An acidic threat to aquatic organisms

Acid rain is the one of the quintessential phenomena that portrays the negative outcomes of human activity and can occur in the form of rain, snow, sleet or fog. Though some rain can be naturally acidic, our activities are making it worse.

What causes acid rain?

When compounds like sulfur dioxide and nitrogen oxides are released into the atmosphere, they travel upwards and react with water, oxygen and other chemicals to form sulfuric and nitric acids. These acids then mix with water and other materials and fall down as ‘acid rain’.

Acid rain may be caused by natural sources. For instance, small proportions of sulfur dioxides and nitrogen oxides are emitted into the atmosphere by volcanoes. The resultant rain from these compounds is mildly acidic in nature. When such rain falls to the ground, alkaline materials present in streams, lakes, soils, etc. neutralize it and prevent it from causing any harm.

What happens when the rain becomes more acidic? Will nature be able to neutralize strongly acidic rains? Sadly, the answer is no. Natural neutralization sources can’t handle acidity levels beyond their capacity. Thus, these sources may even be washed away by acid rain, thereby perilously breaking the fine balance in nature.

What makes mildly acidic rain more acidic?

Though acid rain can be caused naturally, humans are the main reason behind it. Our activities release enormous quantities of pollutants such as sulfur dioxide and nitrogen oxides in the air. The rain formed by these compounds is too acidic for it to be neutralized naturally.

What are the human sources that release dangerous quantities of pollutants?

There are enumerable ways by which humans have become causative agents of acid precipitation. Generation of electricity using fossil fuels like coal, for instance, emits the majority of sulfur dioxide and a quarter of nitrogen oxides present in the atmosphere. Factories, industries and refineries that use fossil fuels for combustion are also to blame. Vehicles like cars, buses and trucks are responsible for over half of nitrogen oxides present in the air.

Do water bodies get affected by acid rain?

The short answer is yes, they do. The adverse effects of acid rain are seen clearly in aquatic habitats such as lakes, ponds or rivers. Organisms in these water bodies survive within a specific pH range. When acidic rainwater drains into these water bodies, their pH levels reduce and they become more acidic. What does this mean for aquatic organisms?  

Some organisms may tolerate lower pH levels; some may not. But the more acidic these water bodies get, the greater is the imbalance in various food chains as certain animals start disappearing. Moreover, if acidity levels rise, fish eggs will not be able to hatch and populations of species may plummet dangerously.

Aquatic plants also suffer due to acidic habitats. Unable to withstand declining pH levels, many of these plants succumb to acid rain. 

Acid rain is one of the many consequences of rising pollution in the cities of India. Humans are harmed by it on the one hand. On the other hand, unfortunately, various other members of the environment have to suffer because of us. Recognizing this, the government has taken several measures to curb emissions. Yet, a promising future cannot be seen if each of us doesn’t start correcting fallacious actions and working towards a better environment.

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