“MUC” and Humics

1. “MUC”and Humics “Molecularly uncharacterized component”

2. “Geomolecules”Or “GEO-MACRO-MOLECULES (GMM’s) 1. What are they?

3. “Geomolecules” “An organic molecule that does not exist (or originate) in a biological system”

4. “Geomolecules” “A molecule that does not exist (or originate) in a biological system” • Assumed to have originated due to abioticorganic reactions in the geosphere. • Some assumed properties: • Made up from biological-derived components. • Characterized by: • a) “randomness”- (relative to enzyme-derived structures) ie: structure controlled by organic chemistry, thermodynamics, not evolution/bio function.

5. “Geomolecules” “A molecule that does not exist (or originate) in a biological system” Due to previous, defined classically by: A) Size (large MW), and B) Inscrutability (is that word?) ie: chemically unrecognizable structure 2. Due to (b) families are Operationally defined: often by characteristic solubility behavior or as the “leftovers” of a set of Molec-level techniques.

6. Structures? So, you might ask- if this is the case, where did these pictures come from? 

7. Answer: “cartoons” such as one at right come from from bulk and functional-level techniques • CHN data (elemental ratios constrain possible structures) • Spectroscopic data (in particular 13C NMR) • Acid –Base data- you can “titrate” acid groups. •  Thus, even though there is no “real” structure for GMM’s, pictures like the one at the right have seeped into the collective consciousness..

8. Some Main MUC Classes • A) Kerogen • “The fraction of large chemical aggregates in sedimentary organic matter that is insoluble in solvents “ >90% of OM in rocks • Divided into 3 broad “Types”, based on bulk properties, and assumed sources: • Type-I “algal kerogen” - freshwater algal source • Type-II “liptinitic kerogen” – marine plankton • Type-III “humic kerogen” higher terrestrial plants (eg in coals) • .

9. Recall the Van Krevelyn type diagrams

10. Kerogen= stuff you cannot extract Source Rock “Bitumen” =stuff you can extract 13C solid-state NMR spectra after HF demineralization

11. 2. Humics and Fulvics • “Humin”: the general term for MUC of soils/ rivers • A) Humics and Fulvic acids: Fractions of Humin- defined by variable solubility (and associated/ assumed size) • *Humic Acid: Soluble in weak base; insoluble in acid- assumed Larger MW • *Fulvic acid: Soluble in all conditions ( yellow-substance)- thought to be smaller MW.

12. 2. Humics and Fulvics

13. Fulvics: because are smaller and soluble, can more readily solve actual structures One “model structure” structure- based on collected average data

14. Fulvics: Some real structures- from swanneee river fulvic- shown to come from tannin and terpinoid precursors

15. Humics: NMR Spectra: note- far more complex than kerogen- lots of aromatic- but also lots of acid, comlex aliphatic, and oxygenated (or N) containing moities

16. Humics: One“model” structure- based on collected average data

17. So: Where does complex MUC come from? • So: Here is the Classical Creation Story- • Which has supported a whole series of assumptions • Underlying Observations: • Most organic matter is MUC : in soils, sediments and water are >50% uncharacterized. • 2. Recognizable structures occur: Lipid structures occur in rocks and petroleums that are recognizably biochemical in origin

18. So: Where does complex MUC come from? Classical Creation Story Con’d Which has supported a whole series of assumptions 3. Progression of complexity: With depth in sediment cores relative abundances change in the order: (decreases) biochemicals fulvic acidhumic acidkerogen (accumulates) note: molecular weight increases to the right 4. Known condensation reactions -many reaction paths are well known that can cause condensations.

19. Example: the Maillard Reaction The classic example: “browning reactions” * Ever leave a pan on the stove? many possible products • 1912: Louis Camille Maillard, describes Rx between proteins and carbos • In foods, Maillard Rx is well studied- responsible for changes in color, flavor, nutrition. • Question: Why not in the geosphere?

20. “Chaque fois que je cuisine avec ma poêle, mon four ou que j'utilise mon barbecue, je provoque une réaction de Maillard “ Sapides: sapid = full of flavor

21. Example: the Maillard Reaction “melanoidans”= the product of maillard Rx: insoluble brown pigmented products, which have variable structures, molecular weights and nitrogen content. Among many many final Products: Pentoses may further react with amines to give orange dye products, influencing the colour of the food.

22. The Classical Heteropolycondensate Model:Based largely on assumption that prevous kinds of reactions occur off the stove, in the environment: • 1. Biopolymers (e.g. lignins, polysaccharides and proteins) are broken down microbially into reactive monomers (e.g. phenols, sugars and amino acids), a fraction (<1%) of which spontaneously “condense” to form heterogeneous GMMs (rest to CO2). • ( minor OC loss in polymerization steps) • 2. Condensation is progressive: • BPBMFAHAkerogen/humin • Some lipids are incorporated into kerogens/humin with minor changes in structure. • 4. Major Appeal: • a. explains failure at characterizations.

23. Problems with the theory in “modern cycles” • little supporting evidence for fast condensation reactions or their “scrambled” products • 1. Few “new” compounds in degraded vs. original woods, leaves & plankton (ie, data support selective removal, not creation of new compounds)

24. Problems with the theory in “modern cycles” • condensation would have to outcompete microbial degradation ! And yet depends on competitive biodegradation as a source of reactive metabolic intermediates • (suggests that bacterial metabolic efficiency must be very low, or near zero, to allow almost significant conversion of biopolymers to geopolymers deep in sediments (%OC profiles almost constant •  Accumulating evidence suggests that much “uncharacterized” OM is actually biochemical-

25. II: Why are they important? Geomolecules

26. Why are GMMs important? • 1. Back to the carbon cycle: • Kerogen is the major organic component of sedimentary rocks (~20% of all buried C- organic or inorganic). • * Unidentified OM is the major organic component of MOST large reservoirs

27. BUT: In a typical deep-sea sediment only about 20% of TOC can be characterized molecularly: The other 80% of TOC is either: 1) macromolecules that are not readily broken down into molecules < 1000D 2) macromolecules that hydrolyze to unrecognizable molecules <1000D 3) Burnt biomass (Black Carbon) in the forms of char, charcoal, soot ("invisible").

28. Why are GMMs important? • Humic substances are major organic forms in soil, sediment and natural waters, where they: • *affect soil structure and fertility • * form complexes with dissolved metals and attenuate light transmission in natural waters • * absorb nonpolar anthropogenic compounds such as PCB's, pesticides & PAHs • * And: constitute huge reservoirs of biologically active elements on land and in the ocean.

29. Humics Nature's Humic Acid100% Organic “Liquid humic acid is a cost-effective way to add humus to your soil. Humic acid increases the efficiency of your fertilizers, transforms insoluble nutrients into useable ones, retards pathogenic fungi build-up, and stimulates microbial activity. “

30. Fulvics: and of course, comes in “organic” form.. Can buy “fulvic acid” by the pint, quart or gallon for your hydroponic garden- to promote “uptake” of nutrients..

31. Why are GMMs important? • Key player in understanding cycling and fates of many nutrients and pollutants: • Metals: Humics form complexes with dissolved metals and thus effect both bioavailablity of bio-important metals (eg iron) as well as transport of contaminants. • Hydrophobic molecules: Adsorb (partition) hydrophobic contaminants ( eg PCB, PAH, hydrocarbons) thus effect both bioavailablity of bio-important metals (eg iron) as well as transport of contaminants.

32. Example: Degree of Organic Speciation in metals • Strongly hydrolyzable species (with low solubility) would be expected to have a higher % organic speciation • EG estimates of % organic-bound: • Cd: 20-80% • Cu: 80-99.99% • Fe: >99.9% • Pb: 36-98%

33. Why do they bind? • 1. Carboxylic acids Groups All soluble GMM’s (ie humics) are by definition loaded with carboxylic acid groups. Or they wouldn’t be soluble.. • 3) Electron density in Carboxylic acids are “perfect” to bind certain classes of metals really well • (recall “Hard, medium and soft metals and ligands” from inorganic chem class- basically a shorthand expression of density of electrons in outer shell) • Ba2+<Sr2+<Ca2+<Mg2+<Mn2+<Fe2+<Co2+<Ni2+<Cu2+>Zn2 • estimates of % organic-bound to COOH, based on “softness”

34. Model organic ligands Question: are there certain natural-product ligands made to bind up Fe? Probably Yes: Eg: Model Organic Ligands Witter et al. 2000 Marine Chemistry * COOH groups = key function for binding metals.

35. Note Similarity:

36. Non-Polar Organics: Humics act as “carriers”- important in transport and partitioning. • Why? • “like dissolves like” chem 101. Typically simple question of equilibrium partitioning (ie similar polarity) • ( THUS humics, in theory , are sort of like giant natural detergents..)

37. Why are GMMs important- III? “BLACK CARBON” • “ Black-Carbon” ~ soot • = are hypothesized “new” form of carbon soil, sediment and natural waters. • - Operationally defined- thought to be produced by biomass burning- naturally as well as anthropogenically- and possibly also in deep ocean sediments (heated..)

38. “BLACK CARBON”

39. “BLACK CARBON” Thought to be highly condensed aromatic rings- almost “invisible” to solids state CPMAS NMR- and because large and insoluble- also to other techniques!

40. “BLACK CARBON” Formation monitored via NMR Thermal degradation (“Charring”)- no oxygen- experiment on wood 500C, under N2

41. Importance of Black Carbon • 1) Contaminant cycling: expected to adsorb (partition) aliphatic hydrocarbons even better than humics (eg: PAH’s) ( think of charcoal resins in water filters) • “Invisible” part of C –Cycle? May be important, but not recognized part of carbon cycle. • IF important and unaccounted for.. Screws up many your analyses..

42. III: How do you analyze for them? Geomolecules

43. In sum: large fraction of OM in sediments, soils, and DOM is “MUC”. What to do? • 1. Develop new methods to characterize MUC: for example, find reactions (in addition to hydrolysis) to break down MUC and identify the pieces (eg, maldi-toffs, etc). • 2. Physically isolate MUC by selectively removing the mineral matrix (eg: "demineralization with HF + NMR, or ultrafiltration- various other schemes."). • Or of course: • 3. Just cop out! (the historic method of choice). By: • defining MUC as being structurally inscrutable, • giving various MUC solubility classes some “icky” names and • making up some creation stories to explain their existence

44. The issue of Molecular Techniques for Geomolecules: How do you analyze this?

45. Problems: 1 The Size issue • The Contemporary Analytical window has a "blind spot" between ~104 and 107 daltons (amu) • At one end: Microscopic analyses can be misleading or useless below about 1uM for organics (eg, mostly formless “stuff”). • 2. At the other: Most molecular-level analyses (as we saw previously) depend on separation of some kind- eg, HPLC/GC. This puts limitations on molecular size, based on volatility or solublity.

46. The Size spectrum: (daltons)

47. Bulk Character all we are left with? • 3. Bulk characterizations are (in principle) applicable over a huge size range (methane to mastodons), but are not very informative about details of molecular structure. •  AND (as we have seen) stories based on bulk ratios (and even functional ratios) can be very misleading.

48. Can we break them apart in non-hydrolytic ways? Sort of. The dilemma: Condensed and complex structures, very difficult to break apart “cleanly”. a) Harsh chemical conditions often needed- destroys original structures. b) Structures present (or created) are largely unknown. result: difficult to know how to design a ML approach.

49. Pyrolysis: Thermal Destructionidea: to blow up molecule, making it amenable to GC, GC-MS, yet preserve the maximum structural information possible. • Mechanism Analogous to MS •  Information from Fragments

50. pyrogram: