Fate and transport of Pb/Cd/P at the sediment-water interface

沈婷婷

11653022

博士

土木工程

唐圆圆

2020-11-11

2020-11-11

南方科技大学

深圳

Sediment is considered as the largest long-term sink and a potential source forenvironmental pollutants in aquatic ecosystems, and critically affects the transport andfate of the contaminants. Once the pollutants were carried by water current into theriver, some of them can deposit on the surface of the sediment by adsorption,precipitation, and flocculation. Furthermore, the bounded contaminants can bereleased from sediments to overlaying water with the change of the benthic and waterenvironment, causing the long-term pollution of river system. Thus, it is necessary andimportant to understand the mechanisms of contaminant transport in river system,particularly at the sediment-water interface, which could provide fundamentalknowledge for appropriate strategic development to reduce long-term river pollution.It is common that heavy metals and nutrients are usually co-existing in natural riversystem, causing consequent environmental risks. Furthermore, the time for pollutantdischarging into the river system always varies a lot among different activities. In thisregard, the contaminants, which enter river system in the previous step, may be easilyadsorbed onto sediments and become a part of sediment components, thus alter thephysical/chemical properties of the sediments. Consequently, the transport and fate ofcontaminants, which enter the river system subsequently, may be also influenced bythe contaminants already attached on sediments. However, few studies have reportedthe interactions between the contaminants under different discharging sequence.Therefore, it is imperative to systematically investigate the fate and transport ofcontaminants at the sediment-water interface, and to study the effect of dischargingsequence.Therefore, in this work, heavy metals such as Pb2+/Cd2+ and nutrient like P wereselected as target contaminants, while the collected sediments as well as the Fe-/Alivmineral phases were used to represent the river sediment. A series ofexperiments werecarried out and can be divided into the following two parts. First, the adsorptionbehavior of Pb2+ and Cd2+ was explicated on the surface of the P-loaded sediment, toexplore the effect of the P loading on the transport of heavy metals at the sedimentwater interface. Second, the transport behaviors of Pb2+ and P were investigated underdifferent enter sequential orders of Pb2+ and P at the interface of sediment minerals(Al-substituted ferrihydrite FA-15/goethite G/Al-substituted goethite GA) and water.For the P loading sediments, the adsorption amounts and retention ability of Pb2+ onsediments were significantly enhanced due to the high affinity between Pb2+ and P.While the transport of Cd2+ was slightly affected by the P loading on river sedimentsdue to the weak interaction between Cd2+ and P. Furthermore, the release processes ofP loading from sediments were found to be remarkably inhibited by the transport ofPb2+. For the adding sequence of Pb2+ and P, results showed that the pre-adsorbed Pon sediment minerals (FA-15, G and GA) enhanced the adsorption amounts of Pb2+remarkably. At the same time, the retention ability of Pb2+ on sediment minerals wasreinforced by the presence of P. For the fate and transport of P, the pre-adsorbed Pb2+seemed to have little effect on the following adsorption of P on FA-15 and G. Whilethe pre-adsorbed Pb2+ on GA was beneficial to the following adsorption of P. For therelease process of P from sediment minerals (FA-15, G and GA), the presence of Pbintensely prevented the P release. Furthermore, the XPS results confirmed the differentternary complexes among Pb, P and O, which were formed on sediment minerals underdifferent adding sequence of Pb2+ and P. In addition, the substitution of Al in differentsediment minerals showed different effects on Pb2+ and P transport.

river sediment lead cadmium phosphorus fate and transport ferrihydrite and Al-substituted ferrihydrite goethite and Al-substituted goethite

英语

独立培养

南方科技大学

Shen TT. Fate and transport of Pb/Cd/P at the sediment-water interface[D]. 深圳. 南方科技大学,2020.