Effects of asphalt on the enzymatic activity and bacterial community in soil

Abstract

Asphalt is an important material widely used in the coating of surfaces such as roads, roofs, linings of water basins and pipes, but it can be potentially hazardous to human and environment because certain substances exist in asphalt, including polycyclic aromatic hydrocarbons. However, it is unknown about the effect of asphalt on soil. The aim of this study is to examine the effects of asphalt on the physiochemical parameters, the enzymatic activity, and the copy number of 16s rRNA bacteria and archaea in soil. Freshly collected garden oils were amended with asphalt of various amounts after 1, 15 and 26 days, respectively. Asphalt application increased the total organic carbon, decreased the total phosphorus and pH values in soil while total nitrogen was not altered, suggesting asphalt can alter the nutrient composition. The copy number of 16s rRNA of bacteria increased in soil with addition of asphalt but that of archaea decreased. The activity of catalase, dehydrogenase, urease, sucrose, cellulase and polyphenol oxidase increased in soil modified with asphalt. Principal components analysis of these parameters resulted in three major components. Urease, sucrose, cellulose, bacteria, dehydrogenase, dehydrogenase, total organic carbon and total nitrogen weighed heavily in component 1, suggesting that the increase of organic carbon affect the enzymatic activity significantly. Although the asphalt may contain much toxic toxicity, asphalt can potentially improve the fertilization of the soil. Key words: Soil, asphalt, 16s rRNA, principal components analysis, bacteria.