Graduate students of Vähätalo Miika Kuivakko, started 2005, University of Helsinki, Photochemical decomposition of brominated flame retardants in the environment. Susann Haase, started 2008, University of Helsinki, The role and importance of photochemistry and bacterial processes in sea ice. Hanna Aarnos, started 2006, University of Helsinki, Photolytic decomposition of natural organic matter in environment.
30
Embed
Graduate students of Vähätalo - helsinki.fi · Graduate students of Vähätalo Miika Kuivakko, started 2005, University of Helsinki, Photochemical decomposition of ... [email protected]
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
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…
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.
• 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)
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)