Green spaces in towns and cities need extra consideration as they may be damaging buildings in the area, according to new research from the Universities of Southampton and Surrey. When organic chemicals from trees and vegetation mix with air pollutants2 the resulting corrosive3 gas（腐蚀性气体） can increase the erosion of building materials, including stone, concrete and steel.Southamptons Dr Abhishek Tiwary, who is based within the Centre for Environmental Sciences, and Dr Prashant Kumar, from the University of Surrey, found that heritage buildings, built from limestone4 and sandstone, are particularly at risk.Local authorities have been encouraged to invest in green spaces, which can reduce greenhouse gases, cut down exposure to pollution and provide mental health benefits. However, the effect on buildings from the mix of pollutants and organic chemicals has not been previously5 accounted for.The damage is mainly caused by ground level ozone6, which is formed when volatile7 organic compounds given off by plants are broken down in sunlight and react with the common pollutant1 nitrogen dioxide.Using mathematical simulations, the research team investigated the effect of green vegetation on limestone and steel structures during different seasons.Species like sycamore maple8 and Douglas fir produced organic compounds which, combined with high levels of ground level ozone during the summer, heightened the concentration of ground level ozone, says Dr Tiwary.The effects of green infrastructure9 vary, depending on building material and the particular pollutant. Limestone, for example, found in the buildings like Westminster Abbey or the Houses of Parliament, is strongly eroded10 by increased levels of ground level ozone.Copper11, zinc12 and carbon steel are also corroded13 by levels of air pollutants and local climatic conditions.Despite their damaging effect on buildings, the researchers recognise the importance of green areas in urban centres. In the future, city planners should look into the species of vegetation they plant in green spaces, says Dr Tiwary. Such consideration might improve the structural14 longevity15 of buildings of historical importance.

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1 pollutant n.污染物质，散布污染物质者 参考例句： Coal itself is a heavy pollutant.煤本身就是一种紧急的污染物。 Carbon dioxide may not be a typical air pollutant.二氧化碳可能不是一种典型的污染物。