The role of portable XRF in contaminated land investigation Moanataiari: a case study

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1 The role of portable XRF in contaminated land investigation Moanataiari: a case study Joanne Ferry (Tonkin & Taylor) Kerry Laing (Kerrich Environmental)

3 Background Phase 1 Desk study and limited soil sampling commissioned by WRC in 2011 Results indicated mine waste was present beneath the site and elevated concentrations of metals were present Moanataiari Project Team established Project Management Group Governance Group

4 Introduction Phase 2 Detailed site investigation of 206 residential properties and one ECC Undertaken by T&T between January - May 2012 This paper focuses on the use of the portable XRF as part of the Phase 2 investigation

5 Soil sampling Up to 3 hand augers at each property Samples collected from 0.0, 0.5 and 1.0m depth 1 duplicate sample from each property 544 investigation locations 1,668 soil samples collected

6 Analysis methodology Key potential contaminants identified from previous work - arsenic, cadmium, chromium, copper, mercury, nickel, lead, zinc, antimony, thallium All samples analysed with portable XRF including QA samples 25% of samples analysed at the laboratory

Analysis methodology Portable XRF methodology Mix the sample inside the plastic bag to achieve a relatively homogenous sample Compress the sample inside the plastic bag to ensure minimum void space

7 Analysis methodology Portable XRF methodology Mix the sample inside the plastic bag to achieve a relatively homogenous sample Compress the sample inside the plastic bag to ensure minimum void space within the sample Undertake a 60 second analysis of the sample through the plastic bag Repeat the analysis on different parts of the sample to achieve three test results for each sample Not consistent with US EPA method 6200

8 Analysis methodology Laboratory analyses 25% of the samples analysed at Hill Laboratories Up to 2 samples from each property with individual lab reports prepared Additional testing on limited samples for more comprehensive range of potential contaminants

9 XRF uncertainty 2 separate XRF units were used during the project Niton XL3t GOLDD+ Omega Express SDD Results from two instruments show good comparison Margin of uncertainty showed significant differences for some analytes

10 XRF uncertainty

11 XRF uncertainty Margin of uncertainty Analyte Niton unit Omega unit Arsenic Cadmium Chromium Copper Mercury Nickel Lead Zinc Antimony Thallium All concentrations in mg/kg

12 XRF uncertainty Analysis methodology US EPA 6300 (ex situ) Mechanically homogenise sample Dry sample Grind and sieve sample No. of replicate analyses not stated Minimum 5% of samples sent to laboratory Moanataiari methodology Some homogenisation Field moisture content Field grain size 3 replicate analyses 25% of samples sent to laboratory Adopted methodology will result in under reporting of results, and more variability between individual samples

13 Lab uncertainty Hill Laboratories standard QA procedures Some samples exhibited high variability but mostly within acceptable range Repeat analyses on selected samples found RPDs <30%

14 Results Results portable XRF Moanataiari School Arsenic concentrations at 0.5m depth (XRF data)

15 Results - Laboratory Analyte Average Maximum % exceeding criteria Tier 1 assessment criteria Arsenic 167 4, Cadmium Chromium Copper Mercury Nickel Lead 181 7, Zinc 196 5, Antimony Thallium All concentrations in mg/kg

16 XRF/lab comparison Very good relationship for some analytes Arsenic Copper Lead Zinc Very poor relationship for others Cadmium, chromium, mercury, nickel, antimony, thallium

17 XRF/lab comparison

18 XRF/lab comparison

19 XRF/lab comparison Analyte Average conc - lab Portable XRF detection limit XRF/lab average RPD (%) r 2 value Arsenic Cadmium Chromium Copper Mercury Nickel Lead Zinc Antimony Thallium

20 XRF/lab comparison Good correlation where average concentration is above the XRF detection limit Poor correlation where average concentration is close to or below the XRF detection limit Impacts of different sample characteristics Surface samples v samples at depth Vegetable gardens v lawn locations

21 Conclusions XRF is an excellent tool in the right circumstances but has many limitations: Instrument may not be set up for all contaminants of concern Not suitable for metals with low assessment/ remediation criteria Not suitable for metals present at concentrations close to the detection limit of the instrument DQOs need to consider potential variability between individual analyses and reported margin of uncertainty Individual XRF instruments may not be comparable Differences in soil types across a site will impact on the ability to compare XRF results

22 Acknowledgements Thames-Coromandel District Council Waikato Regional Council Ministry for the Environment Community of Moanataiari

This paper focuses on the analysis methodology and results of soil sampling from the residential properties during Phase 2 of the project.

This paper focuses on the analysis methodology and results of soil sampling from the residential properties during Phase 2 of the project. THE ROLE OF PORTABLE XRF IN CONTAMINATED LAND INVESTIGATION MOANATAIARI: A CASE STUDY Joanne Ferry (Tonkin & Taylor), Kerry Laing (Kerrich Environmental) 1 Introduction The Moanataiari Project was commissioned