Lecture #18Dissolved Carbon Dioxide: Introduction

(Stumm & Morgan, Chapt.4 )

Benjamin; Chapter 5.4 & 7

David Reckhow CEE 680 #18 1

Updated: 23 February 2020 Print version

http://www.ecs.umass.edu/cee/reckhow/courses/680/slides/680l18p.pdf

David Reckhow CEE 680 #18 2

COOH

O

COOH

COOH

COOH

HOOC

HOOC

HO

OH

COOH

H3CO

OHHydroxy Acid

AromaticDicarboxylicAcid

AromaticAcid

Aliphatic Acid

AliphaticDicarboxylicAcid

Phenolic-OH

HO

From Thurman, 1985

An Aquatic Humic “Structure”

Titration of Humics Model for

aquatic humic substances Acetic acid +

phenol

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Acid Neutralizing Capacity

Net deficiency of protons with respect to a proton reference level when the reference level is H2CO3, the

ANC=Alkalinity

conservative, not affected by T or P In a monoprotic system: [ANC] = [A-] + [OH-] - [H+] = CTα1 + [OH-] - [H+]

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[ ] ∫=

=

=xf

nf

dpHANC β

Dissolved Carbon Dioxide Importance regulating pH in natural waters, also source

of carbon for autotrophic organisms Sources volcanism, combustion, respiration,

weathering

Sinks photosynthesis, precipitation

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CaCO3 (s) + CO2 + H2O ←→ Ca+2 + 2HCO3-Base Acid Hardness Alkalinity

Major Forms of Carbon on Earth

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Source Mass,1015 Kg

Percent

Geologic inorganicminerals

60,000 83%

Geologic organicmineralsa

12,000 17%

Oceanic inorganics 40 0.056

Atmosphere 0.7 0.00097

All life on earth 0.6 0.00083

Ray, Table 3.3, pg. 37

PRIVATE

PRIVATE Source

Mass,

1015 Kg

Percent

Geologic inorganic minerals

60,000

83%

Geologic organic mineralsa

12,000

17%

Oceanic inorganics

40

0.056

Atmosphere

0.7

0.00097

All life on earth

0.6

0.00083

Carbon Forms: Definitions

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CO2 = carbon dioxide (dissolved and gas)H2CO3 = carbonic acid (dissolved)HCO3- = bicarbonate (dissolved)CO3-2 = carbonate (dissolved)CaCO3 = calcium carbonate (mineral)

Inorganic Carbon

Organic CarbonC6H12O6 = glucose (a sugar)CH3COOH = acetic acid (a carboxylic acid)

The Carbon Cycle

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AtmosphericCO2

AqueousCarbonates

PlantOrganic-C

Animal Organic-C

Geologiccarbonates

Fossil fuelOrganic-C

Combustion

Dissolution

Precipitation

Consumption

After: Ray, Figure 3.9

Global Carbon Dioxide

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Atm

osph

eric

car

bon

diox

ide,

ppm

.

https://www.esrl.noaa.gov/gmd/ccgg/trends/

https://www.esrl.noaa.gov/gmd/ccgg/trends/

TOC Trends in US Rivers

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Reckhow, Rees & Nusslein, 2006

Lake Erie

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Total Organic Carbon levels from 2004 to 2011 in the Western Basin of Lake Erie (Baldwin Raw) and in treated water (Baldwin FE)

Tri-state Region

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The Northeast Climate Change Report has projected increases in temperature of 8-12ºF in winter and 6-14°F in summer based on the higher emissions scenario. In general a great annual rainfall is expected, with more high flow events in winter and spring, higher intensity storms and longer annual droughts in summer. This is projected to cause a loss of spruce, fir, hemlock, maple beech and birch, and a migration to a oak/hickory forest. There may be more complete export of agriculturally-applied nutrients. The loss of hemlocks could speed up decomposition and nutrient cycling in soils, increasing nitrate runoff into streams.

To next lecture

David Reckhow CEE 680 #18 13

http://www.ecs.umass.edu/cee/reckhow/courses/680/slides/680l19.pdf

CEE 680: Water ChemistryAn Aquatic Humic “Structure”Titration of HumicsAcid Neutralizing CapacityDissolved Carbon DioxideMajor Forms of Carbon on EarthCarbon Forms: DefinitionsThe Carbon CycleGlobal Carbon DioxideTOC Trends in US RiversLake ErieTri-state RegionSlide Number 13