Ammonia (NH₃) volatilized from soils plays an important role in N cycle and air pollution, thus it is important to trace the emission source and predict source contributions to development strategies mitigating the environmental harmful of soil NH₃ volatilization. The measurements of ¹⁵N natural abundance (δ¹⁵N) could be used as a complementary tool for apportioning emissions sources to resolve the contribution of multiple NH₃ emission sources to air NH₃ pollution. However, information of the changes of δ¹⁵N–NH₃ values during the whole volatilization process under different N application rates are currently lacking. Hence, to fill this gap, we conducted a 15-day incubation experiment included different urea-N application rates to determine δ¹⁵N values of NH₃ during volatilization process. Results showed that volatilization process depleted ¹⁵N in NH₃. The average δ¹⁵N value of NH₃ volatilized from the 0, 20, 180, and 360 kg N ha⁻¹ treatment was −16.2 ± 7.3‰, −26.0 ± 5.4‰, −34.8 ± 4.8‰, and −40.6 ± 5.7‰. Overall, δ¹⁵N–NH₃ values ranged from −46.0‰ to −4.7‰ during the whole volatilization process, with lower in higher urea-N application treatments than those in control. δ¹⁵N–NH₃ values during the NH₃ volatilization process were much lower than those of the primary sources, soil (−3.4 ± 0.1‰) and urea (−3.6 ± 0.1‰). Therefore, large isotopic fractionation may occur during soil volatilization process. Moreover, negative relationships between soil NH₄⁺-N and NH₃ volatilization rate and δ¹⁵N–NH₃ values were observed in this study. Our results could be used as evidences of NH₃ source apportionments and N cycle.

Honey bees (Apis mellifera) and other pollinator populations are declining worldwide, and the reasons remain controversial. Based on laboratory testing, fungicides have traditionally been considered bee-safe. However, there have been no experimental tests of the effects of fungicides on colony health under field conditions, and limited correlational data suggests there may be negative impacts on bees at levels experienced in the field. We tested the effects of one of the most commonly used fungicides on colony health by feeding honey bee colonies pollen containing Pristine® (active ingredients: 25.2% boscalid, 12.8% pyraclostrobin) at four levels that bracketed concentrations we measured for pollen collected by bees in almond orchards. We also developed a method for calculating per-bee and per-larva dose. Pristine® consumption significantly and dose-dependently reduced worker lifespan and colony population size, with negative health effects observed even at the lowest doses. The lowest concentration we tested caused a 15% reduction in the worker population at an estimated dosage that was three orders of magnitude below the estimated LD₁₅ values for previous acute laboratory studies. The enhanced toxicity under field conditions is at least partially due to activation of colonial nutritional responses missed by lab tests. Pristine® causes colonies to respond to perceived protein malnutrition by increasing colony pollen collection. Additionally, Pristine induces much earlier transitioning to foraging in individual workers, which could be the cause of shortened lifespans. These findings demonstrate that Pristine® can negatively impact honey bee individual and colony health at concentrations relevant to what they experience from pollination behavior under current agricultural conditions.

Organomineral assemblages are building units of soil micro-aggregates and exert their essential roles in immobilizing toxic elements. Currently, our knowledge of the adsorption and partitioning behaviors of coexisting Cd–As onto organomineral composites is limited. Herein, we carefully studied Cd–As cosorption onto ferrihydrite organomineral composites made with either living or non-living organics, i.e., bacteria (Delftia sp.) or humic acid (HA), using batch adsorption and various spectroscopies. Batch results show that As(V) only enhances Cd(II) sorption on pure Fh at pH < 6 but cannot promote Cd(II) sorption to Fh–organo composites. However, Cd(II) noticeably promotes As(V) sorption at pH>~5–6. Synchrotron micro X-ray fluorescence indicates that Cd(II) adsorbs predominately to the bacterial fraction (Cd versus P, r = 0.924), whereas As(V) binds mainly to the Fh fraction (As versus Fe, r = 0.844) of the Fh–bacteria composite. On Fh–HA composite, however, Cd(II) and As(V) are both primarily sorbed by the Fh fraction (Cd/As versus P, r > 0.8), based on the scanning transmission electron microscopy-energy disperse spectroscopy analyses. Elemental distribution characterization also manifests the co-localization of Cd(II) and As(V) within the organomineral composite, particular in Fh–HA composite (Cd versus As, r = 0.8), which is further identified as the Fh–As–Cd ternary complex based on the observations (higher frequencies at ~753–761 cm⁻¹) of attenuated total reflection Fourier-transform infrared spectroscopy. Moreover, this ternary interaction is more pronounced in Fh–HA than in Fh–bacteria. In summary, our results suggest that Cd–As coadsorption behaviors on Fh–organo composites are different from those on pure minerals, and the presence of bacteria/HA can significantly affect metal (loid)s speciation, distribution, and ternary interaction. Therefore organomineral composites are a more suitable analog than pure mineral phases to predict the mobility and fate of Cd–As in natural environments.

Insecticide resistance is one of the major obstacles for controlling agricultural pests. There have been a lot of studies on insecticides stimulating the development of insect resistance. Herbicides account for the largest sector in the agrochemical market and are often co-applied with insecticides to control insect pests and weeds in the same cropland ecosystem. However, whether and how herbicides exposure will affect insecticide resistance in insect pests is largely unexplored. Here we reported that after exposure to herbicide butachlor, the lepidopteran Spodoptera litura larvae reduced susceptibility to the insecticide chlorpyrifos. Docking simulation studies suggested that general odorant-binding protein 2 (GOBP2) could bind to butachlor with high binding affinity, and silencing SlGOBP2 by RNA interference (RNAi) decreased larval tolerance to chlorpyrifos. Butachlor exposure induced ecdysone biosynthesis, whose function on increasing chlorpyrifos tolerance was supported in synergism experiments and confirmed by silencing the key gene (SlCYP307A1) for ecdysone synthesis. Butachlor exposure also activated the expression of detoxification enzyme genes. Silencing the genes with the highest herbicide-induced expression among the three detoxification enzyme genes led to increased larval susceptibility to chlorpyrifos. Collectively, we proposed a new mechanism that olfactory recognition of herbicides by GOBP2 triggers insect hormone biosynthesis and leads to high metabolic tolerance against insecticides. These findings provide valuable information for the dissection of mechanisms of herbicide-induced resistance to insecticides and also supplements the development of reduced-risk strategies for pest control.

The residual layer (RL) stores a large amount of pollutants, but its effect on near-surface pollution is unknown. In this study, a two-year continuous observation was performed in Beijing using a ceilometer. The generalized boundary layer includes the mixing layer and RL. The results showed that there is no significant seasonal difference in the generalized boundary layer height (GBLH). The average GBLHs in spring, summer, autumn and winter are 1155, 1139, 1036 and 1195 m, respectively. The diurnal variation characteristics of spring, summer and autumn are similar, and the RL disappears when the mixing layer height reaches its peak in the afternoon. In winter, the development of the mixing layer is weak, and there is a 33.8% chance that the RL cannot be breached, thus making the mixing layer height at noon much lower than the GBLH. The concentrations of PM₂.₅ in the mixing layer and RL are 89 and 52 μg m⁻³, respectively, and the probability that the PM₂.₅ concentration in the RL was higher than that near the ground was 38.9%. RL transport represents an important beginning of the pollution event during the winter mornings and afternoons in Beijing. This study is helpful to better understand the structure of the RL and its influence on air pollution.

Limited data were on the acute respiratory responses in the elderly in response to personal exposure of particulate matter (PM). In order to evaluate the changes of airway inflammation and pulmonary functions in the elderly in response to individual exposure of particles (PM₁.₀, PM₂.₅ and PM₁₀), we analyzed 43 elderly subjects with either asthma, chronic obstructive pulmonary disease (COPD) or Asthma COPD Overlap (ACO) and 40 age-matched subjects without asthma nor COPD in an urban community in Shanghai, China. Data were collected at the baseline and in 6 follow-ups from August 2016 to December 2018, once every 3 months except for the last twice with a 6-month interval. In each follow-up, pulmonary functions, fractional exhaled nitric oxide (FeNO), 7-day continuous personal exposure to airborne particles were measured. Multivariate linear mixed effect regression models were applied to investigate the quantitative changes of pulmonary functions and FeNO in two respective groups. The results showed that on average 4.7 follow-up visits were completed in each participant. In subjects with CRDs, an inter-quartile range (IQR) increase of personal exposure to PM₁.₀, PM₂.₅ and PM₁₀ was significantly associated with an average increase of FeNO(Lag1) of 6.7 ppb (95%CI 1.2, 9.9 ppb), 6.2 ppb (95%CI 1.5, 12.0 ppb) and 5.6 ppb (95%CI 1.5, 11.0 ppb), respectively, and an average decrease of FEV1(Lag2) of −3.6 L (95%CI -6.0, −1.1 L), −3.6 L (95%CI -6.4, −0.8 L) and −3.2 L (95%CI -5.8, −0.6 L), respectively, in the single-pollutant model. These associations remained consistent in the two-pollutant models adjusting for gaseous air pollutants. Stratified analysis showed that subjects with lower BMI, females and non-allergies were more sensitive to particle exposure. No robust significant effects were observed in the subjects without CRDs. Our study provided data on the susceptibility of the elderly with CRDs to particle exposure of PM₁.₀ and PM₂.₅, and the modification effects by BMI, gender and history of allergies.

This research explored the occurrence, epigenetic toxic profiling and main toxic pollutants of POPs in surface water of Dongjiang River, southern China. The concentrations of selected POPs including polycyclic aromatic hydrocarbons (PAHs), endocrine disrupting chemicals (EDCs), phthalate esters (PAEs) and polybrominated diphenyl ethers (PBDEs) of surface water from 18 sites were investigated. ∑₁₆PAHs and ∑₄EDCs were at a moderate level, while ∑₆PAEs and ∑₆PBDEs had low pollution levels. PAHs, EDCs and PAEs showed higher concentrations in dry season than those in wet season, and the loading of selected POPs in tributaries was higher than those in mainstream due to intensive manufactures and lower runoff volume. Moreover, activities of DNA methyltransferase (DNMT)1, histone deacetylase (HDAC2, HDAC8) were confirmed to be sensitive indicators for epigenetic toxicity. The DNMT1-mediated epigenetic equivalency toxicity of organic extracts in Dongjiang River were more serious than those of HDAC2 and HDAC8. Correlation analysis shown binding affinity between POPs and DNMT1, HDAC2 and HDAC8 could be regarded as toxic equivalency factors. Risk assessment suggested that 4-nonylphenol and bisphenol A were the largest contributors to epigenetic risk. This study is the first attempt to quantify epigenetic toxicity and epigenetic risk evaluation of river water.

Excessive Cd accumulation in cereals, especially in high-consumption staple crops, such as rice, is of major concern. Therefore, elucidation of cultivar-specific variation in rice grain Cd bioaccessibility and toxicity in humans would help the development of remedial strategies for Cd accumulation and toxicity. The present study combined an in vitro gastrointestinal digestion model with a human HL-7702 cell and assessed Cd bioaccessibility and toxicity to humans from the grains of 30 rice cultivars of different types harvested from Cd-contaminated paddy soil. The mean grain Cd content of cultivars within the type exceeded acceptable national standards. Cadmium bioaccessibility was high in all grains (9.08–23.6%) except the low accumulator (LA) rice cultivar (7.93%). The mean estimated daily intake of Cd via the cultivars (except LA) exceeded the FAO/WHO permissible limit based not only on the total grain Cd concentration but also on bioaccessible Cd concentration. A dose-proportional correlation between the in vitro bioaccessible and total grain Cd concentrations was observed, suggesting that Cd bioaccessibility accurately reflects the transfer of Cd from rice grain to humans. Toxicity assay results demonstrated that Cd from rice grains could commence oxidative stress and injury in HL-7702 cells, except the LA rice, which did not exhibit significant alteration in HL-7702 cells owing to its low Cd concentration. These results provide primary evidence to suggest that the cultivation of the LA rice cultivar is an effective agronomic approach to avert Cd entry into the food chain and alleviate Cd toxicity in humans.

Herein, the first evidence of the ability of melatonin (MLT) to counteract cadmium (Cd) toxic effects on the rat ovary is reported. Cd treatment, enhancing oxidative stress, provoked clear morphological, histological and biomolecular alterations, i.e. in the estrous cycle duration, in the ovarian and serum E₂ concentration other than in the steroidogenic and folliculogenic genes expression. Results demonstrated that the use of MLT, in combination with Cd, avoided the changes, strongly suggesting that it is an efficient antioxidant for preventing oxidative stress in the rat ovary. Moreover, to explore the underlying mechanism involved, at molecular level, in the effects of Cd-MLT interaction, the study focused on the mTOR and ERK1/2 pathways. Interestingly, data showed that Cd influenced the phosphorylation status of mTOR, of its downstream effectors and of ERK1/2, inducing autophagy and apoptosis, while cotreatment with MLT nullified these changes. This work highlights the beneficial role exerted by MLT in preventing Cd-induced toxicity in the rat ovary, encouraging further studies to confirm its action on human ovarian health with the aim to use this indolamine to ameliorate oocyte quality in women with fertility disorders.