Abstract  Bioaugmentation was used to upgrade the nitrification process in a full-scale municipal WWTP with an A2/O system. A mixture of nitrifying bacteria was inoculated into the bioreactor for a final concentration of 1% (v/v). The upgrade process took 25 days, and the NH4+-N removals reached 94.6% (increased at least by 75%). The effluent concentrations of COD and NH4+-N stabilized at <30 mg/L and <4 mg/L even when the corresponding influent concentrations were over 300 mg/L and 60 mg/L, which met the first-class requirement of the National Municipal Wastewater Discharge Standards of China (COD ≤ 50 mg/L, NH4+-N ≤ 5 mg/L). The succession of the microbial community showed the enhanced NH4+-N removal efficiency mainly resulted from the persistence of introduced ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), which increased from 0% to 0.4% and from 0.01% to 2.1%, respectively. This bioaugmentation was shown as an effective technology for upgrading or retrofitting conventional systems to tertiary-level.

Abstract  RATIONALE: The isotopic tracer technique is widely used to identify the sources and fate of nitrogen (N) in order to understand the N cycle and contamination in water environments. The stable isotope ratio of ammonium is expected to greatly enhance the tracing analysis by combining it with the traditional nitrate isotope ratio. Diffusion followed by gas-phase trapping is the most commonly applied method for ammonium isotope ratio measurement. Although dissolved organic nitrogen (DON) is abundant in natural water and its breakdown in the diffusion procedure has been reported, the interference of DON with the measurement of ammonium isotope ratios has not been fully examined.

METHODS: This study aims to test the effect of DON contamination by using organic N compounds, viz. humic acid and alanine. A series of diffusion experiments was conducted at a temperature of 80°C for a maximum of 7 days. Ammonia was transferred from alkaline solution and trapped with an acidic filter. This method was applied for samples with ammonium concentrations between 0.5 and 2.0 mg-N/L.

RESULTS: There was no difference between the ammonium N stable isotope ratios for samples with and without added DON compounds; the fractionation between the observed value and the actual value was negligible, in the range of 0.2 to 1.0‰. The modifications of previous studies, i.e. shorter diffusion period, no vigorous shaking and using gas-phase trapping, successfully avoided any breakdown of DON in fresh water samples.

CONCLUSIONS: The modified method provides high precision and accuracy and it is recommended for the analysis of anthropogenically influenced water samples, such as paddy fields, ground water, rivers and lakes.

Abstract  Although Nitrobacter winogradskyi is an important chemoorganotrophic organism for the study of nitrite-oxidizing bacteria physiology as well as nitrification, until now, the mixotrophic medium for this organism growth has not been optimized, comprehensively. In this study, we aimed to improve the growth medium of N. winogradskyi using the one-factor-at-a-time (NaNO2 , glycerol, pH) method. In addition, a further experimental design was carried out based on central composite design with response surface methodology. Different combinations of the three cultural parameters were fitted by multiple regression analysis to calculate the predicted response. Our results suggest that optimal culture condition for the growth of N. winogradskyi was a modified DSMZ 756a medium containing NaNO2 (5·74 g l-1 ) and glycerol (37·88 mmol l-1 ), pH 7·83, a temperature of 28°C and agitation at 120 rev min-1 . The results from a validation experiment (bacterial growth: OD600 1·0293) were close to the value predicted by the quadratic model (OD600 1·0994). In addition, we uncovered the potential mechanism at the cellular and ultrastructural levels. The results indicated that glycerol in the media enhanced the rate of cell division and cell growth by increasing the accumulation of polyphosphates and phosphorus, and high concentrations of NaNO2 provided sufficient energy for growth and contributed to the generation of carboxysomes in cells for CO2 fixation.

SIGNIFICANCE AND IMPACT OF THE STUDY: Due to the extremely slow growth rate and the low growth yield of ammonia-oxidizing bacteria and NOB (nitrite-oxidizing bacteria), nitrification is still the rate-limiting step of nitrogen cycle in the current research. Nitrobacter winogradskyi, an important NOB, participates in the second step of nitrification in water and soil. This study reported an optimized culture condition for N. winogradskyi, which increased the growth yield by 5·06 times than that in the basal medium and uncovered the potential mechanism. We expect our study will contribute to the research on water and soil nitrogen cycle. In addition, the optimized culture conditions have the potential to be suitable for the chemoorganotrophic growth of other nitrifiers.

Abstract  Poly-γ-glutamic acid (γ-PGA) is an important multifunctional biopolymer with various applications, for which adenosine triphosphate (ATP) supply plays a vital role in biosynthesis. In this study, the enhancement of γ-PGA production was attempted through various approaches of improving ATP supply in the engineered strains of Bacillus licheniformis. The first approach is to engineer respiration chain branches of B. licheniformis, elimination of cytochrome bd oxidase branch reduced the maintenance coefficient, leading to a 19.27% increase of γ-PGA yield. The second approach is to introduce Vitreoscilla hemoglobin (VHB) into recombinant B. licheniformis, led to a 13.32% increase of γ-PGA yield. In the third approach, the genes purB and adK in ATP-biosynthetic pathway were respectively overexpressed, with the AdK overexpressed strain increased γ-PGA yield by 14.69%. Our study also confirmed that the respiratory nitrate reductase, NarGHIJ, is responsible for the conversion of nitrate to nitrite, and assimilatory nitrate reductase NasBC is for conversion of nitrite to ammonia. Both NarGHIJ and NasBC were positively regulated by the two-component system ResD-ResE, and overexpression of NarG, NasC, and ResD also improved the ATP supply and the consequent γ-PGA yield. Based on the above individual methods, a method of combining the deletion of cydBC gene and overexpression of genes vgB, adK, and resD were used to enhance ATP content of the cells to 3.53 μmol/g of DCW, the mutant WX-BCVAR with this enhancement produced 43.81 g/L of γ-PGA, a 38.64% improvement compared to wild-type strain WX-02. Collectively, our results demonstrate that improving ATP content in B. licheniformis is an efficient strategy to improve γ-PGA production.

Abstract  The mature landfill leachate containing high ammonia concentration (>1000 mg/L) is a serious threat to environment; however, the low COD to TN ratio (C/N, <3) strongly inhibits the denitrification process and poses a severe obstacle for efficient treatment. Herein, two kinds of acidogenic liquids, fermented from oil-removed food waste and oil-added food waste, were first applied as external carbon sources for the biological nitrogen removal from mature landfill leachate in an aerobic/anoxic membrane bioreactor. "Acidogenic liquid b" served quite better than commercial sodium acetate, considering the higher denitrification efficiency and the slightly rapider denitrification rate. The effect of C/N and temperature were investigated under hydraulic retention time (HRT) of 7 d, which showed that C/N ≥ 7 (25 °C) was enough to meet the general discharge standards of NH4+-N, TN and COD in China. Even for some special areas of China, the more stringent discharge standards (NH4+-N ≤ 8 mg/L, TN ≤ 20 mg/L) could also be achieved under longer HRT of 14 d and C/N ≥ 6. Notably, the COD concentration in effluent could also be well reduced to 50-55 mg/L, without further physical-chemical treatment. This proposed strategy, involving the high-value utilization of food waste, is thus promising for efficient nitrogen removal from mature landfill leachate.

Abstract  Nitrification plays a crucial role in global nitrogen cycling and treatment processes. However, the relationships between the nitrifier guilds of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) are still poorly understood, especially in freshwater habitats. This study examined the physiological interactions between the AOB and NOB present in a freshwater aquarium biofilter by culturing them, either together or separately, in a synthetic medium. Metagenomic and 16S rRNA gene sequencing revealed the presence and the draft genomes of Nitrosomonas-like AOB as well as Nitrobacter-like NOB in the cultures, including the first draft genome of Nitrobacter vulgaris. The nitrifiers exhibited different growth rates with different ammonium (NH4+) or nitrite concentrations (50-1,500 μM) and the growth rates were elevated under a high bicarbonate (HCO3-) concentration. The half-saturation constant (Ks for NH4+), the maximum growth rate (μmax), and the lag duration indicated a strong dependence on the synergistic relationships between the two guilds. Overall, the ecophysiological and metagenomic results in this study provided insights into the phylogeny of the key nitrifying players in a freshwater biofilter and showed that interactions between the two nitrifying guilds in a microbial community enhanced nitrification.

Abstract  Two lab-scale nitrifying sequencing batch biofilm reactors, with (SBBR_CN) or without the addition of organics (SBBR_N), were operated to investigate potential roles of acyl homoserine lactone (AHL) based quorum sensing. AHLs of N-[(RS)-3-Hydroxybutyryl]-L-homoserine lactone, N-hexanoyl-L-homoserine lactone (C6-HSL) and N-octanoyl-L-homoserine lactone (C8-HSL) were detected in both reactors. C6-HSL and C8-HSL were also detected in batch experiments, especially with stimulated nitrite oxidizing bacteria activities. Quorum sensing affected biofilm formation mainly through the regulation of extracellular protein production. By the metagenomics analysis, many identified genera and species could participate in quorum sensing, quorum quenching and extracellular polymeric substances (EPS) production. A high quorum quenching activity was obtained in SBBR_CN, whereas a high quorum sensing activity in SBBR_N. Nitrosomonas-like ammonia oxidizing bacteria, Nitrospira-like nitrite oxidizing bacteria and Comammox harbored genes for AHL synthesis and EPS production. Possible relationships among AHLs synthesis, biofilm formation and nitrifiers activity were proposed.

Abstract  The present in vivo randomized, triple-blinded, and split-mouth clinical study evaluated the effectiveness of a hybrid light (HL) source on the color change, stability, and tooth sensitivity in patients submitted to different in-office bleaching techniques. Twenty volunteers were divided into two groups and four subgroups. A split-mouth design was conducted to compare two in-office bleaching techniques (with and without light activation): 35% Lase Peroxide Sensy (LPS) + HL: 35% hydrogen peroxide (HP) + HL; 35% LPS: 35% HP; 25% LPS + HL: 25% HP + HL; and 35% Whiteness HP (WHP): 35% HP. For the groups activated with HL, the HP was applied on the enamel surface three consecutive times using a 3 × 2-minute protocol (three HL activations for two minutes each, with a 30-second interval for a total of seven minutes and 30 seconds) for each gel application, totaling 22 minutes and 30 seconds. For the other groups, HP was applied 3 × 15 minutes, totaling 45 minutes. A spectrophotometer was used to measure the color change (ΔE) before the treatment and 24 hours, one week, and one, 12, and 36 months after. A visual analog scale was used to evaluate the tooth sensitivity before the treatment, immediately following treatment, 24 hours, and one week after. Analysis of variance, Tukey's, Kruskall-Wallis, and Wilcoxon tests, all with α = 0.05 were performed. Statistical analysis did not reveal any significant differences (ΔE) between the in-office bleaching techniques with or without HL in the periods evaluated; the activation with HL required 50% less time to achieve such results. The groups without HL presented statistical differences for ΔE when comparing 24 hours with the other follow-up times (intergroup) and an increase in tooth sensitivity in the initial periods. All techniques and bleaching agents were effective on bleaching during a 36-month evaluation of color stability. The groups activated with HL presented lower sensitivity and required a lower activation time.

Abstract  Activated carbon (AC) was modified by ammonium persulphate or nitric acid, respectively. AC and the modified materials were used as catalyst supports. The oxygen groups were introduced in the supports during the modifications. All the supports were characterized by N-2-physisorption, Raman, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis. Methanol synthesis catalysts were prepared through wet impregnation of copper nitrate and zinc nitrate on the supports followed by thermal decomposition. These catalysts were measured by the means of N-2-physisorption, X-ray diffraction, XPS, temperature programmed reduction and TEM tests. The catalytic performances of the prepared catalysts were compared with a commercial catalyst (CZA) in this work. The results showed that the methanol production rate of AC-CZ (23 mmol-CH3OH/(g-Cu center dot h)) was higher, on Cu loading basis, than that of CZA (9 mmol-CH3OH/(g-Cu center dot h)). We also found that the modification methods produced strong metal-support interactions leading to poor catalytic performance. AC without any modification can prompt the catalytic performance of the resulted catalyst.

Abstract  The potential of simultaneous removal of nitrate and phosphate from wastewater by a single anaerobic Fe(II) oxidizing denitrifiers (the strain PXL1) was assessed using siderite biofilters under different influent TOC concentrations and hydraulic retention times (HRTs) over a 160-day trial. Higher TOC concentrations promoted NO3- removal, while there was no significant influence on PO43- removal. Lowering down HRT from 10 h to 5 h did not significantly influence NO3- and PO43- removal. The NO3- removal performance and microbial community structure in the biofilters indicated that NO3- was reduced to N2 by both strain PXL1 and heterotrophic Acidovorax delafieldii. Iron content analysis of the used siderite along the biofilters showed that PO43- removal was improved by the bio-oxidation of Fe(II) in siderite to Fe(III) via the strain PXL1. The coexistence of the strain PXL1 and natural siderite in nitrate-contaminated aquifers provides a practical technology for in situ remediation of nutrient contaminated waterbodies.

Abstract  Arbuscular mycorrhizal fungi (AMF) are mutualistic symbionts considered a key group in soil systems involved in the provision of several ecosystem services. Recently they have been listed by EFSA as organisms to be included in the test battery for the risk assessment of plant protection product (PPPs). This study aimed to contribute to improve the ISO Protocol (ISO 10832: 2009) by assessing the feasibility of using other AMF species under different test conditions. Overall, results showed that AMF species Gigaspora albida and Rhizophagus clarus (selected out of five AMF species) are suitable to be used in spore germination tests using the ISO protocol (14 days incubation with sand or artificial soil as substrate) to test PPPs. However, several modifications to the protocol were made in order to accommodate the use of the tested isolates, namely the incubation temperature (28 °C instead of 24 °C) and the change of reference substance (boric acid instead of cadmium nitrate). The need for these changes, plus the results obtained with the three fungicides tested (chlorothalonil, mancozeb and metalaxyl-M) and comparisons made with literature on the relevance of the origin of AMF isolates in dictating the adequate test conditions, emphasize the importance of adjusting test conditions (AMF species/isolates and test temperature) when assessing effects for prospective risk assessment targeting different climatic zones. So, further studies should be conducted with different AMF species and isolates from different climatic regions, in order to better define which species/isolate and test conditions should be used to assess effects of a particular PPP targeting a given climatic zone.

Abstract  Progress on reducing nutrient loss from annual croplands has been hampered by perceived conflicts between short-term profitability and long-term stewardship, but these may be overcome through strategic integration of perennial crops. Perennial biomass crops like switchgrass can mitigate nitrate-nitrogen (NO3-N) leaching, address bioenergy feedstock targets, and - as a lower-cost management alternative to annual crops (i.e., corn, soybeans) - may also improve farm profitability. We analyzed publicly available environmental, agronomic, and economic data with two integrated models: a subfield agroecosystem management model, Landscape Environmental Assessment Framework (LEAF), and a process-based biogeochemical model, DeNitrification-DeComposition (DNDC). We constructed a factorial combination of profitability and NO3-N leaching thresholds and simulated targeted switchgrass integration into corn/soybean cropland in the agricultural state of Iowa, USA. For each combination, we modeled (i) area converted to switchgrass, (ii) switchgrass biomass production, and (iii) NO3-N leaching reduction. We spatially analyzed two scenarios: converting to switchgrass corn/soybean cropland losing >US$ 100 ha(-1) and leaching >50 kg ha(-1) (conservative scenario) or losing >US$ 0 ha(-1) and leaching >20 kg ha(-1) (nutrient reduction scenario). Compared to baseline, the conservative scenario resulted in 12% of cropland converted to switchgrass, which produced 11 million Mg of biomass and reduced leached NO3-N 18% statewide. The nutrient reduction scenario converted 37% of cropland to switchgrass, producing 34 million Mg biomass and reducing leached NO3-N 38% statewide. The opportunity to meet joint goals was greatest within watersheds with undulating topography and lower corn/soybean productivity. Our approach bridges the scales at which NO3-N loss and profitability are usually considered, and is informed by both mechanistic and empirical understanding. Though approximated, our analysis supports development of farm-level tools that can identify locations where both farm profitability and water quality improvement can be achieved through the strategic integration of perennial vegetation.

Abstract  Groundwater pollution is a serious worldwide concern. Aromatic compounds, chlorinated hydrocarbons, metals and nutrients among others can be widely found in different aquifers all over the world. However, there is a lack of sustainable technologies able to treat these kinds of compounds. Microbial electro-remediation, by the means of microbial electrochemical technologies (MET), can become a promising alternative in the near future. MET can be applied for groundwater treatment in situ or ex situ, as well as for monitoring the chemical state or the microbiological activity. This document reviews the current knowledge achieved on microbial electro-remediation of groundwater and its applications.

Abstract  The completely autotrophic nitrogen removal over nitrite (CANON) process is an important component of energy self-sufficient sewage treatment plants, and the use of aerobic granular sludge is a profitable choice for the CANON process. In this study, the performance and microbial characteristics of CANON granular sludge were investigated for treating synthetic and mainstream domestic sewage. The average nitrogen removal rate (NRR) was 3.22 kg Nm(-3) d(-1) during the high-rate operating period with high MLSS (4.09 g L-1) and DO (similar to 1.0 mg L-1) for treating synthetic sewage. When the influent was mainstream sewage, the average NRR was 1.11 kg Nm(-3) d(-1). The effluent nitrate concentration was very low, and nitrate build-up was not found. High-throughput pyrosequencing results indicated that, Nitrosomonas and Candidatus Brocadia were the dominant genus in ammonia oxidizing bacteria (AOB) and anaerobic AOB (AAOB), respectively. The proportions of AOB and AAOB decreased during mainstream sewage treatment, but the reactor maintained good performance. The results confirmed the feasibility of using CANON granular sludge for treating mainstream sewage.

Abstract  In this study, an electrochemical-adsorption (ECA) system was constructed by packing iron particles and zeolites between electrodes to simultaneously remove nitrate and its by-products without excessive active chloride accumulation. Response surface methodology (RSM) with Box-Behnken design (BBD) was applied to investigate the effects of independent variables (iron particle, zeolite and current density) and their interaction on the system performance, also determining its optimum working state. The optimal conditions for the amount of iron particles (19.74g) and zeolites (28.19g) as well as the current density (18.72 mA/cm(2)) resulted in a high nitrate removal efficiency of 95% and merely a little ammonia accumulation. Polarized iron particles could provide more reactive sites and increase mass transfer efficiency, thus promoted nitrate reduction and decreased energy consumption. Synergistic effects of electrolysis and zeolite adsorption accelerated ammonium removal by increasing the rate of ion directional migration. The system having low operation costs and no secondary pollution appeared to be an advisable enhancing strategy for removing nitrate and by-products. (C) 2018 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Abstract  Pastoral agriculture is a major source for nitrate (contamination in surface and ground waters and for the greenhouse gas emissions in New Zealand. Advances have been made in recent years in understanding the role of different ammonia oxidisers, including ammonia oxidising bacteria (AOB) and ammonia oxidising archaea (AOA) in nitrification, and in developing nitrification inhibitor (NI) mitigation technologies. Results showed that, in the N-rich soil environment under the animal urine patches in grazed grassland, AOB are the dominant microbes responsible for ammonia oxidation whereas AOA play a less important role. A number of laboratory and field studies have demonstrated conclusively that treating grazed pasture soils with a nitrification inhibitor (NI), such as dicyandiamide (DCD), which inhibits the growth and activity of AOB, is an effective means of reducing NO3- leaching and N2O emissions.

Abstract  A series of dealuminated ZSM-5 zeolite (deAlZSM-5) supported Fe-based catalysts are prepared by a modified solid-state ion exchange method, in which the HZSM-5 zeolite is dealuminated by concentrated HNO3 and subsequently ground with ferric nitrate. The physicochemical properties of the resultant Fe/deAlZSM-5 catalysts are characterized by XRD, N-2 sorption, TEM, H-2-TPR and NH3-TPD techniques. It is revealed that the Fe species are highly dispersed in the deAlZSM-5, and would be transformed into elemental Fe nanoparticles after reduction by H-2. Due to the confinement effect of ZSM-5 zeolite, the Fe/deAlZSM-5 catalysts exhibit high catalytic activity and excellent stability for NH3 decomposition. At 650 degrees C, about 100% NH3 conversion can be achieved over the 9%Fe/deAlZSM-5 catalysts for 50 h time-on-stream, demonstrating a very promising catalyst system in NH3 decomposition.

Abstract  The purpose of this work was to reveal the Chironomid larvae bioturbation impact on N release and to find the mechanism of bioturbation to N conversion at the SWI (sediment-water interface). Sampling at four points during a 35-day incubation experiment was conducted. Two in situ techniques (microelectrode and Peeper) were used to capture more realistic and accurate microenvironment information around U-shaped corridors. The results demonstrate that the concentrations of ammonia nitrogen (NH4+) and nitrate nitrogen (NO3-) decreased by 21.26% and 19.50% in sediment and increased by 8.65% and 49.82% in the overlying water compared to the control treatment, respectively. An inverse relationship was observed between NH4+ and NO3- concentrations in pore water in Chironomid larvae treatment, and they were significantly negatively/positively correlated with AOB (ammonia-oxidizing bacteria) abundance, respectively. This study confirmed that the Chironomid larvae bioturbation promoted the N (NH4+ and NO3-) release from sediment by in situ techniques, and a part of NH(4)(+)converted into NO3- during their flow into the overlying water through the nitrification affected by AOB. Furthermore, the main depth of bioturbation influence is approximately 12 cm below the SWI and the most significant bioturbation effect was observed from days 15 to 25.

Abstract  A variety of 1,1-diacetates have been chemoselectively and efficiently deprotected to the corresponding aldehydes as well as deprotected and concomitantly reduced to the corresponding alcohols in high yields at ambient temperature with nickel boride generated in situ using different molar ratios of sodium borohydride and nickel (II) chloride in methanol at room temperature. Deprotection and reduction of a variety of aromatic, aliphatic and heterocyclic acylals have been achieved efficiently. Mild reaction conditions, easy work-up, high yields and chemoselectivity demonstrate the efficiency of this new method.

Abstract  Bio-cathode denitrification is a new and unique technology for autotrophic nitrogen removal, which uses electricity instead of chemical matter as electron donor. Functional microorganisms are the driver of bio-cathode denitrification and inocula are the origin of functional microorganisms, so three typical inocula, denitrifying, denitratating and anammox (anaerobic ammonia oxidizing) sludge, were chosen to investigate their effect on the performance of bio-cathode denitrification in this work. The results showed that the nitrogen removal rate of denitrifying, denitratating and anammox bio-cathodes was around 101.79 mg/L.d, 47.31 mg/L.d and 100.04 mg/L.d respectively. The output power was 24.01 mW/m(2), 14.11 mW/m(2) and 45.93 mW/m(2). The denitrifying, denitratating and anammox biofilms were observed to grow on cathodes, indicating that the functional microorganisms could use electricity as the sole electron donor and so they were named as electrotrophic microorganisms. The growth rate and the cell yield of denitrifying, denitratating and anammox biofilms were 24 g/m(2).d and 1.71 x 10(-3) g/g NO3--N, 7.67 g/m(2).d and 1.94 x 10(-3) g/g NO3--N, 41 g/m(2).d and 2.32 x 10(-3) g/g NO2--N, respectively. Pseudomonas, Glycocaulis and SM1A02 were found to be enriched in the three biofilms, and Pseudomonas stutzeri was deduced to be the key functional microorganism. Denitrifying sludge was the optimal inoculum when wastewater treatment was the main purpose; however, Anammox sludge turned to be the optimal inoculum when wastewater treatment and energy recovery were combined. The functional microorganisms and their metabolic characteristics were revealed to be the critical factor that determined the enrichment of electrotrophic microorganisms from inocula and the performance of bio-cathode denitrification. These findings are significant to get an insight into the new electrotrophic microorganism and to develop the novel bio-cathode denitrification technology.

Abstract  Water storage pit (WSP) irrigation is a simple and inexpensive technology suitable for orchards in semiarid and arid regions of North China. This study compared the effects of different fertigation strategies on water and nitrogen distribution, and ammonia volatilization. A fertigation experiment was conducted using a 30 degrees wedge-shaped plexiglass soil container, which represents one-twelfth of the complete storage pit. The height of the container was 120 cm, and a plexiglass damper for simulating the zero flux plane of adjacent water storage pits was located at the 40 cm radius. Four fertigation strategies were used for WSP irrigation: solution application during the first half (N-W), the last half (W-N), the middle half of an irrigation cycle (W-N-W), and during the entire irrigation (N-N). Surface (SF) irrigation was used as a control treatment with solution application during the entire irrigation (SN-N). The experimental results showed that the soil water and ammonium contents at 0-10 cm soil depth under WSP irrigation were only 10.51% and 18.42% of those under SF irrigation, respectively. The cumulative NH3 volatilization under WSP irrigation was 51.71%-68.72% lower compared with that under SF irrigation. The soil water distributions were similar for all four fertigation strategies. NH3 volatilization mainly occurred at the pit wall interface, and cumulative NH3 volatilization loss followed the trend N-N > W-N > W-N-W > N-W. Ammonium was adsorbed into the soil and thus mostly remained near the pit wall. Low concentrations of ammonium were found near the edge of the wetting zone under all strategies. Compared to N-W, N-N and W-N-W treatments, W-N treatment decreased the nitrate accumulation at 80-90 cm by 38.6%, 19.0% and 10.3%, respectively. The W-N strategy was suggested for minimizing potential nitrate leaching.

Abstract  External carbon source is needed for biofloc system to maintain an optimal C/N ratio for the growth of bacteria biomass. In this study, three solid-phase biodegradable compounds, including Longan powder (LP), poly-hydroxybutyrate- hydroxyvalerate/LP (PHBVL) and Poly(butylene succinate)/LP (PBSL), were utilized to feed biofloc-based aquaculture systems in triplicates for nine Nile tilapia (Oreochromis niloticus) larvae culture tanks. LP was applied in the in-situ biofloc system as a "control group" (3 tanks), while PHBVL and PBSL were used in the ex-situ biofloc systems (6 tanks). During the 120-days experiment, the C/N ratio was maintained at 24.87 +/- 5.66, 22.93 +/- 3.20 and 23.12 +/- 3.54 for the LP, PHBVL and PBSL groups, respectively. There were no significant differences (P >.05) of the averaged total ammonia nitrogen (TAN) concentration among the LP, PHBVL and PBSL groups (1.10 +/- 1.18, 0.67 +/- 0.38 and 1.18 +/- 1.40 mg L-1). Significant differences of the averaged NO2--N concentrations (0.26 +/- 0.38, 0.01 +/- 0.01 and 0.08 +/- 0.12 mg L-1) were detected among the LP, PHBVL and PBSL groups (P < .05). The accumulation of NO3--N in LP group (> 40 mg L-1 on day 120) was significantly higher than that of PHBVL and PBSL groups (about 2-3mg L-1 on day 120) (P < .05). To characterize the quality of biofloc, the median diameters (D50) and essential amino acids index (EAAI) were measured for three treatments. The D50 (124.7 +/- 4.24, 131.6 +/- 2.83 and 175.5 +/- 9.19 mu m) and EAAI (0.969 +/- 0.011, 1.007 +/- 0.014 and 0.995 +/- 0.012) showed that the high quality bioflocs in the LP, PHBVL and PBSL groups could meet the requirement for feeding the aquatic animals. In addition, high throughput sequencing test showed that solid carbon source not only had a significant effect on the microbial community in bioflocs, but also on the composition of fish gut microbiota. Bacillus was the dominating genus discovered in all treatments (48.34% in LP, 49.24% in PHBVL and 50.47% in PBSL) by 16S rRNA sequencing. Overall, blending LP with biodegradable polymers as carbon source showed significantly higher removal efficiency of nitrate and nitrite nitrogen, and higher biofloc quality than using LP as the only carbon source. How exactly various solid carbon sources influence fish growth performance and health need further study.

Abstract  The environmental impact of irrigated agriculture on water quality was assessed in Landazuria watershed (Navarre, northeast Spain), a 479.5 ha watershed with 53% of irrigated agricultural land. In the framework of a long-term monitoring program, precipitation and discharge were measured at 10-min intervals and compound daily water samples were collected during the agricultural years (September to August) 2007-2016, and analysed for nitrate (NO3-), phosphate (PO43-), sediment and total dissolved solids (TDS) concentrations. Typical agricultural management (including crop surfaces, irrigation and fertilization rates) was obtained from inquiries to farmers. Concentration and yield of the studied variables presented a high degree of variation, both intra- and inter-annual. Median concentration for the entire study period were 185, <0.05, 31 and 2284 mg L-1 for NO3-, PO43-, sediment and TDS, respectively. NO3--N and PO43--P yields averaged 74 and 0.04 kg ha(-1) year(-1), respectively. NO3--N yield was higher than in other agricultural land uses in Navarre and in the order of magnitude of other irrigated areas in the Middle Ebro Valley. PO43--P yield was in the same order of magnitude than in rainfed watersheds in Navarre but lower than in intensively grazed watersheds. Sediment yield was extremely variable, averaging 360 kg ha(-1) year(-1)D, with 44% of the total measured load recorded in a few days. It was in the lower range of those measured in Navarre for rainfed agriculture and similar to those estimated in other irrigated areas of the Middle Ebro River. TDS concentration presented a significant decreasing trend since available salts were being washed out, while TDS yield averaged 1.8 Mg ha(-)1 year(-)1. Long-term monitoring of irrigated areas is required to understand pollution processes in these agroecosystems and to adequately characterize the environmental impact of current agricultural practices on water quality, in order to implement, and adequately assess, measures to reduce agricultural pollution. (C) 2017 Elsevier B.V. All rights reserved.

Abstract  The use of the heteroleptic [Cr-III(AA)(CN)(4)]-complexes as ligands towards the preformed [Mn-II(tptz)](2+) and [Mn-II(pyim)(2)](2+) species afforded the heterometallic compounds of formula [Mn-II(tptz)(H2O)(NO3)(mu-NC)Cr-III(ampy)(CN)(3)]center dot CH3CN (1), [Mn-II(tptz)(H2O)(NO3)(mu-NC) Cr-III(phen)(CN)(3)]center dot H2O (2) and {[Mn-II(pyim)(2)][(mu-NC) Cr(phen)(CN)(3)](2)}center dot 3H(2)O (3) [AA = 2-amino-methylpyridine (ampy) and 1,10-phenanthroline (phen), tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine and pyim = 2-(1H-imidazol-2yl) pyridine]. 1 and 2 are neutral heterodinuclear complexes, where the [Cr-III(AA)(CN) 4]-building block acts as a monodentate ligand through one of its four cyanido groups towards a manganese(II) ion with seven coordination sites completed by a tridenate tptz molecule, a bidentate nitrate anion and a water molecule. Compound 3 is a neutral heterotrinuclear complex made up by two peripheral [Cr-III(AA)(CN)(4)](-) units acting as monodentate ligands through one of their cyanido groups towards an inner [Mn-II(pyim)(2)](2+) entity. Each manganese(II) ion in 3 is six-coordinate with two cyanido nitrogen atoms and two bidentate pyim molecules, building a distorted octahedral surrounding. The values of the Cr-III-Mn-II distance across the bridging cyanido ligand are 5.3766(7) (1), 5.3194(6) (2) and 5.3245(8) and 5.4538(7) angstrom (3). The magnetic properties of 1-3 were investigated in the temperature range 1.9-300 K. Overall antiferromagnetic behaviour is observed for all three compounds, with the antiparallel alignment of the local spins leading to either a ground-state spin triplet (1 and 2) or a spin doublet (3). The values of the magnetic coupling between the Cr-III and Mn-II ions across the single cyanido bridges are J = -7.40(2) (1), -6.65(2) (2) and -6.41(2) and -4.65(2) cm(-1) (3), with the spin Hamiltonian being defined as H = -J(S-Cr1 center dot S-Mn1) (1 and 2) and H = -J(1)(S-Cr1 center dot S-Mn1) - J(2)(S-Cr2 center dot S-Mn2) (3). These values could be correlated with the Mn-N-Ccyanido angle, and they agree with those reported for this exchange pathway in other magnetostructural studies.

Abstract  The main aim of this study was to determine the possibility of using a rat tapeworm, Hymenolepis diminuta as a bioindicatortor of organic and inorganic lead forms. The bioaccumulation of cadmium and zinc were determined as well. The influence of this parasite was determined regarding to the concentration of elements in the tissues of a definitive host, the white rat (Rattus norvegicus). Male Wistar rats were experimentally infected with H. di-minute and exposed to two different forms of lead (lead nitrate and lead bounded in Pistia stratiotes) for six weeks via oral exposure of the host. After the exposure period, the element levels were determined in the rat (liver, kidney, spleen, testes, muscles, bones and intestine) and tapeworm tissues with ICP-OES. Tapeworms in Pistia group accumulated 135.2, 98.4, 83.2, 45.1, 38.6 and 25.8 times more Pb concentrations than their hosts muscle, testes, intestine, liver, kidney and spleen, respectively. In Nitrate group, tapeworms accumulated from 2.7 (spleen) to 9.2, 9.5 and 9.6 (testes, liver and muscle, respectively) times higher concentrations than their hosts. Zn was accumulated up to 4.2 times higher in tissues of tapeworm. Cd levels were detected only in tissues of tapeworm, not in their host tissues. Pb concentrations were up to 12.9 times higher in tissues of non-parasitized than in parasitized rats. Lead from lead nitrate accumulated in higher levels than lead from Pistia stratiotes. This study confirmed the possibility of using H. diminuta as a Pb, Cd and Zn bioindicator of risk element pollution in the environment.