Actividades

absent and thi s may be one of t h0 reasons for tha

di:::'feronces

between the reported _{effects and} those ob_served in the pro sGnt �tudy.

4.

The influenc e s of nickel a nd

trations in the soil on

the

ratios of the metal

concentrations in the leave s .

(

a

)

I ntroduction .

It i s known that the abs vlute c oncentration of a metal in a plant can vary sli

gh

tly due to the age , posit ion on the tree , et c . of the leave s sanpled. H owever , the rat io of the c oncentrat ion� of two !Lletal s i n the leave s of a parti cular spe cie s should be apprcxiriatcly constant in Rll leaf sample � , if the accumulations of both L'lota l s _<".ro regulated by the plant . \Vhere so!Lle exte rnal inf lue nce

is

pr2 sent

the

r�tio could deviate from normal .

Such a c oncept has b ee n u sed in the past for biogeo chouic al prospecting. Warren and Delavault

( 1 948)

suggested the use of the

ratio of copper to z inc concentrat ions in plant tis sue s as a ncans

of

d

etecting anomalous concent rations of the se two metals in the

soil. The se authors reported value s of this ratio for a number of

trees in British C olumbia growing over both non-mineralised and

mine ralised rocks . They c onsidered that any rati o of copp

e

r to

zinc i n the second year twigs greater than

0 . 20

to 0, 25 , de:"cnding

on the spedi�s , could possibly be indicative of copper mineral­

c oncentrations of copper and z inc v.:1ried conside rCLbly b 8twc en sanple s of the same species , the copper t o zinc ratio wa s Duch more c 0nstant . S ince that time , the se workers have conpiled a v ery c omprehensive

li st of the mean copper a nd zinc concentrations, a s well a s the copper

to zinc ratios , for a large number of different specie s growing over

both mineralised and non-ninerali sed roc ks .

(

Warren ,

1 962 ;

Wr:.rren

and D e lavault ,

1 949 ; 1 955;

Warren et al. ,

1 949 ; 1 951 ; 1 95 2 ; '1 9 66)

White

( 1 950 )

inve stigated some British C olw.;bia copper

depo sit s. He found that although the copper and zinc c once ntrations in the plant s growing in the vicinity of the ore varied considerably , the ratio of c oppe r to zinc , whe n gre'1ter than 0 . 30 , v:a s s uc c e s sful in finding the ore body.

Worthingt on

( 1 955)

used this r(: t i G in the vici11i-t..;: c .�. a

lGad/

zinc deposit and found th2..t c 01JPCr t o z inc r<-otios in th-J plP.nt tissues,

l e s s than 0 . 05 , succes sfully dcli ne:::.tcd the or.:: body.

Nioolls

�

( 1 9 65 )

a l s o considered the c oppe r to zinc ratio in the ir study of b otanical and geochemical prospec ting methods i n the Dugald River area , Au stralia . T he se authors appare ntly did not consider the ratio useful in their particular area.

In

the

present study all poss ib le rat ios between the netals an

aly

s ed

in the

plant s were correlated against the copper and n ickel c oncentrations in the

-1 20

Lle sh fraction of the soil .

The

correlation

c

o

e

ff i

cien

t

s Hhich

were

s

igni

f

i

c

a

n

t

are shown i n Table IV - 1 6. The

plant x

soil

correlation coefficients for

nickel and copper are

also shown for

comp

ar

i

s o

n.

N o ratio of

netal co

n

ce

n

t

rat

i

o

na

in t

he l eaf ash gave

a better corre lation

to the nickel content of the soil than Qid

the nickel

concentration in

the leaf a sh .

S i nce the corrcl:-�tion

coefficient between the copper

concentrat ion in the leaf ash 2-.nd the concentration of

th

is

.metal in

the soil

was

0 . 29 6 ,

any

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