1. Could you explain the significance of your article to the non-specialist?

The focus of PCCP article is on the surface chemistry of calcite, an abundant carbonate minerals.  Field measurements that show that carbonate minerals may be particularly reactive components of mineral dust with trace atmospheric gases.  Although carbonate surfaces are ubiquitous in nature there are very few fundamental studies of the reaction chemistry of carbonate surfaces as a function of relative humidity.  Surface reactions in the presence of adsorbed water differ from those in the absence of water.  In this PCCP article, the authors combine spectroscopic with spatial probes to learn more about the surface chemistry of carbonate interfaces with sulphur dioxide, an atmospheric pollutant.  These studies show that adsorbed water plays a role in these reactions as a result of facile surface ion mobility. The extent of reaction is significantly enhanced, approximately five- to ten-fold in the presence of adsorbed water between 30 and 85% relative humidity.

2. What has motivated you to conduct this work?  

Surface reactions of carbonate interfaces are important from a number of perspectives.  Carbonates are a reactive component of mineral dust aerosol and reactions of trace gases with carbonates can alter the chemical composition of the atmosphere. Biologically-driven calcium carbonate deposition serves as a sink for atmospheric carbon dioxide and also as a buffer in ocean chemistry.  Additionally, calcium carbonate is prevalent in buildings, as well as statues and monuments, providing another source of surfaces for reaction with trace atmospheric trace gases  which also leads to the degradation of these structures.  In our work we are interested in using state-of-the-art probes to study the fundamental molecular chemistry that occurs at carbonate interfaces with air pollutants. 

3. Where do you see this work developing in the future? 

The focus of these studies is to investigate fundamental aspects of reactions on carbonate surfaces that are of importance in atmospheric chemistry.  If atmospheric chemistry models are to accurately describe the chemistry of the troposphere, laboratory studies designed to understand the mechanisms of these reactions as well as determining accurate kinetics of these reactions are needed. We are very much interested in connecting the fundamental molecular surface chemistry to global impacts. These types of studies described in this PCCP article will enable us to make these connections. Additionally, valuable information is gleaned about the transformation and degradation of structural materials that can occur from reactions with atmospheric gases.

4. Are there any particular challenges facing future research in this area? 

It is difficult to study fundamental aspects of surface reactions under environmentally relevant conditions as many of the well-developed techniques operate under ultrahigh vacuum conditions.   More work is needed to further develop measurement techniques that can be done under relevant conditions to gain a detailed physicochemical understanding the of environmental molecular surface processes.