#!/usr/bin/env python
# coding: utf-8

# # Converting conditions and pH scales
# 
# *Based on **CO2SYSExample2.m** for MATLAB by Steven van Heuven.*
# 
# A sample is measured in the lab to have a pH of 7.8 on the Total scale at 25 °C under atmospheric pressure.
# 
# What would its pH have been in situ in the ocean: at 2 °C and 4000 dbar pressure (roughly 4000 m depth) on the Seawater scale?
# 
# Additional properties:
# 
#   * Alkalinity = 2400 μmol/kg
#   * Salinity = 35
#   * Total silicate = 50 μmol/kg
#   * Total phosphate = 50 μmol/kg
#   
# ## Define conditions
# 
# The first step is to define the input and output conditions that we want to use with PyCO2SYS.  In this case, we only need a single value for every variable:

# In[1]:


# Define input and output conditions
kwargs = dict(
    par1_type = 1,  # The first parameter supplied is of type "1", which means "alkalinity"
    par1 = 2400,  # value of the first parameter
    par2_type = 3,  # The second parameter supplied is of type "3", which means "pH"
    par2 = 7.8,  # value of the second parameter
    salinity = 35,  # Salinity of the sample
    temperature = 25,  # Temperature at input conditions
    temperature_out = 2,  # Temperature at output conditions
    pressure = 0,  # Pressure    at input conditions
    pressure_out = 4000,  # Pressure    at output conditions
    total_silicate = 50,  # Concentration of silicate  in the sample (in umol/kg)
    total_phosphate = 2,  # Concentration of phosphate in the sample (in umol/kg)
    opt_pH_scale = 1,  # pH scale at which the input pH is reported ("1" means "Total Scale")
    opt_k_carbonic = 4,  # Choice of H2CO3 and HCO3- dissociation constants K1 and K2 ("4" means "Mehrbach refit")
    opt_k_bisulfate = 1,  # Choice of HSO4- dissociation constant KSO4 ("1" means "Dickson")
    opt_total_borate = 1,  # Choice of boron:sal ("1" means "Uppstrom")
)
print('Conditions have been defined!')


# ## Run PyCO2SYS
# 
# Next, we run PyCO2SYS to solve the marine carbonate system under the input and output conditions and calculate related variables:

# In[2]:


# Import PyCO2SYS
import PyCO2SYS as pyco2

# Run PyCO2SYS
results = pyco2.sys(**kwargs)

# Extract and print out the result
pH_insitu_SWS = results['pH_sws_out']
print('The in situ pH on the Seawater scale was: {:.3f}'.format(pH_insitu_SWS))


# See [the documentation](https://pyco2sys.readthedocs.io/en/latest/co2sys_nd/) for more detailed information about the arguments and results of PyCO2SYS.