Mechanisms In Sorption Of Phenanthrene And Nonylphenol By Marine Sediments And Sporopollens With Their Fractions

Sediment organic matter?SOM?and sporopollen can constitute a significant part of natural organic matter?NOM?.The sorption of hydrophobic organic compounds?HOCs?by sediment organic matter?SOM?is critical to the distribution,transport and fate of HOCs in the environment.Considering the heterogeneity of NOM and the difference in physicochemical properties of HOCs,so far,their adsorptive interactions remains unclear.Hence,it is significant to understand the role of the molecular interactions?e.g.,hydrophobicity partitioning,pore-filling,?-? electron donor-acceptor?EDA?interactions and hydrogen bonding?of NOM with varying properties?e.g.,aromatic vs aliphatic,polar vs nonpolar,and microporosity etc.?and various HOCs in sorption process,which is beneficial to the water environmental governance and restoration.Marine surface sediments and sporopollens with their fractions were characterized by elemental analysis,CO2 and N2 adsorption techniques,solid-state ¹³C NMR,XPS and FTIR and used as geosorbents for Phenanthrene?Phen?and nonylphenol?NP?,then sorption capacities were calculated by Freundlich,PD,LPPD and DR model.Nonhydrolyzable organic matter?NHC?exhibited the highest condensation degree,since?O+N?/C of NHC is the lowest in all SOM by elemental analysis;Black carbon?BC?with the lowest H/C exhibited the highest aromaticity.It was observed that sorption capacity of Phen and NP by SOM fractions were significantly negatively correlated with their?O+N?/C;the nonlinear coefficient of Phen for SOM are correlated positively with the H/C.For sporopollen NHC fractions,their H/C were positively correlated with the sorption capacity of Phen.It is noteworthy that after removing lipids from DM fractions,CO2-SSA increased largely,however,N2-SSA decreased slightly,due to steric hindrance effect,the internal micropores of SOM is not accessed by N2 at 77 K.The organic carbon content of SOM were positively correlated with CO2-V0,but no simple relationship stands out between C% and mesopores and macropores measured with N2,indicating the micropores are mainly derived from organic matter.The sorption capacity of Phen and NP are positively related to the CO2-V0 of SOM.The ¹³C NMR solid spectra showed that NHC in the sediment were mainly composed of aromatic carbon?54.4-58.8%?and aliphatic carbon?31.3-34.0%?.Furthermore,there is a significant positive correlation between aromatic C content and the sorption capacity of Phen by NHC,but for nonylphenol,this correlation was only established at low equilibrium concentrations?Ce ? 0.05Sw?.In addition,polar carboxylic carbon contents are negatively correlated to sorption capacity of Phen and NP by NHC.The aliphatic and aromatic carbon?77.4-91.3%?constitute the main components of the NHC fractions of sporopollens,which are comparable to the structure of sporopollenin reported in the literature.The NHC structure of various species sporopollen is obviously different.The sorption capacity of Phen by sporopollens NHC were significantly positively correlated with aliphatic C,alkyl C,poly?methylene?C,and negatively correlated with polar functional group content.The composition of the surface elements of NHC in five sediments was similar by XPS spectra.The primary element was carbon,followed by oxygen,and only trace amounts of silicon were detected.The surface carboxylic acid carbon contents were significantly positively correlated with the sorption capacity of Phen and NP by NHC.FTIR spectra exhibited that the absorption peaks of methyl C-H and methylene C-H in BC were significantly attenuated,even completely disappeared,due to the combustion at 375? reduced the aliphatic structure of NHC,which well explained the lower H/C ratios of the BC relative to NHC.The above findings indicated that accessibility,micropore filling,and ?–? EDA interactions play jointly the important roles in the sorption of HOCs by SOM.For sporopollens NHC,the contents of aliphatic C,alkyl C,poly?methylene?C and polar groups were dominant factors for sorption capacity of Phen in this study.The multiple linear regression model was applied to evaluate the relative importance of the accessibility and the micropority.The importance of micropority on sorption of Phen is greater than that of the accessibility due to the higher standardized coefficient?absolute value?of micropore volume.In terms of NP,the influence of the micropority is greater than contribution of the accessibility to sorption capacity at low concentration?C_e = 0.05Sw?,at high concentration?Ce > 0.5Sw?,the reversal phenomenon was observed.