Effects Of Oil Pipeline Project Construction On Soil Nutrients In The Areas Along The Line

Oil pipeline projects work across a variety of ecological types and have a notable impact on the ecological environment along the pipeline projects. Soil quality degradation is one of the most important ecological impacts. In the section of Mohe-Daqing along the oil pipeline project,19soil samples were taken from representative spots both in operational region and non-operational region to evaluate the effects of pipeline construction on soil nutrients. The disturbance index of the impacts of construction on soil was developed to evaluate the differences of intensity of the influences on soil nutrients between the two study areas (Daxing’anling Mountains and Songnen Plain) and four different ecological types (forest, wetland, grassland and farmland). The indexes of soil nutrients were measured including soil pH, soil organic matter, total N, total P, total K, available N, available P, and available K. Two soil layers,0-20cm named topsoil and20-40cm named subsoil, were separated to take samples. The results showed that soil nutrients were significantly affected by pipeline construction, but the degree of the effect depended on the study areas, nutrient indexes, soil layers and ecological types.Pipeline construction dramatically increased soil pH values in Daxing’anling Mountains. Compared with non-operational region, the contents of soil organic matter, total N and available N of operational region were significantly lower (P<0.05), which indicated that construction resulted in a decline in their contents. Total P content of topsoil in operational region was significantly lower than that of topsoil in non-operational region (P<0.05), while the corresponding content of subsoil had no marked differences which suggested that construction had a larger effect on the content of total P of topsoil. Total K content in operational region was significantly higher than that in non-operational region (P<0.05), indicating that construction resulted in an increase in its content. The content of available P in operational region was generally higher than that in non-operational region, but the differences between the two samples were non-significant in topsoil (P>0.05) and significant in subsoil (P<0.05), indicating that construction had a larger effect on the content of available P of subsoil. There was a non-significant difference between the two samples in the content of available K (P>0.05), which suggested that construction resulted in limited influence on available K content.The effects of pipeline construction on soil pH values and the contents of soil organic matter, total N, total P and available N in Songnen Plain were similar to that in Daxing’anling Mountains. Compared with non-operational region, the contents of soil total K, available K and available P of operational region were higher or lower but no significant differences (P>0.05), suggesting that construction resulted in limited influences on soil total K. available K and available P.The disturbance index in the content and of distribution of soil nutrients for Daxing’anling region was higher than that of soil nutrients for Songnen Plain region. Despite the study areas, the disturbance index in the content and of distribution of soil organic matter, total N and available N was higher than that of other soil nutrient indexes.The disturbance index in the content of soil nutrients of the four ecological types was greatest for wetland, least for farmland and intermediate for forest and grassland. The disturbance index of distribution of soil nutrients of the four ecological types was dependent on soil nutrient indexes.This study highlights the importance of taking the "stratified excavation, layered stacked and layered backfill" into account in pipeline construction and provides a data base and theoretical guidance for pipeline construction and vegetation restoration.