An ecosystem in a cold climate river basin is vulnerable to the effects of climate change affecting permafrost thaw and glacier retreat. We currently lack sufficient data and information if and how hydrological processes such as glacier retreat, snowmelt and freezing-thawing affect sediment and nutrient runoff and transport, as well as N₂O emissions in cold climate river basins. As such, we have implemented well-established, semi-empirical equations of nitrification and denitrification within the Soil and Water Assessment Tool (SWAT), which correlate the emissions with water, sediment and nutrients. We have tested this implementation to simulate emission dynamics at three sites on the Canadian prairies. We then regionalized the optimized parameters to a SWAT model of the Athabasca River Basin (ARB), Canada, calibrated and validated for streamflow, sediment and water quality. In the base period (1990–2005), agricultural areas (2662 gN/ha/yr) constituted emission hot-spots. The spring season in agricultural areas and summer season in forest areas, constituted emission hot-moments. We found that warmer conditions (+13% to +106%) would have a greater influence on emissions than wetter conditions (−19% to +13%), and that the combined effect of wetter and warmer conditions would be more offsetting than synergetic. Our results imply that the spatiotemporal variability of N₂O emissions will depend strongly on soil water changes caused by permafrost thaw. Early snow freshet leads to spatial variability of soil erosion and nutrient runoff, as well as increases of emissions in winter and decreases in spring. Our simulations suggest crop residue management may reduce emissions by 34%, but with the mixed results reported in the literature and the soil and hydrology problems associated with stover removal more research is necessary. This modelling tool can be used to refine bottom-up emission estimations at river basin scale, test plausible management scenarios, and assess climate change impacts including climate feedback.

It is critical to estimate the exposure to indoor air pollution of residents spending most of their time in such microenvironments. However, the understanding regarding PM2.5 exposure in residential indoor environments is very limited. In this study, we collected participants' basic information and time–activity patterns, as well as details of other factors related to indoor air pollution exposure, through questionnaires presented to a large population in 37 counties of China. Continuous monitoring of ambient PM2.5 concentrations was performed using an environmental fixed-site monitoring network. Residential indoor PM2.5 concentrations were predicted using a mass balance model based on the data obtained. Evaluation of continuous daily average residential indoor PM2.5 exposure doses for large populations during winter revealed concentrations ranged from 67 to 195 μg/m3. Finally, differences in residential indoor PM2.5 exposure between northern and southern China were investigated. The results suggested that residential indoor PM2.5 concentrations in northern China, associated with heating, were higher than in the south. The established model could be important for improved understanding of human exposure to indoor PM2.5 air pollution.

Solid fuels, an important source of severe Household Air Pollution (HAP) linked to many adverse health outcomes, has been widely consumed around the world. China consumes large amounts of solid fuels and suffers from serious indoor and outdoor air pollution. Though global HAP issues had been reviewed in previous literatures, peer-reviewed Chinese publications were seldom included in those reviews. We conducted a literature review on the studies of HAP and personal exposure in rural China with inputs from peer-reviewed publications in both English and Chinese. A total of 36,572 articles were retrieved, 294 were read in full text, of which 92 were included in final data extraction and in-depth analysis. Although HAP is a very serious issue in China, studies on either HAP or personal exposure assessment were very limited. From existing studies, levels of air pollutants including carbon monoxide, sulfur dioxide, particulate matter (PM), organic carbon, elemental carbon, polycyclic aromatic hydrocarbons (PAHs), etc., in indoor and ambient air were analyzed for their temporal and spatial variations, and the differences across different fuel types were compared. The studies showed that PM and PAHs levels in most rural homes exceeded the World Health Organization (WHO) and Chinese National Standards, especially during the heating season in northern China. Replacing traditional fuels with cleaner ones (such as liquid petroleum gas (LPG), biogas or electricity) was considered as the most appropriate way to mitigate HAP. The daily exposure to PM and PAHs from using LPG, biogas or electricity was considerably lower than that from using traditional solid fuels. However, the level was still higher than the guideline values for PM and PAHs set by WHO to protect human health. To achieve a more effective control, the current data gap need to be closed and suggestions for future research were discussed in this review.

Studying the characteristics of new particle formation (NPF) is important as it is generally recognized as a major contributor to particle pollution in urban environments. We investigated NPF events that occurred during a 1-year period in the urban environment of Brisbane, Australia, using a neutral cluster and air ion spectrometer (NAIS) which is able to monitor both neutral and charged particles and clusters down to a size of 0.8 nm. NPF events occurred on 41% of days, with the occurrence rate of 7% greater in the summer than in the winter. We derived the first diurnal event distribution of NPF events anywhere in the world and showed that the most probable starting time of an NPF event was near 08:30 a.m., being about an hour earlier in the winter than in the summer. During NPF days, 10% of particles were charged. The mean neutral and charged particle concentrations on NPF days were, respectively, 49% and 14% higher than those on non-event days. The mean formation rate of 2–3 nm particles during an NPF event was 20.8 cm⁻³ s⁻¹. The formation rate of negatively charged particles was about 10% higher than that of positively charged particles. The mean particle growth rate in the size range up to 20 nm was 6.2 nm h⁻¹. These results are compared and contrasted with corresponding values that have been derived with the scanning mobility particle sizer (SMPS) at the same location and with values that have been reported with the NAIS at other locations around the world. This is the first comprehensive study of the characteristics of NPF events over a significantly long period in Australia.

PM₁ might be more hazardous than PM₂.₅ (particulate matter with an aerodynamic diameter ≤ 1 μm and ≤2.5 μm, respectively). However, studies on PM₁ concentrations and its health effects are limited due to a lack of PM₁ monitoring data.To estimate spatial and temporal variations of PM₁ concentrations in China during 2005–2014 using satellite remote sensing, meteorology, and land use information.Two types of Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6 aerosol optical depth (AOD) data, Dark Target (DT) and Deep Blue (DB), were combined. Generalised additive model (GAM) was developed to link ground-monitored PM₁ data with AOD data and other spatial and temporal predictors (e.g., urban cover, forest cover and calendar month). A 10-fold cross-validation was performed to assess the predictive ability.The results of 10-fold cross-validation showed R² and Root Mean Squared Error (RMSE) for monthly prediction were 71% and 13.0 μg/m³, respectively. For seasonal prediction, the R² and RMSE were 77% and 11.4 μg/m³, respectively. The predicted annual mean concentration of PM₁ across China was 26.9 μg/m³. The PM₁ level was highest in winter while lowest in summer. Generally, the PM₁ levels in entire China did not substantially change during the past decade. Regarding local heavy polluted regions, PM₁ levels increased substantially in the South-Western Hebei and Beijing-Tianjin region.GAM with satellite-retrieved AOD, meteorology, and land use information has high predictive ability to estimate ground-level PM₁. Ambient PM₁ reached high levels in China during the past decade. The estimated results can be applied to evaluate the health effects of PM₁.

We discuss 15 years (2000–2015) of daily-integrated PM₂.₅ samples from the Cape Grim Station. Ion beam analysis and positive matrix factorisation are used to identify six source-type fingerprints: fresh sea salt (57%); secondary sulfate (14%); smoke (13%); aged sea salt (12%); soil dust (2.4%); and industrial metals (1.5%). An existing hourly radon-only baseline selection technique is modified for use with the daily-integrated observations. Results were not significantly different for days on which >20 hours were below the baseline radon threshold compared with days when all 24 hours satisfied the baseline criteria. This relaxed daily baseline criteria increased the number of samples for analysis by almost a factor of two. Two radon baseline thresholds were tested: historic (100 mBq m⁻³), and revised (50 mBq m⁻³). Median aerosol concentrations were similar for both radon thresholds, but maximum values were higher for the 100 mBq m⁻³ threshold. Back trajectories indicated more interaction with southern Australia and the Antarctic coastline for air masses selected with the 100 mBq m⁻³ threshold. Radon-only baseline selection using the 50 mBq m⁻³ threshold was more selective of minimal terrestrial influence than a similar recent study using wind direction and back trajectories. The ratio of concentrations between terrestrial and baseline days for the primary sources soil, smoke and industrial metals was 3.4, 2.6, and 5.5, respectively. Seasonal cycles of soil dust had a summer maximum and winter minimum. Seasonal cycles of smoke were of similar amplitude for terrestrial and baseline events, but of completely different shape: peaking in autumn and spring for terrestrial events, compared to summer for baseline conditions. Seasonal cycles of industrial metals had a summer maximum and winter minimum. A significant fraction of the Cape Grim baseline smoke and industrial metal contributions appeared to be derived from long-term transport (>3 weeks since last terrestrial influence).

Mass concentrations of chemical compounds in both PM2.5 (particle aerodynamic diameter, Dp < 2.5 μm) and PM2.5-10 (2.5 < Dp < 10 μm), and acidity of aerosol particles were measured at an urban site in western Japan using a continuous dichotomous Aerosol Chemical Speciation Analyzer (ACSA-12) throughout 2014. Mass concentrations of both PM2.5 and sulfate had distinct seasonal variabilities with maxima in spring and winter, mostly due to long-range transport with the prevailing westerly wind. Mass concentration of nitrate in PM2.5 (fNO3) showed an obvious warm-season-low and cold-season-high pattern as a result of both gas-aerosol phase equilibrium processes under high temperature conditions as well as transport. Nitrate in PM2.5-10 (cNO3) increased during long-range transport of dust, implying the great importance of heterogeneous processes at the surface of coarse mode particles. In this study, Δ[H+] (derived from the difference in pH of extract liquid with/without sampling) was used to indicate the acidity of particles. We found that acidity of particles in PM2.5 (fΔH) was mostly positive with a maximum in August because of the large fraction of nitrate and sulfate. Acidity of particles in PM2.5-10 (cΔH) was negative in winter and spring due to presence of alkaline matter from crustal sources. This study highlights the great importance of anthropogenic pollutants on the acidity of particles in the western Pacific Ocean and further impact on the marine environment and climate.

Mercury (Hg) is a potent neurotoxicant known to induce important adverse effects on fish, but a deeper understanding is lacking regarding how environmental exposure affects the brain morphology and neural plasticity of specific brain regions in wild specimens. In this work, it was evaluated the relative volume and cell density of the lateral pallium, hypothalamus, optic tectum and molecular layer of the cerebellum on wild Liza aurata captured in Hg-contaminated (LAR) and non-contaminated (SJ) sites of a coastal system (Ria de Aveiro, Portugal). Given the season-related variations in the environment that fish are naturally exposed, this assessment was performed in the winter and summer. Hg triggered a deficit in cell density of hypothalamus during the winter that could lead to hormonal dysfunctions, while in the summer Hg promoted larger volumes of the optic tectum and cerebellum, indicating the warm period as the most critical for the manifestation of putative changes in visual acuity and motor-dependent tasks. Moreover, in fish from the SJ site, the lateral pallium relative volume and the cell density of the hypothalamus and optic tectum were higher in the winter than in summer. Thus, season-related stimuli strongly influence the size and/or cell density of specific brain regions in the non-contaminated area, pointing out the ability of fish to adapt to environmental and physiological demands. Conversely, fish from the Hg-contaminated site showed a distinct seasonal profile of brain morphology, presenting a larger optic tectum in the summer, as well as a larger molecular layer of the cerebellum with higher cell density. Moreover, Hg exposure impaired the winter-summer variation of the lateral pallium relative size (as observed at SJ). Altogether, seasonal variations in fish neural morphology and physiology should be considered when performing ecotoxicological studies in order to better discriminate the Hg neurotoxicity.

In this study, we conducted an assessment of polyurethane foam (PUF) passive sampling for metals combining active sampling. Remarkably, we found that the metals collected in the passive samples differed greatly from those collected in active samples. By composition, Cu and Ni accounted for significantly higher proportions in passive samples than in active samples, leading to significantly higher uptake rates of Cu and Ni. In assessing seasonal variation, metals in passive samples had higher concentrations in summer (excluding Heshan), which differed greatly from the pattern of active samples (winter > summer), indicating that the uptake rates of most metals were higher in summer than in winter. Overall, due to the stable passive uptake rates, we considered that PUF passive samplers can be applied to collect atmospheric metals. Additionally, we created a snapshot of the metal pollution in the Pearl River Delta using principal component analysis of PUF samples and their source apportionment.

By identifying the main sources of nitrate (NO3−) can obtain useful information to support the management of NO3− pollution, particularly in subtropical catchments with shallow drinking water wells. This study used water chemistry and dual stable isotopes δ15N and δ18O methods to assess seasonal and spatial variations of NO3− in precipitation, surface water, and groundwater in an agricultural and forest subtropical catchment in Jiangxi Province, China. The maximum concentrations of nitrate-nitrogen (NO3−-N) and ammonium-nitrogen (NH4+-N) were 10.4 and 10.8 mg L−1in samples collected from 221 rainfall events from 2011 to 2013. About 4.4% and 12.3% NH4+-N concentrations of surface water and groundwater exceeded the thresholds of 1.0 and 0.2 mg L−1. The NO3−-N concentrations in surface water were closely correlated with NH4+-N concentrations in surface water and groundwater (r = −0.71 and r = −0.71, P < 0.05). The concentrations of NH4+-N and NO3−-N were significantly higher in a fishery pond and nearby drinking wells than in other monitoring points. Annual exports of NO3−-N and NH4+-N were 4.06 × 104 and 8.14 × 103 kg yr−1, respectively and NO3−-N is the main form of N loss. The δ15N values ranged from 0‰ to 20‰ in surface water and groundwater, and the δ18O values ranged from 0‰ to 15‰ and 1‰–13‰, respectively. Dual stable isotope natural abundance distribution and water chemistry [NO3−]/[Cl−] molar ratio information suggested that manure and sewage and soil N were the main sources of NO3− in surface water and manure and sewage in groundwater in summer and winter. In spring, water occurred denitrification and ammonium fertilizer, manure and sewage were the main sources of NO3− in surface water and groundwater which sampling points were closer residential area and fish ponds than paddy field and local farmers used more Manure. Manure applications should be reasonable around drinking water wells to protect the drinking water quality.