[PPT] - ON HEAVY METALS? Robert van de Graaff, PhD van de Graaff & PowerPoint Presentation

SLIDE 1

ARE WE SOMETIMES TOO HEAVY ON HEAVY METALS?

Robert van de Graaff, PhD van de Graaff & Associates Pty Ltd

SLIDE 2

Background to this talk

All examples are taken from my practice as

a consulting soil scientist

In all cases the Environmental Assessors

were concerned about real contamination and health risks due to official EPA- ANZECC-NHMRC-NEPM concentration thresholds being exceeded

There was hardly ever any real risk

SLIDE 3

Field Examples

1. Barium panic stopping residential development near

Melbourne

2. Heavy metal accumulation in the 120 year old Sewage

Farm, at Werribee near Melbourne

3. Arsenic panic at future Melbourne Museum site
4. Miscellaneous: chromium perceived problems
5. Lead contamination at Ardeer battery recycling plant
6. Lead contamination at Sandringham battery recycling

plant

SLIDE 4

First let us have a look at vertical differentiation of soil profiles

Profile developed on sand over long time in moist climate. A “spodosol” where humus and the iron has moved and settled out deeper down Duplex profile in which the topsoil has lost clay and iron, but iron nodules may have accumulated at the boundary

SLIDE 5

More common soil profiles

Iron concretions “buckshot” at the boundary between seasonally waterlogged loamy topsoil and clay

subsoil. A “contemporary” soil

profile in outer Eastern Melbourne Kinglake Plateau: Iron has been retained in a “fossil” soil, coating all the soil particles. Soil formed in wet tropical climate

SLIDE 6

Melbourne’s drinking water under severe threat!!!! The Sugarloaf Reservoir from the air

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On the beaches we find that wave action has washed out ferruginous gravels “buckshot” that belong to these soils

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Chemical composition of the gravels

Total (1st rows) & TCLP Leachable (Last rows)

mg/kg (except Fe in %) and mg/L

As Cd Cr Co Cu

Fe

Pb Mn M

Ni

Se Sn Zn 160 <0.5 150 8.5 18

19 %

42 78 <1 34 <2 <10 38 As Cd Cr Co Cu

Fe

Pb Mn M

Ni

Se Sn Zn

< 0.02 < 0.05 < 0.05 < 0.05 < 0.05

0.38

< 0.05 0.13 < 0.5 < 0.05 < 0.02 < 0.5 0.63

SLIDE 9

The beach gravel by Victorian EPA standards is a contaminated soil

But,

Melbourne drinking water has negligible As, Cr and Mn. EPA soil classification standards are not able to provide realistic safety guidelines as they do not consider geochemical behaviour

SLIDE 10

Ironstone and bauxite, the last surviving dregs of chemical weathering

Heavy metals locked up in laterite cap rock are environmentally inert; e.g. nickel laterite Bauxite cap rock on left is a mixture

f Al(OH)3 with ferruginous and

clay impurities; Laterite or ferricrete cap rock on right

SLIDE 11

Soil profiles on clay parent materials

A “cracking clay” formed from basalt in a relatively dry climate . Lime has accumulated at the base A “red-brown earth” missing its topsoil, belongs in relatively dry

climate. Whitish layer has lime

SLIDE 12

Soil Eh and pH effects on metal speciation

Normal range of soil pH and redox potential, Eh Speciation of iron

SLIDE 13

Iron oxides and hydroxides have different colours depending on mineralogy, e.g.:

Goethite: α-FeO(OH) Hematite: α-Fe2O3 Magnetite: FeFe2O4 Ferrihydrite: Fe10O15.9H2O Maghemite: γ-Fe2O3 Lepidocrocite: γ-FeO(OH) Courtesy Rob Fitzpatrick (CSIRO)

SLIDE 14

Gley colours and mottles in subsoils of very poorly drained soils

Soil profile in a drained peat swamp, with grey “reduced” colour Detail of soil mottling and gleying: goethite is mustard yellow, hematite brick red

SLIDE 15

Munsell Color Charts – a means to standardise colour descriptions Soil colour – a means to estimate oxidation / reduction status of the soil

The more red the soil, the better is its oxidation status, i.e. its natural drainage Complete lack of soil colour mottles, i.e. a uniformity of brown and reddish colours, the better its drainage status

SLIDE 16

Soil changes in relation to natural drainage regime in the landscape

►Differences in soil morphology are recognised as distinct soils ►Soil maps are made based

n these distinct profiles

Bath – the best drained soil profile is well oxidised throughout, whole coloured in Bir Mardin – has mottles more in Bg (B gley) due to reduction Volusia – has bleached A2 due to seasonal waterlogging Chippewa – G horizons are grey and bluish, few mottles

SLIDE 17

Effects of climate – water balance between rainfall and evaporation

This transect covers soils developed on wind-blown glacial dust since the end of the last Ice Age (≈ 20,000 yrs) From west to east rainfall increases and evaporation decreases Percolating rain water dissolves calcium carbonate and moves it down the profile When plants take up water, the soil solution becomes saturated and calcium carbonate precipitates out. Gypsum is more soluble and precipitates further down

SLIDE 18

Slightly elevated Barium concentrations hold up residential development in Deer Park, Vic., and cost heaps

The soil: heavy clay soil profile developed from basalt in

relatively dry climate; all these soils have illuvial CaCO3 horizons and increasing pH with depth

The problem: “high” Ba stops the Environmental Auditor

from saying the site is safe for residential use.

The economics: Developer has to pay interest on

borrowed money of $A 40,000 per month, he says

SLIDE 19

What did we do?

We assumed Ba would be as SO4 or CO3
We assumed BaSO4 or BaCO3 would

behave just like CaCO3 in illuvial processes

Sample two pits in intervals of 10 cm as far

down as bedrock

Determine depth functions of pH, EC,

exchangeable Na, water soluble SO4 and Total and Leachable Ba

SLIDE 20

What did we notice and consider in the Environmental Assessor’s report?

All elevated Ba always in samples taken at 0.5 and

1.0 m depth, never at 0-0.1 m (these are prescribed sampling depths and followed by Assessors as per cookery book!)

Past land use only grazing for sheep or cattle
Therefore living plants and animals are part of the

geochemistry

Therefore there must be proteins, thus sulphur,

and thus SO4 in the system

SLIDE 21

Seven offending sampling sites having “high” barium in the soil

SLIDE 22

Sampling two pits at Deer Park every 10 cm shows barium bulges at about same depth as lime

10 20 30 40 50 60 70 80 90 100 20 40 60 80 100 120 140 160 180 200 Depth (cm)

Barium in HCl

Site #76 Site #104

SLIDE 23

The soil as a chromatogram

Cracking clay on basalt at Deer Park, Vic.

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90
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6 7 8 9 10 depth (cm) pH Site #76 Site #104

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500 1000 1500 depth (cm) Electiral Conductivity Site #76 Site #104

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1000 2000 3000 4000 depth (cm) Soluble Sulphate Site #76 Site #104

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0.000 0.500 1.000 depth (cm) Ba (ppm in HCl) Site #76 Site #104

SLIDE 24

Risk assessment must rely on solubility and bio-availability of barium

What is the concentration of SO4

2??

SLIDE 25

Molar concentrations of water soluble sulphate in the soil exceed that of leachable barium by factors of 105 Barium in these soils is inert and harmless

SLIDE 26

Long Term Effects of Municipal Sewage on Soils and Pastures at Werribee Sewage Farm

Environmental Science and Health (Part A), vol. 37(4), 745-757, 2002 Robert H.M. van de Graaff, Helen C. Suter, Sophy B. Lawes

SLIDE 27

Site Information

Commenced 1897
Size 10,900 ha
Annual Rainfall 500-550 mm
Annual Evaporation 1,400 mm
Weekly Irrigation Flow 1,743 ML
Average Irrigation Application 11.2

ML/ha.year

SLIDE 28

Soils of the Werribee Farm

Basalt and alluvial basaltic and sedimentary

parent material

Texture contrast soils (Duplex soils)

– Medium to heavy clay subsoils, high shrink swell

Free CaCO3 at 30 cm depth
pH 5-7 (surface) to 8-9 (subsoil)

SLIDE 29

Disposal of Sewage

Treatment in Lagoons and Discharge to Bay

46%

No Treatment and Irrigation 54%

SLIDE 30

Table 1. Mean Heavy Metal and Total P content (mg/L) in raw sewage and annual loading to soil by irrigation kg/ha (1) and moles/ha (2)

Cd Cr Cu Fe Hg Ni Pb Zn Total P Raw sewage (mg/L) 0.11 0.59 0.25 2.28 0.002 0.09 0.22 0.77 10.8 Annual Loading (1) 1.77 9.45 4.07 36.71 0.32 1.45 3.51 12.40 174 Annual loading (2) 15.8 181.7 64.1 657.3 1.6 24.7 16.9 189.7 5615

SLIDE 31

Heavy Metal Transfer Soil to pasture to animal tissue

Note: Zn is essential micro-nutrient; Pb is not

Data taken from Evans et al. (1978) Heavy Metal Accumulation in Soil Irrigated by Sewage and Effect in Plant-Animal Systems (Figure 3).

180 15 0.07 9 2.3 125 12 1.12 10 3.4 0.93 240 171 155 30 45 139

50 100 150 200 250 300 Soil Pasture Liver Metal (mg/kg)

Cr-irrigated Cr-non irrigated Pb-irrigated Pb-non irrigated Zn-irrigated Zn-non irrigated

SLIDE 32

Heavy Metal Transfer Soil to pasture to animal tissue

Note: Cu is essential micro-nutrient, Ni is not

Data taken from Evans et al. (1978) Heavy Metal Accumulation in Soil Irrigated by Sewage and Effect in Plant-Animal Systems (Figure 3).

47 22 5.1 17 11 44 36 6.3 11 1.9

10 20 30 40 50 Soil Pasture Liver Metal (mg/kg)

Cu-irrigated Cu-non irrigated Ni-irrigated Ni-non irrigated

SLIDE 33

Heavy Metal Transfer Soil to pasture to animal tissue

Note: Cd is not an essential micro-nutrient

Data taken from Evans et al. (1978) Heavy Metal Accumulation in Soil Irrigated by Sewage and Effect in Plant-Animal Systems (Figure 3).

2.4 1.1 0.38 0.3 0.19 0.17

0.5 1 1.5 2 2.5 3 Soil Pasture Liver Metal (mg/kg)

Cd-irrigated Cd-non irrigated

SLIDE 34

Monitoring of site

Land and Grass Filtration sites

– Soil sampling 0-10, 10-20 cm twice per year – Herbage twice per year

Wastewater

– Flow every 2 weeks – Composition monthly

SLIDE 35

Outcome of monitoring

Years 1976 to 1993
Heavy metals – Soil

– Accumulation of all metals except topsoil Zn – Greater concentration of all metals in topsoil compared to subsoil, in both treatments – Greater concentration of all metals in topsoil under grass filtration compared to land filtration

– Note: Only 2 years of data for Fe showing no trend

SLIDE 36

Outcome of monitoring

Heavy metals –Soil

– Greater rate of accumulation in topsoil than subsoil – Greater rate of accumulation in subsoil from grass filtration than from land filtration for all metals except Zn – Little difference in accumulation rate in topsoil between sewage treatments

SLIDE 37

Figure 1 Cadmium in topsoil (0-10 cm) under land filtration and grass filtration

Grass Filtration, Cd = 0.032 x + 2.621 Land Filtration, Cd = 0.032 x + 0.682

2 4 6 8 10 12 14 16 18 20 Aug-76 May-78 Feb-80 May-82 Aug-84 Feb-86 Apr-88 Jan-90 Feb-92 Dec-93

Cd (mg/kg)

Grass Filtration Land Filtration

SLIDE 38

Figure 2 Cadmium in subsoil (10-20 cm) under land filtration and grass filtration

Grass Filtration, Cd = 0.056 x + 0.3774 Land Filtration, Cd = 0.040 x – 0.497

2 4 6 8 10 12 Aug-76 May-78 Feb-80 May-82 Aug-84 Feb-86 Apr-88 Jan-90 Feb-92 Dec-93 Cd (mg/kg)

Grass Filtration Land Fitration

SLIDE 39

Figure 3 Cadmium in soil under grass filtration

0-10 cm, Cd = 0.032 x + 2.621 10-20 cm, Cd = 0.056 x + 0.377

4 8 12 16 20 Aug-76 May-78 Feb-80 May-82 Aug-84 Feb-86 Apr-88 Jan-90 Feb-92 Dec-93 Cd (mg/kg)

Soil 0-10 cm Soil 10-20 cm

SLIDE 40

Figure 4 Lead in soil under land filtration

0-10 cm, Pb = 0.046 x + 81.694 10-20 cm, Pb = 0.273 x + 24.162

50 100 150 200 250 300 Aug-76 May-78 Feb-80 May-82 Aug-84 Feb-86 Mar-88 Jul-89 Jul-91 Dec-93 Pb (mg/kg)

0-10 cm 10-20 cm

SLIDE 41

Figure 5 Lead in soil under grass filtration

0-10 cm, Pb = 0.4877x + 126.81 10-20 cm, Pb = 0.849x + 42.344

100 200 300 400 500 600 700 800 Aug-76 May-78 Feb-80 May-82 Aug-84 Feb-86 Apr-88 Jan-90 Feb-92 Dec-93 Pb (mg/kg)

0-10 cm 10-20 cm

SLIDE 42

Figure 6 Lead in subsoil (10-20 cm) under land and grass filtration

Grass Filtration, Pb = 0.849x + 42.344 Land Filtration, Pb = 0.2733x + 24.162

100 200 300 400 500 600 Aug-76 May-78 Feb-80 May-82 Aug-84 Feb-86 Apr-88 Jan-90 Feb-92 Dec-93 Pb (mg/kg)

Grass Filtration Land Filtration

SLIDE 43

Figure 7 Cadmium in herbage under land filtration and grass filtration

Grass filtration, Cd = -0.00002 x + 0.167 Land filtration, Cd = -0.0014 x + 0.345

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Nov-76 Oct-78 Jun-80 May-82 Aug-84 Jan-86 Apr-88 Sep-89 Jul-91 May-93 Cd (mg/kg)

Grass filtration Land filtration

SLIDE 44

Figure 6 Lead in herbage under land filtration and grass filtration

2 4 6 8 10 12 Nov-76 Oct-78 Jun-80 May-82 Aug-84 Jan-86 Apr-88 Sep-89 Jul-91 May-93 Pb (mg/kg)

Grass filtration Land filtration

Grass Filtration, Pb = -0.019 x + 2.2694 Land Filtration, Pb = -0.017 x + 3.1731

SLIDE 45

Findings of other authors: Evans, Mitchell and Salau (1978)

Cd, Cr, Pb and Zn accumulate mostly in the top 20

cm in the irrigated soil

Highest amount of Cd, Cr, Pb and Zn in 0-5 cm

depth (organic matter)

Cu and Ni have zones of higher metal

concentration (bulges) between 30-50 cm depth in both irrigated and control soils

Calculated accumulation rates for top 5 cm

Evans, K.J., Mitchell, I.G. and Salau, B. (1978) Heavy Metal Accumulation in Soils Irrigated by Sewage and Effect in Plant-Animal System, MMBW.

SLIDE 46

10 20 30 40 50 60 1 2 3 Content (mg/kg) Depth (cm)