北大港水库底质胶体态铬释放规律研究

Release Rule of Colloidal Chromium at the Bottom Sediment of Beidagang Reservoir

以天津市北大港水库为研究对象,选择具有代表性的2种底质,采用室内土柱试验,研究水库不同底质胶体态铬的释放规律,同时探讨了底质中铬的释放机理。研究结果表明:水库入库口、库中心底质胶体态铬释放浓度均随着孔隙体积数的增加先增加达到最大值,之后迅速变小并最终趋于稳定,分别稳定在0.067、0.034 mg/L左右。底质胶体态铬累积释放量随孔隙体积数的变化符合分段直线、存在一个拐点,在拐点前后的入库口、库中心底质胶体态铬释放速率分别为0.412 0 mg/(kg·孔隙体积数)、2.081 1 mg/(kg·孔隙体积数)和0.009 5 mg/(kg·孔隙体积数)、0.004 4 mg/(kg·孔隙体积数),表现为初期释放速率大,入库口释放速率小于库中心;而拐点后释放速率正好相反。胶体态铬累积释放总量库中心3.78 mg/kg大于入库口0.61 mg/kg,表明库中心底质胶体态铬更容易释放。底质胶体态铬向水中释放过程是脉冲式的,底质胶体对铬释放的影响与底质固体颗粒粒径大小和胶体含量有关,底质固体颗粒粒径越小,越易形成胶体态铬;胶体含量越多,胶体态铬释放量越多。

Column experiment with two typical sediments in Beidagang Reservoir of Tianjin was done to investigate the release rule of colloidal chromium in different locations of the bottom sediments of the Reservoir, and to discuss the release mechanism of chromium at the sediments. Results indicated that with pore volume number increasing, the release concentrations of colloidal chromium in both the entrance and the center of the Reservoir firstly increase and reach the peak point, then decrease dramatically and finally reach a plateau, stabilizing at about 0.067,0.034 mg/L respectively. Moreover there is a segmental straight line and a turning point corresponding to the cumulative release capacity of colloidal chromium, the release rate of colloidal chromium of the sediments from the entrance of the Reservoir is 0.4120mg/（kg ·pore volume number）, which is one quarter of that from the center, 2.081 1 mg/（kg·pore volume number） in the previous of turning point. On the contrary, following the turning point the release rates of colloidal chromium of the sediments from both sites go down sharply but latter rate is much more faster than the former one, 0.009 5 mg/（kg·pore volume number） and 0.004 4 mg/（kg· pore volume number） partly. The accumulative release capacity of colloidal chromium in the center of the Reservoir is 3.78 mg/kg, greater than 0.61 mg/kg in the entrance, suggesting that colloidal chromium in the center is easily released. The release of colloidal chromium is pulse type,the influence of chromium release at the bottom sediments is related to the particle size of the sediments and colloid content, the more smaller the particle size of the sediments is, the more easier colloidal chromium forms; the more colloid content is, the more the amount of release of colloidal chromium is.