Common Contaminants in Urban Watersheds - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 253

7.8.6 Acids and Bases

An acid increases the concentration of the hydrogen ion H + when dissolved in water and
lowers the pH (potential hydrogen) of the solution. The bare hydrogen ion, H + , is short for
the hydronium ion, H 3 O + , since a bare H + does not exist in a solution. Conversely, a base
increases the concentration of the hydroxide ion OH - when dissolved in water, and raises
the pH of the solution (Meyers 2003). Common acids and bases are listed in Table 7.15
(Meyers 2003).
We recognize acids and bases by their simple properties, such as taste, and conclude
the sour taste of a lemon indicates it must be acidic. Bases tend to taste bitter. On the pH
scale, any substance with a pH less than 7 (the neutral point) is acidic and any substance
having a pH greater than 7 is basic. Acids and bases are widely used in industry, and are
present in many widely consumed foods and drinks. Stronger acids and bases are used
in household cleaners and detergents, especially those used on glassware and in ovens
(USEPA 2008a).
Acids or bases are only toxic if they are strong, meaning they are of relatively low or
high pH. Exposure to strong acids and strong bases causes respiratory irritation and burn-
ing, and causes skin burns. Significant exposure may cause severe burns and even death
(USEPA 2009b). Currently, adequate information is not available to evaluate the potential
carcinogenic effects of common acids and bases (USEPA 2009b).
Ammonia is a common basic chemical widely used as a household cleaning agent and
in many industrial applications (ATSDR 2004). Ammonia is present naturally throughout
the environment in air, soil, and water. Exposure to high levels of ammonia may cause
lung, skin, and throat irritation. Some people with asthma may react more negatively to
the inhalation of ammonia (ATSDR 2004b).
Hydrochloric acid (also referred to as hydrogen chloride) is a common acid widely used
in industry as a cleaning agent, in the manufacturing of PVC, in making steel, and making
leather. Hydrochloric acid is also present in humans and other organisms as a gastric acid

TABLE 7.15
Common Acids and Bases
Common Acids Common Bases

Acid Chemical Formula Base Chemical Formula

Acetic acid HC 2 H 3 O 2 Ammonia NH 3

Benzoic acid HC 7 H 5 O 2 Aniline C 6 H 5 NH 2

Boric acid H 3 BO 3 Dimethylamine (CH 3 ) 3 NH

Carbonic acid H 2 CO 3 Ethylamine C 2 H 5 NH 2

Cyanic acid HCNO Hydrazine H 2 H 4

Formic acid HCNO 2 Hydroxylamine NH 2 OH

Hydrocyanic acid HCN Methylamine CH 3 NH 2

Hydrofluoric acid HF Pyridine C 5 H 5 N

Hydrogen sulfide H 2 S Urea NH 2 CONH 2

Hydrochloric acid HCl Potassium hydroxide KOH

Nitric acid HNO 3 Sodium bicarbonate NaHCO 3

Phosphoric acid H 3 PO 4 Sodium hydroxide NaOH

Pyruvic acid HC 3 H 3 O 3 Calcium hydroxide Ca(OH) 2

Sulfuric acid H 2 SO 4