五氯酚标准样品的研制

五氯酚是美国ＥＰＡ公布的１２９种重点污染物名单以及我国环境优先监测污染物黑名单中的重点污染物,也是环境监测和环境科研工作中的主要对象。本文介绍了这种污染物毒理特性和液体介质标准样品的分析、研究、制备方法。     

朝阳地区大气扩散参数计算分析

利用朝阳西大营地区野外平衡球观测资料计算得出了一套大气扩散参数,并将该结果与其它扩散参数进行了比较,结果表明:在不同的稳定度下,朝阳西大营地区的σy和σz值均略大于同级Briggs公式给出的结果,但小于地形相对复杂的本溪地区。     

Stability and safety evaluation of mixed traffic flow with connected automated vehicles on expressways

Introduction: Connected automated vehicles (CAVs) technology has deeply integrated advanced technologies in various fields, providing an effective way to improve traffic safety. However, it would take time for vehicles on the road to vehicles from human-driven vehicles (HDVs) progress to CAVs. Moreover, the Cooperative Adaptive Cruise Control (CACC) vehicle would degrade into the Adaptive Cruise Control (ACC) vehicle due to communication failure. Method: First, the different car-following models are used to capture characteristics of different types of vehicles (e.g., HDVs, CACC, and ACC). Second, the stability of mixed traffic flow is analyzed under different penetration rates of CAVs. Then, multiple safety measures, such as standard deviation of vehicle speed (SD), time exposed rear-end crash risk (TER), time exposed time-to-collision (TET), and time-integrated time-to-collision (TIT) are used to evaluate the safety of mixed traffic flow on expressways. Finally, the sensitivity of traffic demand, the threshold of time-to-collision (TTC), and the parameters of car-following models are analyzed based on a numerical simulation. Results: The results show that the ACC vehicle has no significant impact on the SD of mixed traffic flows, but it leads to the deterioration of TET and TIT, making the reduction proportion of TER slower. When the penetration rate exceeds 50%, the increase of CACC vehicles reduces traffic safety risks significantly. Furthermore, the increase in traffic demand and car-following parameters worsens traffic safety on expressways. Conclusions: This paper suggests that the CACC vehicles degenerate into ACC vehicles due to communication failure, and the safety risk of mixed traffic flow increases significantly. Practical Applications: The application of CAVs can improve the stability and safety of traffic flow.     

Improvement of fruit and vegetable waste anaerobic digestion performance and stability with co-substrates addition

The effect of fish waste (FW), abattoir wastewater (AW) and waste activated sludge (WAS) addition as co-substrates on the fruit and vegetable waste (FVW) anaerobic digestion performance was investigated under mesophilic conditions using four anaerobic sequencing batch reactors (ASBR) with the aim of finding the better co-substrate for the enhanced performance of co-digestion. The reactors were operated at an organic loading rate of 2.46–2.51 g volatile solids (VS) l⁻¹ d⁻¹, of which approximately 90% were from FVW, and a hydraulic retention time of 10 days. It was observed that AW and WAS additions with a ratio of 10% VS enhanced biogas yield by 51.5% and 43.8% and total volatile solids removal by 10% and 11.7%, respectively. However FW addition led to improvement of the process stability, as indicated by the low VFAs/Alkalinity ratio of 0.28, and permitted anaerobic digestion of FVW without chemical alkali addition. Despite a considerable decrease in the C/N ratio from 34.2 to 27.6, the addition of FW slightly improved the gas production yield (8.1%) compared to anaerobic digestion of FVW alone. A C/N ratio between 22 and 25 seemed to be better for anaerobic co-digestion of FVW with its co-substrates. The most significant factor for enhanced FVW digestion performance was the improved organic nitrogen content provided by the additional wastes. Consequently, the occurrence of an imbalance between the different groups of anaerobic bacteria which may take place in unstable anaerobic digestion of FVW could be prevented.     

Stability of titania nanoparticles in soil suspensions and transport in saturated homogeneous soil columns

The stability of TiO₂ nanoparticles in soil suspensions and their transport behavior through saturated homogeneous soil columns were studied. The results showed that TiO₂ could remain suspended in soil suspensions even after settling for 10 days. The suspended TiO₂ contents in soil suspensions after 24 h were positively correlated with the dissolved organic carbon and clay content of the soils, but were negatively correlated with ionic strength, pH and zeta potential. In soils containing soil particles of relatively large diameters and lower solution ionic strengths, a significant portion of the TiO₂ (18.8-83.0%) readily passed through the soils columns, while TiO₂ was significantly retained by soils with higher clay contents and salinity. TiO₂ aggregate sizes in the column outflow significantly increased after passing through the soil columns. The estimated transport distances of TiO₂ in some soils ranged from 41.3 to 370 cm, indicating potential environmental risk of TiO₂ nanoparticles to deep soil layers.     

Influence of dissolved oxygen on aggregation kinetics of citrate-coated silver nanoparticles

Aggregation, an important environmental behavior of silver nanoparticles (AgNPs) influences their bioavailability and cytotoxicity. The work studied the influence of dissolved oxygen (DO) or the redox potential on the stability of AgNPs in aqueous environments. This study employed time-resolved dynamic light scattering (TR-DLS) to investigate the aggregation kinetics of citrate-coated AgNPs. Our results demonstrated that when DO was present, the aggregation rates became much faster (e.g., 3-8 times) than those without DO. The hydrodynamic sizes of AgNPs had a linear growth within the initial 4-6 h and after the linear growth, the hydrodynamic sizes became random for AgNPs in the presence of DO, whereas in the absence of DO the hydrodynamic sizes grew smoothly and steadily. Furthermore, the effects of primary particles sizes (20, 40, and 80 nm) and initial concentrations (300 and 600 μg/L) of AgNPs on aggregation kinetics were also investigated.     

Oxidative transformation of polybrominated diphenyl ether congeners (PBDEs) and of hydroxylated PBDEs (OH-PBDEs)

BACKGROUND, AIM, AND SCOPE: The historical and widespread use of polybrominated diphenyl ethers (PBDEs) as flame retardants in consumer products worldwide has caused PBDEs to now be regarded as pervasive environmental contaminants. Most recently, hydroxylated PBDEs (OH-PBDEs) and methoxylated PBDEs (MeO-PBDEs) have emerged as environmentally relevant due to reports of their natural production and metabolism. An important parameter for assessing the environmental impact of a chemical substance is persistence. By formulating the concept that persistence is the result of the substance's physicochemical properties and chemical reactivity, Green and Bergman have proposed a new methodology to determine the inherent persistence of a chemical. If persistence could be predicted by straightforward methods, substances with this quality could be screened out before large-scale production/manufacturing begins. To provide data to implement this concept, we have developed new methodologies to study chemical transformations through photolysis; hydrolysis, substitution, and elimination; and via oxidation. This study has focused on adapting an oxidative reaction method to be applicable to non-water soluble organic pollutants. MATERIALS AND METHODS: PBDEs and one MeO-PBDE were dissolved in tetrahydrofuran/methanol and then diluted in alkaline water. The OH-PBDEs were dissolved in alkaline water prior to reaction. The oxidation degradation reaction was performed at 50 degrees C using potassium permanganate as described elsewhere. The pH was maintained at 7.6 with disodium hydrogen phosphate and barium hydrogen phosphate, the latter also serving as a trapping agent for manganate ions. The oxidation reactions were monitored by high-performance liquid chromatography and reaction rates were calculated. RESULTS: The OH-PBDEs have very fast oxidative transformation rates compared to the PBDEs. The reaction rates seem to be primarily dependent on substitution pattern of the pi-electron-donating bromine substituents and of bromine content. There are indications that further reactions of OH-PBDEs, e.g., methylation to the MeO-PBDEs, decrease the oxidation rates, and thereby generate more persistent substances. DISCUSSION: The resistance of PBDEs to oxidation, a major degradation pathway in air, should be further investigated, since these compounds do undergo long range transport. With slight modifications, the original method has been adapted to include a larger variety of chemical substances, and preliminary data are now available on the oxidative transformation rates for PBDEs and of OH-PBDEs. CONCLUSIONS: The original oxidation degradation method can now include non-water soluble compounds. This modification, using low concentrations of test chemicals, allows us to measure oxidative transformation rates, for some of the lower brominated DEs, data that can be used to assess their persistence in future model calculations. Oxidative transformation rates for PBDEs are slow compared to those for the OH-PBDEs. This suggests that OH-PBDEs, when released into the environment, undergo faster oxidative metabolism and excretion than the PBDEs. RECOMMENDATIONS AND PERSPECTIVES: To evaluate the modified method, more degradation reactions with non-water soluble compounds should be investigated. Recent studies show that OH-PBDEs are present in rats and in humans and, because of their activity as endocrine disruptors, determining their subsequent environmental fate is of importance. The resistance of PBDEs to oxidative degradation should be acknowledged as of possible future concern. Several other compound classes (such as polychlorinated biphenyls (PCBs), hydroxylated polychlorinated biphenyls (OH-PCBs), and pharmaceuticals) need to be subjected to this screening method to increase the database of transformation rates that can be used with this model.     

Effect of Urmia Lake's drying on groundwater corrosion and scaling potential in the northwest of Iran (Case study: Spring and summer, 2015)

The most common problems in water distribution systems are corrosion and scaling, which cause both economic and customer health problems. The aim of the present study is to report the relationship between Urmia Lake's drying and the corrosion and scaling potential of groundwater used as drinking water during the spring and summer of 2015. Groundwater samples were collected from all of the catchments of the Urmia Lake basin, and the characteristics of the water were used to determine the corrosive and scaling indices using the Langelier Saturation Index and the Ryznar Stability Index. The results showed that the total dissolved solids measurement of the samples collected from the islands of Urmia Lake was higher than the maximum value of the standard level. In addition, the hardness in 36% of the zones was higher than that of the maximum suggested level. The concentration of calcium was lower than that of the standard, but the rest of the parameters were in the standard level range. Also, the results showed that the water of the Urmia Lake basin tends to be very scaling and corrosive. In order to control the corrosion and scaling caused by groundwater drawn from the catchments around Urmia Lake, measures should be taken to prevent Urmia Lake's drying and to manage the groundwater around this area. It is also suggested that a laboratory study regarding the condition of the distribution system be carried out to adjust the effective parameters, such as the pH.     

沈阳市地表水持续稳定达标关键措施与对策探讨

对沈阳市地表水环境特征及水质达标现状进行了分析,论述了地表水变化趋势,提出了实现地表水持续稳定达标的技术路径,要实现地表水环境质量持续稳定达标,必须采取优化经济结构及布局,持续推进污水集中控制,强化污染源治理,实施农村环境综合整治,提升河流生态环境质量和水体自净能力,强化水环境政策制度建设及环境监管等有效措施。