[APD] thiodenitrification

["Steve Pushak" <teban at powersonic_bc.ca>]

I found another stoichiometric formula for denitrification. This one works
without carbon!

3H2S + 4NO3- + 6OH- = 3SO42- + 2N2 + 6H2O

Is there a way a sulfur compound can oxidize ammonia? such as:

2NH4+ + 3SO2 = 2NO3 + 2H+ + H2S

Is this a reasonable reaction? I think H2S would instead be quite reactive
with nitrate.

Perhaps its more reasonable using SO4(2-), the sulphate ion. Nitrate
disappears at redox of +0.35V to +0.1V and sulphate should predominate above
+0.1V. I think ammonia should be quite stable in the absence of free oxygen.
Urea would hydrolyze to ammonia wouldn't it?

I found the following on the subject of ammonia nitrification at
<http://cobamide2.bio.pitt.edu/biosc1865%5CLecture18.pdf>:

"In virtually all cases, the two stages of nitrification are performed by
separate organisms
? Species the carry out ammonia oxidation to nitrite include the following:
a) Nitrosomonas europeae (most studied)
b) Nitrosolobus spp. (most widespread)
c) Nitrosovibrio & Nitrosospira (least common)
d) Nitrosococcus (important in marine environments)
? Species that carry out nitrite oxidation to nitrate include the following:
e) Nitrobacter (best studied)
f) Nitrospira, Nitrococcus, Nitrospina (high-salt marine nitrifiers)"

I found the following stoichiometric equations at
<http://fadr.msu.ru/mmc/anmod/HIC_214.html>

(CH2O)106(NH3)16H3PO4 + 53SO42- =
= 106CO2 + 106H2O + 16NH3 + H3PO4 + 53S2-
(Richards 1965);

1/2CH2O + NO3 =­ NO2- + 1/2H2O + 1/2CO2
(Anderson et al. 1982)

3/4CH2O + H+ + NO2- = 1/2N2 + 5/4H2O + 3/4CO2
(Anderson et al. 1982)
where Corg:Norg =106:16 (Richards 1965);

(CH2O)106(NH3)16H3PO4 + 84.8HNO3 =
= 106CO2 + 42.4N2 + 148.4H2O + 16NH3 + H3PO4
(Nealson et al. 1991);

3H2S + 4NO3- + 6OH- = 3SO42- + 2N2 + 6H2O
(Volkov 1984);

2H2S + O2 = 2S0 + 2H2O (Tebo 1991);

2S0 + O2 + H2O = S2O32- + 2H+
(Kondrat'eva 1983);

S2O32- + 2O2 + 2OH- = 2SO42- + H2O
(Jorgensen 1989);

NH4+ + 3/2O2 = NO2- + 2H+ + H2O (Jorgensen 1989);

NO2- + 1/2O2 = NO3- (Jorgensen 1989);

(CH2O)106(NH3)16H3PO4 + 106O2
 = 106CO2 + 16NH3 + H3PO4 + 106H2O
(Nealson et al. 1991).

MnO2 + H2S + 2CO2 = Mn2+ + S0 +2HCO3
(Volkov 1984)

Mn2+ + O2+2H2O = MnO2 +4H+ (Rozanov 1995)


Steve P

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