Biogenic activity

Homochirality A preferential amplification of one enantiomer over the other due to biogenic activity - a biomarker... 

McKay DS, et al. (1996) Search for past life on Mars possible relic biogenic activity in martian meteorite ALH 84001. Science 273 924-930... 

Northern Hemisphere. The natural sources include volcanoes, plants, soil and biogenic activity in the oceans. In terms of photochemistry the major sulfur oxide, sulfur dioxide (SO2) does not photodissociate in the troposphere (cf. NO2), i.e. 

In conclusion, any metal oxalate can be considered as a compound in a metastable equilibrium. The only sub-spontaneous diagenetic evolution of calcium oxalate is a possible transformation of weddellite into whewellite by dehydration (Frey-Wyssling, 1981 Verrecchia et al., 1993). Consequently, activation energy has to be provided for a complete oxidation of COM or COD, and life is the best and the most obvious candidate. Therefore, biogenic activity could be the key explanation for the absence of oxalate in paleosols as well as in the geological sedimentary record. 

McKay D. S., Gibson E. K., Thomas-Keprta K. L., Vali H., Romanek C. S., Clement S. J., ChiUierX. D. E., Maechling C. R., and Zare R. N. (1996) Search for past hfe on Mars possible relic biogenic activity in martian meteorite ALH84001. Science 273, 924-930. 

Figure 9.2 Sketch showing the relationships between oxygen, temperature and biogenic activity in a meromictic lake, at noon in summer (Loclat Lake, Switzerland data from Aragno, 1981, and personal communication). The mixolimnion constitutes the oxic zone. The mixolimnion includes the metalimnion and the epilimnion, both defined by the temperature curve. The anoxic zone is called the monimolimnion.

Sketch of the relationships between oxygen, temperature and biogenic activity in a meromictic lake, at noon in summer. 

Biogenic activity. In sandy soils, rapid microbial decomposition of organic matter is facilitated up to its mineralization. In clay soils, anaerobic processes are prevalent with humic substances occurring as decomposition products, and under extremely anaerobic conditions, insufficiently decomposed organic matter may be accumulated. 

The majority of the works are focused in the determination of organic compoimds with biogenic activity [20,23,65-70,72,73] or organic contaminants [56,71]. There is only one method that determines a metal, specifically Zn(II) in milk [23]. 

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