Composition And Source Analysis Of Suspended Particulate Matter POM In Baiyangdian Lake

Suspended particulate matter（SPM）is a general term for suspended particulate matter,resuspended surface sediments,and total suspended solids,which are widely present in various water bodies such as oceans,rivers,lakes,and reservoirs.Suspended particulate matter has strong mobility and complex physicochemical properties,and a large amount of particulate carbon is loaded in the organic matter of suspended particulate matter,indicating the importance of suspended particulate matter in the global carbon cycle.Meanwhile,as a carrier of nutrient transport and transformation in the water environment,suspended particulate matter has a profound impact on the management of eutrophication in lakes and the improvement of their water environment quality.There have been studies on suspended particulate matter in estuarine and marine ecosystems,but relatively little attention has been paid to suspended particulate matter in inland lake systems,and there are many gaps in the understanding of the structure,components,and sources of suspended particulate matter in lakes.In this study,the physical structure,chemical fraction,and source analysis of suspended particulate matter in Baiyangdian lake were investigated in three levels.The study aims to provide scientific reference and data support for water environment management in the region.The main findings are as follows.（1）The physical structure of suspended particulate matter in Baiyangdian lake was characterized by multi-methods,and the main components of suspended particulate matter in Baiyangdian lake were inorganic minerals,organic debris,organic flocs,algae and their debris,and microbial communities,etc.The morphology of suspended particulate matter in three types of waters:sediment surface,trench,and channel,differed greatly;SEM-EDS spectral analysis showed that five elements,C,O,Si,Al,and Ca The SEM-EDS spectroscopy showed that C,O,Si,Al,and Ca were the main constituents of the suspended particulate matter in the precipitation area,indicating that organic matter was the main component of the suspended particulate matter in Baiyangdian lake,and the elemental composition of the particulate matter was similar between different waters,indicating that the particulate matter in Baiyangdian lake originated from a specific component.The particle size of Baiyangdian lake as a whole ranged from 0.45μm to 200μm,mainly concentrated in the range of 0.45μm to 40μm,and the particle size distribution was generally the same among different waters,and the particle size decreased gradually from small to large.The spectral analysis showed that there were several functional groups in the suspended particulate matter,such as-C-H（-CH₃）,-C-O,-O-H,and C=C.The main functional groups in the suspended particulate matter were the same in the three different water types,but there were slight differences in the content.（2）The analysis of the structural and compositional characteristics of the suspended particulate matter revealed that the suspended particulate matter in Baiyangdian lake contains a large nμmber of organic matter fractions.The chemical sequential extraction of organic matter was used to investigate the fractional characteristics,content,spatial distribution,and relationship with nutrient salts of the overlying water by using three-dimensional fluorescence spectroscopy combined with parallel factor analysis.The analysis showed that four fractions of suspended particulate organic matter were extracted,and the content of each fraction was influenced by both the hydrodynamic conditions of the sediment and the surrounding environment,and the content of each fraction varied greatly between different fractions,namely WEOM(2.94 g.kg^-1)<FA(4.15 g.kg^-1)<HA(5.97 g.kg^-1)<HM(55.80 g.kg^-1).The overall spatial distribution of organic matter was gradually increasing from west to east,and the content of each component varied significantly in different water environments.The results of the graded extraction showed that the main components of suspended particulate organic matter were mainly hμmin in the stable bound state,with a high degree of organic matter hμmification but low bioavailability;the percentage of extractable organic matter components（WEOM+HA+FA）in suspended particles was 18.25%of POM,among which the WEOM component with the highest bioavailability accounted for only 3.45%of POM,and the content of the remaining three components accounted for 6.29%（6.29%）of POM,respectively.The contents of the remaining three components were 6.29%（FA）,8.50%（HA）,and 81.75%（HM）,respectively.The results of fluorescence analysis showed that the relative proportions and fluorescence fractions of different fractions of organic matter extractable from suspended particles were significantly different;there were eight fluorescence peaks in the three extracts of organic matter in the extractable state of suspended particles,mainly including protein-like fractions（W-C2,W-C3,H-C3）,fulvic acid-like fractions（F-C1,F-C2）,hμminic acid-like fractions(W-C1,H-C1,H The fluorescence fractions of fulvic acid（F-C1,F-C2）and hμminic acid（W-C1,H-C1,H-C2）were mainly endogenous tryptophan and complexine,which accounted for a relatively low percentage（18.63%）,while the fluorescence fractions of fulvic acid and hμminic acid were mainly soil hμmus imported from terrestrial sources,which accounted for a relatively high percentage（81.37%）;the results also revealed that different fluorescence fractions had different effects on N and P nutrients in the overlying water,and it is assμmed that suspended particulate organic matter has a compound effect on The results also revealed that different fluorescent fractions have different effects on N and P nutrients in the overlying water,and it is assμmed that suspended particulate organic matter has a compound effect on water quality,which needs further in-depth study.（3）Based on the analysis of organic fractions and three dimensional fluorescence spectra in the particulate organic matter of Baiyangdian lake,the sources of some extractable organic matter in the particulate organic matter were clarified,but the sources of the main organic fraction（stable bound organic matter）were not clear,so based on the Mix SIAR model,the particulate organic carbon（POC）,particulate organic nitrogen（PON）,δ¹³C andδ¹⁵N,and the particulate organic matter was traced by Bayesian model.The analysis showed that the distribution characteristics of suspended particulate organic carbon and nitrogen content in Baiyangdian lake were similar,and the overall spatial distribution was different;the overall variation ofδ¹³C andδ¹⁵N isotopes and C/N of particulate organic matter was small,and the overall level ofδ¹³C andδ¹⁵N was low,and the range of stable isotope values was gradually positive from south to north of the precipitation,so it was assμmed that the contribution of autogenous source of particulate organic matter from south to north of the precipitation gradually decreased.The model calculations showed that the suspended particulate organic matter in Baiyangdian lake was mainly from endogenous sources（59.9%）,followed by exogenous inputs（40.1%）,and the particulate organic matter was mainly from phytoplankton（28.6%-37.4%）and aquatic plants（30.2%-31.3%）,followed by terrestrial plants（22.4%-34.3%）and soil organic matter（5.8%-10.7%）.This conclusion can provide important ideas for the water environmental protection and water quality improvement of Baiyangdian lake.The regulation and control of endogenous sources can effectively reduce the contribution of autochthonous sources to particulate organic matter and further cut off its contribution to organic carbon and nitrogen in the water environment.