Question

Suppose a gaseous substance is emitted by an industrial facility, outside of a city, and that this substance has a very low inhalation LD50 value of 0.2 µg/kg/day.

a. Explain the meaning and units of LD50. Given the ‘very low’ description, would you guess that the substance is generally toxic or non-toxic? Explain your answer.

b. A low-pressure system is sitting over the city. How will this affect the transport of the pollutant relative to the city center, i.e., will it move towards or away the center, and why?

c. Assuming that city authorities do not know the source of the pollutant at first, suggest how monitoring equipment could be used/deployed around the city in order to determine the direction of the point source.

d. Suppose the industrial facility is in a rural area and has plenty of land, and now needs to control a relatively small volumetric flow Q of the gaseous pollutant. What control technology would you suggest and why? (Hint: there are two good options.)

Answer 1

A)LD means "Lethal Dose". LD50 is the amount of a material,which causes the death of 50% of a group of test animals.It is usually expressed as the amount in milligrams per 100 grams for smaller animals or per kilogram for bigger test subjects of the body weight of the test animal.

Route of entry for LD50 may be either applied to the skin or given by mouth.It is extremely toxic when inhaled.Given that 0.2 µg/kg/day has been inhaled it seems to be highly toxic.

B)Passenger vehicles are a major pollution contributor, producing significant amounts of nitrogen oxides, carbon monoxide, and other pollution.Low-pressure systems play an important role in the development and transport of pollutants. They tends to force long-range transport of pollutants.They also work as a cleaning and scavenging mechanism of pollutants.A low-pressure system is also able to effectively lift pollutants through their associated cold-frontal activities and transport them away from city centre.

C) Monitoring equipment can be depoloyed on dividing the polluted areas into various zones the zones can be categorized as:

1.Ozone Monitoring in Extreme Environments-2B Technologies instruments were designed from the beginning to deal with harsh environments.
2.Measurements from Aircraft and Balloons
3.Indoor Air Quality Monitoring
4.Roadside Monitoring for NO, NO2 and NOx

D) Control measures for pollutants at rural areas may be:

1.formulate or improve relevant laws, regulations and standards on rural
environmental protection
2.raise the approval level of environmental impact statements of construction
projects for farming, livestock husbandry etc.
3.Strictly implement EIA system for rural construction projects
4.The rural environmental management should be strengthened
5.The rural environmental protection education should be intensified