New techniques for improved decision-making in contaminated land risk assessment

Brownfield & Contaminated Land

11th May 2017

Rebekka McIlwaine

Siobhan Cox

Historical development and its effect on soil contamination in urban areas

Rebekka McIlwaine Rory Doherty Siobhan Cox Mark Cave Society of Brownfield Risk Assessment (SoBRA) funded project

Historical development and its effect on soil contamination in urban areas

• Study areas: Belfast and Sheffield • Elements: Arsenic, Cobalt, Chromium, Copper,

Molybdenum, Nickel, Lead, Antimony, Tin, Vanadium, Zinc

• Source identification: data analysis • Historical development • ‘Typical’ concentrations

Study area: Belfast

• History of linen production (from early 18th Century) and ship building (late 18th Century)

• Varied bedrock geology, known to control PTE concentrations – Basalts to the north – Sherwood sandstone – Greywacke to the south

Belfast

Tellus geochemical soil samples

Inorganics 4 samples per km2

781 samples

Geochemical Datasets

Shallow sample at 5 - 20cm depth

Shallow sample at 5 - 20cm depth

Deep sample at 35 – 50cm depth

X-ray fluorescence Inductively coupled plasma following aqua regia digest Inductively coupled plasma following aqua regia digest

Source Identification

Data analysis

• Various analyses were carried out: SPATIAL – Interpolated maps

STATISTICAL – Inspection of contaminant distributions (skewness and kurtosis) – Depth ratio boxplots – Cluster analysis – Principal component analysis

Belfast: Depth comparison

• Anthropogenic – more likely to be

elevated at surface (ratio >1)

– Less likely to have lower outliers

– Wider distribution • Geogenic

– more likely to be elevated at depth (ratio <1)

– More likely to have lower outliers

Belfast: Principal Component Analysis

Source Identification: skewness and kurtosis

• Skewness measures symmetry in the data

• Kurtosis measures whether the data has a ‘tail’

• Generally geogenic contaminants in the bottom left corner

Less symmetry

and greater ‘tail’

Historical development

Historical development

• Boundaries taken from the extent of urbanised areas on OS mapping

• Belfast – 1858 – 1901 – 1919-1939 – Current

Historical development

• Spatial distribution of Pb in surface soils

• Relatively uncontaminated area in the centre of the city

• Halo of contamination around this

Historical development

Belfast: Pollution Indices

• PI = Uc/Rc (Uc = median urban conc., Rc = median rural conc.)

• Co, V, Cr & Ni – highest PI Current Belfast

• Pb – highest 1901

• All others – highest 1919-1939

• Pb and Sn show considerably higher enrichment

Typical concentrations

Can we calculate ‘typical’ values?

• ‘Typical’ or ‘background’ values • Do not assess risk – provide

‘typical’ concentrations of a compound or element

• UK approach defines background levels as both geogenic and diffuse anthropogenic in origin – ‘Normal Background Concentration’ (NBC)

• Finland - ‘Upper Limit of Geochemical Baseline Variation’ (ULBL)

Typical Threshold Values – Northern Ireland

• Example - Nickel • Identify domains

Ni (mg/kg) 1.45 – 3.55 3.56 – 10.47 10.48 – 25.12 25.13 – 44.67 44.68 – 112.2 112.21 – 165.96 165.97 – 234.42 234.43 – 372.2

Calculating Typical Threshold Values

NBC approach (Cave et al 2012) (needs at least 30 data points) 1. Assess skewness of data 2. Perform data transformation (log or box cox) 3. Determine percentiles (parametric, robust or empirical methods) 4. NBC: the upper 95th confidence limit of the 95% percentile

Calculating Typical Threshold Values

ULBL approach (Jarva et al 2010) • ULBL is the upper limit of the upper whisker line of the box and whisker plot

Typical Threshold Values – Northern Ireland

ULBLX =P75 + 1.5 × (P75−P25)

Upper limit of geochemical baseline variation

Nickel domain TTV (mg/kg) Basalt 250

Mournes 11 Peat 33

Principal 88

Calculating Typical Threshold Values - urban

NBC method ULBL method ‘MAD’ method (Reimann et al., 2005) • Uses the median and median absolute deviation (MAD) where:

Geochemical background = median + 2xMAD • Accepted in Gateshead by local authority as method by which to calculate ‘Normal Background Concentrations’

Typical Threshold Values for Belfast’s development zones (mg/kg)

1858 1901 1919-1939 Modern

S4UL

Lowest

value

ULBL M

+2MAD NBC * ULBL

M

+2MAD NBC ULBL

M

+2MAD NBC ULBL

M

+2MAD NBC

As 18 13 - 21 15 BC 37 26 17 E 52 19 14 L 21 37 **

Cu 120 95 - 160 100 BC 210 200 120 BC 640 120 80 L 130 520 +

Mo 2.8 1.8 - 3.5 2.4 L 4.7 5.1 3.0 E 18 2.7 1.8 L 3.1 -

Pb 190 140 - 430 280 L 490 620 270 BC 1300 200 120 L 260 34 ++

Sb 2.7 1.9 - 4.3 3.1 L 10 7.2 3.7 BC 33 3.0 2.1 L 4.3 -

Sn 16 11 - 20 14 L 33 51 18 BC 1000 14 7.7 BC 24 -

Zn 240 210 - 310 220 L 470 510 290 BC 2100 240 170 L 290 620 +

• * Insufficient samples

• ** Residential with homegrown produce +Allotments ++pC4SL for allotments

(BC = box-cox transformation, L = log transformation and E = empirical)

Conclusions

• Potential sources of elements in soil can be identified using: – Depth ratios, cluster analysis and PCA (and also

skewness and kurtosis) • These methods could also be used to identify elements with

geogenic and anthropogenic sources in Sheffield • Historical development in Belfast and Sheffield is linked to

element contamination, with elevated levels of Pb, Sn and Sb in particular being associated with development in the early 20th Century

• Further work is needed to assess risks associated with this….

Further details

• The final report from this study is available on the SoBRA website

• McIlwaine, R., Doherty, R., Cox, S.F., Cave M. R. (2017) The relationship between historical development and potentially toxic element concentrations in urban soils. Environmental Pollution, 220(B): 1036-1049 http://dx.doi.org/10.1016/j.envpol.2016.11.040

What next?

Total versus Bioavailable Contamination

• McIlwaine et al. 2017 considered the total concentration of elements in soils

• Most risk assessment models assess exposure to total contamination through: – Inhalation – Ingestion – Dermal contact

• For many inorganic contaminants ingestion is the principal pathway • However, once ingested, contamination has to leave the soil and

enter the bloodstream to be able to cause toxic effects • It is less conservative to consider the bioavailable or bioaccessible

concentrations of elements in the soil

Bioavailability and bioaccessibililty

(Cave et al., 2011)

Bioavailability and bioaccessibililty

• Oral bioavailability: The degree to

which a substance is absorbed and becomes available to the target tissue (without first being metabolised) (CIEH, 2009).

• Oral bioaccessibility: The degree to which a chemical is released from soil into solution (and thereby becomes available for absorption) when that soil is ingested and undergoes digestion (CIEH, 2009). – Generally less than or equal to the

bioavailable fraction

Measured by: • In-vivo:

Juvenile swine

• In-vitro: in a test tube in the lab

Measuring bioaccessibility: The Unified BARGE Method (UBM)

• Bioaccessibility test developed by the BARGE group (including BGS)

• Simulates the gastric (G) and gastro-intestinal (GI) phase

• Undergone inter-laboratory trials (Wragg et al., 2011)

• Validated against in-vivo testing for Cd, Pb and As (Denys et al., 2012)

• ISO Technical Specification 17924 www.bgs.ac.uk/barge

What factors affect oral bioaccessibility

• Mineral form • Particle size • Encapsulation • Chemical species

• Also:

– pH – SOM

(Cave et al., 2011)

Oral bioaccessibility testing in Northern Ireland

• UBM testing of 91 soil samples across NI (Barsby et al. 2012)

• UBM testing of 145 samples (incl Barsby dataset) for Ni, V and Cr across NI (Palmer et al. 2014)

• Detailed investigations of Ni & Cr bioaccessibility in soils overlying the Antrim basalts (Cox et al. 2013 & Cox et al. 2017)

(Barsby et al., 2012)

What next? Oral bioaccessibility testing for Belfast

• Set up the UBM in QUB

• Selected 100 samples for UBM testing

• Includes different – land uses – geology – development

zones

How do we use bioaccessibility testing in Risk Assessment?

• Sets out – how to use

bioaccessibility testing in risk assessment

– Common misuses – Common myths

• However bear in mind it was

written before the UBM method was developed!!

How do we use bioaccessibility testing in Risk Assessment?

• QUB deriving graphs of GACs for varying BAF for a variety of contaminants & land uses based on S4ULs

– Methodology adapted from Scott and Nathanail, 2011

0

100

200

300

400

500

600

700

800

900

1000

0 10 20 30 40 50 60 70 80 90 100

Arse

nic

GAC

(mg/

kg)

Arsenic BAF (%)

GAC for Inorganic Arsenic with changing oral bioaccessible fraction (BAF)

GAC Res with Produce S4UL Res with Produce

GAC Res without Produce S4UL Res without Produce

37 mg/kg 40 mg/kg

0

500

1000

1500

2000

2500

3000

0 10 20 30 40 50 60 70 80 90 100

Arse

nic

GAC

(mg/

kg)

Arsenic BAF (%)

GAC for Inorganic Arsenic with hanging oral bioaccessible fraction (BAF)

GAC POS resi S4UL POS res GAC POS park S4UL POS park

Acknowledgments

This research was funded by an Annual Scholarship from the Society of Brownfield Risk Assessment (SoBRA)

Bioaccessibility testing was undertaken as oart of the REMEDIATE project funded from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 643087

The Tellus project was funded by the Department of Enterprise Trade and Investment and by the Rural Development Programme through the Northern Ireland Programme for building sustainable prosperity.

References

• Cave, M.R., Wragg, J., Denys, S., Jondreville, C., Feidt, C., 2011. Oral Bioavailability, in: Swartjes, F.A. (Ed.), Dealing with Contaminated Sites. Springer Netherlands, pp. 287–324. doi:10.1007/978-90-481-9757-6_7

• Chartered Institute of Environmental Health (CIEH), 2009. Professional Practice Note: Reviewing human health risk assessment reports invoking contaminant oral bioavailability measurements or estimates.

• Denys, S., Caboche, J., Tack, K., Rychen, G., Wragg, J., Cave, M., Jondreville, C., Feidt, C., 2012. In vivo validation of the unified BARGE method to assess the bioaccessibility of arsenic, antimony, cadmium, and lead in soils. Environ. Sci. Technol. 46, 6252–60. doi:10.1021/es3006942

• Scott DI & Nathanail CP, 2011. Generic human-health assessment criteria for arsenic at former coking works sites. CL:AIRE Research Bulletin RB14. CL:AIRE, London, UK. ISSN 2047-6450

• Wragg, J., Cave, M., Basta, N., Brandon, E., Casteel, S., Denys, S., Gron, C., Oomen, A., Reimer, K., Tack, K., Van de Wiele, T., 2011. An inter-laboratory trial of the unified BARGE bioaccessibility method for arsenic, cadmium and lead in soil. Sci. Total Environ. 409, 4016–30. doi:10.1016/j.scitotenv.2011.05.019

References: Research about soil contamination and bioaccessibility in Northern Ireland

• Barsby, A., McKinley, J.M., Ofterdinger, U., Young, M., Cave, M.R., Wragg, J., 2012. Bioaccessibility of trace elements in soils in Northern Ireland. Sci. Total Environ. 433, 398–417. doi:10.1016/j.scitotenv.2012.05.099

• Cox, S.F., Chelliah, M.C.M., McKinley, J.M., Palmer, S., Ofterdinger, U., Young, M.E., Cave, M.R., Wragg, J., 2013. The importance of solid-phase distribution on the oral bioaccessibility of Ni and Cr in soils overlying Palaeogene basalt lavas, Northern Ireland. Environ. Geochem. Health 35, 553–567. doi:10.1007/s10653-013-9539-6

• Cox, S., McKinley, J. & Rollinson, G., 2017. Mineralogical Characterisation to improve understanding of oral bioaccessibility of Cr and Ni in Basaltic Soils in Northern Ireland. Journal of Geochemical Exploration. doi: 10.1016/j.gexplo.2017.02.006

• McIlwaine, R., Cox, S.F., Doherty, R., Palmer, S., Ofterdinger, U., McKinley, J.M., 2014. Comparison of methods used to calculate typical threshold values for potentially toxic elements in soil. Environ. Geochem. Health 36, 953–971. doi:10.1007/s10653-014-9611-x

• McIlwaine, R., Doherty, R., Cox, S.F., Cave M. R. (2017) The relationship between historical development and potentially toxic element concentrations in urban soils. Environmental Pollution, 220(B): 1036-1049 http://dx.doi.org/10.1016/j.envpol.2016.11.040

• Palmer, S., Cox, S.F., McKinley, J.M., Ofterdinger, U., 2014. Soil-geochemical factors controlling the distribution and oral bioaccessibility of nickel, vanadium and chromium in soil. Appl. Geochemistry 51, 255–267. doi:10.1016/j.apgeochem.2014.10.010