Stephen Mueller & Jonathan Mallard Tennessee Valley Authority Modeling Natural Fine Particle Concentrations Using the CMAQ Model with Added Treatments of Reduced Sulfur Compounds Stephen Mueller & Jonathan Mallard Tennessee Valley Authority

Research on Natural Particle Levels Identify natural emissions not routinely considered by US regulatory modeling. Develop expanded natural emissions data base. Identify model changes needed to accommodate expanded list of natural emissions. Quantify effects of revised emissions/model versus results from “standard” modeling approach.

Motivation for Research US EPA lowered the 24-hr PM2.5 standard & is considering a lower annual standard. US Regional Haze Rule explicitly requires consideration of “natural haze” components. Efforts to establish secondary standards (e.g., SOx/NOx) should consider natural pollutants.

Natural Emissions Current Technology Added Biogenic VOCs Lightning NOx Reduced sulfur (marine, wetlands, soil, lakes & geothermal ) Biogenic NOx Fires Windblown dust Ocean chlorinated gases Sea salt Ocean ammonia Animal ammonia Geogenic SO2* *Not typically included in data inventories although the system is designed to include it.

Study Area – Modeling Domain Limit of optimal lightning detection

New Natural Emissions Species Dimethylsulfide (DMS): oceans, lakes, coastal wetlands. H2S: oceans, lakes, coastal wetlands, geothermal features (hot springs, fumaroles, etc.) Nitryl chloride (ClNO2) & HCl: oceans – these emissions are surrogates for complex interaction between air pollutants & sea salt.

Natural & Anthropogenic Emissions in July 2002 Data Base “Orange”=anthropogenic “Green”=natural

CMAQ* Model CB05 Updates Gas chemistry Cloud chemistry Added reactions involving DMS, H2S and derivatives. Added reactions involving chlorine, OH, & DMS and its derivatives. Added ClNO2, HCl and chlorine radical reactions to CB05. *Version 4.6

Grid-Averaged Time Series: Sulfur

Grid-Averaged Time Series: Aerosols

Maximum Simulated “Natural” 24-hr Aerosol Concentrations for 2002 Sulfate Organic Carbon

Simulated Particles vs. Haze Guidance

Distribution of Simulated Natural + Background PM2.5 at 50 Receptors

Primary Conclusions CMAQ natural particle simulations useful tool for investigating contributions of natural systems to PM2.5/haze, ozone and deposition. EPA natural haze guidance is too simplistic. Modeling DMS & H2S introduces competition for OH that reduces sulfate formation in natural systems…effects in combined emissions simulations?