Earth as a System: Energy, Matter, and Life (Earth ek System ke roop mein: Energy, Matter aur Life): Class 9 Science Chapter 13 Hinglish mein

May mein north India ke plains tez Sun mein tapte hain. Yahi garmi kuch hafton baad samundar se nami wali hawaayein andar kheenchne mein madad karti hai, aur monsoon aa jaata hai. Baarish rivers ko bhar deti hai, rivers taaza mitti coast tak le jaati hain, aur coast ke paas ki machhliyan wahi khaati hain jo rivers laati hain. In mein se koi bhi ghatna akeli nahi hai. Har ek ek chain ki kadi hai jo hawa, paani, rock, ice aur living things se hokar guzarti hai.

Earth ek system ke roop mein

Is chain ko chalaane wali lagbhag saari energy Sun deta hai. Do chhote sources bhi isme jodte hain. Ek hai planet ke bahut andar se upar risti garmi. Doosra hai woh energy jo hawa, paani aur rock mein substances ke aapas mein react karne par nikalti hai. Middle school mein tumne winds, water cycle, seasons, nutrient cycles aur pollution ko alag-alag topics ki tarah padha tha. Yeh chapter unhe jodta hai. Scientists hamare planet ko ek Earth system ki tarah dekhte hain, jo paanch jude hue hisson se bana hai jinhe spheres kehte hain.

• Geosphere (भूमंडल) solid Earth hai: rocks, soil, pahad aur plains, neeche garam interior tak. Maharashtra ki black cotton soil aur purani, ghisi hui Aravalli pahadiyan, dono isi ka hissa hain.
• Hydrosphere saara liquid paani hai: samundar, Narmada jaisi rivers, Chilika jaisi lakes, aur woh groundwater jo gaon ka handpump upar kheenchta hai.
• Cryosphere jama hua paani hai: Gangotri jaise glaciers, Pir Panjal range par sardiyon ki snow, sea ice aur polar ice caps.
• Atmosphere planet ke chaaron taraf lipti hawa ki layer hai, Kerala ke upar ki nami wali monsoon hawa se lekar Spiti ke upar ki patli, sookhi hawa tak.
• Biosphere har living thing aur uske rehne ki jagah hai: Sundarbans ke mangroves, Punjab ka gehun ka khet, Lakshadweep ke paas coral reefs, aur Bay of Bengal mein tairte plankton.

Spheres band dabbe nahi hain. Girti hui baarish ki boond atmosphere ka hissa hai. Stream tak pahunchte hi woh hydrosphere ka hissa ban jaati hai, aur jab koi tree use pee leta hai, to biosphere ka. Fig. 13.1 mein tum ek hi landscape mein har sphere ko pehchaan sakte ho.

Ab ise poore subcontinent ke scale par socho. Monsoon apni bahut si nami Arabian Sea se leta hai, isliye climate scientists uske surface temperature par kadi nazar rakhte hain. Garam samundar hawa mein zyada water vapour bhejta hai, aur baarish ka andaaza lagana mushkil ho jaata hai: ek district ek hafte paani mein doob sakta hai aur agle hafte sookha pad sakta hai. Badhta hawa ka temperature jame hue world tak bhi pahunchta hai. Jaise-jaise Himalayan glaciers aur polar ice sikudte hain, glacial lakes overflow ho sakti hain, aur oceans dheere-dheere upar uthkar neechi coastal towns ki taraf badhte hain. In mein se har change plants aur animals se unke habitats bhi chheen leta hai.

13.1 Earth ki Uneven Heating

Kya Earth ke har hisse ko Sun ki energy ka barabar hissa milta hai? June ki ek hi dopahar ko Chennai mein log 38 °C mein paseena-paseena hote hain, jabki Arctic Ocean par sea ice abhi bhi tair rahi hoti hai. Heating itni uneven kyun hai, yeh samajhne ke liye pehle humein jaanna hoga ki sunlight kya hai.

Sunlight electromagnetic (EM) radiation hai. EM waves energy le jaati hain aur unhe kisi medium ki zaroorat nahi hoti: woh Sun aur Earth ke beech ki lagbhag khaali space ko light ki speed, $3\times {10}^8\mathrm{m}\mathrm{/}\mathrm{s}$, se paar karti hain. Sound alag hai. Chapter 10 mein tumne dekha tha ki sound ek mechanical wave hai, isliye woh vacuum mein bilkul nahi chal sakti.

EM waves wavelengths ki ek bahut badi range mein hoti hain, jise electromagnetic spectrum kehte hain (Fig. 13.2). Wavelength jitni chhoti, frequency utni zyada aur har wave utni zyada energy le jaati hai. Gamma rays aur X-rays chhote end par hain; unmein itni energy hoti hai ki woh living cells ko nuksaan pahuncha sakti hain. Radio waves lambe end par hain.

Sun jo kuch bhi bhejta hai, usmein se sirf teen bands hi hum tak zyada energy laate hain: ultraviolet (UV), visible light aur infrared (IR). In teeno mein milkar sunlight ki karib 99 % energy hoti hai. Baaki planet ko garam karne ke liye mushkil se maayne rakhta hai: Sun ki gamma rays aur X-rays hamare sir ke bahut upar hi sokh li jaati hain, aur Sun ki microwaves aur radio waves bahut kamzor hain. Neeche aate hue yeh teen important bands bilkul alag kaam karte hain:

Asal mein kitni solar energy pahunchti hai? Do numbers iska jawaab dete hain. Socho ek solar panel atmosphere ke theek upar space mein rakha hai, aur seedha Sun ki taraf muda hai: uska har square metre karib 1.4 kilowatts pakdega. Yeh number solar constant hai. Jo solar energy aakhir mein Earth ki surface par, per square metre per second, pahunchti hai, use insolation (सूर्यातप) kehte hain.

Earth ke energy budget ki, aur isliye climate ki, har calculation solar constant se shuru hoti hai. Ise gate par pahunchi Sun ki poori delivery samjho. Zameen tak neeche aate hue air molecules, dhool aur clouds is load ka kuch hissa absorb ya scatter kar dete hain, isliye bina baadal wale din dopahar ko bhi surface par insolation zyada se zyada lagbhag $1\mathrm{k}\mathrm{W}\mathrm{/}{\mathrm{m}}^2$ tak hi pahunchta hai. India ka zyadatar hissa karib 8° N aur 37° N ke beech hai, aur desh ke zyadatar hisson ko har din per square metre 4 se 7 kWh solar energy milti hai (Ministry of New and Renewable Energy). Yahi dhoop zameen ko garam karti hai jisse monsoon shuru hota hai, fasalon ko pakaati hai aur saaf electricity ka ek bahut bada source deti hai.

Insolation ek power per area hai. Collect hui energy nikaalne ke liye ise Sun ki taraf mude area aur time se multiply karo:

13.1.1 Earth ki surface par solar radiation ka interaction

Dopahar ko safed marble ke farsh se nange pair kaale granite ki seedhi par jao, aur tumhare pairon ko turant farak pata chal jaata hai. May mein ek safed car aur ek kaali car ko saath-saath park karo, aur kaali car chhoone mein kahin zyada garam hoti hai. Grade 7 se tum jaante ho ki zameen aur paani alag-alag rate se garam hote hain; rang aur material bhi utne hi maayne rakhte hain. Halki, chamakdaar surfaces zyadatar sunlight wapas bhej deti hain, jabki gehri surfaces use sokh leti hain.

Scientists ise ek number dete hain. Kisi surface ka albedo aane wali sunlight ka woh fraction hai jo woh reflect karti hai (yeh word albus se aaya hai, jo Latin mein safed hai). Taazi snow, jiska albedo karib 0.85 hai, zyadatar light wapas phenk deti hai aur tez dhoop mein bhi thandi rehti hai. Taarkol wali sadak, karib 0.05, lagbhag saari light rakh leti hai aur tapne lagti hai.

Poori Earth ka albedo karib 0.3 hai. Fig. 13.3 mein atmosphere ke top par aane wali sunlight ke 100 units ko follow karo. Karib 30 units clouds, hawa, ice aur zameen seedha space mein wapas reflect kar dete hain. Karib 23 units hawa aur clouds absorb kar lete hain. Bache hue 47 units zameen aur samundar absorb karte hain, aur yahi surface ko garam karta hai.

Har garam cheez bhi garmi chhodti hai, invisible infrared ke roop mein. Sooraj dhalne ke ek ghante baad kisi river ghat ki pathar ki seedhiyon par baitho, aur tum ab bhi din ki garmi unse bahar aati mehsoos kar sakte ho. Eent aur concrete ki buildings bhi isi tarah garmi jama karti hain aur raat bhar chhodti hain, isiliye top floor ke flats andhera hone ke kaafi der baad tak ghutan bhare rehte hain. Moti mitti ki deewaron, chhappar ki chhat ya chhat par plants wale ghar garmi dheere lete hain aur zyada aaramdeh rehte hain.

13.1.2 Latitude aur Earth ka shape

Torch ko seedha neeche table par chamkao aur tumhe ek chhota, tez circle milta hai. Torch ko tirchha karo aur wahi light ek lambe, dhundhle oval mein phail jaati hai. Gol Earth par sunlight bhi aise hi behave karti hai (Fig. 13.5). Equator ke aas-paas dopahar ka Sun upar hota hai, isliye uski rays lagbhag seedhi neeche padti hain aur apni energy ek chhote area mein bhar deti hain. Poles ki taraf Sun kabhi upar nahi chadhta; uski rays kam tirchhe angle par aati hain aur wahi energy kahin bade area par phail jaati hai. Isliye tropics saal bhar garam rehte hain aur polar zameen barfeeli rehti hai. Equator aur poles ke beech heating ka yeh farak hi planet ki winds aur ocean currents ka engine hai (Section 13.2).

Earth ke axis ka tilt ek doosra effect jodta hai. Jaise-jaise Earth Sun ke chakkar lagati hai, woh latitude jahan dopahar ka Sun theek sir ke upar hota hai, karib $23.4\mathrm{°}$ N aur $23.4\mathrm{°}$ S ke beech khisakta hai. June mein yeh Tropic of Cancer ke paas sir ke upar hota hai, jo Gujarat, Madhya Pradesh aur West Bengal se hokar guzarti hai. Tab north India ko seedhi rays aur lambe din milte hain: garmi. December mein Sun kaafi south mein sir ke upar hota hai, uski rays India tak tirchhi pahunchti hain aur din chhote hote hain: sardi. Neeche wale simulation mein try karo.

13.1.3 Atmosphere ka role

Gravity Earth ke chaaron taraf hawa ki ek layer ko pakde rakhti hai: atmosphere. Sookhi hawa mein karib 78 % nitrogen aur 21 % oxygen hai. Argon lagbhag 1 % hai, aur carbon dioxide sirf karib 0.04 %. Water vapour May mein Thar ke upar lagbhag zero se lekar chipchipi monsoon hawa mein karib 4 % tak badalta hai.

Atmosphere layers mein bana hai, aur har layer alag tarah se behave karti hai (Fig. 13.7). Sabse neeche ki layer, troposphere (क्षोभमंडल), average mein karib 12 km moti hai: equator ke upar lagbhag 16–18 km, lekin poles ke upar sirf 8–10 km. Ise neeche se garam zameen garam karti hai, isliye upar jaate hue hawa thandi hoti jaati hai, har kilometre par karib 6.5 °C. Zameen ke paas ki garam, nami wali hawa upar uthti hai, thandi hoti hai aur clouds banati hai. Lagbhag saara weather, halki hawa se lekar cyclone tak, isi layer mein hota hai.

Karib 12 km se 50 km tak stratosphere hai, jismein ozone layer hai. Ozone Sun ki UV absorb karti hai, isliye yahan uchaai ke saath hawa garam hoti jaati hai. Thandi hawa ke upar baithi garam hawa upar nahi uthti, isliye stratosphere shaant aur stable rehta hai. Yeh ek dhakkan ki tarah kaam karta hai jo weather ko apne neeche rakhta hai. Lambi doori ke jets troposphere ke top ke paas ya uske theek upar udte hain, jahan safar zyada smooth hota hai. Aur upar mesosphere, thermosphere aur exosphere aate hain, jo dheere-dheere space mein mil jaata hai. Yeh oonchi layers surface ke climate par mushkil se asar daalti hain. Karib 100 km upar woh line hai jise aam taur par outer space ka kinara maana jaata hai.

Atmosphere ek saath do kaam karta hai, chhatri aur razaai ki tarah. Chhatri ke roop mein yeh aane wali sunlight ki dhaar kam karta hai: ozone zyadatar UV sokh leti hai, aur gases, dhool aur clouds zameen tak pahunchne se pehle sunlight ka karib ek-chauthaai absorb kar lete hain (Fig. 13.3). Razaai ke roop mein yeh garmi ke bahar nikalne ko dheema karta hai. Sunlight zameen ko garam karti hai, aur garam zameen upar ki taraf infrared radiate karti hai. Carbon dioxide, methane aur water vapour ke molecules us infrared ko absorb karte hain aur use phir har direction mein chhodte hain, kuch zameen ki taraf wapas bhi. Is tarah garmi ko rokne ko greenhouse effect (हरितगृह प्रभाव) kehte hain, jo Fig. 13.8 mein dikhaya gaya hai.

Is razaai ke bina Earth ka average surface temperature karib −18 °C hota aur oceans jam jaate; iske saath average karib 15 °C ka aaramdeh temperature hai. Zyada greenhouse gas jodna razaai ko mota karta hai. Coal, oil aur gas jalane se 1960 se ab tak hawa mein $\mathrm{C}\mathrm{O}{\phantom{X}}_2$ ki maatra karib ek-tihaai badh gayi hai, aur planet ab 1800s ke aakhir ke mukaable lagbhag 1.4–1.5 °C zyada garam hai (Table 13.5). Yeh extra heating global warming hai. Agar ise roka nahi gaya, to Earth ke bade hisson mein rehna bahut mushkil ho sakta hai.

Atmosphere kabhi shaant nahi rehta. Sunlight ke alawa us par Sun se aane wale charged particles ki dhaarayein aur deep space se aane wale tez particles, jinhe cosmic rays kehte hain, bhi takraate hain. Bahut upar yeh kuch layers ko electrically charged bana dete hain. Woh layers radio signals ko mod kar zameen par wapas bhejti hain, aur ek tez solar storm radio, GPS aur satellites mein gadbad kar sakta hai. Yeh saari layers milkar control karti hain ki energy planet mein kaise aati aur jaati hai, aur isse weather, climate aur life ko shape milta hai. Hamare jaane hue kisi aur planet ka atmosphere bilkul hamare jaisa nahi hai.

13.2 Uneven Heating se Wind aur Ocean Currents Chalte Hain

Hawa wahan se jahan pressure high hai, wahan jaati hai jahan pressure low hai, aur us movement ko hum wind ki tarah mehsoos karte hain. Pressure ka farak zyadatar uneven heating se aata hai. Zameen ke kisi garam hisse ke upar ki hawa phailti hai, halki hoti hai aur upar uthti hai, peeche low pressure chhod jaati hai. Thandi, ghani hawa neeche baithti hai aur pressure badhati hai. Din mein sea breeze aur raat mein land breeze ke liye tum yeh idea pehle hi use kar chuke ho. Yahi idea ek valley mein chalne wali winds aur poore planet ka chakkar lagane wali winds, dono ko samjhata hai.

13.2.1 Local winds

Kisi Himalayan valley mein ek saaf din bitao aur tum mehsoos karoge ki wind do baar direction badalti hai. Der subah tak ek breeze pahadi dhalaanon par upar ki taraf chalti hai; Himachal mein paragliders isi par udte hain. Andhera hone ke baad hawa ulti taraf behti hai aur dhalaanon se neeche utarti hai. Kyun? Dhoop wali dhalaanein gehri valley floor ke mukaable Sun ki taraf zyada seedhi mudi hoti hain, isliye mid-morning tak un par ki zameen, aur us par tiki hawa ki patli layer, valley ke beech mein usi height ki hawa se zyada garam hoti hai. Garam hawa kam ghani hoti hai, isliye woh dhalaan par upar sarakti hai aur valley ki hawa uske peeche kheench li jaati hai: ek valley breeze. Raat mein dhalaanein apni garmi khule aasmaan mein radiate kar deti hain. Unhe chhooti hawa thandi hoti hai, paas ki hawa se zyada ghani ho jaati hai, aur paani ki tarah neeche valley mein beh jaati hai: ek mountain breeze (Fig. 13.9).

Kyunki raat mein thandi hawa neeche beh jaati hai, isliye subah tak valley floor aksar sabse thandi jagah hoti hai, aur sardiyon mein frost aur fog sabse pehle wahin jamte hain. Himachal aur Kashmir ke pahadi kisaan yeh jaante hain: woh aksar seb ke baag valley floor ke bajaye dhalaanon par lagaate hain, jahan der se aaya spring frost phoolon ko maar sakta hai. Yeh roz ki breezes nami ko bhi valley mein upar-neeche le jaati hain, jisse yeh tay hota hai ki soil kitni jaldi sookhti hai aur garmiyon ki dopahar mein clouds kahan bante hain.

13.2.2 Planetary winds

Planet ke scale par bada temperature farak equator aur poles ke beech hai. Isse high aur low pressure ki chaudi belts banti hain jo Earth ka chakkar lagaati hain, aur unke beech lagaatar chalne wali winds planetary winds hain (Fig. 13.10).

• Equator par tez heating se garam, nami wali hawa upar uthti hai. Isse equatorial low-pressure belt banti hai, jahan aksar thunderstorms aate hain.
• Bahut upar, uthi hui hawa poles ki taraf phailti hai, thandi hoti hai aur karib 30° N aur 30° S par phir neeche baithti hai. Neeche baithti hawa surface par jama hokar subtropical high-pressure belts banati hai. Duniya ke kai bade deserts, Thar samet, inhi latitudes ke paas hain, kyunki neeche baithti hawa sookhi hoti hai.
• Subtropical highs se surface ki zyadatar hawa wapas equator ki taraf behti hai, aur ek loop poora hota hai. Uska kuch hissa ulti taraf, poles ki taraf, behta hai.
• Karib 60° N aur 60° S par poles ki taraf jaati yeh hawa polar regions ki bahut thandi hawa se milti hai aur upar dhakel di jaati hai, jisse subpolar low-pressure belts banti hain.
• Poles ke upar kadaake ki thandi, ghani hawa neeche baithti hai, aur polar highs banti hain. Wahan se hawa subpolar lows ki taraf behti hai, aur teesra loop poora hota hai.

Agar Earth na ghoomti, to yeh winds high pressure se low pressure ki taraf seedhi, longitude ki lines ke saath chalti. Lekin Earth rotate karti hai, aur chalti hawa mud jaati hai: Northern Hemisphere mein right ki taraf aur Southern Hemisphere mein left ki taraf. Isliye 30° N se equator ki taraf jaati hawa north-east se aati hai, north-east trade winds ke roop mein. 30° aur 60° ke beech poles ki taraf jaati hawa mudkar westerlies ban jaati hai, aur poles se nikalti hawa polar easterlies ban jaati hai. India mein northeast trade winds sardiyon ki sookhi winds hain; garmiyon mein monsoon unhe ulat deta hai.

13.2.3 Ocean currents

Oceans bhi chalte hain. Ocean current (महासागरीय धारा) samundar ke paani ke ek bahut bade hisse ka ek direction mein lagaatar behna hai. Ise kai cheezein chalati hain:

• Wind. Planetary winds samundar ke upar hazaaron kilometres tak chalti hain, aur friction surface ke paani ko apne saath kheench le jaata hai.
• Temperature. Equator par garam hua paani halka hota hai aur surface ke saath poles ki taraf phailta hai. Thanda polar paani zyada ghana hota hai; woh neeche baith jaata hai aur gehre ocean floor ke saath dheere-dheere equator ki taraf wapas sarakta hai.
• Salinity. Zyada namkeen paani kam namkeen paani se zyada ghana hota hai. Bahut namkeen paani neeche baith jaata hai; rivers ya pighalti ice se meetha hua paani upar ke paas rehta hai.
• Earth ka spin chalte paani ko waise hi modta hai jaise wind ko, aur continents currents ko rokte hain aur unhe side mein mod dete hain.

Winds aur spin milkar har ocean basin ke surface paani ko ek bahut bade loop mein ghumate hain, jise gyre kehte hain. Gyres Northern Hemisphere mein clockwise aur Southern Hemisphere mein anticlockwise ghoomte hain (Fig. 13.11).

Ek paheli suno. Norway ka Hammerfest karib 71° N par, Arctic Circle ke andar hai, phir bhi uska harbour poori sardi khula rehta hai. Canada ki Hudson Bay par Churchill kaafi south mein, karib 59° N par hai, lekin uska port aadhe saal se zyada ice mein band rehta hai. Farak ek ocean current ka hai. Gulf Stream Gulf of Mexico se garam paani North Atlantic ke paar le jaati hai, aur uska extension, North Atlantic Drift, Norway ke coast ko garam paani se nehlata hai. Poori duniya mein currents heat ke liye conveyor belt ki tarah kaam karte hain: garam paani poles ki taraf behta hai aur thanda paani wapas aata hai, jisse tropics aur poles ke beech temperature ka farak kam hota hai.

Currents samundar ko khaana bhi dete hain. Jahan winds surface ke paani ko coast se door dhakelti hain, wahan neeche se thanda paani upar aata hai aur gehraai se nutrients upar laata hai. Southwest monsoon ke dauraan Kerala ke coast ke saath aisa hota hai. Thande, nutrients se bhare paani mein khilne wale plankton oil sardines ke un bade jhundon ko khilaate hain jin par Kerala ke machhuare depend karte hain.

13.3 Biogeochemical Cycles

Ek bargad ka tree hawa se carbon dioxide, soil se paani aur minerals, aur sunlight se energy leta hai. Jab ek patta girta hai, to fungi aur bacteria use tod kar woh materials wapas lauta dete hain. Living things (Earth ka biotic hissa) hamesha non-living hawa, paani, soil aur rock (Earth ka abiotic hissa) ke saath matter ka len-den karte rehte hain. Kyunki Earth ko space se lagbhag koi naya matter nahi milta, isliye carbon, nitrogen aur oxygen ke wahi atoms baar-baar use hone chahiye.

Kisi element ka living things aur unke aas-paas ke beech baar-baar ka safar biogeochemical cycle kehlaata hai: bio life ke liye, geo Earth ke liye, chemical elements ke liye. Energy Sun se andar aati hai aur heat ban kar nikal jaati hai, lekin matter ghoomta rehta hai. Yeh cycles ecosystems ko ek doosre se jodte hain. Yahi judaav ek kharab hue jungle ya polluted lake ko waqt ke saath theek hone deta hai, jab tak nuksaan bahut zyada na ho.

Hum inmein se chaar cycles follow karenge: water, carbon, nitrogen aur oxygen. Har ek ke liye dekho ki woh kin spheres se guzarta hai, use aam taur par kya steady rakhta hai, aur insaani activity use kahan balance se bahar dhakel rahi hai.

13.3.1 Water cycle

Water cycle ke steps tum pehle se jaante ho (Fig. 13.12). Sun ki garmi samundar, rivers aur lakes se paani ko evaporate karti hai, aur plants apne patton se transpiration dwara water vapour chhodte hain. Upar uthti vapour thandi hoti hai, chhoti boondon mein condense hoti hai aur clouds banati hai. Paani precipitation ke roop mein wapas aata hai: baarish, snow ya ole. Uska kuch hissa surface par beh kar streams mein aur wapas samundar mein jaata hai (runoff). Kuch soil aur rock mein samaa jaata hai (infiltration) aur groundwater ki tarah jama hota hai.

Raaste mein paani ek delivery service ki tarah kaam karta hai. Soil se risti baarish calcium aur potassium jaise minerals ghola leti hai, jinhe phir jadein le leti hain. Rivers ghule hue nutrients aur silt ko coast tak le jaati hain, aur un estuaries aur uthle samundaron ko upjaau banati hain jahan kai machhliyan ande deti hain. Zameen par koi bhi plant ya animal is cycle se milne wale meethe paani ke bina zinda nahi reh sakta.

Warming water cycle ki speed badha rahi hai. Har 1 °C warming par hawa karib 7 % zyada water vapour rakh sakti hai, isliye toofanon ke paas girane ke liye zyada paani hota hai. Nateeja hai extremes ka cycle: pahadon mein zyada cloudbursts aur ek hi din ki moosladhaar baarish ke baad nadi ban jaati shehar ki sadkein, lekin baarishon ke beech lambe sookhe gaps bhi. Sookhi zameen par tez baarish zyadatar beh jaati hai, apne saath topsoil le jaati hai, wells ko bharne ke liye zameen mein samaane ke bajaye, isliye kisaanon ke paas April aur May mein sahaare ke liye kam groundwater hota hai. Himalaya mein bahut upar, sikudte glaciers pehle un rivers ko phula dete hain jo unse nikalti hain aur baad mein sookhe mausam mein unhe patla chhod denge. Unka meltwater, polar ice sheets ke melt ke saath, India ki lambi coastline ke saath samundar ko dheere-dheere upar utha raha hai. Kya tum is paragraph mein paanchon spheres dhoondh sakte ho?

13.3.2 Carbon cycle

Life ke liye zaroori koi bhi molecule dekho, chahe sugar ho, fat, protein ya DNA, tumhe usmein carbon atoms ka dhaancha milega. Carbon living things ke saath-saath chaaron non-living spheres mein bhi jama hai. Yeh hawa mein $\mathrm{C}\mathrm{O}{\phantom{X}}_2$ ki tarah hai, aur plants, animals aur soil mein hai. Yeh limestone jaisi rocks mein aur coal, oil aur natural gas jaise fossil fuels mein hai. Yeh oceans mein bhi hai, paani mein ghula hua aur samudri jeevon ke shells mein (Fig. 13.14). Is cycle ki ek fast lane hai aur ek slow lane.

Fast cycle mein dino se saalon tak lagte hain. Hare plants sunlight ka use karke photosynthesis mein carbon dioxide aur paani ko glucose mein badalte hain. Animals woh carbon plants ya doosre animals ko khaakar paate hain. Plants, animals aur microbes respiration mein glucose ko phir tod dete hain aur carbon ko $\mathrm{C}\mathrm{O}{\phantom{X}}_2$ ki tarah saans se bahar chhodte hain. Jab organisms marte hain, to decomposers unhe khaate hain aur unka baaki carbon $\mathrm{C}\mathrm{O}{\phantom{X}}_2$ ki tarah chhodte hain.

Slow cycle mein laakhon saal lagte hain. Kabhi-kabhi mare hue plants aur animals decomposers ke kaam poora karne se pehle hi daldal mein ya sea bed par dab jaate hain. Yugon tak zameen ke andar dabne aur garam hone se unke remains dheere-dheere coal, oil aur natural gas ban jaate hain. Power stations, vehicles aur factories in fuels ko jalaate hain, aur jis carbon ko band hone mein laakhon saal lage, woh pal bhar mein hawa mein laut aata hai.

Samundar ek bade carbon sponge ki tarah kaam karta hai. Carbon dioxide surface par ghulti hai, khaas kar thande paani mein, aur react karke carbonate aur bicarbonate ions banati hai. Wahan se life kaam sambhaal leti hai. Phytoplankton, yaani surface ke paas tairte microscopic algae, is ghule carbon se photosynthesis karte hain, jabki corals, oysters aur chalky plankton carbonate se shells banate hain. Jab woh marte hain, to shells aur organic kanon ki ek lagaatar 'snow' andhere mein neeche girti hai. Jo carbon gehre sea floor tak pahunchta hai, woh sadiyon ya usse bhi zyada tak hawa se door reh sakta hai, aur laakhon saalon mein shells sakht hokar limestone aur chalk ban sakte hain.

Insaano ne yeh balance bigaad diya hai. Fossil fuels jalane aur jungle kaatne se hawa mein $\mathrm{C}\mathrm{O}{\phantom{X}}_2$ ki maatra saal dar saal badhi hai. Ise 1958 se Hawaii ki Mauna Loa observatory mein lagaatar naapa ja raha hai. Wahan saalana average 1960 mein karib 317 parts per million (ppm) se badhkar 2025 mein karib 427 ppm ho gaya, yaani lagbhag 35 % badhotri (Fig. 13.15). Ice cores dikhate hain ki kam se kam 800 000 saalon mein yeh itna high nahi raha. Har saal ke andar bhi level kuch ppm upar-neeche hota hai. Yeh har northern summer mein girta hai, jab Northern Hemisphere ke vishaal jungle aur khet ugte hain aur $\mathrm{C}\mathrm{O}{\phantom{X}}_2$ lete hain.

Agar plants ko $\mathrm{C}\mathrm{O}{\phantom{X}}_2$ chahiye, to chinta kyun? Kyunki dikkat rate ki hai. Jungle, soil aur oceans insaano ke har saal chhode carbon dioxide ka sirf karib aadha lete hain, isliye baaki hawa mein jama hota jaata hai aur greenhouse razaai ko mota karta hai (Section 13.1.3). Glaciers, sea level, monsoon aur kheti ke liye iska kya matlab hai, yeh Section 13.4 mein dekhenge.

13.3.3 Nitrogen cycle

Har protein aur har DNA aur RNA molecule mein nitrogen hota hai, isliye koi bhi organism iske bina badh nahi sakta. Nitrogen hamare chaaron taraf hai, tumhari har saans ka 78 %, phir bhi na tum aur na koi plant us gas ka ek bhi molecule use kar sakta hai. Nitrogen gas ($\mathrm{N}{\phantom{X}}_2$) itni unreactive hai ki living things sirf woh nitrogen le sakte hain jo fix ho chuka ho: hydrogen ya oxygen ke saath aise compounds mein juda ho jo soil ke paani mein ghul jaate hain. Nitrogen ko hawa se soil, paani aur living things se hokar wapas hawa tak follow karna nitrogen cycle banata hai (Fig. 13.16). Iske paanch stages hain:

1. Nitrogen fixation. Nitrogen-fixing bacteria hawa ke $\mathrm{N}{\phantom{X}}_2$ ko ammonia ($\mathrm{N}\mathrm{H}{\phantom{X}}_3$) mein badalte hain. Kuch, jaise Rhizobium, chana, matar aur moong jaise legumes ki jadon par chhoti soojan mein rehte hain jinhe root nodules kehte hain. Doosre, jaise Azotobacter, soil mein aazaad rehte hain. Bijli bhi thoda nitrogen fix karti hai, nitrogen oxides ke roop mein jinhe baarish soil mein baha deti hai.
2. Nitrification. Soil bacteria ke do groups baari-baari kaam karte hain: Nitrosomonas ammonia ko nitrite ($\mathrm{N}\mathrm{O}{\phantom{X}}_2{\phantom{X}}^{-}$) mein badalta hai, aur Nitrobacter nitrite ko nitrate ($\mathrm{N}\mathrm{O}{\phantom{X}}_3{\phantom{X}}^{-}$) mein.
3. Assimilation. Plants apni jadon se nitrates (aur kuch ammonium) lete hain aur unse proteins aur nucleic acids banate hain. Animals apna nitrogen plants ya doosre animals ko khaakar paate hain.
4. Ammonification. Jab organisms marte hain, ya animals peshaab aur gobar karte hain, to bacteria aur fungi jaise decomposers nitrogen compounds ko tod kar ammonia wapas soil mein chhodte hain.
5. Denitrification. Paani se bhari, bina hawa wali soil mein Pseudomonas jaise denitrifying bacteria kuch nitrate ko wapas $\mathrm{N}{\phantom{X}}_2$ gas mein badal dete hain, jo hawa mein laut jaati hai aur cycle poora karti hai.

13.3.4 Oxygen cycle

Oxygen Earth ke crust mein sabse zyada paaya jaane wala element hai, uske mass ka lagbhag aadha: quartz aur granite jaisi rocks zyadatar silicon aur metals se judi oxygen hain. Planet ki oxygen ka sirf chhota sa hissa free $\mathrm{O}{\phantom{X}}_2$ gas hai, lekin wahi hissa hawa ka 21 % hai, aur living things usi par depend karte hain. Oxygen paani, carbon dioxide aur har carbohydrate, fat, protein aur nucleic acid mein bhi judi hai. Yahan hum oxygen cycle ka woh hissa follow karenge jo hawa mein $\mathrm{O}{\phantom{X}}_2$ ka level steady rakhta hai (Fig. 13.17).

Teen processes hawa se oxygen nikaalte hain: plants, animals aur microbes mein respiration, lakdi, coal, petrol aur gas ka jalana, aur dheemi oxide formation, jaise iron mein zang lagna. Respiration aur jalana carbon dioxide aur paani wapas dete hain. Oxygen hawa mein mainly photosynthesis se lautti hai, jo sunlight se paani ko todta hai aur $\mathrm{O}{\phantom{X}}_2$ chhodta hai. Ocean ke phytoplankton iska lagbhag aadha banate hain, aur zameen ke plants baaki ka zyadatar hissa. Jab tak banna aur kharch hona balance mein rehte hain, hawa mein oxygen ka level mushkil se badalta hai.

13.4 Earth ke Processes par Insaan ka Asar

Grade 8 mein tumne climate change aur usse aane wale crises padhe the. Yahan hum mechanism dekhenge: hamare kaam abhi trace kiye gaye cycles ko kaise atka dete hain. Fossil fuels jalane se hawa mein carbon dioxide us speed se zyada judti hai jitni tezi se plants, soil aur oceans use wapas le sakte hain. Extra $\mathrm{C}\mathrm{O}{\phantom{X}}_2$ greenhouse effect ko mazboot karta hai, aur uske baad ki warming zyada extreme weather laati hai aur kai species ko extinction ki taraf dhakelti hai.

Oceans ab tak insaano ke chhode carbon dioxide ka karib ek-chauthaai sokh chuke hain, jisse warming dheemi hui hai. Lekin iski keemat hai. Ghula hua $\mathrm{C}\mathrm{O}{\phantom{X}}_2$ samundar ke paani ko thoda zyada acidic bana deta hai: 1800s se surface ocean ka average pH karib 8.2 se girkar karib 8.1 ho gaya hai. Zyada acidic paani mein corals, shellfish aur chhote shell wale plankton ke liye apne skeleton banana mushkil ho jaata hai, aur isse poore marine food webs khatre mein padte hain. Saath hi, garam paani kam gas gholta hai, isliye garam hota ocean theek usi waqt kamzor carbon sink banta jaata hai jab humein uski sabse zyada zaroorat hai.

Jungle aur soil doosre bade carbon sinks hain, aur kaata gaya har hectare jungle unhe kamzor karta hai. India ka apna raasta is problem ke dono pehlu dikhata hai: hamari electricity ka sabse bada hissa ab bhi coal se aata hai, phir bhi solar capacity karib das saal mein tees guna se zyada badh gayi hai. Neeche ki table Earth ke kuch vital signs unke sources ke saath ikattha karti hai.

Fertilisers nitrogen cycle ko bigaadte hain. Kabhi-kabhi kisaan utna urea ya doosra nitrogen fertiliser daal dete hain jitna unki fasalein le hi nahi sakti. Phir baarish extra nitrate ko ponds, lakes aur rivers mein, aur aakhir mein coastal samundaron mein baha deti hai. Wahan yeh algae ki achaanak, ghani growth ko khaana deta hai jise algal bloom kehte hain. Jab algae marti hain, to unhe khaane wale decomposer bacteria paani mein ghuli oxygen ko khatam kar dete hain, aur machhliyon ka dum ghut jaata hai (Fig. 13.18). Nutrients ki is zaroorat se zyada bharmaar ko eutrophication (सुपोषण) kehte hain. Sewage aur phosphate se bhare detergents bhi yahi karte hain. Yeh lakes ko maar deta hai aur coastal fisheries ko nuksaan pahunchata hai.

Jungle kaatna dikhata hai ki ek kaam ek saath har sphere tak kaise pahunchta hai:

Busy shehar mein shaant, dhoop wali dopahar ko vehicles ke dhuein se nikle nitrogen oxides aur bina jale fuel ki vapours sunlight mein pak kar ek bhoori dhundh bana dete hain jise smog kehte hain. Iske ingredients mein se ek ozone hai, wahi gas jo stratosphere mein bahut upar humein bachaati hai. Yahan neeche, jis hawa mein hum saans lete hain, woh lungs aur aankhon mein jalan karti hai, asthma badhaati hai aur fasalon ki growth rok deti hai.

Duniya ozone layer ko theek karne mein kaamyaab kyun hui, lekin carbon dioxide ko rokne mein nahi? CFCs kaafi kam companies banati thi aur safer substitutes taiyaar the, isliye Montreal Protocol unhe jaldi band kar saka. Carbon dioxide hamare lagbhag har kaam se aata hai, power stations aur vehicles se lekar cement kilns aur kheton tak, isliye use kam karne ka matlab poori economies ko badalna hai. Kyoto Protocol aur Paris Agreement ne targets tay kiye, lekin global emissions badhte hi rahe hain.

India inmein se kai par ek saath kaam kar raha hai. Solar capacity 100 GW paar kar chuki hai, bade tree-planting drives chal rahe hain, aur Soil Health Cards kisaanon ko batate hain ki unke kheton ko asal mein har nutrient kitna chahiye, taaki woh fertiliser ka zyada use na karein.