To characterize the emissions of polycyclic aromatic hydrocarbons (PAHs) from residential biomass burning and coal combustion in field environments, smoke samples were collected from the combustion of six types of biomass in heated kangs and four types of coal in traditional stoves and semi-gasifier stoves. The emission factors (EFs) of the total PAH were in the range of 84.5–344 mg/kg for biomass burning, with lower EFs for biomass with higher densities, and in the range of 38.0–206 mg/kg for coal combustion, with lower EFs for coals with higher maturity. Moreover, EFs were lower from high-density biomass fuels (wood trunk, 84.5 ± 11.3 mg/kg) than low-maturity coals (bituminous coal, 206 ± 16.5 mg/kg). Parent, oxygenated, alkylated, and nitrated PAHs accounted for 81.1%, 12.6%, 6.2%, and 0.1%, respectively, of the total-PAH EFs from biomass burning, and 84.7%, 13.8%, 1.4%, and 0.1%, respectively, of the total-PAH EFs from coal combustion. PAH source profiles differed negligibly between biomass fuels but differed significantly between bituminous coal and anthracite coal fuels. The characteristic species of sources were phenanthrene, 9-fluorenone, and 2-nitrobiphenyl for biomass burning, and were phenanthrene, benzo[ghi]perylene, 1,4-naphthoquinone, and 2-nitrobiphenyl for coal combustion. The ratios of benzo[b]fluoranthene/(benzo[b]fluoranthene + benzo[k]fluoranthene) were 0.40–0.45 for biomass burning and 0.89–0.91 for coal combustion, and these significantly different values constitute unique markers for distinguishing these fuels in source apportionment. Benzo[a]pyrene-equivalent factor emissions were 2.79–11.3 mg/kg for biomass and 7.49–41.9 mg/kg for coal, where parent PAHs contributed 92.0%–95.1% from biomass burning and 98.6%–98.8% from coal combustion. Total-PAH emissions from residential heating were 1552 t across Shaanxi province, to which wheat straw (445 t) in biomass burning and bituminous coal (438 t) in coal combustion were the highest contributors. Results from this study provide crucial knowledge for the source identification of PAHs as well as for the design of abatement strategies against pollutant emissions.

Populations of plants and animals, including humans, living in close proximity to abandoned uranium mine sites are vulnerable to uranium exposure through drainage into nearby waterways, soil accumulation, and blowing dust from surface soils. Little is known about how the environmental impact of uranium exposure alters the health of human populations in proximity to mine sites, so we used developmental zebrafish (Danio rerio) to investigate uranium toxicity. Fish are a sensitive target for modeling uranium toxicity, and previous studies report altered reproductive capacity, enhanced DNA damage, and gene expression changes in fish exposed to uranium. In our study, dechorionated zebrafish embryos were exposed to a concentration range of uranyl acetate (UA) from 0 to 3000 μg/L for body burden measurements and developmental toxicity assessments. Uranium was taken up in a concentration-dependent manner by 48 and 120 h post fertilization (hpf)-zebrafish without evidence of bioaccumulation. Exposure to UA was not associated with teratogenic outcomes or 24 hpf behavioral effects, but larvae at 120 hpf exhibited a significant hypoactive photomotor response associated with exposure to 3 μg/L UA which suggested potential neurotoxicity. To our knowledge, this is the first time that uranium has been associated with behavioral effects in an aquatic organism. These results were compared to potential metal co-contaminants using the same exposure paradigm. Similar to uranium exposure, lead, cadmium, and iron significantly altered neurobehavioral outcomes in 120-hpf zebrafish without inducing significant teratogenicity. Our study informs concerns about the potential impacts of developmental exposure to uranium on childhood neurobehavioral outcomes. This work also sets the stage for future, environmentally relevant metal mixture studies. Summary Uranium exposure to developing zebrafish causes hypoactive larval swimming behavior similar to the effect of other commonly occurring metals in uranium mine sites. This is the first time that uranium exposure has been associated with altered neurobehavioral effects in any aquatic organism.

Initial Cadmium (Cd) isotope fractionation studies in cereals ascribed the retention of Cd and its light isotopes to the binding of Cd to sulfur (S). To better understand the relation of Cd binding to S and Cd isotope fractionation in soils and plants, we combined isotope and XAS speciation analyses in soil-rice systems that were rich in Cd and S. The systems included distinct water management (flooded vs. non-flooded) and rice accessions with (excluder) and without (non-excluder) functional membrane transporter OsHMA3 that transports Cd into root vacuoles. Initially, 13% of Cd in the soil was bound to S. Through soil flooding, the proportion of Cd bound to S increased to 100%. Soil flooding enriched the rice plants towards heavy isotopes (δ¹¹⁴/¹¹⁰Cd = −0.37 to −0.39%) compared to the plants that grew on non-flooded soils (δ¹¹⁴/¹¹⁰Cd = −0.45 to −0.56%) suggesting that preferentially light Cd isotopes precipitated into Cd sulfides. Isotope compositions in CaCl₂ root extracts indicated that the root surface contributed to the isotope shift between soil and plant during soil flooding. In rice roots, Cd was fully bound to S in all treatments. The roots in the excluder rice strongly retained Cd and its lights isotopes while heavy isotopes were transported to the shoots (Δ¹¹⁴/¹¹⁰Cdₛₕₒₒₜ₋ᵣₒₒₜ 0.16–0.19‰). The non-excluder rice accumulated Cd in shoots and the apparent difference in isotope composition between roots and shoots was smaller than that of the excluder rice (Δ¹¹⁴/¹¹⁰Cdₛₕₒₒₜ₋ᵣₒₒₜ −0.02 to 0.08‰). We ascribe the retention of light Cd isotopes in the roots of the excluder rice to the membrane transport of Cd by OsHMA3 and/or chelating Cd–S complexes in the vacuole. Cd–S was the major binding form in flooded soils and rice roots and partly contributed to the immobilization of Cd and its light isotopes in soil-rice systems.

The Pearl River Estuary (PRE), the largest estuary in Southern China, historically has suffered from metal contamination as a result of inputs from different riverine discharges. Determining the sources of metals accumulation in local aquatic flora and fauna remains a great challenge for this estuarine system with complex water circulation. In this study, Zn isotope ratios were measured in local oysters (Crassostrea hongkongensis) collected at 8 locations in the estuary on four occasions from 2014 to 2018, to better understand and assess the contamination sources. The results showed no significant differences (p < 0.05) in δ⁶⁶Zn values in oysters among the four sampling dates within individual sites. However, approximately a 0.67‰ (range from -0.66‰ to 0.01‰) difference in average δ⁶⁶Zn values was consistently found in oysters collected from the east side of the estuary compared to the west side, despite their comparable Zn concentrations. A mixing model was subsequently used to estimate the relative contributions from various sources to the δ⁶⁶Zn values in these oysters. The mixing model predicts that zinc derived from the dissolved fraction (approximately 80 %) was the dominant uptake pathway for oysters collected at the east shore whereas approximately 50 % of the Zn in oysters collected at the west shore was derived from the particulate fraction. The mixing model also was used to estimate the relative impacts of fresh versus saline water on the measured δ⁶⁶Zn values. Contributions from these two sources also varied between the east and west shores. This study presents the first data for Zn isotope ratios in oysters from the PRE, providing new insight for using Zn isotope ratios in oysters as a powerful tracer of sources in a complex estuarine system.

Coastal wetland soils serve as a great C sink or source, which highly depends on soil carbon flux affected by complex hydrology in relation to salinity. We conducted a field experiment to investigate soil respiration of three coastal wetlands with different land covers (BL: bare land; SS: Suaeda salsa; PL: Phragmites australis) from May to October in 2012 and 2013 under three groundwater tables (deeper, medium, and shallower water tables) in the Yellow River Delta of China, and to characterize the spatial and temporal changes and the primary environmental drivers of soil respiration in coastal wetlands. Our results showed that the elevated groundwater table decreased soil CO₂ emissions, and the soil respiration rates at each groundwater table exhibited seasonal and diurnal dynamics, where significant differences were observed among coastal wetlands with different groundwater tables (p < 0.05), with the average CO₂ emission of 146.52 ± 13.66 μmol m⁻²s⁻¹ for deeper water table wetlands, 105.09 ± 13.48 μmol m⁻²s⁻¹ for medium water table wetlands and 54.32 ± 10.02 μmol m⁻²s⁻¹ for shallower water table wetlands. Compared with bare land and Suaeda salsa wetlands, higher soil respiration was observed in Phragmites australis wetlands. Generally, soil respiration was greatly affected by salinity and soil water content. There were significant correlations between groundwater tables, electrical conductivity and soil respiration (p < 0.05), indicating that soil respiration in coastal wetlands was limited by electrical conductivity and groundwater tables and soil C sink might be improved by regulating water and salt conditions. We have also observed that soil respiration and temperature showed an exponential relationship on a seasonal scale. Taking into consideration the changes in groundwater tables and salinity that might be caused by sea level rise in the context of global warming, we emphasize the importance of groundwater level and salinity in the carbon cycle process of estuarine wetlands in the future.

The fate of many chemicals in the environment, particularly contaminants of emerging concern (CEC), have been characterised to a limited extent with a major focus on occurrence in water. This study presents the characterisation, distribution and fate of multiple chemicals including pharmaceuticals, recreational drugs and pesticides in surface water, sediment and fauna representing different food web endpoints in a typical UK estuary (River Colne, Essex, UK). A comparison of contaminant occurrence across different benthic macroinvertebrates was made at three sites and included two amphipods (Gammarus pulex &Crangon crangon), a polychaete worm (Hediste diversicolor) and a gastropod (Peringia ulvae). Overall, multiple contaminants were determined in all compartments and ranged from; <LOQ – 386 ng L⁻¹ in surface water (n = 59 compounds), <LOQ – 146 ng g⁻¹ in sediment (n = 39 compounds) and <LOQ – 91 ng g⁻¹ biota (n = 33 compounds). H. diversicolor and P. ulvae (sediment dwellers) showed greater chemical body burden compared with the two swimming amphipod species sampled (up to 2.5 - 4-fold). The most frequently determined compounds in biota (100%, n = 36 samples) included; cocaine, benzyoylecgonine, carbamazepine, sertraline and diuron. Whilst some of the highest concentrations found were in species H. diverscolor and P. ulvae for psychoactive pharmaceuticals including citalopram (91 ng g⁻¹), sertraline (69 ng g⁻¹), haloperidol (66 ng g⁻¹) and the neonicotinoid, imidacloprid (33 ng g⁻¹) Sediment was noted as an important exposure route for these benthic dwelling organisms and will be critical to monitor in future studies. Overall, the analysis of multiple species and compartments demonstrates the importance of including a range of exposure pathways in order to appropriately assess chemical fates and associated risks in the aquatic environment.

Selenium (Se) is both an essential micronutrient and a contaminant of concern that is of particular interest in mining-influenced waterbodies in Canada. The objective of this research was to characterize the trophic dynamics of selenium along a gradient of exposure concentrations in a Canadian boreal lake ecosystem. From June 20 to August 22, 2018, six limnocorrals (littoral, ∼3000 L enclosures) were spiked with mean measured concentrations of 0.4, 0.8, 1.6, 3.4, 5.6 and 7.9 μg Se/L as selenite, and three limnocorrals served as untreated controls (background aqueous Se = 0.08–0.09 μg/L). Total Se (TSe) concentrations in water, periphyton, phytoplankton, sediment, benthic macroinvertebrates, zooplankton and female finescale dace (Phoxinus neogaeus; added on day 21 of the experiment) were measured throughout and at the end of the experiment. Total Se bioaccumulation by organisms was generally non-linear. Greater uptake by phytoplankton than periphyton was observed. Taxonomic differences in accumulation of TSe by invertebrates (Heptageniidae = Chironomidae > zooplankton) were observed as well. Fish muscle and ovary tissue TSe bioaccumulation was more variable than that at lower trophic levels and uptake patterns indicated that fish did not reach steady state concentrations. This research provides field-derived models for the uptake of Se by algae and invertebrates, and contributes to a better understanding of the dynamics of TSe bioaccumulation over a gradient of exposure concentrations in cold-water lentic systems.

Forchlorfenuron (CPPU) has been used worldwide, to boost size and improve quality of various agricultural products. CPPU and its metabolites are persistent and have been detected frequently in fruits, water, sediments, and organisms in aquatic systems. Although the public became aware of CPPU through the exploding watermelon scandal of 2011 in Zhenjiang, China, little was known of its potential effects on the environment and wildlife. In this study, adverse effects of CPPU on developmental angiogenesis and vasculature, which is vulnerable to insults of persistent toxicants, were studied in vivo in zebrafish embryos (Danio rerio). Exposure to 10 mg CPPU/L impaired survival and hatching, while development was hindered by exposure to 2.5 mg CPPU/L. Developing vascular structure, including common cardinal veins (CCVs), intersegmental vessels (ISVs) and sub-intestinal vessels (SIVs), were significantly restrained by exposure to CPPU, in a dose-dependent manner. Also, CPPU caused disorganization of the cytoskeleton. In human umbilical vein endothelial cells (HUVECs), CPPU inhibited proliferation, migration and formation of tubular-like structures in vitro. Results of Western blot analyses revealed that exposure to CPPU increased phosphorylation of FLT-1, but inhibited phosphorylation of FAK and its downstream MAPK pathway in HUVECs. In summary, CPPU elicited developmental toxicity to the developing endothelial system of zebrafish and HUVECs. This was do, at least in part due to inhibition of the FAK/MAPK signaling pathway rather than direct interaction with the VEGF receptor (VEGFR).

The widespread decline in oceanic dissolved oxygen (DO), known as deoxygenation, is a threat to many marine ecosystems, and fish are considered one of the more vulnerable marine organisms. While food intake and growth rates in some fish can be reduced under hypoxic conditions (DO ~ 60 μmol kg⁻¹), the dietary transfer of essential metals remains unclear. In this context, we investigated the influence of DO on the dietary acquisition of two essential metals (Zn and Mn) in the commercially important gilthead seabream (Sparus aurata) using radiotracer techniques. Fish were exposed to variable DO conditions (normoxia 100% DO, mild-hypoxia 60% DO, and hypoxia 30% DO), and fed a single radiolabeled food ration containing known activities of ⁵⁴Mn and ⁶⁵Zn. Depuration and assimilation mechanisms under these conditions were followed for 19 d. Based on whole body activity after the radio-feeding, food consumption tended to decrease with decreasing oxygen, which likely caused the significantly reduced growth (- 25%) observed at 30% DO after 19 d. While there was an apparent reduction in food consumption with decreasing DO, there was also significantly higher essential metal assimilation with hypoxic conditions. The proportion of ⁶⁵Zn remaining was significantly higher (~60%) at both low DO levels after 24 h and 19 d while ⁵⁴Mn was only significantly higher (27%) at the lowest DO after 19 d, revealing element specific effects. These results suggest that under hypoxic conditions, stressed teleost fish may allocate energy away from growth and towards other strategic processes that involve assimilation of essential metals.

Ground level ozone exerts a strong impact on crop yields, yet how to properly quantify ozone induced yield losses in China remains challenging. To this end, we employed a series of O₃-crop models to estimate ozone induced yield losses in China from 2014 to 2018. The outputs from all models suggested that the total Relative Yield Losses (RYL) of wheat in China from 2014 to 2018 was 18.4%–49.3% and the total RYL of rice was 6.2%–52.9%. Consequently, the total Crop Production Losses (CPL) of wheat and rice could reach 63.9–130.4 and 28.3–35.4 million tons, and the corresponding Total Economic Losses (TEL) could reach 20.5–44.7 and 11.0–15.3 billion dollars, stressing the great importance and urgency of national ozone management. Meanwhile, the estimation outputs highlighted the large variations between different regional O₃-crop models when applying to large scales.Instead of applying one unified O₃-crop models to all regions across China, we also explored the strategy of employing specific O₃-crop models in corresponding (and neighboring) regions to estimate ozone induced yield loss in China. The comparison of two strategies suggested that the mean value from multiple models may still present an inconsistent over/underestimation trend for different crops. Therefore, it is a preferable strategy to employ corresponding O₃-crop models in different regions for estimating the national crop losses caused by ozone pollution. However, the severe lack of regional O₃-crop models in most regions across China makes a robust estimation of national yield losses highly challenging. Given the large variations between O₃-crop interactions across regions, a systematic framework with massive regional O₃-crop models should be properly designed and implemented.