Polycyclic aromatic hydrocarbon (PAH) pollution in agricultural soil in Tianjin, China: a spatio-temporal comparison study

Representative agricultural soil samples from Tianjin, the third biggest city in China, were investigated for 16 PAHs in 2008 (n = 87) and 2012 (n = 60). Surface soil samples were air-dried and sieved. The total PAH (T-PAH) concentrations ranged from 29.7 to 4502.5 ng/g (mean value 619.9 ng/g) in 2008; and from 228.6 to 14,722.1 ng/g (mean value 1295.8 ng/g) in 2012. Bap concentrations exceeded the suggested standards at many sites. Bap and T-PAH spatial variations were represented with maps. The pollution status was also compared to many other cities. PAH soil pollution near the urban areas was found to be serious in both 2008 and 2012. Pollution at some sites became severer in 2012 comparing to that in 2008. Principal component analysis and two indicative ratios were employed to find the potential sources. The results in the 2 years both revealed that the major source of soil PAHs was coal combustion, which coincided well with the previous studies. The study added to the basic data of local PAH distribution, and pointed out a proper way for the government to reduce the pollution.