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Multi-proxy records (pollen, particle size, loss on ignition, C:N ratios and radioisotopes, 210Pb and 137Cs) of natural and anthropogenic environmental change are reported for sediment cores from three lakes in the Songnen Plain of northeastern China. These data provide high-resolution records of vegetation history and catchment dynamics for the region over the past 200 years. Records show that vegetation initially responded to a cooler and drier climate during the Little Ice Age with high values of Pinus, Ephedra and Amaranthaceae and low values of Cyperaceae. As anthropogenic activity increased in northeastern China, Pinus gradually declined while broad-leaved deciduous vegetation increased in the region from 1900 CE. Aquatic taxa also increased from 1900 CE as the wetlands responded to changing lake water levels and agricultural activities. Land policy implementation had a profound impact on the vegetation with arboreal pollen in Keqin and Hongyan lakes declining from 1900 CE as marginal land was reclaimed, and agricultural activities increased. Vegetation diversity increased as agricultural activities caused environmental disturbance, with pollen taxa indicating human disturbance including Humulus, Polygonum and Xanthium. Silt and organic content increased and C:N ratios declined after 1940 CE as erosion in the catchment and productivity in the lakes increased. Re-vegetation strategies introduced in the late 1990s caused an increase in arboreal taxa in the pollen record. This multi-proxy palaeoenvironmental study improves understanding of the long-term relationship between natural and anthropogenic environmental change in northeastern China.

Ombrotrophic bogs are widely used to reconstruct the history of atmospheric metal deposition. Minerotrophic fens are potential archives as well but not much attention has been paid to them. This study examined the accumulation of major and trace elements in a poor fen of Fenghuang Mountain, NE China. Peat cores were dated by 210Pb and 137Cs techniques and elemental analyses were conducted after a two-step sequential digestion with HCl. Results suggest no significant pollution for other trace metals but Pb in Fenghuang Mountain area. Atmospheric soil dust flux (ASD) was calculated from the Ti content in the peat, and its decreasing trend over the last 60 years agrees with the East Asian winter monsoon (EAWM) shift, which suggests that ASD could be a potential climatic proxy for the EAWM variability in the region.

Dust deposited on two ombrotrophic peat bogs (Baie and IDH bogs) of the St. Lawrence Gulf and Estuary north shore (Quebec) was geochemically characterized using rare earth element (REE) concentrations, Nd and Pb isotopes along with particle grain size. Both cores display similar ɛNd values, which suggests either a common source or sources with similar signatures in both regions. Combining Nd isotope data with REE patterns and particle size allowed for better insights into the source of deposited dust and the inference of past environmental and climatic conditions in both regions. REEs, ɛNd and grain-size distribution suggest that, over the last 2000 years, the Baie bog received more local dust due to increased local storminess in response to greater regional hydroclimatic variability. The same phenomenon occurred in the IDH bog since 620 cal a BP, i.e. during the Little Ice Age, where hydroclimatic and paleoecological changes have been previously documented. While the dust reconstructions and regional climatic records agree relatively well, the discrepancies between paleodust records highlight the complex and variable structure of late Holocene changes in paleoclimate and more particularly past dust deposition in eastern Canada.

Dust deposition in north-eastern Canada was estimated from the geochemical signature of a boreal peat bog from the James Bay lowlands. The rare earth elements and other lithogenic elements, as well as Nd isotopes were measured by Q-ICP-MS, ICP-OES and MC-ICP-MS, respectively along a 4.20 m peat core covering the last 7000 years. A principal component analysis performed on the geochemical dataset shows that REEs display the same chemical behavior as other lithogenic elements such as Al and Ti, which suggests that they are immobile in the peat column and can be used as tracers of dust deposition. After 4000 cal yr BP, peaks in dust deposition associated with greater variability in testate amoebae assemblages and plant macrofossil composition as well as a change in ɛNd values are observed. Between 7000 and 4100 cal yr BP, the ɛNd values varied from −36 to −29, while they gradually increased from 4100 cal yr BP until 1500 cal yr BP, suggesting proportionally less dust from local source(s) is deposited in favor of more regional source(s). From 1500 cal yr BP, ɛNd values remained relatively stable around −15 and −12. Most of the dust peaks correspond to documented cold and dry periods likely linked to intrusion of arctic air masses. A migration of the polar front might explain the more frequent intrusion of Arctic air masses in the region and the greater variability in the LG2 record over the last 4000 years.

Dust deposition in two ombrotrophic peatlands (Baie and Ile du Havre peatland (IDH) bogs) of the Estuary and Gulf of the St. Lawrence in eastern Canada was reconstructed using elemental geochemistry. The rare earth elements (REEs) and other lithogenic element concentrations were measured by ICP-oES and Q-ICP-MS along two peat cores spanning the last 4000 years. Principal component analyses on the geochemical profiles show that REEs display the same behavior as Al, Ti, Sc, and Zr, all conservative elements, which suggests that REEs are immobile in the studied peat bogs and can be used as tracers of dust deposition. Plant macrofossils were also used to infer past environmental and humidity changes. The dust fluxes were reconstructed using the sum of REEs (ΣREE). The range of dust deposition varies from 0.2 to 3.8 g m−2 yr−1 in the Baie bog, while the IDH bog shows lower fluxes ranging between 0.1 and 1.2 g m−2 yr−1. The highest dust fluxes in the Baie bog were recorded from 1750–1000 cal. BP to 600–100 cal. BP and occur at the same time as periods of high variability in the macrofossil record (i.e. successive layers dominated by Sphagnum or Ericaceae). The timing of these events in the dust and macrofossil records also corresponds to documented cold periods. These two periods have been identified as episodes of climatic instability, which could have been caused by changes in the wind regime.

The recent history of atmospheric As, Cd, Ni, Pb and Zn deposition and the stable Pb isotope signatures were reconstructed from short cores collected at three peat bogs along the St. Lawrence Valley (SLV). The onset of industrial activity was recorded around 1810–1850 AD. As, Cd, Pb and, to a certain extent, Ni deposition rates reached maxima between 1940 and the early 1970s. Trace metals likely originated from coal-burning and ore smelting between 1850 and 1950 AD, and were replaced thereafter, at least in the case of Pb, by the combustion of leaded gasolines until the mid-1980s. Trace metal contents and accumulation rates were greater in the two cores recovered from the southwestern SLV than further northeast, as expected from their proximity to urban and industrial centers of eastern Canada and the U.S. Mid-West and the direction of the prevalent winds. A rapid decrease in metal accumulation rates since the 1970s suggests that mitigation policies were effective in reducing atmospheric metal emissions. Nevertheless, metal accumulation rates and stable Pb isotope signatures have not yet returned to their pre-industrial values.