Petroleum contamination of soil and water, and their effects on vegetables by statistically analyzing entire data set

• The soil, water, and vegetables were contaminated in the outskirts of Xi'an.
• Inputs of herbaceous plants and floating macrophytes were differentiated.
• Pollution characteristics of Brassica and Apium were differentiated.
• Effect of petroleum contamination in soil/water on vegetables was presented.
• Correlation coefficient between multidimensional data sets was calculated.

Aliphatic hydrocarbons have been used to assess total oil concentrations, petroleum sources, and petroleum degradation. In this study, surface soil, groundwater, surface water, and vegetables were collected from the outskirts of Xi'an, the largest city in northwestern China, and the samples were analyzed for aliphatic hydrocarbon contents. The concentrations of n-alkanes were 1.06–4.01 μg/g in the soil. The concentrations and the geochemical characteristics of n-alkanes showed that the low carbon number hydrocarbons were mainly from petroleum sources, whereas the high carbon number hydrocarbons received more hydrocarbons from herbaceous plants. The concentrations of n-alkanes were 9.20–93.44 μg/L and 23.74–118.27 μg/L in the groundwater and the surface water, respectively. The water had characteristics of petroleum and submerged/floating macrophytes and was found in concentrations that would cause chronic disruption of sensitive organisms. The concentrations and geochemical characteristics of n-alkanes in Brassica chinensis L. and Apium graveolens were different, but both were contaminated by petroleum hydrocarbons. The results from principal component analysis (PCA) indicated that the sorption of n-alkanes to soil particles could not be described by linear models. The distributions of n-alkanes in vegetables were positively correlated with those in soil, and the correlation coefficient was up to 0.9310 using the constructed vectors. Therefore, the researchers should pay close attention to the effect of soil contamination on vegetables.