The benefits of the artificial fixation of reactive nitrogen (Nr, nitrogen [N] compounds other than dinitrogen), in the form of N fertilizers and materials are huge, while at the same time posing substantial threats to human and ecosystem health by the release of Nr to the environment. To achieve sustainable N use, Nr loss to the environment must be reduced. An N-budget approach at the national level would allow us to fully grasp the whole picture of Nr loss to the environment through the quantification of important N flows in the country. In this study, the N budgets in Japan were estimated from 2000 to 2015 using available statistics, datasets, and literature. The net N inflow to Japanese human sectors in 2010 was 6180 Gg N yr⁻¹ in total. With 420 Gg N yr⁻¹ accumulating in human settlements, 5760 Gg N yr⁻¹ was released from the human sector, of which 1960 Gg N yr⁻¹ was lost to the environment as Nr (64% to air and 36% to waters), and the remainder assumed as dinitrogen. Nr loss decreased in both atmospheric emissions and loss to terrestrial water over time. The distinct reduction in the atmospheric emissions of nitrogen oxides from transportation, at −4.3% yr⁻¹, was attributed to both emission controls and a decrease in energy consumption. Reductions in runoff and leaching from land as well as the discharge of treated water were found, at −1.0% yr⁻¹ for both. The aging of Japan's population coincided with the reductions in the per capita supply and consumption of food and energy. Future challenges for Japan lie in further reducing N waste and adapting its N flows in international trade to adopt more sustainable options considering the reduced demand due to the aging population.

Delivering quality-changed water often contributes to the biological instability of drinking water distribution systems (DWDS). However, the potential effects of quality-changed water on the biostability within DWDS are not well understood, especially after water switching to quality-improved water. The objective of this study was to investigate the effects of quality-improved water on DWDS, focusing on the stability of biofilm. The practical aged-pipe was assembled into pipe reactors to simulate the effect of switching to quality-improve water. The adenosine triphosphate (ATP) concentration of bulk water in the pipe reactors increased from ∼1.2 ng/L to almost above 5 ng/L when fed water switching to TP 2. Biomass quantified by measuring ATP concentration confirmed that the risk of biofilm release through aged cast-iron (CI) pipe surfaces after water source switching. The changes in water characteristics due to quality-improved water source could cause bacteria release in DWDS at the initial period (at the first 7 days). However, the DWDS can establish the new stable phase after 42 days. Over time, biomass in the bulk water of the distribution system decreased significantly (The ATP concentration in the bulk maintains around 3 ng/L) after 42 days, indicating the improvement of water quality. The biofilm was dominated by bacteria related to iron-cycling process, and at the genus level, Desulfovibrio had the highest relative abundance, however, it decreased significantly (from 48% to 9.3%) after water source switching. And there was a slightly increase in the fraction of iron-oxidizing bacteria (IOB) and siderophore-producing bacteria (SPB), but a relatively higher increase in nitrate-reducing bacteria (NRB), nitrobacteria (NOB), and iron-reducing bacteria (IRB) was observed. Taken together, these results and the corrosion morphology, indicate that pipe biofilm and corrosion were chemically and microbially stable after re-stability under water source switching. In addition, the bulk water environment showed a marked decrease in selected bacteria at genus level, including pathogenic species, indicating the improvement of quality in drinking water.

Honey bees Apis mellifera forage in a wide radius around their colony, bringing back contaminated food resources that can function as terrestrial bioindicators of environmental pesticide exposure. Evaluating pesticide exposure risk to pollinators is an ongoing problem. Here we apply five metrics for pesticide exposure risk (prevalence, diversity, concentration, significant pesticide prevalence, and hazard quotient (HQ)) to a nation-wide field study of honey bees, Apis mellifera in the United States. We examined samples from 1055 apiaries over seven years for 218 different pesticide residues and metabolites, determining that bees were exposed to 120 different pesticide products with a mean of 2.78 per sample. Pesticides in pollen were highly prevalent and variable across states. While pesticide diversity increased over time, most detections occurred at levels predicted to be of low risk to colonies. Varroacides contributed most to concentration, followed by fungicides, while insecticides contributed most to diversity above a toxicity threshold. High risk samples contained one of 12 different insecticides or varroacides. Exposures predicted to be low-risk were nevertheless associated with colony morbidity, and low-level fungicide exposures were tied to queen loss, Nosema infection, and brood diseases.

Sediment remediation in eutrophic aquatic ecosystems is imperative, but effective ecological measures are scarce. A pilot-scale trial investigated sediment remediation by the addition of Tubifex tubifex. The results showed that the addition of T. tubifex accelerated sediment organic matter (OM) and nitrogen (N) loss, with averages of 7.7% and 75.1% increased loss (IL) compared to treatments without T. tubifex in the 60-day experiment, respectively. The percentages of the increased in water to the IL in sediment were only 0.6%, 0.21%, 2.1% and 6.3% for NH₄⁺-N, NOₓ⁻-N, TN and COD, respectively, at the end of the experiment. The absolute abundances of the nitrifying genes AOA and AOB; the denitrifying genes napA, nirS, nirK, cnorB and nosZ; and the anaerobic ammonia oxidation gene anammox increased 2.3- to 11.0-fold with the addition of T. tubifex. Therefore, the addition of T. tubifex is an effective strategy for sediment remediation by accelerating OM and N loss in sediment without substantially increasing the water N concentration.

Nitrate (NO₃⁻) is one of the common inorganic nitrogen compound pollutants in natural ecosystems, which may have serious risks for aquatic organisms. However, its toxicological mechanism remains unclear. In the current study, juvenile turbot (Scophthalmus maximus) were exposed to different concentrations of NO₃⁻ (CK− 3.57 ± 0.16, LN − 60.80 ± 1.21, MN − 203.13 ± 10.97 and HN − 414.16 ± 15.22 mg/L NO₃–N) for 60 d. The blood biochemical assays results revealed that elevated NO₃⁻ exposure significantly increased the concentrations of plasma NO₃⁻, NO₂⁻, MetHb, K⁺, cortisol, glucose, triglyceride, lactate, while significantly decreased the concentrations of plasma Hb, Na⁺ and Cl⁻, which meant that NO₃⁻ caused hypoxic stress and further affected the osmoregulation and metabolism in fish. Besides, exposure to MN and HN induced a significant decrease in the level of antioxidants, including SOD (Point: 60th day, MN, HN v.s. CK: 258.36, 203.73 v.s. 326.95 U/mL), CAT (1.97, 1.17 v.s. 2.37 U/mL), GSH (25.38, 20.74 v.s. 37.00 μmol/L), and GPx (85.32, 71.46 v.s. 129.36 U/mL), and a significant increase of MDA (7.54, 9.73 v.s. 5.27 nmol/L), suggesting that NO₃⁻ exposure leading to a disruption of the redox status in fish. Also, further research revealed that NO₃⁻ exposure altered the mRNA levels of p53 (HN: up to 4.28 folds) and p53-regulated downstream genes such as Bcl-2 (inferior to 0.44 folds), caspase-3 (up to 2.90 folds) and caspase-7 (up to 3.49 folds), indicating that NO₃⁻ exposure induced abnormal apoptosis in the fish gills. Moreover, IBRv2 analysis showed that the toxicity of NO₃⁻ exposure to turbot was dose-dependent, and the toxicity peaked on the 15th day. In short, NO₃⁻ is an environmental toxicological factor that cannot be ignored, because its toxic effects are long-term and could cause irreversible damage to fish. These results would be beneficial to improve our understanding of the toxicity mechanism of NO₃⁻ to fish, which provides baseline evidence for the risk assessment of environmental NO₃⁻ in aquatic ecosystems.

Ciprofloxacin (CFX) and ofloxacin (OFX) are two of the most often used fluoroquinolone antibiotics, and their residues are found in large amounts in various aquatic settings. However, the toxicity tests of CFX using eukaryotic organisms such as Daphnia magna are inadequate, and the test result of OFX is currently unknown. Therefore, the chronic toxicity test for D. magna was performed during 42 days under exposure to CFX and OFX concentrations of 50, 500, and 5000 μg L⁻¹. All exposure conditions did not cause mortality for D. magna. CFX exposure at 500 μg L⁻¹ resulted in an earlier oogenesis date and increased brood size in the second birth. The Poisson-based generalized linear mixed-effects model revealed that the reduction of fertility was statistically significant for the CFX and OFX exposures at 5000 μg L⁻¹. On the other hand, the production of dead eggs as offspring degradation was also found significantly as maternal D. magna exposed to antibiotics at 5000 μg L⁻¹. In addition, following long-term exposure to antibiotics, maternal adaptation to antibiotics was established for offspring deterioration and fertility. However, the OFX exposure showed that the fertility-suppressed effects continued for a longer period than the CFX exposure. Although no rational explanation has yet been given for the more substantial effect of OFX on reducing fertility than CFX, molecular cell biology and symbiotic microbial flora derived from previous studies could explain our ecotoxicological results. This study is the first report for the OFX chronic toxicities on D. magna by comparing it to the toxicity of CFX. Our study contributes to guiding the future impact assessment of fluoroquinolone antibiotic pollution on ecosystems, including the need for new statistical methods in ecotoxicological studies.

Iron-bearing nanoparticles (IBNPs) were abundant in particulate matter (PM). Due to their high reactivity, IBNPs were considered hazardous to human health, however, their toxic mode-of-action(s) are highly unclear. Ferroptosis is a novel programmed cell death (PCD) that highly associated with intracellular iron. However, the pro-ferroptotic effect of IBNPs has not been characterized. To this end, we ought to investigate whether and how IBNPs (synthetic γ-Fe₂O₃ and Fe₃O₄ NPs were selected as the model compounds) are involved in ferroptosis. We found that human umbilical vein endothelial cells (HUVECs) phagocytized large qualities of γ-Fe₂O₃ and Fe₃O₄ NPs, resulting in increased intracellular iron level. We further observed the disrupted cystine/glutamate reverse transporter (System Xc⁻) and glutathione peroxidase 4 (GPX4) signaling in γ-Fe₂O₃ and Fe₃O₄ NPs-challenged HUVECs. γ-Fe₂O₃ and Fe₃O₄ NPs could also cause mitochondrial fusion and fission dysregulation, activate lipid peroxidation and iron metabolism-related genes in a P53-dependent manner. Together, the ferroptotic activity of IBNPs should be acknowledged for the risk assessment of PM associated health effects.

Degradation of freshwater ecosystems by uncontrolled human activities is a growing concern in the tropics. In this regard, we aimed at testing an integrative framework based on the IFEQ index to assess freshwater ecosystem health of river basins impacted by intense livestock and agricultural activities, using the Muchacho River Basin (MRB) as a case study. The IFEQ combine multiple lines of evidence such as riverine hydromorphological analysis (LOE 1), physicochemical characterization using ions and pesticides (LOE 2), aquatic macroinvertebrate monitoring (LOE 3), and phytotoxicological essays with L. sativa (LOE 4). Overall, results showed an important reduction in streamflow and an elevated increase in ion concentrations along the MRB caused by deforestation and erosion linked to agricultural and livestock activities. Impacts of the high ion concentrations were evidenced in macroinvertebrate communities as pollution-tolerant families, associated with high conductivity levels, represented 92 % of the total abundance. Pollution produced by organophosphate pesticides (OPPs) was critical in the whole MRB, showing levels that exceeded 270-fold maximum threshold for malathion and 30-fold for parathion, the latter banned in Ecuador. OPPs concentrations were related to low germination percentages of Lactuca sativa in sediment phytotoxicity tests. The IEFQ index ranged from 44.4 to 25.6, indicating that freshwater ecosystem conditions were “bad” at the headwaters of the MRB and “critical” along the lowest reaches. Our results show strong evidence that intense agricultural and livestock activities generated significant impacts on the aquatic ecosystem of the MRB. This integrative approach better explains the cumulative effects of human impacts, and should be replicated in other basins with similar conditions to help decision-makers and concerned inhabitants generate adequate policies and strategies to mitigate the degradation of freshwater ecosystems.

Severe haze episodes in cold season in Beijing have been mitigated greatly during the last decade. However, the changes in aerosol chemistry as responses to the large reductions in gaseous precursors during the two phases of clean air action, i.e., phase Ⅰ (2013–2017) and phase Ⅱ (2018–2020), are less understood. Here we characterized such changes in cold season (January–March) by using five-year real-time aerosol particle composition measurements. Our results showed consistently large reductions for all chemical species from 2013 to 2020 with the largest decreases being chloride (95%) and organics (74%) followed by sulfate (69%), while the decreases in nitrate were comparatively small (44%). However, the contributions of sulfate were fairly stable despite the increased nitrate contributions from 18% in 2013 to 30% in 2020. Organic aerosol (OA) composition also changed significantly since 2018 with large increases in the contributions of secondary OA and corresponding decreases in primary OA from fossil fuel combustion and cooking emissions. The changes in aerosol chemistry were closely related to the different reductions in gaseous precursors, e.g., SO₂ vs. NO₂, and the enhanced secondary processes, e.g., the increases in O₃, sulfur and nitrogen oxidation efficiency. Further, we found that the changes in aerosol chemistry in cold season during the phase Ⅱ of clean air action (2018–2020) started to slow down with relatively small changes in PM₂.₅ and secondary inorganic species. Our results point towards a future challenge in mitigating air pollution in cold season, and the need of more stringent and scientific strategies to control secondary aerosol pollution in an environment with enhanced oxidation capacity and high precursors.

To enable and/or facilitate analysis of microplastics from environmental samples, a purification process is required to reduce the organic matter content. The development of such process has as one main concern, besides achieving efficient organic matter reduction, the preservation of the microplastics. In this study, a three-step method for sewage sludge purification was proposed employing sodium dodecyl sulfate and hydrogen peroxide. The effects of the purification method on seven polymers (LLDPE, HDPE, PP, PS, PET, PA66 and SBR) were evaluated in terms of mass change, surface characteristics, mechanical properties, thermal properties and functional groups change. It was also assessed how the polymers were affected by the purification chemicals without the presence of sewage sludge. The purification process led to changes in all tested plastics, but in different intensities. LLDPE, HDPE, PP, PS and PET did not suffer considerable degradation. PET was more affected by hydrolysis than oxidation. On the other hand, the integrities of PA66 and SBR were noticeably affected. The effects of the purification process were considered to be due to the plasticizer behavior of water and oxidation on PA66 and loss of filler and oxidation on SBR. For both polymers there was a reduction on the tensile strength of around 50–60% after the purification, indicating they could be prone to fragmentate into smaller pieces along the process. After purification, PA66 also started to decompose at a temperature around 10 °C lower comparing to virgin samples. Except for SBR, the presence of sewage sludge and its oxidation was more harmful to the polymers than the purification chemicals without the presence of sewage sludge. This study serves as an evaluation of the effects of the purification process on the degradation of microplastics and a methodology for such assessment when designing a purification process.