Search

Surface sediment-associated synthetic pyrethroid insecticides (SPs) are known to pose high risks to the benthic organisms in Chaohu Lake, a shallow lake of Eastern China. However, the pollution status of the lake's tributaries and estuaries is still unknown. The present study was conducted to investigate the occurrence, compositional distribution, and toxicity of 12 currently used SPs in the surface sediments from four important tributaries, as well as in the sediment cores at their estuaries, using GC-MS for quantification. All SPs selected were detectable, with cypermethrin, es/fenvalerate, and permethrin dominant in both surface and core sediments, suggesting that these compounds were extensively applied. Urban samples contained the highest summed concentrations of the 12 SPs analyzed (ΣSP) in both surface and core sediments compared with rural samples, suggesting that urban areas near aquatic environments posed high risks for SPs. The mean concentration of ΣSP in surface sediments of each river was generally higher than that found in core sediments from its corresponding estuary, perhaps implying recent increases in SP usage. Surface sediments were significantly dominated by cypermethrin and permethrin, whereas core sediments were dominated by permethrin and es/fenvalerate. The compositional distributions demonstrated a spatial variation for surface sediments because urban sediments generally contained greater percentages of permethrin and cypermethrin, but rural sediments had significant levels of es/fenvalerate and cypermethrin. In all sediment cores, the percentage of permethrin gradually increased, whereas es/fenvalerate tended to decrease, from the bottom sediments to the top, indicating that the former represented fresh input, whereas the latter represented historical residue. Most urban samples would be expected to be highly toxic to benthic organisms due to the residue of SPs based on a calculation of toxic units (TUs) using toxicity data of the amphipod Hyalella azteca. However, low TU values were found for the samples from rural areas. These results indicate that the bottom sediments were exposed to high risk largely by the residual SPs from urban areas. The summed TUs were mostly attributable to cypermethrin, followed by λ-cyhalothrin and es/fenvalerate. Despite permethrin contributing ∼28.7 % of the ΣSP concentration, it only represented 6.34 % of the summed TUs. Therefore, our results suggest that high levels of urbanization can increase the accumulation of SPs in aquatic environments. [ABSTRACT FROM AUTHOR]

A bacterium capable of degrading phenol coupled with reducing chromium (VI) was isolated and was identified as beingPseudomonassp. JF122 using 16S rRNA sequence analysis. The bacterium was able to simultaneously remove 600 mg/L phenol and 2.0 mg/L Cr(VI) within 72 h. Results from a study of the phenol biodegradation coupled with chromium (VI) reduction suggested that the electron donors involved in the reduction of Cr(VI) were intermediate phenol degradation products. Phenol concentrations higher than 800 mg/L inhibited both phenol degradation and Cr(VI) reduction. However, at a phenol concentration of 200 mg/L, not enough electron donors were produced to fully reduce the initial Cr(VI) concentration (1.2 mg/L). Cr(VI) concentrations below 2.0 mg/L enhanced both phenol degradation and Cr(VI) reduction. Cr(VI) was reduced to soluble Cr(III), which remained in the supernatant solution. This bacterium seems to have potential for the efficient and simultaneous treatment of organic pollutants and heavy metals in complex wastewaters. [ABSTRACT FROM PUBLISHER]

Novel filter Palygorskite porous ceramsite (PC) was prepared using Palygorskite clay, pore-forming material sawdust, and sodium silicate with a mass ratio of 10:2:1 after sintering at 700°C for 180 min. PC was characterized with X-ray diffraction, X-ray fluorescence, scanning electron microscopy, elemental, and porosimetry. PC had a total porosity of 67% and specific surface area of 61 m2/g. In order to assess the usefulness of PC as a medium for biological aerated filters (BAF), PC and (commercially available ceramsite) CAC were used to treat wastewater city in two laboratory-scale upflow BAFs. The results showed that the reactor containing PC was more efficient than the reactor containing CAC in terms of total organic carbon (TOC), ammonia nitrogen (NH3-N), and the removal of total nitrogen (TN) and phosphorus (P). This system was found to be more efficient at water temperatures ranging from 20 to 26°C, an air–water (A/W) ratio of 3:1, dissolved oxygen concentration >4.00 mg/L, and hydraulic retention time (HRT) ranging from 0.5 to 7 h. The interconnected porous structure produced for PC was suitable for microbial growth, and primarily protozoan and metazoan organisms were found in the biofilm. Microorganism growth also showed that, under the same submerged culture conditions, the biological mass in PC was significantly higher than in CAC (34.1 and 2.2 mg TN/g, respectively). In this way, PC media can be considered suitable for the use as a medium in novel biological aerated filters for the simultaneous removal of nitrogen and phosphorus. [ABSTRACT FROM AUTHOR]

In the present study, surface sediment samples from 48 sites covering the whole water area and three main estuaries of Chaohu Lake were collected to determine the concentrations of 25 metal elements using microwave-assisted digestion combined with ICP-MS. Spatial variation, source appointments, and contamination evaluation were examined using multivariate statistical techniques and pollution indices. The results show that for the elements Cd, Pb, Zr, Hf, U, Sr, Zn, Th, Rb, Sn, Cs, Tl, Bi, and Ba, which had higher coefficients of variation (CV), the concentrations were significantly higher in the eastern lake than in the western lake, but other elements with low CV values did not show spatial differences. The accumulation of Cu, Zn, Rb, Sr, Zr, Cd, Sn, Cs, Ba, Hf, Ta, Tl, Pb, Bi, U, and Th in the surface sediments was inferred as long-term agricultural cultivation impact, but that of Ti, V, Cr, Mn, Co, and Ni may have been a natural occurrence. The contribution from industrial and municipal impact was negligible, despite the rapid urbanization around the studied area. Principal component analysis-multiple linear regression (PCA-MLR) predicted the contribution from agricultural activities to range from 0.45 ± 1.31 % for Co to 92.7 ± 17.7 % for Cd. The results of the pollution indices indicate that Chaohu Lake was weakly to moderately affected by Ti, V, Cr, Mn, Co, and Ni but was severely contaminated by Hf and Cd. The overall pollution level in the eastern lake was higher than that in the western lake with respect to the pollution level index (PLI). Therefore, our results can help comprehensively understand the sediment contamination by metals in Chaohu Lake. [ABSTRACT FROM AUTHOR]

In the present study, 28 polycyclic aromatic hydrocarbons (PAHs) were investigated in four sediment cores collected from the main river estuaries of Chaohu Lake, one of the severely polluted lakes in China. The results indicate that elevated concentrations of total PAHs (ΣPAH) were found in the samples from the estuary of Nanfei River (ENF), considering BaP-based total toxicity equivalent (TEQ-BaP) and toxic unit (TU) results; there are potential adverse environmental implications. The total organic carbon (TOC) played an important role on the accumulation of PAHs at ENF and the estuary of Tongyang River (ETY). The predominant PAHs are high molecular weight (HMW) homologous for all samples; as a result, industrial wastewater from a steel company is expectedly the key source of PAHs in ENF, while coke consumption would be the important source of PAHs at other three sampling sites. Vertical distribution of PAHs in the sediment cores could be explained by the local social and economic activities. Furthermore, a minor variation of PAH composition in the sediment core could be justified by the stable structure of energy consumption in the Anhui Province. These results justify the need for further enhancement of industrial wastewater treatment and development of renewable energies which are the key factors on the control of PAH pollution in China. [ABSTRACT FROM AUTHOR]

Purpose: Organophosphorus pesticides (OPs) are significant stressors in the aquatic ecosystem of lakes due to their extensive use in agriculture. To understand the potential ecotoxicological risk of OPs, we examined the occurrence, distribution, and sources of 12 selected OPs in surface and core sediment samples collected around Chaohu Lake, one of the most eutrophic lakes in Eastern China. Materials and methods: Eighteen surface sediments and four sediment cores were sampled from an important inflowing river and four main river estuaries around Chaohu Lake, respectively. All samples were analyzed for 12 selected OPs using a gas chromatograph equipped with a mass spectrometer. Results and discussion: The results show that two thirds of the selected OPs were frequently detected around the lake, with detection frequencies of more than 60 %. Dichlorvos was the predominant OP, comprising 89.6 % of the total concentration of the 12 OPs (defined as ΣOP) in all samples. ΣOP in surface sediment and in core sediments ranged from 0.50 to 6.45 and 0.27 to 23.33 ng g dry weight, respectively. High concentrations of ΣOP were found in estuaries of rivers flowing from agricultural lands, indicating that the selected OPs were mostly due to cultivation, and the vertical distribution of OPs in core sediments clearly showed the application history of OPs over the past few decades. The intercorrelation between OPs was likely affected by their sources, degradation rates, and deposition pathways. The poor correlation between OPs and total organic carbon (TOC) in the core sediments of Chaohu Lake might be ascribed to multiple sources of the TOC in Chaohu Lake. Conclusions: Despite previous studies demonstrated that most OPs were not detectable in bottom sediments due to their high water solubilities and reduced persistence, in the present study, we found that most of the selected OPs were frequently detected in bottom sediment samples collected around Chaohu Lake, which have been identified with long-term eutrophication, suggesting that the OPs likely migrated from the water to the bottom sediment due to the occurrence of massive amounts of phytoplankton. Therefore, the environmental behavior and fate of OPs in a eutrophic lake require more attention given their ecotoxicity. [ABSTRACT FROM AUTHOR]

Nitrate and Fe(III) are two terminal electron acceptors in anaerobic respiration by microorganisms growing in the anoxic soil or sediment environment. In the current paper a facultative anaerobic dissimilatory Fe(III)- and nitrate-reducing bacterium was isolated from the Linchong tailings, a skarn-type copper mine tailings, located in Anhui. Skarn often formed at the contact zone between intrusions of granitic magma bodies into contact with carbonate sedimentary rocks. This made the tailings possessed strong acid neutralizing capacity and pH of the pore water was 6.8–8.6. The isolate, which was designated strain CW (CCTCC AB 2013114), was a gram-negative rod bacterium and belonged to the gamma subgroup p of the proteobacteria, closely (99.0%) related toPseudomonas stutzeri. In defined medium, strain CW was shown to grow anaerobically with the acetate using the ferric iron or nitrate as the electron acceptors. Results also showed that strain CW could not grow in the presence of ferrous iron and nitrite. [ABSTRACT FROM AUTHOR]

δ -MnO 2 /zeolite nanocomposites were prepared with natural zeolite, potassium permanganate, and manganese sulfate by oxidation-reduction precipitation, which were used to simultaneously remove Fe 2+ , Mn 2+ , and NH 4 + -N from groundwater. To investigate the performance and mechanism of Fe 2+ , Mn 2+ , and NH 4 + -N removal from groundwater by δ -MnO 2 /zeolite nanocomposites, static batch experiments were conducted under different environmental conditions in a zero-oxygen atmosphere using SEM, TEM, Zeta potential, FTIR, and XPS techniques. The experimental results showed that the manganese-oxide-coated natural zeolite was δ -MnO 2 , and Fe 2+ , Mn 2+ , and NH 4 + -N adsorption on the δ -MnO 2 /zeolite nanocomposites could be best described with the pseudo-second-order kinetic model and the Langmuir model. In addition, the maximum adsorption capacities of Fe 2+ , Mn 2+ , and NH 4 + -N were calculated to be 215.1, 23.6, and 7.64 mg·g -1 , respectively. The removal mechanism of NH 4 + -N from the solutions by zeolite was via the action of ion exchange, and the adsorption and oxidation catalysis of δ -MnO 2 -coated zeolite were responsible for the removal of Fe 2+ and Mn 2+ . This research indicates that δ -MnO 2 /zeolite nanocomposites could be used as highly efficient adsorbents to simultaneously remove Fe 2+ , Mn 2+ , and NH 4 + -N from water.

Nitrogen elements play an important role in the biogeochemical cycle of artificial wetlands. In this study, we investigated the anaerobic transformation of ammonia nitrogen and its main pathways in sediment in an artificial wetland. Results showed that the anaerobic ammonia oxidation (ANAMMOX) process and iron reduction occurred in wetland sediment, coupled with anaerobic ammonia oxidation (Feammox). Feammox used Fe(Ⅲ) to oxidize ammonia nitrogen to produce nitrogen; intermediate products were nitrate, nitrite, and N 2 O. Addition of ferrihydrite promoted the Feammox process and ammonia nitrogen loss caused by Feammox was enhanced from 1.69 to 2.72 mg·(kg·d) -1 . When ferrihydrite was added, a loss of 28% of total nitrogen (TN) in the wetland occurred, associated with Feammox, increasing to 42%. Anaerobic ammonia oxidation was significantly inhibited with addition of ferrihydrite and TN loss in the system decreased by about 25%. Results showed that the formation of goethite by mineralization of ferrihydrite inhibited the ANAMMOX process, promoting Feammox to lead to competing electronic donors for the S-ANAMMOX process, causing inhibition of the S-ANAMMOX process. This achieves the purpose of reducing TN loss in the wetland system. In addition, this may have some significance for further understanding the interaction between iron reduction and the nitrogen cycle in the wetland.

C-Fe 3 O 4 composite material [magnetic biomass char (MBC)] was prepared by pyrolysis of a mixture of wheat straw and siderite at 500℃. The MBC was characterized by XRF, FTIR, XRD, SEM, XPS, and a magnetic susceptibility device. The effect of contact time, pH value, initial Cd 2+ concentration, and ionic strength on the adsorption capacity of the MBC to Cd 2+ was investigated. The results showed that the BET surface areas of the MBC and biomass char (BC) were 23.38 m 2 ·g -1 and 7.20 m 2 ·g -1 , respectively, total pore volumes were 1.04×10 -1 cm 3 ·g -1 and 2.23×10 -2 cm 3 ·g -1 , and average pore diameters were 17.74 nm and 12.38 nm. The magnetic susceptibility of the MBC was 42900×10 -8 m 3 ·kg -1 . FTIR showed that phenolic hydroxyl and carboxyl functional groups bound metal ions on the surface of the MBC and BC. The kinetic data of the MBC were described well by the pseudo-second-order model. Isothermal adsorption of Cd 2+ by MBC and BC was fitted well by the Freundlich equation. The adsorption velocity increased with an increase of pH in the region 3-6 and then stabilized in the region 6-9. The adsorption capacity of Cd 2+ decreased slightly when ionic strength increased from 1 mmol·L -1 to 100 mmol·L -1 , whereas the desorption rate increased from 0.51% to 8.5%. The adsorption properties and characterization results illustrated that the removal mechanism of Cd 2+ likely was through adsorption and ion exchange on the surface of the MBC with a high amount of functional groups. In addition, magnetic adsorbents offered a significant advantage compared to other adsorbents in the aspect of separation from aqueous solution.

2,4-dichlorophenol(2,4-DCP), a highly toxic and refractory organic compound, was commonly used in pesticide production and thus widely distributed in water and soil. Goethite, magnetite and gypsum were added into the anaerobic system which simulated the natural anaerobic process to evaluate their effects on the anaerobic degradation of 2,4-DCP. It indicated that goethite, magnetite and gypsum had no appreciable adsorption ability toward 2,4-DCP under anaerobic condition. Mass balance analysis showed that only the transformation of 2,4-DCP to 4-chlorophenol(4-CP) occurred in all experimental groups. The addition of sodium acetate doubled the reductive dechlorination rate of 2,4-DCP in comparison with the groups without exogenous carbon source. The reductive dechlorination rate of 2,4-DCP was enhanced by the addition of goethite and magnetite, which was caused by the improved metabolic activity of dechlorination bacteria that played an important role in the anaerobic degradation of 2,4-DCP. Gypsum greatly inhibited or even stopped the degradation process of 2,4-DCP through restraining the growth and activity of dechlorination bacteria. This study will shed light on the migration and degradation of refractory chlorinated organic contaminants in anaerobic sedimentary environment, and the treatment of such matters in environmental technology.

Environmental pollution caused by synthetic pyrethroid insecticides has received a great deal of attention with the increase in usage recently.To understand the occurrence, environmental processes, fate and ecological impact of permethrin in Chaohu Lake, fugacity based multimedia fate model combining species sensitivities model (SSD) were employed.The concentration distribution, and transfer fluxes were predicted under nonequilibrium steady-state condition, and the effect of input parameter on the outputs was evaluated by sensitive and uncertainty analysis.Furthermore, SSD model of aquatic organisms was constructed for permethrin to assess the potential ecological risk and to determine the maximum annual input amount of permethrin for the purpose of protecting 95% of species.The results showed that the predicted concentrations of permethrin in air, water and sediment were 3.99×10 -16 , 5.63×10 -11 , 1.95×10 -5 mol·m -3 , and sediment was the largest sink.Most permethrin was transported from water to air via volatilization, but elimination from air was mostly by particle dry deposition.Permethrin in water was predominately from advection, and was removed by deposition of suspended particulate matter.Sediment associated permethrin was generally derived from suspended particulate matter deposition, and was eliminated by resuspension and sediment burial.The results of SSD model suggested HC 5 value was at 0.97 ng·L -1 , which was much higher than the predicted environmental concentration of permethrin in water.Only 0.77% of species was possibly impacted by exposure to permethrin.In order to protect 95% of species in Chaohu Lake, the maximum annual input amount of permethrin should be controlled below 78.2 t·a -1 .

Natural limonite was used as a precursor to prepare γ -Fe 2 O 3 via thermal treatment. The influences of reaction temperature, manganese oxides existing in limonite and coexisting SO 2 and H 2 O on the catalytic reduction activity of the prepared γ -Fe 2 O 3 were evaluated, and the activity of SCR was compared with that of α -Fe 2 O 3 , by means of XRD, XRF, XPS, NH 3 -TPD, FT-IR and so on. The results showed that because the surface acidity of γ -Fe 2 O 3 is stronger, the SCR temperature window of γ -Fe 2 O 3 was 200-350℃ being broader than that of α -Fe 2 O 3 (200-300℃), and in the active temperature window, the NO removal reached over 99%. The existence of MnO 2 in the newly formed γ -Fe 2 O 3 slightly decreased the SCR reactivity at lower temperature (100-200℃), while it decreased the SCR reactivity at higher temperature (400-450℃). The existence of SO 2 led to the shifting of temperature window by 100℃ from 200-350℃ to 300-450℃, and the volume fraction of 5%H 2 O only had a tiny negative effect on the SCR reactivity of γ -Fe 2 O 3 . However, the coexisting SO 2 and H 2 O, especially when the volume fraction of SO 2 reached 0.12%, significantly decreased the SCR reactivity due to the generation of ammonium sulfate. Besides, although the magnetic susceptibility of reacted γ -Fe 2 O 3 experienced a slight decrease compared with the newly prepared γ -Fe 2 O 3 , the catalysts could still be used repeatedly by magnetic recycling.

In this study, the performance of photo-Fenton reaction on decomposition of toluene was investigated by a flowing column using toluene as a representative of volatile organic pollutants (VOCs). The effects of initial pH, H2O2 concentration, Fe2+ concentration, initial concentration of toluene on degradation of toluene by photo-Fenton reaction were evaluated. Mass spectrometry and gas chromatograph were utilized to detect the products. The results showed that the introduction of UV greatly enhanced the Fenton reaction by improving the generation of hydroxyl radicals. When the initial concentration of toluene was 260 mg x m(-3), the toluene removal can achieve 98% under the following experimental conditions: initial pH = 3.0, H2O2 20 mmol x L(-1), Fe2+ 0.3 mmol x L(-1). Furthermore, no other intermediate except CO2 was detected in the reaction that photocatalytic degradation of toluene in waste gas by the photo-Fenton, which indicates all the degraded toluene was mineralized into CO2.

Effects of goethite on the anaerobic fermentation process of organic fraction of municipal solid wastes, including the biogas production and characteristics of leachate, were investigated in the anaerobic digesters constructed by PVC. The results showed that the addition of goethite promoted hydrolysis and acidogenesis efficiency of solid wastes and gas production rate. The total gas volume was 163.4 L,which increased by 20% compared to the blank. The intermediate products of Fe2+ , NH+4 -N, NO-3 -N, COD and organic acids in the leachate were analyzed. Results showed that the addition of goethite reduced the system ORP to - 124 mV which could improve the activity of the anaerobic microorganism. Addition of goethite could also promote the utilization of organic acids which decreased the inhibition effects of organic acids on the anaerobic microorganism.