Assessment of environmental impacts based on particulate matter, and chlorophyll content of urban trees

Abstract

Trees improve air quality, and they have irreplaceable aesthetic value in urban landscapes. The amount of dust deposited on tree leaves is a simple and cost-effective indicator of air quality. Our aim was to explore particle filtering capacity of roadside trees in an urbanized area. We also assessed the impact of meteorological conditions on the amount of deposited dust. We measured the leaf surface deposition, and chlorophyll content of leaves along a road section that started at an intersection and ended in a less disturbed suburban area in Debrecen city, Hungary. Samples were collected in July, and September from Celtis occidentalis, a frequent species. We found a significant negative correlation between dust deposition on the leaves, and the distance from the intersection in July, meaning that the amount of dust on the leaves decreased as the distance from traffic increased. In September, dust deposition decreased considerably compared to July, caused by the rainfall before the second sampling. Chlorophyll content also had a significant negative correlation with the distance from the traffic intersection in July, as it decreased towards the less disturbed end of the transect. We also found a positive correlation between dust deposition and chlorophyll content in July. Surprisingly, the exposure to moderate amounts of pollutants in the air caused an increase in chlorophyll content. Our findings suggest that dust deposition on leaves serves as a reliable indicator of traffic intensity, because excess dust caused by the proximity of car traffic can be detected on the leaf surface. Although, certain weather conditions like rainfall and wind can disrupt the patterns in dust deposition that have developed over an extended period through wash-off and resuspension. Hence, it is advisable to consider these effects while selecting the sampling time and evaluating the results. HighlightsO_LILeaves of urban trees are used as bioindicators of deposited dust pollution. C_LIO_LIDust deposition, and chlorophyll content was measured along a roadside transect. C_LIO_LIWe found that dust and chlorophyll content decreased with distance from traffic emissions. C_LIO_LIModerate level of dust pollution resulted in an increase in chlorophyll content. C_LI