2023年實(shí)驗(yàn)報(bào)告英文

determinationofheavymeta1sinsoilbyatomicabs

orptionspectrometry(aas)

name：xufeigroup:the3rdgroup

date：sep.20th2023

part1theintroduction

1.lthepurposes

(1)learnhowtooperatetheatomicabsorptionspectrom

etry;

(2)learnhowtodothepretreatmentofsoi1samples;

(3)getfami1iarwiththeapplicationofatomicabsorpti

onspectrometry.

1.2theprinciples

atomicabsorptionspectrometry(aas)isatechniquefor

measuringquantitiesofchemicalelementspresentinen

vironmenta1samplesbymeasuringtheabsorbedradiation

bythechemica1elementofinterest.thisisdonebyre

adingthespectraproducedwhenthesampleisexcitedbyradi

ation.theatomsabsorbultravio1etorvisiblelightan

dmaketransitionstohigherenergylevels.

theconcentrationisca1culatedbasedonthebeer-lambertlaw.

absorbanceisdirectlyproportionaltotheconcentrationof

theanalyteabsorbedfortheexistingsetofcondi

tions.theconcentrationisusuallydeterminedfromaca

librationcurve,obtainedusingstandardsofknownconcent

ration.calibrationcurvemethod：preparestandardso1u

tionsofat1eastthreedifferentconcentrations,measure

theabsorbanceofthesestandardsolutions,andpreParea

calibrationcurvefromthevaluesobtained.thenmeasurethe

absorbanceofthetestsolutionadjustedinconeentration

toameasurablerange,anddeterminetheconcentrationoft

heelementfromthecalibrationcurve.

part2themateria1sandapparatus

part3theprocedure

3.1operatingprocedureforaas

(2)installrequiredhoi1owcathode1amp.seiecti°t?±

beforeturningtothepowerandho1lowcathodelamp.then

seiectappropriatelampcurrentandpreheatfor3Omin.

(3)makesureelectricalmetertopointtozeroand

thenturnonhigh-voItagepower.

(4)selectapPropriateslitwidth.

(5)rotatemonochromatorandselectrequiredwaveleng

th.ifthepowermeteristoohighorlow,adjustnegati

vehighvoItageuntilthemeterreadsfullsca1e.

(6)adjustlightpointandwavelengthsothatthemeter

representsthemaximumvalue.

(8)injectdistilledwaterintothef1ameandcontinue

topreheattheburner.injectdistilledwaterintothe

flameaftereachsample.

(9)select)°e?±zinjectb1anksolutionintothef1ame

andadjustthemetertozero.

(10)optimizeanalysisconditionsandmeasures

tandardso1utionandsamp1es.

(12)select?°tj±beforeturningoffhighvoItage

power,decreaselampcurrentandthenturnoffthelamp,at

thesametime,a11buttonsshouldbeonorigina1positions.

(13)checktheequipmentbefore1eavingthe

laboratory.

3.2determinationofsoilsamples

(1)Preparationofextractingsolution(0.05mo1/1edta

solution)

18.6gofedtaisdissolvedwithwaterinabeaker(500

ml).thePhisadjustedto7.0usingdiluteammonia,the

mixtureisansferredintoavolumetricflask(1000m

1),dilutetothemarkandmixedwell.

(2)treatmentofsoi1samples

2.50gofair-driedsoil(60-100mesh)isputintoan

er1enmeyerflaskwithstoPper(100ml).12.5mlofedtas

olutionisadded.themixtureisshakenforIhandthen

filtered.thefiltrateispreservedforanalysis.

(3)preparationofcustandardstocksolution

0.10gofcuisdissolvedin15mlof(1:1)nitrica

cidsolution.themixtureistransferredintoavolumetr

icflask(1000ml)anddilutedtothemarkwithre-distil1ed

water.theconcentrationofthestockstandardsolutionis

100g/ml.(theconcentrationshouldbecalculatedacc

ordingtothemassofcu).theworkingcustandardsolution(1

0；Ig/ml)isobtainedbydi1uting10m1ofcustandardstoc

ksolutionto100mlwith

re-distiliedwater.

(4)plottingofthestandardcurve

0ml,1mlz2ml,3ml,4mland5m1ofcustandard

solution(10；tg/m1)areaddedrespectivelyto6vo1umetr

icflask(10ml)with1m1of5mol/1hydroch1oricacid.the

mixtureisdilutedwithre-distilledwaterandmixedwell

togive0|tg/m1z1.00|Ig/mlz2.00；tg/ml,3.00|Ig/ml,4.OO|tg/

ml,5.00；tg/m1ofcu,respective1y.theabsorbanceis

measuredatwavelengthsof3247?.thestandardcurveis

constructedbyplottingabsorbancevs.concentration.

(5)determinationofsamples

thesamplesolutionisanalyzedusingthesameprocedu

reandconditionsasforthestandardcurve.theconcentra

tionofcuisobtainedfromthestandardcurvebasedonthe

absorbance.

part4theresu1ts

4.1therawdata

4.2aasstandardcurve

4.3calculation

theabsorbanceofsampleis0.0511.

accordingtotheformulaabove：y=0.0446x+0.0024,r2=0.9

997

theconcentrationofcuinthesampleis:1.091mg/l.

part5discussion

inthisexperiment,weusetheaastodeterminecuin

soil.i1earnhowtooperatetheaasandthelimitation.

intheexperimentalprocess,standardsolutionwasprepare

dinstrictaccordaneewiththeexperimenta1requirementsand

i1earnhowtodealwiththedata,finallywegetthestandar

dcurvezthen,thesampleconcentrationiscalculatedaccor

dingtotheabsorbaneeofthesample.

ultimately,wegetthelinearformulaisy=0.0446x+0.0

024andr2=0.9997.fromaccordingtotheformu1aandtheabso

rbaneeofcuinthesampleis0.0511,wedrawthec

oncentrationofcuinthesamp1eis1.091；Ig/m1.wehave

knownthattheconeentrationoftestsamp1emeasuredby

instrumentis1.091mg/l.

wecansayourresultofexperimentissoveryaccurate

fromthestandardcurveofcuandtheva1ueofr(r2=0.0999

7),theaccuratedataisduetotheeffortsofweeveryone.

thanksforeverymerribersofourgroup.

ihavesomesuggestionsforourexperiments.first1yw

henwe11doanexperimentzwemustprepareourpre-lab

byourselvesandtranslateitintoChinese.onlydoliket

his,wecanunderstandtheexperimentwell.second1ywesh

Quidprefertosolutetheprob1emsintheexperimentrather

thanaskforta.final1y,everyoneshouldunderstandhisown

taskintheexperiment°OCIAEpNe±"nE^°ID

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2023-10-0406：03

O??Yxi±ex^pAEpNei"4aepA4nE^￡°

1.abstract

2.introduction

3.method

4.resuIts

5.discussion

6.conclusion

7.reference

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xaO?,bidEEpAexample:

doesachi1d\~sfocuscorrelatewithbarometricpre

ssure?ifso,doesitcorrelatepositivelyornegatively?

tucker(1999)hypothesizedanegativecorrelation,butthis

assertionhasneverbeentested.ourteamusedthemisha

cpttomeasurethefocusofagroupof150third-grade

students.wedividedthestudentsintothreegroupsof

50students,onegrouptookthemishacptwhenbarometrie

pressurewaslow,anothergrouptookitwhenbarometric

pressurewasneutraltandthefina1grouptookitwhenbarom

etricpressurewashigh,theresu1tsfoundthatchildr

enfocusedsignifiesntlybetterwhenbarometriepressurewas

1owthanwhen

barometriepressurewasneutralorhigh.theresuits

suggestthatwhendiagnosingadhd,practitionersshou1dgive

thecptwhenbarometricpressureisneutral.

introduction

introductio

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0Uxab?^aldEiiaDzpA°UoApAintroductionexample

introduction

inthislab,weexplorethetheoryofoptimalforagingan

dthetheoryofcentra1placeforagingusingbeaversast

hemodelanima1.foragingreferstothemammalianbehavior

associatedwithsearchingforfood,theoptima1foragingth

eoryassumesthatanimalsfeedinawaythatmaximizestheir

netrateofenergyintakeperunittime(pykeetal.1

977).ananimalmayeithermaximizeitsdailyenergyintake

(energymaximizer)orminimizethetimespentfceding(t

imeminimizer)inordertomeetminimum

thecentralp1acetheoryisusedtodescribeanimalst

hatcollectfoodandstoreitinafixedlocationintheir

homerange,thecentralp1ace(jenkins1980).thefactorsa

ssociatedwiththeoptimalforagingtheoryalsoapp1yto

thecentralplacetheory.thecentralp1acetheorypredi

ctsthatretrieva1costsincrease1inearlywithdistance

oftheresourcefromthecentralplace(rockwoodandhu

bbe111987).centralp1acefeedersareveryse1ectivewhen

choosingfoodthatisfarfromthecentralplacesince

theyhavetospendtimeandenergyhaulingitbacktothe

storagesite(schoener1979).

themainobjectiveofthislabwastodeterminebeaver

(castorcanadensis)foodse1ectionbasedontreespecies,

size,anddistance.sincebeaversareenergymaximizers(je

nkins1980,be1ovsky1984)andcentralplacefeeders(mcg

inleyandwhitam1985),theymakeanexce11enttestan

ima1fortheoptimalforagingtheory.beaverseatseveral

kindsofherbaceousplantsaswel1asthe1eaves,twigs,and

barkofmostspeciesofwoodyplantsthatgrownearwater

(jenkinsandbusher1979).byexaminingthetreesthatare

chewedornot-chewedinthebeavershomerange,anaccura

teassessmentoffoodpreferencesamongtreespeciesmay

begained(jenkins1975).thepurposeofthislabwasto1e

arnabouttheoptimalforagingtheory.wewantedtoknow

ifbeaversputtheoPtimalforagingtheoryintoactionwh

enselectingfood.

wehypothesizedthatthebeaversinthisstudywi11choose

treesthataresmallincircumferenceandclosesttothew

ater?sincetheenergyyieldoftreespeciesmayvary

significant!y,weaIsohypothesizedthatbeaverswi1Ishow

apreferenceforsomespeciesoftreesoverothersregardies

sofcircumferencesizeordistancefromthecentra1area.

theoptimalforagingtheoryandcentralp1acetheorylead

ustopredictthatbeavers,

likemostherbivores,willmaximizetheirnetrateofen

ergyintakeperunittime.inordertomaximizeenergy,

beaverswi11choosetreesthatareclosesttotheircentra1

place(thewater)andrequiretheleastretrievalcost.since

beaversaretryingtomaximizeenergy,we

hypothesizedthattheywil1tendtose1ectsome

speciesoftreesoverothersonthebasisofnutritiona1va

1ue.

methods

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hromatography

lightbulbs

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lc-10avpp1ushigh-performance1iquidchromatography

24incandescent60wlightbulbsarrangedina6*4rec

tangu1armatrix(seefigure2)

dellprecisiont7500(xeonx55502.66ghz,6gbram,64b

itwindows7professional)

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subjects

wetested150third-gradestudentschosenatrandomfrom

apoolof346applicantsfromeightlondonpublicandpri

vateelementaryschools.thestudentsrepresentedafairly

widerangeofeconomicbackgrounds.a11agreedtoparticipat

einourstudyinexchangefora25poundsgiftcertif

icatefroma1ocaltoystore.

procedure

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example:

tmr(g-a),

whereaistheaccelerationofthemass.iftheassum

ptionholdsthattheonlyfrictionaffectingthepotentiometer

wasconstantcou1ombfriction,theneachmasswouldundergo

aconstantacceleration.

thepotentiometermeasuredvoltageversustimeforthe

massesastheydropped,butthemeasurementofinterestto

uswaspositionversustime.forthatreason,aj?calibrat

he

calibration,thepotentiometer「sinitialvo1tagewas

measured.thenthestringwaspulledasetdistance(2inc

hes),andthevoItagewasrecorded,thisprocessofpulling

thestringasetdistaneeandrecordingthevoltageconti

nuedanothertwotimes(seeappendixafortheresults).to

determinethere1ationshipbetweenvoltageandposition,

thedifferencesinthevo1tageswereaveragedanddivided

bythe1ength.theresultingrelationshipwas0.9661

vo1ts/inch.

fivedifferentmasseswereusedtotesttheassumptionof

constantacceleration.foreachmass,thestringwasrolled

upontheshaftftheoscil1oscopewastriggered,andthe

shaftwasreleased,aseachmassdropped,theoscilloscope

collectedthepotentiometeri~~svo1tageversusthetime.

afterobtainingplotsforeachmass,weusedthe

voltage--positionrelationship,mentionedabove,toconv

ertthedatafromtheformvoltageversustimetothef

ormpositionversustimesquared.theresidualsofthedata

determinedwhethertheassumptionofconstantaccele

rationwasvalid.

results

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example:

results

overa11,beaversshowedaprefereneeforcertainspec

iesoftrees,andtheirpreferencewasbasedondistance

fromthecentra1place.

measurementstakenatthestudysiteshowthatbeavers

avoidedoaksandmusclewood(fig.1)andshowasignifica

ntfoodpreference(x2=447.26,d?f?=9,p&1t；.05)noa

voidanceorparticularpreferencewasobservedfortheother

treespecies.themeandistanceof8.42mawayfromthewat

erfornot-chewedtreeswassignificantlygreaterthanthe

meandistanceof

6.13mforchewedtrees(t=3.49,d.f.=268,p<.05)(fi

g.2).thetreespeciesthatwereavoidedwerenot

signifiednt1yfartherfromthewater(t=.4277,d.f.=268,P

>；.05)thanse1