Abstract  The present work is the ensuing part of the study on spatial and temporal variations in chemical characteristics of PM10 (particulate matter with aerodynamic diameter ≤ 10 μm) over Indo Gangetic Plain (IGP) of India. It focuses on the apportionment of PM10 sources with the application of different receptor models, i.e., principal component analysis with absolute principal component scores (PCA-APCS), UNMIX, and positive matrix factorization (PMF) on the same chemical species of PM10. The main objective of this study is to perform the comparative analysis of the models, obtained mutually validated outputs and more robust results. The average PM10 concentration during January 2011 to December 2011 at Delhi, Varanasi, and Kolkata were 202.3 ± 74.3, 206.2 ± 77.4, and 171.5 ± 38.5 μg m-3, respectively. The results provided by the three models revealed quite similar source profile for all the sampling regions, with some disaccords in number of sources as well as their percent contributions. The PMF analysis resolved seven individual sources in Delhi [soil dust (SD), vehicular emissions (VE), secondary aerosols (SA), biomass burning (BB), sodium and magnesium salt (SMS), fossil fuel combustion, and industrial emissions (IE)], Varanasi [SD, VE, SA, BB, SMS, coal combustion, and IE], and Kolkata [secondary sulfate (Ssulf), secondary nitrate, SD, VE, BB, SMS, IE]. However, PCA-APCS and UNMIX models identified less number of sources (besides mixed type sources) than PMF for all the sampling sites. All models identified that VE, SA, BB, and SD were the dominant contributors of PM10 mass concentration over the IGP region of India.

Abstract  This study explored the physiological responses of the coral Pocillopora damicornis to high nitrate concentrations and thermal stresses. The expression of heat shock proteins Hsp60 and Hsp32, Symbiodiniaceae density, Chl a concentration, Fv/Fm, H2O2 scavenging, and caspase 3 activity varied during 60 h incubations at 28 °C or 32 °C, ambient or high nitrate (~10 μM) concentrations, and their combinations. In combined stresses, corals showed a rapid and high oxidation level negatively affecting the Symbiodiniaceae density and Chl a concentration at 12 h, followed by caspase 3 and Hsps upregulations that induced apoptosis, bleaching and tissue detachment. Corals under thermal stress showed the highest oxidation and upregulation of Hsps and caspase 3 resulting in coral discoloration. High nitrate treatment alone did not seriously affect the coral function. Results showed that combined stress treatment severely affected coral physiology and, judging from the condition of detached tissues, these corals might have lower chances to recover.

Abstract  Tropical scleractinian corals support a diverse assemblage of microbial symbionts. This 'microbiome' possesses the requisite functional diversity to conduct a range of nitrogen (N) transformations including denitrification, nitrification, nitrogen fixation and dissimilatory nitrate reduction to ammonium (DNRA). Very little direct evidence has been presented to date verifying that these processes are active within tropical corals. Here we use a combination of stable isotope techniques, nutrient uptake calculations and captured metagenomics to quantify rates of nitrogen cycling processes in a selection of tropical scleractinian corals. Denitrification activity was detected in all species, albeit with very low rates, signifying limited importance in holobiont N removal. Relatively greater nitrogen fixation activity confirms that corals are net N importers to reef systems. Low net nitrification activity suggests limited N regeneration capacity; however substantial gross nitrification activity may be concealed through nitrate consumption. Based on nrfA gene abundance and measured inorganic N fluxes, we calculated significant DNRA activity in the studied corals, which has important implications for coral reef N cycling and warrants more targeted investigation. Through the quantification and characterisation of all relevant N-cycling processes, this study provides clarity on the subject of tropical coral-associated biogeochemical N-cycling.

Abstract  The spatial distributions of elemental and molecular species are vital pieces of information for a broad number of applications such as material development and bio/environmental analysis. There is currently no single analytical method that can simultaneously acquire elemental, molecular, and spatial information from a single sample. This paper presents the coupling of an NWR213 laser ablation (LA) system to the liquid sampling-atmospheric pressure glow discharge (LS-APGD) microplasma for combined atomic and molecular (CAM) analysis. The work demonstrates a fundamental balance that must be considered between the extent of fragmentation of molecules and ionization of atoms for CAM analysis. Detailed studies showed that the interelectrode gap to be a critical parameter for controlling the ionization efficiency of atomic and molecular species. Utilizing Design-of-Experiment (DoE) procedures, the discharge current was also found to be a significant parameter to control. Elemental lead, caffeine, and simultaneous lead and caffeine analysis via LA-LS-APGD-MS was made possible through improved understanding of the influence of plasma parameters on the product mass spectra of laser-ablated particles. Finally, a chemical map of elemental lead and molecular caffeine, from lead nitrate and caffeine residues, was generated, demonstrating the comprehensive mapping capabilities of LA-LS-APGD-MS. The practical relevance of the capabilities is demonstrated by mapping glutamic acid from a cryosectioned chicken breast with a thallium spike deposited within the tissue. It is believed that the LA-LS-APGD-MS could be a valuable methodology for the simultaneous mapping of elemental and molecular species from a variety of samples.

Abstract  A facile and straightforward approach has been implemented for the synthesis of nanostructured Y2O3 particles via sol-gel method from yttrium nitrate solution. The individual effects of calcination temperature, precipitation-chelating agent and precursor concentration on microstructural parameters, crystal defects and morphology of Y2O3 were investigated in detail. The morphology of synthesized nanostructured Y2O3 particles was revealed by scanning electron microscopy (SEM). X-ray diffraction (XRD) and Williamson Hall analysis were used to find out how Y2O3 crystallite size, lattice strain-stress, dislocation density and morphology affect the sol-gel process parameters. Comparative studies for determining crystallite size of particles were carried out by Modified Debye-Scherer and Williamson Hall analysis. A more detailed microstructural analysis and investigation of crystallographic imperfections were conducted by Williamson- Hall (W-H) method. W-H analysis was carried out on Y2O3 particles with spherical shape and sponge morphology for the first time. Results reveal that as calcination temperature is increased from 700 degrees C to 900 degrees C, the crystallite size increases from 37.15 nm to 49.49 nm while lattice strain increases from 8.154 x 10(-4) to 8.696 x 10(-4). It is also found that, an increment in solution concentration from 0.1 mol/L to 0.2 mol/L results in crystallite size decrement from 47.27 nm to 44.37 nm. A further increment from 0.2 mol to 0.4 mol/L leads to crystallize size increase from 44.37 nm to 49.67 nm.

Abstract  CruCA4 is a secreted isoform of the α-carbonic anhydrase (CA, EC 4.2.1.1) family, which has been identified in the octocoral Corallium rubrum. This enzyme is involved in the calcification process leading to the formation of the coral calcium carbonate skeleton. We report here experiments performed on the recombinant CruCA4 with the technique of protonography that can be used to detect in a simple way the enzyme activity. We have also investigated the inhibition profile of CruCA4 with one major class of CA inhibitors, the inorganic anions. A range of weak and moderate inhibitors have been identified having KI in the range of 1-100 mM, among which the halides, pseudohalides, bicarbonate, sulfate, nitrate, nitrite, and many complex inorganic anions. Stronger inhibitors were sulfamide, sulfamate, phenylboronic acid, phenylarsonic acid, and diethylditiocarbamate, which showed a better affinity for this enzyme, with KI in the range of 75 μM-0.60 mM. All these anions/small molecules probably coordinate to the Zn(II) ion within the CA active site as enzyme inhibition mechanism.

Abstract  Ocean acidification (OA) and nutrient enrichment threaten the persistence of near shore ecosystems, yet little is known about their combined effects on marine organisms. Here, we show that a threefold increase in nitrogen concentrations, simulating enrichment due to coastal eutrophication or consumer excretions, offset the direct negative effects of near-future OA on calcification and photophysiology of the reef-building crustose coralline alga, Porolithon onkodes Projected near-future pCO2 levels (approx. 850 µatm) decreased calcification by 30% relative to ambient conditions. Conversely, nitrogen enrichment (nitrate + nitrite and ammonium) increased calcification by 90-130% in ambient and high pCO2 treatments, respectively. pCO2 and nitrogen enrichment interactively affected instantaneous photophysiology, with highest relative electron transport rates under high pCO2 and high nitrogen. Nitrogen enrichment alone increased concentrations of the photosynthetic pigments chlorophyll a, phycocyanin and phycoerythrin by approximately 80-450%, regardless of pCO2 These results demonstrate that nutrient enrichment can mediate direct organismal responses to OA. In natural systems, however, such direct benefits may be counteracted by simultaneous increases in negative indirect effects, such as heightened competition. Experiments exploring the effects of multiple stressors are increasingly becoming important for improving our ability to understand the ramifications of local and global change stressors in near shore ecosystems.

Abstract  Purpose: Fumagillin has been previously used to treat corneal microsporidial keratitis and also identified as an angiogenesis inhibitor. This study aimed to evaluate efficacy of fumagillin bicyclohexylamine on the rat model of corneal neovascularization induced by silver nitrate cauterization. Methods: Twenty-four Albino Wistar rats (n = 24) were divided into three groups. Following silver nitrate-induced corneal injury, eyes in Group 1 received one drop of 5 mg/mL topical fumagillin bicyclohexylamine four times daily for 10 days. Group 2 received subconjunctival injection of 0.1 mL fumagillin bicyclohexylamine (2.5 mg/mL) on day 1 and day 5. Group 3 received artificial tears and lubricants four times daily for 10 days as control. On day 10, animals were sacrificed. Corneal specimens were obtained and prepared to assess vascular endothelial growth factor (VEGF-C) levels and corneal angiogenic microvessel density. Results: There was no significant difference in VEGF-C levels between the groups (P = 0.994). Assessment of angiogenic microvessel density for peripheral corneal zone also did not reveal significant difference between the groups (P = 0.113). However, mean vascular density in Group 1 and Group 2 was significantly higher for both midperipheral and central corneal zones in comparison with Group 3 (P = 0.003, P = 0.015). Conclusions: Previously proved to be effective for treatment of microsporidial keratitis in humans, topical and subconjunctival concentration or dosing of fumagillin bicyclohexylamine failed to reduce corneal neovascularization induced by silver nitrate in this study. Further studies comparing different concentrations and dosing may detect inhibitory effects of fumagillin on corneal neovascularization without inducing toxicity. 2018, Springer Nature B.V.

Abstract  Volatile phenolic derivatives are substantially emitted from biomass burning and produced from photochemistry of atmospheric aromatic volatile organic compounds (VOCs). Oxidation of phenolic VOCs at night by nitrate radicals (NO3.) may represent a significant source of secondary organic aerosols (SOA) and brown carbon (BrC) formation in the atmosphere. In this study, NO3. oxidation of five phenolic derivatives, including phenol, catechol, 3-methylcatechol, 4-methylcatechol and guaiacol are investigated in laboratory experiments. The SOA constituents from the NO3. oxidation were analyzed using electrospray ionization ion mobility spectrometry time-of-flight mass spectrometry, which allows for characterization and identification of isomers in the oxidation products. Through these analyses, several classes of nitro-containing products in addition to the well-known nitrophenol compounds were observed, including: (1) the nitrophenol type of products with additional hy-droxyl functional groups; (2) non-aromatic/ring-opening nitro-products with lower double bond equivalence; (3) phenol and catechol products from the C-7 phenolic VOCs with carbon-containing substitutions; and (4) nitrated diphenyl ether dimers. The present work indicates that new products from previously unrecognized pathways are formed during NO3. oxidation of phenolic VOCs and may contribute an important portion of the SOA. Some of these products were also observed in ambient aerosols during biomass burning. We suggest that the ubiquity of the nitrophenol type of products in the SOA derived from phenolic VOC + NO3. are responsible for the strong light absorption measured in this study. Therefore, elucidation of these pathways will be critical for understanding the nighttime oxidation and BrC formation mechanisms.

Abstract  Long-term phytoplankton community changes indicate the trophic status under nutrient regulation conditions in eutrophic lakes, although the modulatory role of climate change scenarios in their indicative function has been underestimated. Hence, we analyzed the relative contributions of nutrient and climate factors to interannual and seasonal variations in the phytoplankton biomass and composition from 1992 to 2017 in Meiliang Bay, Lake Taihu, China. Discrete phytoplankton communities from five periods were classified according to their interannual features. Variations in the phytoplankton community composition were observed during the five periods, and these variations included a shift from exclusive cyanobacterial dominance before 2008 to diatom-cyanobacterial codominance in 2008-2010 and from cyanobacterial dominance in 2011-2014 to cyanobacterial-diatom codominance in 2015-2017. The phytoplankton biomass pattern typically peaked in summer, although peaks also occurred in winter 2008-2010 and autumn 2011-2014. Additionally, the phytoplankton biomass increased by threefold from 2015 to 2017, which might have been related to rising air temperatures and greater light availability. The variance in the phytoplankton community was significantly explained by nutrient (ammonium, nitrate and phosphate) and climatic (air temperature and wind speed) factors. However, the explaining effect of the factors varied among the five periods: nutrients strongly impacted the community composition from 1992 to 2007, whereas climatic variables became more important modulators after 2007. These results reveal that climatic factors play importance roles in shaping the phytoplankton community and cyanobacterial blooms and suggest that differences in the roles between specific climatic conditions should be considered. Future declines in cyanobacterial blooms require further dual nitrogen and phosphorus reduction and longer recovery times under current climate change scenarios in this and possibly other shallow eutrophic lakes.

Abstract  Previous research suggests that fertilization of surface waters with chemically reduced nitrogen (N), including ammonium (NH4+), may either enhance or suppress phytoplankton growth. To identify the factors influencing the net effect of NH4+, we fertilized natural phytoplankton assemblages from two eutrophic hardwater lakes with growth-saturating concentrations of NH4Cl in 241 incubation experiments conducted biweekly May-August during 1996-2011. Phytoplankton biomass (as chlorophyll a) was significantly (p < 0.05) altered in fertilized trials relative to controls after 72 h in 44.8% of experiments, with a marked rise in both spring suppression and summer stimulation of assemblages over 16 yr, as revealed by generalized additive models (GAMs). Binomial GAMs were used to compare contemporaneous changes in physico-chemical (temperature, Secchi depth, pH, nutrients; 19.5% deviance explained) and biological parameters (phytoplankton community composition; 40.0% deviance explained) to results from fertilization experiments. Models revealed that that the likelihood of growth suppression by NH4+ increased with abundance of diatoms, cryptophytes, and unicellular cyanobacteria, particularly when water temperatures and soluble reactive phosphorus (SRP) concentrations were low. In contrast, phytoplankton was often stimulated by NH4+ when chlorophytes and non-N-2-fixing cyanobacteria were abundant, and temperatures and SRP concentrations were high. Progressive intensification of NH4+ effects over 16 yr reflects changes in both spring (cooler water, increased diatoms and cryptophytes) and summer lake conditions (more chlorophytes, earlier cyanobacteria blooms), suggesting that the seasonal effects of NH4+ will vary with future climate change and modes of N enrichment.

Abstract  Hazardous contaminants, such as nitrite and microcystin-leucine arginine (MC-LR), are released into water bodies during cyanobacterial blooms and may adversely influence the normal physiological function of hydrobiontes. The combined effects of nitrite and MC-LR on the antioxidant defense and innate immunity were evaluated through an orthogonal experimental design (nitrite: 0, 29, 290 μM; MC-LR: 0, 3, 30 nM). Remarkable increases in malondialdehyde (MDA) levels have suggested that nitrite and/or MC-LR exposures induce oxidative stress in fish spleen, which were indirectly confirmed by significant downregulations of total antioxidant capacity (T-AOC), glutathione (GSH) contents, as well as transcriptional levels of antioxidant enzyme genes cat1, sod1 and gpx1a. Simultaneously, nitrite and MC-LR significantly decreased serum complement C3 levels as well as the transcriptional levels of splenic c3b, lyz, il1β, ifnγ and tnfα, and indicated that they could jointly impact the innate immunity of fish. The severity and extent of splenic lesions were aggravated by increased concentration of nitrite or MC-LR and became more serious in combined groups. The damages of mitochondria and pseudopodia in splenic macrophages suggest that oxidative stress exerted by nitrite and MC-LR aimed at the membrane structure of immune cells and ultimately disrupted immune function. Our results clearly demonstrate that nitrite and MC-LR exert synergistic suppressive effects on fish innate immunity via interfering antioxidant responses, and their joint toxicity should not be underestimated in eutrophic lakes.

Abstract  Oyster reef restoration can significantly increase benthic denitrification rates. Methods applied to measure nutrient fluxes and denitrification from oyster reefs in previous studies include incubations of sediment cores collected adjacent to oyster clumps, benthic chambers filled with intact reef segments that have undergone in situ equilibration and ex situ incubation, and cores with single oysters. However, fluxes of nutrients vary by orders of magnitude among oyster reefs and methods. This study compares two methods of measuring nutrient and metabolic fluxes on restored oyster reefs: incubations including intact segments of oyster reef and incubations containing oyster clumps without underlying sediments. Fluxes of oxygen (O2), dissolved inorganic carbon (DIC), ammonium (NH4+), combined nitrate and nitrite (NO2/3-), di-nitrogen (N2), and soluble reactive phosphorus (SRP) were determined in June and August in Harris Creek, a tributary of the Chesapeake Bay, Maryland, USA. Regression of fluxes measured from clumps alone against those measured from intact reef segments showed significant positive relationships for O2, DIC, NH4+, and SRP (R2 = 0.920, 0.61, 0.26, and 0.52, respectively). Regression of clump fluxes against the oyster tissue biomass indicates significant positive relationships for O2 and NH4+, marginally significant and positive relationships for DIC and N2, and no significant relationship for NO2/3- or SRP. Although these results demonstrate that the incubation of oyster clumps without underlying sediments does not accurately represent biogeochemical fluxes measured from the whole oyster and sediment community, this work supports the need to understand the balance between the metabolism of oysters and local sediments to correctly estimate biogeochemical rates.

Abstract  A river water quality spatial profile has a diverse pattern of variation over different climatic regions. To comprehend this phenomenon, our study evaluated the spatial scale variation of the Water Quality Index (WQI). The study was carried out over four main climatic classes in Asia based on the Koppen-Geiger climate classification system: tropical, temperate, cold, and arid. The one-dimensional surface water quality model, QUAL2Kw was selected and compared for water quality simulations. Calibration and validation were separately performed for the model predictions over different climate classes. The accuracy of the water quality model was assessed using different statistical analyses. The spatial profile of WQI was calculated using model predictions based on dissolved oxygen (DO), biological oxygen demand (BOD), nitrate (NO3), and pH. The results showed that there is a smaller longitudinal variation of WQI in the cold climatic regions than other regions, which does not change the status of WQI. Streams from arid, temperate, and tropical climatic regions show a decreasing trend of DO with respect to the longitudinal profiles of main river flows. Since this study found that each climate zone has the different impact on DO dynamics such as reaeration rate, reoxygenation, and oxygen solubility. The outcomes obtained in this study are expected to provide the impetus for developing a strategy for the viable improvement of the water environment.

Abstract  The effects and interactive effects of different nitrogen (N) sources (ammonium, nitrate, and urea) and carbon dioxide (CO2) concentrations were investigated on Alexandrium tamarense, a harmful marine dinoflagellate, by measuring its growth (μ), extracellular carbonic anhydrase (CA), and its toxicity to zebrafish (Danio rerio) embryo. The μ and CA were influenced more strongly by CO2 concentrations rather than by N sources; significant effects of CO2 on μ and CA were observed under low CO2 concentration (LC) conditions compared to high CO2 concentration (HC) conditions. The ammonium and nitrate media under LC conditions had the maximum μ and CA, which was inhibited under HC conditions. The embryotoxic effects were influenced more strongly by the N sources than by CO2 concentrations, thus excluding the lower deformation in urea under HC conditions. Moreover, the antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione S-transferase (GST), and catalase (CAT) were detected in normal (untreated) zebrafish embryos, and among them, the level of SOD was the highest. In summary, this study provides a clear insight for understanding the effects and interactive effects of N sources and CO2 concentrations on the growth and toxicity of harmful dinoflagellates.

Abstract  Ammonium dinitramide (ADN) is a strong, environmentally friendly oxidizer used in composite solid rocket propellants. As there is no reliable colorimetric sensor for ADN assay applicable to in-field screening, we developed a sensitive and practical sensing method to determine it in the presence of other explosives and possible interferents, based on the detection of nitrite formed from ADN degradation under UV light in a slightly alkaline (i.e. of lower alkalinity than needed to hydrolyze nitramines) solution by a nanoparticle-based colorimetric sensor. The ADN-derived nitrite formed a colored product via a Griess reaction using gold nanoparticles modified with 4-aminothiophenol (4-ATP-AuNPs) along with a coupling reagent N-(1-naphthyl)ethylene diamine (NED) for forming an azo dye. The method used for ADN detection could also be applied to tetryl samples at a different wavelength. The limit of detection (LOD) was 0.012 mg L-1 for ADN and 0.615 mg L-1 for tetryl. Interference effects of energetic materials like trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and pentaerythritol tetranitrate (PETN) to ADN determination could be overcome. In addition, common soil ions did not adversely affect the nanosensor performance. The developed method was statistically validated against reference voltammetric, UV, and HPLC methods using t- and F- tests.

Abstract  The Arctic flora hosts a limited number of species due to its extreme environmental conditions which also yield novel and unique secondary metabolites from withstanding plants. Considering a lack of research on bioactivity potential of Arctic flora, Ranunculus hyperboreus, an Arctic plant, was studied for its anti-inflammatory potential as a part of ongoing research on discovering novel natural bioactive products. Solvent-based fractions (H2O, n-BuOH, 85% aq. MeOH, n-hexane) from R. hyperboreus extract were observed to decrease the elevated nitrate amount during the inflammatory response of lipopolysaccharide-induced mouse macrophage RAW264.7 cells. To some extent, treatment with fractions was able to regulate the expression and protein levels of inflammation-related enzymes, iNOS and COX-2, and pro-inflammatory cytokines, TNF-α, IL-1β, and IL-6. The most active fractions, H2O and 85% aq. MeOH, were suggested to exert their effect through suppressed activation of MAPK pathways, especially JNK. Based on the studies of same species, phenolic glycosides were suggested to be the main active ingredients. To our knowledge, this is the first report of any bioactivity of R. hyperboreus which could be a valuable source of natural bioactive agents against inflammation.