| PAHs (Polycyclic aromatic hydrocarbons and PAHs) refers two or more than two benzene class of organic compounds, it is ubiquitous persistent organic pollutants in the environment, mainly derived from volcanic eruptions, forest fires and other natural processes and human activities such as petrochemical industry, coal. Because most PAHs are strong "three" effect, which threatening the ecological safety of soil and human health. Soil PAHs pollution repairation has become a hotspot in research of environmental problems.This study through the simulation of natural fine root turnover situation of subtropical broad-leaved forest, select fine goldenrain tree root, and adopt the artificial add the root method, then mixed soil PAHs pollution gradient levels (L1< L2<L3), For a 180-days trial. Determination of the concentration of soil PAHs can be extracted, the content of soil total organic carbon (TOC) and the content of soil soluble organic carbon (DOC). Contrast analyzed respectively under three different pollution levels, the removal efficiency of soil pyrene with no root treatment and add the root treatment. Studied the influence of pyrene pollution in the process of fine root turnover effects on soil properties. Reveals the correlation between TOC, DOC and the amount of PAHs degradation. Results will be able to gain a better understanding of fine root turnover affect the repair effect of soil PAHs, and provideing a reference for phytoremediation to find effective improvement method. Besides, providing theoretical basis of draw up fast, economic, effective and safe soil PAHs pollution repair for the practical technology. Through research and analysis, this paper draws the following basic conclusion:1. The effects of add fine root for pyrene contaminated soil repair.Under the three level of the pollution, the soil pyrene degradation rate in the two kinds of treatment both the add the root and no root are increased with the extension of time, and PAHs in soil degradation trend under the three pollution levels after 180 days is consistent, both for L2>L1>L3. The average soil pyrene degradation rate of the treatment of no root under the L1, L2, L3 pollution level are 45.42%,55.95% and 45.42% respectively, the average soil pyrene degradation rate of the treatment of add the root under the L1, L2, L3 pollution level are 56.78%,68.20% and 34.19% respectively, soil pyrene degradation rate of treatment of add root were significantly higher than that of treatment of no root under three pollution level (P<0.05), increased by 11.36%,12.25% and 12.25% respectively. This fully embodies the fine root turnover repair effect of soil pyrene,also suggests that PAHs contaminated soil itself has certain natural repair capacity, and the appropriate concentration of PAHs is good for its degradation.The soil pyrene repair efficiency under different periods is not the same. In the treatment of no root, the largest pyrene degradation rate of soil under the L1, L2, L3 pollution levels are at 90 days,60 days and 90 days respectively, is respectively 11.04%,16.39%,6.68%, which is associated with different pollution levels of microbial degradation activity. But in the treatment of add root, the largest pyrene degradation rate of soil under the L1, L2, L3 pollution levels are both at 15 days, is respectively 13.44%,17.91%,10.96%, this may be related to the newly dead fine roots decomposition.2. The influence of add fine root on the pyrene contaminated soil properties.The TOC under all of three kinds of pollution levels are higher than control treatment(P<0.05)。In the treatment of no root, TOC under the L1, L2, L3 pollution level higher than control treatment 35.07%,32.93%,43.72% respectively; in the treatment of no root, TOC under the L1, L2, L3 pollution level higher than control treatment 50.32%,49.64%,70.22% respectively. TOC in the treatment of add root is higher than the treatment of no root. The treatment of soil organic carbon under L1, L2, L3 pollution levels higher than that the treatment of no root 14.37%,14.97%, 23.58% respectively.The soil DOC content under the three pollution levels changing with time volatile, in the treatment of no root, DOC at 15th and 180th days are higher than the controlled treatment(P<0.05). Soil DOC under three pollution levels of different treatment shows:add root treatment<no root treatment, and in the treatment of add root, DOC at 15th、30th、60th、180th days are lower than the treatment of no root (P<0.05).Correlation analysis was carried out on the pyrene repairing effect and soil properties, the results shows that in the treatment of no root, the amount of TOC and soil degradation pyrene in the L2 pollution level are very significant positive correlation(P<0.01), the amount of DOC and soil degradation pyrene under the L2 pollution level have no significant correlation(P><0.05), the others have no significant correlation(P>0.05). |
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