Sediment Records Of Environmental Evolutions In The Last One Hundred Years And Discrimination Of Anthropogenic Influence In Jiaozhou Bay

For the protection and sustainable utilization of the bays,it is of great significance to explore the impact of human activities on its ecological environment.The environmental evolutions of Jiaozhou Bay are driven by both natural and anthropogenic activities,which present as the epitome of the east coast of China.The study on Jiaozhou bay has great significance to construct a model bay for the ecological environment evolution.Heavy metals,stable isotopes and rare earth elements were investigated in this dissertation to illustrate the environmental evolutions of Jiaozhou Bay in the last 100 years,to discriminate typical anthropogenic activities and quantify anthropogenic influences.A series of new results and understandings have been obtained as follows:1.The temporal and spatial variation of heavy metal contents,metal speciation,properties of sediments and anthropogenic inputs were investigated.Results indicated that the speciation distribution of heavy metals could be used to indicate the regional sedimentary environment changes.The ratios of acid soluble fraction and oxidizable fraction?F1/F3?were related to redox conditions and nutrient levels during deposition,and anthropogenic inputs could increase the proportion of labile fractions of heavy metals.Based on metal contents,metal speciation,and metal toxicity coefficient,this dissertation established the Comprehensive Risk Factor?CRF?to reflect the evolution trends of sedimentary environmental quality in different areas of Jiaozhou Bay.???.The total heavy metal contents in cores C4 and DGH located in east of the bay and estuary of Dagu River were controlled by the influence of terrigenous clastic sources,particle size and dilution of biological deposition.The relation between metal contents and sedimentary properties in core C3 were disturbed by sediment resuspension,and the total metal contents in core LSH were controlled by anthropogenic inputs.The labile fractions of heavy metals were related to the sedimentary environment changes:aerobic and high nutrient condition could induce the high ratios of F1/F3;the proportion of labile fractions of heavy metals were significantly correlated to anthropogenic contribution of heavy metals,indicating that the labile fractions of heavy metals can reflect the impact of human activities on sedimentary environment.The results of CRF indicated that Pb and Cu were in low ecological risk,Ni,Cr and Zn in no ecological risk in cores C3,C4 and DGH.The ecological risks in LSH were relatively higher:all the studied heavy metals?except for Zn which were in low risk?were in moderate-considerable ecological risk.The average CRF values in different cores decreased in the order of LSH?297?>DGH?62?>C3?37?>C4?35?.Based on the criterion of CRF,cores C3 and C4 were in low ecological risk,core DGH in moderate ecological risk and core LSH in considerable ecological risk.The vertical variations of CRF value indicated that the ecological risk of heavy metals in different cores have obvious turning points,reflecting environmental quality evolutions of sediments in Jiaozhou Bay:the CRF values in core C3 after 1950s were higher than those before 1950s,which had a potential to become moderate ecological risk;the CRF values in core C4 increased from 1966?bottom?to 1985 year,and kept relatively stable around the value of 38 after 1985;the CRF values in core DGH had an obvious promotion around 1995 year,which increased from 58?before 1995?to 66?after 1995?;the CRF in LSH were very high and fluctuated greatly,which were in considerable-high ecological risk in each layer.2.Geochemical method?background method?combining with positive matrix factorization?PMF?receptor model and lead isotope method was used for source apportionment of heavy metals in sediments of Jiaozhou Bay.Results indicated that sediments from different areas of Jiaozhou Bay were suffered from different anthropogenic activities.Geochemical method recognized that Cr in core C4 and Cu in core DGH were mainly controlled by industrial activities and agricultural activities,respectively.Results of PMF model suggested that anthropogenic?industrial?source,terrigenous clastic source and autogenetic enrichment source contributed 43%,24%and 33%of heavy metals in core C4 in the last 50 years.For core DGH,heavy metal contributions from anthropogenic?agricultural?source,terrigenous clastic source and autogenetic enrichment source were 29%,37%and 34%,respectively.Lead isotope indicated that leaded gasoline and industrial application was the main anthropogenic source of Pb in sediments,the contribution of which increased from 32%before 2000s to 56%after 2000s.Anthropogenic contributions of heavy metals obtained by background method followed the order of LSH?54.3%?>C4?32.6%?>DGH?18.6%?>C3?13.1%?.Heavy metals in core LSH were mainly from industrial activities,and those in core C3 were little polluted by anthropogenic activities.Based on the historical data about industrial and agricultural development of Qingdao,heavy metals which were indicative of specific anthropogenic activities were recognized in cores C4 and DGH.The variation trend of anthropogenic contribution to Cr in core C4 was consistent with the historical change of industrial index,which indicated that yarn and soda ash were the main anthropogenic sources before 1990s,and industrial activities such as tanning,paper making,flat glass and rough steel were the main anthropogenic sources for Cr in core C4.The variation trend of anthropogenic contribution to Cu in core DGH was consistent with the historical change of agricultural index?yield per unit area and fertilizer usage?,which indicated that agricultural contributions to Cu have increased after 1995.PMF model was used for source apportionment of heavy metals in cores C4 and DGH.The contributions from anthropogenic?industrial?source,terrigenous clastic source and autogenetic enrichment source were 43%,24%and 33%,respectively,which could be divided into three stages:anthropogenic contributions increased from1966 to 1985 year,when traditional industries grew rapidly without the constraints of environmental policies;anthropogenic contributions decreased during 1985-2005 year,when the anthropogenic disturbs to ecological environment of the bay were controlled;after 2005,anthropogenic contributions kept relatively stable.The contributions from anthropogenic?agricultural?source,terrigenous clastic source and autogenetic enrichment source were 29%,37%and 34%,respectively,which could be divided into two stages:anthropogenic contributions increase from 27%before 1995 to 39%after1995,which was attributed to the intense agricultural activities and the increased usage of chemical fertilizers and pesticides.The ratios of ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb were in ranges of 1.148-1.163 and 2.118-2.138,respectively.The measured lead isotope ratios fell on the line between the characteristic values of leaded vehicle exhaust,domestic lead deposit and the background values in the scatter plot.Results of mix-model suggested that anthropogenic contributions to Pb were 32%before 2000s,and leaded gasoline was the main source.The anthropogenic contributions increase to 56%after 2000,which were mainly from industrial application of lead.3.Carbon and nitrogen isotope indicated variation trends of terrestrial contributions to organic matter were similar to those of anthropogenic contributions to heavy metals in core C4,and the relative ratios of marine source to land source was related to spinning industry and eutrophication events in sediments of Jiaozhou Bay.The distribution patterns of rare earth elements revealed that sediments in cores C3,C4 and DGH were mainly from natural inputs,whereas in core LSH were from anthropogenic sources.Obvious differentiation between LREE and HREE was more controlled by source rocks than regional climate.?La/Yb?_N,?Ce and?Eu in different cores were influenced by organic colloid content,biogenic carbonate deposition and runoff.TOC/TN and?¹³C,which were in negative correlations in core C4,could be used to source identification of organic matters.The values of?¹³C increased accompanying with TOC/TN increased before 1985 year,when terrestrial contributions to organic matter increased from 32%to 45%;the values of?¹³C increased and terrestrial contributions to organic matter decreased during 1985-2005;after 2005,the values of?¹³C decreased and terrestrial contributions to organic matter gradually increased.The historical variations of terrestrial contributions to organic matter agreed well with those of yarn output,indicating that spinning and other related industries may important sources of organic matter for the sediments of Jiaozhou bay.In addition,the increasing trend from bottom to top of?¹³C in layer 15-27 cm?1999-2005?could be related to red tide events occurred in Jiaozhou Bay during 1997-2004.The covariation trends of?La/Yb?_N and?Ce in core C4 were related to terrestrial input of organic matter,and could reflect environmental evolutions related to organic colloid content and redox condition:when organic colloid content increased attributed to terrestrial input and the eutrophication events occurred during deposition,?La/Yb?_N increased and?Ce decreased.The values of?Ce,?Eu and?La/Yb?_N were mainly controlled by biogenic carbonate deposition?low?Ce and?Eu;high?La/Yb?_N?.The variations of?Ce,?Eu and?La/Yb?_N in core C3 reflected that there were more biogenic carbonate deposits and obvious biological activities before 1946 year in the middle of Jiaozhou Bay.The obvious low?Ce and high?Eu values in the layer 65-69 cm?1984-1985 year?could reflected the large runoff of Dagu River in 1985,when more coarse particles were transported to the estuary.Ce and Eu anomaly in core LSH were mainly controlled by sediment sources.The high fluctuations of?Eu and?Ce indicated that the sources of sediments in estuary of Loushan River were very complex,which was attributed to industrial activities.