DENITZA VOUTCHKOVA PHD FELLOW AARHUS UNIVERSITET 22. AUGUST 2012 Multivariate Analysis of Danish Historical Hydrogeochemical Data with Respect to Iodine

DENITZA VOUTCHKOVAPHD FELLOW

AARHUSUNIVERSITET

22. AUGUST 2012

Multivariate Analysis of Danish Historical Hydrogeochemical Data with Respect to Iodine in Groundwater

AUSESEH 2012Sino-European Symposium on Environment and Health (SESEH 2012)Galway, Ireland, August 20 - 25, 2012

AARHUSUNIVERSITET

SESEH 2012DENITZA VOUTCHKOVA

22. AUGUST 2012

WHO ARE WE?

› Danish project, financed by Geological Survey of Denmark and Greenland (GEUS) and Aarhus University (2011- 2014):

““Iodine in the hydrological cycle in Denmark: Iodine in the hydrological cycle in Denmark: implications for human health“implications for human health“

2

summaryresultsdatapurposeiodine in dk

AARHUSUNIVERSITET


22. AUGUST 2012

IODINE IN DENMARK

3

Europe

Denmark› Mild iodine deficiency Mild iodine deficiency based on median UI = 50-99ug/l (WHO, 2007)

subnational survey data: 2 cohorts

› MandatoryMandatory fortification since 2000 (13mg/kg)

› ~25%~25% of iodine intake in the Danish diet is derived from drinking drinking waterwater, coffee, tea and other beverages (Rasmussen et al., 2000)

› Iodine in drinking water Iodine in drinking water in Denmark varies from 0,7ug/l to 0,7ug/l to 140ug/l140ug/l (Pedersen et al., 1999, Andersen et al., 2002)

› Danish drinking water is ~100% with groundwater origin groundwater origin


AARHUSUNIVERSITET


22. AUGUST 2012

PURPOSE OF THE STUDY

Iodine in Denmark is not studied is not studied from geochemical point of view

We want to:•map and explain the spatial variations;•understand the involved processes;•find the source(s) of iodine in the groundwater in Denmark;

HOW?By MVD exploration of the different data we have and hydrogeochemical interpretation of the results


limestone

gwt

dry and wetI deposition

volatilisation

volatilisation

uptake

topsoil

iodine cycle in the ocean

leaching

org. Iinorg. I

reduction

Sea water intrusion

Upward transport of old saline water

diffusion

bioaccumulationdecomposition

aquitard sorption

desorptionaquifer

Marine deposits

Conceptual model of iodine cycle in Denmark

AARHUSUNIVERSITET


22. AUGUST 20125

• 26 chemical variables26 chemical variables: I, Li, H2S, CH4, O2, Agg. CO2, NVOC, PO4, SO4, NO3, K, Fe, Mn, HCO3, Ca, Mg, Na, Cl, Fl, B, Ba, Br, Sr, conductivity, redox, pH;

• Geology Geology at the well screen;

• Lab methods

Calculated in ArcMap:• Distance to the coastlineDistance to the coastline• Distance to major geological Distance to major geological

faults faults

AVAILABLE GROUNDWATER DATAJUPITERJUPITER is the Danish nationwide database of groundwater and drinking water (http://www.geus.dk/jupiter/data-dk.htm)


AARHUSUNIVERSITET


22. AUGUST 2012

IODINE DATA

6

Number of Iodine samples

Status December 2011: 2562 samples


Iodine in groundwater (n=2562) for the period 1933-2011

AARHUSUNIVERSITET


22. AUGUST 2012

DATA PREPARATION FOR MVDA

› Dataset cleaningcleaning (excluded all additional information coming from Jupiter)

› Data qualityquality assessment› Iodine data inhomogeneity

due to analytical method› Values below detection limit› Errors

› Dataset reductionreduction› Reduction of variables › Reduction of samples

7

28 variables2562

samples

Lots of missing values

20 variables505 samples

Few missing values


AARHUSUNIVERSITET


22. AUGUST 2012

MVDA STRATEGY

8

7PC7PC needed to explain

75% 75% variance

structure

noise


Principal Component Analysis

We found 3 groups of samples showing multivariate structure on the first 3 PCs and analysed them further

AARHUSUNIVERSITET


22. AUGUST 2012

PLS-R MODEL

9

Partial Least Squares Regression Model

R²=0,76 (3 PCs, 75% of the variance)Slope 0,77

Calibration Validation

Factors

Factor-0 Factor-1 Factor-2 Factor-3 Factor-4 Factor-5 Factor-6 Factor-7 Factor-8 Factor-9

Y-v

aria

nce

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1Residual Variance

3PC3PC neededTo explain75%75% of the variance

validation

calibration

1:1

noisedata


AARHUSUNIVERSITET


22. AUGUST 201210

RESULTS AND INTERPRETATION

Factor-1 (34%, 48%)

-0,3 -0,2 -0,1 0 0,1 0,2 0,3 0,4 0,5

Fac

tor-

2 (1

1%,

31%

)

-0,4

-0,3

-0,2

-0,1

0

0,1

0,2

0,3

0,4

0,5

X-loading Weights and Y-loadings

DIST_FAULT

DIST_COAST

SR2126

CL1591

BR1542

BA1516

BOR1536 NA2096

MG2081

CA1551

BIK305

MN2086

FE204X

K2056

LED0011

PHX

NO3X

SO4_2142

LI2076

JOD2051Iodine Ba

HCO3

Br Na

Fe

SO4Ca

K Cl

cond.

B Sr

Li

NO3

Mn

pHfaults

coast

Mg

Sønderborg

Jammerbugt

Ishøj

Gladsaxe

København

Lejre

Frederiksberg

Interpretation based on the Loading Weights plot Loading Weights plot and Score plot Score plot (PC1-PC2)


Other factors (location and water quality): geology, screen depth, municipality, Na/Cl ratio, Cl/Br ratio, Redox, SI

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22. AUGUST 2012

SUMMARY› It is possible to studyIt is possible to study the groundwater origin and the

processes governing the water composition by MVDA;

› Important factors Important factors for the Iodine variation,based on the PLS-R model:

› Future:Future: smaller scale studiesfocus on the geochemistry; groundwater/drinking water; connection to the human health;

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Documents

DENITZA VOUTCHKOVA PHD FELLOW AARHUS UNIVERSITET 22. AUGUST 2012 Multivariate Analysis of Danish Historical Hydrogeochemical Data with Respect to Iodine