Category Science

WHAT IS NITROGEN CYCLE? WHAT ARE THE STAGES OF NITROGEN CYCLE?

Our atmosphere is made up of 78% nitrogen. This element is essential for all living beings but we cannot directly take the nitrogen from the environment. We must absorb it through our food. The nitrogen cycle follows the circulation of nitrogen from the atmosphere to the soil, to animals and back. Nitrogen in the atmosphere falls to the earth through snow and rain. Once in the soil, the nitrogen combines with the hydrogen on the roots of the plants to form ammonia. This process is called Nitrogen fixation. Additional bacteria further combine this ammonia with oxygen in a process called Nitrification. At this point, the nitrogen is in a form called nitrite, which is further converted into nitrate by the bacteria. Plants can absorb nitrogen in this state through a process called assimilation and the rest is utilised by the bacteria. The remainder is released back into the atmosphere through the process of denitrification.

Nitrogen Cycle Explained – Stages of Nitrogen Cycle

Process of the Nitrogen Cycle consists of the following steps – Nitrogen fixation, Nitrification, Assimilation, Ammonification and Denitrification. These processes take place in several stages and are explained below:

Nitrogen Fixation Process

It is the initial step of the nitrogen cycle. Here, Atmospheric nitrogen (N2) which is primarily available in an inert form, is converted into the usable form -ammonia (NH3).

During the process of Nitrogen fixation, the inert form of nitrogen gas is deposited into soils from the atmosphere and surface waters, mainly through precipitation.

The entire process of Nitrogen fixation is completed by symbiotic bacteria, which are known as Diazotrophs. Azotobacter and Rhizobium also have a major role in this process. These bacteria consist of a nitrogenase enzyme, which has the capability to combine gaseous nitrogen with hydrogen to form ammonia.

Nitrogen fixation can occur either by atmospheric fixation- which involves lightening, or industrial fixation by manufacturing ammonia under high temperature and pressure conditions. This can also be fixed through man-made processes, primarily industrial processes that create ammonia and nitrogen-rich fertilisers.

Assimilation

Primary producers – plants take in the nitrogen compounds from the soil with the help of their roots, which are available in the form of ammonia, nitrite ions, nitrate ions or ammonium ions and are used in the formation of the plant and animal proteins. This way, it enters the food web when the primary consumers eat the plants.

Ammonification

When plants or animals die, the nitrogen present in the organic matter is released back into the soil. The decomposers, namely bacteria or fungi present in the soil, convert the organic matter back into ammonium. This process of decomposition produces ammonia, which is further used for other biological processes.

Denitrification

Denitrification is the process in which the nitrogen compounds make their way back into the atmosphere by converting nitrate (NO3-)  into gaseous nitrogen (N). This process of the nitrogen cycle is the final stage and occurs in the absence of oxygen. Denitrification is carried out by the denitrifying bacterial species- Clostridium and Pseudomonas, which will process nitrate to gain oxygen and gives out free nitrogen gas as a byproduct.

Conclusion

Nitrogen is abundant in the atmosphere, but it is unusable to plants or animals unless it is converted into nitrogen compounds.

Nitrogen-fixing bacteria play a crucial role in fixing atmospheric nitrogen into nitrogen compounds that can be used by plants.

The plants absorb the usable nitrogen compounds from the soil through their roots. Then, these nitrogen compounds are used for the production of proteins and other compounds in the plant cell.

Animals assimilate nitrogen by consuming these plants or other animals that contain nitrogen. Humans consume proteins from these plants and animals. The nitrogen then assimilates into our body system.

During the final stages of the nitrogen cycle, bacteria and fungi help decompose organic matter, where the nitrogenous compounds get dissolved into the soil which is again used by the plants.

Some bacteria then convert these nitrogenous compounds in the soil and turn it into nitrogen gas. Eventually, it goes back to the atmosphere.

These sets of processes repeat continuously and thus maintain the percentage of nitrogen in the atmosphere.

Credit : BYJU’S 

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WHAT IS NUCLEAR POWER AND ENERGY?

An atom is the building block of all matter. Nuclear energy is the energy that exists at the core of the atom called the nucleus. Nuclear energy can be accessed through two kinds of atomic reactions nuclear fission and nuclear fusion. In the first reaction, atoms are broken apart whereas in the latter they are forced to fuse together. However, to date, nuclear power plants do not have a safe and reliable way to generate energy through nuclear fusion. Therefore, nuclear reactors use uranium as fuel to produce energy by nuclear fission.

World nuclear power

Nuclear power provides almost 15 percent of the world’s electricity. The first nuclear power plants, which were small demonstration facilities, were built in the 1960s. These prototypes provided “proof-of-concept” and laid the groundwork for the development of the higher-power reactors that followed.

The nuclear power industry went through a period of remarkable growth until about 1990, when the portion of electricity generated by nuclear power reached a high of 17 percent. That percentage remained stable through the 1990s and began to decline slowly around the turn of the 21st century, primarily because of the fact that total electricity generation grew faster than electricity from nuclear power while other sources of energy (particularly coal and natural gas) were able to grow more quickly to meet the rising demand. This trend appears likely to continue well into the 21st century. The Energy Information Administration (EIA), a statistical arm of the U.S. Department of Energy, has projected that world electricity generation between 2005 and 2035 will roughly double (from more than 15,000 terawatt-hours to 35,000 terawatt-hours) and that generation from all energy sources except petroleum will continue to grow.

In 2012 more than 400 nuclear reactors were in operation in 30 countries around the world, and more than 60 were under construction. The United States has the largest nuclear power industry, with more than 100 reactors; it is followed by France, which has more than 50. Of the top 15 electricity-producing countries in the world, all but two, Italy and Australia, utilize nuclear power to generate some of their electricity. The overwhelming majority of nuclear reactor generating capacity is concentrated in North America, Europe, and Asia. The early period of the nuclear power industry was dominated by North America (the United States and Canada), but in the 1980s that lead was overtaken by Europe. The EIA projects that Asia will have the largest nuclear capacity by 2035, mainly because of an ambitious building program in China.

A typical nuclear power plant has a generating capacity of approximately one gigawatt (GW; one billion watts) of electricity. At this capacity, a power plant that operates about 90 percent of the time (the U.S. industry average) will generate about eight terawatt-hours of electricity per year. The predominant types of power reactors are pressurized water reactors (PWRs) and boiling water reactors (BWRs), both of which are categorized as light water reactors (LWRs) because they use ordinary (light) water as a moderator and coolant. LWRs make up more than 80 percent of the world’s nuclear reactors, and more than three-quarters of the LWRs are PWRs.

Issues affecting nuclear power

Countries may have a number of motives for deploying nuclear power plants, including a lack of indigenous energy resources, a desire for energy independence, and a goal to limit greenhouse gas emissions by using a carbon-free source of electricity. The benefits of applying nuclear power to these needs are substantial, but they are tempered by a number of issues that need to be considered, including the safety of nuclear reactors, their cost, the disposal of radioactive waste, and a potential for the nuclear fuel cycle to be diverted to the development of nuclear weapons. All of these concerns are discussed below.

Safety

The safety of nuclear reactors has become paramount since the Fukushima accident of 2011. The lessons learned from that disaster included the need to (1) adopt risk-informed regulation, (2) strengthen management systems so that decisions made in the event of a severe accident are based on safety and not cost or political repercussions, (3) periodically assess new information on risks posed by natural hazards such as earthquakes and associated tsunamis, and (4) take steps to mitigate the possible consequences of a station blackout.

Credit : Britannica 

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WHAT IS METHANE?

Methane is a hydrocarbon, which means that it is a compound made up of hydrogen and carbon atoms. It naturally occurs as an odourless, colourless, and tasteless gas. It is 25 times more dangerous Greenhouse gas than carbon dioxide. It can either be introduced into the environment by natural processes like the decomposition of the organic matter or by human activities like coal oil and natural gas extractions from the Earth, uncovered or poorly managed landfills and the burning of fossil fuels to name a few.

PRIMARY SOURCES OF METHANE EMISSIONS

Atmospheric methane concentrations have grown as a result of human activities related to agriculture, including rice cultivation and ruminant livestock; coal mining; oil and gas production and distribution; biomass burning; and municipal waste landfilling. Emissions are projected to continue to increase by 2030 unless immediate action is taken.

In agriculture, rapid and large scale implementation of improved livestock feeding strategies can reduce of 20% of global methane emissions by 2030, while full implementation of intermittent aeration of continually flooded rice paddies (known as alternate wetting and drying cultivation) could reduce emission from rice production by over 30%.

Emissions from coal mining and the oil and gas sector could be reduced by over 65% by preventing gas leakage during transmission and distribution, recovering and using gas at the production stage, and by pre-mine degasification and recovery of methane during coal mining.

METHANE IMPACTS

  • CLIMATE IMPACTS

Methane is generally considered second to carbon dioxide in its importance to climate change. The presence of methane in the atmosphere can also affect the abundance of other greenhouse gases, such as tropospheric ozone, water vapor and carbon dioxide.

Recent research suggests that the contribution of methane emissions to global warming is 25% higher than previous estimates.>

  • HEALTH IMPACTS

Methane is a key precursor gas of the harmful air pollutant, tropospheric ozone. Globally, increased methane emissions are responsible for half of the observed rise in tropospheric ozone levels.

While methane does not cause direct harm to human health or crop production, ozone is responsible for about 1 million premature respiratory deaths globally. Methane is responsible for about half of these deaths.

SOLUTIONS

The relatively short atmospheric lifetime of methane, combined with its strong warming potential, means that targeted strategies to reduce emissions can provide climate and health benefits within a few decades.

The Coalition supports implementation of control measures that, if globally implemented by 2030, could reduce global methane emissions by as much as 40%. Several of these emission reductions could be achieved with net savings, providing quick benefits for the climate as well as public health and agricultural yields.

Credit : Climate & clean air coalition   

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WHAT IS A MONSOON SEASON?

A monsoon is a seasonal wind pattern that lasts for several months and results in heavy rainfall during the summer and dry spells in the winter. It is responsible for the wet and dry seasons throughout much of the tropics. Typically Indian monsoon lasts from June-September, with large areas of western and central India receiving more than 90% of their total annual precipitation during the period. The word comes from the Arabic ‘mausin’ which means season and was first used in the English language during the British occupation of India.

What causes a monsoon?

A monsoon (from the Arabic mawsim, which means “season”) arises due to a difference in temperatures between a land mass and the adjacent ocean, according to the National Weather Service. The sun warms the land and ocean differently, according to Southwest Climate Change, causing the winds to play “tug of war” eventually switching directions bringing the cooler, moister air from over the ocean. The winds reverse again at the end of the monsoon season.

Wet versus dry

A wet monsoon typically occurs during the summer months (about April through September) bringing heavy rains, according to National Geographic. On average, approximately 75 percent of India’s annual rainfall and about 50 percent of the North American monsoon region (according to a 2004 NOAA study) comes during the summer monsoon season. The wet monsoon begins when winds bringing cooler, more humid air from above the oceans to the land, as described above.

A dry monsoon typically occurs between October and April. Instead of coming from the oceans, the winds tend to come from drier, warmer climates such as from Mongolia and northwestern China down into India, according to National Geographic. Dry monsoons tend to be less powerful than their summer counterparts. Edward Guinan, an astronomy and meteorology professor at Villanova University, states that the winter monsoon occurs when “the land cools off faster than the water and a high pressure develops over the land, blocking any ocean air from penetrating.” This leads to a dry period.

The winds and rains

The monsoon season varies in strength each year bringing periods of lighter rains and heavier rains as well as slower wind speeds and higher wind speeds. The Indian Institute of Tropical Meteorology has compiled data showing yearly rainfalls across India for the last 145 years.

According to the data, the intensity of a monsoon varies over an average of period of 30 – 40 years. In each period, the amount of rain received is higher than average resulting in many floods or lower than average resulting in droughts. The long-term data suggest that the monsoon trends may turn from being in a low rain period that began in approximately 1970 to a higher rain period. Current records for 2016 indicate that total rainfall between June 1 and September 30 is 97.3 percent of the seasonal normal.

The most rain during a monsoon season, according to Guinan, was in Cherrapunji, in the state of Meghalaya in India between 1860 and 1861 when the region received 26,470 millimeters (1,047 inches) of rain. The area with the highest average annual total (which was observed over a ten year period) is Mawsynram, also in Meghalaya, with an average of 11,872 millimeters (467.4 inches) of rain.

The average wind speeds in Meghalaya during peak summer monsoon season average 4 kilometers per second and typically vary between 1 and 7 kilometers per hour, according to Meteoblue. During the winter months, wind speeds typically vary between 2 and 8 kilometers per hour with an average of 4 – 5 kilometers per hour.

Credit : Live science 

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WHAT ARE KEYSTONE SPECIES?

Keystone species play a unique and crucial role in the functioning of an ecosystem. The animals and organisms that come under this category help to maintain biodiversity within their community either by controlling populations of other species that would otherwise dominate the community or by providing critical resources for the survival of a wide range of organisms.

These species act as the glue that holds the system together. The term was coined by Dr Robert Paine in 1969, to describe the power a single species exerts on an ecosystem. Examples of keystone species include starfish, sea otters, beavers, wolves, elephants, prairiedogs and bees.

Keystone Species Examples

Sea Otter

The sea otter (shown below) is considered a keystone species as their consumption of sea urchins, preventing the destruction of kelp forests caused by the sea urchin population. Kelp forests are a critical habitat for many species in nearshore ecosystems. In the absence of sea otters, sea urchins feed on the nearshore kelp forests, thereby disrupting these nearshore ecosystems. However, when sea otters are present, their consumption of sea urchins restricts the sea urchin population to smaller organisms confined to protective crevices. Thus, the sea otter protects the kelp forests by reducing the local sea urchin population.

Large Mammalian Predators

While small predators are important keystone species in many ecosystems, as mentioned above, large mammalian predators are also considered keystone species in larger ecosystems. For example, the lion, jaguar (shown below), and gray wolf are considered keystone species as they help balance large ecosystems (e.g., Central and South American rainforests) by consuming a wide variety of prey species.

Sea Star

Sea stars (shown below) are another commonly recognized keystone species as they consume mussels in areas without natural predators. In many cases, when the sea star is removed from an ecosystem, the population of mussels proliferates uncontrollably, and negatively effects the resources available to other species within the ecosystem.

Credit :  Biology dictionary  

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WHAT IS LANDFILL? HOW DO LANDFILLS WORK?

A landfill is a dumping ground for waste materials. It is the systematic disposal of garbage or trash by burying it in the ground. Most modern landfills are designed in a way that they reduce contamination of the nearby groundwater and soil. Nowadays, they are also completely sealed to prevent the methane that is generated by the decomposing waste from diffusing in the environment.

How Do Landfills Work?

Modern landfills are built using a layering system designed to safely isolate waste and monitor any byproducts, leaks and anything else that can harm the environment. Isolating the trash from air and water is vital for preventing contamination.

We can learn more about how landfills work by examining each layer.

Cells (Old and new)

Each day, trash is compacted a cell in order to make the most of the space available in the landfill. The day’s work cell is also known as the daily workface. Here, trash is organized in layers or lifts then compacted accordingly.

Heavy machinery like bulldozers and compaction equipment are used to compress the trash and place it in the landfill. A six inch layer of dirt covers the cell after it’s made and is then compacted once more. This layer helps contain odors and prevent unwanted pests. Some landfills are considering alternatives like tarps or cement emulsions to save space.

The Liner System

The bottom layer of the landfill consists of a liner that keeps trash and byproducts separate from the environment and groundwater. Some facilities use more than one type, but at any landfill you’ll find at least one of the below liners.

Compact clay liners: These liners are normally made of dense, compacted clay solid enough to prevent waste, liquid or gas leaks from seeping into the environment.

Plastic liners: These liners are made of dense plastic and other synthetic materials, normally 30 to 100 mils thick. Plastic liners are typically used in municipal solid waste (MSW) landfills.

The Drainage System

On top of the liner, you’ll find a storm water drainage system that filters out both the liquids produced by trash and the water collected from rain and snow. This layer is important because it separates produced liquids from solid waste. Another drainage system is used to specifically filter out the liquid produced by trash, called leachate, from any rainwater and the rest of the landfill.

Gas Collection System

The gas collection system uses extraction wells and pipes throughout the landfill to carry landfill gas that’s generated when waste decomposes to treatment areas where it is then vented, burned or converted into energy.

Cap

A landfill is permanently capped with a plastic liner when it is full. After it’s capped, the landfill is covered with two feet of soil. Then, vegetation (normally grass and plants without penetrating roots) is planted on top to prevent soil erosion due to rainfall and wind. The landfill is monitored for 30 years to ensure there is no detrimental impact to the environment.

As you can see, today’s landfills are a far cry from the disease-ridden dumps from years before. The industry is also exploring other ways to make landfills cleaner, safer and more environmentally friendly in addition to the processes we’ve already mentioned. See below to learn a few ways landfills are becoming more sustainable.

Credit : Big Rentz

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