Diurnal, seasonal and weekdays–weekends variations of ground level ozone concentrations in an urban area in greater Cairo

Ground level ozone (O3) concentration was monitored during the period of December 2004 to November 2005 in an urban area in Greater Cairo (Haram, Giza). During the winter and summer seasons, nitrogen dioxide (NO2) and nitric oxide(NO) concentrations and meteorological parameters were also measured. The mean values of O3 were 43.89, 65.30, 91.30 and 58.10 ppb in daytime and 29.69, 47.80, 64.00 and 42.70 ppb in whole day (daily) during the winter, spring, summer and autumn seasons, respectively. The diurnal cycles of O3 concentrations during the four seasons revealed a uni-modal peak in the mid-day time, with highest O3 levels in summer due to the local photochemical production. The diurnal variations in NO and NO2 concentrations during the winter and summer showed two daily peaks linked to traffic density. The highest levels of NOx were found in winter. Nearly, 75%, 100%, 34.78% and 52.63% of the mean daytime concentrations of O3 during spring,summer, autumn and the whole year, respectively, exceeded the Egyptian and European Union air quality standards (60 ppb) for daytime (8-h) O3 concentration. About, 41.14% and 10.39% of the daytime hours concentrations and 14.93% and 3.77% of the daily hour concentrations in summer and the whole year, respectively, exceeded the Egyptian standard (100 ppb) for maximum hourly O3 concentration, and photochemical smog is formed in the study area (Haram) during a periods represented by the same percentages. This was based on the fact that photochemical smog usually occurs when O3 concentration exceeds 100 ppb. The concentrations of O3 precursors (NO and NO2) in weekends were lower than those found in weekdays, whereas the O3 levels during the weekends were high compared with weekdays. This finding phenomenon is known as the "weekend effect". Significant positive correlation coefficients were found between O3 and temperature in both seasons and between O3 and relative humidity in summer season, indicating that high temperature and high relative humidity besides the intense solar radiation (in summer) are responsible for the formation of high O3 concentrations.     

Nitrous acid concentrations in homes and offices in residential areas in Greater Cairo

Indoor and outdoor measurements of nitrous acid and nitrogen dioxide were conducted at four homes and two offices in residential areas in Greater Cairo during winter (2000-2001) and summer (2001) seasons. Indoor nitrogen dioxide concentrations were higher than outdoor levels at the four homes, whereas indoor concentrations of nitrogen dioxide were lower than outdoor levels at the two offices, during both seasons. Indoor nitrous acid concentrations were higher than outdoor levels at all homes and offices during the period of study. The mean indoor nitrous acid concentrations were 6.8 ppb and 3.67 ppb in the four homes, whereas they were 1.42 ppb and 1.24 ppb in the two offices, during the winter and summer seasons, respectively. Indoor/outdoor ratios of nitrous acid concentration were 6.94 in the winter and 5.03 in the summer for all of the homes. However, the ratios were 1.31 and 1.61 during the winter and summer seasons, respectively, for the two offices. Insignificant positive correlation coefficients were found between indoor and outdoor concentrations of nitrous acid at homes and offices. The maximum outdoor nitrous acid concentrations were recorded during the winter season. Significant positive correlation coefficients were found between nitrous acid and nitrogen dioxide and relative humidity in homes and offices. The ratios of nitrous acid to nitrogen dioxide concentrations ranged from 0.045 to 0.16, with a mean of 0.1, in the four homes, whereas the ratios ranged from 0.026 to 0.09, with a mean of 0.059, in the two offices.     

Passive air sampling of DDT, chlordane and HCB in the Pearl River Delta, South China: implications to regional sources

The Pearl River Delta (PRD) is one of the largest fast-developing economic zones in China. Hong Kong and the mainland part of the PRD differed in socio-economic development history and chemical management policies. Polyurethane foam (PUF)-passive air sampling (PAS) was deployed at 21 regional air quality monitoring stations across the PRD in summer and winter, respectively. Dichloro-diphenyl-trichloroethane (DDT), chlordane and hexachlorobenzene (HCB) were analyzed with GC-MS. High total DDT (240-3700 pg m(-3)) and chlordane (100-2600 pg m(-3)) concentrations were observed. Concentrations of DDTs and chlordane were higher in summer than winter; HCB vice versa. Spatially, the mainland part of the PRD generally displayed higher DDT concentrations than Hong Kong. Antifouling paint for fishing ships in coastal China was suggested to be an important current DDT source in the coast. The reason is unknown for the very low trans-/cis-chlordane (TC/CC) ratios (0.27) found in the mainland in winter. HCB concentrations were relatively uniform across the PRD, and long range transport of HCB from inland/North China to the PRD in winter was suggested.     

西安市黑碳气溶胶浓度特征及与气象因素和常规污染物相关性

利用西安市环境监测站超级站2013年9月1日—2015年5月31日黑碳气溶胶(BC)的监测数据,研究空气中BC浓度特征及其与气象因素和常规污染物相关性。结果表明:BC小时平均浓度均值在春季、夏季和冬季的变化趋势呈"W"型,秋季呈"V"型,且冬季的第一个最低值和峰值比春季和夏季的分别延迟1 h和2~3 h,且20:00~次日6:00秋季BC小时平均浓度均值高于当年冬季。BC浓度在秋季和冬季较高,夏季较低。冬季BC/PM_(2.5)基本最低,秋季BC/PM_(2.5)相对最高。BC日平均浓度与气温、降水和风速的日平均值为极负显著相关,且风速小于1.0 m/s时,其与风速呈最显著的负相关。除O_3外,BC日平均浓度与其他常规空气污染物浓度呈显著相关,表明其同源性很强,且受机动车尾气排放的影响更大。     

Application of passive sampling on assessment of concentration distribution and health risk of volatile organic compounds at a high-tech science park

The objectives of this study are to investigate the volatile organic compound (VOC) distribution using passive samplers and to assess the resulting health risks in a high-tech science industrial park. With the advantages of passive sampling techniques, long-term and wide-area samples are collected. The results show TVOC concentrations in summer, fall, winter, and spring are 7.14?±?5.66 ppb, 18.17?±?5.81 ppb, 10.30?±?3.54 ppb, and 14.56?±?4.53 ppb, respectively; those on weekdays and weekends are 14.36?±?6.80 ppb and 9.87?±?4.86 ppb, respectively; and those in industrial and residential zones are 12.97?±?0.39 ppb and 11.13?±?0.68 ppb, respectively. Based on concentration variations, and benzene, toluene, ethylbenzene, and xylene ratios, we can resolve the source origins. Health risks are assessed based on the resulting concentrations. In the case of non-cancer chronic effects, long-term exposure to these concentrations does not support there is a risk of adverse health effects. However, potential cancer risks of exposure to these concentrations may occur, especially to carbon tetrachloride and benzene. By applying this study’s procedures, information on VOC concentration distribution, source identification, and health assessment can be obtained and they are applicable to similar studies.     

Statistical analysis of arsenic contamination in drinking water in a city of Iran and its modeling using GIS

In this research, probable arsenic contamination in drinking water in the city of Ardabil was studied in 163 samples during four seasons. In each season, sampling was carried out randomly in the study area. Results were analyzed statistically applying SPSS 19 software, and the data was also modeled by Arc GIS 10.1 software. The maximum permissible arsenic concentration in drinking water defined by the World Health Organization and Iranian national standard is 10 μg/L. Statistical analysis showed 75, 88, 47, and 69% of samples in autumn, winter, spring, and summer, respectively, had concentrations higher than the national standard. The mean concentrations of arsenic in autumn, winter, spring, and summer were 19.89, 15.9, 10.87, and 14.6 μg/L, respectively, and the overall average in all samples through the year was 15.32 μg/L. Although GIS outputs indicated that the concentration distribution profiles changed in four consecutive seasons, variance analysis of the results showed that statistically there is no significant difference in arsenic levels in four seasons.     

Mercury concentrations in tidal marsh sparrows and their use as bioindicators in Delaware Bay, USA

National parks are used worldwide as a means to protect the ecological integrity of unique ecosystems. Dilek National Park in western Turkey is a protected habitat for several endangered and severely threatened species. Thirty-seven water and 59 sediment samples were collected and analyzed for pesticides at two different sampling depths. The park is contaminated with 16 different organochlorine pesticides, with more pesticides detected in sediments than in water. The most prevalent pesticides in the 30–60-cm depth were DDT (69.5% of the samples), heptachlor (62.3%), a-endosulfan (55% of samples), and endrin (37%). Lindane isomers were present, but at <30% of the sediment samples. These pesticides could be a long-term contamination source that enters the food web used by the very species the park is trying to protect.     

Indoor and outdoor formaldehyde concentrations in homes in residential areas in Greater Cairo

Indoor and outdoor measurements of formaldehyde were conducted at seven flats located in residential areas in Greater Cairo, during spring and summer seasons 1999. The mean daytime formaldehyde concentrations in kitchens, bedrooms and living rooms were 89, 100 and 100 ppb, respectively, in the seven flats. Significant positive correlations were found between the concentrations of formaldehyde found in these three rooms. On the other hand, no significant differences were found between the mean formaldehyde concentrations in these three rooms. The maximum mean concentration of formaldehyde (147 ppb) was recorded in a new flat, while the minimum concentration (43 ppb) was observed in an old flat. The maximum hourly and daytime concentrations were 350 and 225 ppb, respectively. Air temperature, relative humidity and the age of the flat are factors affecting the emission and concentration of formaldehyde. The maximum indoor and outdoor formaldehyde concentrations were recorded during the summer season. During the spring, 38% of the samples indicated that the concentration of formaldehyde in the seven flats exceeded 0.1 ppm, the American Society of Heating, Refrigerating, and Air Conditioning Engineers' (ASHRAE) standard; in the summer, this figure increased to 53%.     

Survey of carbon monoxide concentrations in selected urban microenvironments

Carbon monoxide concentrations were measured in six shops situated in narrow busy streets of the city centre for ten days in winter and ten days in summer and correlated with the measurements simultaneaously performed at an outdoor background reference point. The correlation was significant for four out of six shops in winter, but not in summer. Day-to-day variations seemed to be influenced by gross contamination due to changing weather conditions whereas differences in concentration levels from site to site were strongly influenced by the proximity and density of traffic. The exposure of a pedestrian in winter was in good correlation with background outdoor levels and it was considerably lower than that of a car driver driving though the city.     

Ground level nitrogen dioxide concentrations in the rural Waikato Valley,New Zealand

Ground level nitrogen dioxide (NO₂) concentrations have been measured for one year over an area of 400 square kilometres in rural New Zealand using an array of 21 sites. Three passive samplers were exposed at each site for intervals of two weeks from August 1989 to August 1990. The exposure sites were centred around the Waikato Valley township of Huntly (population 6900). Important features of the survey area include a 1000 MW thermal power station situated on the outskirts of the town, the Waikato River and State Highway 1, a major north-south traffic route along the valley. The NO₂ concentrations in the survey area ranged from below 0.1 to 10.1 ppb, with an annual average of 1.2 ppb. Seasonal variations indicate summer values about three times lower than those found in the winter. The spatial distribution of NO₂ appears to be related to contributions from State Highway 1.