黄河泥沙含量对磷迁移过程的影响研究

Suspended sediments in the Yellow River impact phosphorus transportation

磷是我国河流主要污染物质之一,泥沙含量对磷的迁移过程具有重要影响,但针对磷在沉积物-水界面的迁移机制理解尚不完全.黄河作为典型的高含沙量和高磷负荷河流,对于磷在河流介质的迁移过程具有重要研究意义.在2019年10月份选取黄河沿程18个水样采集点位和2个沉积柱采集点位,对水样含沙量、总磷含量(TP)和沉积物样磷形态含量(Ca-P、Fe/Al-P、OP)进行测量,结合2000-2019年黄河主要水文站实测输沙量、含沙量、泥沙粒径数据进行分析.从时空尺度上,尽管中游河段输沙量近20年呈显著下降趋势,但下游输沙量仍保持稳定,下游前段水体含沙量呈上升趋势.将水体含沙量与TP含量进行协同分析,下游河段水体含沙量同TP含量呈相反变化规律.对泥沙粒径进行分析,冲刷作用导致较大粒径沉积物再悬浮,这一过程对磷的迁移具有重要影响.对沉积物磷形态进行分析,IP为黄河流域沉积物磷主要赋存形态,Ca-P是IP的主要赋存形态.研究认为,当流速慢时,水体泥沙含量低,沉积物再悬浮作用弱,Fe/Al-P在沉积物-水界面迁移.当流速快时,水体泥沙含量高,沉积物再悬浮作用强,下游地区沉积物和悬浮颗粒物成为磷汇.

Phosphorus(P)is a major pollutant in Chinese rivers.Sediments affects the migration process of P at sediment-water interface,but the mechanism is not entirely clear.In the present work,18 water samples and 2 sediment core samples were taken in October 2019 along the Yellow River,a river with typically high sediment and phosphorus loads,which has important research significance for the migration process of phosphorus in river.Total phosphorus(TP)and sediment contents in water,and phosphorus contents in different forms in sediment were measured.These data were correlated with hydrological data(sediment transport,sand content,suspended sediment particle size)from 2000-2019.Sediment-transport in the middle-reaches of the river showed significant downward trend in the past 20 years,but remained stable downstream.Sediment content front downstream showed upward trend.In synergistic analysis,sediment content and TP in the lower reaches showed opposite change patterns.Resuspension of largerdiameter sediments due to scouring was found to have significant effect on the migration of phosphorus.IP was found to be the most prominent,with Ca-P being the main form of IP.Fe/Al-P migrated at the sediment-water interface when flow velocity was slow.Besides,sediment load was low and resuspension of sediment was weak.When at a high flow rate,the water body has a high sediment content and the resuspension of the sediment was strong.Downstream sediment and suspended particles become a phosphorus sink.