Skip to content

Activity Examples

This section provides working code examples for computing chemical activity in aerosol particles using Particula's activity strategies. Learn how to use ideal, kappa-Kohler, and BAT (non-ideal) models through practical examples.

Overview

Activity determines how species partition between gas and particle phases and controls water uptake in hygroscopic aerosols. These examples demonstrate:

  • Computing activity from mass concentrations
  • Comparing ideal vs. non-ideal activity models
  • Using the kappa parameter for hygroscopic growth
  • Integrating activity with equilibria calculations

Example Scripts

  • Ideal Activity

    Basic ideal activity calculation using Raoult's Law with ActivityIdealMolar. Good starting point for understanding the activity API.

  • BAT Model Activity

    Non-ideal activity using the Binary Activity Thermodynamic (BAT) model with ActivityNonIdealBinary. Compares ideal vs. non-ideal activity for organic-water mixtures.

  • Kappa Parameter Activity

    Hygroscopic activity using kappa-Kohler theory with ActivityKappaParameter. Demonstrates water activity at different compositions for inorganic aerosols.

  • Equilibria Partitioning

    Liquid-vapor partitioning using LiquidVaporPartitioningStrategy. Shows how activity integrates with equilibria calculations for gas-particle partitioning.

Interactive Tutorial

For a comprehensive hands-on introduction, see the interactive Jupyter notebook:

Activity Tutorial

This tutorial covers:

  • What is activity and why it matters for aerosol modeling
  • Ideal activity with Raoult's Law
  • Non-ideal activity with the BAT model
  • Kappa parameter for hygroscopic growth
  • Integration with equilibria calculations
  • Visualization of activity vs. composition

Quick Reference

Available Strategies

Strategy Import Description
ActivityIdealMolar par.particles.ActivityIdealMolar Raoult's Law (mole fractions)
ActivityIdealMass par.particles.ActivityIdealMass Ideal (mass fractions)
ActivityKappaParameter par.particles.ActivityKappaParameter Kappa-Kohler model
ActivityNonIdealBinary par.particles.ActivityNonIdealBinary BAT non-ideal model

Basic Usage Pattern

import numpy as np
import particula as par

# 1. Create strategy
strategy = par.particles.ActivityIdealMolar(
    molar_mass=np.array([18.015e-3, 200.0e-3]),  # kg/mol
)

# 2. Define mass concentrations
mass = np.array([0.5e-9, 0.5e-9])  # kg/m^3

# 3. Compute activity
activity = strategy.activity(mass_concentration=mass)