Buried soils as archives of paleo-pollution in the North China Plain

WashU’s involvement: This project was funded and enabled by the Nano Research Facility at Washington University.

Abstract: Ancient soils contain geochemical signatures of human land use, making them usable as a “golden spike,” or globally synchronous marker, to identify traces of the early “Anthropocene.” This article examines the sedimentary record in northern China to determine when, and under what cultural circumstances, did ancient pollution appear in buried soils and sediments. Using methods of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Local Enrichment Factor (LEF), we analyzed the elemental geochemistry of soil and sediment samples (n = 333) that span the Holocene from three rural sedimentary sequences in Henan Province. We compared results to geochemical data from a 2000-year sequence of urban occupation from the nearby city of Kaifeng. We expected to find higher concentrations of heavy metals in anthropogenic soils at both rural and urban locations, as pollution from human activities intensified as a result of pre-modern industrialization around 1000 BP. Instead, ancient soils in rural contexts are moderately enriched (LEF ≈ 6) in several metals (Arsenic, Barium, Zinc, and Lead) starting around the Bronze Age (ca. 4000-3000 BP). Additionally, after 1000 BP, most soils show no significant enrichment. At the urban site of Kaifeng, ancient soils have heavy metal concentrations (Zinc and Lead) an order of magnitude greater than the rural sites. This study showed that, while anthropogenic soils are sinks for ancient pollution, they contain a signature that must be understood within a localized geochemical context. Anthropogenic soils are therefore a useful proxy for defining the geographic extent, and thus the patchiness, of ancient human land use activities, rather than a “golden spike” of the early “Anthropocene.”

Citation: Storozum, Michael J., Zhen Qin, Yiming V. Wang, and Haiwang Liu. “Buried soils as archives of paleo-pollution in the North China Plain.” Anthropocene (2020): 100251. https://doi.org/10.1016/j.ancene.2020.100251