The Characteristics Of Particulate Organic Matters And Their Adsorption Of Antibiotics In The Coastal Soils And Sediments In The Yellow River Delta

Antibiotics have been of concerned globally as emerging pollutants in the marine and coastal environments.Soil organic matter plays an important role in sorption of antibiotics.Particulate organic matter?POM?is a biologically and chemically active fraction of soil organic matter.Free particulate organic matter?fPOM?is found between aggregates while intra-aggregate particulate organic matter?iPOM?is incorporated and physically stabilized within aggregates.The difference in position within the soil and the protection of soil aggregates leads to properties that differ in stability and composition.Particulate organic matter has a strong capability in enriching soil pollutions.10 coastal soil samples were collected from the Yellow River Delta and Hainan Dongzhaigang and were separated into different fractions of POM and mineral-associated soil organic matter?mSOM?with the method of wet sieving and density separation.The POM and mSOM were measured for organic carbon,black carbon,mineral components,oxides content and trace element,morphological characteristics and volume distribution,organic group components and contents and stable carbon isotopes.Levels and distributions of veterinary antibiotics both in the sediments of the Bohai Sea in China and in the surface and ground river water surrounding Bohai Sea were investigated in this study.The results are expected to be useful in understanding the properties of particulate organic matter and providing the basis of study of the antibiotics sorption onto POM.The sorption of antibiotics onto POM was studied both by batch experiment and Nano-scope characteristics distribution of antibiotics in the POM.The main results were summarized as follows:particulate organic matter is organic mineral complex which comprised by organic matter and mineral.The organic matter in soil aggregates could be fractionated into free particulate organic matter?fPOM?on the surface of macro-?micro-?aggregates,intra-macro-?micro-?aggregate particulate organic matter?iPOM,250-2000?m?and mineral-associated soil organic matter.Contents of fPOM,iPOM and mSOM were quite low in the barren land,but soil organic carbon content increased significantly in the three types of SOM in the saltmarsh where some halophytes began to grow,reaching as high as 410.0 g/kg,98.8 g/kg and 18.8 g/kg,respectively.When saltmarsh was reclaimed into upland,the rising trend of the three types of SOM leveled off.The POM?including f POM and iPOM?accounted for only20%or below of the organic carbon in the barren land,for 41.8%⁷5.2%in the saltmarsh that had some halophytes growing,and for 54%in the upland.The black carbon was an important component of soil organic matter and the content of it was in positive relationship with the content of organic carbon in different SOM fraction.The main primary mineral was quartz,and main secondary mineral was hydromica in the fPOM.The content of Al₂O₃ of mSOM was higher than that of POM while the content of CaO of intra-macroaggregate POM was higher than that of fPOM and mSOM.There was no significant difference among the content of MgO of different POM fraction and mSOM.As for trace elements,except for Cr and V,fPOM had stronger enrichment capability for trace elements such as Ni,Co,Cd,Cu,Zn and As than iPOM and mSOM.Combining the results of?¹³C demonstrated that the growth of halophytes in the saltmarsh?wetland?increases the content of POM and Cultivation of corn and wheat lowers the relative proportion of active carbon pool,but enhances stability of the so carbon pool.In the humification process of POM,their content of aliphatic carbon decreased while aromartic carbon increased.Their morphological regularized,pority and special surface areabecame increased and volumes decreased.This processes were affected by plantation types,residues and sources.FPOM and iPOM had different morphological characteristics,volume distribution,porosity and special surface area and so on.The results showed that the number of iPOM was more than fPOM,and most of them were regular particles while the fPOM were lignin shaped with relative high volume ratio.The number and volume ratio of macro-aggregate surface fPOM were lower than those of micro-aggregate fPOM.The macro-and micro pore of fPOM were abundant,which would provide numerous sorption sites.?2?A total samples including 139 Bohai Sea and estuarine sediments and 195riverine sediments and surface and ground water samples from the downstream to neritic sea were analyzed for seventeen antibiotics.The results revealed that the main polluted antibiotics were tetracyclines,Quinolones and macrolides and the highest antibiotic concentration of 4695?g/kg of oxytetracycline occurred in the estuarine sediment from Ziya New River.The Bohai Bay and Laizhou Bay,as well as the surrounding estuaries had higher concentrations of antibiotics.However the Liaodong Bay had few antibiotics detected in contrast to the high antibiotics concentration presented in its surrounding estuaries.The spatial heterogeneity of antibiotics of sediments was affected by antibiotics sources and properties of sediments and waters.?3?On the basis of characteristics of POM and the investigation of antibiotics pollution in the Bohai Sea and surrounding estuaries sediments,we went further study on fractionation and sorption of antibiotics in different soil organic matter fractions.The results showed as follows:In the aliphatic carbon dominant POM sorption process,the aromatic carbon played restrained role,reversely in the aromatic carbon dominant POM sorption process and played an important role in desorption hysteresis.FTIR analysis results showed that Oxygen containing functional groups such as hydroxyl,carboxyl played an important role in the sorption mechanism.Further study conducted OTC and CFC sorption in the fPOM from different sources.The regression equation between properties of fPOM and K_d value were:OTC K_d=0.139×SSA+0.035×MSS+0.4×CEC+0.14×Al₂O₃+0.11×Carbonyl-C+0.36×Aliphatic-C+0.12×Aromtic-C+0.028×Carboxyl-C and CFC K_d=0.12×SSA+0.09×MSS+0.18×CEC+0.15×Al₂O₃+0.12×Carbonyl-C+0.03×Carboxyl-C+0.13×Aliphatic-C+0.14×Aromtic-C.The content of Aliphatic-C,CEC and Al₂O₃ were important to antibiotics sorption in fPOM.The sorption of OTC in fPOM was affected by environmental factors.fPOM had a stronger sorption capacity of CFC than OTC.The main mechanisms of sorption OTC and CFC in fPOM were cation exchange,electrostatic interaction,hydrophobic interaction and mesoporous filling in different pH solutions.And saline ions competed to sorption sites with OTC and CFC in fPOM.The thermodynamics adsorption of OTC was feasible,spontaneous,entropy increasing and endothermic in nature.Lastly,Nano secondary ion mass spectrometry study of carbon isotope labled CFC sorption in fPOM and organic matter fraction showed that organic matter of fPOM played a preferential role in the CFC sorption process,and there were no significant difference in the fPOM profile sorption of CFC.