AMBIENT AIR QUALITY AND ITS EFFECT ON MONUMENTS

Abstract

Adequate knowledge of a situation is a prerequisite for any effective intervention aiming at its modification for achieving certain goals. This is true even in air pollution studies since the ambient air quality plays a vital role in assessment of the extent of pollution levels especially in urban areas. The concern for quality of urban air is being felt due to tremendous increase in anthropogenic activities resulting in deterioration of air quality at a faster rate. Thus national and international efforts are being diverted to check the air quality in urban areas throughout the world. In India also, much of the interest has been shown recently for maintaining the air quality. Recognising the importance of this, Acts have been passed in the last ten years. Concentration of pollutants vary over the map of the city due to combined effects of the source configurations and meteorological and topographical features of the area. Thus, with the objective of knowing the status of air quality and its probable effects on monuments, Agra city was selected as the study area, because of its recognised international importance as one of the tourist destinations. Primary pollutants (SPM, SO2, NOx, HC and CO) were monitored in the study area two times in winter season when they are supposed to be most concentrated. Second sampling schedule coincided with the coldest spell of 1990-91 winter for Agra region. Significant variations in a 24 hour period at different stations were. observed. In general, pollutant concentrations were (v) found maximum during afternoon sessions and least during night sessions. SPM, SO2, NOx, HC and CO levels were found as high as 649 μg/m3, 51 gg/m3, 100 mg/m3, 42628 Mg/m3 and 32280 gg/m3 respectively. An air quality index(AQI) was evaluated based on observed results and air quality during November(AQI=110) and December/January(AQI=168) was found in the category of Heavily polluted and severly polluted respectivly. Also, principal component analysis(PCA) was applied for three pollutants(SPM, SO2 and NOx),It shows that all stations are significant and mostly NOx correlates among stations. Chemical analysis for trace metals in filter paper collected suspended particulate matter was done. It was found that air borne particulates contain significant amount of metals. The properties of particulates/metals depends mainly on the size according to density. Recognising this, sizing of air borne particulate was carried out at two most significant stations in the study area using a seven stage Cascade Impactor. Further, different sized particulates collected on each stage of impactor were analyzed for five trace metals and showed a bimodal distribution. The mass median aerodynamic diameter(MMAD) and percentage of particulate metals in respirable range were also calculated. The obtained MMAD for the metals were found to be 1 comparable with data from other Indian cities. Forty one percent of Pb was found to be in respirable range. Surface soil samples were also collected and analysed for metals indicating high level of Fe(9952 4g/g) and Pb(273.5 gg/g).Fe was found (vi) contributing relatively a higher percentage (93.4%) compared to other metals analysed(Cd, Cr, Mn and Pb). In order to identify probable sources for metals one of the receptor models i.e., calculation of enrichment factors was adopted. The obtained enrichment factors were as high as 2707 for Cd, 20 for Cr, 6800 for Pb taking Fe as reference metal. However, Enrichment factor for Mn was found to be less than one. Soil also shows an enrichment factor as high as 358 for Cd and 105 for Pb. The decline in air quality also adversely affects the monuments. Themonuments not only preserve the cultural heritage but also brings foreign exchange by attracting tourists