1. Nutrients leaching from agricultural land into water courses, can lead to algal blooms and eutrophication. An algal bloom is a rapid increase or accumulation in the population of algae (typically microscopic) in an aquatic system. Eutrophication is the ecosystem response to the addition of artificial or natural substances, such as nitrates and phosphates, through fertilizers or sewage to an aquatic system.
   1. The Nationwide Urban Runoff Program (NURP) is a research project conducted by the US Environmental Protection Agency (EPA) between 1979 and 1983. It was the first comprehensive study of urban stormwater pollution across the United States.

1. Alpha partices lack penetration power but they have more energy than beta. Alpha particles cannot penetrate the skin to reach the internal organs whereas beta particles can damage internal organs.
   1. Radioactive iodine - 131 accumulates in thyroid gland and causes cancer. The cancer occurs from residual tissue radiation damage caused by the I¹³¹, and usually appear years after exposure, long after the I¹³¹ has decayed.

1. A spill or ongoing releases of chemical or radionuclide contaminants into soil (located away from a surface water body) may not create point source or non-point source pollution, but can contaminate the aquifer below, defined as a toxin plume. A radionuclide is an atom with an unstable nucleus, characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or via internal conversion.
   1. Pollutants released to the ground can work their way down into the groundwater. The resulting body of polluted water within an aquifer is called a plume, with its migrating edges called plume fronts. Plumes are used to locate, map, and measure water pollution within the aquifer's total body of water, and plume fronts to determine directions and speed of the contamination's spreading in it.

1. An electrical conductivity meter is used to measure total dissolved solids.
   1. A gas chromatograph-mass spectrometer measures pesticides and other organic pollutants.
   2. A rosette sampler is used to collect samples in deep water, such as the Great Lakes or oceans, for water quality testing. Probably, the most commonly user water sampler is rosette.

1. Stockholm Convention on Persistent Organic Pollutants is an international environmental treaty, signed in 2001 and effective from May 2004, that aims to eliminate or restrict the production and use of persistent organic pollutants (POPs).
   1. Endosulfan is an off-patent organochlorine insecticide and acaricide that is being phased out globally and is acutely neurotoxic to both insects and mammals, including humans.
   2. Endosulfan, although classified as a yellow label pesticide by the Central Insecticides Board, is highly produced and consumed.

1. The EPA began regulating greenhouse gases (GHGs) from mobile and stationary sources of air pollution under the Clean Air Act (CAA) for the first time on January 2, 2011.
   1. Statement 2 is incorrect. The Montreal Protocol on Substances that Deplete the Ozone Layer (a protocol to the Vienna Convention for the Protection of the Ozone Layer) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances believed to be responsible for ozone depletion. The use of CFCs was banned.

Toxicity labels; red label, yellow label, blue label and green label are mandatory labels employed on pesticide containers in India, identifying the level of toxicity of the contained pesticide as extremely toxic (poison), highly toxic (poison), moderately toxic (danger) and slightly toxic (caution) respectively.

1. The sievert (symbol: Sv) is the International System of Units (SI) derived unit of equivalent radiation dose, effective dose and committed dose. Quantities that are measured in sieverts are designed to represent the stochastic biological effects of ionizing radiation. The gray and sievert units are both special names for the SI derived units of joules per kilogram (m²/s² if expressed in base units), though they are not interchangeable. 1. Sv = 1 J/kg = 1 Gy
   1. Dissolved Oxygen (Oxygen saturation): It is a relative measure of the amount of oxygen dissolved in water. Super saturation (excess of oxygen) can be harmful to organisms and also cause decompression sickness. It is expressed in mg/l.

1. Ethanol is a biofuel and can be easily produced from carbohydrate rich substances like sugarcane, corn and sorghum. It burns clean and non polluting. However, as compared to petrol its calorific value is less and therefore, produces much less heat than petrol.
   1. Ethanol is considered to be an excellent substitute for kerosene and its combustion is as clean as LPG.

1. The SPI (Society of the Plastics Industry) resin identification coding system is a set of symbols placed on plastics to identify the polymer type. The primary purpose of the codes is to allow efficient separation of different polymer types for recycling. Separation must be efficient because the plastics must be recycled separately.
   1. White pollution is improper disposal of rubbish such as food containers and wrapping paper along railway stations, rivers and any other corner of city streets. This term has been coined to describe the local and global effects of discarded plastic bags upon the environment.

Option 4 is incorrect. All the above statements are correct.

1. Polyvinyl chloride, commonly abbreviated PVC, is the third-most widely produced plastic, after polyethylene and polypropylene. PVC is commonly used as the insulation on electrical cables; PVC used for this purpose needs to be plasticized.
   1. Most plastics are made from petroleum (oil or natural gas). First, refineries process the crude oil to produce fuels, such as gasoline, and many petrochemicals. Petrochemicals then are used by chemical plants to obtain many products, like fertilizers, lubricants, and plastic resins. Plastic resins are, in turn, used to produce many different types of plastics.

1. High-density polyethylene (HDPE) is a polyethylene thermoplastic made from petroleum,  Known for its large strength to density ratio, HDPE is commonly used in the production of plastic bottles.
   1. Cross-linked polyethylene, commonly abbreviated PEX or XLPE, is a form of polyethylene with cross-links. It is formed into tubing and is used predominantly in building pipework and services, domestic water piping, and insulation for high tension (high voltage) electrical cables.
   2. Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. Its most common use is in plastic bags.
   3. Medium-density polyethylene (MDPE) is a type of polyethylene, which is less dense than HDPE. Stress cracking resistance is better than that of HDPE. MDPE is typically used in sacks, shrink film, packaging film etc.

1. The nuclear fuels uranium-235 and plutonium-239 are the materials from which nuclear weapons are made.
   1. Radioactive radon gas is a colourless gas produced from the decay of uranium.

Methane is produced when bacteria break down the organic matter in moist places that lack oxygen, such as swamps, natural wetlands, paddy fields, landfills and digestive tracts of cattle, sheep and termites.