Impact of dissolved organic matter on the photolysis of the ionizable antibiotic norfloxacin

Norfloxacin (NOR), an ionizable antibiotic frequently used in the aquaculture industry, has aroused public concern due to its persistence, bacterial resistance, and environmental ubiquity. Therefore, we investigated the photolysis of different species of NOR and the impact of a ubiquitous component of natural water — dissolved organic matter (DOM), which has a special photochemical activity and normally acts as a sensitizer or inhibiter in the photolysis of diverse organics; furthermore, scavenging experiments combined with electron paramagnetic resonance (EPR) were performed to evaluate the transformation of NOR in water. The results demonstated that NOR underwent direct photolysis and self-sensitized photolysis via hydroxyl radical (·OH) and singlet oxygen (¹O₂) based on the scavenging experiments. In addition, DOM was found to influence the photolysis of different NOR species, and its impact was related to the concentration of DOM and type of NOR species. Photolysis of cationic NOR was photosensitized by DOM at low concentration, while zwitterionic and anionic NOR were photoinhibited by DOM, where quenching of UOH predominated according to EPR experiments, accompanied by possible participation of excited triplet-state NOR and ¹O₂. Photo-intermediate identification of different NOR species in solutions with/without DOM indicated that NOR underwent different photodegradation pathways including dechlorination, cleavage of the piperazine side chain and photooxidation, and DOM had little impact on the distribution but influenced the concentration evolution of photolysis intermediates. The results implied that for accurate ecological risk assessment of emerging ionizable pollutants, the impact of DOM on the environmental photochemical behavior of all dissociated species should not be ignored.     

IKK inhibition prevents PM2.5-exacerbated cardiac injury in mice with type 2 diabetes

Epidemiological studies have found that individuals with diabetes mellitus(DM) display an increased susceptibility for adverse cardiovascular outcomes when exposed to air pollution.This study was conducted to explore the potential mechanism linking ambient fine particles(PM2.5) and heart injury in a Type 2 DM(T2DM) animal model. The KKay mouse, an animal model of T2DM, was exposed to concentrated ambient PM2.5 or filtered air for 8 weeks via a versatile aerosol exposure and concentrator system. Simultaneously, an inhibitor of IκB kinase-2(IKK-a)(IMD-0354), which is a blocker of nuclear factor κB(NF-κB)nuclear translocation, was administrated by intracerebroventricular injection(ICV) to regulate the NF-êB pathway. The results showed that ambient PM2.5 induced the increase of, NF-êB, cyclooxygenase-2(COX-2) and mitogen activated protein kinase(MAPK) expression in cardiac tissue, and that IMD-0354 could alleviate the inflammatory injury. The results suggested that the NF-êB pathway plays an important role in mediating the PM2.5-induced cardiovascular injury in the T2DM model. Inhibiting NFκB may be a therapeutic option in air-pollution-exacerbated cardiovascular injury in diabetes mellitus.     

Serious BTEX pollution in rural area of the North China Plain during winter season

Atmospheric BTEX compounds(benzene, toluene, ethylbenzene and xylenes) in a rural site of the North China Plain(NCP) were preliminarily investigated in winter, and the outdoor concentrations(25.8–236.0 μg/m3) were found to be much higher than those reported in urban regions. The pollution of BTEX inside a farmer's house was even more serious, with combined concentrations of 254.5–1552.9 μg/m3. Based on the ratio of benzene to toluene(1.17 ± 0.34) measured, the serious BTEX pollution in the rural site was mainly ascribed to domestic coal combustion for heating during the winter season. With the enhancement of farmers' incomes in recent years, coal consumption by farmers in the NCP is rapidly increasing to keep their houses warm, and hence the serious air pollution in rural areas of the NCP during winter, including BTEX, should be paid great attention.     

Synergistic effect of ozonation and ionizing radiation for PVA decomposition

Ozonation and ionizing radiation are both advanced oxidation processes (AOPs) without chemical addition and secondary pollution. Also, the two processes'' efficiency is determined by different pH conditions, which creates more possibilities for their combination. Importantly, the combined process of ozonation and ionizing radiation could be suitable for treating wastewaters with extreme pH values, i.e., textile wastewater. To find synergistic effects, the combined process of ozonation and ionizing radiation mineralization was investigated for degradation of polyvinyl alcohol (PVA) at different pH levels. A synergistic effect was found at initial pH in the range 3.0–9.4. When the initial pH was 3.0, the combined process of ozonation and ionizing radiation gave a PVA mineralization degree of 17%. This was 2.7 times the sum achieved by the two individual processes, and factors of 2.1 and 1.7 were achieved at initial pH of 7.0 and 9.4, respectively. The combined process of ozonation and ionizing radiation was demonstrated to be a feasible strategy for treatment of PVA-containing wastewater.     

Analysis of trace dicyandiamide in stream water using solid phase extraction and liquid chromatography UV spectrometry

An improved method for trace level quantification of dicyandiamide in stream water has been developed. This method includes sample pretreatment using solid phase extraction. The extraction procedure (including loading, washing, and eluting) used a flow rate of 1.0 mL/min, and dicyandiamide was eluted with 20 mL of a methanol/acetonitrile mixture (V/V = 2:3), followed by pre-concentration using nitrogen evaporation and analysis with high performance liquid chromatography–ultraviolet spectroscopy (HPLC–UV). Sample extraction was carried out using a Waters Sep-Pak AC-2 Cartridge (with activated carbon). Separation was achieved on a ZIC^®-Hydrophilic Interaction Liquid Chromatography (ZIC-HILIC) (50 mm × 2.1 mm, 3.5 μm) chromatography column and quantification was accomplished based on UV absorbance. A reliable linear relationship was obtained for the calibration curve using standard solutions (R² > 0.999). Recoveries for dicyandiamide ranged from 84.6% to 96.8%, and the relative standard deviations (RSDs, n = 3) were below 6.1% with a detection limit of 5.0 ng/mL for stream water samples.     

Ozone concentrations, flux and potential effect on yield during wheat growth in the Northwest-Shandong Plain of China

Ozone (O₃) concentration and flux (F_o) were measured using the eddy covariance technique over a wheat field in the Northwest-Shandong Plain of China. The O₃-induced wheat yield loss was estimated by utilizing O₃ exposure-response models. The results showed that: (1) During the growing season (7 March to 7 June, 2012), the minimum (16.1 ppbV) and maximum (53.3 ppbV) mean O₃ concentrations occurred at approximately 6:30 and 16:00, respectively. The mean and maximum of all measured O₃ concentrations were 31.3 and 128.4 ppbV, respectively. The variation of O₃ concentration was mainly affected by solar radiation and temperature. (2) The mean diurnal variation of deposition velocity (V_d) can be divided into four phases, and the maximum occurred at noon (12:00). Averaged V_d during daytime (6:00–18:00) and nighttime (18:00–6:00) were 0.42 and 0.14 cm/sec, respectively. The maximum of measured V_d was about 1.5 cm/sec. The magnitude of V_d was influenced by the wheat growing stage, and its variation was significantly correlated with both global radiation and friction velocity. (3) The maximum mean F_o appeared at 14:00, and the maximum measured F_o was − 33.5 nmol/(m²·sec). Averaged F_o during daytime and nighttime were − 6.9 and − 1.5 nmol/(m²·sec), respectively. (4) Using O₃ exposure-response functions obtained from the USA, Europe, and China, the O₃-induced wheat yield reduction in the district was estimated as 12.9% on average (5.5%–23.3%). Large uncertainties were related to the statistical methods and environmental conditions involved in deriving the exposure-response functions.     

Responses of soil ammonia oxidizers to a short-term severe mercury stress

The responses of soil ammonia-oxidizing archaea(AOA) and ammonia-oxidizing bacteria(AOB) to mercury(Hg) stress were investigated through a short-term incubation experiment.Treated with four different concentrations of Hg(CK,Hg25,Hg50,and Hg100,denoting 0,25,50,and 100 mg Hg/kg dry soil,respectively),samples were harvested after 3,7,and 28 day incubation.Results showed that the soil potential nitrification rate(PNR) was significantly inhibited by Hg stress during the incubation.However,lower abundances of AOA(the highest in CK: 9.20 × 10~7 copies/g dry soil; the lowest in Hg50: 2.68 × 10~7 copies/g dry soil) and AOB(the highest in CK: 2.68 × 10~7 copies/g dry soil; the lowest in Hg50:7.49 × 10~6 copies/g dry soil) were observed only at day 28 of incubation(P 0.05).Moreover,only the community structure of soil AOB obviously shifted under Hg stress as seen through DGGE profiles,which revealed that 2–3 distinct AOB bands emerged in the Hg treatments at day 28.In summary,soil PNR might be a very useful parameter to assess acute Hg stress on soil ecosystems,and the community structure of soil AOB might be a realistic biological indicator for the assessment of heavy metal stress on soil ecosystems in the future.     

Preparation of steel slag porous sound-absorbing material using coal powder as pore former

The aim of the study was to prepare a porous sound-absorbing material using steel slag and fly ash as the main raw material, with coal powder and sodium silicate used as a pore former and binder respectively. The influence of the experimental conditions such as the ratio of fly ash, sintering temperature, sintering time, and porosity regulation on the performance of the porous sound-absorbing material was investigated. The results showed that the specimens prepared by this method had high sound absorption performance and good mechanical properties, and the noise reduction coefficient and compressive strength could reach 0.50 and 6.5 MPa, respectively. The compressive strength increased when the dosage of fly ash and sintering temperature were raised. The noise reduction coefficient decreased with increasing ratio of fly ash and reducing pore former, and first increased and then decreased with the increase of sintering temperature and time. The optimum preparation conditions for the porous sound-absorbing material were a proportion of fly ash of 50% (wt.%), percentage of coal powder of 30% (wt.%), sintering temperature of 1130°C, and sintering time of 6.0 hr, which were determined by analyzing the properties of the sound-absorbing material.     

推进养殖污染防治,实现产业优化与环境保护双赢——对《水污染防治行动计划》的解读

针对《水污染防治行动计划》提出的畜禽养殖污染治理思路和措施,梳理了我国现阶段畜禽养殖污染防治中存在的问题,对《水污染防治行动计划》中提出的"调布局、建设施、促利用"三大举措进行了分析和解读,提出了落实《水污染防治行动计划》的几项重点工作,为地方推进畜禽养殖污染防治工作提供参考。     

低温低浊高色水源水处理的进展研究

针对低温低浊高色水源水质特征,对近年低温絮凝剂、低温强化混凝技术、低温膜集成技术研发与应用现状进行了综合论述.通过对低温混凝剂的絮凝机理与效果、各技术低温保持水质达标的应对策略的深入剖析,预测低温低浊高色水处理的发展趋势.研究表明,开发低温专用的高效低耗、质优价廉、无毒无二次污染的载体絮凝水处理剂,探索在不增加甚至减少工程造价条件下对低温期及平常期水处理均有效的工艺,是低温低浊高色水源水处理的关键.