Environmental Pollution

On December 3, 1984, the Bhopal gas tragedy occurred as a consequence of the reaction between methyl isocyanate and water within a cooling tank. This reaction generated heat, leading to a rise in pressure that ultimately caused the rupture of the safety valve, resulting in the release of toxic gas.

In desert ecosystems, there is limited vegetation, and the soil consists of sandy terrain. The absence of plant cover means that the soil is exposed to the atmosphere. During the daytime, the sand heats up quickly when exposed to sunlight, and at night, after sunset, it cools down rapidly, releasing heat rapidly. As a result, the daily temperature fluctuations at the surface of the soil are quite extreme in desert regions. This significant temperature variation is one of the factors contributing to the lack of abundant plant life and animal populations in desert environments.

Physico-chemical indicators: These are conventional parameters commonly associated with water quality assessment. They encompass measurements such as dissolved oxygen levels, pH, temperature, salinity, and the concentration of nutrients like nitrogen and phosphorus. Physico-chemical indicators also include assessments of pollutants like insecticides, herbicides, and heavy metals. Biological indicators: Biological indicators offer a direct evaluation of the overall health of aquatic ecosystems by examining the condition of the resident plants and animals. In freshwater environments, these indicators involve assessing factors like the diversity of macroinvertebrates or fish, the growth of benthic algae, and the oxygen demand in benthic communities. Flow indicators: In freshwater systems, changes in water flow often play a pivotal role in the degradation of aquatic ecosystem health. For instance, the Murray-Darling system is a notable example of this phenomenon. Evaluating alterations in natural flow patterns caused by human activities is crucial. These changes can encompass modifications in peak flows, base flows, the absence of flow during certain periods, and alterations in seasonal flow patterns.

Lead, a prominent heavy metal pollutant, is predominantly discharged into the environment through vehicle emissions. It lingers in the atmosphere and subsequently settles during rainfall. Lead can enter the human body when ingested via water or inhaled as suspended particles. When the concentration of lead in the bloodstream reaches 30μg/100ml, it is deemed toxic, as it has the potential to induce conditions like aplastic anemia, tumors, and cancer.Therefore, the accurate answer is '30μg/100ml.'

The correct option is (B): 1981.