Total Ammonia Concentration Research Articles

The effect of feeding maize silage 1 h or 9 h before the herbage meal on dry matter intake, milk production, nitrogen partitioning and rumen function of lactating dairy cows

The study was conducted to evaluate the effect of the timing of feeding maize silage before a short herbage meal on dry matter (DM) intake, milk production, nitrogen (N) partitioning and rumen function of lactating dairy cows. Ten lactating, pregnant, Friesian × Jersey rumen-fistulated dairy cows aged 4–5 years were blocked in pairs by milksolids (MS; sum of protein and fat) production (1.73 ± 0.097 kg MS/cow.day; mean ± s.d.), bodyweight (519 ± 24.7 kg), days in milk (163 ± 12.5), and body condition score (3.9 ± 0.21). Cows within pairs were randomly allocated to one of two treatments: (1) five cows were offered one-third of their estimated total DM intake (5 kg/cow.day) as maize silage after the afternoon milking at 1500 hours, ~1 h before herbage was provided (1BH); (2) five cows were offered one-third of their estimated total DM intake as maize silage after morning milking at 0700 hours, ~9 h before herbage was provided (9BH). All cows were offered two-thirds of their total estimated DM intake (11 kg/cow.day) over a period of 4 h from 1600 hours to 2000 hours as freshly cut perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens) in an indoor system. Cows were adapted to diets for 9 days (Days 1–9), followed by 5 days of measurement (Days 10–14). Maize silage DM intake did not differ between treatments averaging 5.1 kg DM/cow.day. Herbage DM intake was greater (P = 0.02) for 9BH (11.2 kg DM/cow.day) than 1BH (10.4 kg DM/cow.day). Milk yield (P = 0.001) and MS production (P = 0.08) were greater for 9BH than 1BH (18.8 vs 15.4 kg/cow.day and 1.63 vs 1.48 kg MS/cow.day, respectively). There was no effect of time of supplementation on N partitioned to milk, faeces, or urine. The purine derivatives to creatinine ratio, as an indication of microbial protein production, was greater (P = 0.04) for 9BH than 1BH. Daily mean rumen pH and the concentration of total rumen volatile fatty acids, acetate, butyrate, and ammonia N were not affected by treatment. However, the peak concentration of ruminal ammonia N was 27% lower (P < 0.05) for 9BH than 1BH. The concentration of non-esterified fatty acid (P = 0.03) and beta-hydroxy butyric acid (P = 0.01) were greater for 1BH than 9BH (0.14 vs 0.09 and 0.81 vs 0.71 mmol/L, respectively). These results indicate that under herbage feed restriction, altering the time of supplementation relative to the herbage meal can increase herbage DM intake and subsequent milk production.

Effects of dry period management and parity on rumen fermentation, blood metabolites, and liver triacylglyceride in dairy cows

Khazanehei, H., Li, S., Khafipour, E. and Plaizier, J. C. 2015. Effects of dry period management and parity on rumen fermentation, blood metabolites, and liver triacylglyceride in dairy cows. Can. J. Anim. Sci. 95: 445–453. The effects of dry period management on rumen fermentation, blood metabolites and liver triacylglyceride (TAG) were determined in 11 second-parity (PAR 2) and 15 third-parity and older (PAR 3+) cows. Cows were paired and randomly assigned to two treatments: (1) a short 40-d dry period (SHORT) with only a close-up diet [1.43 Mcal kg–1 dry matter (DM)], or (2) a conventional 60-d dry period (CONV) with 39 d far-off diet (1.28 Mcal kg–1 DM) and 21 d close-up diet (1.43 Mcal kg–1 DM) in a randomized block design. Concentrations of total volatile fatty acids, ammonia, and lactate in rumen fluid, and also concentrations of lactate, beta hydroxybutyric acid (BHBA), urea and insulin in plasma were not affected by treatment. Across the 3 wk after calving, cows on the SHORT treatment had higher blood non-esterified fatty acid (NEFA) and glucose, and at 1 wk after calving, these cows had a higher liver TAG than cows on the CONV treatment. Also, during this time, PAR 3+ cows had higher serum NEFA compared with PAR 2 cows. Results suggest that the SHORT treatment resulted in more lipolysis, TAG accumulation in the liver and glucose sparing in early lactation compared with the CONV treatment, and that this effect was greater in PAR 3+ cows than in PAR 2 cows.

Effects of total ammonia, temperature and salinity on the mortality and viral replication of WSSV-infected Chinese shrimp (Fenneropenaeus chinensis)

In this study, we evaluated the effects of three factors, total ammonia, temperature and salinity, on the mortality of and viral proliferation in white spot syndrome virus (WSSV)-infected Chinese shrimp. Shrimp maintained in 30‰ seawater at 25°C with 0.34 mg L−1 total ammonia (control group) were injected with approximately 20 WSSV particles per shrimp and subsequently subjected to the following conditions: 30‰ seawater at 25°C, with 6 mg L−1 (N1 group) or 14 mg L−1 (N2 group) total ammonia; 30‰ seawater at 18°C (T1 group) or 30°C (T2 group), with 0.34 mg L−1 total ammonia and 20‰ (S1 group) or 40‰ (S2 group) seawater at 25°C, with 0.34 mg L−1 total ammonia. An anova analysis revealed that the cumulative mortality of WSSV-infected Chinese shrimp was significantly lower when reared in the T1 group compared to that of the T2 and control group. Similarly, the mortality of the shrimp in the S1 group was also significantly lower than that of the S2 and control group. No significant differences were detected among the N1, N2 and control groups. Accordingly, the WSSV level in the T1 and S1 groups was significantly lower than those in the control, T2 or S2 groups respectively. No significant differences in viral loads were detected among the control, N1 and N2 groups. The transfer of Chinese shrimp to lower temperature and lower salinity enhanced their resistance to WSSV infection, whereas a change in the concentration of total ammonia had no significant effect on the mortalities and viral loads of WSSV-infected shrimp.

Physiological and behavioral responses of the invasive amphipod, Dikerogammarus villosus, to ammonia

We studied the physiological and behavioral responses of the Ponto-Caspian amphipod Dikerogammarus villosus during exposure to four total ammonia concentrations (NH3+NH4+; TotAmm): 0.003 (control), 0.06, 1.6, and 7.0mmol L−1 (0.042, 0.84, 22.4, and 98.0mg L−1) for a period of up to 12h at 21°C. During the transition period from the control to treatment concentration as well as during the first hour of exposure to 0.06 and 1.6mmol L−1, gammarids increased their locomotor activity, which was manifested in significantly higher routine metabolic rates compared to control conditions. At control conditions, the resting metabolic rate amounted to 0.98±0.26mW g−1 and significantly increased by 19 and 37% at 0.06 and 1.6mmol L−1, respectively. The highest examined [TotAmm] caused a rapid and significant increase in resting metabolic rate by 37% within the first 4h of exposure before gammarids died. The exposure to elevated [TotAmm] also resulted in a significant decreased RNA:DNA ratio and significantly higher glycogen concentrations compared to the control. We conclude that even a short exposure to TotAmm of 0.06mmol L−1, which may occur in natural habitats, disturbs the physiology and behavior of D. villosus and leads to increased metabolic costs of the maintenance and reduced protein synthesis.

Global oceanic emission of ammonia: Constraints from seawater and atmospheric observations

AbstractCurrent global inventories of ammonia emissions identify the ocean as the largest natural source. This source depends on seawater pH, temperature, and the concentration of total seawater ammonia (NHx(sw)), which reflects a balance between remineralization of organic matter, uptake by plankton, and nitrification. Here we compare [NHx(sw)] from two global ocean biogeochemical models (BEC and COBALT) against extensive ocean observations. Simulated [NHx(sw)] are generally biased high. Improved simulation can be achieved in COBALT by increasing the plankton affinity for NHx within observed ranges. The resulting global ocean emissions is 2.5 TgN a−1, much lower than current literature values (7–23 TgN a−1), including the widely used Global Emissions InitiAtive (GEIA) inventory (8 TgN a−1). Such a weak ocean source implies that continental sources contribute more than half of atmospheric NHx over most of the ocean in the Northern Hemisphere. Ammonia emitted from oceanic sources is insufficient to neutralize sulfate aerosol acidity, consistent with observations. There is evidence over the Equatorial Pacific for a missing source of atmospheric ammonia that could be due to photolysis of marine organic nitrogen at the ocean surface or in the atmosphere. Accommodating this possible missing source yields a global ocean emission of ammonia in the range 2–5 TgN a−1, comparable in magnitude to other natural sources from open fires and soils.

A novel strategy achieving enrichment of metal values from and into ammoniacal solutions

A novel strategy has been proposed to achieve enrichment of metal values from and into ammoniacal solutions through solvent extraction. The extraction equilibria of Cu(II), Ni(II) and Zn(II) in ammoniacal sulfate solution have been examined with β-diketone in the pH range of 6–12. The ammonia stripping behaviors of three metal ions have been studied by consideration of total ammonia, pH and temperature. The results indicate that a special swing phenomenon was found for both extraction and ammonia stripping processes. The loaded organic phases can be successfully stripped with ammoniacal solutions by adjusting total ammonia concentration and pH. Zinc and nickel are more easily stripped than copper. Increasing temperature is beneficial for the ammonia stripping of zinc and nickel but adverse for copper, thus potentially improving the Zn/Cu and Ni/Cu separation. The ammonia stripping isotherm shows that zinc can be efficiently enriched with two counter current stages. Moreover, there is no significant loss of organic phase during stripping. Therefore, direct enrichment of metal values through ammonia stripping has a good prospect for the integrated extraction and electrowinning circuit throughout ammoniacal systems.

An electrochemical study of the dissolution of chalcopyrite in ammonia–ammonium sulphate solutions

Ammoniacal solutions are an effective lixiviant for the oxidative dissolution of some mineral sulphides. A study of the anodic dissolution of chalcopyrite in ammonium sulphate-ammonium hydroxide solutions has been carried out using cyclic voltammetry, chrono-amperometry and rest-potential measurements. The role of the copper(II)/copper(I) redox couple in the oxidation process has been evaluated. Rest potentials have been found not to be affected by oxygen but to increase with an increase in initial copper(II) concentration. This trend remains more or less unchanged with increasing total ammonia (NH3+NH4+) concentration. Cyclic voltammetry analysis shows an oxidation peak/shoulder when anodically polarising the chalcopyrite after attaining rest potential in the presence of copper(II) ions. All reverse sweep curves are more or less identical, but the Tafel slope decreases from around 150 mV/decade at 1M total ammonia concentration to around 120 mV/decade at higher ammonia concentrations. Pseudo-steady-state anodic current densities measured in the absence of copper(II) ions at the rest potentials obtained in the presence of copper(II) ions increase with increasing concentration of copper(II) ions, confirming the positive effect of copper(II) ions on the rate of dissolution of the mineral. Cyclic voltametric and chrono-amperometric data show that in the absence of initial copper(II) ions, the rate of dissolution in the presence of dissolved oxygen is significantly lower. These results confirm that the effective oxidant for the mineral under the conditions of the study is copper(II) and not dissolved oxygen. Coulometric measurements have been used to establish the stoichiometry of the anodic reaction at different potentials as involving approximately seven electrons per mole of chalcopyrite, suggesting the formation of thiosulphate, although thiosulphate ions have not been tested for or identified in solution. SEM and energy dispersive X-ray (EDX) analysis of the mineral surface left to equilibrate over time shows a copper-depleted surface, rich in iron but relatively low in sulphur. The iron in the surface layer can easily be removed by short contact with concentrated acid, which is consistent with the formation of a secondary iron-based precipitation layer rather than an altered mineral phase.

The Assessement of the Compositional and Microbiological Parameters of some Meat Products Manufactured in a Small Processing Unit

The hygienic quality of meat products can be substantially improved by respecting strictly the rules of Good Hygienic Practice (GHP) and the rules of Good Manufacturing Practice (GMP) along the entire food chain.The aim of this study was to evaluate the compositional and hygienic parameters of meat and meat products processed in a small scale processing unit, and to assess the microbial risk represented by the total plate count, E. coli and Salmonella spp. The research materials were collected from a small scale meat processing unit located in Maramures County during January-Mai 2014, 15 samples from each of the following types of products: fresh pork meat, smoked salami, cold smoked sausages, raw dry smoked specialities. In order to assess the quality of meat products, all the samples were processed through standardized protocols. Also, the results were statistically analysed using ANOVA monofactorial analysis. Some compositional parameters are accordence with the standards (salt, nitrates and total ammonia content). For the previously mentioned category of products the following compositional parameters were not in accordence with the maximum and minimum limits of the standards: proteins, fatness and humidity. The microbial load ranged between 3.56± 0.32 and 5.85 ± 0.22 log cfu/cm 2 , 20% of samples presented elevated values according with EU standards. The main nonconformities identified regarding compositional parameters in case of smoked salami were the lower values for protein content and the higher values in case of fat. Regarding the fresh sausages nonconformities they were represented mainly by the increased moisture and fat content. In case of raw meat products, the identified nonconformities were represented by the low protein and high fat and moisture content. The microbiological risk parameters were represented by total bacterial load, E. coli and Salmonella was low in all meat products except for fresh raw meat, because total bacterial load exceeds the maximum limits.

Heap and tank leaching of copper and nickel from a Platreef flotation concentrate using ammoniacal solutions

The technical feasibility of ammonia leaching of platinum group mineral (PGM)-bearing Platreef flotation concentrates was investigated as an alternative method for the recovery of base metals before precious metal recovery. The composition of the concentrate sample included 2·02% Cu and 3·17% Ni, mainly as chalcopyrite and pentlandite. A solution containing 4M NH4OH, 4M (NH4)2CO3, buffered in the pH range 9–10, was used as base case lixiviant in column and batch stirred tank reactor tests, around which the effects of total ammonia concentration and operating temperature were explored further. At optimal conditions nearly 100% Cu and Ni extraction were obtained in the batch stirred tank reactor, and 95% Cu and 60% Ni extraction was obtained in columns. The activation energy for chalcopyrite and pentlandite was 36 and 16 kJ mol− 1, respectively, in both reactors, indicating different reaction pathways for the two minerals. Gas-liquid mass transfer appears to be the limiting reaction step in columns much more than in tanks, and the degree of ammonia loss to air is significant. This initial test work indicates the feasibility of using ammonia leaching for this and similar materials as an alternative route to conventional smelting and refining before PGM recovery, but a number of technical challenges still need to be overcome.

Effect of grinding or pelleting high grain maize- or barley-based concentrates on rumen environment and microbiota of beef cattle

Eight 5-month old, rumen-cannulated Holstein male calves were used in a three months experiment to study the effect of the cereal in the concentrate (0.53 of maize, M, or 0.67 of barley, B) given either ground (GR) or pelleted to 6mm (PE) on rumen fermentation and microbiota in intensive feeding conditions. Four calves received M and the other four B, offered either GR or PE in two consecutive 45-day periods, together with straw. On days 41 and 43 of each period, the feed intake pattern was recorded and rumen contents were sampled before the morning feeding (0h) and after 4 and 8h to determine rumen pH and total volatile fatty acids (VFA), lactic acid, ammonia and fatty acids (FA) concentration, and to characterise bacterial and protozoal populations. Compared with those given M, calves fed B showed lower rumen pH (5.64 vs. 6.14, P=0.001) and higher total VFA concentration (140mmol/l vs. 113mmol/l, P=0.014) 4h after feeding, and a greater proportion of records of pH below 5.6 (0.27 vs. 0.10, P=0.039) and VFA over 150mmol/l (0.18 vs. 0.02, P=0.019), benchmarks of subacute ruminal acidosis (SARA). Feeding B resulted in lower (P=0.072) and higher (P=0.059) proportions of acetic and propionic acids, respectively, with sampling time differences for this diet, as well as more variable ammonia concentrations (P<0.001). On the other hand, concentrates processed as PE promoted a lower acetic to propionic ratio, this effect being more evident with M (1.15 vs. 2.39, P=0.003), and a more pronounced pH drop from 0 to 4h after feeding compared with those given GR (1.01 vs. 0.87 pH units, P=0.059). Only minor effects were observed on either FA concentrations or rumen microbiota. The more abrupt rumen fermentation induced by B may be due to the more rapidly degradation rate of its starch combined with a greater concentrate intake during the first 4h (2.83 vs. 2.43kg dry matter, P=0.031), which was not affected by the concentrate processing. The results suggest that barley-based diets would cause a less favourable rumen fermentation that might increase the risk of SARA compared with maize diets, whereas pelleting the concentrates at 6mm would not affect the feed intake pattern and would not be advisable to avoid SARA compared with grinding

Ammonia and temperature determine potential clustering in the anaerobic digestion microbiome

Anaerobic digestion is regarded as a key environmental technology in the present and future bio-based economy. The microbial community completing the anaerobic digestion process is considered complex, and several attempts already have been carried out to determine the key microbial populations. However, the key differences in the anaerobic digestion microbiomes, and the environmental/process parameters that drive these differences, remain poorly understood. In this research, we hypothesized that differences in operational parameters lead to a particular composition and organization of microbial communities in full-scale installations. A total of 38 samples were collected from 29 different full-scale anaerobic digestion installations, showing constant biogas production in function of time. Microbial community analysis was carried out by means of amplicon sequencing and real-time PCR. The bacterial community in all samples was dominated by representatives of the Firmicutes, Bacteroidetes and Proteobacteria, covering 86.1 ± 10.7% of the total bacterial community. Acetoclastic methanogenesis was dominated by Methanosaetaceae, yet, only the hydrogenotrophic Methanobacteriales correlated with biogas production, confirming their importance in high-rate anaerobic digestion systems. In-depth analysis of operational and environmental parameters and bacterial community structure indicated the presence of three potential clusters in anaerobic digestion. These clusters were determined by total ammonia concentration, free ammonia concentration and temperature, and characterized by an increased relative abundance of Bacteroidales, Clostridiales and Lactobacillales, respectively. None of the methanogenic populations, however, could be significantly attributed to any of the three clusters. Nonetheless, further experimental research will be required to validate the existence of these different clusters, and to which extent the presence of these clusters relates to stable or sub-optimal anaerobic digestion.

Reversible brain swelling in crucian carp (Carassius carassius) and goldfish (Carassius auratus) in response to high external ammonia and anoxia

Increased internal ammonia (hyperammonemia) and ischemic/anoxic insults are known to result in a cascade of deleterious events that can culminate in potentially fatal brain swelling in mammals. It is less clear, however, if the brains of fishes respond to ammonia in a similar manner. The present study demonstrated that the crucian carp (Carassius carassius) was not only able to endure high environmental ammonia exposure (HEA; 2 to 22mmolL−1) but that they experienced 30% increases in brain water content at the highest ammonia concentrations. This swelling was accompanied by 4-fold increases in plasma total ammonia (TAmm) concentration, but both plasma TAmm and brain water content were restored to pre-exposure levels following depuration in ammonia-free water. The closely related, ammonia-tolerant goldfish (Carassius auratus) responded similarly to HEA (up to 3.6mmolL−1), which was accompanied by 4-fold increases in brain glutamine. Subsequent administration of the glutamine synthetase inhibitor, methionine sulfoximine (MSO), reduced brain glutamine accumulation by 80% during HEA. However, MSO failed to prevent ammonia-induced increases in brain water content suggesting that glutamine may not be directly involved in initiating ammonia-induced brain swelling in fishes. Although the mechanisms of brain swelling are likely different, exposure to anoxia for 96h caused similar, but lesser (10%) increases in brain water content in crucian carp. We conclude that brain swelling in some fishes may be a common response to increased internal ammonia or lower oxygen but further research is needed to deduce the underlying mechanisms behind such responses.

Impacts of ultrasound on leaching recovery of zinc from low grade zinc oxide ore

AbstractOn the basis of an experiment on ultrasonic enhanced ammonia leaching of low grade zinc oxide ores, the effects of the total ammonia concentration, the ratio between the NH

Adaptations of a deep sea scavenger: High ammonia tolerance and active NH4+ excretion by the Pacific hagfish (Eptatretus stoutii)

The Pacific hagfish (Eptatretus stoutii) has an exceptional ability to both withstand and recover from exposure to high external ammonia (HEA). This tolerance is likely due to the feeding behavior of this scavenger, which feeds on intermittent food falls of carrion (e.g. fish, large marine mammals) during which time it may be exposed to high concentrations of total ammonia (TAmm=NH3+NH4+) while burrowed inside the decomposing carcass. Here we exposed hagfish to 20mmolL−1TAmm for periods of up to 48h and then let animals recover in ammonia-free seawater. During the 48h HEA exposure period, plasma TAmm increased 100-fold to over 5000μmolL−1 while ammonia excretion (Jamm) was transiently inhibited. This increase in plasma TAmm resulted from NH3 influx down massive inwardly directed ΔPNH3 gradients, which also led to a short-lived metabolic alkalosis. Plasma [TAmm] stabilized after 24–48h, possibly through a reduction in NH3 permeability across the body surface, which lowered NH3 influx. Ammonia balance was subsequently maintained through the re-establishment of Jamm against an inwardly directed ΔPNH3. Calculations of the Nernst potential for ammonia strongly indicated that Jamm was also taking place against a large inwardly directed NH4+ electrochemical gradient. Recovery from HEA in ammonia-free water was characterized by a large ammonia washout, and the restoration of plasma TAmm concentrations to near control concentrations. Ammonia clearance was also accompanied by a residual metabolic acidosis, which likely offset the ammonia-induced metabolic alkalosis seen in the early stages of HEA exposure. We conclude that restoration of Jamm by the Pacific hagfish during ammonia exposure likely involves secondary active transport of NH4+, possibly mediated by Na+/NH4+ (H+) exchange.

Recent trends in gas-phase ammonia and PM2.5 ammonium in the Southeast United States

Ammonia measurements from the Southeastern Aerosol Research and Characterization (SEARCH) study network were analyzed for trends over 9 yr (2004–2012) of observations. Total ammonia concentrations, defined as the sum of gas-phase ammonia and fine particle ammonium, were found to be decreasing by 1–4% yr−1 and were qualitatively consistent with ammonia emission estimates for the SEARCH states of Alabama, Georgia, Mississippi, and Florida. On the other hand, gas-phase ammonia mixing ratios were found to be slightly rising or steady over the region, leading to the observation that the gas-phase fraction of total ammonia has steadily increased over 2004–2012 as a result of declining emissions of the strong acid precursor species sulfur dioxide (SO2) and nitrogen oxides (NOx) and consequent reduced partitioning of ammonia to the fine particle phase. Because gas-phase ammonia is removed from the atmosphere more rapidly than fine particle ammonium, an increase in the gas-phase fraction of total ammonia may result in shifted deposition patterns as more ammonia is deposited closer to sources rather than transported downwind in fine particles. Additional long-term measurements and modeling studies are needed to determine if similar transitions of total ammonia to the gas phase are occurring outside of the Southeast and to assess if these changes are impacting plants and ecosystems near major ammonia sources. Unusually high ammonia concentrations observed in 2007 in the SEARCH measurements are hypothesized to be linked to emissions from wildfires that were much more prevalent across the Southeast during that year due to elevated temperatures and widespread drought. Although wildfires are currently estimated to be a relatively small fraction (3–10%) of total ammonia emissions in the Southeast, the projected increased incidence of wildfires in this region as a result of global climate change may lead to this source’s increased importance over the rest of the 21st century.Implications: Ammonia concentrations from the Southeastern Aerosol Research and Characterization study (SEARCH) network are analyzed over the 9-yr period 2004–2012. Total ammonia (gaseous ammonia + PM2.5 ammonium) concentrations declined at a rate of 1–4% yr−1, consistent with U.S. Environmental Protection Agency (EPA) emission estimates for the Southeast United States, but the fraction of ammonia in the gas phase has risen steadily (+1–3% yr−1) over the time period. Declining emissions of SO2 and NOx resulting from imposed air quality regulations have resulted in decreased atmospheric strong acids and less ammonia partitioning to the particle phase, which may impact the amount and overall pattern of ammonia deposition.

Does ammonia trigger hyperventilation in the elasmobranch, Squalus acanthias suckleyi?

We examined the ventilatory response of the spiny dogfish, to elevated internal or environmental ammonia. Sharks were injected via arterial catheters with ammonia solutions or their Na salt equivalents sufficient to increase plasma total ammonia concentration [TAmm]a by 3–5 fold from 145±21μM to 447±150μM using NH4HCO3 and a maximum of 766±100μM using (NH4)2SO4. (NH4)2SO4 caused a small increase in ventilation frequency (+14%) and a large increase in amplitude (+69%), while Na2SO4 did not. However, CO2 partial pressure (PaCO2) also increased and arterial pHa and plasma bicarbonate concentration ([HCO3−]a) decreased. NH4HCO3 caused a smaller increase in plasma ammonia resulting in a smaller but significant, short lived increases in ventilation frequency (+6%) and amplitude (36%), together with a rise in PaCO2 and [HCO3−]a. Injection with NaHCO3 which increased pHa and [HCO3−]a did not change ventilation. Plasma ammonia concentration correlated significantly with ventilation amplitude, while ventilation frequency showed a (negative) correlation with pHa. Exposure to high environmental ammonia (1500μM NH4HCO3) did not induce changes in ventilation until plasma [TAmm]a increased and ventilation amplitude (but not frequency) increased in parallel. We conclude that internal ammonia stimulates ventilation in spiny dogfish, especially amplitude or stroke volume, while environmental ammonia only stimulates ventilation after ammonia diffuses into the bloodstream.

Influence of substrate concentration and feed frequency on ammonia inhibition in microbial fuel cells

Excessive amounts of ammonia are known to inhibit exoelectrogenic activities in microbial fuel cells (MFCs). However, the threshold ammonia concentration that triggers toxic effects is not consistent among literature papers, indicating that ammonia inhibition can be affected by other operational factors. Here, we examined the effect of substrate concentration and feed frequency on the capacity of exoelectrogenic bacteria to resist against ammonia inhibition. The high substrate condition (2 g L−1 sodium acetate, 2-day feed) maintained high electricity generation (between 1.1 and 1.9 W m−2) for total ammonia concentration up to 4000 mg-N L−1. The less frequent feed condition (2 g L−1 sodium acetate, 6-day feed) and the low substrate condition (0.67 g L−1 sodium acetate, 2-day feed) resulted in substantial decreases in electricity generation at total ammonia concentration of 2500 and 3000 mg-N L−1, respectively. It was determined that the power density curve serves as a better indicator than continuously monitored electric current for predicting ammonia inhibition in MFCs. The chemical oxygen demand (COD) removal gradually decreased at high ammonia concentration even without ammonia inhibition in electricity generation. The experimental results demonstrated that high substrate concentration and frequent feed substantially enhance the capacity of exoelectrogenic bacteria to resist against ammonia inhibition.

Nonprotein Nitrogenous Compounds and Gelling Property of Whitecheek Shark (C archarhinus Dussumieri ) Mince as Affected by Washing and Microbial Transglutaminase

Changes in nonprotein nitrogenous compounds and gelling properties of whitecheek shark (Carcharhinus dussumieri) meat during iced storage for 12 days were monitored. Total volatile base (TVB), trimethylamine (TMA) and ammonia contents increased, whereas urea content decreased during the storage (P < 0.05). TVB, TMA, urea and ammonia contents were lower in washed mince, indicating the removal of those compounds by washing. The addition of microbial transglutaminase (MTGase, 0.6 unit/g sample) was able to increase breaking force, deformation and water-holding capacity of both gels from mince and washed mince. Nevertheless, gel strengthening effect of MTGase was lowered when mince or washed mince were obtained from shark stored for an extended time. Polymerization of myosin heavy chain was enhanced when MTGase was incorporated but took place at a lower degree for mince and washed mince produced from unfresh shark. Washing process in combination with MTGase addition could therefore improve gel quality of shark meat. Practical Applications Shark meat is a good source of protein, which could be a suitable source for surimi production. However, the meat is considered to have a low market value because of undesirable odor, which is mainly from the decomposition of urea to ammonia during extended storage. Appropriate washing to remove those compounds, along with the use of microbial transglutaminase (MTGase), can be a promising means to improve the textural properties of gels from shark mince. Thus, shark meat can be better exploited, especially for the surimi industry.

Application of a partial nitritation and anammox system for the old landfill leachate treatment

This study shows high nitrogen removal efficiency of a combination of partial nitritation and Anaerobic Ammonium Oxidation (anammox) process for old landfill leachate treatment. A lab-scale experiment including partial nitritation using a sequencing batch reactor (PN-SBR) followed by a anammox hybrid reactor (HAR), which consists of suspended biomass layer in the bottom part and bio-carrier bed in the upper part run at the influent total ammonia concentrations (TAN) of 500 mg N/L and 1000 mg N/L. The result of PN-SBR experiment showed that the NO2–N:NH4–N ratio achieved about 1.22 and 1.02 at HRT of 12 h (influent TAN of 500 mg N/L) and HRT of 19 h (influent TAN of 1000 mg N/L), respectively. Simultaneously, the HAR was operated at the nitrogen loading rate (NLR) of 4.2 and 8.3 kg N/m3.d, corresponding to influent TAN of 500 mg N/L and 1000 mg N/L, respectively. The effluent of the system containing 9.7 ± 3.5 mg NH4–N/L, 1.7 ± 0.4 mg NO2–N/L and 23 ± 4 mg NO3–N/L (equivalent to 35 ± 4 mg TN/L) at NLR of 1.02 for PN-SBR and NLR of 4.2 kg N/m3.d for HAR. This effluent quality was good enough to meet Vietnamese treated landfill leachate quality. The system obtained TN removals of 93 ± 1% and 81 ± 1.2% at NLRs of 4.2 kg TN/m3.d (phase I) and 8.3 kg TN/m3.d (phase II), respectively. The total biomass of HAR including attached biomass and suspended one was maintained up to 20,400 mgVSS/L at the end of the experiment when the removal rate of anamnox biomass obtained 0.4 kg TN/kgVSS.d. While, PN-SBR was kept at 2300 mg MLVSS/L and SRT of 10–12 days at NLR of 4.2 kg TN/m3.d, which the nitrogen conversion rate of AOB was 0.53 kg TAN/kgVSS.d. In terms of COD removal, it is found that PN-SBR removed only 14% of influent COD, whereas HAR removed 30% of COD.

Dietary vitamin C mitigates monocrotophos toxicity in the freshwater fishClarias batrachus

The amelioration effect of balanced diet with supplementation of vitamin C against stress was evaluated in freshwater paddy field fish, Clarias batrachus, exposed to organophosphate insecticide, monocrotophos (MCP). Three groups of fishes, that is, (E0) Control, (E1) MCP (2.14 mg L−1) exposure and E2) Vitamin C, MCP (0.2 g kg−1 body weight + 2.144 mg L−1) were selected for the sublethal study. The effect of MCP on protein metabolism in physiological sensitive tissues, namely gills, kidney, liver and muscle of the fish has been determined. Stress on Clarias batrachus was evident that the total protein, amino acid and ammonia contents were decreased, and urea and glutamine levels were elevated in all tissues for 30 days. Similarly, the activities of protease, aminotransferases and phosphatases were elevated significantly in all the tissues during the same period. Fish fed with a diet supplemented by vitamin C (0.2 g kg−1 body weight) could significantly counter these effects.