Urban background of air pollution: Evaluation through moss bag biomonitoring of trace elements in Botanical garden

•The moss element enrichment did not significantly increase through 15-30-45-60 days.•The content of photosynthetic pigments decreased in the moss over exposure periods.•The antioxidative activity increased in the moss over the exposure time.•The Botanical garden represents the urban background of air pollution.

Urban background air pollution is the lowest level of pollution representative for the exposure of general urban population and mainly originates from non-local sources of pollution. Moss bag technique has been predominantly adopted for biomonitoring of trace elements across anthropogenically devastated areas, such as urban and industrial zones. However, the technique has been rarely used for measurement of background air pollution. In this study, element content and concomitant physiological parameters were assessed in the moss Hypnum cupressiforme Hedw. after its exposure within the bags in the Botanical garden (Belgrade, Serbia), as the presumable background area. During the summer of 2014, the moss bags were exposed for 60 days in total, and the sample analyses were performed every 15 days. As a control of the measured physiological parameters, a set of the moss bags was kept within the phytotron, under conditions of optimal-like growth. The total content of 21 elements, photosynthetic pigments (chlorophylls and carotenoids), phenolics, and antioxidative capacity were determined in the moss samples. The levels of trace elements were markedly lower within the Botanical garden in comparison to the street ambient, but still significantly higher than in the moss pristine habitat. However, the performed physiological tests indicated that the vulnerability of the moss during exposure time was not caused by the low trace element enrichment, but probably by the harsh meteorological parameters in an urban area. Finally, the Botanical garden could be assumed as control site for measurement of the urban background pollution, and it might be effectively measured by the moss bag technique.

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