Concentration in parts per billion

Figure 10.9 Example of a food chain biomagnification of PCB52 (2,2 ,5,5 ,-tetrachIorobiphenyI). Concentrations in parts per billion (ppb, i.e., fig L 1 or fig kg 1, respectively) of this PCB in each phase of two food chains (i) from water to phytoplankton to herbivorous mysids to carnivorous small fish to carnivorous large fish, and (ii) from bed sediments to de-trivorous amphipods to carnivorous small fish to carnivorous large fish. Data from a study of Lake Ontario (Oliver and Nimi, 1988) assuming all organisms were 80% water content to convert all concentrations to a dry-weight basis.

Persons are medically considered to have lead poisoning if they have a concentration of greater than 10 micrograms of lead per deciliter of blood. What is this concentration in parts per billion ... 

Conc(7) is the concentration of species j expressed in ppbC, oH(y> is the rate constant for the reaction between species j and OH, and oh(C,H6) is the rate constant for the reaction between OH and propene. Prop-Equiv(7) is a measure of the concentration of species j on an OH-reactivity-based scale normalized to the reactivity of propene and is literally the concentration (in parts per billion carbon) required of propene to yield a carbon oxidation rate equal to that of VOC species j. Thus if a VOC species has an atmospheric abundance of 10 ppbC and is twice as reactive as propene, its Prop-Equiv is 20 ppbC if the species is half as reactive as propene, its Prop-Equiv is 5 ppbC. The use of propene s reactivity as the normalization factor in the above formulation is completely arbitrary, and equivalent results would be obtained if the reactivity of any other species is chosen. 

About ten years ago, all ESBR plants modified their processes to eliminate die presence of volatile nitrosamines. These potentially carcinogenic chemicals were present at concentrations in parts per billion. The changes made eliminated the use of sodiiun nitrite and one component of the short stop system, sodium dimethyl dithiocarbamate. 

---