inductive effects, one of the two hydrogen atoms at the central carbon in AA was replaced with -CH3, -CH2CH3, and -Cl groups, respectively. It is well known that -Cl is an electron withdrawing group, whereas -CH3 and -CH2CH3 are electron donating groups. As a consequence, the electron density on the central carbon and the electron cloud distribution of these compounds were varied due to inductive effect. In AA-(CH3)2, the two hydrogen atoms at the central carbon were both replaced with -CH3. Three different types of dyes were selected as model compounds to check the photoactivities of the AAs. The effects of the substituting groups on the efficiency of the UV/AA process for decolorization were evaluated through parallel experiments. Under identical conditions, the k1 of the UV/AA-(CH3)2 process was close to that of UV/AA, indicating that the enol form of AA might not be of vital importance as previously proposed. The presence of -Cl had negligible effect on the efficiency of decolorization, whereas the presence of -CH3 and -CH2CH3 significantly accelerated both the self-photodegradation of AAs and the degradation of the three dyes. The results here provide a criterion for the selection of proper AAs for the photodegradation of dyes.
The structure and components of dissolved organic matter (DOM) are complex. Traditional drinking water treatment processes (coagulation, sedimentation, filtration, disinfection) and advanced treatment processes have limited removal of DOM and many generate disinfection by-products during the disinfection process. The structure and composition of DOM influence its removal effect during drinking water treatment. In order to gain a deeper understanding of the structure and morphological changes of DOM during drinking water treatment, various detection methods are needed to characterize the changes. This article focuses on the changes in the molecular weight, fractions, aromaticity and fluorescence components of DOM in different drinking water treatment processes, and summarizes the research progress on the characterization methods for drinking water research, including pretreatment classification (physical grading-Ultrafiltration membrane filtration, chemical fractionation-resin adsorption), ultraviolet-visible absorption spectroscopy, three-dimensional fluorescence spectroscopy, etc. The advantages and limitations of different characterization methods were discussed in detail in order to provide a scientific basis for the accurate assessment of DOM changes during water treatment.
A method was developed for the determination of halogenated methyl sulfonic acids (HMSAs) in environmental water by solid phase extraction (SPE) coupled with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Parameters affecting the performance of SPE-LC-MS/MS were optimized, including SPE conditions, LC separation column and mass spectrometry parameters. A weak anion exchange (WAX) cartridge was chosen as the pretreatment column. After an environmental water sample was loaded into the WAX cartridge, the analytes were eluted using 2 mL of 5% ammonium hydroxide in methanol, 2 mL of 2% formic acid in methanol, 2 mL of the mixture solution with dichloromethane and methanol (2:8, V/V). Five HMSAs, including trifluoromethanesulfonic acid, chloromethanesulfonic acid, dichloro- methanesulfonic acid, trichloromethanesulfonic acid, and bromomethanesulfonic acid, were separated on an Acclaim HILIC-10 column and detected using MS/MS with negative and multi reaction monitoring (MRM) mode. The mobile phase was mixture of acetonitrile (A) and 100 mmol·L-1 ammonium formate solution (B) with pH at 6.5. Under the optimized conditions, the calibration range was from 0.05 to 50 μg·L-1. The method limits of detection (LOD) were in the range of 0.005-0.039 μg·L-1, which were calculated as the concentrations resulting in a signal-to-noise ratio at 3 (S/N=3).The developed method was successfully applied to HMSAs analysis in environmental water sample, with satisfied recoveries (67.5%-95.4%) and relative standard deviations (RSD, n=5) at 8.5%-13.0%.
N-homoserine lactones (AHLs) are vital quorum-sensing signal molecules of gram-negative bacteria. A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was established to determine the AHLs in activated sludge. A mixture of acetonitrile and water served as the mobile phase and an electrospray positive ion mode was set. After seperation by mobile phase with gradient elution, the sample was measured in multi-reaction monitoring mode with a detection time of 10 min. The results showed that the method had a good linearity in the range of 1-1000 μg·L-1. The instrument detection limit, instrument quantification limit and average recovery efficiency were 1.0-2.0 μg·L-1, 2.0-5.0 μg·L-1, and 80.0%-113.4%, respectively. When this method was used to analyze the activated sludge from wastewater treatment plant and lab-scale sequential batch activated sludge reactor (SBR) system, different types of AHLs were detected with a good peak shapes and separation efficiency. Therefore, this method can satisfy the actual requirement for the measurement of AHLs in activated sludge.
A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed for the determination of nitrofuran metabolites residues in shellfish tissues. The residues of protein adducts from nitrofuran metabolites in shellfish tissues were hydrolyzed by HCl, followed by derivatizing with nitrobenzaldehyde. The resulting derivatives were extracted with ethyl acetate, and the organic layer was concentrated by a stream of nitrogen gas. After purification by matrix dispersed solid phase extraction combined with ultrafiltration, the samples were analyzed by LC-MS/MS using internal standard method. Electrospray ionization was applied and operated in positive ion mode. The calibration curve showed a good linearity in the range of 0.5-20 μg·L-1 with the correlation coefficient over 0.999. The average recoveries for the spiked samples at concentrations of 1.00, 2.50 and 10.0 μg·kg-1 ranged from 90.1% to 99.5% with intra and inter batch relative standard deviations below 15%. The limit of detection of nitrofuran metabolites was 0.50 μg·kg-1. This approach is proved to be a simple and efficient method to identify and quantify nitrofuran metabolites in shellfish tissues with satisfactory sensitivity and repeatability.
Application of coal fly ash as catalytic materials is an important means to realize its high added-value utilization. In this paper, the chemical composition and structure characteristics of coal fly ash were described in detail. The research status of coal fly ash based catalysts applied in organic pollatant degradation, organic synthesis and catalytic hydrogen production was reviewed, and the action mechanism of coal fly ash in different catalytic reactions were discussed. Coal fly ash, as a composite carrier, is rich in Si and Al, and has some irreplaceable advantages over single carriers. The composition and structure of coal fly ash had great influence on catalytic performance, and different active components and structure corresponded to different reactions. So, it had a wide range of adaptability. The main factors influencing catalyst performance include structure reorganization of Si-O-Si or Al-O-Si in coal fly ash, catalysts modification by Fe, Ca, Na, K, the interaction between the active components and the coal fly ash carrier, etc. Therefore, regulating the chemical composition and structure of coal fly ash accurately is an important means to improve the performance of coal fly ash based catalysts and the theoretical basis for expanding the high value-added utilization of coal fly ash in the future.
Chlorine dioxide, which is widely used in drinking water treatment, has a significant pre-oxidation effect on algae-containing water, but there is a risk of inorganic by-product formation. It is of great significance to optimize the application of ClO2 and explore the methods of controlling the by-product formation. There are currently only a few studies on the formation of by-products during the pre-oxidation of ClO2, and evey less reports about the treatment on the algae raw water. In this study, lab-scale experiments were conducted to determine the algae removal efficiency and inorganic by-product generation during ClO2 pre-oxidation on the algae-containing water. The experimental results showed that the amount of ClO2- increased with the increase of ClO2 dosage, the initial concentration of algae, pH and NOM concentration. Environmental concentrations of Fe2+ and Mn2+ promoted the production of ClO2-, while NH4+ had no effect on that. In addition, the amount of ClO2- generated during the process of Cyanophyta removal was significantly higher than that of Chlorophyta.
Taking Cu and Cr in the water washing solution of municipal solid waste incinerator (MSWI) fly ash as the research object, adopting the sedimentation method by blowing CO2, the effects of CO2 concentration, flow rate, blowing time, reaction temperature and heavy metal initial concentrations on the sedimentation of Cu and Cr in the water washing solution were studied. The results showed that CO2 could effectively precipitate Ca2+ and decrease the pH value of the water washing solution. Higher CO2 concentrations were beneficial to the sedimentation of Cu and Cr; The optimal process conditions of CO2 precipitation treatment were a CO2 concentration of 10%, a blowing time of 80 s, a flow rate of 2 mL·min-1and a reaction temperature of 40℃. Under these conditions, the sedimentation rates of Cu and Cr reached about 95% and 50%, respectively.
Appearance and components of water treatment plant sludge (WTPS) and calcined water treatment plant sludge (C-WTPS) were characterized by scanning electron microscope and energy dispersive spectrometry(SEM-EDS). Phosphorus adsorption characteristics of WTPS and C-WTPS were investigated through adsorption kinetics and adsorption isotherm tests. The release amount of ammonia nitrogen and total organic carbon of WTPS and C-WTPS was compared. The forms of adsorbed phosphorus in C-WTPS were analyzed. The results showed that, compared with WTPS, a large number of cracks appeared on the surface of C-WTPS. The mass percentage of carbon and nitrogen on the surface of C-WTPS decreased by 5.52% and 1.36% respectively, and the mass percentage of iron and aluminium on the surface of C-WTPS increased by 2.3% and 0.54% respectively. The results of kinetic experiment showed that the adsorption process of phosphorus on C-WTPS followed the pseudo-second-order model, which indicates that the adsorptes of phosphorus is mainly controlled by chemical action. The Langmuir and Freundlich equation could describe well the phosphorus adsorption process of C-WTPS. The Langmuir equation data indicated that the P saturation adsorption capacity of C-WTPS was 3.34 mg·g-1, which was 1.6 times that of WTPS. There was more inorganic phosphorus (IP) than organic phosphorus (OP) on WTPS, but the calcination converted OP in WTPS to IP. Fractionation of the phosphorus indicated that adsorbed phosphorus in C-WTPS existed in mostly non apatite inorganic phosphorus (NAIP), indicating that iron and aluminum on the C-WTPS played an important role in the process of phosphorus adsorption. The risk of ammonia nitrogen and organic matter release for C-WTPS is much lower than that of WTPS. Therefore, C-WTPS is a better material for phosphorus removal.
Widespread application of antibiotics in breeding industry has led to residues of multiple antibiotics in livestock manure, which has become an important source of antibiotics pollution in the environment. The contamination characteristics and ecological effects of various antibiotics in livestock manure and soils are addressed in this paper. And the influencing factors and research progress on composting technology to remove antibiotics in livestock manure are also discussed. The key in composting treatment technology for multiple antibiotics contamination in livestock manure is to control the associated parameters during composting process according to different antibiotics characteristics and improve the removal efficiency of composting.
Based on the analysis of aerosol samples collected during heating period in Lanzhou City in 2016, the characteristics of atmospheric pollution and its main controlling factors and sources were discussed. The results show that the main ionic components in the winter were NO3-,SO42-,Ca2+ and NH4+, accounting for 88.12% of the total ion concentration. The secondary transformation of pollutants from anthropogenic sources was the main factor. NO3- and Ca2+ have been increasing in recent years. Based on three-phase clustering and the analysis of potential sources of pollutants, it was found that the secondary pollution was serious in the winter in Lanzhou, and the proportion of pollutants emitted by motor vehicles increased. The air mass arriving in Lanzhou was led by Wuwei-Lanzhou. Tenggri desert and southwestern of Loess Plateau were the main sources of PM10 pollution in winter. Lanzhou City and Baiyin City were the main sources of NO2 pollution. Overall, the air quality of Lanzhou has greatly improved.
Laboratory simulation experiments were conducted to investigate the effects of Chlorella elliptica on the photoreduction of Hg2+ in water body. Different wavelengths of ultraviolet (UV) lamp and xenon lamp (visible light) were used as light sources. Chemical kinetic characteristics were analyzed for the experiments using different concentrations of living/dead Chlorella elliptica and under various light conditions. The results indicated that when the abundance of algae was 1×106 cells·mL-1, the release of Hg0 from living and dead algae treatment were 3.733 ng and 3.749 ng, respectively. The reduction rates of Hg2+ were 18.66% and 18.75% for living and dead algae treatment under visible light irradiation, respectively. Under UV light irradiation, the flux of Hg0 from living and dead algae treatment were the highest at 2.312 ng and 2.373 ng respectively, and the highest reduction rates of Hg2+ were 11.56% and 11.86%, respectively. When the abundance of algae increased from 0 cells·mL-1 to 10×106 cells·mL-1, under the visible light, UVA, UVB and dark conditions, the reduction rates of Hg2+ contained with living algae decreased from 21.45%, 22.86%, 26.75%, and 20.41% to 17.70%, 10.28%, 9.962% and 9.774%, respectively. For the dead treatments, the reduction rates decreased from 21.45%, 22.86%, 26.75%, and 20.41% to 18.15%,10.83%, 10.77%, and 10.39%, respectively. Therefore, Chlorella elliptica inhibited the photoreduction of Hg2+ and the inhibition was increased with the increase of the abundance of algae. Visible light played a major role in the Hg2+ photoreduction contained with algae, followed by UV light. The kinetics of photoreduction of Hg2+ by Chlorella elliptica under UV irradiation can be described by the Langmuir-Hinshelwood model. The rate constant k and Langmuir adsorption coefficient KL were calculated to be (0.6893-1.473)×10-4 ng·L-1·min-1 and (1.063-1.080)×10-2 L·ng-1, respectively.
Nitzschia closterium (N. closterium) was selected as the test organism to study the toxicity effects of 180 # fuel oil water accommodated fractions (WAF) during the exposure time of 96 h in the present study. The relative abundance of amino acids in the cells of N. closterium were measured. The results showed that the relative abundance of alanine (Ala) and histidine (His) increased with increasing culture time in the control group and low WAF concentrations (1% and 3%). However, the change of Ala was not obvious in the high WAF concentrations (5%, 7% and 10%), and the abundance of His first decreased and then increased. The relative abundance of cysteine (Cys) in the control group and low WAF concentrations (1% and 3%) decreased with the increase of culture time, while variation trend was opposite in the high WAF concentrations (5%, 7% and 10%).The relative abundance of proline (Pro) increased with increasing culture time in all the WAF concentrations, and the change of aspartic acid (Asp) was just opposite to the trend of Pro. The study shows that the main amino acids in N. closterium are sensitive to the 180 # fuel oil WAF, which can serve as the new approach to monitor the marine pollution caused by the oil spill.
Strain NAU-16 was isolated from heavy metal-loaded acidic wastewater by the method of Hungate operation. According to its morphology and 16S rDNA gene sequencing, this strain was identified to be Desulfurella amilsii. Its growth property and sulfur reduction ability at different temperatures (20-60℃), initial pH (1.0-7.0) and electron donors (acetate, propionate, lactate, glucose, glycerol, pyruvate) were investigated. The role of this strain in removing heavy metals in acid wastewater containing Zn2+, Cu2+, Ni2+ were evaluated in sequencing batch. The results showed that strain NAU-16 growed at optimum temperatures from 35℃ to 45℃ and a broad pH range from 3.0 to 7.0. It was able to couple the oxidation of acetate and glucose to the reduction of elemental sulfur. Furthermore, this isolate-mediated biological sulfur reduction strain NAU-16 showed efficient removal of Zn2+, Cu2+, Ni2+. Up to 99% Zn2+, Cu2+ and up to 90%-99% Ni2+ were removed after 12 days, with initial pH 3.0 and 4.0 treatment. Strain NAU-16 could be a good candidate to cope with low pH and high metal concentration wastewater.
To clarify the adaptation in plants to acid rain stress, we chose rice with stronger acidity tolerance as experimental object to study the effect of acid rain (AR) (pH 3.5/pH 2.5) on antioxidant enzyme activities and isozyme composition in rice roots. After 5-day exposure, activities of SOD, CAT and POD in rice roots treated with pH 3.5 AR were increased, and isozyme bands were thickened and brighter. Meanwhile, contents of H2O2, O2·-, MDA and membrane permeability were all increased while root length, root surface area, root volume and root/shoot ratio were decreased. In pH 2.5 AR treating group, activities of SOD and CAT were increased and bands of SOD and CAT isozyme were thicker and brighter than those in pH 3.5 AR group. But the activity of POD was decreased and bands of POD 3, POD 4 and POD 5 were obviously darkened. The increased contents of O2·-, H2O2 and MDA and membrane permeability and the decreased root length, root surface area, root volume and root/shoot ratio were all larger than those treated with pH 3.5 AR. After a 5-day recovery, all parameters of rice root under pH 3.5 AR stress were recovered to the control level whereas oxidative damage caused by pH 2.5 AR was irreversible. Therefore, the increase in SOD, CAT and POD isozyme in rice root could promote the activities of antioxidative enzymes to scavenge excessive accumulation of reactive oxygen species induced by AR and enhance plant tolerance to acid rain. Moreover, the regulating effect of antioxidave isozyme was limited by the intensity of acid rain.
Wetland eutrophication continues to worsen and reduce the self-purification capability of wetlands. Studies on the root-exudates adaptation mechanism of the floating plant Pistia stratiotes under phosphorus stress may provide a scientific basis for the development of rhizosphere control measures necessary to remediate plateau wetlands. Hydroponic experiments were performed in nutrient solution, and the root exudates of P.stratiotes under different levels of phosphorus stress were characterized. Results showed that the root exudates of P. stratiotes mainly comprised alkanes, esters, alcohols, amines, benzene and acidic compounds. The relative content of alkane, acid and amine in the non-phosphorus treatment secretions were high and accounted for 41.02%, 24.74% and 12.11% of the total detection area, respectively. Among them, the most secreted substances in the three types of compounds are cyclopentasiloxane 8.47%, phthalic acid 20%, naphthylamine 6.39%. Under phosphorus stress, the chemical species and corresponding relative contents of P.stratiotes root exudates varied greatly. The contents of specific compounds in P.stratiotes root exudates gradually decreased. Nevertheless, phthalate content remained high under each stress condition. The relative contents of organic acids in P.stratiotes root exudates were all higher in the presence of phosphorus stress than those in the absence of phosphorus stress. As phosphorus concentration increased, the types and relative contents of organic acids in P.stratiotes root exudates decreased. The relative contents of phthalic acid, benzene dicarboxylic acid and cyclohexasiloxane in root exudates under six level of phosphorus stresses varied and initially increased and then decreased. Phosphorus stress level was negatively correlated with phthalic acid and benzene dicarboxylic acid contents, whereas phthalic acid and benzene dicarboxylic acid were positively correlated. This study indicated that the increased exudation of phthalic acid by P.stratiotes roots under phosphorus stress is an important mechanism that underlies the response of this plant to environmental stress.
Based on groundwater pollution survey data, the pollution status and influencing factors of "Three-Nitrogen" in groundwater were investigated in the oasis area of Hotan River basin. The reeults showed that "Three-Nitrogen" pollution of groundwater in the oasis area of Hotan river basin was not serious, but increased over time. The content, detection rate and over standard rate of nitrate nitrogen were the highest, followed by ammonia nitrogen, and nitrite nitrogen was lowest in the groundwater. The spatial distribution of "Three-Nitrogen" content in the study area showed some pattern. In the horizontal direction, the content of nitrate nitrogen and ammonia nitrogen decreased gradually from south to north, but the distribution of ammonia nitrogen in the north was wider than that in the south. In the vertical direction, "Three-Nitrogen" content in the middle-deep unconfined groundwater area was higher than that in the shallow unconfined groundwater. Compared with other regions in Xinxiang, the content of nitrate nitrogen in the oasis area of Hogan river basin was high, while the content of nitrite nitrogen and ammonia nitrogen were low. The sources of "Three-Nitrogen" were mainly related to resident life and agricultural production.There were many factors that influenced the form and distribution characteristics of "Three-Nitrogen" in groundwater, which include the lithology and thickness of aeration zone, hydrochemical environment and groundwater runoff conditions.
In order to investigate the levels and distributions of parabens in the sediments from typical tidal estuarine zones in China, six paraben analogues, methyl-(MeP), ethyl-(EtP), propyl-(PrP), butyl-(BuP), benzyl-(BzP) and heptyl parabens(HepP) were determined by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The results showed that the total concentration (sum of six parabens:∑parabens) of parabens in the sediment samples ranged from 2.20 to 24.5 ng·g-1, with a geometric mean value of 8.11 ng·g-1. That was slightly higher than those reported from the United States (4.93 ng·g-1), Japan (5.78 ng·g-1) and South Korea (6.46 ng·g-1). MeP was the predominant compound among the six paraben analogues (detection rate:100%, percent contribution:79.9%), followed by PrP (91%, 17.7%). Nevertheless, BuP and HepP were not found in any sediment samples. The total concentration of parabens in the sediments from Jiulong Estuary was the highest (geometric mean ∑parabens:14.6 ng·g-1), while that from Beidai River Estuary was the lowest (4.34 ng·g-1). Principal component analysis suggests the similar source of parabens in the sediment samples from tidal estuarine zones in China.
This study aimed to identify the spatial distribution of endogenous load of nutrients and distribution characteristics of nitrogen and phosphorus in the pretreatment area, emerged plant area, submerged plant area and deep purification area of Yanlong Lake ecological purification system and evaluate the pollution of nutrients in the sediments of different units. The results showed that the contents of total nitrogen (TN), total phosphorus (TP) and organic matter (OM) in the surface sediments of Yanlong Lake were 156.43-1130.00 mg·kg-1, 615.23-1580.66 mg·kg-1, 5.00%-49.04%, respectively. The upper (1508.09 mg·kg-1) and lower (932.30 mg·kg-1) range of TP content was in the sediments of the pretreatment unit and emergence plant area B, respectively. The sediments of the emergence plant area A had the upper range of TN (1126.91 mg·kg-1) and OM (48.89%), and the lower range of TN (272.47 mg·kg-1) and OM (5.23%) was in the deep purification zone sediments. Occluded phosphorus (Abs-P) accounted for 75.3%-82.3% of TP, the largest proportion. Exch-P had ≤ 1% of TP. In the direction along the flow, the contents of Iron phosphorus (Fe-P) and Aluminum phosphorus (Al-P) presented a tendency of decrease. The contents of Exch-P and Ca-P in the direction along flow at first decreased and then increased, showing a U-shaped trend. Weak acid extractable form (WAEF-N) accounted for the largest proportion of TTN (45.3%-68.94%), and Strong oxidant extractable form (SOEF-N) had 10.45%-19.08% of TTN, the lowest proportion. The morphological nitrogen contents in the sediment TTN were in the order of WAEF-N > strong alkali extractable form (SAEF-N) > ion exchange form (IEF-N) > SOEF-N. Our results from the single factor index method, comprehensive pollution index, organic nitrogen and organic index method demonstrated that the pollution in the pre-treatment zone S1 and emergent water plant zone S2 is the most serious and the deep purification zone S6 is the least polluted, along with other treatment units polluted to one degree or another.
Occurrence and fate of three cyclic (D4-D6,CMS) and twelve linear (L5-L16,LMS) methylsiloxanes in the wastewater and sludge collected from a wastewater treatment plant (WWTP) in Shandong Province were studied. The concentrations of total methylsiloxanes(∑MS) in the influent were 15.7-65.7 μg·L-1 (Mean:39.2 μg·L-1), and ∑LMS were the predominant(98.2%). Influent samples collected during the summer contained the highest ∑MS concentrations(65.7 μg·L-1), followed by autumn(41.7 μg·L-1), winter(33.7 μg·L-1) and spring(15.7 μg·L-1). ∑MS concentrations in the effluent were 6.24-14.3 μg·L-1(Mean:10.6 μg·L-1), with 73.0% average removal efficiency. The ∑MS concentrations in the sludge ranged from 14.1 to 48.4 μg·g-1(Mean:20.3 μg·g-1). The logarithm values of solid-liquid distribution coefficients of D4-D6 and L6-L16 were 3.84-4.44 and 2.24-4.30, respectively. In addition, the hazard quotients(HQ) of siloxanes were used to evaluate their ecological risk to aquatic organisms, results suggested that the target compounds in the effluent would pose little potential adverse ecological risk.
We describe the analysis of multiple pesticides residues in complex food matrices using online sample preparation with an Agilent PAL RTC system followed by separation and detection using an Agilent 7890B GC and Agilent 7000D triple quadrupole GC/MS system. The online sample preparation method is based on micro-SPE technology and is combined with an automated workflow on the Agilent PAL RTC system. The objective of this application is the cleanup of the typically dirty extracts from the well-known QuEChERS sample extraction process to achieve ease-of-use and extended sample throughput with less maintenance. It is shown that the automatic system is robust for different kinds of food matrices. The repeatability of most of the analyte was excellent at less than 10% and the recovery range are all between 70 to 130%. This totally meets the requirements for pesticide residue analysis in foods.
A gel permeation chromatography method for simultaneous determination of 16 polycyclic aromatic hydrocarbons (PAHs) residual in edible oils was established and validated. The samples were initially extracted with cyclohexane-ethyl acetate solution (1:1,V/V) by vortex mixing, and the targeted PAHs was prepared using the gel permeation chromatography method to clean-up which removing most fats and sterols in samples, and the backgroud interference was effectively reduced. The analysis was performed by GC-MS and quantified by internal standard method. The SIM-Retention time and specific ions were used to confirm the PAHs. The average recoveries of 16 PAHs were almost in the range of 80.6%-106.7% at the spiked level of 1, 2 and 10 μg·kg-1 with the relative standard deviations of 1.3%-13.4%. In the method validation, correlation coefficients were higher than 0.999 with the linear ranging from 1 μg·L-1 to 50 μg·L-1 and the limits of detection was in rang of 0.11-1.1 mg·kg-1.