Small molecules dominate organic phosphorus in NaOH-EDTA extracts of soils as determined by 31P NMR

Haddad, LennyUmeå universitet,Institutionen för medicinsk kemi och biofysik (author)

Understanding the composition of organic phosphorus (P) in soils is relevant to various disciplines, from agricultural sciences to ecology. Despite past efforts, the precise nature of soil organic P remains an enigma, especially that of the orthophosphate monoesters, which dominate 31P NMR spectra of NaOH-EDTA extracts of soils worldwide. The monoester region often exhibits an unidentified, broad background believed to represent high molecular weight (MW) P. We investigated this monoester background using 1D 31P NMR and 2D 1H[sbnd]31P NMR, as well as 31P transverse relaxation (T2) measurements to calculate its intrinsic linewidth and relate it to MW. Analyzing seven soils from different ecosystems, we observed linewidths of 0.5 to 3 Hz for resolved monoester signals and the background, indicating that it consists of many, possibly >100, sharp signals associated with small (<1.5 kDa) organic P molecules. This result was further supported by 2D 1H[sbnd]31P NMR spectra revealing signals not resolved in the 1D spectra. Our findings align with 31P NMR studies detecting background signals in soil-free samples and modern evidence that alkali-soluble soil organic matter consists of self-assemblies of small organic compounds mimicking large molecules.

NATURVETENSKAP Geovetenskap och miljövetenskap Miljövetenskap hsv//swe
NATURAL SCIENCES Earth and Related Environmental Sciences Environmental Sciences hsv//eng
2D 1H– 31P NMR
31P NMR
Molecular weight
Monoester region
P speciation
Phosphorus
Sulfide precipitation
T2 measurements

Vincent, Andrea G.Escuela de Biología, Universidad de Costa Rica, San José, Costa Rica (author)
Giesler, ReinerUmeå universitet,Institutionen för ekologi, miljö och geovetenskap(Swepub:umu)regi0001 (author)
Schleucher, Jürgen,ProfessorUmeå universitet,Institutionen för medicinsk kemi och biofysik(Swepub:umu)jusc0001 (author)
Umeå universitetInstitutionen för medicinsk kemi och biofysik (creator_code:org_t)

By the author/editor: Haddad, Lenny; Vincent, Andrea ...; Giesler, Reiner; Schleucher, Jürg ...

About the subject

NATURAL SCIENCES: NATURAL SCIENCES; and Earth and Relate ...; and Environmental Sc ...

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