Isotopic composition of carbon in atmospheric air; use of a diffusion model at the water/atmosphere interface in Velenje Basin

Abstract

Klju~ne besede: atmosferski ogljikov dioksid, ogljikovi izotopi, fazna meja zrak/voda, difuzijski model, Velenjski bazen, termoelektrarna, antropogeni vpliv Abstract CO 2 concentrations (partial pressure of CO 2 , pCO 2 ), and isotope compositions of carbon dioxide in air (δ 13 C CO2 ), temperature (T) and relative humidity (H) have been measured in the atmosphere in the Velenje Basin. Samples were collected monthly in the calendar year 2011 from 9 locations in the area where the largest thermal power plant in Slovenia with the greatest emission of CO 2 to the atmosphere (around 4M t/year) is located. Values of pCO 2 ranged from 239 to 460 ppm with an average value of 294 ppm, which is below the average atmospheric CO 2 pressure (360 ppm). δ 13 C CO2 ranged from -18.0 to -6.4 ‰, with an average value of -11.7 ‰. These values are similar to those measured in Wroclaw, Poland. We performed the comparison of δ 13 C CO2 values in atmospheric air with Wroclaw since researchers used similar approach to trace δ 13 C CO2 around anthropogenic sources. The isotopic composition of dissolved inorganic carbon (δ 13 C DIC ) in rivers and lakes from the Velenje basin changes seasonally from -13.5 to -7.1‰. The values of δ 13 C DIC indicate the occurrence of biogeochemical processes in the surface waters, with dissolution of carbonates and degradation of organic matter being the most important. A concentration and diffusion model was used to calculate the time of equilibration between dissolved inorganic carbon in natural sources (rivers) and atmospheric CO 2 . Izvle~ekTa {tudija opisuje rezultate analize koncentracij CO 2 v zraku (parcialni tlak CO 2 , pCO 2 ) in izotopske sestave ogljika v atmosferskem zraku (δ 13 C CO2 ), temperature (T) in relativne vlažnosti (H) v atmosferi iz Velenjskega bazena. Vzorce smo vzor~ili mese~no na 9 lokacijah v koledarskem letu 2011 na obmo~ju Velenjskega bazena, kjer je locirana najve~ja termoelektrarna v Sloveniji, ki predstavlja najve~jega proizvajalca emisij CO 2 v atmosfero (okoli 4 Mt/leto). Koncentracije pCO 2 v zraku se v ~asu te {tudije spreminjajo od 239 do 460 ppm. Merjene povpre~ne koncentracije pCO 2 v na{i {tudiji zna{ajo 294 ppm in so pod povpre~nim atmosferskim tlakom CO 2 , ki zna{a 360 ppm. Merjena δ 13 C CO2 se spreminja od -18,0 do -6,4 ‰ s povpre~no vrednostjo δ 13 C CO2 -11,7 ‰. Vrednosti atmosferskega CO 2 in δ 13 C CO2 so v ~asu te raziskave podobne vrednostim objavljenim za Wroclaw, Poljska. Naredili smo primerjavo z δ 13 C CO2 vrednostmi v atmosferskem zraku z Wroclawom, ker so raziskovalci uporabili podoben pristop sledenja δ 13 C CO2 vrednosti okrog antropogenih virov. Izotopska sestava raztopljenega anorganskega ogljika (δ 13 C DIC ) v rekah in jezerih Velenjskega bazena se je v letu 2011 sezonsko spreminjala od -13,5 do -7,1 ‰. Vrednosti δ 13 C DIC odražajo biogeokemijske procese v povr{inskih vodah, med katerimi sta najpomembnej{a raztapljanje karbonatov in razgradnja organske snovi. Izdelali smo tudi koncentracijski in izotopski difuzijski model za izra~un ~asa u...