Passage IV
Burning household waste in metal barrels can release harmful emissions (airborne gases and particulates), including SO2, CO, NO2, dioxin, lead, and mercury. The remaining ash also may contain toxic substances. Two studies examined these emissions and ash.
Study 1
Two hundred pounds of household waste designated for burning was collected from 12 households. The waste was placed in a metal barrel located under a hood that collected emissions (see Figure 1). The waste was burned for 2 hours at 400°F to 500°F. The average reduction in the weight and the volume of the original waste after burning was 58% and 70%, respectively.
The concentrations of emissions, in parts per million (ppm), were measured. Table 1 shows the results and the established maximum allowed concentrations in emissions from incinerators (facilities that burn large quantities of household waste).
Study 2
The ash from the burned waste in Study 1 was analyzed for the presence of several substances, including mercury and lead. Table 2 shows the measured concentrations in the ash and the established limit that, if exceeded for any one of the substances, means the sample of ash would be considered hazardous.
Figure and tables adapted from Chris Burger, “Emission Characteristics of Burn Barrels.” ©1994 by Patrick Engineering, Inc.
21. If Study 2 had been repeated using the waste from 15 households instead of 12 households, the resulting measured concentration for each substance in the repeated Study 2 would most likely have been:
Your Answer is
Correct Answer is B
Explanation
No matter how many households are used to test, the concentration should be similar, because the household garbage composition of each household should be similar