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Inorganic carbonate can be an important component of atmospheric particulate matter in arid environments where mineral dust components contribute significantly to air particulate matter. Carbonate carbon (CC) is only rarely quantified in atmospheric studies and methods to quantify carbonate in atmospheric samples are rare. In this manuscript, we present a novel protocol for quantifying carbonate carbon in atmospheric particulate matter samples, through the acidification of aerosol filters at ambient pressure and temperature and subsequent measurement of carbon dioxide (CO2) released upon acidification. This method is applicable to a variety of filter media used in air pollution studies, such as Teflon, cellulose, or glass fiber filters. The method allows the customization of the filter area used for analysis (up to 24 cm2) so that sufficient CO2 can be detected when released and to assure that the sample aliquot is representative of the whole filter. The resulting detection limits can be as low as 0.12 µg/cm2. The analysis of a known amount of sodium bicarbonate applied to a filter resulted in a relative error within 15% of the known mass of bicarbonate when measured 20 min after acidification. A particulate matter sample with aerodynamic diameter larger than 2.5 µm (PM>2.5) collected via cascade impaction on a high-volume aerosol sampler yielded good precision, with a CC concentration of 4.4 ± 0.3 µgC/cm2 for six replicates. The precision, accuracy, and reproducibility of this method of CC measurement make it a good alternative to existing quantification methods. 

Abstract. Long-term environmental research networks are one approach toadvancing local, regional, and global environmental science and education. Aremarkable number and wide variety of environmental research networks operatearound the world today. These are diverse in funding, infrastructure,motivating questions, scientific strengths, and the sciences that birthed andmaintain the networks. Some networks have individual sites that wereselected because they had produced invaluable long-term data, while othernetworks have new sites selected to span ecological gradients. However, alllong-term environmental networks share two challenges. Networks must keeppace with scientific advances and interact with both the scientific communityand society at large. If networks fall short of successfully addressing thesechallenges, they risk becoming irrelevant. The objective of this paper is toassert that the biogeosciences offer environmental research networks a numberof opportunities to expand scientific impact and public engagement. Weexplore some of these opportunities with four networks: the InternationalLong-Term Ecological Research Network programs (ILTERs), critical zoneobservatories (CZOs), Earth and ecological observatory networks (EONs),and the FLUXNET program of eddy flux sites. While these networks were foundedand expanded by interdisciplinary scientists, the preponderance of expertise andfunding has gravitated activities of ILTERs and EONs toward ecology andbiology, CZOs toward the Earth sciences and geology, and FLUXNET towardecophysiology and micrometeorology. Our point is not to homogenize networks,nor to diminish disciplinary science. Rather, we argue that by more fullyincorporating the integration of biology and geology in long-termenvironmental research networks, scientists can better leverage networkassets, keep pace with the ever-changing science of the environment, andengage with larger scientific and public audiences.