Lake eutrophication remains a serious environmental problem of global significance, and phosphorus (P) plays a key role in lake eutrophication. Internal P loading, as a result of P release from sediments, is gathering more and more recognition as an important source governing the P availability in these ecosystems. Anoxic condition can promote the release of P associated with Fe oxides, which has already been a consensus. However, it is still unknown whether the anoxic conditions induced by eutrophication act to intensify or weaken the regeneration of organic P (Pₒᵣg) in sediments. We selected the Hongfeng Reservoir, a typical sub-deep lake, to study the regeneration behaviours of C and P in the sediments buried before and after eutrophication. The results showed that Pₒᵣg did not significantly increase with the rapid increase in organic C (Cₒᵣg) since eutrophication occurred. Furthermore, the organic C/P ratio was much higher in sediments buried after eutrophication than in those buried before, which indicated that Pₒᵣg regeneration had been significantly enhanced since eutrophication occurred. Based on C/P ratios, our estimation suggested that the Pₒᵣg regeneration and P release from sediment to water approximately enhanced 45.2% ± 8.7% and 34.5% ± 9.8%, respectively. Elevated primary productivity (algae) and the corresponding hypoxic/anoxic condition, both caused by eutrophication, promoted P biogeochemical cycle in the sub-deep reservoir. This study further verifies the significant contribution of regenerated Pₒᵣg to the internal P load, and highlights the importance of controlling P release from sediments in order to restore clear water ecosystems in sub-deep lakes or reservoirs.

In the current investigation, we presented the success of the modified hydrothermal method for synthesizing the iron-oxide nanoparticles (Fe₂O₃-NPs) efficiently. These NPs were further characterized by using different techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM) micrographs, energy-dispersive X-ray spectroscopy (EDAX)/Mapping pattern, Raman Spectroscopy Pattern, ultra violet (UV) and Photoluminescence (PL). All these analyses revealed highly pure nature of Fe₂O₃-NPs with no internal defects, and suggested its application for plant growth improvement. Therefore, we further investigated the separate as well as combined effects of the Fe₂O₃-NPs and citric acid (CA) in the alleviation of arsenic (As) toxicity in the soybean (Glycine max L.), by evaluating the different plant growth and metabolic attributes. Results of our study revealed that As-induced growth inhibition, reduction of photosynthesis, water use efficiency (WUE), and reactive oxygen species (ROS) accumulation whereas application of the Fe₂O₃-NPs and CA significantly reversed all these adverse effects in soybean plants. Moreover, the As-stress induced malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) production were partially reversed by the Fe₂O₃-NPs and CA in the As-stressed plants by 16% and 10% (MDA) and 29% and 12% (H₂O₂). This might have resulted due to the Fe₂O₃-NPs and CA induced activities of the antioxidant defense in plants. Overall, the Fe₂O₃-NPs and CA supplementation separately and in combination positively regulated the As tolerance in soybean; however, the effect of the combined application on the As tolerance was more profound relative to the individual application. These results suggested the synergetic effect of the Fe₂O₃-NPs and CA on the As-tolerance in soybean. However, in-depth mechanism underlying the defense crosstalk between the Fe₂O₃-NPs and CA needs to be further explored.

While evidence indicates that groundwater is a potential source for greenhouse gas (GHG) emissions, information for such emissions in groundwater used for irrigation is lacking. Based on 23 wells in the mid-western Guanzhong Basin of China, we investigated the dissolved CO₂, N₂O, and CH₄ distributions in groundwater, their relationships with water indicators, and emission fluxes during flood irrigation. We found zero methane, but CO₂ and N₂O were 30 and 25 times, respectively, supersaturated compared to atmospheric concentrations. Dissolved N₂O in groundwater was positively correlated with NO₃⁻-N (P = 0.009), while CO₂ depended mainly on low pH and high dissolved inorganic carbon. The CO₂ and N₂O emission fluxes detected in wellheads, especially in shallow wells, implied potential emissions. Flood irrigation experiments showed that 24.55% of dissolved CO₂ and 36.81% of dissolved N₂O in groundwater was degassed immediately (within 12 min of irrigation) to the atmosphere. Our study demonstrates that direct GHG emissions from groundwater used for agricultural irrigation in the Guanzhong Basin are potentially equivalent to about 2–4% of the GHG emissions from 3 years of fertilizer use on these farmlands, so further research should focus on optimizing irrigation strategies to mitigate GHG emissions.

As tracers, rare earth elements (REEs) can reflect the influence of human activities on the environmental changes in aquatic systems. To reveal the geochemical behavior of REEs in a water–sediment system influenced by human activities, the contents of REEs in the surface water and sediment in the Chaohu Lake Basin were measured by inductively coupled plasma mass spectrometry (ICP–MS). The results show that the ΣREE contents in the surface water are 0.10–0.850 μg L⁻¹, the ΣREE contents in the sediments are 71.14–210.01 μg g⁻¹, and the average contents are 0.24 μg L⁻¹ and 126.72 μg g⁻¹, respectively. Almost all water and sediment samples have obvious light REE (LREE) enrichment, which is the result of the input of LREE-rich substances released by natural processes and human activities (industrial and agricultural production). Under the alkaline water quality conditions of Chaohu Lake, REEs (especially LREEs) are easily removed from water by adsorption/coprecipitation reactions with suspended colloidal particles, which leads to the enrichment of LREEs in sediments. The Ce anomaly of the water–sediment system is related to the oxidation environment, while the Eu anomaly is related to the plagioclase crystallization. Significant Gd anomalies was observed in the downstream of rivers flowing through urban areas, which was related to the anthropogenic Gd wastewater discharged by hospitals. The ∑REE–δEu and provenance index (PI) discrimination results are consistent, indicating that the sediments in Chaohu Lake mainly come from rivers flowing through the southwest farmland. Furthermore, the spatial distribution of REEs shows that these tributaries are significantly affected by agricultural activities. The distribution and accumulation of REEs in Chaohu Lake are the result of the interaction of natural and human processes. The results can provide a scientific reference for the distribution and environmental behavior of REEs in aquatic environments disturbed by human beings.

Microplastics (MPs), plastic particles <5 mm in diameter, have become an emerging ubiquitous concern for the environment. Rivers are the primary pathways that transport MPs from the land to the ocean; however, standardized methodologies for in-situ sampling in freshwater environments remain undefined. Notably, uncertainties in MP sampling methods lead to errors in estimating MP discharge through rivers. In the present study, the inter-sample variance of plankton net-obtained MP concentrations for two urban rivers in Japan was investigated. Numerical concentrations, expressed in particles·m⁻³, revealed that variance s2 was proportional to the mean m of replicated estimates of numerical concentrations. A derived statistical model suggested that river MPs disperse according to purely random processes; that is, Poisson point processes. Accordingly, a method was established to project the “precision,” the ratio of the standard error to m, of numerical concentrations based on the number of net sampling repetitions. It was found that the mean of two replicates maintained sufficient precision of <30% for conditions with high concentrations of ≥3 particles·m⁻³. Projected precisions under different levels of MP concentrations are also presented to help design future field campaigns.

Currently, urbanization is associated with an increase in air pollutants that contribute to invasive pathogen infections by altering the host's innate immunity and antimicrobial resistance capability. Streptococcus pyogenes, also known as Group A Streptococcus (GAS), is a gram-positive opportunistic pathogen that causes a wide range of diseases, especially in children and immunosuppressed individuals. Diesel exhaust particle (DEP), a significant constituent of particulate matter (PM), are considered a prominent risk factor for respiratory illness and circulatory diseases worldwide. Several clinical and epidemiological studies have identified a close association between PM and the prevalence of viral and bacterial infections. This study investigated the role of DEP exposure in increasing pulmonary and blood bacterial counts and mortality during GAS M1 strain infection in mice. Thus, we characterized the upregulation of reactive oxygen species production and disruption of tight junctions in the A549 lung epithelial cell line due to DEP exposure, leading to the upregulation of GAS adhesion and invasion. Furthermore, DEP exposure altered the leukocyte components of infiltrated cells in bronchoalveolar lavage fluid, as determined by Diff-Quik staining. The results highlighted the DEP-related macrophage dysfunction, neutrophil impairment, and imbalance in pro-inflammatory cytokine production via the toll-like receptor 4/mitogen-activated protein kinase signaling axis. Notably, the tolerance of the GAS biofilms toward potent antibiotics and bacterial resistance against environmental stresses was also significantly enhanced by DEP. This study aimed to provide a better understanding of the physiological and molecular interactions between exposure to invasive air pollutants and susceptibility to invasive GAS infections.

The contamination of toxic heavy metals (i.e., Cd, Cr, Pb, and Ni) and metalloid (i.e., As) (TMMs) is considered as a major cause of increasing incidences of human and livestock cancers, gastrointestinal disorders and neurological problems. The levels of these TMMS in soil, irrigation water, and plants like Salanum lycopersicum (tomato), Spinacia oleracea (Spinach), and Triticum aestivum (Wheat) samples were detected which were collected from various localities across 100 km around the city of Lucknow, India. This study reported that the concentration of TMMs was within the range of maximum allowable concentration (MAC) (FAO/WHO, 2011) in most of the agricultural soil, whereas, it was higher in irrigation water. The TMMs levels in the edible parts of vegetables and cereal were in the range 1.91–53.94 μg/g, 5.06–40.49 μg/g, 4.08-2312-29 μg/g, 0.43–51.48 μg/g, and 0.01–1.65 μg/g, respectively which was significantly higher than the MAC. The BAF of Cd and Ni was very high in the edible parts of the vegetables and cereal samples indicating an entry of TMMs in food chain through the metal-contaminated irrigation water, even if TMMs are low in the field soil. The contamination coefficient (Cfi) and Ecological risk factors (Efi) of the TMMs were detected in the range of low risk in all agricultural soil. The Ecological risk index (ERI) of TMMs was at moderate risk, indicating a mild impact of the metal toxicity in the agro-ecosystems but the high risk on the consumers. The daily intake (DI) of TMMs through vegetables and cereal was below the maximum allowable daily intake (MTDI) but the carcinogenic risk factor (CRs) potential of Cr, Cd, Ni, and As was observed significantly higher for these vegetables and cereal, which indicated a complex scenario of a far-future carcinogenic health hazard on consumers in densely populated city of Lucknow, India and its surrounding regions.

Thermokarst lakes form as the results of ice-rich permafrost thawing and act as important water resources in cold regions. However, the distributions of antibiotic resistance genes (ARGs) in thermokarst lakes are far less studied. Using metagenomic sequencing approach, we provided the first study to document ARGs in thermokarst lakes of the Yellow River Source Area on the Qinghai-Tibet Plateau (QTP). The results revealed that both sediment and water of the thermokarst lakes harbor diverse ARGs. Multidrug resistance genes were the most diverse, while rifamycin resistance genes were the most abundant with rpoB2 and rpoB genes having the highest proportion. Sediment samples contained more ARGs than water samples, but their composition differed between the two types of samples. However, the composition variations of sediment and water ARGs were closely correlated. The Sorensen dissimilarities of ARGs were controlled by strong turnover processes in sediment samples, and by turnover and nestedness in water samples. High contributions of nestedness were found between sediment and water samples. Moreover, ARGs in water had more significant relationships with environmental variables than that in sediment. Given the role of thermokarst lakes as important water resources in permafrost landscape, as well as intensifying influences of climate change and anthropogenetic activities, thermokarst lakes could bring potential ARG risks, warranting further investigation and evaluation.

During hydraulic fracturing, wastewaters - termed flowback and produced water (FPW) - are created as a by-product during hydrocarbon extraction. Given the large volumes of FPW that a single well can produce, and the history of FPW release to surface water bodies, it is imperative to understand the hazards that hydraulic fracturing and FPW pose to aquatic biota. Using rainbow trout embryos as model organisms, we investigated impacts to cardio-respiratory system development and function following acute (48 h) and sub-chronic (28-day) FPW exposure by examining occurrences of developmental deformities, rates of embryonic respiration (MO₂), and changes in expression of critical cardiac-specific genes. FPW-exposed embryos had significantly increased rates of pericardial edema, yolk-sac edema, and tail/trunk curvatures at hatch. Furthermore, when exposed at three days post-fertilization (dpf), acute 5% FPW exposures significantly increased embryonic MO₂ through development until 15 dpf, where a switch to significantly reduced MO₂ rates was subsequently recorded. A similar trend was observed during sub-chronic 1% FPW exposures. Interestingly, at certain specific developmental timepoints, previous salinity exposure seemed to affect embryonic MO₂; a result not previously observed. Following acute FPW exposures, embryonic genes for cardiac development and function were significantly altered, although at termination of sub-chronic exposures, significant changes to these same genes were not found. Together, our evidence of induced developmental deformities, modified embryonic MO₂, and altered cardiac transcript expression suggest that cardio-respiratory tissues are toxicologically targeted following FPW exposure in developing rainbow trout. These results may be helpful to regulatory bodies when developing hazard identification and risk management protocols concerning hydraulic fracturing activities.

Little is known about the main sources of ambient particulate matter (PM) in the 22 Eastern Mediterranean Region (EMR) countries. We designed this study to systematically review all published and unpublished source apportionment (SA), identification and characterization studies as well as emission inventories in the EMR. Of 440 articles identified, 82 (11 emission inventory ones) met our inclusion criteria for final analyses. Of 22 EMR countries, Iran with 30 articles had the highest number of studies on source specific PM followed by Pakistan (n = 15 articles) and Saudi Arabia (n = 8 papers). By contrast, there were no studies in Afghanistan, Bahrain, Djibouti, Libya, Somalia, Sudan, Syria, Tunisia, United Arab Emirates and Yemen. Approximately 72% of studies (51) were published within a span of 2015–2021.48 studies identified the sources of PM₂.₅ and its constituents. Positive matrix factorization (PMF), principal component analysis (PCA) and chemical mass balance (CMB) were the most common approaches to identify the source contributions of ambient PM. Both secondary aerosols and dust, with 12–51% and 8–80% (33% and 30% for all EMR countries, on average) had the greatest contributions in ambient PM₂.₅. The remaining sources for ambient PM₂.₅, including mixed sources (traffic, industry and residential (TIR)), traffic, industries, biomass burning, and sea salt were in the range of approximately 4–69%, 4–49%, 1–53%, 7–25% and 3–29%, respectively. For PM₁₀, the most dominant source was dust with 7–95% (49% for all EMR countries, on average). The limited number of SA studies in the EMR countries (one study per approximately 9.6 million people) in comparison to Europe and North America (1 study per 4.3 and 2.1 million people respectively) can be augmented by future studies that will provide a better understanding of emission sources in the urban environment.