底泥间歇扰动-沉降过程对静止水体中生物有效磷的影响

通过模拟试验研究了底泥间歇扰动-沉降过程(每天底泥扰动10 min,然后静置沉淀1 430 min,共持续17 d)上覆水中生物有效磷(BAP)的变化规律.结果表明,每次底泥扰动后0 h,BAP含量显著升高,并在第1 d(第1次扰动)达到最高值(2.82mg.L-1);然而,随着静置沉淀时间的延长(1、6、24 h),BAP呈逐渐下降的趋势.另外,随着底泥扰动次数的增加,各采样时段(0、1、6、24 h)的BAP均明显降低,但每次扰动后0 h时的BAP含量仍远高于其它时段(1、6、24 h),这主要是由于底泥扰动导致BAPP的"瞬间释放"所致,试验过程中此时段的BAPP/BAP平均值高达95.3%.随着静置沉淀时间的延长,这一比值逐渐降低.试验开始后的第5 d,每次底泥扰动后0、1、6、24 h时的TDP达到平衡浓度(0.053、0.062、0.051、0.045 mg.L-1),而且TDP在BAP中所占的比重也逐渐降低.说明底泥扰动抑制了BAPP向TDP的转化,"延缓"了静止水体富营养化发展进程.底泥中内源磷形态分析也表明,底泥扰动后,难释放态磷占总磷的百分比由原底泥中的72.8%升至77.3%,其主要与闭蓄态铁铝结合态磷含量增加有关.说明底泥扰动促使易释放态磷向难释放态磷转化.

Sediment Disturbance-Sedimentation Process on the Bioavailable Phosphorus in Standing Water

The course of intermittent sediment disturbance-sedimentation, that sediment disturbance was for 10 min and succeeding sedimentation was for 1430 min each day over a 17-day period, was simulated to investigate the variation of bioavailable phosphorus (BAP) in overlying water. The results showed that the concentrations of BAP increased obviously at 0h after each disturbance, and the maximum concentration of BAP was reached up to 2.82 mg·L^-1 after 1 d (the first disturbance). However, the BAP gradually decreased with the sedimentation time increase (1 h, 6 h, 24 h). Moreover, at 0, 1, 6, 24 h after disturbance, the BAP gradually declined with the number of sediment disturbance increase, but the BAP at 0h after each disturbance was higher than that at 1 h, 6 h, 24 h. This may be attributed to the immediate release of bioavailable particulate phosphorus (BAPP), as a result of sediment disturbance. The average BAPP/BAP was up to 95.0% at 0h after disturbance over a 17-day period, but this value gradually decreased with the sedimentation time increase (1 h, 6 h, 24 h). At 0 h, 1 h, 6 h, 24 h after each disturbance, the equilibrium concentrations of total dissolved phosphorus (TDP) were reached after 5 d (0.053, 0.062, 0.051, 0.045 mg·L^-1), and the percentage of TDP in BAP also decreased gradually. Therefore, it is considered that sediment intermittent disturbance can accelerate the transformation from TDP to PP and hinder the development process of eutrophication in standing water. Sequential fractionation also indicates that the percentage of refractory phosphorus in Tot-P increased from 72.8% (raw sediments) to 77.3% (sediments after disturbance), attributable to the increase of concentrations of occluded Fe/Al-P. It is hopefully suggested an acceleration of transformation of phosphorus from mobile fractions to refractory fractions.