广州城市森林及下垫面对暴雨径流与PAHs的影响

The research on storm runoff and PAHs reservoir filtration of different underlying surfaces, the forest system have of scientific significance and urgent need to aim at the frequent rainstorm and persistent rainstorm hazard in Guangzhou city. Ecohycro-influence of the different underlying surfaces will be carried out to study by small watershed technology and surface runoff field test method in the Guangzhou city and Maofeng mountain forest. Among them, the underlying surface types include impermeable cement and asphalt surface, grass surface and forest ecosystems. And the experiments included the surface runoff and PAHs flux, the soil seep to the total runoff and PAHs flux, and the removal mechanism of forest soil under storm or heavy rainfall. It aims to analysis the effects of vegetation structure on storm runoff ecology, PAHs capability in the migration and the ecological remove. Extraction of different vegetation in the city, forest ecosystems are regulated during the process of rainstorm-runoff, PAHs degradation and other ecological hydrology and geochemical laws. For the urban areas, support and scientific basis have been provided in order to deal with extreme or severe rainstorm prevention.

针对广州城市频发性暴雨及持续性大暴雨危害，城市地表不同垫面、森林系统的暴雨冲刷消减、径流响应及PAHs储滤等生态机制研究颇具科学意义。以广州市内及市郊帽峰山林区为试验研究区，采用配对森林小集水区试验技术、地表不同垫面对比径流场试验及暴雨-径流的生态水文学实验方法；开展城市小尺度暴雨特征及携PAHs的质量负荷、不同地表不透水垫面、草被及森林的暴雨地表冲刷、地表产流、壤中渗透至总径流及携带PAHs的含量、通量的对比实验研究，以及森林及灌草群落的土壤渗透控制模拟试验；解析城市下垫面、植被结构对暴雨-径流的生态学影响，研究暴雨径流水体PAHs的迁移、周转和滞留的生态学机制；提取城市不同地表植被、森林生态系统在暴雨-产流过程调蓄、PAHs去除降解等生态水文学及地球化学规律；为城市区应对极端或灾害性暴雨事件的防治提供计量的数据支撑和科学依据。

针对广州暴雨频繁易发内涝及水质毒性危害问题，基于市内及近郊帽峰山林区4年森林与不同下垫面暴雨径流及PAHs、TOC的定位对比实验测试；系统地完成了城郊小尺度上暴雨及硬质地表径流PAHs质量负荷差异解析；森林及不同地表垫面对暴雨径流及PAHs、TOC影响机制；森林水文界面层对暴雨及PAHs、TOC迁移的影响效应；森林土壤杀菌对暴雨渗透水PAHs的协同影响等的研究；其重要结果：（1）市内与近郊林区暴雨间表征在地形对暴雨雨强的影响差异，两地暴雨中PAHs组分质量浓度的差异表征出影响源的差异；市内沥青交通路面暴雨径流中4环PAHs和BghiP、BaP、IcdP质量浓度相对暴雨净增1.1—11.0倍，较市郊林区相应的高2.1—24.4倍；前者受煤燃品及交通尾气的增效影响极显著地大于后者。（2）硬质地表暴雨产流率平均达90.0%，分别是草被、针阔叶混交林、常绿阔叶林相应的13.9、24.5、27.2倍；草被、森林地表垫面年均净贮存暴雨中∑16 PAHs、TOC通量分别达94.2、96.5%和83.2、89.9%，较水泥地表相应的年均净减少93.2、96.0 %和88..0、92.8%，而草被、两类森林相应PAHs组分通量年均净减率分别高于93.0、95.0%和96 .0%。（3）常绿阔叶林及针阔叶混交林土壤30cm层暴雨渗透率分别达67.9、60.5%，土层杀菌处理后暴雨渗透水中均有12种PAHs的质量浓度高于对照；前者以BbF、BkF、BghiP、DahA、BaP、ANT、FLU、ANA及CHR高出浓度几何均值占对照的比率均大于50%，土壤杀菌渗透水PAHs的协同影响明显。（4）应对年暴雨量722.5mm至1025.1mm，常绿阔叶林、针阔叶混交林冠截留率平均为11.5、9.8%，总径流响应率分别在17.8—22.6%和21.2—25.8%间，分别贮存年暴雨∑16PAHs通量的85.4%和82.5%、年暴雨TOC通量的73.0%和81.7 %。两类森林生态系统年储滤暴雨∑2—3环PAHs、∑4环PAHs及6种PAHs代表物通量的平均分别是86.4、83.4%及79.6—87.9 %，而相应的土壤至不透水岩层储滤占比分别为68.9%、90.7%及59.4—80.1%。此对于城市暴雨内涝防治及水质保护等均有重要的科学意义。