code: def O2_sat(P_air, temp):
      
      fraction_O2 = 0.21
      P_O2 = P_air * fraction_O2
      return ((P_O2.to(u.atm).magnitude) *
              u.mg/u.L*np.exp(1727 / temp.to(u.K).magnitude - 2.105))
docs: Calculate saturaed oxygen concentration in mg/L for 278 K < T < 318 K
  
      :param P_air: Air pressure with appropriate units
      :type P_air: float
      :param temp: Water temperature with appropriate units
      :type temp: float
  
      :return: Saturated oxygen concentration in mg/L
      :rtype: float
  
      :Examples:
  
      >>> from aguaclara.research.environmental_processes_analysis import O2_sat
      >>> from aguaclara.core.units import unit_registry as u
      >>> round(O2_sat(1*u.atm , 300*u.kelvin), 7)
      <Quantity(8.0931572, 'milligram / liter')>