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.
Biological effects of nanoparticles have attracted widespread attention. However, the interaction between plants and nanoparticles remains unclear. The purpose of this study was to investigate characteristics of nano-sized metal particles in two representative plant species, Erigeron canadensis and Boehmeria nivea, in the Guangdong Province, China. The stems of the plants were sliced and placed on Ni–C grids for field-emission transmission electron microscopy (TEM). The metal-bearing nanoparticles were further analysed for their size, shape, composition, content and other characteristics using X-ray energy spectrum analysis, scanning TEM and selected-area electron diffraction pattern. The results revealed that the plants contain nano-sized Au-bearing particles with a diameter of 5–50 nm, ellipsoid, spherical and bone-rod shapes or irregular morphology with smooth edges. These nanoparticles primarily consisted of Au, Cu, O and Cl. The discovery of Au-bearing nanoparticles in natural plant tissues is of great significance for biological nanoscience. Here, we discuss the function and absorption mechanism of Au-bearing nanoparticles in plants and present the influence of the discovery of Au-bearing nanoparticles in natural plants. 相似文献
Estimating the movement of dissolved contaminants in heterogeneous aquifers is very important for the monitoring design, risk assessment, and remediation of contaminated aquifers. This work explored the influence of source size, monitoring distance, and aquifer heterogeneity on the accuracy of contaminant mass discharge (CMD) estimation using leaching surface approach as well as on the plume spread uncertainty in a 2-D heterogeneous aquifer. The interaction among source size, monitoring distance, and aquifer heterogeneity regarding the accuracy of CMD estimation and the plume spread uncertainty at downstream of the contaminated aquifer was extensively investigated. The transient leaking of a contaminated aquifer in a saturated heterogeneous aquifer under steady-state flow conditions was simulated. The effect of aquifer heterogeneity on the CMD uncertainty was evaluated through the expected values and variance. The results showed that the CMD estimation error varied from underestimation in the mildly heterogeneous aquifer, over accurate estimation in the medium heterogeneous aquifer to overestimation in the highly heterogeneous aquifer. Additionally, the results illustrated that the mean and variance of the transverse spatial extent of the peak concentrations for the plume at the control plane were very sensitive to the aquifer heterogeneity and detectable concentrations of contaminants. 相似文献