Properties and types of water. Properties of water

Transcription

1 PART 3 Proprtis and typs of watr Proprtis of watr Chmical form: H 2 O Physical stats: gas (vapor) liquid (watr) solid (ic, snow) Molcular structur: On oxygn atom and two hydrogn atoms ar arrangd as in th figur blow. Th molcul is polar (it has dipol momnt). It has a positiv charg on th sid of th two hydrogn atoms and ngativ charg on th opposit sid. Watr is a good solvnt bcaus ot th polarity of watr molcul m = 1 Å polar (dipol momnt)

2 Comprssibility (10-10 Pa -1 ) Viscosity (10-3 Pa s) Dnsity (kg m -3 ) Rad: Appndix 1 Proprtis and typs of watr 12 Physical proprtis: g = spcific wight (kn m -3 ) = spcific dnsity (kg m -3 ) µ = dynamic viscosity (Pa s) = kinmatic viscosity (m 2 s -1 ) ß = comprssibility (Pa -1 ) Tabl 5. Physical proprtis of watr. Tmpratur ( C) Dnsity (kg m -3 ) Dynamic viscosity (10-3 Pa s) Comprssibility (10-10 Pa -1 ) Rang (%) Data from d Marsily, 1986, Quantitativ Hydrogology, Acadmic Prss, 440 p Tmpratur (C) Fig. 5. Physical proprtis of watr.

3 Proprtis and typs of watr 13 Isotopic composition: Thr stabl isotops of oxygn: 16 O - common (abundanc 99.76%) 18 O - rar (0.20%) 17 O - vry, vry, vry rar (0.04%) Z = 8 16 O 17 O 18 O N = Two stabl isotops of hydrogn: 1 H - common (99.984%) 2 H = D = dutrium - rar (0.016%) Radioactiv isotop of hydrogn: 3 H = T = tritium half-lif of 12.3 y dcay to hlium-3: T -> 3 H + - Bta dcay of 3 H to 3 H occurs by mitting - (or - ), nutron bcoms proton. Dcay of tritium is usd for dating of young ground watr (up to fw tns of yars). Combination H 2 O may rsult in: 1 H 16 O - "normal watr" HD 16 O - havy watr H 18 2 O - havy watr pnn Z = 2 3 H 4 H Z = 1 1 H 2 H 3 H N = ppn Isotops - lad to fractionation. Usful in studis of nvironmntal procsss, such as:- vaporation, - rcharg, - mixing.

4 Proprtis and typs of watr 14 Typs of watr on contact with solid Hygroscopic immobil watr [adsorbd in figur blow]: High binding nrgy. 1-3 molculs, attachd to surfac of grain du to molcular attraction. Can rmov by hating to 150 C Hygroscopic mobil watr [adsorbd in figur blow]: Lowr binding nrgy molculs, it is maximum dgr of hygroscopicity. Can rmov by hating to 90 C. Constitut 15-20% of all watr in clays, but lss than 5% in coarsr matrials. Also varis according to minralogy,.g.: 0.9% in quartz, 8-17% in fldspars, 36-48% in micas. Pllicular watr (or pndular or funicular) [adsorbd in figur blow]: Low binding nrgy. It is a film ovr hygroscopic watr. It is mobil. Maintaind by molcular forcs. Fr watr: in minrals (bound) in capillaris (small pors) gravitational (moving) Chmically bound watr: In minrals as H 2 O (.g., gypsum, CaSO 4 2H 2 O), HO -, (.g., gibbsit, Al(OH) 3 ), H + and H 3 O + ; ;; ;;; ; Bond nrgy (Pa) adsorbd adhsiv ;; ;; fr watr Fig. 6. Binding nrgy for watr molculs (d Marsily, 1986). Distanc (10-6 m)

5 Proprtis and typs of watr 15 Juvnil watr: Origin of ground watr From th intrior of th arth. Has nvr bn in surficial watr cycl. It is first watr cratd from O and H. Mantl: largst sourc, kg Crust: from to kg (from mantl) Exampl: minral muscovit (KAl 2 (OH) 2 Si 4 O 10 ) has 8.5% OH and 4.5% H 2 O Answr to qustion posd in class on 8/30/00: Vry littl watr circulating today is of rcnt juvnil origin. Most of th watr that coms out of volcanos and hot springs is mrly rcycld ground watr. Stabl isotops of oxygn and hydrogn indicat that no mor than 1% of juvnil watr may b hiddn within th mtoric watr. Sourcs: H.W. Mnard, 1974, Gology, rsourcs, and socity, p. 206, Frman F. Phillips (Nw Mxico Tch), prsonal communication, August Connat watr (or formation watr): It was onc a part of surficial watr cycl and thn it was trappd in sdimnts. Has composition dpndnt on rock through which it flows (dissolution and prcipitation ar important factors controlling chmical composition of watr). Mtoric watr (or prcipitation watr): Watr prsntly circulating btwn th atmosphr and th hydrosphr. Entrs groundwatr systms by infiltration. It has composition similar to rain watr, but volvs towards quilibrium with rock formation. Mtoric watr is of intrst to us bcaus of its occurrnc in th shallow subsurfac.

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