Temporal and Spatial Distribution of Elements in a ...

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nk to 316.2 km due to excess reclamation f Wang Sum—. in and Dou Hongshen,1998). Th e Wan gling River is a small stream wining its way along the ...
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Vo1.23 No.1  

CHI NESE JOURNAL OF  GEOCHEM I STRY 

Tem poral  and Spat i al  Di st ri but i on of El em ents  i n a Sm al l  Cat chm ent,and Bufer Funct i on  of W etl and i n Longgan Lake,Chi na水   wu  Ya nho ng(吴艳 宏 )¨,WANG  S umi n(王 苏 民)¨,R.W.Ba r t t ar be e  ,   a nd   ZHU  Yux i n(朱 育新 )  ’   1)( Ke y  Lab or at or y  o fL ake   S e di men t at i on  an d  Env i r onme nt,Nan j i ng  I n s t i t ut e   f Ge o o gr a phy   an d  L i mno l o gy,   Chi n es e   Ac ade my  o fS ci e nc e s,Na  ng  21 00 08,Chi n a)   2)(ECRC,De par t en m t  f Ge o o ra g ph y,Uni v e r s ty i   Co l l e ge   fL O On ̄n,26  Be d for d  Wa y,L on don,WC1HOAP,£ 7 .尼 )  

Abst r act:Wet l and i s   t he  con j unct ion  o f   l ake  and  t er r ene   wher e  human  act i vi t i es   ar e  c oncent r at -   ed.Fr om  t he  vi ewpoi nt s   f  o mat er ial  t r n spor a t   n d  a cy cl i ng i n  t l l e  t er r ene- l a ke  s ys t em,we la t n d  i s 

t he  buferwher e  sa n d  n d  a mud.heav y met al s,p ol l ut ant s a n d nut ient r s  a r e t ar r i e d. I n  t l l i s   pa-   pe r.we  pr o vi de  a  cas e s t udy bas ed on t l l e  t e mpor a l  a n d s pa t i l di a s t r i but ion o f e l ement s i n t l l e  W angl i ng  Ri v er   cat chment.a  s mal l   s ub. cat chment   of   Longga n  La I 【 e  i n  t l l e  mi dd l e  r ea c hes   f  o t l l e 

Ya ngt z e Ri v er.we   ha ve  f ound  t l l at   wet la nd  ca n  bu f er   ma j or   hea vy  met al s   such  a s  Cr,Cu,et c.   si gni ica f nt lv.but  ha s  a  l i t t l e  bu f er   f unct ion  t o  some  act ive  el ement s  such  s  Fe a  a nd  Mn,whi ch  ar e  lways a   ra t ns or p ted  s  s a ol ut i ons . Hum a n  act i vi t i es  not  onl y i nf luence  t l l e di st r i but i on of   e l e-   ment s.buta lsoweakent he  bu f e rf unct i ono f wet la n d.I nt ensi ve  huma na ct ivi t i esi nt he  Longga n  LaI 【 e   ar ea  i n  t he  pa s t70 ye ar s   hav e  been  r ecor ded  i n  s ream .wet t la n d  n d  a l ake  s edi ment s ,es pe-   ci a l l y  t l l e  hum a n act i vi t y  event s s uch  s  a def or es t i ng   and  r ec l ai mi ng  on  a  l a r ge  s ca le  i n 1 958 a n d 

t he 1 980’s.Human  ct a i vi t i es   can s ed t he i ncr ea s e o f  sedi ment at i on r at es  s i nce  t l l e 1 950’s,a s  wel l  a s  t l l e  i ncr ea se  of   el e ment s ’concent rat i ons . The  ext ens i ve  use  f  o f er ti l i z er s  a n d pes ici t de s  s i nce  t he  1960’s  ha ve  l e d  t o  t l l e  i ncr ea s e  f  o t ot al   P  concent r at i ons.I ncr ea si ng  SO,emi ss i on  ac-  

ce l er at e  t l l e  pr oces s   f  o cat i on  e xcha n ge   i n  s oi l.a n d e nha n ce  t l l e  l eachi ng  f  o Mn  out   f  o s oi I s.Per -   manent   s t or ing o f  wat er  caus es t l l e  s oi l  gl eyi icat f i on t l l at  a ls o i nt ens i f i e s t l l e  l eachi ng o f  Mn.  

h es T e  re  a t wo  maj or  r ea sons  f or  t he obvi ous  i ncr eas e o f ma n ga n ese  concent ra t i ons  i n r ecent   20  yea r s  i n  Long ga n  La I 【 e.I nt ensi ve  huma n  act ivi ies t   s i nce   h e  t 1950s’have  i nt ens i f i ed  he  t o pul p a -   t i on  i n  t l l i s  r egi on  n d  a t hus  des t ro y r d  t e he   bu f er   f unct i on  f  o wet la n d.  

Key words: c onc ent rat ions  of  el ement s; t emporal  and s pat i al  di s t ri but ion; wet l and,   buf e r;hum a n  ac t i vi t y;Longgan  Lake 

h ke sedi ment s  are commonl y use t o st udy l ake envi ronment  evol ut i on and gl oba l cl i mat e a n d 

envi ronment  change a n d reconst ruct  human— nat ur e i nt eracti on hi s t or y.Lake sedi ment s s ourced f rom  l k e cat a chment  a re t he  carr i er  of   vari ous envi ronment al  i nf or mat i on.whi ch have  recorded bot h nat u—   ra l change a n d ant hr op o geni c i mpact.Due t o t he compl i cat ed physi ca l a n d chemi ca l pr ocesses  dur -   i ng mat er ia ls bei ng del i vered f r om t h e cat chment  t o t h e l ake. mi xed i nfor mat i on of  envi r onment al   pr oxy may be cont ai ned i n lake sedi ments。whi ch may lead t o a mi sunder st andi ng of envi r onment  

cha n ge.Thr ough  h e compar t i son of  luvi f l ,wet a l n d and l a acust ine sedi r ment s,st udy on t empor al   n d  a spat i l di a st ri but i on of  mater ia ls  i n t h e cat chment。a n d a na lysi s on t h e pr o cess  of   mat er i l t a r ansport。   ISSN 1Ooo- 9426 

Thi s   wor k  i s   s up poaed  b y  t he   p r o j e c t   f r om  Nat ion al   Na t ur a l   Sci e nc es   Fu nda io f n  o f   Ch i na(Gr a nt   No.4030 2022)a nd   t he   Kn s w1 .  

ed ge ・ I nnov a t i o n  Pr o j e ct   o f   Chi ne s e   Aca de my   o f   Sc i enc e s(CAS)(Gr ant   No s .KZCX1 一 SW. 1 2  a nd  KZCX2- 302).  

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CHI NESE JOURNAL OF  GEOCHEM ISTRY 

Vo1 .23 

i t  i s  usef ul   t o unde ̄t and t he si gni icance of  f envi ronment al  pr oxy  and  t o di s t i ngui s h t he  huma n  i mpact   fr om t he envi r onment l r a ecor ds.  

We land f  i s   he t   co nj unct i o n  o f   l ake   n d  a t er r ene   wher e   human  a ct i vi t i e s   a r e   conc ent r at ed.Fr o m  h e vi t ewpoi nt s  of mat er ia l t rans port  and cycli ng i n t h e t er r ene— l ake r esponse envi ronment  sys t em ,   wet la n d i s  t he bufer  wher e sand a n d  mud,heavy met ls,p a ol l uta nt s  and  nut ri ent s  ar e t ar ri ed.Bas ed  on t h e bufer  f unct ion of  wet l and,ma n —const r uct ed wet l ands  have been devel oped al l  over  h e worl t d 

t o  s ubt r ac t  or g ni a c  ma t t er,ni t r og en,phos phor ous  a nd t o xi c  met ls a  f r o m was t e  wat e r(Ree d a nd  Br own。1 992).The r e   i s   hi her t to   lmos a t   no   r e por t  o n  t he  pur if ic at i on  pr oc es s  a n d  t he   me cha ni s m  of  

we t l n d  a f o r mat i on(Br i x,1 994;Ta n ne r   e t   1.,1993;Br a ee n,1 990).How  ca n a nd  ho w do es   he t   nat ura l wet la n d act  as  a  buf fer  t o t h e l k e?  a In t hi s l i ght  of  t he t empor l and spat a i l di a st ri but i on of  sel ect ed el ement s i n a smal l  sub— cat ch—   ment  of  Longga n  Lake,t hi s st udy t ies r  t o s hed much l i ght   on how  mat er ia l ar e t ra ns or p ted  f rom t h e  sour ce t o t he l k e。how huma a n  act i vi t i es i mpact  t he di st r i but i on of  el ement s and what  t h e bu f er  f unct i on of  wet l n d i a s.  

1 General  descri pt i on  of   t he area  st udi ed 

Long ga n  La ke(29。 52 一30。 05  N,11 5。 55  一11 6。1 7  E)i s   l oc at ed  i n  t he   bo r de r   ar ea   bet wee n  Sus ong  Co unt y,Anhui  Pr ovi nce,and  Long gan  Far m,Hubei   Pr ovi nc e,whi c h  wa s   t he   ma j or   par t   of   he t   Peng li z e   pa l e o— l a ke   i n  he t   hi s t or y(Zhu  Hmhong   n d  a Zhang   Be n,1 997)(Fi g.1).I t   i s   a   wa t er —   passi ng l ake wi h an average wat t er  dept h  of  3.78 m and suppl y co e fi ci ent  of 17.4. T h e l k e ar a ea 

wa s  578.95 km bef or e t he 1950’s  and shr n k t a o 316.2 km due t o exces s r ecl amat i on f   W ang  Sum—  

i n  nd a   Dou  Hong s hen,1 998).   h e W a T n gl i ng Ri ver i s  a sma ll  st r eam wi ni ng i t s way a long t he nort h ba n k of Longga n  Lake 

(Fi g.1).I t   i s   5   km  l o ng,or ig i nat e d  f r o m  l o w  hi l l s   whe e  r bed  r o cks   re a   do mi na t e d  by   g r no— a g nei s s .   h e sma T ll  st r eam l eads  t o Longgan Lake acr o ss  a wet la n d mea s ur ing 400 m i n wi dt h a long t h e l k e  a shor e.  

2 Hum an act i vi t i es   i n t he  Longgan Lake regi on i n recent   50  years ̄ 

h e Longga T n  Lake Far m was est abl i shed i n 1   956.s i nce t hen a number  of  peopl es  have i mmi —   grat ed t o t hi s  r egi on.At  t he end of 1956 t h e popul at i on of t h e Longga n  Lake Far m r eached 2415.  

h e most T  rapi d i ncrease of  popul at i on happened i n 1958.f r om 4256 at   h e end of 1957 t t o 14035 at  

t he   end  o f   1   958.r I 1 he   op p ul a t i o n  o f   he t   Long ga n  a ke L   Far m  r emai ne d  uncha nged   or   s l i ht g ly  dr opped  af t er  1985 when i t  r e ached 28746.  

To  f eed up s uch a rapi dl y i ncr eased popul at i on,l r ge— a sca le of  rec ̄i mi ng a n d i nni ng act i vi t i es  st ar t ed  when t he Longgan Lake Far m wa s  es t abl i shed. Fr om 1 956 t o 1974.t h e t ot l r a ecl ai med area  wa s  60.6 km . Af t er  1974。l n d r a e cl ai mi ng wa s  s t opped because new agri cul t ur l t a echni ques  a n d 

met h ods wer e i nt roduced a n d f er ti li zer s and pest i ci des wer e us ed。a n d t h e popul at i on t ended t o be  st abl e.At  t he begi nni ng of  h e 1980’s。t t he uni t ed f ar m was  di si nt i gr at ed and r e pl aced by a l ot  of  f m i a l y f arms.To get   mor e  cul ti vat ed l and,t h e f ar mers  r ecl ai med  l and a g ai n Af ter  1985.t he f ar m—   .

er s st opped r e cl m at a i on a n d began t o l evel  of t h e l and.pl ant  t r ees a n d di g  t e nches. r   In 1 958,a lmos t  a ll  t h e  lees f  i n t he s ur r oundi ngs  of  t he  l ake  wer e  cut   down a n d  us ed  s  a fuel s  f 0r  



Compi l at i o n  Co mmi t t e e   o f   Long ga n  La ke   Fa r m  Re c0 柑s(e d.),“Lo t m  ̄ ga n  La ke   Fa rm  Re co r d s(1 956—198 5)”  

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No.1  

CHINESE JOURNAL OF GEOCHEM ISTRY 

116" 00E 

39 

11 8。 20E 

30。10. N 

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30’ oo. N 

2 9 ‘ 5 o . N  /  

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/ 二 。 . ∞ EⅢ w EⅢ 瑚 E, 二  .   ‘ 

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▲S a m p l e   s i t e  





Wetl and  ar ea 



/  

Fi g.1.Ske t ch  map  of   t he  ar ea  s t udi ed 

l oca l s t eel  r ef inement .   I n 1976 a phos phorus  f er t i l i zer   f act or y was es t abl i shed on t he l _ onggan Lake Farm.Lar ge— scal e  use of  f er ti l i zer s and pes t i ci des  s t art ed f r om l at er 1970’S.t he annaa l average amount  of f ert i l i zer  used was  4500 t on  fr om 1970 —1985.and t hat  of  pest i ci de 300—500 t on.   I n t he smal l  cat chment  of   t he W angl i ng St r eam .t he backgr ound of  human act i vi t y i S  si mi l ar  t o  t I I at  i n  t he  whol e cat chment  of  t he I . ongga n  L e.  

3 M at eri al s  and  m et hod  Thr ee  shor ts  of  COr eS  wer e t aken  wi t h a  ravi g t y cor e  sa m pl er  long  a t he  Wa n gl i ng  St rea m   i n  Ja n u—  

a r y,200l(Fi g.1).Cor es   we e  r s m pl a e d  at   i nt er va ls  o f   l  c m,s t or e d  i n  pl as t i c  bag s  a nd  f r ee z ed.   Cor e LH 。21  cm  l ong。was  t aken i n  h e  t l k e nea a r  t he  est uar y  of   h e W a t n gli ng  St ream ,a n d i t s  l i h ol t —   ogy i s  domi nat ed by si l t y cl ay. Cor e  L3,22 cm l ong,was  t aken i n t he wetl and,and i s compos e d  mai nl y of  si t y cl ay and cl ayi s h si l t . Cor e L7,19 cm l ong,Wa s  t aken f rom al l uvi l sedi a ment  of t h e  W angl i ng St r eam .and i S composed mai nl y of  cl ayi s h si l t .  

h e t T i me sequence of  t he t hr ee cores  Wa s  det er mi ned by  Cs  n d  ”Pb wi a t h a l ow—backgr ound  ger m ani um  s pect u m  r det ect or  produced  by  EG&G Or tec Co.Sa m pl es  wer e  di gest ed by  mi xed aci d 

(ni t ic r   ac i d,hyd r of luor ic  a ci d  and   pe r ch ] o r i c   a ci d).Af t e r   t he   s ampl e s   we r e   di ges t ed,t hei r   e l e me nt   concent r at i ons wer e det er m i ned by i nduct i vi t y coupl ed pl asma— at omi c emi ssi on s pect rophot omet ry 

f   I CP— AES)wi h  t t he  s t a nda rd  s ol ut i on  SPEX  of   US  as   he t   s t n dar a d.Qua li t y  c ont r ol   Wa s  ss a ur ed  by   te h   na a lys i s   o f   dupl i ca t e  s m pl a es,bl anks,r e f er e nc e  mat er i ls(GSD- a 9 a nd GSD—ll,Chi nes e  g e m—  

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CHI NESE  JOURNAL OF GEOCHEMISTRY 

Vo1 .23 

l o gi c   r e f e r e nc e  ma t e ia r l s)   4 Res ul t s  and di scus si on 

I n core L3。1 3 7Cs was  det ect ed at  17 cm f irst l y and reached i t s f ir st  peak at  14.5 cm co1 Te-   sp o ndi ng t o 1963.Near t he sur face l ayer.at  t he dept h  of  2.5—3.5 cm t h er e  appear s anot h er  pea k  of  Cs  con. esp o ndi ng t o t he Chenor bel y acci dent  t hat  occurr ed i n 1986.Ther e i s st i l l  a smal l  p ea k 

e me r g i ng  bet we en  1963  a nd  1 98 6.Compa red  wi h  t l i t e r a t ur e(Ca r t e r   a nd  Uoghi s s i ,1 977;Wan  Guo-  

j i a ng  et   a 1 .,1 99 0;Xi a ng  Li ang   et   a1 .,1 996),t hi s   s ma l l  pe k  a eme r g ed  i n  1974(Fi g.2).Co r e   L3 i s t oo short  t o get  i nvent or y of   unsuppor ted  ”Pb.hence sedi ment at i on  rat e cannot   be  worked out  

i n t er ms  of  mPb act i vi t y var iati on.Accordi ng t o t i me ma r kers of  Cs.s edi ment at i on rat es  of  core  L3 ar e ca l cul at ed  and  l i s t ed  i n  Tabl e  1.T h e  s edi ment ati on  rat e change  coi nci des  wi t h huma n  act i vi t y 

chang e  i n  t hi s   r eg ion.Si nce   1 956,a   l ar ge   number   o f   pe opl e   i mmi g r a t ed  i n  he  t Long ga n  lake  ca t ch-   ment  a r ea.T h e  popul ati on of  t he Longgan Lake Far m i n 1984 was mor e t h an 10 t i mes  t h at  of  19560 

(Ya n g  Xi a ng do ng   e t   1.,2001).I a t   i s   ne ce s s a r y   t o   r e cl a i m  mor e  and  l t o   f eed  s uc h  a  l a r g e  op ̄l p a-   t i on. Large.sca le r ecl amat i on  l ed t o ser ious  er osi on and hi gh deposi t i on r at e i n t h e s t r eam 。wet l n d  a

n d  a l ke.Si a nc e 1 974.t he g ove r nment  ha s f or bi dde n i mmi ra g t i o n t o  t hi s  r eg ion.Si nce  t he e rl a y  1980’s.t he p o pul at i on. cont ol r  pol i ci es  have been put  i nt o i mpl ement at i on. So,t he popul at ion i n 

h e  t l ake cat chment  ar ea r emai ns  unchanged si nce t h e 1980’s. As  known f r om t h e “l -  ̄nggan Lal 【 e  Farm records”。la rge. sca le re cl amat i on st opped af ter  1985。whi l e wat er conserva n ci es wer e con-  

st r uct ed.1 eadi ng t o  l ow erosi on a n d deposi t i on r at e i n t he st r ea m .wet la n d and l ake a r ea.   Tabl e  1.Sedi ment at ion r at e s  of   c orf ¥L3.L7  and LH 

h e t T hree pea ks  of ”Cs emerged at  t he dept h of  10 5 cm ,6.5 cm and  3.5 cm of  core LH ,   .

cor resp o ndi ng t o 1963,1974 a n d 1986.T h e t hr ee  Cs  pea k  va lues  of  core  L7  emer ged at   h e  t dept h  of  11.3 cm .6.5 cm and 1.5 cm.Sedi ment at i on r at es  of  cor e LH and cor e L7 a r e det er mi ned  by  h e  t

s a me   met ho d a s   i n  he t   det e mi r na t i on  f  o s di e ment a t i on  r a t e  o f   c or e  L 3 (Ta bl e  2).   4.2 Tem poral  and s pat ial  di stri but i on of  el em ent s 

Cor e  L7:T h e concent rat i ons  ofAI  i ncr eas ed rema r ka bl y i n t h e ea rl y 1950’s and kept  a r el a-  

t i ve l y   hi g h  va lue   t i U  1 986.T he  c o nc ent r a t i o ns   of   Mn  we r e   hi 【 g h a t  t he  e ar l y   pe iod  r o f   s edi ment at io n  of  h e core,a t n d  kept  t he s ame l evel  i n t h e ea rl y per iod except  t wo peaks  ar ound 1965 a n d 1980。   h ere i T s  an i ncreasi ng t rend of  P  concent rat i ons,es peci al l y af t er  1   980.T h e concent rat i ons  of  ot h er 



Co mpi l a t i on   Co mmi t t e e   o f   路a I l   La ke  Fa r m  Re co r ds(e d.),“Lo ng ga n  La ke   Fa r m  Re co r d s(19 56—1 985)”  

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Age 

Cr  

Cu 

( AD)   0 

100 200  0 

40 

0 

1O0 200  0 

40  80  0  30000 60000 0  10002000 0 

30  60 0  500010000  0

0 

1 O0  20 0  0 

40 

30  6 0 0  5 00 0100 00  0  100 0 2000 0 

Fe 

M n 

80  0  3000060000 0  10002000 0 

Ni   30 

Ti  

P 

Zn 

60 0  5001 310000  0  10002000 0 

AI  

Fe/ M n 

100  200  0  GO0001000000 

50  1O0 

100 200  0

50  100 

200 0  199 0  198 0  1g 70  -一

196 0  195 0  194 0  193 0 

" 10002000 0 

 ̄6000IW

0 

2 00 0 

’990  198 0  1970  1960  1 9' 5 0  194 0  ’∞ O 

80  20000  ̄0000 60000  0  1000 20 00  0 

100  2 00  0  5Oo00,oo0∞ 0 

50  10 0 

2 ∞ 0 

1990  198 0  —

1g 70 

_一 196 0  ’950  194 0  1g 3O 

Fi g.2.El eme nt   concent r at i o ns  i n  cor es   L7,L3 a nd LH (mg/kg).   el ement s vari ed i n such a t rend t hat  t her e was ,no obvi ous  change bef ore 1980



but  an obvi ous i n- 

creasi ng t rend aft erwards.   Cor e L3:The  el ement  concent rat i ons  a r e gener al l y  hi gher   h an  t h ose of  t COr e L7 T h e out st and.  .

i ng  f eat ur e  i s  t hat  t h er e emerged t wo peak va lues of el ement  concent rat i on a r ound 1957 a n d 1982

, 

es r pect i vel y. Heavy met l s,s a uch a s  Cr,Ni,a n d Cu,s how no cha n ge i n concent rat i ons a long t he 

cor e except  t wo pea k s. Fe,Mn,and P t end t o i ncr e as e a ft er  h e pea t k  of  1982 r n1 e  concent rat i ons  0f  Al  have not abl y i ncr ea s ed si nce t he 1950’S.   .

Cor e LH :   concent rat i ons  of  A1   have  l so  a i ncr eased  si nce  t he 1950’S Heav y  met als  such a s  Cr  and Cu were at  t hei r pea k  va lues  a r ound 1971  a n d 1993. Fe a n d Mn have t he sal ne i ncr easi ng  .

rend si t nce t h e 1950’S,es peci ll a y Mn i n r ecent  years. A r e ma rkabl e i ncr ease i n P st ar t ed f r om  1968.  

Va r i a t i ons   i n   el e me nt   co nce nt ra t i o ns   f r om  luvi f l  a s edi ment s(L7)t o   we t l a nd s e di ment s(L3),   n d  a ina f ll y  t o  l ke a   s edi ment s(LH)r e lec f t   he  t rans t por t   pr oce s s   o f   ma t er ia l s   f r om  t he  8 0ar ce  t o  t he   l k e.As a  vi ewed f r om el ement  concent rati on vari at i ons mat er ia ls a re l ed t o t he r i ver  f ir st.a n d t hen  t o t h e wet la n d except  a smal l  par t  of  t hem deposi t ed as  f luvi l s a edi ment s Af t er compl i cat e physi ca l  ,



n d chemi a ca l vari at i ons  i n wet l and h t ey a r e fur t her t ransp or t ed a n d deposi t ed i n t l l e hl 【 e f inal l y.   r nl e l ag t i me of  some el ement   concent rat i on pea ks  i n t he l k e  a sedi ment s  ef r lect s t he t r n spor a t pr oce8s  ,

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fl r 0m wet l and t o l ake and demons t rat es  t he wet l and buf f er f unct i on t o t he mat er ial s  f rom t he l ake  cat chm ent.  

I r on i s  a ki nd of   mi cr onut r i ent s.I t  may have an i mpact  on  h e di t rect   bi ol ogi cal  

and P,a n d hence i nf luence t he phot os ynt hesi s  of  pl nt a s.I ncreases  i n i ron cont ent  i n sea  wat er   have 

enha nced   t he  pho t os y nt hes i s   ef ici e ncy  a nd i mpr ov ed  pr ima r y  pr oduc t i vi t y(Hut c hi ns   n d Br a ul n d, a   1 998;Pe t i t  e t  a 1.,1 999;Eng s t or m  a nd  Wr ight,1 98 4).The r ef o r e,hi s t o ic  r v ar ia t i o ns   i n  P  n d  a Fe   cont ent s  i n  l ake s edi ment s  r ef lect   h e  t change of  l ake t rophi c  st at us.T h e  concent rat i on vari at i on  of   Fe  n d P i a n cor e LH revea ls  t hat  t he t r ophi c l evel  of  Longga n  Lake has been r isi ng cont i nuousl y si nce  1950.especi al l y si nce t h e 1 980’s.   I n sur f ace sedi ment s  of  core LH .t he concent rat i ons  of  Mn are obvi ousl y hi gher  t ha n  i n t h e l ow—   er  l ayer.T h e enri chment  ext ent  of  Mn i s hi gher  t ha n  t hat  of  ot her  el ement s l at er  si nce  h e 1980’s. t  

Mn enr ichment  i n s ur f ace l k e sedi a ment s i s  a gl obal  phenomenon a n d i s a lways  at t ibut r ed t o oxi da-  

t i o n— r e duct i on(Engs t o r m  nd  a wr i h t,1 g 98 4;Pa ul   a nd  Ro be r t,2000;Boyl e  e t   a 1 .,1 999).Unde r   n oxi a c condi t i ons.ma n ga n ese  may be mobi l i zed  i n s edi ment s  a n d t r n spor a ted  f urt her  t o  mole pr of un.  

da l  r e gi o ns(Mor ti me r,1 941,1 942).I n c or e  L3,t he  c once nt r a t i o ns  o f   Fe  a nd Mn dr oppe d but   t hos e   o f   Cr   nd  a Cu  i ncr ea s ed   a f t er   t he   1 98 0’s.i mpl yi ng  hat t   hi hl g y   r edo xi c   co ndi t i ons   a r e   de ve l o ped  i n wedand.On t he ot her   hand.Fe  n d Mn wer a e enr iched i n core LH a ft er   l at er  i n t he 1980’s.The  Fe/Mn r ati o  of  cor e LH show a si gni icant f  decr ease si nce t he 1980’s.revea li ng t hat  manga n ese i s   s el ect i vel y enri ched because i t   woul d di ssol ve at  hi gher r edox pot ent i l a a n d t end t o r emai n i n s ol u—  

t i o ns  l ong er   ha t n  Fe(J o ne s   and   Bowe r s,1 978).Ano t he r   r e as o n  f or   he t   s i g ni ica f nt   i ncr ea se   o f   Mn  i n  s uf ac e  s e di ment s   ma y  be   human  a ct i v i t y (t o   be  di s c us s ed   i n  t he   f ol l owi ng   s ec t i o n.)   4.3 Hum an acti vi ies and el t ement  concentrat i ons 

Huma n  ac t i vi t i es   i n  t he   Lo ngg n  a Lake  r e io g n  hav e  a   g r ea t  i mpa ct   on  t he   va r i a t i on  t r end  o f   e l e—   ment  concent rat i ons i n l k e sedi a ment s. Al umi num i s  t hought  t o be mai nl y rel at ed t o cl ay mi ner ls a  

f r om  ad j a ce nt   wea t her e d be d r oc ks .Hi he g r   enr ichment  o f   A1  i n  l ke a  s e di me nt   i ndi ca t es  t ha t  mor e   ine・ f rai g ne d  c l a y  ma t e ia r ls   c ome   f r om  he t   be d  ocks(Sz r ef e r,1 990;Sz e f er   e t   1.,1 a 995).Thi s   f e a—   t ur e i s  of t en  used t o i ndi cat e t h e i nt ensi t y of  weat h er ing i n t he l ake cat chment  a n d cl i mat e cha n ge  In  t he Longgan L a ke r egi on.t he enri chm ent   of   Al   f ur ther  ref lects   t he  cha n ge of  hum a n  act i vi t y i nt en—  

si t y.Si nce t he 1950’s,t he popul at i on has  been enl r ged drast a i ca ll y,excessi ve recl amat i on of  l n d  a l et s mor e mat eri ls a  t o be t r n spor a ted i nt o t h e l k e f a rom t he cat chment . Si nce t h e 1950’s.el ement   concent rat i ons have changed s ynchr onousl y i n cores  L7.L3 and LH .es peci ll a y t he Al  concent ra.  

t i ons t h at  i ncr ea s ed  rapi dl y i n t he mi d 1950’s  and remai ned cons t ant  or  sl i ghdy decr ea s ed s i nce t h e  1980’s  due t o t h e s t op of   l n d recl a amat i on.On t he cont r ar y.t he concent rat i ons  of  P have i ncreas ed  si nce  t he 1980’s because of   sl at h er i ng  fer ti l i z er s and or ga ni c phos phorus  pest i ci des.   Two  event s  of   cl earance of  rees t  on a l ar ge sca le  i n 1958 a n d at  t he  begi nni ng of   t he 1980’s  l ed  t o a  si ni g ica f nt  i ncrease i n el em ent  concent rat i ons  i n cores  L3 and LH .but  t he t i me at  whi ch 

va l ues  appeared i n core LH wa  put  of  i n core L3 ( t o   be   di s c us s ed  i n  t he   f ol l owi ng  s e c t i on).   I nt ensi 6cat i on of  human act i vi t i es i S  r ef lect ed not  onl y by t he var i ati on of  el ement  concent ra—   t i ons,but  a ls o by t h e var iati on of  sedi ment at i on r at es.  Sedi ment at i on rates  of  cor es  L7.L3 a n d LH 

a r e   r el a t i v el y  hi h  g f r om  t he  1 950’s   t o  t he  1 980’s .   I n Longga n  L a ke,  manga n ese concent rat i ons  have i ncrea s ed si gni ica f nt l y i n recent  20 year s.  

Besi des  t h e chemi cal  pr oper ti es  of  manga n ese ment i oned above,a n ot her expl n at a i on of  h e si t s,  ̄ 一   cant  i ncr ease of ma n ganese concent rat i ons  i s  huma n  act i vi t y.  Gl eyi icat f i on and aci di icat f i on of s oi l   caused by huma n  act i vi t i es  enhanced l eachi ng of  Mn f rom soi l,f ol l owi ng by t h e i mpact  of  Mn i nt o  h e l t k e.Owi a ng  t o economi c devel opment,SO2  emi ssi on due t o combust i on of  coal,i ncr eases  year  ,

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bv   ve ar(Fu  Li xi n  e t   a 1 .,1 997).I n 1 990  t he  me an  SO2  e mi s s i o n f o r   Anhui   Pr ovi nce  a nd HCRa B  Pr o vi nce i s  est i mat ed  up t o 6.7 ×10 kg/km :3. 4 ×10 kg/km f 0r t he nei ghbor ing Hubei  Prov-  

i nc e:and   50.3×1 0 k s/km f or   Ji a ngs u Pr ovi nc e(Ra m  e t   a1 .,1 996).SO2   and  NO2  a r e   he  t t o p  t wo  a t mos phe ic r   pol l ut ant s   re  a r es pons i bl e   or f   t he  oc cur r e nce  o f   a ci d r ai n(Ma s on,1992).Soi l   i s   al ways  sens i t i ve  t o aci d r ai n,t hough  t he  soi l   sensi t i vi t y  has  not  been meas ur ed.Deposi ti on  of  mor e S 

wi l l   a cc el e r a t e   he t   pr oc es s   o f   ca t i on   exc hange   i n  s oi l,a nd  enhanc e  l e ac hi n g  o f   Mn  f r o m  s oi l(Kah—   kone n  and  Mahone n,1 993;Li l i eho l m  and  Fr e a gl e y,1 988).I n   t he   ca t chme nt   of   Lo ng ga n  Lake  he t   ma j or   c ops r   re a   ic r e   and  l o t us.Per ma nent   s t o r a ge   o f   wa t e r   ca us es   t he   g l ey i ic f at i on  of   s o i l,t hen  l e ad—   i ng  t o  t he   e nha n cemen t   o f   l ea c hi n g  o f   Mn (Xi a ng  Wa nhong  et   1.,200O). a   4.4 Bufer  f uncti on of  wet l and  to materi al s from   the l ake catchment  

Mat er ia ls t r ans por ted by r iver s,s uch as  heavy met al s,polut ant s,nut ient r s and par ti cl es,ar e  deposi t ed part l y i n t he wet land owi ng t o t h e decr eas e of  wat er  dynami cs,pl nt a  abs or pti on a n d geo—   chemi ca l react i ons. Hence,wet l n d acts a  a s  a bufer  t o t he mat er ia ls  fr om t he l ake cat chment  t o  h e  t

l a ke(Ga y da r dj i ev   e t  a l  1 996;Roo d e t  a 1.,1 995;Ande so r n e t  a 1.,2000).Geoc he mi c l r a e —   s earch on t h e wet l and shows  t hat  t he mai n pr o cess  of  bufer ing t o t h e met al s and nut ient r  el ement s 

f r o m  he  t l a ke   ca t chment   i s   el e me nt   de pos i t i on  wi t h r edo xi c   r ea c t i on (Ga ydar dj i e v e t   1.,1 a 996).   Hi gh wat er cont ent  and  l ow  oxygen cont ent   make  t he wet l n d  a be i n a  reduct i ve condi t i on.I n t hi s  si t .  

ua t i o n,Eh  i s   nor ma l l y  l o w,t hus   f av o ing r   he t   e xi s t e nce   o f   S  (Ta n ,1 998;St e wa r t   a nd  Fe r gus on, s   1 994).Me t al   el e me nt s   ar e,t he r e f or e.ea sy  t o   c ombi ne   wi h  t S   t o   or f m  met l  a s ul phi des .The   met al  

s ul phi des  a e r r e l at i v el y  i ns ol ubl e,r educ i ng  t he  pot e nt i l f a or   emobi r l i z at i on (Bi r c h e t  a 1.,1 996).   Cr,Cu  and  Ni   lwa a ys   c l i ng   t o  Fe“ a nd  Mn  o xi des(St e wa r t   a nd  Fe r gus s on,1 994).Under   r e duc —   ive condi f t i on.Fe and Mn a r e reduced t o Fe“ and Mn  ,a n d  t he met al s  cli ngi ng t o Fe a n d Mn ox.   i des  r e relea a s ed t o f or m  s ul phi des.   St umm et  a 1 . demonst r at ed t hat  t h e sur f ace of  or ga ni c debr is  cont ai ns a number  of  f unct i ona l 

gr oups   s uch   s— a OH  n d・ a COOH,whi ch  have   a   hi g h  a fi ni t y  or f   me t ls(St a umm  e t   a 1 .,1 994).We t -   l n d sedi a ment s cont ai n a l ar ge a m ount  of  aquat i c pl ant  debr is,whi ch can pr o mot e met al  dep o si t i on 

i n t h e wet l n d. a   Mat eri ls i a n wet l and  wi l l   be t r n spor a ted t o  t he l ake f inal l y and dep o si t ed  t her e.Cr,Cu.Zn a n d  Ti  a r e di fi cul t  t o r emove  af t er  r edoxi c r eact i on i n t he  wet l and.a n d s houl d be car ri ed  by s uspensat es  n d t a ra n spor ted i nt o  h e l t ake.As  st at i st i cs  dat a  show.more t han  98% 0f   Ti  and  Cr   n d  a 70% 一80% 

of   Cu   and  Zn  re  a no t   t r ns a po ted  r i n  s ol ut i ons,but   re a  a ds or bed  on   t he   s us pens a t es(Zha ng  Hucai .  

1997).Mn  and  Fe   a r e   lwa a ys   t r ans po te r d  i n  wa t er   i n  t he   or f m  of   c ol l o i ds   or   i n  s ol ut i ons(   Zhang   Hu—   ca i,1 997).Di fe ent r   ra t ns por t  or f ms   o f   el e me nt s   ls a o  re a   bene it f i l  a t o   t he   wet l n d  a t o   bu fe r   s ome   e 1 .   ement s  fr om t h e l ake cat chment.   I n t he Longgan Lake cat chment,t he  wet la n d  exhi bi t ed t hi s  bu f er  f unct i on as  asychr onv i n el e.  

ment  concent r at i on vari at i on bet ween wet l n d a a n d l ake sedi ment s. Pea k  concent r at i ons of  Cr.Cu.   Zn,Ti  a n d ot h er  heavy  met al s i n cor e L3 emerged  ar o und 1957 a n d 1982.r espect i vel y,corr esp o nd.   i ng t o t hose i n core LH ar ound 1971  and 1993.It  i s a t i me gap of  about  11—14 year s.T h e bu f er   f unct i on t o  Fe and Mn i s  not  s o  r ema rka bl e due t o  h ei t r  chemi ca l act i vi t y.T h e peak  concent rat i ons  of 

Fe  n d Mn i a n t h e wet l n d art a r ri but ed t o huma n  act i vi t i es di d not  appea r  i n l ake sedi ment s I n wet .   . 

1 n d sedi a ment s,P concent rat i ons  t end t o i ncr ea s e dr st a i ca ll y s i nce t h e 1950’s whi l e i n l ake sedi .   ment s  hi t s t r end emerged i n ea rl y 1960.   .

Int ens i ve human act i vi t i es  si nce t h e 1950’s,due t o t he i ncrea s e of  popul at i on i n t hi s  regi on . 

have weakened a n d des t royed t h e bu f er  f unct i on of  wet l and.  A compar i son of  t he peak concent r a.  

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t i ons  of  el ement s i n l ake sedi ment s wi t h t hose of   wet land sedi ment s shows  t hat  t he l ag  t i me becomes  s hor t er  a n d shor ter  wi t h gradual  r ecl amat i on of   wet l and.  

Tempor l a a n d spat i l di a st ri but i on of  el ement s  i n t h e  t hr ee s hor ts of  cor es  t aken f r om f iver.wet -   l n d a a n d l ake a l ong t h e W angl i ng St ream ,Longgan Lake, cl earl y r eveal s t he pr ocess  of  el ement  

t r n sp a or t a n d dep o si t i on i n t he l ake cat chment.efect i vel y r ef lect s t he bufer  f uncti on of  wet l and t o  h e mat t er i ls  a f rom l n d t a o  l ake.mea n whi l e i t  has r ecorded r ea li st i cal l y  huma n  act i vi ies.Huma t n  ac—   t i vi t y i s an i mp or t ant  f act or l eadi ng t o t he vari at i ons of  sedi ment at i on r at es a n d el ement  concent r a-  

t i ons i n s edi ment s. Mat eri l s  a sour ced f rom t he l ake cat chment  a r e part l y deposi t ed i n t h e f iver.a n d  h en t t r n spor a ted t o t he wet la n d.W i h  compl t i cat ed chemi ca l react i ons.part  of  t he el ement s ar e r e—   t ai ned i n t he wet la n d t hat  di spl ays t h e bu f er  f unct i on of wet l and. Theor et i cal ly. t h e mat er ia ls  s our ced f rom t h e cat chment   wi l l   be  brought   i nt o t he  l ake a n d dep o si t ed t h ere  ina f ll y.T h e l g  a of   vari —   af ion i n concent r at i ons  of  s ome el ement s  i n l k e s a edi ment s  ef f ect i vel y demonst r at es t h e bu f er  f unc—  

t i on.meanwhi l e i t  r emi nds us  t hat   we shoul d pay  more at t ent i on t o i t  when  we us e l ake sedi ment s t o  i nt er pret  envi r onmenta l change a n d huma n  act i vi t y. T h e envi r onment l pr a oxy change of  l ake sedi —   ment s may not  b e  a lways s ynchr onous,some proxi es may pos t dat e t h e act ua l envi r onment  cha n ge or   huma n  act i vi t y event,na m el y l i nea r  a n d nonl i nea r r espons e pr ocesses.  

Ander son W . Rat e,Al i st ai r E.Rober t son,and Audrey T. Bor g,2000,Dis t ri but i on of  heavy met al s i n nea/ " 一shor e sedi ment s of t l I e 

Swa n  Ri ve r   es t ua r y,wes t e r n  Aus t r a l i a[J]:Wat e r,Ai r,a nd  Soi l   PoHut ion,v.1 24,P. 15 5—1 68.   Bi rch,L.,K.W .Ha n seh n ann,a n d R.Ba c hof en,1996,Heav y  met al  cons er vat i on i n Lake Cadagno  sedi ments:his ̄f icM r ecor ds of 

nt a op r og en i c   e mi s s i o n  i n  a   me r o mi c t i c   Al pi ne   ake[ L J]:Wa t er   Res ea r c h,v. 30,P. 687—69 7.   Boyl e,J.F.,N.L. Rose,H.Benni on  et   a1 .。1999,Envi r onment al  i mpl i cat ion i n  t he Ji angha n  Pl ai n:evi dence f r om l ake sedi ment s 

[J]:Wat e r,Ai r,a nd  oi S l   Pol l ut i o n,v.11 2。P. 21—40.   Br e e n,P. F.,1 990,A  mas s   b al nce a   me ho t d  f o ra ss es s i ngt he   p ot en ia t l   ofa rt i ic f i al   we t l ndsf a orwa st e   wa t e rt r ea t me nt[J]:Wa t erBe -   sear ch,v.2 4 ,n.6,P.689—697.  

Br i x,H.,1 9 94,Func io t ns   o fmac ophy r t es   i n   co ns t r u ct e d  we t l nds[J]:Wa a t e r   Sci e nc e   Te ch nol o gy,v. 29,n. 4,P.71—78.   Ca r t er   Me l vi n,W.a nd  Mo ghi s s i   A.Al n ,1 a 977,Th r ee   de c ade s   o fnuc l e ar   t e st ing[J]:He al h  t Phy s i cs,v. 33,P.5 5—71.   En ̄t om ,D.R. a n d H.E. Wri ght,1 984,Chemi cal  st rat igr aphy of  lake sedi ment s a s  a record of  envi o nment r al  ch∞ ge, i n E.Y.  

Ha wo r t h  nd a  J.W.G.hl nd,a ds.,Lak e  s edi men t s  a nd e nvi r on me nt al  hi s t o r y [C]:Mi nne a ol p i s,Uni v er s i t y  o f   Mi nne s o t a  Press。P.11—68.  

Fu   Li x i n,Hao   J i mi ng,Zho u  Xuel o ng   e t   a1 .,1 997,Tr end s   o fe ne r g y   c ons umpt io n  nd a   SO2   em is s i on   i n  e st a e n  r Chi na[J]:Chi naEn—   v i r o nme nt   Sc i e nc e,v.1 7,n. 4,P. 349-352 (i n  Chi n es e   wi t l I   Eng l i s h  a bs t r a ct ).   Gay da r d j i e v,S.,M.Had j i hr i s t o va,a nd   R.Ti c hy,1 996,Opp or t u ni t i e s   or f   us i n g  t wo  l o w— co s t   me ho t ds   or f   t r e at ment   of   me t al   beB r i I l g  a que ous   s t _ r e A i l n¥[ J]:Mi ne r a l s   Eng i nee r i ng,v .9。n. 9,P. 947—964.  

Hu t c ins,D. h A.a nd  K. W.Br nl n d,1 a 998,I r o n— l i it m e d  gr o wt h  nd a   Si /N  u pt ake   r a t i o  i n  a   c o a st alupwe li ng   r e g i me[ J]:Na t ur e,v.   393,P.561—56 4.  

Jone s ,B.F.a n d C.J.Bower s,1978,Them i ner alogy  andr el at ed chem i st r y  ofl ake sedi ment,i nA.Lerman,ed.,L a ke s chemi st r y。  

g e ol o gy,phy s i cs[M]:New Yor k,Spr in ge r,P.1 79—235.   Se ns i t i v i y  t o f   s oi la nd   wa t e st r o   a ci di ic f at i o n,Fi nni s h  La pl nd[ a J]:App ie l dGeo che is m .  

Kahkonen,A.M. a n dO.Ma b onen,1993



t r y,(Sup.),n. 2,P. 49—50.  

Li ieho l l m,B. C.a nd  S.C.Fr e a gl ey,1 988,Efe c s  t o f   s t i mul at e d  on   oi s l  nd a   l ea cha t e   ci a di ica f ion  t ofLe xi ng t on   s i l y  t oi s l   l o am [J]:   oi S l Sci ence,v.146,P.317—326.  

Ma so n,B.J .,1 9 92,Ac i d  r in:I a s  t c au es s   nd a   efe ct s   on  i nl nd  a wat e s [M]:Ne r w  Yo r k,Oxf o d  r Un i v er s i t y  Pr es s。P.1 26.   Mo r t i mer ,C.H.,1 941,The   e xc hang e   o f   di s ol s v ed   s ubs t nce a s   be t we e n  mu d  nd  a wa t er   i n  l a ke s [J]:J our na l   of   Eco l og y ,v .2 9,P.   208—329.  

Mo r t i mer,C.H.,1 942,T he  e x ch ang e  ofdi s s ol ve d  s u bs t an ce s   be t we en   mud   nd a   wa t r  e i n  l a kes[J]:J our na l  o fEco l o g y,v .3 0,P.   147 一O1.  

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Paul  J.  Garri s on and  R0ber t  S.Wakema n ,2000,Use of  pal ol e i mnol ogy t o document  t he efect  of  l ake shorel and devel opment  on wa-  

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