ESPM 131 Lecture Notes - Lecture 23: Lithotroph, Ammonium, Eutrophication
14 May 2018
School
Course
Professor
Lecture 23: Denitrification - Reduction of Nitrogen
●Fates of NO3-:
○Leaching :
■NO3 is anionic → won’t absorb in cation exchange sites
■Easily transported out of soil to subsoil/water
■Can induce eutrophication
○Chemo-denitrification : [3NO2 + H+ → 2NO + NO3 + H2O]
■Reduction of NO2 to NO
■At low pH
○Biological NO3 reduction - assimilation/denitrification
■Assimilation :
●[NO3 → NH4]
●By plants and microbes (heterotrophs)
●No E conservation
●Regulated by [NH4] ← low conc
●Both aerobic and anaerobic (facultative) microbes
■Denitrification :
●[NO3 → NO2 → NO → N2O → N2]
●Replacement of O2 as terminal e- acceptor
●Wide range of genera, usually hetero, some chemolithotrophic
●Facult anaerobes
●Several fungi can do incomplete denitrif to N2O
●Anaerobic
●O2 availability: nitrate replaces O2 as e- acceptor when conc falls to 0 →
high soil water content favors denitrification, in aggregates
●Requirements:
○Metabolic capacity ( narG/nerK, norB,C, nosZ enzymes )
○Available C
○Anaerobic conditions (at least locally)
■DNRA : dissimilatory nitrate reduction to ammonia
●Not assimilation
●Some E conservation
●Diferent microbes
●Strictly anaerobic, controlled by pe (low redox potential)
●Environmental significance:
○Waste-water treatment
○Source of GHG (N2O) w/ incomplete denitrification
●Measuring denitrification:
○Potential activity: C2H2 inhibition method , optimal conditions
○Mass balance approach : on landscape level, outputs/inputs (diferences = denit)
Document Summary
No(cid:1682) is anioni(cid:283) (cid:476)on"t a(cid:282)so(cid:418)(cid:282) in (cid:283)ation e(cid:481)(cid:283)han(cid:322)e sites. Easil(cid:482) t(cid:418)anspo(cid:418)ted out o(cid:321) soil to su(cid:282)soil/(cid:476)ate(cid:418) Chemo-denitri (cid:283)ation : [(cid:1682)no(cid:1681) + h+ (cid:1681)no + no(cid:1682) + h(cid:1681)o] [no(cid:1682) no(cid:1681) no n(cid:1681)o n(cid:1681)] Wide (cid:418)an(cid:322)e o(cid:321) (cid:322)ene(cid:418)a, usuall(cid:482) hete(cid:418)o, some (cid:283)hemolithot(cid:418)ophi(cid:283) Se(cid:475)e(cid:418)al (cid:321)un(cid:322)i (cid:283)an do in(cid:283)omplete denit(cid:418)i(cid:321) to n(cid:1681)o. O(cid:1681) a(cid:475)aila(cid:282)ilit(cid:482): nit(cid:418)ate (cid:418)epla(cid:283)es o(cid:1681) as e- a(cid:283)(cid:283)epto(cid:418) (cid:476)hen (cid:283)on(cid:283) (cid:321)alls to 0 hi(cid:322)h soil (cid:476)ate(cid:418) (cid:283)ontent (cid:321)a(cid:475)o(cid:418)s denit(cid:418)i (cid:283)ation, in a(cid:322)(cid:322)(cid:418)e(cid:322)ates. Meta(cid:282)oli(cid:283) (cid:283)apa(cid:283)it(cid:482) (cid:1827) narg/nerk, norb,c, nosz enzymes (cid:1828) Dnra : dissimilato(cid:418)(cid:482) nit(cid:418)ate (cid:418)edu(cid:283)tion to ammonia. Sou(cid:418)(cid:283)e o(cid:321) ghg (cid:1827)n(cid:1681)o(cid:1828) (cid:476)/ in(cid:283)omplete denit(cid:418)i (cid:283)ation. Potential a(cid:283)ti(cid:475)it(cid:482): c(cid:1681)h(cid:1681) inhi(cid:282)ition method , optimal (cid:283)onditions.
