CFL bulbs contain mercury in a gaseous, elemental form, with an average content of 3.5 mgHg/CFL. When broken, Hg is released from the bulb and can present a hazard to those exposed. CFL production grew rapidly between 2004 and 20084, at which point CFL demand continued to grow but at a slower pace. CFLS last an average of 6 years in use, so, for example,a bulb produced in 2004 is expected to retire (i.e., be discarded) in 2010. To calculate material flows in the year 2017, you'll need to know how many bulbs were sold and put into use in 2011.Approximately 400,000,000 CFL bulbs were sold in 2011, and 550,000,000 were sold in 20175.
Assume that CFLS only break in the home when they are being installed or removed. Assume that 2% of all bulbs sold are broken during installation (i.e. have a lifetime of zero years),and 2% are broken during removal (i.e. after a lifetime of 6 years). Assume that Hg in broken bulbs goes directly to air or soil where the bulbs are broken. The other fates for CFL bulbs include disposal in the trash leading to land filling, and proper recycling. Only 15% of removed bulbs are recycled, the rest are broken or destined for landfills. Table 2 describes the environmental fate of mercury (either to air, soil and water, or back into production via recycling).
Calculate the following mercury stocks and flows (as illustrated on the MFA diagram) for the year 2017. Please report values in kilograms rounded to the nearest whole number.
a) Assuming that all CFLS sold before 2011 have already been discarded, use Table 1 to calculate
The total in-use stock of Hg in CFLS in 2017. Note that 1 kg = 103 g = 106 mg.
ii)that have reached 6 years of age are discarded. By convention, a net addition to stock is reported as a positive number, and a net decrease to stock as a negative number. Report your results in kg.The net addition to in-use stock (Ns) of Hg in the year 2017. Assume all bulbs
Calculate B (Hg from broken CFLS), and the quantity of Hg to air and soil/water. Report your results in kg.
c) Calculate D Landfll, the amount of Hg discarded to landfill, and the quantity to air and soil/water. Report your results in kg.
Calculate D Recycling, the amount of Hg recycled. Report your results in kg.
O Calculate the total addition of Hg to the atmosphere due to CFLS. Report your results in kg.
Calculate the total addition of Hg to soil and water due to CFLS. Report your results inkg.
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