Defining the onset of the Anthropocene.

Twelve sites are considered for defining the Anthropocene geological epoch.

Anthropocene microplastic stratigraphy of Xiamen Bay, China: A history of plastic production and waste management.

Microplastics (MPs) are considered one of the significant stratigraphic markers of the onset of the Anthropocene Epoch; however, the interconnections between historic plastic production, waste management as well as social-economic and timing of MP accumulation are not well understood. Here, stratigraphic data of MPs from a sediment core from Xiamen Bay, China, was used to reconstruct the history of plastic pollution. Generalized Additive Modeling indicates a complex temporal evolution of MP accumulation. The oldest MPs deposited in 1952 was 30,332 ± 31,457 items/kg•dw, coincide with the infancy of the plastic industry and onset of the Anthropocene. The Cultural Revolution (1966-1976) curtailed these initial increases. Subsequent rapid growth in MPs during the late 1970s was peaked at 189,241 ± 29,495 items/kg•dw in 1988 and was followed by a drastic decline in the late 1980s to a low value in 1996 (16,626 ± 26,371 items/kg•dw), coinciding with proliferation of MP sources, coupled with evolution of plastic production, consumption, and regulation. Increasing MPs over the past decades implies that previous mitigation measures have been compromised by the escalated influx of MPs from increasing plastics production, legacy MPs remaining in circulation and insufficient waste management for a growing population. The present methodology and results represent a conceptual advance in understanding how changes in policy and economics over time correlate to changes in MP records in Anthropocene strata, which may help make decisions on plastic pollution mitigation strategies worldwide.

Natural archives of long-range transported contamination at the remote lake Letseng-la Letsie, Maloti Mountains, Lesotho.

Naturally accumulating archives, such as lake sediments and wetland peats, in remote areas may be used to identify the scale and rates of atmospherically deposited pollutant inputs to natural ecosystems. Co-located lake sediment and wetland cores were collected from Letseng-la Letsie, a remote lake in the Maloti Mountains of southern Lesotho. The cores were radiometrically dated and analysed for a suite of contaminants including trace metals and metalloids (Hg, Pb, Cu, Ni, Zn, As), fly-ash particles, stable nitrogen isotopes, polycyclic aromatic hydrocarbons (PAHs) and persistent organic pollutants such as polychlorinated biphenyls (PCBs), polybrominated flame retardants (PBDEs) and hexachlorobenzene (HCB). While most trace metals showed no recent enrichment, mercury, fly-ash particles, high molecular weight PAHs and total PCBs showed low but increasing levels of contamination since c.1970, likely the result of long-range transport from coal combustion and other industrial sources in the Highveld region of South Africa. However, back-trajectory analysis revealed that atmospheric transport from this region to southern Lesotho is infrequent and the scale of contamination is low. To our knowledge, these data represent the first palaeolimnological records and the first trace contaminant data for Lesotho, and one of the first multi-pollutant historical records for southern Africa. They therefore provide a baseline for future regional assessments in the context of continued coal combustion in South Africa through to the mid-21st century.

Palaeotoxicity: reconstructing the risk of multiple sedimentary pollutants to freshwater organisms.

'Real-world' contaminant exposure of sediment-dwelling biota is typically long-term, low-level and to multiple pollutants. However, sediment quality guidelines, designed to protect these organisms, relate only to single contaminants. This study uses radiometrically dated sediment cores from 7 English lakes with varying contamination histories to reconstruct temporal changes in likely risk to biota (herein termed 'palaeotoxicity'). The Probable Effects Concentration Quotient (PEC-Q) approach was used to combine sediment concentrations from multiple contaminants (trace metals; PCBs; PBDEs) to determine risk allocated to metals and persistent organic pollutants (POPs) separately as well as combined (PEC-Q Mean-All). Urban-influenced lakes were considerably more contaminated, exceeding PEC-Q thresholds of 0.5 and 2.0 over long durations (some since the nineteenth century). This has been mainly due to metals (principally lead) and by factors of up to 10 for individual metals and by > 2 for PEC-Q Mean-Metals. In 6 out of 7 lakes, considerable reductions in risk associated with trace metals are observed since emissions reductions in the 1970s. However, at all lakes, PEC-Q Mean-POPs has increased sharply since the 1950s and at 5 out of 7 lakes now exceeds PEC-Q Mean-Metals. These organic pollutants are therefore now the dominant driver behind elevated contaminant risk to sediment-dwelling biota and recent temporal trends in PEC-Q Mean-All remain above threshold values as a result. Finally, PEC-Q Mean-All values were compared to standard biological toxicity tests for surface sediments at each site. While chironomid growth and daphniid reproduction were significantly reduced compared to controls at 5 out of 7, and all lakes, respectively, the scale of these reductions showed only limited quantitative agreement with predicted risk.

Microplastics in the sediments of a UK urban lake.

While studies on microplastics in the marine environment show their wide-distribution, persistence and contamination of biota, the freshwater environment remains comparatively neglected. Where studies on freshwaters have been undertaken these have been on riverine systems or very large lakes. We present data on the distribution of microplastic particles in the sediments of Edgbaston Pool, a shallow eutrophic lake in central Birmingham, UK. These data provide, to our knowledge, the first assessment of microplastic concentrations in the sediments of either a small or an urban lake and the first for any lake in the UK. Maximum concentrations reached 25-30 particles per 100 g dried sediment (equivalent to low hundreds kg-1) and hence are comparable with reported river sediment studies. Fibres and films were the most common types of microplastic observed. Spatial distributions appear to be due to similar factors to other lake studies (i.e. location of inflow; prevailing wind directions; propensity for biofouling; distribution of macroplastic debris) and add to the growing burden of evidence for microplastic ubiquity in all environments.

Hexabromocyclododecanes, polybrominated diphenyl ethers, and polychlorinated biphenyls in radiometrically dated sediment cores from English lakes, ~1950-present.

This paper reports input fluxes between ~1950 and present, of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecanes (HBCDs) in radiometrically-dated sediment cores from 7 English lakes. Fluxes of PCBs at all but one location prone to significant sediment resuspension peaked in the late-1960s/early-1990s, before declining thereafter. Input fluxes of HBCDs at all sites increased from first emergence in the mid-1960s. Thereafter, fluxes peaked in the late-1980s/early-2000s, before declining through to the present, except at the most urban site where HBCD fluxes are still increasing. Trends of PBDEs predominant in the Penta-BDE and Octa-BDE formulations vary between sites. While at some locations, fluxes peaked in the late-1990s/early-2000s; at others, fluxes are still increasing. This suggests the full impact of EU restrictions on these formulations has yet to be felt. Fluxes of BDE-209 have yet to peak at all except one location, suggesting little discernible environmental response to recent EU restrictions on the Deca-BDE product. Strikingly, fluxes of BDE-209 in the most recent core slices either exceed or approach peak fluxes of ΣPCBs, implying substantial UK use of Deca-BDE. Excepting HBCDs, inventories of our target contaminants correlated significantly with local population density, implying substantial urban sources.

A gradient of mercury concentrations in Scottish single malt whiskies.

Mercury (Hg) concentrations were measured in 26 Scottish single malt whiskies, and all found to be very low (<10 ng L(-1)), posing no threat to human health through reasonable levels of consumption. However, a significant south-to-north declining gradient in Hg concentrations was observed reflecting that reported for atmospheric deposition. We speculate that this gradient could be due to a combination of contemporary deposition and the legacy of industrial mercury emissions and deposition over the last 200 years affecting concentrations in local waters used in whisky production. As UK atmospheric emissions of mercury have declined by 90 % since the 1970s, we suggest that whisky being produced today should have even lower Hg concentrations when consumed in 10- to 15-years time. This reduction may be compromised by the remobilisation of contaminants stored in catchment soils being transferred to source waters, but is very unlikely to raise the negligible health risk due to Hg from Scottish single malt whisky consumption.

Polybrominated diphenyl ethers (PBDEs) in English freshwater lakes, 2008-2012.

Concentrations of tri-to-hexa-BDEs were determined in water samples taken from 9 English lakes on 13 occasions between April 2008 and February 2012. Across all sites, concentrations of ΣBDEs in individual samples ranged from 9.2 to 171.5pgL(-)(1), with an average of 61.9pgL(-)(1). Notwithstanding the far greater use of the Penta-BDE commercial formulation in the USA, concentrations in this study are comparable to the limited data available for the Great Lakes. PBDE concentrations showed no evidence of a decline at any monitored location over the study period. This may be because this study commenced 4years after the introduction of restrictions on the Penta- and Octa-BDE formulations. While concentrations normalised to water volume at the different locations were statistically indistinguishable; significant spatial variation was apparent when the data were normalised to total suspended solids (TSS) content. However, this spatial variation was not correlated with factors such as population density and lake catchment area, suggesting that concentrations of PBDEs in lake water in this study are a complex integral of numerous factors. BDE-47:99 ratios and concentrations of ΣBDEs respectively decreased and increased significantly with increasing TSS content. As TSS content was elevated in colder compared with warmer periods, such seasonal variation in TSS content appears a major contributor to the observed elevation of ΣBDE concentrations in colder periods, and higher BDE-47:99 ratios in warmer periods.

Stable isotopes trace estuarine transformations of carbon and nitrogen from primary- and secondary-treated paper and pulp mill effluent.

Stable isotope analysis of a novel combination of carbon and nitrogen pools traced inputs and processing of primary-treated (PE) and secondary-treated effluent (SE) from a paper and pulp mill (PPM) in a temperate Australian estuary. Distinct carbon stable isotope ratios of dissolved organic carbon (DOC) near the PPM outfall indicated large PE and reduced SE inputs of DOC. DOC was remineralized to dissolved inorganic carbon regardless of season, but rates were lower in winter. PE discharge in winter elevated DOC concentrations along much of the estuary. Distinct stable isotope ratios confirmed particulate organic matter (POM) input from PE and SE to the water column and into the sediment. This was relatively localized, indicating rapid POM settlement regardless of season. SE discharge increased nutrient inputs and enhanced algal productivity, particularly in summer when chlorophyll-a concentrations were elevated throughout the estuary. SE discharge reduced pCO(2) from levels associated with PE discharge. However, the estuary remained heterotrophic as subsequent respiration or decomposition of algal material offset reductions in PPM organic matter input. The influence of the PPM was apparent throughout the estuary, demonstrating the ability of anthropogenic inputs, and changes to these, to affect ecosystem functioning.

Historical reconstruction of mercury pollution across the Tibetan Plateau using lake sediments.

The Tibetan Plateau is described as the "Roof of the World" averaging over 4000 m above sea level; it is remote, isolated, and presumed to be a pristine region. In order to study the history of atmospheric mercury (Hg) pollution and its spatial variation across the Plateau, lakes were chosen from three areas forming a north to south transect. Sediment cores were taken from three sites in each area and dated using the radionuclides 210Pb and 137Cs. Analysis of the cores yielded the first comprehensive Hg reconstructions for the Plateau, showing clear Hg pollution at all sites. The first indication of Hg pollution is much earlier than the onset of the industrial revolution in Europe, but the most significant pollution increase is from the 1970s, followed by a further marked increase from the 1990s. The mean post-2000 atmospheric pollution Hg accumulation rates for the sampling sites were estimated at between 5.1 and 7.9 microg m(-2) yr(-1). The increase in Hg pollution over the last few decades is synchronous with the recent economic development in Asia (especially China and India), and pollution Hg levels continue to increase. Furthermore, contemporary sediment Hg accumulation rate data are in broad agreement with Hg deposition values derived from global models that attribute pollution to sources mainly within southeast Asia. As most of the sites are exceptionally remote and situated above the atmospheric boundary layer, these results underline the need to understand the local Hg cycle in both regional and global context.

Current-use brominated flame retardants in water, sediment, and fish from English lakes.

Concentrations are reported of hexabromocyclododecanes (HBCDs) and tetrabromobisphenol-A (TBBP-A) in water (n = 27), sediment (n = 9), and fish samples (n = 30) from nine English lakes. Seasonal variation in concentrations in water is minimal. Concentrations of TBBP-A range from 140 to 3200 pg L(-1) (water), 330 to 3800 pg g(-1) dry weight (sediment), and <0.29 to 1.7 ng g(-1) lipid weight (fish). Those of SigmaHBCDs range between 80 and 270 pg L(-1) (water), 880 and 4800 pg g(-1) dry weight (sediment), and 14 and 290 ng g(-1) lipid weight (fish). Aqueous concentrations of SigmaHBCDs and TBBP-A are significantly positively correlated, indicating a common source. Average +/-sigma(n) "freely-dissolved" phase proportions are 47 +/- 4.7% (SigmaHBCDs) and 61 +/- 2.9% (TBBP-A). Average field-derived bioaccumulation factors are 5900, 1300, 810, and 2100 for alpha-, beta-, gamma-, and SigmaHBCDs, respectively. Tetrabromocyclododecadienes are detected in all sediments, with pentabromocyclododecenes present in some. This suggests HBCD degrades via sequential loss of HBr. The delta-HBCD meso form was quantified in 43% of fish samples (1.0-11% SigmaHBCDs). Its absence from temporally and spatially consistent water and sediment samples suggests it is formed via bioisomerization. While HBCD chiral signatures are racemic in water and sediment, our data reveal enantiomeric enrichment of (-)alpha-HBCD and (+)gamma-HBCD in fish.