23 primary schools have been selected in Tiaret city, and the collection of PM2.5 was performed in the morning, afternoon and evening, in the presence and absence of the pupils. The results found have shown a gradient of concentrations of PM2.5 by site typology. Low and average concentrations are recorded in the areas close to forests: 23.32±2.77 µg/m3 and the high concentrations are observed in the sites exposed to road traffic: 33.57±3.27 µg/m3 in winter. However, concentrations recorded in the urban sites are lower in the summer (sites exposed to road traffic: 25.33±2.85 µg/m3, sites close to the forests 23.78± 1.92µg/m3). We also noticed that the dominance of PM2.5 has been observed in the vicinity of the major axes of movement. The dispersion of these particles is illustrated by a detailed maps. The maps present information obtained by hierarchical classification, they aim to answer a need for spatial knowledge of the problem of particulate pollution in urban areas in the city of Tiaret. The hierarchical classification allowed to distinguish three groups of schools: urban, urban highly subject to dense road traffic and schools close to green spaces and forests. The results obtained revealed a high contamination of the atmospheric environment of the city of Tiaret by PM2.5 aerosols, taking into account the results recorded in primary schools. Mass concentration of PM2.5 in the 1st period (autumn and winter) is higher than that of the 2nd period (spring and summer). Indeed, the highest concentrations are recorded in the presence of pupils in winter.
The data from several weather stations in Western Algeria show a semi-arid climate during last decades. The entire study region showed a great variability in the occurrences of the first and second rainy days in the year. This variability is associated with a positive trend, showing a continuous increasing aridity in the south Mediterranean and the late arrival of the rainy season is well marked. The rainy season in the north of Algeria, spreads from September to June. The origin of the rains differ according to the seasons. The rainfall from June to October is of localized stormy origin, whereas in winter, the rainfall comes from the classical atmospherically perturbations arriving from North or North West. This work objective was to give a definition of the rainy season onset and to show its inter - annual variability according to the Niño and Niña years. The El - Niño phenomenon by its positive and negative phases seems to affect the start of the rainy season. The variability of the rainfall onset indices is very significant. There is a relative stability of the rainy season length over the long term period. A significant delay in the precipitation onset was observed during certain years. A method to define rainy season onset based on daily rainfall data from a weather station in the Algerian highlands was proposed. This approach is based on a climatic point of view, using a frequency analysis of precipitation and dates of their first occurrence. It delays the first heavy rain day (20 mm) when La - Niña settles. If EL-Niño settles, the first heavy rain (20 mm) day will be earlier. These results will improve the probabilistic forecasts of the beginning of the rainy seasons, the cessation as well as the lengths. This work is a preliminary confirmation that the El-Niño phenomenon really affects the Mediterranean climate.
The objective of this work is to determine and quantify the inorganic compounds of PM 2.5 aerosols; collected using a two-stage Dekati® PM10 impactor; in educational establishments in Tiaret-city "Algeria". It also aimed to follow the dispersion of these particles in sites near the forest, urban fabric and urban sites exposed to dense road traffic, as well as to determine the source of this type of pollution. 23 primary schools were chosen as sampling sites in Tiaret city. The collection of PM 2.5 was carried out in the winter and summer period. The spectroscopic analysis carried out by FTiR-ATR shows that the sulfate ions recorded their maximum in the summer period than in the winter, as well as the nitrate and ammonium ions which do not show a large seasonal difference. The dominant species in urban areas are NO 3 -, SO 4 -2 which due to the presence of a very important source of NOx and SO2 which, by gas-particle conversion, transform into nitrate and sulfate ions respectively. These species present a lower proportion in sites close to the forest. However, the same order of abundance of these ions exists in the two sampling periods. The main sources of NOx in urban sites are combustion phenomena linked in particular to the transport system, which is characterized by very dense traffic in the city's agglomeration.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.