A 2600-year record of past polycyclic aromatic hydrocarbons (PAHs) deposition at Holzmaar (Eifel, Germany)

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are a proxy for climate- and human-related historical fire activity which has rarely been used beyond 1800AD. We explored the concentration and composition patterns of PAHs together with other proxies (charcoal, C, N, S, δ13C, δ15N, and δ34S) in a sediment core of Holzmaar as indicators of variations in climate and anthropogenic activity over the past 2600years. The concentrations of pyrogenic PAHs remained low (<500ngg−1) from the pre-Roman Iron Age (600BC) until the first significant increases to ca. 1000–1800ngg−1 between 1700 and 1750AD related to regional iron production. The highest increases in pyrogenic PAH concentrations occurred with industrialization peaking in the 1960s. PAH concentrations in most recent sediments decreased to pre-industrial levels because of emission control measures and the switch from coal to oil and gas as major fuel sources. Fluxes of PAHs (mgkm−2yr−1) increased in the order Migration Period and Early Middle Ages<pre-Roman Iron Ages<Roman era<High Middle Ages and Renaissance<pre-industrial modern period<industrial modern period. The changes of PAHs fluxes in pre-industrial times parallel known changes in local, regional and continental anthropogenic activity and climatic variations or their interactions across these historical periods. Perylene, a mainly biologically produced compound, was the dominant PAH in pre-industrial times. The Migration Period and the Early Middle Ages witnessed the most profound and simultaneous changes to the sedimentary organic matter properties in the past 2600years including the lowest PAH fluxes because of reduced human activity and more negative δ13C and δ15N values probably in response to colder and wetter conditions.