耕作方式对农田土壤PAHs分布特征的影响

Influence of the different farming cultivation methods on the distribution features of PAHs of the land soils

以沈抚灌区为研究区域,分析了不同耕作方式对农田土壤多环芳烃分布及组成的影响。结果表明,停灌30a来,沈抚灌区周边不同耕作方式的农田土壤受PAHs污染仍较为严重,属于中度以上污染。美国环保署(USEPA)规定的16种PAHs中有15种被检测出,主要富集在表层土壤(0～20cm),质量比为3518～9140μg/kg,以高环芳烃(>4环)为主;亚表层土壤(20～40cm)中PAHs质量比显著低于表层土壤,以低环芳烃(<4环)为主。不同耕作方式对农田土壤PAHs质量比影响较大,表层土壤水田耕作下土壤PAHs残留量最高,水田-旱田轮作比长期旱田耕作模式下土壤PAHs质量比高70%;亚表层土壤中耕作下长期旱田耕作下土壤PAHs质量比最低,为1 020 μg/kg。亚表层土壤PAHs与有机质存在着显著的相关性(p<0 05)。w(IcP)/[w(IcP)+w(BgP)]和w(Fla)/[w(Fla)+w(Pyr)]分析表明,表层土壤PAHs来源除受长期污灌影响外,耕作方式和环境因素不容忽视。

The present paper intents to study the influence of the different cultivation methods on the distribution features of polycyclic aromatic hydrocarbons （PAHs） of the farmland soil. In our study, we have taken our sample soil from Shenfu sewage irrigation area of Shenyang, which used to be the largest area of petroleum sewage irrigation. The results of our studies show that the farmland soil has been remaining seriously polluted by PAHs though the sewage irrigation, even if the irrigation practice had been given up for over thirty years. The actual influence can be found that there still exists 15 PAHs out of the 16 PAHs list in the USEPA. With PAHs mainly being found existing in the surface soils （0- 20 cm） and the total PAHs varied from 3 518-9 140 μg/kg,most of which are higher rings （rings≥4）, including BbF, BgP, Icp, etc. The higher rings PAHs account for 34.1%, 43.4%, 54.3% and 49.5% respectively. In the subsur- face soils （20 -40 cm）, PAHs are found existing from the leaching of the surface soil and the total concentration was evidently lower than that of the surface, with 2-ring, and 3-ring of PAHs as the predominant compounds. The results also show that the content of PAHs in the soils is obviously affected by the different cultivation ways. In the surface soils PAHs in the paddy fields are the highest, and that in the soil of turbulent farming between dry land and paddy fields account for 70% higher than the soils of dry land. In the subsurface soils, PAHs in the dry land for long term farming are 1 020 μg/kg, which are the lowest in the research. And PAHs content in the surface soils is significantly correlated with the soil organic matter content （ r = 0.87, p 〈 0.05）, but not for the surface soils. The ratio of w（Fla）/[w（Fla） ＋ w（Pyr）] and w（IcP）/[w（IcP） ＋ w（BgP）] indicate that the PAHs in the surface soils are mainly originated from the sewage irrigation for long term, and the influence of different cul- tivation ways and environment factors are also of great significance. Thus, it can be concluded that the dry land and the turbulent farming land between the dry land and the paddy fields can promote the improvement of soil property and the degradation of PAHs. The long term paddy cultivation is actually does not avail for natural degradation of PAHs.