简介:TheupwellingareaintheChangjiangEstuarywasselectedtocollectthecore,wheretheredtideoccurredfrequentlyandhypoxicexisted.Thetotalorganiccarbon(TOC),totalnitrogen(TN),biogenicsilica(BSi)andstableorganiccarbonisotopicratios(δ13Corg)weredeterminedonthe210Pb-datedsedimentcore.TheconcentrationsofTOC,TN,BSiaswellastheirsedimentationfluxeshaveincreasedtosomeextentsincethe1970s.TOCandTNfluxesincreasedabout45%,36%respectively.Theaverageδ13Corgvalueinthecorewas-23.67×10-3whichremainednearlyconstantbeforethe20century.Theδ13Corgvaluesincreasedafterthe1900s,twomarkedincreaseswereobservedfromthe1950sandthe1970s.Asimpleδ13Corgmodelwasusedtoestimatethecontributionofterrigenousandmarineorganicmatterinputsforthesediment,whichindicatedtheincreaseinaccumulationsincethe1970shasbeenalmostexclusivelymarine.Theincreasingofmarineorganicmatteraccumulation(TOC,TNandBSi)wascorrespondingwiththeincreasingoffertilizerconsumptionandtheNO3-NbudgetsfromtheChangjiangRiver.Theriverinerunoffoffertilizersandnutrientsstimulatedthealgaeblooming.Enhancedprimaryproductionresultedinanenrichmentoforganicmatterinthesediment.ThesedatasupportthehypothesisthatanthropogenicnutrientloadinghasbeenasignificantfactorontheeutrophicationintheChangjiangEstuary.
简介:Thestudydealswiththeobservationofthechangesintheelectricalactivitiesof8healthydiversinthe80mswsaturation-100mswexcursionhelioxdivebyDCG.Resultsshowedsignificantchangesinthe24hofaverageheartrate,thedecreaseofheartrateatsaturationstoragedepthanddecompressionperiodsbeing15.5%and19.7%respectively.Fortuitoussupraventricularprematurebeatsappearedin8diversandventricularprematurebeatsin5diversduringexposure.TransientischemicST-Tchangesin6diversoccurredrepeatedlyduringdivingoperations.ThediscussionputsuptheviewthattheST-Tchangeswereduetothestressreactionofthebodyinducedbythecombinedeffectofsuchstressfactorsashyperbaricpressureperse,highpartialpressureofoxgen,noiseandtheclosedrestrictedchamberenvironment.