Graduate students ofVähätalo

Miika Kuivakko, started 2005, University ofHelsinki, Photochemical decomposition ofbrominated flame retardants in the environment.

Susann Haase, started 2008, University ofHelsinki, The role and importance ofphotochemistry and bacterial processes in sea ice.

Hanna Aarnos, started 2006, University of Helsinki,Photolytic decomposition of natural organic matterin environment.

Continents – ocean interface

12

3

4

56

78

9

10

1 Amazon2 Congo3 Parana4 Lena5 Ganges

+ Brahmaputra6 Mississippi7 Mekong8 Yang Tse9 St Lawrence10 Yukon

• Researchers, who are interested in the coupling betweenthe continents and the ocean are welcome to join oureffort.

• Interesting questions include e.g., global discharge ofheavy metals (Hg, Cd, etc.)pollutants (antropogenic chemicals, POPs)microbes (community structrues)your favorite topic…

Please contanct us:anssi.vahatalo@helsinki.fihanna.aarnos@helsinki.fi

Invitation

DirectDirect Photolyhotolysis ofofPolybrominatedPolybrominated DiphenylDiphenyl EthersEthersin Surface Watersin Surface Waters

Miika Kuivikko1,4, Tapio Kotiaho1,2, Kari Hartonen1,Aapo Tanskanen3, Anssi Vähätalo4

1 Laboratory of Analytical Chemistry, Department of Chemistry, University ofHelsinki.2 Pharmaceutical chemistry, Faculty of Pharmacy, University of Helsinki3 Finnish Meteorological Institute, UV Radiation Research4 Department of Biological and Environmental Sciences, University of Helsinki.

Contents

• Introduction• Objectives• Photolytical Experiments• Optical Model• Results• Conclusions

Introduction• Polybrominated diphenyl ethers (PBDE)are additives in plastics (e.g. electrichousing, upholstery textiles, mobilephones etc.)

• Annual global PBDE-production is67 000 t

• PBDEs are used to prevent or minimizefire damage

Introduction• PBDEs are ubiquitous in theenvironment and they have endocrinicand neurotoxic effects in mammals

• PBDE resist microbial decomposition inthe presence of oxygen, but candecompose through microbial reductivedehalogenation in anaerobic envi-ronment

• Photolysis can debrominate PBDEs

Objectives

• Study the direct photolysis ofdissolved PBDEs

• Calculate the direct photolytic half-lives of PBDEs in the Baltic Sea andNorth Atlantic Ocean

• Calculate seasonal latitudal half-livesof PBDEs in North Atlantic Ocean

Photolytical Experiments• For the photolytical experiments, the PBDEs,2,2',4,4'-tetrabromodiphenyl ether (#47)2,2',4,4',5-pentabromodiphenyl ether (#99)2,2',3,3'4,4',5,5',6,6'-decabromodiphenyl ether (#209),in isooctane were introduced into custom made quartzGC-autosampler vials. The vials were placed into apool on the roof at Helsinki, Finland (60°20’N 24°97’E)

• PBDEs were analysed during the experiments withan GC-EI-MS (Agilent model 6890/5973)

Photolytical ExperimentsGC parameters for #209GC column, 7-5 m long DB-5MS (id. 0.25 mm and 0.1 µm film), 3-1 m long retention gap (id. 0,53 mm) gas flow: 1,8 ml/min, oven:90-320 °C (25 °C/min), injection: On-column, injection volume 1µl, GC-MS interphase: 320 °C

GC Parameters for #47 and #99GC column 14 m long HP-5MS (id. 0.18 mm and 0.18 µm film)and 3-5 m long retention gap (id. 0,53 mm), gas flow: 0,9 ml/min(constant flow), oven: 50-300 °C (25 °C/min)

MS parameterssolvent delay: 2 min, quadrupole temperature 200 °C, ion sourcetemperature 250 °C, electron energy 70 eV, SIM: 325.9 m/z for#47, 403.8 m/z for #99 and 399.7 m/z #209

Photolytical Experiments

The specific absorptivities of PBDEs in isooctane(50 µg ml-1) and mean solar irridiances inHelsinki on July 7. 2005.

0

500

1000

1500

2000

300 320 340 360 380 4000.00

0.25

0.50

0.75

1.00

Mol

ar a

bsor

ptiv

ity

(M-1

cm-1

)

Sola

r ir

radi

ance

(Wm

-2nm

-1)Spectrophotometer ( Gary 100, Varian)

scanning rate of 30 nm min-1, slit of 2nm and a 10 mm quartz cuvette

#209#99

#47

Photolytical Experiments• Three samples, dark control (wrapped inaluminium foil) and Isooctane (blank) for eachof the time point• Initial concentration was 250 pg/µl (isooctane)• Experiment Setup for #209:

(Q) Quartz, (G) Glass

O min 15 min 30 min 45 min 60 min

Sample (Q)

Control (G)

Blank (G)

Photolytic Experiments

Optical Model• Solar radiation(direct+diffuse) incident tothe pool, was calculatedusing radiative transfer code(Disort 2, libRadtran), FMI• Number of photonsabsorbed by the PBDEs inthe pool was calculated usingMatlab (v. 6.5)*

* Vähätalo, A. V.; Salkinoja-Salonen, M.; Taalas, P.; Salonen, K. Spectrum of the quantum yieldfor photochemical mineralization of dissolved organic carbon in a humic lake. Limnol.Oceanogr.2000, 45, 664-676.

VIAL

POOL

DIFDIR

Optical Model, Quantum Yield

Photolytic decomposition rates of thecongeners were related to the number ofabsorbed photons (Qa) to determineapparent quantum yields ( )

PBDE = PBDE Qa-1

Optical ModelDecomposition of PBDEs at the surface (mol m-3 d-1)

Qz, ,s = scalar photon flux density at the depth of z and wavelength(mol photons m-2 d-1nm-1)

aPBDE, = absorption of the PBDE (m-1 nm-1)

PBDE = quantum yield (mol PBDE / mol absorbed photons-1)

= 300-400 nm

daQPBDE PBDE

max

min,PBDES,,Zz

Optical Model

Decomposition of PBDEs in the mixing stratum (mol m-2 d-1)

Qabs, = Photon flux density absorbed by the water column(mol photons m-2 d-1)

atot, = total absoprtion of the water column (m-1 nm-1)

da

aQPBDE PBDE

tot

PBDEabs

,

,max

min,

Optical Model, Case I vs Case II

Baltic Sea (Case II)

Atlantic Ocean(Case I)

Optical Model, Case I vs Case II

Tota

lAbs

orpt

ion

coef

ficie

nt(m

-1)

Wavelength (nm)

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

300 310 320 330 340 350

1.00E-15

1.00E-14

1.00E-13

1.00E-12

1.00E-11

#99

BS

AO

Total Absorption of the Baltic Sea (AO), Atlantic Ocean (AO, 23°N 30°W),and #99 (concentration of 30 pg/l).

Br

Br

Br

Br

Br

Br

Br

Br

Br Br

O

Br

Br

Br

Br Br

O

Br

Br

Br Br

O

Results, Decomposition of PBDEs

-4

-3.5-3

-2.5

-2

-1.5-1

-0.5

00 2 4 6 8 10 12 14

Time (d)

CB

A

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0

0 10 20 30 40 50 60

ln(C

0/C)

A

Time (min)

A) B) C)

Results, Quantum Yield

0.56 0.16

-

0.38 0.10

Qs (THF)*

0.22 0.05

0.16 0.02

0.28 0.04

Qs (isooctane)

0.63#47

-#99

0.29#209

Qs (THF)**PBDE

*= Palm, W.-U.; Sossinka, W.; Ruck, W.; Zetzsch, C. Environ. Toxicol.Chem. 2004.** = Eriksson, J., Green, N., Marsh, G., Bergman, Å., Environ, Sci technol., 2004THF = Tetrahydrofuran

Results, half-lives (d) Case I vs Case II

0.4

27

115

AtlanticOcean (M)

1.8

121

526

Baltic Sea(M)

Mixing layer(3-4 pg l-1)

0.020.03#209

1.41.4#99

8.48.5#47

Baltic Sea(M)

Isooctane(O)

PBDE

Surface

O = Observed ja M = Modeled

Results, Seasonal half-lives in NorthAtlantic Ocean

•Seasonal half-lives (latitudes 0,20,40,60 °N)of PBDEs were calculated using:

-Seasonal changes in solar radiation-Seasonal changes in mixing layerdepth-Seasonal changes in naturalabsorbing component (CDOM andparticles) concentrations

100d

Winter

X 10

t½= 2930 d

t½= 202 d

t½= 32 d

t½= 9 d0°N

20°N

40°N

60°N

30°W

Spring t½= 188 d

t½= 43 d

t½= 7 d

t½= 13 d

0°N

20°N

40°N

60°N

30°W

Summert½= 27 d

t½= 5 d

t½= 5 d

t½= 12 d0°N

20°N

40°N

60°N

30°W

Autumnt½= 585 d

t½= 17 d

t½= 11d

t½= 12 d

0°N

20°N

40°N

60°N

30°W

Conclusions

• The surface half-lives overestimatethe photolytic half-lives in the mixingstratum, which is the most relevant forestimating the environmental fate of thePBDEs.

• Study shows that the naturalabsorbing components and the depthof mixing stratum affect greatly thephotolytic half-life of PBDEs in thesurface waters

Acknowledgements

• Pyranometer data: Pasi Kallio jaMarkku Kulmala (University of Helsinki)

• Baltic Sea Optics: Jukka Seppälä,Pasi Ylöstalo (FIMR) & WASI 2005

• Atlantic Ocean data: RV Pelagia &crew, Gerhard Herndl (NIOZ)

• Maj ja Tor Nessling foundation forfunding

Summer 2008, Tvärminne

Br

Br

Br

Br Br

O

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

00 10 20 30 40 50

Summer 2008, Tvärminne

Photolysis (ng L-1 d-1)D

epth

(m)

Photolysis,z = 37 e-6.9 z

Photolytic half life (depth 0 m)= 5.7 d

Br

Br

Br

Br Br

O

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

00 10 20 30 40 50

Summer 2008, Tvärminne

Photolysis (ng L-1 d-1)D

epth

(m)

Photolysis,z = 37 e-6.9 z

Photolytic half life (depth 0 m)= 5.7 d

Br

Br

Br

Br Br

O

Open position for a post-doc

•Project: “Preventing the presence ofpersistent anthropogenic chemicals inthe environment”

•Funded by Helsinki University Centrefor Environment (HENVI) 2009-2011

•Aim: Develop methods, which estimatethe photolytic turnover of (future)chemicals in the environment.

•Contact: anssi.vahatalo@helsinki.fi