The Geochemical Characteristics Of Suspended Particle Matter And Black Carbon In The Pearl River

Suspended particle matter（SPM）is the main carrier for terrigenous materials to enter the ocean.Through the study of river suspended matter,we can understand the weathering erosion status of river basin and evaluate the impact of human activities.Due to the unique geological background and climate weathering types of the Pearl river basin,the study on the geochemical characteristics of SPM and black carbon in the Pearl river system is typical.We collected 24suspended particle matter（SPM）sample from the mainstream of the Pearl river in 2014’s raining season.The SPM concentration varies from 8 to 944mg/L,the average SPM concentration is177.18mg/L and the SPM concentration in upstream is lower than the SPM concentration in the downstream.The experiment shows the elements easy to migrate and accumulate like Al and Fe are accumulated in the SPM,while the elements strongly to migrate like Na and K are lack in the SPM.That is because the climate in the Pearl river basin is subtropical monsoon climate,the hot and humid and rainy weather in here cause the significant chemical erosion.The enrichment of the heavy metal in the SPM is evaluated by enrich factor（EF）,EF=[X/Al]_samples/[X/Al]_upcrust.If EF=1,it means the element X comes from the continental material.If EF>1,it means the element X comes from anthropogenic input.We found the heavy metal concentration of the Beipanjiang upstream is lower than the heavy metal concentration of the Nanpanjiang upstream and the downstream of the Pearl river,and the heavy metal enrichment order of SPM is Cd>As>Zn>Cr>Cu>Pb.Enrichment situation of the heavy metals like As、Cd、Cr、Cu and Zn has great difference.The EF value of Cd and Zn and As has strong positive anomaly.The nonuniform distribution of Cr is due to the influence of the clay minerals.The Cu concentration of the SPM in the upstream is higher than the Cu concentration in the downstream of the Pearl river,it is may because of the influence of the smelting pollution of nonferrous metal mining in the upstream.The Pb concentration in the SPM is uniform in the river,that means all the Pearl river is polluted by Pb.Rare earth elements（REE）concentrations in the SPM are normalized to the North America Shale,the REE compositions of the SPM are rich in light Rare earth elements（LREE）.The REE in the SPM has positive Sm and Gd anomaly and negative Eu anomaly.The Sm and Gd are easy get out of the mineral lattices and absorb and accumulate in the SPM,and that cause the positive Sm and Gd anomaly.The Eu is easy dissolved in water so it is lack in the rock and that cause the negative Eu anomaly.The concentration of BC varies from 4.63 to 19.32mg/g,theδ¹³C value is vary from-28.4‰to-24.3‰.The concentration of BC in the upstream is high and enrich the ¹³C isotope which suggests the human activities lead to the pollution.The concentration of BC in the SPM is lower in the middle stream and downstream than the upstream due to the dilution of the river water.The coalδ¹³C value is-25‰and theδ¹³C value in oil vary from-18 to-34‰,theδ¹³C value in gas vary from-50 to-20‰.BC in the downstream enrich the ¹³C isotope which suggests the energy structure there has low portion of coal and high portion of petrol and gas.