The intensive use of antibiotics results in the continuous release of antibiotics into wastewater treatment systems, leading to the spread of antibiotic resistance. Nitrifying system is reported to be capable of degrading antibiotics, yet few studies have systematically investigated the inherent correlation among ammonium oxidation rate, antibiotic degradation and genetic expression of nitrifying bacteria along the process. This study selected a widely used sulfonamide antibiotic, sulfadiazine (SDZ), to investigate its biodegradation potential by an enriched nitrifying culture and the response of nitrifying bacteria against antibiotic exposure. Our results demonstrated that SDZ degradation was mainly contributed by cometabolism of ammonia-oxidizing bacteria (AOB), rather than biomass adsorption. The quantitative reverse transcription PCR (RT-qPCR) analysis revealed that the expression level of amoA gene was down-regulated due to the SDZ exposure. In addition, the degradation products of SDZ did not exhibit inhibitory effect on Escherichia coli K12, indicating the biotoxicity of SDZ could be mitigated after biodegradation. The findings offer insights regarding the biodegradation process of sulfonamide antibiotics via cometabolism by AOB.

Bisphenol S (BPS) has been widely used as a bisphenol alternative in recent few years. However, with mounting evidence suggesting that the presence of BPS in the environment also poses risks to ecosystems and human health, we decided to use the juvenile common carp (Cyprinus carpio) and its primary macrophages as in vivo and in vitro models to examine if BPS is a safe substitute of BPA. The present study evaluated the immune responses of chronic BPS exposure and their mechanisms of action associated with peroxisome proliferator-activated receptor (PPAR) signaling pathway. Potential oxidative stress and pro-inflammatory effects of BPS exposure were identified in fish liver after 60-day exposure, based on the increased reactive oxygen species (ROS) production, antioxidant capacity, NO production, lipid peroxidation, and induction of inflammatory cytokine expression, as well as acute phase protein levels of C-reactive protein, immunoglobulin M, lysozyme, and complement component 3. Moreover, pparγ, PPAR pathway-associated genes retinoid x receptor α (rxrα) and nuclear factor-κb (nfκb) presented a rough concentration-dependent alteration after BPS exposure. An acute BPS exposure to the isolated primary macrophages from juvenile common carp was performed to help elucidate gene expression patterns of pparγ, rxrα, and nfκb in a typical immune cell model, the results were consistent with what we found in vivo experiments for long-term BPS exposure. Furthermore, with coexposure to BPS and a PPARγ antagonist, the restriction of PPAR signaling pathway significantly inhibited the induction of ROS and the mRNA level of interleukin-1β, confirming the involvement of PPAR pathway in BPS-induced chronic inflammatory stress in liver.

Deposition of reactive nitrogen (N) is a major threat to terrestrial ecosystems associated with impacts on ecosystem properties and functions including carbon (C) and nutrient stocks, soil water quality and nutrient retention. In the oceanic-alpine Racomitrium heath habitat, N deposition is associated with moss mat degradation and a shift from bryophyte to graminoid dominance. To investigate the effects of moss mat decline on C and N stocks and fluxes, we collected Racomitrium heath vegetation/soil cores from sites along a gradient of N deposition in the UK. Cores were maintained under controlled conditions and exposed to scenarios of current (8–40 kg N ha⁻¹ y⁻¹), reduced (8 kg N ha⁻¹ y⁻¹) and elevated (50 kg N ha⁻¹ y⁻¹) N deposition. Cores from high N deposition sites had smaller aboveground C and N stocks and, under current conditions, leached large amounts of inorganic N and had low soil water pH compared with low N deposition sites. With reduced N deposition there was evidence for rapid recovery of soil water quality in terms of reduced N leaching and small increases in pH. Under high N deposition, cores from low N deposition sites retained much of the applied N while those with a history of high N deposition leached large amounts of inorganic N. Carbon fluxes in soil water and net CO₂ fluxes varied according to core source site but were not affected by the N deposition scenarios. We conclude that C and N stocks and cycling in Racomitrium heath are strongly affected by long-term exposure to N deposition but that soil water quality may improve rapidly, if N deposition rates are reduced. The legacy of N deposition impacts on moss mat cover and vegetation composition however, mean that the ecosystem remains sensitive to future pulses in N input.

At present, the study of microplastic sources is in a relatively preliminary stage due to the complexity of microplastic features in the environment. Based on a literature review, we developed a source-specific classification system for the quantitative analysis of microplastic sources. The classification system includes ten types of microplastics based on morphology and composition and can identify their main sources and the associated probabilities. To reflect the complexity of types and sources in the regional combination of microplastics, we first propose a microplastic diversity index (D1-D’(MP)). We use the South China Sea as an example to carry out quantitative source analysis and calculate the diversity index. Eight types of microplastics were found, mainly consisting of maritime coatings (type “Gran_coat”) (33.0%) and synthetic fibers (type “Fib_thin”) (29.6%). We also found that the diversity increased with offshore distance. In addition, we partitioned surface microplastics globally according to a two-dimensional microplastic abundance-diversity index. We believe that these indicators can effectively reflect pollution status and ultimately lead to different types of control measures. In the future, additional indicators for the characterization of microplastics must be included in the classification system to establish a one-to-one source analysis system for microplastic characteristics and source apportionment. In general, our study may provide new insights into the establishment of more accurate and quantitative source apportionment techniques and effective pollution control.

Muzzle emissions from firing an M4 carbine rifle in a semi-enclosed chamber were characterized for an array of compounds to provide quantitative data for future studies on potential inhalation exposure and rangeland contamination. Air emissions were characterized for particulate matter (PM) size distribution, composition, and morphology; carbon monoxide (CO); carbon dioxide (CO₂); energetics; metals; polycyclic aromatic hydrocarbons; and methane. Three types of ammunition were used: a “Legacy” (Vietnam-era) round, the common M855 round (no longer fielded), and its variant, an M855 round with added potassium (K)-based salts to reduce muzzle flash. Average CO concentrations up to 1500 ppm significantly exceeded CO₂ concentrations. Emitted particles were in the respirable size range with mass median diameters between 0.33 and 0.58 μm. PM emissions were highest from the M855 salt-added ammunition, likely due to incomplete secondary combustion in the muzzle blast caused by scavenging of combustion radicals by the K salt. Copper (Cu) had the highest emitted metal concentration for all three round formulations, likely originating from the Cu jacket on the bullet. Based on a mass balance analysis of each round's formulation, lead (Pb) was completely emitted for all three round types. This work demonstrated methods for characterizing emissions from gun firing which can distinguish between round-specific effects and can be used to initiate studies of inhalation risk and environmental deposition.

Hydrogen gas (H₂) has been shown as an important factor in plant tolerance to abiotic stresses, but the underlying mechanisms remain unclear. In the present study, the effects of H₂ and its interaction with nitric oxide (NO) on alleviating cadmium (Cd) stress in Brassica campestris seedlings were investigated. NO donor (SNP) or hydrogen-rich water (HRW) treatment showed a significant improvement in growth of Cd-stressed seedlings. Cd treatment upregulated both endogenous NO and H₂ (36% and 66%, respectively), and the increase of H₂ was prior to NO increase. When treated with NO scavenger (PTIO) or NO biosynthesis enzyme inhibitors (L-NAME and Gln), HRW-induced alleviation under Cd stress was prevented. Under Cd stress, HRW pretreatment significantly enhanced the NO accumulation, and together up-regulated the activity of NR (nitrate reductase) and expression of NR. HRW induced lower reactive oxygen species (ROS), higher AsA content, enhanced activity of POD (peroxidase) and SOD (superoxide dismutase) in seedling roots were inhibited by PTIO, L-NAME and Gln. Through proteomic analysis, the level of 29 proteins were changed in response to H₂ and NO-induced amelioration of Cd stress. Nearly half of them were involved in oxidation-reduction processes (about 20%) or antioxidant enzymes (approximately 20%). These results strongly indicate that in Cd-stressed seedlings, pretreatment with HRW induces the accumulation of H₂ (biosynthesized or permeated), which further stimulates the biosynthesis of NO through the NR pathway. Finally, H₂ and NO together enhance the antioxidant capabilities of seedlings in response to Cd toxicity.

Microalgae are commonly used in ecotoxicity testing due to their ease of culturing and rapid cell division rates. These tests generally utilise a single species of algae; however, microalgae occur in the environment as complex communities of multiple species. To date, routine multispecies toxicity tests using tropical microalgae have not been available. This study investigated four tropical freshwater microalgal species for use in a chronic multispecies toxicity test based on the population growth (cell division) rate: Pediastrum duplex, Monoraphidium arcuatum, Nannochloropsis-like sp. and Chlorella sp. 12. Flow cytometric analysis identified the different fluorescence and light scattering properties of each algal species and quantified each species within multispecies mixtures. Following optimisation of test media nutrients and pH, a toxicity testing protocol was developed with P. duplex, M. arcuatum and Nannochloropsis-like sp. There were no significant differences in growth rates of each alga when tested over 72 h as single species or in multispecies mixtures. Atrazine and imazapic, two herbicides with different modes of action, were used to assess the sensitivity of the multispecies toxicity test. Atrazine was toxic to all species with 72-h IC10 values of 7.2, 63 and 280 μg/L for P. duplex, M. arcuatum and Nannochloropsis-like sp. respectively, while imazapic was not toxic to any species at concentrations up to 1100 μg/L. The toxicity of atrazine and imazapic to each microalgal species in the multispecies toxicity test was the same as that determined from single-species toxicity tests indicating that the presence of these microalgae in a mixture did not affect the toxicity of these two herbicides. This study is the first to develop a multispecies tropical microalgal toxicity test for application in freshwaters. This time- and cost-effective tool can be utilised to generate data to assist environmental decision making and to undertake risk assessments of contaminants in tropical freshwater environments.

Stressors associated with climate change and contaminants, resulting from the activities of humans, are affecting organisms and ecosystems globally. Previous studies suggest that the unique characteristics of polar biota, such as slower metabolisms and growth, and the generally stable conditions in their natural environment, cause higher susceptibility to contamination and climate change than those in temperate and tropical areas. We investigated the effects of increased temperature and decreased salinity on copper toxicity in four subantarctic marine invertebrates using realistic projected conditions under a future climatic change scenario for this region. We hypothesised that these relatively subtle shifts in environmental stressors would impact the sensitivity of cold-adapted species to copper. The four test species were: a copepod Harpacticus sp.; isopod Limnoria stephenseni; flatworm Obrimoposthia ohlini; and bivalve Gaimardia trapesina. These species occupy a range of ecological niches, spanning intertidal and subtidal nearshore zones. We predicted that species would differ in their tolerance to stressors, depending on where they occurred within this ecological gradient. Organisms were exposed to the multiple stressors in a factorial design in laboratory based toxicity tests. Sensitivity estimates for copper (LC50) were calculated using a novel statistical approach which directly assessed the impacts of the multiple stressors. In three of the four species tested, sensitivity to copper was amplified by small increases in temperature (2-4 °C). The effects of salinity were more variable but a decrease of as little as 2 ppt caused a significant effect in one species. This study provides some of the first evidence that high latitude species may be at increased risk from contaminants under projected future climate conditions. This interaction, between contaminants and the abiotic environment, highlights a potential pathway to biodiversity loss under a changing climate.

High removal efficiency and excellent recyclability are the fundamental qualities that an outstanding adsorbent used for organic dye removal should possess. In this study, two recyclable gels (sodium alginate/Ca/fiber: SCFA hydrogels; cellulose nanofiber/chitosan: CNFCS aerogels) were successfully fabricated using the facile method. Additionally, the as-prepared adsorbents were investigated using a series of characterizations. The adsorption behavior and anti-interference performance of the synthesized gels were compared by choosing methylene blue (MB) as the model pollutant. The kinetic behavior of the gels towards MB was consistent with the pseudo first-order model, and the SCFA hydrogels reached adsorption equilibrium faster than the CNFCS aerogels. The maximum adsorption capacity of MB on the SCFA hydrogels and CNFCS aerogels was 1335.0 and 164.5 mg g⁻¹ (pH = 7.0, dosage: 0.5 g/L; initial concentration from 15 to 180 mg L⁻¹), respectively. More specifically, we found that the co-existing anions had different effects on MB adsorption over the gels used for MB removal. Furthermore, for the SCFA hydrogels, co-existing natural organic matter (NOM) at low concentrations enhanced MB adsorption, and then stabilized as the concentration of NOM increased. However, this increasing trend was not observed for MB adsorption on CNFCS aerogels; these gels exhibited a slight decrease at first, and then showed no change. Nevertheless, both the gels exhibited superior regeneration and recycling abilities.

Nitrogen (N) deposition has rapidly increased and is influencing forest ecosystem processes and functions on a global scale. Understanding process-specific N transformations, i.e., gross N transformations, in forest soils in response to N deposition is of great significance to gain mechanistic insights on the linkages between global N deposition and N availability or loss in forest soils. In this paper, we review factors controlling N mineralization, nitrification and N immobilization, particularly in relation to N deposition, discuss the limitations of net N transformation studies, and synthesize the literature on the effect of N deposition on gross N transformations in forest ecosystems. We found that more than 97% of published papers evaluating the effect of N deposition (including N addition experiments that simulate N deposition) on soil N cycle determined net rates of mineralization and nitrification, showing that N deposition significantly increased those rates by 24.9 and 153.9%, respectively. However, studies on net N transformation do not provide a mechanistic understanding of the effect of N deposition on N cycling. To date, a small number of studies (<20 published papers) have directly quantified the effect of N deposition on gross N transformation rates, limiting our understanding of the response of soil N cycling to N deposition. The responses to N deposition of specific N transformation processes such as autotrophic nitrification, heterotrophic nitrification, dissimilatory nitrate reduction to ammonium, N mineralization, and N immobilization are poorly studied. Future research needs to use more holistic approaches to study the impact of N deposition on gross N transformation rates, N loss and retention, and their microbial-driven mechanisms to provide a better understanding of the processes involved in N transformations, and to understand the differential responses between forest and other ecosystems.