Enhanced surface ozone during the heat wave of 2013 in Yangtze River Delta region, China.

Under the background of global warming, occurrence of heat waves has increased in most part of Europe, Asia and Australia along with enhanced ozone level. In this paper, observational air temperature and surface ozone in the Yangtze River Delta (YRD) region of China during summer of 2013, and the regional chemistry-climate model (RegCM-CHEM4) were applied to explore the relationship between heat wave and elevated ground-level ozone. Observations indicated that YRD experienced severe heat waves with maximum temperature up to 41.1°C, 6.1°C higher than the definition of heat wave in China, and can last for as long as 27days. Maximum ozone reached 160.5ppb, exceeding the national air quality standard (secondary level) as 74.7ppb. Moreover, ozone was found to increase at a rate of 4-5ppbK-1 within the temperature range of 28-38°C, but decrease by a rate of -1.3~-1.7ppbK-1 under extremely high temperature. A typical heat wave case (HW: 24/7-31/7) and non-heat wave case (NHW: 5/6-12/6) were selected to investigate the mechanism between heavy ozone and heat waves. It was found that chemical reactions play the most important role in ozone formation during HW days, which result in 12ppb ozone enhancement compared to NHW days. Chemical formation of ozone can be influenced by several factors. During heat waves, a more stagnant condition, controlled by anti-cyclone with sink airflow, led to less water vapor in YRD from south and contributed to less cloud cover, which favored a strong solar radiation environment and ozone significantly increasing. High temperature also slightly promote the effect of vertical turbulence and horizontal advection, which beneficial to ozone remove, but the magnitude is much smaller than chemical effect. Our study suggests that the chemical reaction will potentially lead to substantial elevated ozone in a warmer climate, which should be taken into account in future ozone related issues.

A study of the hourly variability of the urban heat island effect in the Greater Athens Area during summer.

Measurements of air temperature and humidity in the urban canopy layer during July 2009 in 26 sites in Athens, Greece, allowed for the mapping of the hourly spatiotemporal evolution of the urban heat island (UHI) effect. City districts neighboring to the mountains to the east were the hottest during the afternoon, while being among the coolest during the early morning hours. While during the early morning some coastal sites were the hottest, the warm air plume slowly moved to the densely urbanized center of the city until 14:00-15:00, moving then further west, to the Elefsis industrial area in the afternoon. Results from the UrbClim model agree fairly well with the observations. Satellite-derived land surface temperature (LST) data from AATSR, ASTER, AVHRR and MODIS, for pixels corresponding to ground stations measuring Tair, showed that LST can be up to 5K lower than the respective Tair during nighttime, while it can be up to 15K higher during the rest of the day. Generally, LST during late afternoon as acquired from AATSR is very near to Tair for all stations and all days, i.e., the AATSR LST afternoon retrieval can be used as a very good approximation of Tair. The hourly evolution of the spatial Tair distribution was almost the same during days with NE Etesian flow as in days with sea breeze circulation, indicating that the mean wind flow was not the main factor controlling the diurnal UHI evolution, although it influenced the temperatures attained. No unambiguous observation of the urban moisture excess (UME) phenomenon could be made.

Time lag between the tropopause height and 7Be activity concentrations on surface air.

A strong positive correlation between the seasonal changes of the tropopause height and the concentration of (7)Be in the surface air (R = 0.94, p < 0.0001) was observed at 40°N. Moreover, a strong positive correlation was revealed between the activity concentrations of (7)Be and the temperature T (°C) (R = 0.97, p < 0.001), confirming that the increased rate of vertical transport within the troposphere, especially during warmer months, has as a result the descent to the surface of air masses enriched in (7)Be. The results of the present work suggest that the temperature and the tropopause height are good indicators for transport time of air masses enriched in (7)Be to the surface. Higher values of temperature or tropopause height seem to result to shorter transport times. This is attributed to atmospheric convection which provides an effective mechanism for vertical transport of air masses. Increasing tropospheric temperature has generally as a result that convection penetrates more deeply which in turn leads to an increase in tropopause height. But, the atmospheric procedures do not occur immediately after the fluctuations of correlated factors. Thus, a time lag is expected between the tropopause height and (7)Be activity concentrations on surface air that might be from hours to days or weeks. The result suggests that (7)Be concentrations fully respond within three days after the changes in the tropopause height.

Smoking and pollution cause an increase in expired carbon monoxide in kiosk workers.

BACKGROUND: The measurement of expired carbon monoxide (CO) is a direct and non-invasive method for the detection of exposure to CO. OBJECTIVE: Our aim was to investigate the impact ofatmospheric pollution and smoking on expired CO in kiosk workers in Thessaloniki, Greece. METHODS: Twenty kiosks were selected in the commercial centre of city. The workers were all men aged 30.5 +/- 5.5 years. Measurements of expired CO and environmental CO were carried out twice per day, during two different seasons of the year, summer and winter. Expired CO was measured via a MicroCOMeter equipped with a fuel cell type electrochemical sensor. The CO levels in ambient air were determined using the method of Non-Dispersive Infra-Red analysis. RESULTS: Ambient CO levels were 2.11 +/- 0.64 ppm at h. 17:00 and 3.64 +/- 1.45 at h. 21:00 in winter and 1.26 +/- 0.17 ppm at h. 17:00 and 1.73 +/- 0.22 at h. 21:00 in summer. Expired CO in non-smokers was 3.2 +/- 2.7 ppm at h. 17:00 and 4.2 +/- 3.2 at h. 21:00 in winter and 1.3 +/- 1 ppm at h. 17:00 and 2.2 +/- 1.4 at h. 21:00 in summer. In smokers it was +/- 5.2 ppm at h. 17:00 and 13.9 +/- 7.5 at h. 21:00 in winter and 10 +/- 4.8 ppm at h. 17:00 and 18 +/- 7 at h. 21:00 in summer. All these differences were statistically significant. The concentrations of expired CO were significantly correlated with the number of the cigarettes smoked. CONCLUSIONS: The levels of expired CO in kiosk workers increase mainly due to smoking and to a lesser degree due to environmental pollution.

Transport of toxic organic aerosol pollutants from Yugoslavia to Greece during the operation "Allied Force".

Between March 24 and June 10, 1999 a large number of chemicals were ejected into the atmosphere because of air strikes on chemical industries and oil storage facilities in former Yugoslavia. Chemicals released into the atmosphere under suitable meteorological conditions can be transported across borders to large distances. The releases may have contained not only conventional air pollutants but also semi-volatile organic compounds (SOCs) which include dioxins, furans, PCBs and PAHs, all known to be hazardous to health. A measuring programme was initiated at Democritus University Thrace, Greece to monitor the chemical characteristics of atmospheric aerosol during February, March and April 1999. Particulate matter (aerosol) was collected on filters and was analysed using high-resolution gas chromatography coupled to high-resolution mass spectrometry for their content in SOCs. In the present work we show evidence of two events with three to twenty fold increased SOCs in the atmosphere of Northern Greece which were associated with air masses transported from the conflict area, following the destruction of chemical plants and oil storage facilities.

Neural network model for predicting peak photochemical pollutant levels.

In this paper, an attempt is made for the 24-hr prediction of photochemical pollutant levels using a neural network model. For this purpose, a model is developed that relates peak pollutant concentrations to meteorological and emission variables and indexes. The analysis is based on measurements of O3 and NO2 from the city of Athens. The meteorological variables are selected to cover atmospheric processes that determine the fate of the airborne pollutants while special care is taken to ensure the availability of the required input data from routine observations or forecasts. The comparison between model predictions and actual observations shows a good agreement. In addition, a series of sensitivity tests is performed in order to evaluate the sensitivity of the model to the uncertainty in meteorological variables. Model forecasts are generally rather insensitive to small perturbations in most of the input meteorological data, while they are relatively more sensitive in changes in wind speed and direction.

The war in Kosovo: Evidence of pollution transport in the Balkans during operation "Allied Force".

During the operation "Allied Force" in the spring of 1999, the burning or damaging of industrial and military targets in the Former Republic of Yugoslavia resulted in the release of a large number of chemicals into the atmosphere. The releases contained not only conventional air pollutants, but also Semi-Volatile Organic compounds (SVOs) which are known to be hazardous to health. Under suitable meteorological conditions, these chemicals can be transported across borders over large distances. In this paper, an analysis of measurements and dispersion calculations is presented which provides evidence of pollutant transport from the conflict area to Greece. The measuring program was carried out in Xanthi, Greece and included aerosol sampling and subsequent analysis for the determination of the concentration of SVOs including dioxins, furans, PCBs (PolyChlorinated Biphenyls), PAHs (Polycyclic Aromatic Hydrocarbons) and organic phthalates. This paper focuses on two episodes of organic phthalates that were observed during the conflict period. Pollution measurements are interpreted by means of air trajectories and dispersion calculations. For this purpose, the HYSPLIT_4 (HYbrid Single-Particle Langrangian Integrated Trajectory) modeling system is used to calculate the dispersion of toxic substances.

Enumeration and confirmation of Aeromonas hydrophila, Aeromonas caviae, and Aeromonas sobria isolated from raw milk and other milk products in Northern Greece.

A total of 138 raw cow's and 57 raw ewe's milk samples; 80 pasteurized cow's milk samples; 39 Anthotyros cheese, 36 Manouri cheese, and 23 Feta cheese samples; and 15 rice pudding samples were examined for the presence and any countable population of Aeromonas species. Twenty-two (15.9%) of the 138 cow's milk samples analyzed were contaminated with A. hydrophila. In 13 of these samples, populations of 3.0x10(2) to 5.0x10(3) CFU/ml were counted in starch ampicillin agar (SAA). Eighteen cow's milk samples (13.0%) were contaminated with A. caviae, and in eight of these samples, populations of 2.0x10(2) to 3.0x10(3) CFU/ml were counted in SAA. Five cow's milk samples (3.6%) were contaminated with A. sobria, and in two of these samples, populations of 2.5x10(3) and 5.0x10(3) CFU/ml were counted in SAA. Eleven cow's milk samples (7.9%) were contaminated with other Aeromonas spp. not classified. Eight (14.0%) of the 57 ewe's milk samples analyzed were contaminated with A. hydrophila. In these samples, populations of 5.0x10(2) to 5.0x10(3) CFU/ml were counted in SAA. Six ewe's milk samples (10.5%) were contaminated with A. caviae, and populations of 1.5x10(2) to 1.0x10(3) CFU/ ml were counted in SAA. Two ewe's milk samples (3.5%) were contaminated with A. sobria, and populations counted in SAA were 5.0x10(2) and 1.0x10(3) CFU/ml. Four samples (7.0%) were contaminated with other Aeromonas spp. not classified. A. hydrophila was recovered in 4 (10.2%) and 3 (8.3%) of the Anthotyros and Manouri cheese samples analyzed, respectively, but no countable populations were noted in SAA. None of the pasteurized milk, Feta cheese, and rice pudding samples yielded Aeromonas spp. The results of this work indicate that motile Aeromonas are common in raw milk in Greece. Also, the presence of A. hydrophila in the whey cheeses Anthotyros and Manouri indicates that postprocessing contaminations of these products with motile Aeromonas may occur during production.