posted on 2024-01-18, 12:45authored byMenghan Yu, Zongle Gan, Wenjun Zhang, Caihong Yang, Ying Zhang, Aidong Tang, Xiongbo Dong, Huaming Yang
Lake
sediments connection to the biogeochemical cycling of phosphorus
(P) and carbon (C) influences streamwater quality. However, it is
unclear whether and how the type of sediment controls P and C cycling
in water. Here, the adsorption behavior of montmorillonite (Mt) with
different interlayer cations (Na+, Ca2+, or
Fe3+) on dissolved organic matter (DOM) and P was investigated
to understand the role of Mt in regulating the organic carbon-to-phosphate
(OC/P) ratio within freshwater systems. The adsorption capacity of
Fe–Mt for P was 3.2-fold higher than that of Ca–Mt,
while it was 1/3 lower for DOM. This dissimilarity in adsorption led
to an increased OC/P in Fe–Mt-dominated water and a decreased
OC/P in Ca–Mt-dominated water. Moreover, an in situ atomic
force microscope and high-resolution mass spectrometry revealed molecular
fractionation mechanisms and adsorptive processes. It was observed
that DOM inhibited the nucleation and crystallization processes of
P on the Mt surface, and P affected the binding energy of DOM on Mt
through competitive adsorption, thereby governing the interfacial
P/DOM dynamics on Mt substrates at a molecular level. These findings
have important implications for water quality management, by highlighting
the role of clay minerals as nutrient sinks and providing new strategies
for controlling P and C dynamics in freshwater systems.