Photodemethylation can be one of the primary processes for loss of neurotoxic methylmercury (MeHg) in freshwater lakes. Few studies have quantified seasonal variations in photodemethylation rate constants as a function of dissolved organic matter (DOM). We conducted 1-week irradiation experiments in two seasons to test for spatial and temporal differences in photodemethylation potential in temperate lake waters. Six study lakes in Kejimkujik National Park, Nova Scotia were sampled in summer and fall to include a range of naturally occurring DOM concentrations (4.4–13.4 and 3.9–16.4 mg C L⁻¹, respectively). A negative linear relationship (R² = 0.76, p = 0.01) was found between DOM concentration and photodemethylation rate constant across seasons, indicating that DOM is a strong predictor of MeHg photodemethylation independent of seasonal effects. The two highest carbon lakes (BDW and PEB) had significantly higher energy-normalized photodemethylation rate constants in summer compared to fall corresponding with lower DOM concentrations in summer relative to fall. Additionally, there were negative linear relationships between MeHg photodemethylation and DOM photomineralization (R²s = 0.58–0.72) and DOM photobleaching (R²s = 0.83–0.90). This key finding suggests that competition for photons within DOM structures may reduce the potential for MeHg photodemethylation in high carbon waters and that this relationship persists across seasons.

Based on ozone observation data from urban stations and the Dingling (DL) background station, we investigated the trend of ozone concentrations in Beijing during 2004–2015. For urban stations, both O3_1 h and O3_8 h increased stably with a clear and significant linear pattern and the increase rate was notably higher during the period of May to Sep. Meanwhile, the variation of O3_1 h and O3_8 h for the DL station did not demonstrate a regular pattern. During this period, the differences between the diurnal peak of ozone concentrations at the DL background station and urban stations decreased significantly due to the rapid urbanization of Beijing. Furthermore, we examined simultaneous variations of ozone and its precursors during 2015 Grand Military Parade and 2014 APEC meeting and evaluated the performances of different emission-reduction measures during the two specific events. For 2015 Grand Military Parade, emission-reduction measures were implemented 14 days in advance, which led to a notable decrease of ozone concentrations during the Parade period. For 2014 APEC meeting, emission-reduction measures were not implemented in advance, which led to incomplete VOCs reduction and high VOCs/NOx values, and thus a significant increase of ozone concentrations during the APEC period. The emission-reduction measures during APEC and PARADE periods both slowed down the accumulation and cut down the concentration peaks of ozone. We also analyzed simultaneous concentration variations of ozone and its precursors in long time-series. The results proved that compared with other precursors, NO2/NO was an effective indicator for ozone concentration in Beijing, especially in urban areas. The findings from this research provide useful reference for better monitoring and managing ozone concentrations in Beijing and other cities through properly designed and implemented emission-reduction measures.

Controlling blooms of toxigenic phytoplankton, including cyanobacteria, is a high priority for managers of aquatic systems that are used for drinking water, recreation, and aquaculture production. Although a variety of treatment approaches exist, hydrogen peroxide (H2O2) has the potential to be an effective and ecofriendly algaecide given that this compound may select against cyanobacteria while not producing harmful residues. To broadly evaluate the effectiveness of H2O2 on toxigenic phytoplankton, we tested multiple concentrations of H2O2 on (1) four cyanobacterial cultures, including filamentous Anabaena, Cylindrospermopsis, and Planktothrix, and unicellular Microcystis, in a 5-day laboratory experiment and (2) a dense cyanobacterial bloom in a 7-day field experiment conducted in a nutrient-rich aquaculture pond. In the laboratory experiment, half-maximal effective concentrations (EC50) were similar for Anabaena, Cylindrospermopsis, and Planktothrix (average EC50 = 0.41 mg L−1) but were ∼10x lower than observed for Microcystis (EC50 = 5.06 mg L−1). Results from a field experiment in an aquaculture pond showed that ≥1.3 and ≥ 6.7 mg L−1 of H2O2 effectively eliminated Planktothrix and Microcystis, respectively. Moreover, 6.7 mg L−1 of H2O2 reduced microcystin and enhanced phytoplankton diversity, while causing relatively small negative effects on zooplankton abundance. In contrast, 20 mg L−1 of H2O2 showed the greatest negative effect on zooplankton. Our results demonstrate that H2O2 can be an effective, rapid algaecide for controlling toxigenic cyanobacteria when properly dosed.

To better characterize the transport of neonicotinoid insecticides to the world's largest freshwater ecosystem, monthly samples (October 2015–September 2016) were collected from 10 major tributaries to the Great Lakes, USA. For the monthly tributary samples, neonicotinoids were detected in every month sampled and five of the six target neonicotinoids were detected. At least one neonicotinoid was detected in 74% of the monthly samples with up to three neonicotinoids detected in an individual sample (10% of all samples). The most frequently detected neonicotinoid was imidacloprid (53%), followed by clothianidin (44%), thiamethoxam (22%), acetamiprid (2%), and dinotefuran (1%). Thiacloprid was not detected in any samples. The maximum concentration for an individual neonicotinoid was 230 ng L⁻¹ and the maximum total neonicotinoids in an individual sample was 400 ng L⁻¹. The median detected individual neonicotinoid concentrations ranged from non-detect to 10 ng L⁻¹. The detections of clothianidin and thiamethoxam significantly increased as the percent of cultivated crops in the basins increased (ρ = 0.73, P = .01; ρ = 0.66, P = .04, respectively). In contrast, imidacloprid detections significantly increased as the percent of the urbanization in the basins increased (ρ = 0.66, P = .03). Neonicotinoid concentrations generally increased in spring through summer coinciding with the planting of neonicotinoid-treated seeds and broadcast applications of neonicotinoids. More spatially intensive samples were collected in an agriculturally dominated basin (8 sites along the Maumee River, Ohio) twice during the spring, 2016 planting season to provide further information on neonicotinoid inputs to the Great Lakes. Three neonicotinoids were ubiquitously detected (clothianidin, imidacloprid, thiamethoxam) in all water samples collected within this basin. Maximum individual neonicotinoid concentrations was 330 ng L⁻¹ and maximum total neonicotinoid concentration was 670 ng L⁻¹; median detected individual neonicotinoid concentrations were 7.0 to 39 ng L⁻¹.

Aquatic animals live in an acoustic world in which they often rely on sound detection and recognition for various aspects of life that may affect survival and reproduction. Human exploitation of marine resources leads to increasing amounts of anthropogenic sound underwater, which may affect marine life negatively. Marine mammals and fishes are known to use sounds and to be affected by anthropogenic noise, but relatively little is known about invertebrates such as decapod crustaceans. We conducted experimental trials in the natural conditions of a quiet cove. We attracted shore crabs (Carcinus maenas) and common shrimps (Crangon crangon) with an experimentally fixed food item and compared trials in which we started playback of a broadband artificial sound to trials without exposure. During trials with sound exposure, the cumulative count of crabs that aggregated at the food item was lower, while variation in cumulative shrimp count could be explained by a negative correlation with crabs. These results suggest that crabs may be negatively affected by artificially elevated noise levels, but that shrimps may indirectly benefit by competitive release. Eating activity for the animals present was not affected by the sound treatment in either species. Our results show that moderate changes in acoustic conditions due to human activities can affect foraging interactions at the base of the marine food chain.

Constructed wetlands (CWs) are a promising technology to treat pesticide contaminated water, but its implementation is impeded by lack of data to optimize designs and operating factors. Unsaturated and saturated CW designs were used to compare the removal of triazole pesticide, tebuconazole, in unplanted mesocosms and mesocosms planted with five different plant species: Typha latifolia, Phragmites australis, Iris pseudacorus, Juncus effusus and Berula erecta. Tebuconazole removal efficiencies were significantly higher in unsaturated CWs than saturated CWs, showing for the first time the potential of unsaturated CWs to treat tebuconazole contaminated water. An artificial neural network model was demonstrated to provide more accurate predictions of tebuconazole removal than the traditional linear regression model. Also, tebuconazole removal could be fitted an area-based first order kinetics model in both CW designs. The removal rate constants were consistently higher in unsaturated CWs (range of 2.6–10.9 cm d⁻¹) than in saturated CWs (range of 1.7–7.9 cm d⁻¹) and higher in planted CWs (range of 3.1–10.9 cm d⁻¹) than in unplanted CWs (range of 1.7–2.6 cm d⁻¹) for both designs. The low levels of sorption of tebuconazole to the substrate (0.7–2.1%) and plant phytoaccumulation (2.5–12.1%) indicate that the major removal pathways were biodegradation and metabolization inside the plants after plant uptake. The main factors influencing tebuconazole removal in the studied systems were system design, hydraulic loading rate and plant presence. Moreover, tebuconazole removal was positively correlated to dissolved oxygen and all nutrients removal.

Pregnancy is a period when the mother and her offspring are susceptible to the toxic effects of metals. We investigated associations of intake of frequently consumed foods with urinary metals concentrations among pregnant women in the Pacific Northwest. We measured urinary cadmium (U-Cd), arsenic (U-As) and molybdenum (U-Mo) concentrations from spot urine samples in early pregnancy (15 weeks of gestation, on average) among 558 women from Seattle and Tacoma, Washington. We assessed periconceptional dietary intake using a semi-quantitative food frequency questionnaire (FFQ). We also determined early pregnancy zinc concentrations in serum. Statistical analyses involved multivariable linear regression models, adjusted for smoking status, age, race/ethnicity, multivitamin and supplement use, education, estimated total energy intake, and gravidity. The geometric mean and range in μg/g creatinine for U-Cd, U-As and U-Mo were 0.29 (0.1–8.2), 18.95 (3–550), and 72.1 (15–467), respectively. U-Cd was positively associated with dietary zinc intake (P-value = 0.004) and serum zinc (P-value<0.001) while it was negatively associated with coffee intake (P-value = 0.03). U-As was positively associated with dietary fish [(Lean fish, fatty fish, shellfish and non-fried fish) (P-values<0.01)], selenium (P-value = 0.004), zinc (P-value = 0.017), vegetables (P-value = 0.004), and low-fat yogurt (P-value = 0.03). Women who reported higher intake of dietary magnesium (Mg)(P-value = 0.04), insoluble fiber (P-value = 0.03), and low-fat yogurt (P-value = 0.04) had higher U-Mo concentrations. Our study suggests that vegetables, fish, fiber and yogurt might be significant dietary sources of metals. Future studies aimed at investigating the risk of exposure to metals from other various food sources among reproductive-age and pregnant women are needed.

To improve the accuracy and temporal-spatial resolution for a vehicle emission inventory in a medium-sized city with a strip road network, this study was conducted based on detailed hourly traffic-flow data for each day of 2014, and covered all road types and regions in the city of Foshan. Detailed hourly emission characteristics and sources in five regions were analysed. The results showed that the total vehicle emissions of CO, NOX, VOCs, and PM2.5 were 13.10 × 104, 0.23 × 104, 4.46 × 104, and 0.18 × 104 tons, respectively. Motorcycles (MCs) and light passenger cars (LPCs) were the dominant contributors of CO emissions, while buses and heavy passenger cars (HPCs) were the dominant contributors for NOX. As a whole, the daytime contributions to total emissions were close to 80%, and emissions during the peak periods accounted for almost 40%. Specifically, the hourly emissions of each pollutant on workdays were higher than on non-workdays (maximum up to 64.2%), and for some roads the early peak periods changed significantly from workdays to non-workdays. At expressways, artery roads, and local roads, the daily emission intensities of CO, NOx, and PM2.5 in Foshan were close to or even higher than that of Beijing. On a regional scale, the temporal variation of vehicle emissions on workdays at artery roads of different regions were similar. In addition, the higher emission intensities of CO and VOCs were identified in DaLiang-RongGui (DLRG) and that of NOX and PM2.5 were in Central Region (CR). These results are meaningful for decision-makers to help provide more detailed vehicle pollution control measures in Foshan with a strip road network and only one ring road.

Air pollution, being especially severe in the fast-growing developing world, continues to post a threat to public health. Yet, few studies are capable of quantifying well how different groups of people in different places experience different levels of air pollution at the global scale. In this paper, we use worldwide Chinese as a lens to quantify the spatiotemporal variations and geographic differences in PM2.5 exposures using unprecedented mobile phone big data and air pollution records. The results show that Chinese in South and East Asia suffer relatively serious PM2.5 exposures, where the Chinese in China have the highest PM2.5 exposures (52.8 μg/m3/year), which is fourfold higher than the exposures in the United States (10.7 μg/m3/year). Overall, the Chinese in Asian cities (35.5 μg/m3/year) experienced the most serious PM2.5 exposures when compared with the Chinese in the cities of other continents. These results, partly presented as a spatiotemporally explicit map of PM2.5 exposures for worldwide Chinese, help researchers and governments to consider how to address the effects of air pollution on public health with respect to different population groups and geographic locations.

Cyclophosphamide (CP) and Ifosfamide (IF) are two nitrogen mustard drugs widely prescribed in cancer therapy. They are continuously released via excreta into hospital and urban wastewaters reaching wastewater treatment plants. Although CP and IF, their metabolites and transformation products (TPs) residues have been found in the aquatic environment from few ng L⁻¹ to tens of μg L⁻¹, their environmental toxic effects are still not well known. The present study aimed to investigate the acute and chronic ecotoxicity of CP and IF and their commercially available human metabolites/TPs, i.e. carboxy-CP, Keto-CP and N-dechloroethyl-CP on different organisms of the aquatic trophic chain. The experiments were performed using the green alga Pseudokirchneriella subcapitata, the rotifer Brachionus calyciflorus and the crustaceans Thamnocephalus platyurus and Ceriodaphnia dubia. Moreover, to assess the treatment conditions in regards to parent compound removal and formation of new TPs, CP and IF were UV- irradiated for 6 h, 12 h, 24 h, 36 h and 48 h, followed by toxicity evaluation of treated samples by algae, rotifers and crustaceans. Between the parent compounds, IF resulted as more toxic drug under tested conditions, exerting both acute and chronic effects especially on C. dubia (LC50:196.4 mg L⁻¹, EC50:15.84 mg L⁻¹). Among the tested metabolites/TPs, only carboxy-CP inhibited the reproduction in the rotifer. However, LOEC and NOEC values were calculated for CP and IF for all organisms. In addition, despite a low degradation of CP (28%) and IF (36%) after 48 h UV-irradiation, statistically significant effect differences (p < 0.05) from not-irradiated and irradiated samples were observed in both acute and chronic assays, starting from 6 h UV-irradiation. Our results suggest that the toxic effects found in the aquatic organisms may be attributable to interactions between the parent compounds and their metabolites/TPs.