苦草密度对扰动引起各形态磷释放的影响

摘要

采用富营养化水体底泥培育苦草Vallisneria natans,构建密度0、20、40、100、300、450、600株·m-2的沉水植物苦草,模拟一次大风浪扰动过程扰动24 h,然后静置126 h.监测扰动和静置过程中不同密度苦草条件下水体中各形态磷含量的变化,及水体浊度的变化规律和水体中悬浮颗粒物结构.实验结果表明:苦草密度为0、20和40株·m-2的实验组扰动初浊度和水体中各形态磷含量迅速升高,并在第10 h左右达到最大值,随后下降.当苦草密度大于100株·m-2时,水体中浊度和各形态磷含量扰动前后无明显变化.随着沉水植物密度的增加,扰动所引起沉积物磷释放总量呈指数曲线降低.不同密度的苦草水体悬浮物的中值粒径在扰动后3h达到最大值,但是在扰动后期,中值粒径开始下降,并且在实验第36h达到最小值.数学模拟表明水体中各形态磷的含量与扰动实验时间和苦草密度的关系函数模拟均达到极显著水平.本实验研究说明:沉水植物密度的增加能显著抑制沉积物中磷的释放,并且当苦草密度大于100株·n-2时扰动所引起的沉积物磷释放影响不显著.扰动所引起的悬浮物的粒度变小,比表面积增大,对磷的吸附能力就越强,是水体扰动后期磷含量降低的主要原因.%Vallisneria natans was cultured using eutrophic water sediment. V. natans density of 0, 20, 40, 100, 300, 450, 600 individuals·m-2 were built, a wind-wave disturbance with 24 hours disturbance and 126 hours undisturbed course were simulated. Phosphorus concentrations in water under different V. natans density were investigated in the disturbance and disturbed course. Turbidity and configuration of particle during the resuspension course were studied. The results indicated that phosphorus concentrations and turbidity increased rapidly at the beginning of the disturbance course when the density of V. natans was 0, 20,40 individuals·m-2, and reached the maxvalue after 10 hours disturbance then decreased. There was no significant difference of turbidity and different phosphorus concentrations between the disturbance and undisturbed course when the density of V. natans was greater than the density of 100 individuals·m-2. The total phosphorus quantity during the disturbance course decreased with exponential line with the density of V. natans increased. The middle grain size of different V. natans density water body reached the maximum after 3 hours disturbance, but the middle grain size decreased at the end of disturbance course and decreased to the minimum at 36 hours during the experiment. The mathematic simulated model indicated that all phosphorus concentrations have significant correlation with time and density of V. natans. The results of this experiment suggested that increasing V. natans density could resistant phosphorus release from sediment. There was no significant effect on phosphorus concentrations during the disturbance course when the density of V. natans was greater than the density of 100 individuals·m-2. The main reason of phosphorus concentrations decrease at the end of the disturbance course was the decrease of the particle size and the increase of the particle specific surface, which increased the absorb ability of phosphorus.