Biological remediation

Biological remediation  -  a treatment process using microorganisms to break down, or degrade organic contaminants or toxic hazardous into less toxic or nontoxic substances.

What would modern life be like without plastic? However,  plastic bags, due to biodegrade resistant, can take between 400 to 1,000 years to break down, because of photodegrade.  When breaking down, it contaminates soil and waterways. Nearly 90% of the debris in our oceans is plastic, which causes over 100,000 seabirds, fish, turtles and other marine life deaths every year when animals mistake them for food.

In the past decade, scientists and engineers have been trying to find plastic-eating organisms to break down plastic substances into - opening a new door to solve the global plastic problem for our environment - according to the United Nations Environmental Programme, global plastic consumption has gone from 5.5 million tons in the 1950s to 110 million tons in 2009. only less than 10%, for example in American, of the total gets recycled, and the rest presents great challenges, ranging from water contamination to marine animal skilling.

 

According to the news published in Scienceblog, some bacteria could help transform a key component of disposable cups, plates and utensils into a useful eco-friendly plastic, significantly reducing the environmental impact of this ubiquitous, but difficult-to-recycle waste stream.

Kevin O’Connor and  his colleagues have found a special strain of the soil bacterium Pseudomonas putida, converted polystyrene foam — commonly known as Styrofoam into a biodegradable plastic leading to

the possibility of converting a petroleum-based plastic waste into a reusable biodegradable form.

 

Mealworm,  the tiny worm, which is the larvae form of the darkling beetle, according to the paper published in  published in Environ. Sci. Technol., 2015, 49 (20), pp 12080–12086,

can subsist on a diet of Styrofoam and other forms of polystyrene. The study was the first to provide detailed evidence of bacterial degradation of plastic in an animal’s gut. Understanding how bacteria within mealworms carry out this feat, according to  co-authored by Dr. Wu, a senior research engineer in the Department of Civil and Environmental Engineering at Stanford, could potentially enable new options for safe management of plastic waste.

 

Image source - Environ. Sci. Technol., 2015, 49 (20), pp 12080–12086,

 

 

 

 

 

Ozone depletion

Ozone molecule consists of three bonded atoms of oxygen, which is unstable and highly reactive. In the lower atmosphere, ozone is a serious pollutant,  in the stratosphere, ozone, however, is an essential shield against ultraviolet radiation, where Ozone screens out 99% of all UV solar radiation.

Ozone depletion and CFCs

In 1974, a controversial hypothesis was proposed, suggesting that chlorofluorocarbons (CFCs) deplete stratospheric ozone. This hypothesis was based on the observations that CFCs are extremely stable in the lower atmosphere, they readily migrate to the stratosphere,  where they can be broken down by intense UV radiation, and the freed chlorine free radical can then catalyze the destruction of stratospheric ozone (e.g., CFCl₂):

                             CFCl₃ + light         ------>       Cl●    +    CFCl₂           (1)

                               Cl●     +    O₃        ------>     ClO    +       O₂               (2)

                              ClO     +   O₃       ------>       Cl●    +        2O₂             (3)

Ozone depletion thus results in significantly increased levels of biologically damaging and effects on human health, including sunburn, skin cancer, and cataracts,  as increased UV solar radiation reaches the earth’s surface.

Emission and uses of ozone-depleting chemicals
CFCs and other ozone destroyers have been widely used as aerosol propellants, refrigerants, blowing agents, cleaning solvents, and fire extinguishing agents. CFCs are thought to be responsible for most ozone depletion. Though restricted for use as aerosol propellants, CFCs are still widely used as refrigerants, and this use shows an upward trend.

The Antarctic ozone hole
Much of the world’s stratospheric ozone is produced near the equator, However, air  circulation patterns produce the greatest concentration of ozone in the polar regions. The term ozone hole refers to springtime thinning of the ozone layer above Antarctica; such thinning has been observed since the 1970s.

An Arctic ozone hole?
The ozone-deficient air masses that form over the North Pole are more mobile than those over Antarctica, thus threatening some densely populated regions of northern continents.

Tropical and midl-atitude ozone depletion
Conditions conducive to ozone depletion may occur in the tropics and mid-latitudes. Volcanic eruptions in tropical latitudes may contribute sulphur-based aerosols which trigger the necessary reactions.

Environmental effects
The potential environmental effects of ozone depletion include damage to aquatic and terrestrial food chains and a variety of  human health effects. Increased UVB exposure resulting from ozone destruction can educe primary productivity in marine food chains, thus affecting all  trophic levels and perhaps disrupting the global carbon cycle. Agricultural harvests could be negatively affected by widespread ozone depletion. Increased UV radiation due to ozone depletion is expected to increase human skin cancers and cataracts and to suppress human immune system functions.         

Ozone depletion prevent - collection and Reuse of CFCs
CFCs in refrigerators, automobiles, and other cooling systems can be collected and reused rather than discarded.

Substitutes for CFCs
The two major substitutes for CFCs, HFCs and HCFCs, are less ozone-destructive
than CFCs, but are costly and may have other environmental effects. Other CFC substitutes, such as helium and propane, show great promise but face technological and/or economic difficulties in development .

Short-term adaptation to ozone depletion
Given the realities of present and future ozone depletion, the most sensible short- term approach will center on human adaptation to increased UV levels and increased commitment to researching the ecological implications of ozone depletion.

My persona favourite tips to prevent ozone depletion:
1. Minimising person vehicle driving
2. Understanding it illegal to recharge refrigerators, freezers and home/vehicle air
    conditioners with CFCs
3. Not  purchasing or using portable fire extinguishers that contain halons
4. Using environmental-friendly household products
5. Minimising using pesticides.