METREAU part II Analysis Division March 10, 2003 1

METREAU Objectives To estimate the uncertainty related to the sampling of groundwater To evaluate the variability in space-time of groundwater chemical composition at the scale of an industrial site To assess the true quality of groundwaters To understand the behaviour of pollutants in groundwater To elaborate appropriate protocols for groundwater sampling > 2 3

METREAU Site Characteristics In the « BIC 2 » borehole Potash production site in France Site Characteristics Groundwater subjected to a specific pollution of heavy metals 3 boreholes located close together In the « BIC 2 » borehole 1996 data: [ Pb ] = 206 µg/l; [ Cd ] = 28,9 µg/l 2002 data: [ Pb ] = 1 µg/l; [ Cd ] = 0.05 µg/l BIC 2 BIC 3 300 m Aval hydraulique BIC 1 3

METREAU Uncertainty estimate related to the sampling stage Estimate by field testings of groundwater sampling repeatability and reproducibility Definition of a specific protocol 1/ On site measurements of chemical and physical parameters versus depth in BIC 2 2/ Sampling at 3 different levels, with 10 samples per level 3/ Specific sampler using gas pressure system 4/ Chemical analysis of major and trace elements by ICP/MS: 26 chemical elements 5/ Statistical data processing 3

METREAU Logs of chemical parameters C T O2 Eh pH Example for BIC 1 3

Uncertainty related to the sampling stage METREAU Uncertainty related to the sampling stage Analyse et Caractérisation Minérale 3

Uncertainty related to the sampling stage In the BIC 2 borehole : No particular layering /stratification of water 3 levels selected, 10 samples collected per level 3 analysis of lead contents in each sample Calculation of the uncertainty related to the sampling step A B C O2 pH Eh T C BIC 2 3

Uncertainty related to the sampling stage lead contents and statistical processing (ANOVA method) [ Pb]A = 0,94 ± 0,16 (18%); n=10 samples [ Pb]B = 1,20 ± 0,33 (28%); n=10 samples [ Pb]C = 0,51 ± 0,12 (24%); n=10 samples Uncertainty related to the sampling stage about 20% for a content of 1 µg/l results in total agreement with analytical uncertainties (close to 3% ; Icp-ms method) 3

Uncertainty related to the sampling stage If we suppose a random sampling in this borehole and then one analysis in lab Estimate of uncertainty based on 30 samples: good estimate of the true value and small uncertainty if not: statistical calculation allows estimation of an unknown value [Pb] content shoul be close to the mean value: 0,88 µg/l Uncertainty will be close to 0,82 µg/l (  100%) 3

Space-time variability of groundwaters METREAU Space-time variability of groundwaters 3

Space-time variability of groundwaters Definition of a specific protocol measurements of chemical parameters logs in each borehole sampling in each layer of each borehole Renewal of field tests repeated over 2 days analysis of major and trace elements: 26 chemical elements About 1400 values available: principal component analysis (PCA) Results PCA: only 4 parameters needed to explain 90% of the variability of data variation 3

Space-time variability of groundwaters BIC 1 BIC 3 BIC 2 Spatial variability of chemical parameters between boreholes 3

Space-time variability of groundwaters BIC 1 level A BIC 1 level. B,C BIC 2 BIC 3 Spatial variability : two factors chemical composition between borehole and depth 3

Space-time variability of groundwaters Results of data processing by PCA Identification of the 4 main effects responsible for spread in data: Analytical effect: sampling + analysis space effect identified between each borehole depth effect identified into two boreholes time effect between D and (D+1) and between July and October samplings Origin of time variation? 3

Time variation Field observation into BIC 2 sample: orange suspended matter containing living micro-organisms 3

Time variation SEM 10000 X SEM 3300 X FeS: pyrite nodules Bacteria 3

Time varition is related to bacterial activity Time variation Results of chemical analysis: organic and suspended matter water sample: BIC 2 [Al]  12740 ppb  1 ppb [Fe]  78490 ppb  200 ppb [Pb]  140 ppb  0,4 ppb [As]  1200 ppb  13 ppb [Zn]  37 ppb  8 ppb Time varition is related to bacterial activity 3

METREAU Conclusions Uncertainty related to the sampling step: Lead content: about 20% for a concentration level close to regulatory limits Uncertainty related to the analytical step: Lead content : about 3% in the case of METREAU Uncertainty of a random sampling on one borehole: Lead content : about 100% Space-time variability on this site strong variability between 3 boreholes located close together 3

Proposal (1) The understanding of natural variations needs specific field protocols for accurate data acquisition Proper assessment of the uncertainty of measurement requires procedures taking into account uncertainty on analysis and on sampling Harmonized validated protocols must be defined at the European level for the sampling of groundwaters to ensure data quality and consistency 3

Proposal (2) Monitoring programmes for implementation of Water Framework Directive need: measurement techniques of demonstrated quality for assessement of water status and to control pollution pressures endangering water status to compare existing rapid techniques and to check their validity to develop innovative « low cost » screening methods 3