Physico-chemical properties of environmental compartments

Soil/sedimenary organic matter

• Aims:

– To provide knowledge about main components of environmental compartments (soil/sediments)

• Outcomes:

– Students will understand the main properties of components of environmental compartments (soil/sediments)

2Environmental processes / Pollutants and environmental compartments (i)

Environmental processes / Pollutants and environmental compartments (i) 3

W et (rain , snow )D eposition

G as

P artic les/aerosols

D epos ition to te rrestria l su rfaces

D ry pa rtic leD epos ition

A ir/w a te r/snow G as exchange

D irec t depos ition to w a te r/snow

S now m e lt& runo ff

D isso lved phase

P artic le bound

P artic le sedim en ta tion

S ed im en t bu ria l

P hytop lankton -inve rteb ra tes-fo rage fish

Aquatic food w ebs

M arine m am m alsP iscivorous fish

W ate rfow l,sea b irds

Terrestrial food webs

L ichen - ca ribou

P lan ts - ca ttle (m ilk, m ea t)

Stra tosphere - ozone layer dep letion

Troposphere - increased U V solar rad iation

CFC , CO 2 , CH 4 G loba l warm ing

Relatively long atm osphere life tim esCO 2 , CFC , CH 4 , P O Ps, m ercury, C l 4 ,C l5 P CDD /FsS PM 2.5

Relatively short atm ospheric life tim esS O x, NO x, CO , VO C s, HC FCs, h igh M W P CD D/Fs, S PM 10, heavy m eta ls

V O Cs, N O xO zone

reac tions w ithH O rad ica l

S O 2 , NO xA cid ic p rec ip ita tion

H 2O

Anthropogenic Sources

N atu ra l S ources

H um ans

H um ans

123

A quatic -Terres tria l-A tmospheric E c osys tem L inkages to Chemic al Cyc les

S .J . E isenreic h (M odified from D. M uir, 1997)

Soil/Sediment Organic Matter (SOM)

• Content:– ~0 to 5% of most soils– Up to 100% of organic soils (histosoils)– Higher in moist soils and northern slopes– Lower in drier soils and southern slopes– Cultivation reduce SOM

• High surface area and CEC• High content of C and N

4Environmental processes / Pollutants and environmental compartments (i)

5Environmental processes / Pollutants and environmental compartments (i)

6Environmental processes / Pollutants and environmental compartments (i)

7Environmental processes / Pollutants and environmental compartments (i)

8

Fig 3.3

Four theories on how humic substances are formed

Pathway 1: probably not important

Pathways 2 & 3: polymerization of quinones, probably predominant in forest soils

Pathways 4: Classical theory, probably predominant in poorly drained soils

Environmental processes / Pollutants and environmental compartments (i)

9

Negative charge comes primarily from ionization of acid functional groups (e.g. hydroxyl, carboxyl)

Environmental processes / Pollutants and environmental compartments (i)

10

SOM structures

soil humic acid

seawater humic

black carbon (soot, HSACM)

Environmental processes / Pollutants and environmental compartments (i)

SOM properties

• Voids can trap

– Water

– Minerals

– Other organic molecules

• Hydrophobicity/hydrophilicity

• Reactivity

• H-bonding, chelating of metals

11Environmental processes / Pollutants and environmental compartments (i)

• Functional groups and charge characteristics– PZC ~ 3 (pH of zero charge)– Up to 80% of CEC in soils is due to SOM– Acid functional groups

• Carbonyls pKa < 5• Quinones also pKa < 5• Phenols pKa < 8

– SOM constitutes most of the buffering capacity of soils

12Environmental processes / Pollutants and environmental compartments (i)

13Environmental processes / Pollutants and environmental compartments (i)

Source

Environmental processes / Pollutants and environmental compartments (i) 14

In The Handbook of Environmental Chemistry: Aboul-Kassim, T.A.T., Simoneit, B.R.T., 2001. Chemistry and Modeling. Springer-Verlag, Berlin. P107-167. ISBN: 3-540-41650-1