Atmospheric Pb deposition was reconstructed using peat cores from bogs in the vicinity of Flin Flon, Manitoba, Canada, home to a zinc refinery and copper smelter. The Sask Lake (SL4-1) core was collected 85 km NW of Flin Flon and Kotyk Lake (KOL) 30 km NE. The distribution of Sr and U show that both profiles are predominantly minerotrophic (ie groundwater-fed), but the Pb concentration profile shows that Pb was received exclusively from the atmosphere. Graphs of 208Pb/206Pb against 206Pb/207Pb document atmospheric Pb contamination dating from the early to mid-1800’s, well before the start of metallurgical processing (in 1930) and attributable to long-range atmospheric transport from other regions of North America. Industrial activities at Flin Flon clearly affected the concentrations, enrichment factor (calculated using Sc), and accumulation rates of Pb, but it is the similarity in isotopic composition, and contrast with crustal values (206Pb/207Pb ca. 1.20 to 1.22) which makes the connection to the Flin Flon ores. The KOL samples dating from 1925–1976 CE have a 206Pb/207Pb of 1.032 ± 0.002 (n = 11) which approach the values for the Flin Flon ores (206Pb/207Pb = 1.008). But even at SL4-1, the peat samples dating from 1925–1976 CE have a 206Pb/207Pb of 1.061 ± 0.022 (n = 18) which is well below the corresponding ratio of Canadian leaded gasoline (206Pb/207Pb = ca. 1.15). The SL4-1 site too, therefore, was clearly impacted by Pb from mining and metallurgy, despite the distance (88 km) from Flin Flon and being predominantly upwind. These two bogs not only provide the chronology of atmospheric Pb deposition for the past decades, but suggest that the extent of contamination may have been underestimated by previous studies.

There is an ongoing debate on the fate of mercury (Hg) in areas affected by artisanal and small-scale gold mining (ASGM). Over the last 30 years, ASGM has released 69 tons of Hg into the southeastern Peruvian Amazon. To investigate the role of suspended matter and hydrological factors on the fate of ASGM-Hg, we analysed riverbank sediments and suspended matter along the partially ASGM-affected Malinowski-Tambopata river system and examined Hg accumulation in fish. In addition, local impacts of atmospheric Hg emissions on aquatic systems were assessed by analysing a sediment core from an oxbow lake. Hg concentrations in riverbank sediments are lower (20–53 ng g−1) than in suspended matter (∼400–4000 ng g−1) due to differences in particle size. Elevated Hg concentrations in suspended matter from ASGM-affected river sections (∼1400 vs. ∼30–120 ng L−1 in unaffected sections) are mainly driven by the increased amount of suspended matter rather than increased Hg concentrations in the suspended matter. The oxbow lake sediment record shows low Hg concentrations (64–86 ng g−1) without evidence of any ASGM-related increase in atmospheric Hg input. Hg flux variations are mostly an effect of variations in sediment accumulation rates. Moreover, only 5% of the analysed fish (only piscivores) exceed WHO recommendations for human consumption (500 ng g−1). Our findings show that ASGM-affected river sections in the Malinowski-Tambopata system do not exhibit increased Hg accumulation, indicating that the released Hg is either retained at the spill site or transported to areas farther away from the ASGM areas. We suspect that the fate of ASGM-Hg in such tropical rivers is mainly linked to transport associated with the suspended matter, especially during high water situations. We assume that our findings are typical for ASGM-affected areas in tropical regions and could explain why aquatic systems in such ASGM regions often show comparatively modest enrichment in Hg levels.

Oxidative potential (OP) of particulate matter (PM) − defined as the capacity of PM to oxidize target molecules generating reactive oxygen species (ROS) − has been proposed as a more health relevant metric than PM mass. In this study two cell-free methods were used to assess the OP of PM filters collected at an urban site and to evaluate correlation with PM mass and PM composition.Among the different assays existing, two inexpensive and user-friendly methods were used both based on spectrophotometric measurements of depletion rate of target reagents oxidized by redox-active species present in PM. One assay measures the consumption of dithiothreitol (OPDTT) and the other the ascorbate (OPAA).Although both assays respond to the same redox-active species, i.e., quinones and transition metals, no correlations were found between OPDTT and OPAA responses to compounds standard solutions as well as to ambient samples. When expressed in relation to air volume, OPDTT m−3 strongly correlates with PM2.5 mass whereas no correlation was found for OPAA m−3 with PM2.5. When expressed on mass basis, both OPDTT μg−1 and OPAA μg−1 show a strong dependence on the sample composition, with higher OP for summer samples. OPDTT m−3 were highly correlated with the determined metals (Cu, Zn, Cr, Fe, Ni, Mn) whereas OPAA m−3 showed only moderate correlation with Cu and Mn.Thus, the two assays could potentially provide complementary information on oxidative potential characteristic of PM. Consequently, the combination of the two approaches can strengthen each other in giving insight into the contribution of chemical composition to oxidative properties of PM, which can subsequently be used to study health effects.

In addition to their active ingredients, pesticides contain also additives – surfactants. Use of surfactants has been increasing over the past decade, but their effects on non-target organisms, especially natural enemies of pests, have been studied only very rarely. The effect of three common agrochemical surfactants on the foraging behavior of the wolf spider Pardosa agrestis was studied in the laboratory. Differences in short-term, long-term, and overall cumulative predatory activities were investigated. We found that surfactant treatment significantly affected short-term predatory activity but had no effect on long-term predatory activity. The surfactants also significantly influenced the cumulative number of killed prey. We also found the sex-specific increase in cumulative kills after surfactants treatment. This is the first study showing that pesticide additives have a sublethal effect that can weaken the predatory activity of a potential biological control agent. More studies on the effects of surfactants are needed to understand how they affect beneficial organisms in agroecosystems.

Ingestion of soot present in soil or other environmental particles is expected to be an important route of exposure to nitro and oxygenated derivatives of polycyclic aromatic hydrocarbons (PAHs). We measured the apparent bioaccessibility (Bapp) of native concentrations of 1-nitropyrene (1N-PYR), 9-fluorenone (9FLO), anthracene-9,10-dione (ATQ), benzo[a]anthracene-7,12-dione (BaAQ), and benzanthrone (BZO) in a composite fuel soot sample using a previously-developed in vitro human gastrointestinal model that includes silicone sheet as a third-phase absorptive sink. Along with Bapp, we determined the 24-h sheet-digestive fluid partition coefficient (Ks,24h), the soot residue-fluid distribution ratio of the labile sorbed fraction after digestion (Kr,lab), and the maximum possible (limiting) bioaccessibility, Blim. The Bapp of PAH derivatives was positively affected by the presence of the sheet due to mass-action removal of the sorbed compounds. In all cases Bapp increased with imposition of fed conditions. The enhancement of Bapp under fed conditions is due to increasingly favorable mass transfer of target compounds from soot to fluid (increasing bile acid concentration, or adding food lipids) or transfer from fluid to sheet (by raising small intestinal pH). Food lipids may also enhance Bapp by mobilizing contaminants from nonlabile to labile states of the soot. Compared to the parent PAH, the derivatives had larger Kr,lab, despite having lower partition coefficients to various hydrophobic reference phases including silicone sheet. The Blim of the derivatives under the default conditions of the model ranged from 65.5% to 34.4%, in the order, 1N-PYR > ATQ > 9FLO > BZO > BaAQ, with no significant correlation with hydrophobic parameters, nor consistent relationship with Blim of the parent PAH. Consistent with earlier experiments on a wider range of PAHs, the results suggest that a major determinant of bioaccessibility is the distribution of chemical between nonlabile and labile states in the original solid.

Mass transfer of hydrophobic organic contaminants (HOCs) across the air-water interface is an important geochemical process controlling the fate and transport of HOCs at the regional and global scales. However, few studies have characterized concentration or fugacity profiles of HOCs near both sides of the air-water interface, which is the driving force for the inter-compartmental mass transfer of HOCs. Herein, we introduce a novel passive sampling device which is capable of measuring concentration (and therefore fugacity) gradients of HOCs across the air-water interface. Laboratory studies indicated that the escaping fugacity values of polycyclic aromatic hydrocarbons (PAHs) from water to air were negatively correlated to their volatilization half-lives. Results for field deployment were consistent between the passive sampler and an active method, i.e., a combination of grab sampling and liquid-liquid extraction. In general, the fugacity profiles of detected PAHs were indicative of an accumulation mechanism in the surface microlayer of the study regions (Haizhu Lake and Hailing Bay of Guangdong Province, China), while p,p'-DDD tended to volatilize from water to the atmosphere in Hailing Bay. Furthermore, the fugacity profiles of the target analytes increased towards the air-water interface, reflecting the complexity of environmental behavior of the target analytes near the air-water interface. Overall, the passive sampling device provides a novel means to better characterize the air-water diffusive transfer of HOCs, facilitating the understanding of the global cycling of HOCs.

The worldwide use of pesticides has led to increases in agricultural yields by reducing crop losses. However, increased pesticide use has resulted in pesticide-resistant pest species and recent studies have discovered pesticide-resistance in non-target species living close to farms. Such increased tolerance not only affects the species, but can alter the entire food web. Given that some species can evolve not only resistance to a single pesticide, but also cross-resistance to other pesticides that share the same mode of action, one would predict that cross-resistance to pesticides would also have effects on the entire community and affect community stability. To address this hypothesis, we conducted an outdoor mesocosm experiment comprised of 200 identical aquatic communities with phytoplankton, periphyton, and leopard frog (Lithobates pipiens) tadpoles. To these communities, we added one of four Daphnia pulex populations that we previously discovered were either resistant or sensitive to the insecticide of chlorpyrifos as a result of living close to or far from agriculture, respectively. We then exposed the communities to either no insecticide or three different concentrations of AChE-inhibiting insecticides (chlorpyrifos, malathion or carbaryl) or sodium channel-inhibiting insecticides (permethrin or cypermethrin). We discovered that communities containing sensitive Daphnia pulex experienced phytoplankton blooms and subsequent cascades through all trophic groups including amphibians at moderate to high concentrations of all five insecticides. However, communities containing resistant D. pulex were buffered from these effects at low to moderate concentrations of all AChE-inhibiting insecticides, but were not buffered against the pyrethroid insecticides. These data suggest that a simple change in the population-level resistance of zooplankton to a single insecticide can have widespread consequences for community stability and that the effects can be extrapolated to a wide variety of pesticides that share the same mode of action.

The effects of polystyrene microbeads (micro-PS; mix of 2 and 6 μm; final concentration: 32 μg L−1) alone or in combination with fluoranthene (30 μg L−1) on marine mussels Mytilus spp. were investigated after 7 days of exposure and 7 days of depuration under controlled laboratory conditions. Overall, fluoranthene was mostly associated to algae Chaetoceros muelleri (partition coefficient Log Kp = 4.8) used as a food source for mussels during the experiment. When micro-PS were added in the system, a fraction of FLU transferred from the algae to the microbeads as suggested by the higher partition coefficient of micro-PS (Log Kp = 6.6), which confirmed a high affinity of fluoranthene for polystyrene microparticles. However, this did not lead to a modification of fluoranthene bioaccumulation in exposed individuals, suggesting that micro-PS had a minor role in transferring fluoranthene to mussels tissues in comparison with waterborne and foodborne exposures. After depuration, a higher fluoranthene concentration was detected in mussels exposed to micro-PS and fluoranthene, as compared to mussels exposed to fluoranthene alone. This may be related to direct effect of micro-PS on detoxification mechanisms, as suggested by a down regulation of a P-glycoprotein involved in pollutant excretion, but other factors such as an impairment of the filtration activity or presence of remaining beads in the gut cannot be excluded. Micro-PS alone led to an increase in hemocyte mortality and triggered substantial modulation of cellular oxidative balance: increase in reactive oxygen species production in hemocytes and enhancement of anti-oxidant and glutathione-related enzymes in mussel tissues. Highest histopathological damages and levels of anti-oxidant markers were observed in mussels exposed to micro-PS together with fluoranthene. Overall these results suggest that under the experimental conditions of our study micro-PS led to direct toxic effects at tissue, cellular and molecular levels, and modulated fluoranthene kinetics and toxicity in marine mussels.

Microplastics have been reported everywhere around the globe. With very limited human activities, the Arctic is distant from major sources of microplastics. However, microplastic ingestions have been found in several Arctic marine predators, confirming their presence in this region. Nonetheless, existing information for this area remains scarce, thus there is an urgent need to quantify the contamination of Arctic marine waters. In this context, we studied microplastic abundance and composition within the zooplankton community off East Greenland. For the same area, we concurrently evaluated microplastic contamination of little auks (Alle alle), an Arctic seabird feeding on zooplankton while diving between 0 and 50 m. The study took place off East Greenland in July 2005 and 2014, under strongly contrasted sea-ice conditions. Among all samples, 97.2% of the debris found were filaments. Despite the remoteness of our study area, microplastic abundances were comparable to those of other oceans, with 0.99 ± 0.62 m−3 in the presence of sea-ice (2005), and 2.38 ± 1.11 m−3 in the nearby absence of sea-ice (2014). Microplastic rise between 2005 and 2014 might be linked to an increase in plastic production worldwide or to lower sea-ice extents in 2014, as sea-ice can represent a sink for microplastic particles, which are subsequently released to the water column upon melting. Crucially, all birds had eaten plastic filaments, and they collected high levels of microplastics compared to background levels with 9.99 and 8.99 pieces per chick meal in 2005 and 2014, respectively. Importantly, we also demonstrated that little auks took more often light colored microplastics, rather than darker ones, strongly suggesting an active contamination with birds mistaking microplastics for their natural prey. Overall, our study stresses the great vulnerability of Arctic marine species to microplastic pollution in a warming Arctic, where sea-ice melting is expected to release vast volumes of trapped debris.

Studying long-term trends of contaminants in Arctic biota is essential to better understand impacts of anthropogenic activities and climate change on the exposure of sensitive species and marine ecosystems. We concurrently measured temporal changes (2006–2014) in mercury (Hg) contamination of little auks (Alle alle; the most abundant Arctic seabird) and in their major zooplankton prey species (Calanoid copepods, Themisto libellula, Gammarus spp.). We found an increasing contamination of the food-chain in East Greenland during summer over the last decade. More specifically, bird contamination (determined by body feather analyses) has increased at a rate of 3.4% per year. Conversely, bird exposure to Hg during winter in the northwest Atlantic (determined by head feather analyses) decreased over the study period (at a rate of 1.5% per year), although winter concentrations remained consistently higher than during summer. By combining mercury levels measured in birds and zooplankton to isotopic analyses, our results demonstrate that inter-annual variations of Hg levels in little auks reflect changes in food-chain contamination, rather than a reorganization of the food web and a modification of seabird trophic ecology. They therefore underline the value of little auks, and Arctic seabirds in general, as bio-indicators of long-term changes in environmental contamination.