Spatial variations of hydrocarbon contamination and soil properties in oil exploring fields across China

Successful site remediation is critically based on a comprehensive understanding of distribution of contaminants, soil physico-chemical and microbial properties in oil contaminated sites. One hundred and ten topsoils were sampled from seven typical oil fields in different geoclimate regions across north to south China to investigate the spatial variances of oil contaminations and soil parameters. Oil concentrations and compositions, soil geochemical properties and microbial populations were analyzed and statistic analysis methods were used to analyze the spatial pattern of soil variables. The results indicated that oil contaminations were serious in most oil exploring areas in China, especially with high levels of polycyclic aromatic hydrocarbons (PAHs) from petrogenic origin. Ordination analyses indicated a relatively distinct spatial pattern that all soil samples grouped mainly by geographic locations, instead of distributing along contamination or other geochemical variable gradient. Microbial populations were found to be statistically positively correlated with soil nitrogen, phosphorus and water content, and negatively correlated with salt pH and soluble salts (P<0.05). This study provided insights into the spatial variability of soil variables in hydrocarbon-contaminated fields across large spatial scales, which is important for the environmental protection and further remediation in oil contaminated sites according to local conditions.