Question

Last Tuesday the Belmont Fire Department was dispatched to the westbound lane of State Highway 123 for an accident involving a dump truck on fire.

Engine 2 responded with a crew of five, followed shortly after by Engine 3 with a crew of four. Engine 2 arrived to find an overturned dump truck with the cab fully involved and the driver self-extricated. Engine 2’s crew pulled one of the front bumper lines and started their fire attack. They were followed closely behind by Engine 3’s crew, who pulled the other line and helped with the fire suppression.

The operator of the vehicle suffered minor abrasions and declined further treatment.

The dump truck was carrying ash from a local incinerator that burns trash to generate electricity. Much of the ash was carried into a nearby stream during the fire suppression. Local authorities and the EPA were notified of a spill of ash with potential toxins into the local watershed.

1. Explain where the truck was most likely headed.
2. Identify three potential toxins in the ash and their probable source.
3. For two of the toxins you identified, discuss their potential effects on the stream ecology downstream.

Answer 1

1. The dump truck was carrying ash from a local incinerator. Hence in most probability, the truck was heading towards dumping ground located on the outskirts of the city or in an isolated place devoid of human settlements and dense population (commonly known as landfills).

It is a normal practice around the world and in the US, fly ash which is obtained as a residue after burning of wastes is used as landfill or used for the production of hydraulic cement. Since the questions mention the truck as dump trucks, it could be assumed as they were trucks used for dumping the ash at landfill sites or dumping grounds.

2. Fly ash or simply ash which is obtained after burning of wastes in an incinerator or coal-based power plants are toxic. This toxicity is due to the presence of heavy metals which are mostly toxic to humans and the environment alike.

The most common toxins in the ash include-

• Lead- Lead is present in different types of electronic wastes, cosmetic products, batteries etc.
• Mercury- Mercury is widely found in electric flat panel displays, thermostats, lamps, mobile phones, medical equipment, relays and sensors.
• Arsenic- Arsenic is commonly used in semiconductors, chemical compounds, bronze products, LED’s and laser diodes. Mostly Arsenic occurs in combination with lead.

3. All the above-mentioned toxins along with other toxins are extremely dangerous to humans and the environment. If ingested they can prove to be lethal to human beings. On mixing with water, they deteriorate its quality and impact the ecology thus causing environmental pollution and degradation.

• Arsenic- Arsenic after being carried downstream, mixes with the stream and impacts humans and the environment. They are known to cause death, reduced growth, reproduction and photosynthesis as well as behavioural defects. In extreme cases, complete flora and fauna are obliterated leaving just a few species to survive. Moreover, downstream increased concentration of arsenic exhibits biomagnification phenomenon as well as increased growth of plants that absorb it such as hydrilla, sea pink thrift and others.
• Lead- Lead is the most potent of all toxins present. It remains in the water and eventually makes its way to soils, humans and air. It influences the water chemistry and forms lead compounds in the water. They are known to poison the fishes and other aquatic animals in the water bodies thus leading to desertification of the body. It also exhibits the phenomenon of bioaccumulation and biomagnification.