Abstract  Calcareous macroalgae are of particular ecological importance as primary producers, carbonate sediment builders, and habitat providers in coral reef ecosystems. Ocean warming is a major threat to calcareous algae, but it remains unclear exactly how these algae will respond to it. In this study, the potential physiological impacts of ocean warming on the calcareous alga Amphiroa fragilissima were evaluated in laboratory experiments. Increasing temperature from 26 to 28°C had positive effects on algal growth rate and chlorophyll a content, but these parameters decreased significantly at 32°C, which is 5°C above the annual mean temperature in the study region. Algal bleaching occurred at 34°C. There were no significant differences in CaCO3 content of thalli among different temperatures; however, calcification rate was inhibited significantly at 32 and 34°C. Transcriptome analyses using the Illumina RNA-seq platform showed that differentially expressed genes were annotated mainly in the categories of steroid biosynthesis, gap junction, ribosome, and mTOR signaling pathway. The expression levels of PsbA and PsbP were suppressed at 32°C, implying that inactivation of photosystem II could be a main reason for the decreased photosynthetic rate. Down-regulation of the genes encoding carbonic anhydrase and nitrate reductase was observed at 32°C, which could inhibit growth rate. Additionally, several genes that might be related to calcification were identified, including CAMK, CDPK, and CAM and genes encoding alpha-catenin and carbonic anhydrase. This study contributes to our understanding of the effects of temperature on algal calcification and provides a theoretical basis to protect ecological diversity of coral reef ecosystems.

Abstract  The present investigation was aimed to characterize the Ulva blooms and to identify the probable sources for Ulva blooms along the Jeju Island coast for pertinent control measures. Algal isotope signatures (delta C-13, delta N-15 and delta O-18) and tissue nitrogen and carbon were analyzed to map nutrient sources around the Jeju coastal areas. The algal delta C-13 values were ranged from -20.52 to -439 parts per thousand, while delta N-15 and delta O-18 values ranged from 4.26 to 8.29 parts per thousand and 12.80-17.34 parts per thousand, respectively. Moreover, site-specific significant differences were observed in algal stable isotope (delta C-13, delta N-15 and delta O-18) values. The bi-plot (delta N-15 vs delta O-18) diagram indicated four dominant nitrogen sources along the Jeju coast, with 1) soil organic nitrogen mixed with livestock wastes (spring water samples and E), the 2) synthetic fertilizer input (A3 and B2), 3) sewage discharge (D1, D2 and 13) and 4) aquaculture waste (fish farm samples, A4, A5, B1, G and 12). Present findings revealed the different potential nitrogen sources for localized increase of algal growth along the Jeju coast. Finally, the present findings could be used as baseline data for efficient nutrient management to remediate Ulva blooms along Jeju coastal environment. (C) 2019 Elsevier Ltd. All rights reserved.

Abstract  The present study aims to use behavioral responses of the freshwater planarian Girardia tigrina to assess the impact of anthropogenic activities on the aquatic ecosystem of the watershed Araguaia-Tocantins (Tocantins, Brazil). Behavioral responses are integrative and cumulative tools that reflect changes in energy allocation in organisms. Thus, feeding rate and locomotion velocity (pLMV) were determined to assess the effects induced by the laboratory exposure of adult planarians to water samples collected in the region of Tocantins-Araguaia, identifying the sampling points affected by contaminants. Furthermore, physicochemical and microbiological parameters, as well as the presence of inorganic compounds (dissolved aluminum, total barium, total chloride, dissolved iron, total fluoride, total manganese, nitrates, nitric nitrogen, total sulfate, total zinc) and surfactants, were determined on each specific sampling point. The behavioral biomarkers (feeding rate and pLMV) of the freshwater planarians were significantly decreased when organisms were exposed to water samples from four municipalities (Formoso do Araguaia, Lagoa da Confusao, Gurupi and Porto Nacional), sites of the Tocantins-Araguaia hydrographic region-TAHR. Both behavioral biomarkers decreased up to similar to 37-39% compared to organisms in ASTM medium only. Our results showed that these behavioral biomarkers can be used for fast screening monitoring of environmental samples of freshwater ecosystems, since a decrease in feeding rate and locomotor activity was observed in sites impacted by anthropogenic activities. However, the absence of effects observed in some sampling points does not represent the absence of contamination, since several other classes of contaminants were not determined. In these negative results, the absence of deleterious effects on behavioral biomarkers might only be indicative that the potential presence of contaminants on such sites does not significantly affect the performance of planarians. This fast screening approach seems to be useful to determine contaminated sites in freshwater ecosystems for biomonitoring purposes. This knowledge will help to develop biomonitoring programs and to decide appropriate sampling sites and analysis.

Abstract  The shallower oxygen-poor water masses of the ocean confine a majority of the microbial communities that can produce up to 90% of oceanic N-2. This effective N-2-yielding section encloses a suspended small-particle layer, inferred from particle backscattering (b(bp)) measurements. It is thus hypothesized that this layer (hereafter, the b(bp)-layer) is linked to microbial communities involved in N-2 yielding such as nitrate-reducing SAR11 as well as sulfur-oxidizing, anammox, and denitrifying bacteria - a hypothesis yet to be evaluated. Here, data collected by three BGC-Argo floats deployed in the Black Sea are used to investigate the origin of this bbp-layer. To this end, we evaluate how the key drivers of N-2-yielding bacteria dynamics impact the vertical distribution of b(bp) and the thickness of the b(bp)-layer. In conjunction with published data on N-2 excess, our results suggest that the b(bp)-layer is at least partially composed of the bacteria driving N-2 yielding for three main reasons: (1) strong correlations are recorded between bbp and nitrate; (2) the top location of the b(bp)-layer is driven by the ventilation of oxygen-rich subsurface waters, while its thickness is modulated by the amount of nitrate available to produce N-2; and (3) the maxima of both b(bp) and N-2 excess coincide at the same isopycnals where bacteria involved in N-2 yielding coexist. We thus advance that b(bp) and O-2 can be exploited as a combined proxy to delineate the N-2-yielding section of the Black Sea. This proxy can potentially contribute to refining delineation of the effective N-2-yielding section of oxygen-deficient zones via data from the growing BGC-Argo float network.

Abstract  The MCM-41 molecular sieve was synthesized by hydrothermal method and Al was used to modify MCM-41. A series of MnOx/xAl-MCM-41 for NH3-SCR were prepared by impregnating Mn(NO3)(2) onto xAl-MCMM-41 and characterized by XRD, SEM, HRTEM, H-2-TPR, NH3-TPD, XPS and in situ DRTFTS. The results showed that Al doping can significantly change NOx removal ability of MnOx/MCM-41 and achieves above 90% NOx removal efficiency at 200-400 degrees C and about 90% N-2 selectivity at 120-400 degrees C. Introducing of Al into MCM-41 enhances the H2O and SO2 resistance of catalysts and inhibits the non-selective reduction of NO to N2O, but short-range ordered structures of MCM-41 appear distortions because of Al doping. Al doping into MCM-41 cannot change the Mn species (Mn2+, Mn3+ and Mn4+) on the catalyst but it changes redox properties of catalysts. Mn/MCM-41 samples have only Lewis acid sites while Mn/xAl-MCM-41 samples have both Lewis acid sites and Bronsted acid sites. The bridge nitrates are very stable and exist in the entire testing temperature range and mainly adsorbed on Lewis and Bronsted acid sites, while the monodentate nitrates only exist at low temperatures (200 degrees C) and adsorbed on Lewis acid sites, resulting in different reaction paths between NOx and NH3.

Abstract  We evaluated changes in the concentration of cations, anions, nutrients (dissolved organic carbon, DOC; phosphorus, P; and nitrogen forms including nitrate, NO3- and total organic nitrogen, TON), and chlorophyll a (Chl-a) in 31 Tatra Mountain lakes in Slovakia and Poland during their recovery from acidic deposition (1992-2018). Typical effects of decreasing acidic deposition on the lakes' water composition, such as decreasing base cation concentrations, were confounded by climate change and catchment characteristics, including areal proportions of well-developed soils and scree. A climate-related increase in physical erosion provided freshly exposed unweathered granodiorite (the dominant bedrock) to chemical weathering. Dissolution of accessory calcite in the granodiorite increased the in-lake Ca2+ and HCO3- concentrations and reversed the Ca2+ trends, which originally decreased in parallel with strong acid anions. These changes were most pronounced in steep, scree-rich areas, which are most sensitive to physical weathering. Fresh apatite [Ca-5(PO4)(3)(F, Cl, OH)] in the crushed granodiorite acts as a P source at soil pH's between 4 and 5 and in the presence of chelating organic acids within soils. These conditions enhance apatite solubility, which in part explains increasing P in lakes with scree-dominated catchments. Soil recovery from acidification due to decreasing acidic deposition and the neutralizing effect of weathering of erosion-derived accessory calcite were the most likely causes of elevated DOC and P export from soils. Their elevated leaching was accompanied by increasing in-lake concentrations of Chl-a and TON. The increasing TON concentrations were, as for Ca2+, most pronounced in the scree-rich catchments, and represented the most sensitive indicator of the changes in the lake water nutrient composition.

Abstract  Polycyclic aromatic compounds (PACs) such as polycyclic aromatic hydrocarbons (PAHs) and their derivatives [oxygenated PAHs (OPAHs), nitrated PAHs (NPAHs), and azaarenes (AZAs)] are toxic and ubiquitous air pollutants. In this study, the concentrations of these PACs were determined in air obtained in spring and autumn of 2012 from urban and rural areas of the Tibetan Plateau, temperate, subtropical, and tropical climate zones in China. Average concentrations (gaseous + particulate) of ∑29PAHs, ∑15OPAHs, ∑11NPAHs, and ∑4AZAs were 928 ± 658, 54 ± 45, 5.3 ± 4.4, 14 ± 11 ng m-3 and 995 ± 635, 67 ± 38, 8.4 ± 6.1, 24 ± 16 ng m-3 in spring and autumn, respectively. Various C fractions and latitude correlated significantly with the concentrations and ratios of PACs. The slopes of the regression of gas-particle partition coefficients (Kp) of PACs on their sub-cooled liquid vapor pressures (PL0), indicated both adsorption and absorption to total suspended particles (TSP) for PAHs, OPAHs, and NPAHs in the four studied climatic zones. This result was further supported by comparing the fractions of PACs in TSP calculated from field data with those predicted by the Junge-Pankow adsorption and KOA absorption models. The concentration ratios of most OPAHs or NPAHs to their parent PAHs and of benzo[e]pyrene/benzo[a]pyrene were higher in autumn than in spring and increased with remoteness from point sources. This suggests enhanced secondary formation of PAH derivatives due to the elevated photochemical activity in autumn and longer ageing of air and associated transformation of PACs during their long-distance transport from source regions (urban sites) to rural sites. Lifetime lung cancer risk estimated from PACs ranged from 0.8 ± 0.6 to 3.1 ± 1.0 (×10-3), exceeding the value (10-5) recommended by the WHO. Gaseous PACs contributed substantially to the estimated cancer risks and their contributions increased with decreasing latitude in China.

Abstract  Stormwater is increasingly being valued as a freshwater resource in arid regions and can provide opportunities for beneficial reuse via aquifer recharge if adequate pollutant removal can be achieved. We envision a multi-unit operation approach to capture, treat, and recharge (CTR) stormwater using low energy, cost-effective technologies appropriate for larger magnitude, less frequent events. Herein, we tested nutrient, metal, and trace organic contaminant removal of a pilot-scale CTR system in the laboratory using biochar-amended woodchip bioreactors following eight months of aging under field conditions with exposure to real stormwater. Replicate columns with woodchips and biochar (33% by weight), woodchips and straw, or woodchips only were operated with continuous, saturated flow for eight months using water from a watershed that drained an urban area consisting of residential housing and parks in Sonoma, California. After aging, columns were challenged for five months by continuous exposure to synthetic stormwater amended with 50 μg L-1 of six trace organic contaminants (i.e., fipronil, diuron, 1H-benzotriazole, atrazine, 2,4-D, and TCEP) and five metals (Cd, Cu, Ni, Pb, Zn) frequently detected in stormwater in order to replicate the treatment unit operation of a CTR system. Throughout the eight-month aging and five-month challenge experiment, nitrate concentrations were below the detection limit after treatment (i.e., <0.05 mg N L-1). The removal efficiencies for metals in all treatments were >80% for Ni, Cu, Cd, and Pb. For Zn, about 50% removal occurred in the woodchip-biochar systems while the other systems achieved about 20% removal. No breakthrough of the trace organic compounds was observed in any biochar-containing columns. Woodchip columns without biochar removed approximately 99% of influent atrazine and 90% of influent fipronil, but exhibited relatively rapid breakthrough of TCEP, 2,4-D, 1H-benzotriazole, and diuron. The addition of straw to the woodchip columns provided no significant benefit compared to woodchips alone. Due to the lack of breakthrough of trace organics in the biochar-woodchip columns, we estimated column breakthrough with a diffusion-limited sorption model. Results of the model indicate breakthrough for the trace organics would occur between 10,000 and 32,000 pore volumes. Under ideal conditions this could be equivalent to decades of service, assuming failure by other processes (e.g., clogging, biofouling) does not occur. These results indicate that multiple contaminants can be removed in woodchip-biochar reactors employed in stormwater treatment systems with suitable flow control and that the removal of trace organic contaminants is enhanced significantly by addition of biochar.

Abstract  Southern Vietnam is known as one of the most vulnerable areas to climate change in the world due to its low elevation and flat topography, heavy groundwater use, and dense population. This paper introduces hydrogeological conditions and critically reviews groundwater issues that southern Vietnam faces by summarizing previous literatures. Issues that this paper covers include groundwater use and associated phenomenon, acid sulfate soils, the occurrence of saline groundwaters, seawater intrusion, land subsidence, groundwater acidification, and groundwater contamination by nitrate, ammonium, and trace metals such as As, Fe, Mn, Al, Cd, and Pb. This paper shows that most of these issues are inter-related and essentially linked with the unique hydrogeological setting of the study area. However, many of these problems have also been triggered or aggravated by human activities that use water resources and land. Issues such as those of As contamination and groundwater acidification are connected with the aquifer characteristics that are generally confined and rich in organics and pyrite. However, groundwater salinization, acidification, groundwater level declining, land subsidence, and high heavy metal concentrations are in large part caused by human activities such as well installation and heavy groundwater abstraction. While previous studies have proposed artificial recharge as a promising means of mitigating groundwater issues in the study area, the development of techniques that help minimizing aquifer disturbances is also likely required.

Abstract  A traditional rapid infiltration basin (RIB) has been compared to a modified RIB constructed with manufactured biosorption-activated media (BAM) to evaluate nitrate removal from wastewater effluent. The RIBs are used for reclaimed and excess stormwater disposal. In this work, a mixture of clay, tire crumb, and sand (CTS) was selected to serve as the BAM material (Bold and Gold™ CTS media). Each RIB was constructed with two feet of either sand or BAM, covering more than 43,600 square feet of surface area. Over an eight-month period, loadings to the BAM RIB and traditional RIB each approximated 5.4 million gallons (MG) per acre. Water samples collected from lysimeters installed below the 2 foot of sand or BAM materials were analyzed for nutrients. Results suggest that under the conditions of the study BAM removed approximately 31% more nitrate-nitrites and total phosphorus than the traditional RIB. Additionally, BAM removed approximately 18% more total nitrogen than the traditional. PRACTITIONER POINTS: Biosorption-activated media (BAM) removed nitrate-nitrites from reclaimed water more effectively than sand in rapid infiltration basins. BAM could serve as an alternative media for nutrient removal from water prior to release to the environment. Total nitrogen removal was most influenced by NOx removal, with a few removals influenced by TKN. Nutrients could not be effectively removed using BAM or sand from reclaimed water at threshold concentrations below two parts per million.

Abstract  Landfill leachate (LFL) is one of the most serious environmental problems due to the high concentrations of toxic and hazardous matters. Although several physical, chemical, methods have been tested, biological processes and single or multiple-stage combinations of them have been receiving more attention due to their cost-effective and environmentally-friendly manner. The present work recommended coupling of conventional single-stage A/O with moving bed biofilm reactor and membrane bioreactor (AnoxMBBR/AeMBR) for LFL treatment. The system performance was evaluated for 233 d under varying nitrate concentrations (100-1000 mgNO3--N/L), sludge retention time (SRT) (30-90 d), and HRT (24-48 h) in AnoxMBBR, and constant SRT (infinite) and HRT (48 h) in the AeMBR. The best system performances were observed at 1000 mgNO3--N/L concentration, SRT of 90 d and HRT of 48 h, and the average removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and nitrate‑nitrogen (NO3-N) were 74.2%, 99.7%, and 89.1%, respectively. Besides, the AeMBR was achieved above 99% NH4+-N removal and not adversely affected by varying operation conditions of AnoxMBBR. A slight increase in selected phthalic acid ester (PAE) concentrations (diethyl phthalate (DEP), di (2-Ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP)) was detected in the AnoxMBR, and complete PAEs removal was attained in the AeMBR. Mg, Al, Si, Na, Fe was detected by SEM-EDX analyses in both biofilm of AnoxMBBR and the cake layers of AeMBR. Nitrobacter and Nitratireductor which showed a relatively high abundance played an important role in the removal of NH4+-N and COD in LFL. The results confirmed that the proposed sequence is efficient for COD removal, nitrogen removal, and PAEs being an acceptable treatment for landfill leachates.

Abstract  The management of rivers for navigation, hydropower and flood risk reduction involves the installation of in-channel structures. These influence river levels and can affect groundwater flow within hydraulically-connected riparian floodplain aquifers. A comprehensively monitored, peri-urban, lowland river floodplain in the southern United Kingdom was used to explore these dependencies and to examine the implications for the flux exchange of water and nitrate between the river and the floodplain alluvial aquifer. The study demonstrated that rivers maintained at high levels by management structures, result in raised groundwater levels in the adjacent aquifer and complex groundwater flow patterns. Engineered river management structures were shown to promote flow from river to aquifer through the river bed but the majority of the associated nitrate was removed in the hyporheic zone. High-nitrate groundwater recharge to the alluvial aquifer also occurred through overbank flood flows. Across the floodplain, substantial denitrification occurred due to anaerobic conditions resulting from carbon-rich sediments and the shallow water table, the latter linked to the river management structures. An upper limit on the total annual mass of nitrate removed from river water entering the floodplain aquifer was estimated for the study site (2.9 × 104 kg), which was three orders of magnitude lower than the estimate of annual in-channel nitrate flux (1.8 × 107 kg). However, this capacity of lowland floodplains to reduce groundwater nitrate concentrations has local benefits, for example for private and public water supplies sourced from alluvial aquifers. The insights from the study also have relevance for those considering schemes that include the installation, removal or redesign of river management structures, as the resultant change in groundwater levels may have consequences for floodplain meadows and the nutrient status of the aquatic system.

Abstract  Production of defensible modelling tools for aquifer vulnerability mapping under the conditions of sparse data remains topical using the DRASTIC framework. DRASTIC is the acronym for seven data layers using a prescribed scoring system in terms of rates to account for local variations and weights to account for the relative importance of data layers. Also, the term framework signifies the consensual nature of choosing the data layers without any theoretical or empirical basis. Artificial Intelligence (AI) or similar techniques are used to reduce inherent subjectivities through a strategy of unsupervised learning from data by formulating Multiple Frameworks (MF) and supervised learning from Multiple Models (MMs) without searching for any ‘superior’ model. Notably, a framework lacks the procedure for iterative training and testing, as usual in modelling procedures. In this strategy, models are organised in two hierarchical levels: Level 1 comprises the construction of MFs (two frameworks) and/or MMs (two models); Level 2 comprises a model or an algorithm to reuse the outputs from Level 1 through formulating four strategies, including a mixture of MFs/ MMs, in which Support Vector Machine (SVM) is chosen by the paper to run models at Level 2. The supervision process uses target values as a function of observed nitrate-N values. The strategy is applied to the aquifer in the Malekan region, where the past extensive agricultural practices have been transformed into intensive use of fertilisers without protecting water quality in the aquifers. Results show that AIMM/MF lead to significant improvements in delineating high vulnerability areas.

Abstract  Erythrosine and tartrazine are one of the synthetic azo dye mostly consumed in food, drugs and other industrial compounds. This study was designed to investigate the adverse effect of combine erythrosine and tartrazine on cognitive and neurobehavioral functions, pro-oxidants, endogenous antioxidants, cholinergic system and pro-inflammatory cytokines in rats.Erythrosine and tartrazine (2 mg/kg, 6 mg/kg, and 10 mg/kg, b.w., p.o, 50:50) was administered to rats (n = 6) for 6 weeks. Memory and neurobehavioral assessment using Novel object recognition test (NORT) and Elevated plus maze (EPM) and biochemical (pro-oxidants and anti-oxidant enzymes) and pro-inflammatory cytokine measurement from the brain sub regions namely, hippocampus and prefrontal cortex were done at the end of treatment. The results showed (p < 0.05) significant decreased memory and neurobehavioral function, increased acetyl-cholinesterase and pro-oxidants activity (Malonaldehyde level and Nitrite), decreased endogenous anti-oxidants (Glutathione and Catalase) and increased pro-inflammatory cytokines (Tumor necrosis factor-alpha, TNF-a). We suggested that the mechanism by which this oxidative and neuro-inflammatory damage and cholinergic system alteration occur might be related to the release of metabolite in fission of the azo dyes of the combined erythrosine and tartrazine administration in the animals. However, we concluded on these findings that erythrosine and tartrazine dyes significantly provoke the release of oxido-nitrergic and neuroinflammatory stress markers and also may incite acetyl-cholinesterase activities in different brain regions leading to memory and neurobehavioral impairment.

Abstract  The present study demonstrates utilization of secondary agricultural wastes for xylitol production. The highest xylan-to-xylose (70%) conversion was achieved using dilute nitric acid as catalyst followed by resin treatment. Results show that resin treatment efficiently removed nitrate salt (70%), phenolic content and 5-HMF (70%). Highest xylitol yield (85%) was achieved during fermentation using Candida tropicalis MTCC 6192 from the neutralized hemicellulosic hydrolysate medium. Good recovery (>15%) was achieved from corncob with 85% xylose to xylitol conversion during fermentation. This two-step process for transformation of agri-waste to xylitol is much simpler and it could possibly be considered for up scaling after process optimization parameters.

Abstract  The hydrazone (E)-3-hydroxy-N'-(1-(2-oxo-2H-chromen-3-yl)ethylidene)-2-naphthohydrazide (H2L) was synthesized from the reaction of 3-acetylcoumarin and 3-hydroxy-2-naphthoic hydrazide in methanol. Compounds [Mn(H2L)(NO3)(2)(CH3OH)]?CH3OH (1a), [Mn(HL)(NO3)(CH3OH)](n) (1b), [Co(HL)(NO3)(CH3OH)](n) (2), and [Cu(HL)(NO3)] (3) were obtained by reaction of an equimolar amount of H2L with nitrate salts of Mn(II), Co(II), or Cu(II) in methanol. The reaction of ligand and Mn(NO3)(2)4H(2)O was also carried out in the presence of sodium azide which led to the 1-D coordination polymer, [Mn(HL)(N-3)(CH3OH)](n) (4). All of the synthesized compounds were characterized by elemental analyses and spectroscopic methods. Single-crystal X-ray analysis of 1-4 indicated that H2L is neutral (in 1a) or mononegative ligand (in 1b, 2, 3 and 4). In 1b, 2 and 4 the 1-D polymeric chain is found by a rare coordination mode of this kind of hydrazone ligand since the naphtholic oxygen is coordinated to the neighboring metal ions while the NH moiety of hydrazone remains intact, also confirmed by FT-IR spectroscopic studies. The thermal stability of 2 and 4 were also studied from 30-1000 degrees C.

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Abstract  Hydroxylammonium nitrate (HAN) is an energetic ionic liquid which is fast emerging as a promising environmentally friendly, high performing monopropellant for space propulsion application. The high performance due to the higher adiabatic temperature for HAN based compositions also poses challenges as high temperature tolerant catalysts have to be developed for its decomposition. A novel cobalt doped cerium oxide based catalyst has been prepared by the co-precipitation route and characterized by SEM/EDS, XRD, and XPS. The effectiveness of the catalyst in decomposing HAN has been tested using thermo-analytical techniques. An evolved gas analysis (EGA) to examine decomposition products and the possible reaction mechanism was also performed using the hyphenated DTA-TG-FTIR technique. Formation of an in situ Ce3+/Ce4+ ion couple in ceria during co-precipitation was found to be critical in deciding the reactivity of HAN decomposition over the catalyst. The activity of the catalyst was also examined in a batch reactor for its longevity. The prepared catalyst was found to be more versatile and durable than a hitherto reported alumina supported iridium catalyst in the present studies.

Abstract  Cadmium (Cd) contamination in red soil has been considered as a severe threat due to its toxic effects on plants and food security. This study aims to evaluate the comparative efficiency of rice husk-derived biochar (RHB) and steel slag (SS) metal stabilizer on decreasing Cd mobility and bioavailability to Chinese cabbage grown on acidic contaminated red soil. Several extraction techniques: a sequential extraction procedure, the European Community Bureau of Reference, toxicity characteristics leaching procedure, ammonium nitrate, and simple bioaccessibility extraction test were used to measure Cd mobility after amelioration of the investigated soil. The results indicated that application of stabilizer significantly increased soil chemical properties including soil pH, cation exchange capacity, nutrients, and organic matter. The soluble portion of Cd in soil was significantly decreased by 17.6-31.2% and 7.8-11.7% for RHB and SS at 1.5% and 3% application rate, respectively. Moreover, Cd bioaccessibility was significantly declined by 37.08% with RHB and 11.3% with SS at 3% rate. Inlcorporation of RHB at 3% can effectively immobilize Cd and thereby, reduce its phytoavailability to cabbage in Cd-contaminated soil to mitigate food security risks.

Abstract  Mercury is one of the most toxic metals and has global importance due to the biomagnification and bioaccumulation of organomercury via the aquatic food web. The physical and chemical transformations of various mercury species in the atmosphere strongly influence their composition, phase, transport characteristics and deposition rate back to the ground. Modeling efforts to assess global cycling of mercury require an accurate understanding of atmospheric mercury chemistry. Yet, there are several key uncertainties precluding accurate modeling of physical and chemical transformations. We focus this article on recent studies (since 2015) on improving our understanding of the atmospheric chemistry of mercury. We discuss recent advances in determining the dominant atmospheric oxidant of elemental mercury (Hg-0) and understanding the oxidation reactions of Hg-0 by halogen atoms and by nitrate radical (NO3)in the aqueous reduction of oxidized mercury compounds (Hg-II) as well as in the heterogeneous reactions of Hg on atmospheric-relevant surfaces. The need for future research to improve understanding of the fate and transformation of mercury in the atmosphere is also discussed.

Abstract  The factors influencing how soil nitrite (NO2-)- and ammonia (NH3)-oxidizing activities remain coupled are unknown. A short-term study (<48 h) was conducted to examine the dynamics of NO2--oxidizing activity and the accumulation of NO2- in three Oregon soils stimulated by the addition of 1 mM NH4+ in soil slurry. Nitrite initially accumulated in all three soils; its subsequent decline or slowing of the accumulation of the NO2- pool by 24 h was accompanied by an increase in the size of the nitrate (NO3-) pool, indicating a change in NO2- oxidation kinetics. Bacterial protein synthesis inhibitors prevented the NO2- pool decline, resulting in a larger accumulation in all three soils. Although no significant increases in NO2--oxidizing bacteria nxrA (Nitrobacter) and nxrB (Nitrospira) gene abundances were detected over the time course, maximum NO2- consumption rates increased 2-fold in the treatment without antibiotics compared to no change with antibiotics. No changes were observed in the apparent half saturation constant (Km) values for NO2- consumption. This study demonstrates phenotypic flexibility among soil NO2- oxidizers, which can undergo protein synthesis-dependent increases in NO2- consumption rates to match NH3 oxidation rates and recouple nitrification.

Abstract  Large-scale agricultural land reclamation activities can trigger substantial changes in the soil bacterial community by disturbances associated with growth of crops and addition of fertilizers and pesticides. In this study, the bacterial 16S gene was sequenced on the Illumina MiSeq platform for bacterial identification and taxonomy. We investigated the (i) soil bacterial diversity and community composition in natural marsh, moderate and severe intensity of interference in wetlands, and (ii) the relationship between soil physical and chemical properties, and soil bacterial community structures in order to understand the effects of interference intensities on the marsh soil environment in the Sanjiang Plain wetland, Northeast China. The natural marsh soil contained most of 573 operational taxonomic units (OTUs) between all the three sites (n=1241), while wetland soils of moderate and severe intensity of interference had only 510 and 401 OTUs, respectively. The soil bacterial diversity and richness indices of all disturbed wetlands presented a decline at the OTU level, alpha diversity (Shannon diversity and Chao and Ace diversities). In addition, the composition of soil bacterial communities showed different trends and structure after the disturbance. There were significant variation in unclassified genera and some dominant genera (relative abundance>1% in at least one site) between natural marsh and difference in interference intensities in disturbed wetlands, including Acidobacteria, Proteobacteria, Verrucomicrobia, Actinobacteria, Chlorobi and Gemmatimonadetes. Composition of soil bacterial community was affected by Soil Moisture, pH, Soil Organic Carbon, Total Nitrogen, Available Nitrogen, Total Phosphorus, Available Phosphorus, Total Potassium, Nitrate Nitrogen, Available Potassium and Ammonium Nitrogen. This study will provide a fundamental scope to understand the bacterial community structure in wetland ecosystems and the environmental function as a predictor of bacterial community composition. (C) 2018 Friends Science Publishers