Elements of Environmental Chemistry

Jonathan D. Raff, Ronald A. Hites

• Editorial: Wiley
• Año: 2020
• ISBN:
  9781119434894
• Edición: 3
• Categoría: Ciencias físicas
• Categoría: Química orgánica

A practical approach to environmental chemistry, Elements of Environmental Chemistry, 3 rd Edition provides readers with the fundamentals of environmental chemistry and a toolbox for putting them into practice. This is a concise, accessible, and hands-on volume designed for students and professionals working in the chemical and environmental sciences.

The 3 rd Edition has been completely revised and rearranged. The first chapter on tool skills has been expanded to include thermodynamic considerations and measurement issues. The former chapter on the partitioning of organic compounds has been expanded to cover the fates of organic compounds, with an emphasis on developing the readers chemical intuition for predicting a chemicals fate based on structure. The material on lead, mercury, pesticides, PCBs, dioxins, and flame retardants has been expanded and combined into the last chapter and supplemented with more references to the literature. The problem sets have been extended and now include over 130 problems, some of which can be solved using Excel.

1
Simple Tool Skills

There are several tasks that will occur over and over again as one works as an environmental scientist; we need to master them first. These tasks include unit conversions, estimating, the ideal gas law, stoichiometry, thermodynamic considerations, and measurement issues.

1.1 Unit Conversions

There are several important prefixes that you should know, and these are given in Table 1.1.

Table 1.1 Unit prefixes, their abbreviations, and their meanings.

Prefix	Abbreviation	Multiplier
yocto	y	10^−24
zepto	z	10^−21
atto	a	10^−18
femto	f	10^−15
pico	p	10^−12
nano	n	10^−9
micro	μ	10^−6
milli	m	10^−3
centi	c	10^−2
deci	d	10^−1
kilo	k	10^3
mega	M	10^6
giga	G	10^9
tera	T	10^12
peta	P	10^15
exa	E	10^18

For example, a nanogram is 10⁻⁹ g, a kilometer is 10³ m, and a petabyte is 10¹⁵ bytes, which is a lot.

For those of us forced by convention or national origin to work with the so‐called “English units,” here are some other handy conversion factors you should know

A handy formula for converting degrees Fahrenheit to degrees Centigrade is

There are some other common conversion factors that link length units to common volume and area units

One more unit conversion that we will find helpful is

Yes, we will spell metric tonnes like this to distinguish it from English tons, which are 2000 lb and also called “short tons.” One English ton equals one short ton and both equal 0.91 metric tonnes.

Another unit that chemists use to describe distances between atoms in a molecule is the Ångström,¹ which has the symbol Å and represents 10⁻¹⁰ m. For example, the C—H bond in an organic molecule is typically 1.1 Å, or 1.1 × 10⁻¹⁰ m. The O—H bond in water is only 0.96 Å long.

Let us do some simple unit conversion examples. The point is to carry along the units as though they were algebra and cancel out things as you go. Always write down your unit conversions. We cannot begin to count the number of people who looked foolish at public meetings because they tried to do unit conversions in their head. Even rocket scientists have screwed this up such that they once missed Mars.

Let us assume that human head hair grows at 0.5 in./month. How much hair grows in 1 s? Please use metric units.

Strategy: Let us convert inches to meters and months to seconds. Then depending on how small the result is, we can select the right length units

If you find scientific notation confusing, see footnote ². We can put this in more convenient units

So in 1 s, your hair grows about 5 nm. This is not much, but it obviously adds up second after second.

A word on significant figures: In the above result, the input to the calculation was 0.5 in./month, a datum with only one significant figure. Thus, the output from the calculation should not have more than one significant figure and should be given as 5 nm/s. In general, one should use a lot of significant figures inside the calculation, but round the answer off to the correct number of figures at the end. With a few exceptions, one should be suspicious of environmental results having four or more significant figures – in most cases, two will do. More on this later.

The total amount of sulfur released into the atmosphere per year by the burning of coal is about 75 million tonnes. Assuming this were all solid sulfur, how big...