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Water, soil and noise pollution

తెలుగులో వివరణ

Pollution · Part 2 / 3 · Fact-checked on 8 November 2026 · how we check

Written with AI from the sources listed at the bottom of this page, then fact-checked by a separate AI.

Point and non-point sources; dissolved oxygen, BOD and COD; eutrophication; mercury, cadmium and lead; arsenic, fluoride and nitrate in groundwater; sewage treatment, the Ganga Action Plan and Namami Gange; bioremediation and phytoremediation; soil pollution, bioaccumulation and biomagnification; the Noise Rules, 2000; thermal, radioactive and light pollution and oil spills.

Each idea is explained first in Telugu (తెలుగు), ending with the English and Hindi exam terms, followed by the same point in exam English. UPSC Prelims is in English or Hindi, so understand it in Telugu and revise it in English.

ఊహించండి, ఊరి చెరువులోకి ఒక ఫ్యాక్టరీ పైపు మురుగు వదులుతోంది. ఆ పైపు కనిపిస్తుంది, దాన్ని పట్టుకుని జరిమానా వేయొచ్చు; ఇదే బిందు మూలం. కానీ వర్షం పడ్డప్పుడు వేల పొలాల నుంచి ఎరువు, పురుగుమందు కొట్టుకొచ్చి చెరువులో కలిస్తే ఏ ఒక్క పైపునూ మూయలేం; ఇది బిందురహిత మూలం. దీన్ని ఆపాలంటే రైతులు, పట్టణాలు తమ అలవాట్లు మార్చుకోవాలి, అందుకే ఇది కష్టం. (→ English: water pollution; point source; non-point source · हिन्दी: जल प्रदूषण; बिंदु स्रोत; गैर-बिंदु स्रोत)

In exam EnglishThe first part of this chapter dealt with air; this second part turns to water, soil and noise. Water counts as polluted once its physical, chemical or biological make-up has been altered enough to hurt the people, crops or creatures that depend on it. A point source is a single outlet that can be identified, such as a factory's effluent pipe or a town's sewage drain emptying into a river; because the outlet is known, it can be monitored, given consent conditions and penalised. A non-point source is spread out: rain washing fertiliser and pesticide off thousands of fields, or oil and litter off city streets. There is no single pipe to block, so control depends on changing what people do on the land, which makes non-point pollution the harder problem.

నీటిని మూడు కొలతలతో పరీక్షిస్తారు. కరిగిన ఆక్సిజన్ అంటే నీటిలో చేపలు పీల్చే గాలి. జీవరసాయన ఆక్సిజన్ డిమాండ్ అంటే మురుగులోని చెత్తను బ్యాక్టీరియా తింటూ ఎంత ఆక్సిజన్ వాడుకుంటుందో; చెత్త ఎక్కువైతే ఇది పెరుగుతుంది, చేపలకు మిగిలే ఆక్సిజన్ తగ్గుతుంది. ఇంట్లో అతిథులు ఎక్కువైతే అన్నం త్వరగా అయిపోయినట్టు. రసాయన ఆక్సిజన్ డిమాండ్ బలమైన రసాయనంతో అన్నిటినీ కాల్చి కొలుస్తుంది, బ్యాక్టీరియా తినలేనివాటితో సహా; అందుకే అది ఎప్పుడూ ఎక్కువే. (→ English: dissolved oxygen (DO); biochemical oxygen demand (BOD); chemical oxygen demand (COD) · हिन्दी: घुलित ऑक्सीजन; जैव-रासायनिक ऑक्सीजन माँग; रासायनिक ऑक्सीजन माँग)

In exam EnglishThree measurements tell how polluted water is. dissolved oxygen (DO) is the oxygen held in the water, which fish and other aquatic life breathe; it falls as water warms and as microbes consume it. biochemical oxygen demand (BOD) is the amount of oxygen that bacteria use up while breaking down the organic matter in a sample, usually measured over five days at 20°C. Organic waste such as sewage raises BOD and pulls DO down, so a high BOD signals heavy organic pollution. chemical oxygen demand (COD) measures the oxygen needed to oxidise the matter in the sample chemically, with a strong oxidising agent, so it also counts substances that bacteria cannot digest. For the same sample COD is normally higher than BOD. The Central Pollution Control Board's criteria for outdoor bathing water ask for DO of at least 5 mg/l and BOD of no more than 3 mg/l.

The three oxygen measures of water quality
Measure	What it measures	Polluted water shows	Test
DO	Oxygen present in the water	Low value	Direct reading
BOD	Oxygen used by microbes to decompose organic matter	High value	Five days at 20°C
COD	Oxygen needed to oxidise matter chemically, including what microbes cannot digest	High value; normally above BOD	A few hours

చెరువులో ఎరువు, మురుగు ఎక్కువగా కలిస్తే అదే పోషకాధిక్యత. మొదట నాచు ఒక్కసారిగా పెరిగి నీరు ఆకుపచ్చగా మారుతుంది, కింది మొక్కలకు వెలుతురు అందదు. నాచు చనిపోయాక దాన్ని బ్యాక్టీరియా కుళ్ళబెడుతూ నీటిలోని ఆక్సిజన్ అంతా వాడేస్తుంది, చేపలు ఊపిరాడక తేలతాయి. ఎక్కువ తిండి పెట్టిన మొక్క కుండీలో కుళ్ళిపోయినట్టు. గుర్రపుడెక్క చెరువులను కప్పేసేది కూడా ఇలాంటి నీటిలోనే. (→ English: eutrophication; algal bloom; dead zone · हिन्दी: सुपोषण; शैवाल प्रस्फुटन; मृत क्षेत्र)

In exam Englisheutrophication is the over-enrichment of a lake, pond or slow-moving river with nutrients, chiefly nitrogen and phosphorus. Every lake slowly gathers nutrients and ages over centuries; human activity speeds this up enormously through fertiliser runoff, untreated sewage and phosphate detergents, and this faster version is called cultural eutrophication. Extra nutrients feed a sudden growth of algae, an algal bloom, which turns the water green and shades out the plants below. When the algae die, bacteria decompose them and use up the dissolved oxygen; BOD rises, DO crashes and fish suffocate. Some blooms of blue-green algae (cyanobacteria) also release toxins. Stretches of coastal sea left with too little oxygen for most life are called dead zones. The floating mats of water hyacinth that choke many Indian lakes thrive in the same nutrient-rich water.

భారీ లోహాలు కుళ్ళవు, శరీరంలో పోగవుతూనే ఉంటాయి. జపాన్‌లోని మినమాటాలో ఫ్యాక్టరీ పాదరసాన్ని సముద్రంలో వదిలింది; అది చేపల్లో పేరుకుంది, ఆ చేపలు తిన్నవాళ్ళ నరాలు దెబ్బతిన్నాయి. అదే మినమాటా వ్యాధి. ఇటాయ్-ఇటాయ్ అంటే 'నొప్పి, నొప్పి'; గనుల కాడ్మియం వరి పొలాల్లో చేరి ఎముకలు పెళుసుగా మారాయి. గుర్తుంచుకోండి: మినమాటా అంటే పాదరసం, ఇటాయ్-ఇటాయ్ అంటే కాడ్మియం. సీసం పిల్లల మెదడుకు హాని. (→ English: heavy metals; Minamata disease (mercury); itai-itai disease (cadmium); lead · हिन्दी: भारी धातुएँ; मिनामाता रोग (पारा); इताई-इताई रोग (कैडमियम); सीसा)

In exam EnglishHeavy metals are dangerous because they do not break down and they build up in living tissue. The best-known disaster is Minamata disease. From the 1930s a chemical factory at Minamata in Japan let mercury waste flow into the bay, where it was turned into methylmercury and concentrated in fish; people who ate the fish suffered nerve damage, numbness and birth defects, and the disease was officially identified in 1956. The Minamata Convention on Mercury, adopted in 2013 and in force from 2017, is named after the town. Itai-itai disease, also from Japan (the name means 'it hurts, it hurts'), was caused by cadmium from mining that polluted the rice fields of the Jinzu river basin; it left bones brittle and painful and damaged the kidneys. Lead harms the brain and nerves, above all in children, which is one reason leaded petrol was phased out.

ఈ విషం ఫ్యాక్టరీ నుంచి కాదు, భూమి లోపలి నుంచే వస్తుంది. గంగా మైదానపు మట్టిలో సహజంగా ఉన్న ఆర్సెనిక్‌ను బోర్లతో ఎక్కువగా తోడితే బావుల్లోకి వస్తుంది. నల్గొండ లాంటి ప్రాంతాల్లో రాళ్ళ నుంచి ఫ్లోరైడ్ నీటిలో కలుస్తుంది; కొంచెం అయితే పళ్ళకు మంచిది, ఎక్కువైతే ఫ్లోరోసిస్: పళ్ళపై మచ్చలు, తర్వాత ఎముకలు వంకర. ఉప్పు కొంచెం రుచి, ఎక్కువైతే రోగం అన్నట్టు. ఎరువుల నైట్రేట్ పసిపిల్లలకు 'బ్లూ బేబీ' సమస్య తెస్తుంది. (→ English: arsenic; fluoride; fluorosis; nitrate; blue baby syndrome · हिन्दी: आर्सेनिक; फ़्लोराइड; फ्लोरोसिस; नाइट्रेट; ब्लू बेबी सिंड्रोम)

In exam EnglishSome of India's worst water pollution cannot be seen and comes from the ground itself. Arsenic occurs naturally in the young sediments of the Ganga-Brahmaputra plains, and heavy pumping of groundwater draws it into wells in states such as West Bengal, Bihar, Uttar Pradesh and Assam; years of drinking it cause skin lesions and cancers. Fluoride comes from fluoride-bearing rocks in drier regions such as Rajasthan, Gujarat and parts of Telangana and Andhra Pradesh. A little protects teeth, but too much causes fluorosis: mottled teeth first, then stiff and deformed bones. Surplus fluoride can be settled out of water by dosing it with alum and lime, a method worked out by the National Environmental Engineering Research Institute (NEERI) and known as the Nalgonda technique. Nitrate, mostly from fertilisers and sewage, seeps into groundwater and can cause 'blue baby syndrome' (methaemoglobinaemia) in infants. The Bureau of Indian Standards' drinking water standard, IS 10500:2012, sets limits of 0.01 mg/l for arsenic, 1.0 mg/l for fluoride (1.5 mg/l where no other source exists) and 45 mg/l for nitrate.

Toxic contaminants of water and what they cause
Contaminant	Main source	Effect	Known case or area
Mercury	Industrial waste	Nerve damage, birth defects	Minamata disease, Japan
Cadmium	Mining waste	Brittle, painful bones; kidney damage	Itai-itai disease, Japan
Lead	Leaded petrol (earlier), batteries	Harm to brain and nerves, mainly in children	Phase-out of leaded petrol
Arsenic	Natural sediments, drawn up by heavy pumping	Skin lesions, cancers	Ganga-Brahmaputra plains
Fluoride	Fluoride-bearing rocks	Dental and skeletal fluorosis	Rajasthan, Gujarat, parts of Telangana and Andhra Pradesh
Nitrate	Fertilisers, sewage	Blue baby syndrome in infants	Farming areas

నదుల్లో ఎక్కువ మురికి పట్టణాల మురుగే, కాబట్టి ముందు దాన్ని శుద్ధి చేయాలి. మురుగు శుద్ధి కేంద్రం బియ్యం కడిగినట్టు దశలవారీగా పనిచేస్తుంది: మొదట జల్లెడ పట్టి రాళ్ళు, చెత్త తీస్తారు; తర్వాత సూక్ష్మజీవులకు గాలి ఇచ్చి కరిగిన మురికిని తినిపిస్తారు; చివరిలో పోషకాలు తీసి క్రిములు చంపుతారు. గంగా శుద్ధి 1985 గంగా కార్యాచరణ ప్రణాళికతో మొదలైంది; ఇప్పుడు నమామి గంగే ఆ పని చేస్తోంది. (→ English: sewage treatment plant; primary, secondary and tertiary treatment; Ganga Action Plan; Namami Gange; National Mission for Clean Ganga · हिन्दी: सीवेज उपचार संयंत्र; प्राथमिक, द्वितीयक और तृतीयक उपचार; गंगा कार्य योजना; नमामि गंगे; राष्ट्रीय स्वच्छ गंगा मिशन)

In exam EnglishMost of the organic load in Indian rivers is untreated urban sewage, so treatment plants are the first line of defence. A sewage treatment plant works in stages. Primary treatment removes floating and settling solids by screening and sedimentation. Secondary treatment lets microbes consume the dissolved organic matter, often in aerated tanks (the activated sludge process), which cuts BOD sharply. Tertiary treatment adds further steps, such as removing nutrients and disinfecting, before the water is reused or released. River cleaning in India began with the Ganga Action Plan in 1985, which was widened in 1995 into the National River Conservation Plan for other rivers. The Ganga was declared a national river in 2008, and in 2015 the Union government approved Namami Gange, an integrated mission for the river. It is carried out by the National Mission for Clean Ganga, which works under the National Ganga Council chaired by the Prime Minister.

చెత్తను శుభ్రం చేయడానికి ప్రాణులనే పనిలో పెట్టొచ్చు. జీవ శుద్ధీకరణలో బ్యాక్టీరియా, శిలీంధ్రాలు కాలుష్యాన్ని తిని హానిలేని నీరు, కార్బన్ డయాక్సైడ్‌గా మారుస్తాయి; సముద్రంలో ఒలికిన నూనెపై నూనె తినే బ్యాక్టీరియా చల్లడం ఉదాహరణ. మొక్కల శుద్ధీకరణలో మొక్కలు మట్టిలోని లోహాలను వేళ్ళతో పీల్చుకుంటాయి, తర్వాత ఆ మొక్కలను కోసి జాగ్రత్తగా పారేస్తారు. స్పాంజ్ నీటిని పీల్చి, దాన్ని పిండేసినట్టు. చౌక, కానీ నెమ్మది. (→ English: bioremediation; phytoremediation · हिन्दी: जैव उपचार; पादप उपचार)

In exam EnglishLiving things can also be put to work cleaning up. bioremediation uses microbes, mainly bacteria and fungi, to break pollutants down into harmless substances such as carbon dioxide and water. Bacteria that digest oil, spread on spills and on oily sludge, are the usual example; Oilzapper, a microbial culture developed in India by The Energy and Resources Institute (TERI), is one such product. phytoremediation uses plants instead. Some plants draw metals or other toxins out of soil or water into their roots and leaves, and are then harvested and disposed of safely; others hold the pollutants in place or break them down. Both methods are cheap and gentle compared with digging up contaminated soil and burning it, but they are slow and work best where the contamination is moderate.

మట్టి తట్టుకోగలిగినదానికంటే వేగంగా విషాలు చేరితే అది కలుషితమవుతుంది: పురుగుమందులు, అతి ఎరువులు, గనుల లోహాలు, ప్లాస్టిక్. DDT లాంటి మందు కొవ్వులో దాక్కుంటుంది, బయటికి పోదు; అదే జీవ సంచయనం. ఆహార గొలుసులో పైకి వెళ్ళేకొద్దీ అది పెరుగుతుంది; అదే జీవ ఆవర్ధనం. పురుగు నుంచి చేప, చేప నుంచి గద్ద: ప్రతి మెట్టులో విషం ఎక్కువ, చిన్న అప్పు వడ్డీతో పెరిగినట్టు. అందుకే గద్దల గుడ్ల పెంకులు పలుచబడ్డాయి. (→ English: soil pollution; bioaccumulation; biomagnification; DDT; endosulfan · हिन्दी: मृदा प्रदूषण; जैव संचयन; जैव आवर्धन; DDT; एंडोसल्फ़ान)

In exam EnglishSoil is polluted when harmful substances build up faster than it can neutralise them. Farming is a major source: pesticides that linger in the ground, and fertilisers used in excess, which acidify the soil, upset its microbes and leach nitrate into groundwater. Industry and mining add heavy metals and toxic effluent, and plastic fragments persist for decades. The most harmful pesticides are persistent and dissolve in fat, as DDT does. They stay in an animal's fat instead of being excreted, which is bioaccumulation, and their concentration rises at each step up a food chain, which is biomagnification, so top predators carry the heaviest load; DDT thinned the eggshells of birds of prey. India now allows DDT only for limited public-health use against disease-carrying mosquitoes. In 2011 the Supreme Court ordered a nationwide ban on the production, use and sale of endosulfan, after illness was linked to its aerial spraying on cashew plantations in Kasaragod, Kerala.

శబ్దాన్ని డెసిబెల్‌లలో కొలుస్తారు. ఇది మామూలు స్కేలు కాదు: 10 పెరిగితే శక్తి పదింతలు. 70 నుంచి 80కి వెళ్ళడం అంటే ఒక్క మెట్టు కాదు, పది మెట్లు ఎక్కినట్టు. నిబంధనలు పగలు, రాత్రి వేర్వేరు పరిమితులు పెడతాయి; రాత్రి 10 తర్వాత బహిరంగ లౌడ్‌స్పీకర్ వద్దు. ఆస్పత్రి, బడి, కోర్టు చుట్టూ 100 మీటర్లు నిశ్శబ్ద మండలం; అక్కడ రోగి, విద్యార్థి, న్యాయమూర్తి ప్రశాంతంగా ఉండాలి కదా. (→ English: decibel (dB); Noise Pollution (Regulation and Control) Rules, 2000; silence zone · हिन्दी: डेसिबल; ध्वनि प्रदूषण (विनियमन और नियंत्रण) नियम, 2000; शांत क्षेत्र)

In exam EnglishNoise is unwanted sound, measured in decibels (dB). The scale is logarithmic: every rise of 10 dB means ten times the sound energy, so 80 dB is not slightly worse than 70 dB but ten times as intense. Long exposure to loud noise causes permanent hearing loss. A 1987 amendment brought noise within the Air Act's definition of an air pollutant, but the detailed rules are the Noise Pollution (Regulation and Control) Rules, 2000, made under the Environment (Protection) Act, 1986. They set ambient limits for four kinds of area, separately for day (6 a.m. to 10 p.m.) and night (10 p.m. to 6 a.m.). The ground within 100 metres or more of a hospital, an educational institution or a court is treated as a silence zone. Loudspeakers may not be used at night except in closed premises such as halls, though a state may allow them until midnight on up to fifteen festival days a year. In 2005 the Supreme Court upheld such limits, treating freedom from noise as part of the right to life under Article 21.

Ambient noise limits under the Noise Rules, 2000 (Leq, dB(A))
Area	Day (6 a.m. to 10 p.m.)	Night (10 p.m. to 6 a.m.)
Industrial	75	70
Commercial	65	55
Residential	55	45
Silence zone	50	40

ఇంకొన్ని రకాలు: ఉష్ణ కాలుష్యం అంటే విద్యుత్ కేంద్రాలు చల్లబరచిన వేడి నీటిని నదిలో వదలడం; వేడి నీటిలో ఆక్సిజన్ తక్కువ, అందుకే చేపలు చనిపోతాయి. రేడియోధార్మిక కాలుష్యం కణాలను, జన్యువులను దెబ్బతీస్తుంది. పట్టణాల అతి వెలుతురు రాత్రి జీవులను గందరగోళపరుస్తుంది; తాబేలు పిల్లలు సముద్రం బదులు రోడ్డు వైపు వెళ్తాయి. ఒలికిన నూనె సముద్ర పక్షుల రెక్కలను అతికిస్తుంది. (→ English: thermal pollution; radioactive pollution; light pollution; oil spill · हिन्दी: तापीय प्रदूषण; रेडियोधर्मी प्रदूषण; प्रकाश प्रदूषण; तेल रिसाव)

In exam EnglishA few other kinds of pollution complete the picture. thermal pollution is the release of heated water, mostly from the cooling systems of thermal and nuclear power stations and some industries; since warm water holds less oxygen, the stretch of river or coast that receives it can lose fish and other life. Radioactive pollution comes from nuclear accidents and from careless disposal of nuclear and medical waste; radiation damages cells and genes, as the accidents at Chernobyl (1986) and Fukushima (2011) showed. Light pollution, the excess artificial light of towns and cities, hides the night sky and confuses animals that are active at night; sea-turtle hatchlings, which head for the brightest horizon, can crawl inland instead of to the sea. Oil spills coat the water, cut off oxygen and light below and mat the feathers of seabirds; they are tackled with floating booms, skimmers, chemical dispersants and bioremediation.

మొత్తం మీద రెండు ప్రశ్నలు గుర్తుంచుకోండి. ఒకటి: ఈ చెత్త ఎంత ఆక్సిజన్ తింటుంది? మురుగు, ఎరువులు ఆక్సిజన్ లాగేసి చెరువును చంపుతాయి. రెండు: ఈ విషం ఎంత కాలం ఉంటుంది? లోహాలు, ఆర్సెనిక్, DDT కుళ్ళవు, శరీరాల్లో పోగవుతాయి. అదుపు మూలాన్ని బట్టి: పైపుకు శుద్ధి కేంద్రం, పొలాలకు అలవాటు మార్పు, శబ్దానికి సమయ పరిమితి. తర్వాతి భాగం ఇళ్ళు, ఆస్పత్రులు, పరిశ్రమల ఘన వ్యర్థాల గురించి. (→ English: oxygen demand; persistence; point and non-point sources; solid waste · हिन्दी: ऑक्सीजन माँग; स्थायित्व; बिंदु और गैर-बिंदु स्रोत; ठोस अपशिष्ट)

In exam EnglishTwo questions tie this part together. How much oxygen does a pollutant use up? Sewage and nutrients raise BOD, lower DO and, through eutrophication, can choke a lake. How long does it last? Metals, arsenic, fluoride and persistent pesticides do not break down, so they accumulate in bodies and magnify along food chains. Control follows the source: point sources through consents and treatment plants, non-point sources through changed practices on farms and in cities, and noise through zone limits and time rules. The third part turns to solid waste and the rules that decide who must handle each kind.

Exam traps

A high BOD means more organic pollution, not cleaner water; as BOD rises, DO falls.
For the same sample COD is normally higher than BOD, because the chemical test also counts matter that microbes cannot digest.
In eutrophication most fish die from lack of oxygen when bacteria decompose the dead algae; the algae's growth itself is fed by nitrogen and phosphorus, not by heavy metals.
Minamata disease is mercury; itai-itai disease is cadmium. Both cases are from Japan; do not swap the metals.
Arsenic in the groundwater of the Ganga-Brahmaputra plains is mainly natural (geogenic), brought up by heavy pumping, not mainly industrial.
Blue baby syndrome is caused by nitrate, not by fluoride or arsenic; fluorosis is caused by fluoride.
The Noise Rules, 2000 were made under the Environment (Protection) Act, 1986, even though a 1987 amendment also brought noise into the Air Act's definition of an air pollutant.
Hospitals, educational institutions and courts each carry a surrounding silence zone of no less than 100 metres, whose limits (50 dB by day, 40 dB by night) are the strictest of the four kinds of area.

Recap

Point source: one identifiable outlet (effluent pipe, sewage drain); non-point source: diffuse runoff from farms and streets, harder to control.
DO is oxygen in water; BOD is oxygen used by microbes (five days, 20°C); COD is oxygen for chemical oxidation and is normally above BOD.
CPCB bathing-water criteria: DO at least 5 mg/l, BOD at most 3 mg/l.
Eutrophication: nitrogen and phosphorus feed an algal bloom; decomposing algae use up oxygen; fish die; dead zones form.
Minamata (mercury, identified 1956; convention 2013, in force 2017); itai-itai (cadmium); lead harms children's nerves.
Arsenic (Ganga-Brahmaputra plains, natural), fluoride (fluorosis; Nalgonda technique), nitrate (blue baby syndrome); IS 10500:2012 limits 0.01, 1.0 and 45 mg/l.
Sewage treatment: primary (solids), secondary (microbes, cuts BOD), tertiary (nutrients, disinfection); Ganga Action Plan 1985, NRCP 1995, Namami Gange 2015 run by NMCG.
Bioremediation uses microbes (Oilzapper); phytoremediation uses plants; persistent chemicals bioaccumulate and biomagnify (DDT); endosulfan banned by the Supreme Court in 2011.
Noise Rules 2000 under the EPA: four areas, day 6 a.m.-10 p.m., night 10 p.m.-6 a.m.; silence zone 100 m; no loudspeakers at night outside closed premises.
Thermal pollution lowers oxygen; radioactive pollution damages cells and genes; light pollution misleads turtle hatchlings; oil spills are fought with booms, skimmers and microbes.

Practice questions

Q1. Which one of the following combinations in a river sample points to heavy organic pollution from sewage?

High dissolved oxygen and low BOD
Low dissolved oxygen and high BOD
High dissolved oxygen and high BOD
Low dissolved oxygen and low COD

Show answer

Answer: B. Low dissolved oxygen and high BOD

Sewage is rich in organic matter, so microbes use a lot of oxygen (high BOD) and leave little in the water (low DO). High DO with low BOD describes clean water; high DO and high BOD rarely go together because heavy microbial demand pulls DO down; and organic pollution would raise COD, not keep it low.

Q2. Consider the following statements:
1. For the same water sample, chemical oxygen demand is usually lower than biochemical oxygen demand.
2. Biochemical oxygen demand is commonly measured as the oxygen used by microbes over five days at 20°C.
Which of the statements given above is/are correct?

1 only
2 only
Both 1 and 2
Neither 1 nor 2

Show answer

Answer: B. 2 only

Statement 1 is wrong: COD counts everything that can be oxidised chemically, including matter microbes cannot digest, so it is usually higher than BOD; this rules out options 1 and 3. Statement 2 is correct, so option 4 is wrong.

Q3. Consider the following pairs:
Disease : Cause
1. Minamata disease : Cadmium
2. Itai-itai disease : Cadmium
3. Blue baby syndrome : Nitrate
Which of the pairs given above are correctly matched?

1 and 2 only
2 and 3 only
1 and 3 only
1, 2 and 3

Show answer

Answer: B. 2 and 3 only

Pair 1 is wrong because Minamata disease was caused by mercury (methylmercury in fish), so options 1, 3 and 4, which include pair 1, are wrong. Pair 2 (cadmium) and pair 3 (nitrate) are correct.

Q4. Consider the following statements about eutrophication:
1. It is driven mainly by excess nitrogen and phosphorus entering a water body.
2. It raises the dissolved oxygen of the water body over time, because algae release oxygen.
Which of the statements given above is/are correct?

1 only
2 only
Both 1 and 2
Neither 1 nor 2

Show answer

Answer: A. 1 only

Statement 1 is correct, so option 4 is wrong. Statement 2 is wrong: when the algae die, bacteria decomposing them use up the dissolved oxygen, so oxygen falls and fish die; options 2 and 3, which accept statement 2, are wrong.

Q5. The arsenic found in the groundwater of the Ganga-Brahmaputra plains comes mainly from:

effluents of chemical industries
natural sediments, drawn into wells by heavy pumping
arsenic-based pesticides sprayed on rice
fly ash from thermal power stations

Show answer

Answer: B. natural sediments, drawn into wells by heavy pumping

The arsenic is geogenic: it sits naturally in the young sediments and is mobilised when groundwater is pumped heavily. Industrial effluent, pesticides and fly ash can add local contamination but are not the main cause of this regional problem, so options 1, 3 and 4 are wrong.

Q6. Consider the following statements about the Noise Pollution (Regulation and Control) Rules, 2000:
1. They were made under the Environment (Protection) Act, 1986.
2. Night time under the Rules runs from 10 p.m. to 6 a.m.
3. The noise limits for a silence zone are higher than those for a residential area.
Which of the statements given above are correct?

1 and 2 only
2 and 3 only
1 and 3 only
1, 2 and 3

Show answer

Answer: A. 1 and 2 only

Statements 1 and 2 are correct. Statement 3 is wrong: silence zones have the strictest limits (50 dB by day, 40 dB by night, against 55 and 45 for residential areas), so options 2, 3 and 4, which include statement 3, are wrong.

Q7. Growing plants that draw heavy metals out of contaminated soil into their roots and leaves, and then harvesting them, is an example of:

biomagnification
phytoremediation
eutrophication
thermal pollution

Show answer

Answer: B. phytoremediation

Using plants to remove or hold pollutants is phytoremediation. Biomagnification is the rise of a persistent chemical's concentration up a food chain, eutrophication is nutrient over-enrichment of water, and thermal pollution is the release of heated water; none of them is a clean-up method.

Q8. Consider the following statements:
1. The Ganga Action Plan was launched in 1985.
2. Namami Gange is carried out by the National Mission for Clean Ganga.
3. The National Ganga Council is chaired by the Union Minister of Jal Shakti.
Which of the statements given above are correct?

1 and 2 only
2 and 3 only
1 and 3 only
1, 2 and 3

Show answer

Answer: A. 1 and 2 only

Statements 1 and 2 are correct. Statement 3 is wrong because the National Ganga Council is chaired by the Prime Minister, so options 2, 3 and 4, which include statement 3, are wrong.

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Sources

Central Pollution Control Board: Primary Water Quality Criteria for designated best uses (outdoor bathing: DO 5 mg/l or more, BOD 3 mg/l or less); water quality monitoring of rivers — https://cpcb.nic.in
The Water (Prevention and Control of Pollution) Act, 1974 (consent for discharge of effluent) — https://www.indiacode.nic.in
United States Environmental Protection Agency: nutrient pollution and eutrophication; biochemical and chemical oxygen demand; thermal discharges; oil spill response; remediation technologies — https://www.epa.gov
Minamata Convention on Mercury (adopted 10 October 2013, in force 16 August 2017), UNEP secretariat — https://www.mercuryconvention.org
World Health Organization fact sheets: mercury and health; lead poisoning; arsenic; cadmium (itai-itai disease) — https://www.who.int
Bureau of Indian Standards: IS 10500:2012, Drinking Water: Specification (arsenic 0.01 mg/l; fluoride 1.0 mg/l, 1.5 mg/l in the absence of an alternate source; nitrate 45 mg/l) — https://www.bis.gov.in
Central Ground Water Board: groundwater quality reports (arsenic, fluoride and nitrate affected areas); NEERI's Nalgonda technique for defluoridation — https://cgwb.gov.in
National Mission for Clean Ganga, Ministry of Jal Shakti: Namami Gange (approved May 2015); Ganga Action Plan (1985) and National River Conservation Plan; River Ganga (Rejuvenation, Protection and Management) Authorities Order, 2016 — https://nmcg.nic.in
Press Information Bureau: bioremediation of oil spills and oily sludge with TERI's Oilzapper — https://pib.gov.in
Supreme Court of India: Democratic Youth Federation of India v. Union of India, interim order of 13 May 2011 banning the production, use and sale of endosulfan — https://main.sci.gov.in
The Noise Pollution (Regulation and Control) Rules, 2000, with Schedule of ambient noise standards; the Environment (Protection) Act, 1986; the Air (Prevention and Control of Pollution) Act, 1981, section 2(a) as amended in 1987 — https://www.indiacode.nic.in
Supreme Court of India: In re Noise Pollution (Implementation of the Laws for Restricting Use of Loudspeakers and High Volume Producing Sound Systems), judgment of 18 July 2005 — https://main.sci.gov.in