Predicting Cutoff Aerodynamic Diameter and Sharpness of Single Round-Nozzle Impactors with a Finite Impaction Plate Diameter

Abstract

This investigation numerically examined the cutoff aerodynamic diameter (da₅₀) and the sharpness (GSD) of the particle collection efficiency curve of impactors with a finite impaction plate diameter. Results revealed that the inertial impactors have a limited cutoff aerodynamic diameter at different air velocities. The extreme value of the cutoff aerodynamic diameter increases with the nozzle diameter (W)/the plate diameter (D_c). The computed da₅₀/D_c values of the impactors increase with W/D_c at various Reynolds numbers (Re) and with the nozzle-toplate distance (S)/D_c when Re is 100. The value of GSD slightly increases with W/D_c for Re of 10 and 100, although the effect of S/D_c on GSD is not evident at various Res. The particle collection efficiency curve of the impactor with a lower Re is less sharp than that with a high Re at various W/D_c and S/D_c values. Statistical equations closely fitted the obtained numerical results for Res of 10–3000. The equations are useful for directly calculating the cutoff aerodynamic diameter and the sharpness of the particle collection efficiency curve for single round-nozzle impactors with a finite impaction D_c.     

Phthalate exposure in pregnant women and their children in central Taiwan

Phthalate exposure was found to be associated with endocrine disruption, respiratory effects, reproductive and developmental toxicity. The intensive use of plastics may be increasing the exposure to phthalates in Taiwanese population, particularly for young children.We studied phthalate metabolites in pregnant women and their newborns in a prospective cohort from a medical center in Central Taiwan. One hundred maternal urine samples and 30 paired cord blood and milk samples were randomly selected from all of participants (430 pregnant women). Eleven phthalate metabolites (MEHP, 5OH-MEHP, 2cx-MEHP, 5cx-MEPP, 5oxo-MEHP, MiBP, MnBP, MBzP, OH-MiNP, oxo-MiNP, and cx-MiNP) representing the exposure to five commonly used phthalates (DEHP, di-isobutyl phthalate (DiBP), DnBP, BBP, DiNP) were measured in urine of pregnant women, cord serum and breast milk after delivery, and in urine of their children. Exposure was estimated with excretion factors and correlation among metabolites of the same parent compound. Thirty and 59 urinary samples from 2 and 5 years-old children were randomly selected from 185 children successfully followed.Total urinary phthalate metabolite concentration (geometric mean, μg L⁻¹) was found to be higher in 2-years-olds (398.6) and 5-years-olds (333.7) than pregnant women (205.2). Metabolites in urine are mainly from DEHP. The proportion of DiNP metabolites was higher in children urine (4.39 and 8.31%, ages 2 and 5) than in adults (0.83%) (p < 0.01). Compared to urinary levels, phthalate metabolite levels are low in cord blood (37.45) and milk (14.90). DEHP metabolite levels in women’s urine and their corresponding cord blood are significantly correlated. Compared to other populations in the world, DEHP derived metabolites in maternal urine were higher, while phthalate metabolite levels in milk and cord blood were similar. The level of phthalate metabolites in milk and cord blood were comparable to those found in other populations. Further studies of health effects related to DEHP and DiNP exposure are necessary for the children.     

Polybrominated diphenyl ethers (PBDEs) and indicator polychlorinated biphenyls (PCBs) in marine fish from four areas of China

The levels of polybrominated diphenyl ethers (PBDEs) and indicator polychlorinated biphenyls (PCBs) were determined in marine fish from four areas of China (South China Sea, Bohai Sea, East China Sea, and Yellow Sea) using GC/NCI-MS and GC/ITMS, respectively. Total concentrations of eight PBDEs (BDE-28, 47, 99, 100, 153, 154, 183 and 209) in all samples ranged from 0.3 ng g⁻¹ ww (wet weight) to 700 ng g⁻¹ ww, with median and mean values of 85 ng g⁻¹ ww and 200 ng g⁻¹ ww, respectively. BDE-209 and BDE-47 were the major congeners in all samples, contributing 54% and 19% to the total concentration, respectively. The sum of seven indicator PCB levels (CB-28, 52, 101, 118, 138, 153, and 180) ranged from 0.3 ng g⁻¹ ww to 3.1 μg g⁻¹ ww, with median and mean values of 6.4 ng g⁻¹ ww and 398 ng g⁻¹ ww, respectively. High contributions of CB-138 (32%) and CB-153 (25%) were found in all samples. In general, pollutants measured in this study were at high levels when compared with previous studies from other regions in the world. The relative abundance of BDE-209 may suggest that deca-BDE sources existed in studied area. And principal component analysis (PCA) showed that there were other PBDE sources in Yellow Sea. The pattern and PCA showed that PCB pollutions came from similar sources in the studied areas. In addition, concentrations of ∑₇PBDEs (u/209) were strongly correlated with those of ∑₇PCBs in all fish (r = 0.907, n = 44).     

农村生活固体垃圾的处理现状及影响因素

随着我国农村经济与农民收入水平的快速提高,农村生活固体垃圾产生与排放的数量快速增加,已经严重影响了农村环境、农民健康和农业可持续发展.该文的主要目的是基于甘肃和河北省60个村和240个农户的调研资料,深入了解农村生活固体垃圾的处理和管理现状及影响生活固体垃圾有效处理的制约因素.结果表明,大多数村没有处理生活固体垃圾的设施,总体看甘肃省拥有的处理设施要好于河北省.超过一半的村中生活固体垃圾都没有人管理,但部分村开始制定相关的管理计划.描述性统计分析和计量模型的分析结果表明,农村生活固体垃圾的处理状况与农民人均收入水平的提高和交通便利程度的改进有显著正相关关系,而非农就业机会的增加不利于当地生活垃圾的处理.     

Distribution and bioaccumulation of steroidal and phenolic endocrine disrupting chemicals in wild fish species from Dianchi Lake, China

The distribution and bioaccumulation of steroidal and phenolic endocrine disrupting chemicals (EDCs) were studied in various tissues of wild fish species from Dianchi Lake, China. In muscle tissue, 4-tert-octylphenol, 4-cumylphenol, 4-nonlyphenol and bisphenol A were detected in fish from each sampling site, with maximal concentrations of 4.6, 4.4, 18.9 and 83.5 ng/g dry weight (dw), respectively. Steroids (estrone, 17β-estradiol 17α-ethynylestradiol and estriol) were found at lower levels (<11.3 ng/g dw) and less frequently in muscle samples. The highest concentrations of steroids and phenols were found in liver, followed by those in gill and the lowest concentration was found in muscle. The field bioconcentration factors (BCFs) of phenols were calculated in fish species ranged from 18 to 97. Moreover, the measured tissue concentrations were utilized in order to estimate water concentration of steroids (4.4-18.0 ng/L). These results showed that steroidal and phenolic EDCs were likely ubiquitous contaminants in wild fish.     

Assessment of heavy metal pollution from a Fe-smelting plant in urban river sediments using environmental magnetic and geochemical methods

Environmental magnetic proxies provide a rapid means of assessing the degree of industrial heavy metal pollution in soils and sediments. To test the efficiency of magnetic methods for detecting contaminates from a Fe-smelting plant in Loudi City, Hunan Province (China) we investigated river sediments from Lianshui River. Both magnetic and non-magnetic (microscopic, chemical and statistical) methods were used to characterize these sediments. Anthropogenic heavy metals coexist with coarse-grained magnetic spherules. It can be demonstrated that the Pollution Load Index of industrial heavy metals (Fe, V, Cr, Mo, Zn, Pb, Cd, Cu) and the logarithm of saturation isothermal remanent magnetization, a proxy for magnetic concentration, are significantly correlated. The distribution heavy metal pollution in the Lianshui River is controlled by surface water transport and deposition. Our findings demonstrate that magnetic methods have a useful and practical application for detecting and mapping pollution in and around modern industrial cities.     

Occurrence of diarrheagenic Escherichia coli genes in raw water of water treatment plants

Purpose

The high incidences of waterborne diseases are frequently associated with diarrheagenic Escherichia coli (DEC). DEC may pose a health risk to people who contact surface water for recreation or domestic use. However, there is no published report on the monitoring of DEC in drinking water sources in Taiwan. In this study, the occurrence of DEC genes in raw water for water treatment plants in Taiwan was investigated.

Method

Raw water samples were taken from water treatment plants adjacent to the Kaoping River in southern Taiwan. Each water sample was treated with membrane filtration followed by DNA extraction from the concentrate and concentrate enrichment, respectively. The target genes for various DEC strains of genes were identified, including enteroaggregative E. coli (EAEC), enterohemorrhagic E. coli (EHEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC).

Results

Among 55 water samples analyzed, DEC genes were detected in 16 (29.1%) samples. Strain-specific genes for EAEC, EHEC, EIEC, and EPEC were found in the percentages of 3.6%, 10.9%, 9.1%, and 9.1%, respectively. The specific gene for ETEC is not detected in the study. By looking at the presence/absence of specific genes and water sample characteristics, water temperature was found to differ significantly between samples with and without EHEC gene. In addition, pH levels differed significantly for EHEC and EPEC presence/absence genes, and turbidity was significantly different for water with and without EPEC genes.

Conclusion

DEC genes were detected in 29.1% of the raw water samples in the study location. The potential health threat may be increased if the treatment efficiencies are not properly maintained. Routine monitoring of DEC in drinking water sources should be considered.     

Effects of compositional heterogeneity and nanoporosity of raw and treated biomass-generated soot on adsorption and absorption of organic contaminants

A biomass-generated soot was sequentially treated by HCl-HF solution, organic solvent, and oxidative acid to remove ash, extractable native organic matter (EOM), and amorphous carbon. The compositional heterogeneity and nano-structure of the untreated and treated soot samples were characterized by elemental analysis, thermal gravimetric analysis, BET-N₂ surface area, and electron microscopic analysis. Sorption properties of polar and nonpolar organic pollutants onto the soot samples were compared, and individual contributions of adsorption and absorption were quantified. The sorption isotherms for raw sample were practically linear, while were nonlinear for the pretreated-soot. The removal of EOM enhanced adsorption and reduced absorption, indicating that EOM served as a partitioning phase and simultaneously masked the adsorptive sites. By drastic-oxidation, the outer amorphous carbon and the inner disordered core of the soot particles were completely removed, and a fullerene-like nanoporous structure (aromatic shell) was created, which promoted additional π-π interaction between phenanthrene and the soot.     

间歇浸取对废物水泥窑共处置产品中Cr和As释放的影响

研究间歇浸取条件下废物水泥窑共处置产品中重金属Cr、As的释放,对水泥产品在实际应用中的环境安全性评价有重要意义.通过模拟煅烧实验制取含Cr和As的水泥熟料,并制取混凝土样品,采用pH影响实验和扩散浸出实验,研究了混凝土中Cr和As的溶解特性及其间歇浸取对混凝土中Cr和As释放的影响.结果表明,浸取方式对浸取液pH有较...     

稻秆对铜绿微囊藻抑制作用的研究

研究了稻秆浸出液对铜绿微囊藻生长的抑制作用.研究表明,稻秆浸出液中含有的化学物质抑制了铜绿微囊藻的生长繁殖.稻秆浸泡时间的延长,有利于提高浸出液的抑藻效果,但浸泡时间过长则无益于抑藻效果提高,浸泡时间为15 d时,抑制率能高达75.99%.稻秆浸出液投加量达7.5%以上具有显著的抑藻效果.不同部位的水稻秸秆浸出液对铜绿...