An Aquatic Humic Structure Hydroxy Acid OH COOH From Thurman, - - PDF document

CEE 680 Lecture #18 2/24/2020 1

Lecture #18 Dissolved Carbon Dioxide: Introduction

(Stumm & Morgan, Chapt.4 )

Benjamin; Chapter 5.4 & 7

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Updated: 24 February 2020

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COOH O COOH COOH COOH HOOC HOOC HO OH COOH H3CO OH Hydroxy Acid Aromatic Dicarboxylic Acid Aromatic Acid Aliphatic Acid Aliphatic Dicarboxylic Acid Phenolic-OH HO

From Thurman, 1985

An Aquatic Humic “Structure”

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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+] 

= CT1 + [OH‐] ‐ [H+]

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 



 



x f n f

dpH ANC 

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Dissolved Carbon Dioxide

 Importance

 regulating pH in natural waters, also source

• f 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, 10

15 Kg

Percent Geologic inorganic minerals 60,000 83% Geologic organic minerals

a

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

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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 Carbon

C6H12O6 = glucose (a sugar) CH3COOH = acetic acid (a carboxylic acid)

The Carbon Cycle

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Atmospheric CO2 Aqueous Carbonates Plant Organic-C Animal Organic-C Geologic carbonates Fossil fuel Organic-C Combustion Dissolution Precipitation Consumption After: Ray, Figure 3.9

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Global Carbon Dioxide

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Atmospheric carbon dioxide, ppm.

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

TOC Trends in US Rivers

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Reckhow, Rees & Nusslein, 2006

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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

• f hemlocks could speed up

decomposition and nutrient cycling in soils, increasing nitrate runoff into streams.

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To next lecture

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