ENVIRONMENTAL MEASUREMENT - WordPress.com · 2013. 8. 4. · Concentration in Environment • Concentration is the driving force that controls the movement of chemicals within and

ENVIRONMENTAL

MEASUREMENT

1 Engr. Yvonne Ligaya F. Musico

Concentration in Environment

• Chemical concentration is one of the

most important determinants in almost all

aspects of chemical fate, transport, and

treatment in both natural and engineered

system.


Concentration in Environment

• Concentration is the driving force that controls

the movement of chemicals within and between

environmental media, as well as the rate of may

chemical reaction.

• Concentration often determines the severity of

adverse effects, such as toxicity,

bioconcentration, and climate change.


1. Mass Concentration Units

• Concentration often

determines the

severity of adverse

effects, such as

toxicity,

bioconcentration, and

climate change.


Mass concentration units


Mass/Mass Units

Parts per million by

mass (referred to as

ppm or ppmm) is

defined as the number

of units of mass of

chemical per million

units of total mass.

totalgiofgppmm610

610xm

mppm

total

im


Mass/Mass Units

Parts per billion by

mass (ppb or ppbm) 910x

m

mppb

total

im

Parts per trillion by

mass (ppt or pptm) 1210x

m

mppt

total

im


Sample Problem 1

Concentration in Soil

A 1 kg sample of soil is analyzed for the

chemical solvent trichloroethylene (TCE).

The analysis indicates that the sample

contains 5.0 mg of TCE. What is the TCE

concentration in ppmm and ppbm?


Solution

Note that in soil and sediments,

mg/kg equals ppmm, and g/kg

equals ppbm

𝑇𝐶𝐸 = 5.0 𝑚𝑔 𝑇𝐶𝐸

1.0 𝑘𝑔 𝑠𝑜𝑖𝑙=

0.005 𝑔 𝑇𝐶𝐸

103𝑔 𝑠𝑜𝑖𝑙

= 5 𝑥 10−6𝑔 𝑇𝐶𝐸

𝑔 𝑠𝑜𝑖𝑙 𝑥 106 = 5 𝑝𝑝𝑚𝑚 = 5, 000 𝑝𝑝𝑏𝑚


Mass/Volume Units

mg/m3 and g/m3 – it is

commonly used unit for

concentration of mass

per volume of air in the

atmosphere

mg/L and g/L –

commonly used for

concentration unit for

water.

In most aqueous

system, ppmm is

equivalent to mg/L.


Sample Problem 2

Concentration in Water

One liter of water is analyzed and found to

contain 5.0 mg of TCE. What is the TCE

concentration in mg/L and ppmm?


Solution


1.0 𝐿 𝐻2𝑂=

5.0 𝑚𝑔

𝐿


1.0 𝐿 𝐻2𝑂𝑥

1.0 𝐿 𝐻2𝑂

1,000 𝑔 𝐻2𝑂

= 5.0 𝑚𝑔 𝑇𝐶𝐸

1.0 𝐿 𝐻2𝑂=

5.0 𝑥 10−6 𝑔 𝑇𝐶𝐸

𝑔 𝑡𝑜𝑡𝑎𝑙𝑥

106𝑝𝑝𝑚𝑚𝑚𝑎𝑠𝑠 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛

𝑇𝐶𝐸 = 5.0 𝑝𝑝𝑚𝑚


Sample Problem 3

Concentration in Air

What is the carbon monoxide (CO)

concentration expressed in g/m3 of 10 L

gas mixture that contains 10-6 mole of CO?


Solution

𝐶𝑂 = 1.0 𝑥10−6 𝑚𝑜𝑙𝑒 𝐶𝑂

10 𝐿 𝑡𝑜𝑡𝑎𝑙𝑥

28 𝑔𝐶𝑂

𝑚𝑜𝑙𝑒 𝐶𝑂

𝐶𝑂 = 28 𝑥 10−6 𝑔 𝐶𝑂

10 𝐿 𝑡𝑜𝑡𝑎𝑙𝑥

106𝜇𝑔

𝑔 𝑥

103𝐿

𝑚3

= 2,800 𝜇𝑔

𝑚3


2. Volume/Volume and Mole/Mole Units

Parts per million by

volume (referred to as

ppm or ppmv) is

defined as the number

of units of volume of

chemical per million

units of total volume.

610xV

Vppm

total

iv



Ideal Gas Law states that the volume occupied by

a given number of molecules of any gas is the

same, no matter what the molecular weight or

composition of the gas, as long as the pressure

and temperature are constant

nRTPV



Universal Gas Constant

• 0.08205 L-atm/mol-K

• 8.205 x 10-5 m3-atm/mole-K

• 82.05 cm3-atm/mole-K

• 1.99 x 10-3 kcal/mole-K

• 8.314 J/mole-K

• 1.987 cal/mole-K

• 62,358 cm3-torr/mole-K

• 62,358 cm3-mm Hg/mole-K

At standard conditions

(P=1 atm and

T=273.15K), 1 mole of

any pure gas will

occupy a volume of

22.4 L.



For gases, volume ratios and mole ratios are equivalent

610xmole

moleppm

total

iv


Sample Problem 4 Gas Concentration in Volume Fraction

A gas mixture contains 0.001 mole of sulfur

dioxide (SO2) AND 0.999 mole of air. What

is the SO2 concentration, expressed in units

of ppmv?


Solution

𝑆𝑂2 = 𝑉𝑆𝑂2

𝑉𝑇𝑜𝑡𝑎𝑙 𝑥106

But,

𝑉𝑆𝑂2 =𝑛𝑅𝑇

𝑃= 0.001 𝑚𝑜𝑙𝑒 𝑆𝑂2

𝑅𝑇

𝑃

And,

𝑉𝑡𝑜𝑡𝑎𝑙 = (0.999 + 0.001) 𝑚𝑜𝑙𝑒 𝑇𝑜𝑡𝑎𝑙𝑅𝑇

𝑃

The concentration in ppmv is:


Solution

𝑝𝑝𝑚𝑣 =0.001 𝑚𝑜𝑙𝑒 𝑆𝑂2

𝑅𝑇𝑃

1.000 𝑚𝑜𝑙𝑒 𝑡𝑜𝑡𝑎𝑙 𝑅𝑇𝑃

𝑥 106

𝑝𝑝𝑚𝑣 =0.001𝐿 𝑆𝑂2

1.000 𝐿 𝑡𝑜𝑡𝑎𝑙 𝑥 106 = 1,000 𝑝𝑝𝑚𝑣



Mole ratio (moles i/moles total) is sometimes

referred to as mole fraction, X.

RT

PxMWxppm

m

gV

000,13


Sample Problem 5 Conversion of Gas Concentration

The concentration of SO2 is measured in air

to be 100 ppbv. What is this concentration in

units of g/m3? Assume the temperature is

28oC and pressure is 1 atm.


3. Partial Pressure Units


3. Partial Pressure Units

])[(

][

totaliv

totaliii

Pxppm

PxfractionmoleorfractionvolumeP

610xP

Pppm

total

iV


Sample Problem 6 Concentration as Partial Pressure

The concentration of gas-phase polychlorinated

biphenyls (PCBs) in the air above Lake Superior

was measured to be 450 picogram per cubic meter

(pg/m3). What is the partial pressure (in atm) of

PCBs? Assume the temperature is 0oC, the

atmospheric pressure is 1 atm and the average

molecular weight of PCBs is 325.


Polychlorinated Biphenyl (PCBs)


Sample Problem 7 Concentration as Partial Pressure

What would be the partial pressure (in atm) of

carbon dioxide (CO2) when barometer reads 29.0

inches of Hg, the relative humidity is 80 percent,

and the temperature is 70oF? Use Table 2.2 to

obtain the concentration of CO2 in dry air. The

vapor pressure of water at 70oF is 0.36 lb/in2.


4. Mole/Volume Units

Molarity (M)

solutionofliter

soluteofmolesMMolarity )(


Sample Problem 8 Concentration as Molarity

The concentration of trichloroethylene (TCE)

is 5 ppm. Convert this units of molarity. The

molecular weight of TCE is 131.5 g/mole.


Sample Problem 9 Concentration as Molarity

The concentration of alachlor, a common

herbicide, in the Mississippi River was found to

range from 0.04 to 0.1 g/L. What is the

concentration range in nanomoles/L? The

molecular formula for the alachlor is C14H20NCl,

and its molecular weight is 270.


4. Mole/Volume Units

soluteofweightequivalent

soluteofweightsoluteofequivalent

solutionofLiter

soluteofequivalentNNormality

)(

Normality (N)


Equivalent Weight

• Weight of substances that are equivalent

to one another in chemical reaction.

• The equivalent of an oxidizing agent or

reducing agent is the weight of the

substance required to gain or lose 1 mole

of electron.


Equivalent Weight

Equivalent Weight = molecular weight (MW)

f (factor)


Reacting Capacity of Solute

ACID BASE SALT

f

Total number

of H+

replaceable

Total number

of replaceable

OH-

Total (+/-)

charge


Sample Problem 10 Calculations of Equivalent Weights

What are the equivalent weights of HCl,

H2SO4, NaOH, CaCO3, and aqueous CO2?


Relationship between Normality

and Molarity

N = n solute x f

liter of solution

N = molarity (M) x f


Sample Problem 11 Calculation of Normality

What is the normality of 1 M of HCl and

H2SO4?


Sample Problem 12 Use of Equivalents in Determining the

Accuracy of a Water Analysis

The label on a bottle of New Zealand mineral water

purchased in the city of Dunedin states that a chemical

analysis of the mineral water resulted in the following

cations and anions being identified with corresponding

concentrations (in mg/L):

[Ca2+] = 2.9 [Mg2+] = 2.0 [Na+] = 11.5 [K+] = 3.3

[SO42-] = 4.7 [F-] = 0.09 [Cl-] = 7.7

Is the analysis correct?


5. Concentration as a Common Constituent

• Greenhouse gases, nitrogen, and phosphorus are

chemicals that have their concentration typically reported

as a common constituent.

• Phosphorus may be present as orthophosphates

(H3PO4, H2PO4-, HPO42-, PO4

3, HPO42- complexes)

polyphosphate (for example, H4P2O7 AND H3P3O102-),

metaphosphates (for example, HP3O92-), and/or organic

phosphates (mg P/L, mg/L as P, or mg/L P)


Sample Problem 13 Nitrogen Concentration as a Common

Constituent

A water contains two nitrogen species. The

concentration of NH3 is 30 mg/L NH3, and

the concentration of NO3- is 5 mg/L NO3

-.

What is the total nitrogen concentration in

units of mg N/L?



• Hardness of water is caused by the presence of divalent

cations in water, which Ca2+ and Mg2+ are by far the

most abundant (mg CaCO3/L).

32

2

/

50CaCOas

L

mg

eqvginMofwteqvL

mginM



• Global warming potential (GWP) is a multiplier used to

compare the emissions of different greenhouse gases to

a common constituent.

• Carbon dioxide equivalent are metric measurement

used to compare the mass emissions of greenhouse

gases to a common constituents, based on the specific

gas’ global warming potential.


Sample Problem 14 Determination of a Water Hardness

Water has the following chemical

composition: [Ca2+] = 15 mg/L; [Mg2+] = 10

mg/L; [SO42-] = 30 mg/L. What is the total

hardness in units of mg/L as CaCO3?


6. Reporting Particle Concentration in Air

and Water

• Total suspended particulate (TSP) – the

increase in weight of the filter due to

collection of particulate divided by the

volume of air passed through the filter,

g/m3 or g/m3.


Sample Problem 15 Carbon Equivalent as a Common

Constituents

The US greenhouse gas emissions reported

in 2004 were 5,988 teragrams (Tg) CO2e OF

N2O. How many gigagrams (Gg) of CH4 and

N2O were emitted in 2004?



and Water


7. Representation by Effect

• Biological oxygen demand (BOD)

• Chemical oxygen demand (COD)


Sample Problem 16 Determining Concentration of Solids in a

Water Sample

A laboratory provides the following analysis obtained from a 50 mL

sample of wastewater: total solids = 200 mg/L, total suspended solids =

160 mg/L, fixed suspended solids = 40 mg/L, and volatile suspended

solids = 120 mg/L.

1. What is the concentration of total dissolved solids of this sample?

2. Suppose this sample was filtered through a glass-fiber filter, and

the filter was then placed in a muffle furnace at 550oC overnight.

What would be the weight of the solids (in mg) remaining on the

filter after the night in the furnace.

3. Is this sample turbid? Estimate the percent of the solids that are

organic matter.


THANK YOU


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ENVIRONMENTAL MEASUREMENT - WordPress.com · 2013. 8. 4. · Concentration in Environment • Concentration is the driving force that controls the movement of chemicals within and