Distribution And Ecological Risk Of Polycyclic Aromatic Hydrocabons In Crops Andfarmland From Parts Of Henan Province

Polycyclic aromatic hydrocarbons(PAHs) are the widespread environmental contaminants and introduced into the environment through man’s activities and natural process. There is globally increasing concern about persistent pollution and harmfulness by PAHs because of the documented carcinogenic, mutagenic and toxic in environments and biota. The paper concerned with farmland soils and crops in Henan province, which is one of the main agricultural producing provinces in China. After measured PAHs in these samples, distribution characteristics and sources of PAHs in farmland soils, uptake and accumulation of PAHs in crops were investigated. In addition, ecological risks and health risks of PAHs in farmland ecosystem were evaluated. The main results in this study were listed as follows:1、 The contents of PAHs ranged from 6.91 ng/g~106 ng/g with an average concentration of 28.6 ng/g in Huojia farmland soils, which was very low in comparison with values reported from other soils in the world and the soil standard set up by Netherlands. Assessment of PAHs in farmland soils with the N.L. Nemerow composite index and the standard of agricultural soils in Canada showed that ecological risk caused by PAHs was relatively low, which would not produce side effects to organism. 2~4 rings PAHs were dominated in soils and source apportionment from factor analysis with multivariate linear regression indicated that fossil fuel burning contributed 45.3%, biomass burning 32.9% and unknown sources 21.8%.2、 In Biyang farmland soils, the total PAHs concentrations were in the range of 45.0 ng/g~211ng/g with a mean value of 139 ng/g, which was higher than those in Huojia farmland soils and lower than the soil standard in the Netherlands and other regions around the world. Ecological risks of PAHs in farmland soils from Biyang were very low using N.L. Nemerow composite index and standard of agricultural soils in Canada. The composition of PAHs were mainly 2~3 rings PAHs with the proportions of 76.7%. Factor analysis with multivariate linear regression quantitatively apportioned sources PAHs which revealed that contributions of coal combustion and biomass burning, vehicle emission and unknown sources were 48.1%, 37.9% and 14.0%, respectively.3、 In different tissues of wheat, the content range of ΣPAHs was from13.9 ng/g to 50.9 ng/g and ΣPAHs concentrations decreased along root-stem-grain. The levels of PAHs(except leaf) in different tissues of corn had no significant differences and were higher than those in the corresponding tissues of wheat. In addition, PAHs concentrations of wheat and corn in the studied areas were significantly lower than those of plants in other region. The concentrations of PAHs in wheat and corn tissues(except leaves) were strongly associated with those of PAHs in soils, which suggested that the crops could absorb PAHs from soil. The contents of 2 ~ 3 ring PAHs in different tissues of wheat and corn were the highest, which was accordance with those in soils. And the contents of 2~4 ring PAHs in wheat gradually increased along the root-stem-grain, which showed that it was easier to migrate from the soil to plants. However, the opposite trend recorded for 5 ~ 6 rings PAHs showed that it was difficult to transfer. There were no significant differences between PAHs levels in corn tissues. In addition, the composition characteristics of PAHs in corn leaf were different from other tissues, which indicated different PAHs source with other tissues. The PAHs enrichment factors of wheat were in the order of root>stem>grain were lower than those of wheat. The log Kow of PAHs had no impact on accumulation and uptake of PAHs in wheat. The same observation was found in corn.4、 In order to investigate potential health risks to human caused by PAHs in farmland soil, incremental life cancer risks(ILCRs) incurred by ingestion, inhalation exposure and dermal contact for children and adults was calculated. The results showed that the total exposure cancer risks of PAHs in the studied solis were lower than the lower limits of acceptable carcinogenic risk(10-6). Howeverr, cancer risk of children was slightly higher than that of adults. The ingestion and inhalation are the main way of carcinogenic risk to PAHs. As for crops, corn in Huojia had the highest CRI value and exceeded the acceptable upper limit specified by USEPA, which indicated a serious potential carcinogenic risk. But the CRI values of wheat in Huojia and corn in Biyang were in the scope of the security(10-6≤CRI≤10-4), which revealed that a modertae potential carcinogenic risk.