Sorption and distribution performance of organophosphorus compound (Adenosine 5'-monophosphate)on marine sediments.

In this paper, the kinetics and thermodynamics of Adenosine 5'-monophosphate (AMP) sorption on the sediments obtained from the Yangtze River Estuary and adjacent areas were studied, in combination with the effects of the sediments' properties and media conditions. The kinetics curves could be described by a two-compartment first-order equation, and the equilibrium isotherms fitted well with the modified Langmuir and Freundlich models. The analysis of organic phosphorus (OP) fractions changes after sorption indicated that the contents of exchangeable or loosely sorbed PO increased most significantly. Higher organic matter (OM) of the sediments were favorable for the sorption ability. It was also found that the content of OP and OM in the sediments showed an obvious positive correlation, indicating that organic matter rather than Fe/Al oxides played an important role in the migration of OP in the Yangtze River estuary and its adjacent area. Temperature, salinity and pH of the media influenced the sorption of AMP significantly. Increase of temperature was of benefit to the sorption of AMP, which was a spontaneous and exothermic process according to the calculations of the thermodynamic parameters. The sorption capacity was higher at a moderate salinity in the range of our study. With the pH changing from 3 to 10, the sorption capacity exhibited as a "U-trend" curve.

Diagenesis of sulfur, iron and phosphorus in sediments of an urban bay impacted by multiple anthropogenic perturbations.

Solid-phase speciation and porewater chemistry measured by the diffusive gradients in thin films (DGT) technique were used to understand the diagenesis of sulfur (S), iron (Fe), and phosphorus (P) in sediments of Jiaozhou Bay (China), which has been impacted by multiple anthropogenic perturbations. Despite water eutrophication, sediments of the bay are low in organic carbon and sulfide, but high in unsulfidized Fe(II). Dissimilatory iron reduction (DIR) prevails in sediments of the bay, and there is no evidence for responses of S and Fe diagenesis to the water eutrophication, which is largely attributable to unique depositional and diagenetic regimes in association with multiple anthropogenic perturbations. Good coupling of porewater Fe2+ and P in the porewaters suggests that P mobilization is driven mainly by DIR. Low Fe2+/P ratios in porewaters imply that oxidative regeneration of Fe oxides within the upper sediments is incapable of efficiently scavenging upward diffusing P.

Effect of black carbon on sorption and desorption of phosphorus onto sediments.

The sorption behavior of phosphorus onto sediment was investigated with the addition of BC derived from incomplete biomass combustion (PC). The sorption kinetic curves of phosphorus onto PC and sediment could be described by a two-compartment first order equation, and the sorption isotherms fit the Freundlich model well. With increasing amounts of PC added, the sorption capacity increased while the HI did not change much. The distribution of phosphorus forms showed that CaP (ACa-P plus DAP) constituted the highest fraction in the sediment samples. Throughout the sorption process, CaP and OP changed very little, but the Ex-P and FeP increased obviously, and the presence of PC made this increase more significantly. The high specific area and the presence of iron and aluminum, as well as the modification of the sediments surface properties, make the addition of PC be favorable for the sorption of phosphorus onto sediments.

In situ, high-resolution DGT measurements of dissolved sulfide, iron and phosphorus in sediments of the East China Sea: Insights into phosphorus mobilization and microbial iron reduction.

Dissolved sulfide, iron (Fe), and phosphorus (P) concentrations in sediments of the East China Sea were simultaneously measured in situ by diffusive gradients in thin films (DGT) technique. The results, by combination with solid-phase Fe speciation, were used to characterize the interplays of Fe, S and P. Diverse distributions of dissolved sulfide among the sites are attributable to highly dynamic diagenetic regimes and varying availability of labile organic carbon (OC). The DGT technique provided high-resolution evidence for coexistence of microbial iron reduction (MIR) and sulfate reduction in localized zones, and for Fe-coupled P mobilization. Measured Fe2+/P ratios suggest that Fe2+ reoxidatiion at the oxic zones can serve as an efficient scavenger of P. Empirical estimation indicates that MIR plays an important role in anaerobic OC mineralization in the sediments, which is a combined result of low availability of labile OC, high reactive Fe content, and unsteady diagenetic regimes.

[Surface Property and Sorption Characteristics of Phosphorus onto Surface Sediments in Sanggou Bay].

Kinetic curves and isotherms were investigated to study the sorption mechanism of phosphorus onto the sediments of Sanggou Bay, together with the surface charge properties of sediments and the forms of phosphorus studied. The results showed that the sorption including a fast process and a slow one, and could be described by a two-compartment first order equation. The thermodynamic isotherms were well fitted with a modified Langmuir equation. The maximum adsorption capacity was larger in summer than in spring, and the smaller particle size was favorable to the sorption. The maximum adsorption capacities (Qm) were 0.0471-0.1230 mg x g(-1), and the zero equilibrium phosphorus concentration (EPC0) of the sediments ranged from 0.0596 mg x L(-1) to 0.1927 mg x L(-1), which indicated that the sediments from Sanggou Bay were sources of phosphorus. Inorganic phosphorus (IP) was the main form of total phosphorus (TP). The contents of exchangeable or loosely absorbed P and Fe-bound P increased significantly in the samples after sorption. The sorption process involved physical sorption and chemical sorption, with the former being the predominant.

[Influence of SDBS on sorption behaviors of heavy oil on Jiaozhou Bay sediment].

Sorption behavior of heavy oil onto Jiaozhou Bay sediment in the presence of anionic surfactant sodium dodecylbenzene sulfonate (SDBS) in artificial seawater was studied. Batch method was used to investigate the kinetic and thermodynamic behaviors. The results showed that the sorption rate and sorption capacity increased with the increasing initial concentration of SDBS. The sorption rate equations could be described by the pseudo-second-order model. The sorption isotherms were in good agreement with the Freundlich model. Higher salinity and lower temperature of the medium were favorable to the process. In the temperature range of 283-308K, the values of thermodynamic parameters were estimated, such as the deltaG(theta), deltaH(theta), deltaS(theta) which had significantly negative values in the presence of SDBS than those without SDBS. The sorption process was a spontaneous and exothermic reaction, and the randomness was decreased during the process.