沉积物-上覆水界面有效铁浓度对内源磷再移动的影响

Effect of DGT-Labile Fe on Endogenous Phosphorus Remobilization at the Sediment-Water Interface

铁磷耦合关系是控制沉积物磷再移动的主导机制,基于薄膜梯度扩散(DGT)技术测定的沉积物-上覆水界面RFeP(有效态铁磷摩尔浓度比)可反映内源磷再移动潜力.本文总结了有效铁和磷及IF(磷扩散通量)在沉积物-上覆水界面的区域分布差异,探讨了RFeP、沉积特征和外部环境条件对内源磷再移动的影响机制.结果表明:①有效铁和磷浓度变化范围分别为0.08~10.22和0.02~3.35 mg/L,淡水高于海水;有效铁浓度表现为南方高于北方,有效磷浓度呈相反趋势.②RFeP和IF的变化范围分别为0.09~132.38和0.56~903.67 ng/(cm^(2)·d);RFeP表现为淡水高于海水,平原高于高原;IF则表现为淡水高于海水,高原高于平原.③RFeP与IF成反比,沉积物磷的高污染负荷或水生动植物生理活动会影响判别沉积物内源磷再移动潜力阈值(RFeP=2)的准确性.④对于不同的水域类型,沉积物中Fe^(2+)氧化沉淀或铁氧化物还原溶解均是控制沉积物磷再移动的关键过程,扰动、水生植物、微生物等外部环境条件通过改变沉积特征间接影响磷的再移动.为加深对沉积物内源磷再移动机制的认识,未来研究可关注磷再移动过程的多驱动力耦合作用机制及磷的吸附沉积速率.

The coupling relationship between iron(Fe)and phosphorus(P)is the dominant mechanism controlling P remobilization in sediment,and the molar concentration ratio of DGT-labile Fe and DGT-labile P(RFeP)determined by diffusive gradients in thin film(DGT)technology at the sediment-water interface(SWI)can reflect the P remobilization potential.The spatial distribution characteristics of DGT-labile Fe,DGT-labile P,RFeP,and apparent diffusion flux of DGT-labile P(IF)at the SWI in different regions were systematically summarized,and the effects of RFeP,sediment physicochemical indicators,and external environmental factors on P remobilization were discussed.The results showed that:(1)The concentrations of DGT-labile Fe and DGT-labile P ranged from 0.08 to 10.22 and 0.02 to 3.35 mg/L,respectively.Both had higher concentrations in freshwater than that in seawater.The concentration of DGT-labile Fe in South China was higher than that in North,while the concentration of DGT-labile P showed the opposite trend.(2)The RFeP and IF ranged from 0.09 to 132.38 and 0.56 to 903.67 ng/(cm^(2)·d),respectively.The RFeP in freshwater was higher than that in seawater,and IF showed the same trend.The RFeP in plain was higher than that in plateau,whereas IF showed the opposite trend.(3)RFeP was inversely proportional to IF,and RFeP=2 was the threshold for identifying the remobilization potential of endogenous P in sediment.However,the high P load in sediments or physiological activities of aquatic plants and benthic animals might alter the accuracy of this criterion.(4)The oxidative precipitation of Fe^(2+)and reductive dissolution of Fe oxides in sediment were always the key processes controlling P remobilization in sediment in different regions.Disturbance,aquatic plants,microbes,and other external environmental factors could indirectly affect the P remobilization by changing the physicochemical properties of sediment.In order to improve the understanding of P remobilization in sediment,future studies may focus on the coupled mechanisms of multiple driving forces for P remobilization or the precipitation rate of adsorbed P.