Spheroidal carbonaceous particles (SCP), a constituent of coal fly ash, are a sensitive indicator of local and regional coal combustion archived in lake sediments. Their unique morphology and chemical composition are not replicated by any naturally occurring substance on Earth. SCP accumulation in sediments has also been correlated to accumulation of heavy metals such as Mn, Fe, Ti, and Pb. We reconstructed SCP accumulation in a former mill pond in Williamsburg, VA, Lake Matoaka, and find a bimodal distribution with peaks c. 1790 and c. 1953. We believe that our study is the first to identify SCPs in sediments prior to the early 1800s, making this record unique. Grain size analysis shows a statistically significant difference in grains from the two peaks indicating different fly-ash provenance. The particles first appear in Lake Matoaka in 1734 and steadily increase from 15-300 SCP/gDM peaking in 1790. SCP concentration remains constant at ~100-200 SCP/gDM from c. 1800-1860, when a rapid increase in particle accumulation resumes, increasing abruptly from 500 SCP/gDM in 1860 to >8000 SCP/gDM in 1953. Modern accumulation rates have decreased in response to emission restricting legislation in 1970 but continue to accumulate 1000 SCP/gDM in surface sediments. Trends in SCP accumulation mirror major historical events including prominent socio-political wars and economic depressions.

Determining the metal content of soil collected from small arms training ranges (SARs) is difficult and controversial because the contamination consists of fine particulates abraded from bullets and larger fragments such as intact bullets and spent shell casings. This heterogeneous distribution of materials can be difficult to sample reproducibly and difficult to prepare for analysis. Similar issues are encountered with sampling and analysing solid residues of energetic compounds for which grinding to 75 microns is necessary to achieve excellent precision. Issues to be resolved for SAR metals include the necessity of sieving, the extent of contamination from grinding, and the proper digestion procedure for efficient recovery. The work reported in this manuscript employed field and laboratory sampling approaches developed for energetics and examined a variety of laboratory sample preparation techniques for SAR metals. Application of the sampling approaches used for energetics to metals was straightforward. The US Environmental Protection Agency (USEPA) nitric acid digestion procedure is effective for the recovery of three of the most important SAR metals, copper, lead and zinc, when analysing a 2 g portion of the 2 mm fraction of an unground soil sample. However, sieving the sample ignores a large portion of the total metal load and a total digestion with hydrofluoric acid is necessary to determine the concentration of all naturally-occurring metals in the sample. Finally, the USEPA-approved method for metal analysis is inappropriate for tungsten unless supplemented with phosphoric acid.