Question

questions 1 through 3 refer to the following.
summary of mean water quality results
green roof
control roof
precipitation
water quality
mean
mean
mean
parameter
ph
7.28
6.27
4.82
nitrate (mg/l)
0.27
0.87
0.6
ammonium (mg/l)
0.86
1.47
1.19
total phosphorus
0.47
0.25
0.21
(mg/l)
magnesium (mg/l)
2.92
0.25
0.20
boron (mg/l)
0.58
0.03
0.00
green roofs offer many environmental advantages, including the removal of some pollutants from
rainwater. the parameters in the table above were measured in water samples collected after rainfall had
passed through green roofs and over traditional roofs (n = 5) in new york city. mean levels of ph and
pollutants in precipitation are shown in the table.
3
mark for review
assume that the rainwater from one of the green roofs ran off directly into a nearby lake. water quality
results from which of the following parameters show that the green roof would likely improve water quality
in the lake?
a total phosphorus
b magnesium
c boron
d nitrate

Explanation:

Step1: Analyze each option

• Total phosphorus: Green roof mean ($0.47$) is higher than control roof ($0.25$) and precipitation ($0.21$), so it won't improve water quality.
• Magnesium: Green roof mean ($2.92$) is much higher than control roof ($0.25$) and precipitation ($0.20$), so it won't improve water quality.
• Boron: Green roof mean ($0.58$) is higher than control roof ($0.03$) and precipitation ($0.00$), so it won't improve water quality.
• Nitrate: Green roof mean ($0.27$) is lower than control roof ($0.87$) and close to precipitation ($0.6$). A lower nitrate level is better for water quality.

Answer:

D. Nitrate