Distributions, sources and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in topsoil at Ji’nan city, China

Surface soil (0-5 cm) samples from 17 sampling sites including different functional areas at Ji'nan city in Shandong Province of China were collected and analyzed for 16 EPA priority polycyclic aromatic hydrocarbons (PAHs). The total PAH concentrations were in the range from 1.31 mg kg(-1) to 254.08 mg kg(-1) (dry weight), and the average level of total PAHs was 23.25 mg kg(-1). The highest total PAHs concentrations were found in steel and iron plant at industrial areas. The total PAHs concentrations in industrial areas were markedly higher than those in other different functional areas. According to comparing total PAHs concentration in Ji'nan city to that of other urban areas, it was found that total PAHs concentrations were 6 to 137 times higher than other areas because of some specific sampling sites such as steel and iron plant and one main roadside. The results showed that PAHs in topsoil of Ji'nan city were suffered from strong pyrogenic influence, especially in industrial areas. However about 52.9% soil samples were mainly originated from both pyrogenic and petrogenic mixed sources based on Flu/Pyr ratios and Phe/Ant ratios. Furthermore, It was found that all individual PAHs except Fle were significantly correlated (P < 0.01) with LMW, HMW, total PAHs and SOM, and individual PAHs except Fle in soils were significantly correlated (P < 0.01) with each other. The nemerow composite index to assess the environmental quality showed that the soil sample of steel and iron plant in industrial areas and one main roadside were heavy pollution of PAHs, and about 47% soil sampling sites were safety, about 53% soil sampling sites were got different grades of PAHs pollution.     

Relationships of relative humidity with PM<Subscript>2.5</Subscript> and PM<Subscript>10</Subscript> in the Yangtze River Delta,China

Severe particulate matter (PM, including PM_2.5 and PM₁₀) pollution frequently impacts many cities in the Yangtze River Delta (YRD) in China, which has aroused growing concern. In this study, we examined the associations between relative humidity (RH) and PM pollution using the equal step-size statistical method. Our results revealed that RH had an inverted U-shaped relationship with PM_2.5 concentrations (peaking at RH = 45–70%), and an inverted V-shaped relationship (peaking at RH = 40 ± 5%) with PM₁₀, SO₂, and NO₂. The trends of polluted-day number significantly changed at RH = 70%. The very-dry (RH < 45%), dry (RH = 45–60%) and low-humidity (RH = 60–70%) conditions positively affected PM_2.5 and exerted an accumulation effect, while the mid-humidity (RH = 70–80%), high-humidity (RH = 80–90%), and extreme-humidity (RH = 90–100%) conditions played a significant role in reducing particle concentrations. For PM₁₀, the accumulation and reduction effects of RH were split at RH = 45%. Moreover, an upward slope in the PM_2.5/PM₁₀ ratio indicated that the accumulation effects from increasing RH were more intense on PM_2.5 than on PM₁₀, while the opposite was noticed for the reduction effects. Secondary transformations from SO₂ and NO₂ to sulfate and nitrate were mainly responsible for PM_2.5 pollution, and thus, controlling these precursors is effective in mitigating the PM pollution in the YRD, especially during winter. The conclusions in this study will be helpful for regional air-quality management.     

城市污水厂污泥化学调理深度脱水机理

城市污水厂剩余污泥脱水是当前实际生产中亟待解决的问题。考察了厦门市集美污水厂剩余污泥经FeCl3和CaO,投加量分别为污泥质量分数的0.5%～0.7%和1.0%～1.5%化学调理前后污泥粒度、形态及胞外聚合物(extracellular polymeric substances,EPS)的变化。结果表明,调理后污泥比阻降低86%,污泥颗粒之间细碎紧密,细菌表面变得粗糙,经板框压滤后含水率低于60%。由三维荧光光谱(three-dimensional emission and excitation matrixs,EEM)光谱分析可知,LB-EPS(loosely bound-EPS)同TB-EPS(Tightly bound-EPS)的荧光峰整体发生红移,出现位于IV区域的色氨酸类蛋白质荧光峰Ex/Em=313/380 nm。FeCl3和CaO的加入一方面破坏了污泥颗粒的细胞结构,使EPS大量溶出,细胞结合水变成表面吸附水;另一方面Fe3+和CaO水解,中和污泥负电荷,通过压缩双电层作用破坏污泥胶体颗粒的稳定,去除表面吸附水,大幅提高了污泥的脱水性能,利于进一步板框压滤脱水。     

以废渣磷石膏为原料水热法制备硫酸钙晶须

以磷石膏为原料,采用水热法制备硫酸钙晶须。借助X射线衍射仪(XRD)、扫描电子显微镜(SEM)及红外光谱仪(FT-IR)等仪器对产物进行表征,研究了反应温度和时间、料浆初始固液比及不同添加剂等因素对产物形貌及可溶磷含量等的影响。结果表明,最佳反应条件为:反应温度140℃,反应时间2 h,料浆固液比为1∶10,最佳添加剂及剂量为丙三醇(V醇/V总液为50%)。所得产物为六方晶系的CaSO4.0.5H2O,直径1～3μm,晶须长径比为45左右,合成率约95%,产物可溶磷含量由原样的0.41%降至0.21%。     

Impacts of simulated acid rain on recalcitrance of two different soils

Laboratory experiments were conducted to estimate the impacts of simulated acid rain (SAR) on recalcitrance in a Plinthudult and a Paleudalfs soil in south China, which were a variable and a permanent charge soil, respectively. Simulated acid rains were prepared at pH 2.0, 3.5, 5.0, and 6.0, by additions of different volumes of H₂SO₄ plus HNO₃ at a ratio of 6 to 1. The leaching period was designed to represent 5 years of local annual rainfall (1,200 mm) with a 33 % surface runoff loss. Both soils underwent both acidification stages of (1) cation exchange and (2) mineral weathering at SAR pH?2.0, whereas only cation exchange occurred above SAR pH?3.5, i.e., weathering did not commence. The cation exchange stage was more easily changed into that of mineral weathering in the Plinthudult than in the Paleudalfs soil, and there were some K⁺ and Mg²⁺ ions released on the stages of mineral weathering in the Paleudalfs soil. During the leaching, the release of exchangeable base cations followed the order Ca²⁺?>?K⁺?>?Mg²⁺?>?Na⁺ for the Plinthudult and Ca²⁺?>?Mg²⁺?>?Na⁺?>?K⁺ for the Paleudalfs soil. The SARs above pH?3.5 did not decrease soil pH or pH buffering capacity, while the SAR at pH?2.0 decreased soil pH and the buffering capacity significantly. We conclude that acid rain, which always has a pH from 3.5 to 5.6, only makes a small contribution to the acidification of agricultural soils of south China in the short term of 5 years. Also, Paleudalfs soils are more resistant to acid rain than Plinthudult soils. The different abilities to prevent leaching by acid rain depend upon the parent materials, types of clay minerals, and soil development degrees.     

Visible-light-induced photocatalytic reduction of Cr(VI) with coupled Bi2O3/TiO2 photocatalyst and the synergistic bisphenol A oxidation

Coupled Bi₂O₃/TiO₂ photocatalysts were fabricated by sol–gel and hydrothermal methods and characterized using various spectroscopy techniques. Photocatalytic reduction of Cr(VI) in aqueous solution, together with the synergistic effect of photodegradation of bisphenol A (BPA), was investigated using these coupled Bi₂O₃/TiO₂ under visible-light irradiation. Coupling of Bi₂O₃ inhibited the phase transformation from anatase to rutile and extended absorption region to visible light. Bi ions did not enter TiO₂ lattice and were more likely to bond with oxygen atoms to form Bi₂O₃ on the surface of TiO₂. Photovoltage signals in visible range revealed the effective interfacial charge transfer between Bi₂O₃ and TiO₂. Two percent Bi₂O₃/TiO₂ exhibited the highest photocatalytic activity of visible-light-induced reduction of Cr(VI). The addition of BPA effectively increased the photocatalytic reduction of Cr(VI). Simultaneously, the presence of Cr(VI) promoted the degradation of BPA, which was demonstrated by the investigation of TOC removal yield and generated intermediates. A possible mechanism of photocatalytic reduction of Cr(VI) and degradation of BPA in Bi₂O₃/TiO₂ system was proposed. The synergistic effect, observed between reduction of Cr(VI) and degradation of BPA, provides beneficial method for environmental remediation and purification of the complex wastewater.     

Correlation analysis of major control factors for the formation and stabilization of aerobic granule

In recent years, aerobic granular sludge technology has demonstrated significant advantages in areas such as the sludge–water separation, residual sludge minimization, simultaneous biological nitrogen and phosphorus removal, and toxic organic compounds degradation in biological wastewater treatment. However, the critical control factors and their relation during sludge granulation have not been revealed indeed, and the stability of aerobic granular sludge is still not good. The Gray’s correlation analysis was used to investigate the relationship of aerobic granular characteristics and control factors in the study. Results showed that the organic loading rate, hydraulic shear stress, and sludge settling time were the major factors affecting the aerobic sludge granulation, and the associated regulating strategy was important for the stabilization of granular sludge system. Based on above results, the mechanism of aerobic sludge granulation was proposed, and it was expected to favor the application of aerobic granular sludge technology.     

天然锰砂去除水中的砷

天然锰砂是一种廉价、高效的水处理用材料,但尚未用于水中砷的去除。实验研究了反应时间、砷形态、初始砷浓度、温度、溶液初始pH对吸附过程的影响。结果表明,天然锰砂对As(Ⅲ)的吸附能力大于As(Ⅴ)。25℃时,固液比为10 g/L的条件下,天然锰砂对初始浓度为5.0 mg/L的砷溶液吸附过程经72 h基本达到平衡,平衡时对As(Ⅲ)和As(Ⅴ)的去除率分别达到94.5%和85.9%。吸附过程符合Lagergren准一级反应动力学模型和假二级反应动力学模型。相比之下,假二级动力学模型拟合程度更高。对As(Ⅲ)和As(Ⅴ),45℃时的吸附量均大于25℃时。不同温度下,天然锰砂对As(Ⅲ)和As(Ⅴ)的吸附过程更符合Freundlich等温吸附模型。在溶液初始pH为3～10范围内,锰砂对砷的吸附能力受pH的影响较小。实验结果表明,天然锰砂是一种具有实际应用潜力的除砷材料。     

剩余污泥中微生物絮凝剂的提取方法比较

分别采用低浓度和高浓度剩余污泥对剩余污泥中微生物絮凝剂(MBF)的多种提取方法(超声法、树脂法、超声-树脂法、树脂-超声法、超声-树脂-超声法和树脂-超声-树脂法等)进行了比较研究.结果表明,各种复合形式的提取效果均优于超声法或树脂法单独使用的提取效果.在各种复合形式中,以树脂-超声法所提取MBF的含量最高且絮凝效果最好.此外,所提取的MBF浓度与污泥浓度正相关.从剩余污泥中直接提取MBF,在降低MBF生产成本的同时实现了污泥的资源化利用.