Air pollutant measurement and respiratory inflammatory tests were conducted at a junior secondary school in Xi’an, Northwestern China. Hazardous substances including particulate matters (PMs), black carbon (BC) and particle-bounded polycyclic aromatic hydrocarbons (PAHs) were quantified both indoors and outdoors of the school. Source characterization with organic tracers and particle-size distribution demonstrated that the school’s air was mostly polluted by combustion emissions from the surrounding environment. The evaluation of health assessment related to air quality was conducted by two methods, including potential risk estimation of air pollutants and direct respiratory inflammatory test. The incremental lifetime cancer risks associated with PAHs were estimated and were 1.62 × 10−6 and 2.34 × 10−6, respectively, for indoor and outdoor fine PMs. Both the values exceeded the threshold value of 1 × 10−6, demonstrating that the carcinogenic PAHs are a health threat to the students. Respiratory inflammatory responses of 50 students who studied in the sample classroom were examined with a fractional exhaled nitric oxide (FeNO) test, with the aid of health questionnaires. The average FeNO concentration was 17.4 ± 8.5 ppb, which was slightly lower than the recommended level of 20 ppb established by the American Thoracic Society for children. However, a wide distribution and 6% of the values were > 35 ppb, suggesting that the potentials were still high for eosinophilic inflammation and responsiveness to corticosteroids. A preliminary interpretation of the relationship between air toxins and respiratory inflammatory response demonstrated the high exposure cancer risks and inflammatory responses of the students to PMs in the city.
• A pilot study was conducted for drinking water treatment using loose NF membranes.• The membranes had very high rejection of NOM and medium rejection of Ca2+/Mg2+.• Organic fouling was dominant and contribution of inorganic fouling was substantial.• Both organic and inorganic fouling had spatial non-uniformity on membrane surface.• Applying EDTA at basic conditions was effective in removing membrane fouling. Nanofiltration (NF) using loose membranes has a high application potential for advanced treatment of drinking water by selectively removing contaminants from the water, while membrane fouling remains one of the biggest problems of the process. This paper reported a seven-month pilot study of using a loose NF membrane to treat a sand filtration effluent which had a relatively high turbidity (~0.4 NTU) and high concentrations of organic matter (up to 5 mg/L as TOC), hardness and sulfate. Results showed that the membrane demonstrated a high rejection of TOC (by>90%) and a moderately high rejection of two pesticides (54%–82%) while a moderate rejection of both calcium and magnesium (~45%) and a low rejection of total dissolved solids (~27%). The membrane elements suffered from severe membrane fouling, with the membrane permeance decreased by 70% after 85 days operation. The membrane fouling was dominated by organic fouling, while biological fouling was moderate. Inorganic fouling was mainly caused by deposition of aluminum-bearing substances. Though inorganic foulants were minor contents on membrane, their contribution to overall membrane fouling was substantial. Membrane fouling was not uniform on membrane. While contents of organic and inorganic foulants were the highest at the inlet and outlet region, respectively, the severity of membrane fouling increased from the inlet to the outlet region of membrane element with a difference higher than 30%. While alkaline cleaning was not effective in removing the membrane foulants, the use of ethylenediamine tetraacetate (EDTA) at alkaline conditions could effectively restore the membrane permeance. 相似文献
A series of novel mortars were developed from composite binder of uncalcined FGD gypsum, fly ash (FA) and ground granulated blast furnace slag (GGBFS) for the good utilization of flue gas desulphurization (FGD) gypsum. At a fixed ratio (20%) of GGBFS to the composite binder, keeping consistency of the mortar between 9.5 and 10.0 cm, the properties of the composite mortar were studied. The results show that higher water/binder (W/B) is required to keep the consistency when increasing the percentage of FGD gypsum. No obvious influences of the W/B and content of FGD gypsum on the bleeding of paste were observed which keeps lower than 2% under all experimental conditions tried. The highest compressive and flexural strengths (ratio is 20% FGD gypsum, 20% GGBFS and 60% FA) are 22.6 and 4.3 MPa at 28 days, respectively. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicate that massive ettringite crystals and C-S-H gels exist in the hydration products. At 90 days the mortars with FGD gypsum is dramatically smaller drying shrinkage (563-938 micro strain) than that without FGD gypsum (about 2250 micro strain). The release of the SO(4)(2-) from the mortar was analyzed, indicating that the dissolution of sulfate increases with FGD gypsum. The concentration of SO(4)(2-) releasing from the mortar with 10% FGD gypsum is almost equal to that obtained from the mortar without FGD gypsum. The release of SO(4)(2-) from the mortar with 20% FGD gypsum is 9200 mg·m(-2), which is lower than that from the mortar with 95% cement clinker and 5% FGD gypsum. 相似文献