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Lead lability in alluvial soils of the river Trent catchment, U.K.M. Izquierdo, A.M. Tye, S.R. Chenery
British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK
Lead lability in alluvial soils of the river Trent catchment, U.K.M. Izquierdo, A.M. Tye, S.R. Chenery
British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK
SOURCE APPORTIONMENT
27 sampling sites
paired topsoils (0-15cm)
and subsoils (35-50cm)
+ extraction of pore waters
Pb= 40-1280 mg/kg
Extensive Pb mining since pre-Roman times
Pb-rich sediments still pulse into the Trent tributaries
Floodplains downstream the Orefield are a primary Pb repository
ACKNOLEDGEMENTS
Pb IN TRENT ALLUVIAL SOILS
Overbank sediments in the river Trent
floodplains act as a focus for deposition
and short- to long-term storage of Pb
Pb can be released back into the drainage
network through bank erosion
Potential for increased Pb uptake to grazing
livestock, terrestrial and aquatic
ecosystems
AIMS & METHODOLOGY
Pb SOURCES IN THE TRENT CATCMENT
2. Coal
Coal mining
Coal combustion emissions
3. ‘BHT’ Pb
Diffuse source
Petrol-derived
1. Pennine Ore
Examine the sources, lability and
solubility of Pb in alluvial soils from
the River Trent and River Dove
Pb source apportionment
Pb Isotope dilution
2.350
2.370
2.390
2.410
2.430
2.450
2.470
2.490
1.070 1.090 1.110 1.130 1.150 1.170 1.190
208 P
b/20
7 Pb
206Pb/207Pb
coal
Pennine ore (galena)UK petrol lead
pore water surfacetopsoil
pore water subsoilsubsoilLondon aerosols
labile poolroad dustsewage
BHT (petrol) Pb
UK coalPennine Pb ore
Km d
owst
ream 0
50
100
150
200
2500 20 40 60 80 100
Lability %E
2 3 4 5 6 7pH
8
pH% E
206Pb/207Pb1.100 1.200
Pennine ore Pb dominant BUTBHT (petrol) Pb contribution=0-
50% despite withdrawal in 2000
BHT Pb in subsoilspost depositional vertical
migration of Pb from traffic related sources
Pb LABILITY-10
0
10
20
30
40
50
-10 10 30 50
% petrol Pb
topsoil
su
bsoil
Current UK regulations on metal contamination are based on the total
concentration in soil no indication of the chemically reactive or labile
fraction of a given element in a soil system
ISOTOPE DILUTION TECHNIQUES (E-value) allow the determination of
the reactive pool of metal in soils i.e. pool of metal in equilibrium with soil
pore water
L labile: soluble+adsorbed+solubilised in pore waterN fixed Pb: occluded, inert, inaccessible
NN
LN
L
N
LL
LL L
NN
LN
L
N
LL
LL L
spike 204Pb
E-VALUE Isotopically exchangeable fraction:
geochemically active – bioavailable for uptake
LABILE Pb=9-56% over the total pool
No differences in Pb lability with depth
No Pb >fixation with depth
evidence of continuous
bank recycling
No differences in Pb
contents with depth
No source control on lability
Strong pH control on %E
1.120
1.130
1.140
1.150
1.160
1.170
1.180
1.190
1.120 1.130 1.140 1.150 1.160 1.170 1.180 1.190
LABILE POOLNONLABILEPORE WATER
This work has been funded by a Marie Curie Fellowship (Project no. 254983) to M.Izquierdo
206Pb/207Pb
208 P
b/20
7 Pb
Pb isotopic ratios in total, labile and pore water pools
Enrichment of ‘BHT’ Pb in the bioavailable poolspossible causes
BHT Pb still being deposited (dry/wet deposition + present/recent dissolution of poorly soluble traffic related Pb-bearing species
BHT Pb bound to sub-micron FeO colloids in soil pore waters
M.Izquierdo, A.M.Tye, S.R.Chenery Sci Total Environ 433 (2012) 110-122