Chapter 21, Problem 101A

Interpretation Introduction

Interpretation:

The reason for low levels of PAH in the late 1800s and early 1900s needs to be explained.

Concept introduction:

PAH is a short form of polycyclic aromatic hydrocarbons that contain two or more fused aromatic rings. They are naturally occurring compounds and human activities can result in increase in the concentration of PAH in the environment.

Explanation of Solution

Given:

From the given figure, the average PAH concentration before 1905 is quite low that is from $\text{0-4 μg/g}$ and after 1925 is from $\text{11-15 μg/g}$. The large increase in concentration is observed from 1905 to 1925 due to increase in burning of fossil fuels.

The reason for low levels of PAH in the late 1800s and early 1900s is due to less use of electricity. But after 1905, the use of electricity increases which was produced from the energy derived from burning of fossil fuels and thus, resulting in increase in concentration level of PAHs after 1905.