Mercury in archaeological human bone: biogenic or diagenetic?

Abstract

We investigated mercury (Hg) in human bone from archaeological sites in the Iberian Peninsula where the cultural use of cinnabar (HgS) as a pigment, offering or preservative in burial practices has been documented from the 4th to 2nd millennia cal B.C. (Late Neolithic, Copper Age and Bronze Age). Previous analyses have shown high levels of total mercury (THg) in human bone at numerous Neolithic and Chalcolithic sites in this region, but the question remains if this mercury entered the bones via diagenetic processes in the soil, especially where cinnabar powder and paint was found associated with the burials, or if it entered the bone via biogenic pathways from exposure to mercury from using cinnabar in life. We analyzed the humerus, femur, and tibia from a total of 30 individual burials from four Neolithic to Bronze Age sites in Iberia and found low to high values of THg in these bones, with the humerus showing significantly more THg concentrations than other skeletal elements when the THg was greater than 1 ppm. This pattern of Hg deposition in skeletal material from different sites and ages strongly suggests a biogenic origin for the mercury. In addition, absence of detectable Hg in bones with high to low values of THg using SEM EDS analysis further discounts diagenetic intrusion of Hg or cinnabar particles into the bone from the soil. It is likely that greater stress and bone remodeling rates from use of heavy tools and other activities in life are responsible for higher THg in the humerus than other skeletal elements, but additional research is needed to verify this. humans also can occur via methylmercury (MeHg), which bioaccumulates and biomagnifies in food webs and can lead to acute or chronic mercury poisoning (Driscoll et al., 2013). This dietary pathway of exposure, since it is related to increasing mercury concentrations in species higher up the food chain, is typically correlated with higher concentrations of the heavier nitrogen isotope, δ 15 N ‰, which also increases with trophic level of diet (Jardine et al., 2006;Blévin et al., 2013).Mineral pigments, especially red from ochres (iron oxides), have a long archaeological record dating as far back as 200,000 to 300,000 years ago in Africa (Siddall, 2018). These pigments have been used as paint for rock art, body decoration, or in ceramics and as such need to

Approaching mercury distribution in burial environment using PLS-R modelling

“…Diagenesis is of major concern when trace elements are studied in archaeological bones, as there is the potential for the soil to be a source of elements for bones 30 , 55 . But works which assessed mercury diagenetic incorporation into bone in archaeological burial environment 22 , 23 , 31 , 41 , 42 conclude that mercury bone levels were no related with diagenesis, unless the soils were naturally enriched in mercury.…”

Comparison of trace element chemistry in human bones interred in two private chapels attached to Franciscan friaries in Italy and Denmark: an investigation of social stratification in two medieval and post-medieval societies

“…Mercury had an extremely low environmental occurrence in most medieval societies in both Denmark and Italy [2,32]. Even so, Hg has been found in high concentrations in medieval and post-medieval human individuals in several studies [2,32,[38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. Some individuals were only exposed to the environmental Hg background, which has been estimated to correspond to 80 ng g −1 in cortical and 300 ng g −1 in trabecular bone tissue in Danish and German medieval and post-medieval skeletons [46].…”

“…Diagenetic deposition of Hg in human bones originating from the surrounding soil has not been observed in the many studies focusing on Hg measurements in human bones (see [51] and references therein). A likely explanation is that the environmental exposure is generally very low, and that sulphur containing compounds are abundantly present during the decay process of the body, which reacts with Hg to form the very stable and insoluble HgS [46].…”

Pigments — Mercury-based red (cinnabar-vermilion) and white (calomel) and their degradation products

“…In the former case, mercury derives from direct exposure; while in the latter, the process involves a transfer from the soil. On this topic, the research conducted by (a) Emslie et al (2015Emslie et al ( , 2019 (2013,2018) on Mexican Red Queens and other funerary contexts must indeed be cited for both their intrinsic and methodological value.…”