Nitrogen Concentration Levels Research Articles

Microbial fuel cell application in landfill leachate treatment

The feasibility of using microbial fuel cells (MFCs) in landfill leachate treatment and electricity production was assessed under high levels of nitrogen concentration (6033 mg N L −1) and conductivity (73,588 μS cm −1). An air-cathode MFC was used over a period of 155 days to treat urban landfill leachate. Up to 8.5 kg COD m −3 d −1 of biodegradable organic matter was removed at the same time as electricity (344 mW m −3) was produced. Nitrogen compounds suffered transformations in the MFC. Ammonium was oxidized to nitrite using oxygen diffused from the membrane. However, at high free ammonia concentrations (around 900 mg N-NH 3 L −1), the activity of nitrifier microorganisms was inhibited. Ammonium reduction was also resulted from ammonium transfer through the membrane or from ammonia loss. High salinity content benefited the MFC performance increasing power production and decreasing the internal resistance.

Evaluating the performance of PC-ANN for the estimation of rice nitrogen concentration from canopy hyperspectral reflectance

In this study, a wide range of leaf nitrogen concentration levels was established in field-grown rice with the application of three fertilizer levels. Hyperspectral reflectance data of the rice canopy through rice whole growth stages were acquired over the 350 nm to 2500 nm range. Comparisons of prediction power of two statistical methods (linear regression technique (LR) and artificial neural network (ANN)), for rice N estimation (nitrogen concentration, mg nitrogen g−1 leaf dry weight) were performed using two different input variables (nitrogen sensitive hyperspectral reflectance and principal component scores). The results indicted very good agreement between the observed and the predicted N with all model methods, which was especially true for the PC-ANN model (artificial neural network based on principal component scores), with an RMSE = 0.347 and REP = 13.14%. Compared to the LR algorithm, the ANN increased accuracy by lowering the RMSE by 17.6% and 25.8% for models based on spectral reflectance and PCs, respectively.

Dependences of nitrogen incorporation behaviors on the crystallinity and phase distribution of atomic layer deposited Hf-silicate films with various Si concentrations

This study examined the nitrogen incorporation behavior of atomic layer deposited HfO2 and Hf-silicate films with various Si concentrations during thermal annealing under a NH3 atmosphere. The level of crystallization and the phase distribution of the films (crystalline HfO2 and amorphous Hf-silicate and SiO2) had a significant effect on extent of nitrogen incorporation. There was virtually no nitrogen incorporation in the crystallized HfO2. Under the condition that the Hf-silicate films were not phase-separated and crystallized during thermal nitridation, the excess HfO2 and SiO2 phases that did not contribute to the amorphous HfSiO4 phase were easily nitrided. On the other hand, the amorphous HfSiO4 phase was barely nitrided. Therefore, it was concluded that the level of nitrogen concentration in the Hf-silicate films decreased with increasing Si concentration in the films. The changes in the capacitance equivalent thickness, gate leakage current density, and flatband voltage shift of the various films after thermal nitridation were consistent with the nitrogen concentration in the films.

Trickle and sprinkler irrigation of potato ( Solanum tuberosum L.) in the Middle Anatolian Region in Turkey

The potato ( Solanum tuberosum L.) is widely planted in the Middle Anatolian Region, especially in the Nigde-Nevsehir district where 25% of the total potato growing area is located and produces 44% of the total yield. In recent years, the farmers in the Nigde-Nevsehir district have been applying high amounts of nitrogen (N) fertilizers (sometimes more than 900 kg N ha −1) and frequent irrigation at high rates in order to get a much higher yield. This situation results in increased irrigation and fertilization costs as well as polluted ground water resources and soil. Thus, it is critical to know the water and nitrogen requirements of the crop, as well as how to improve irrigation efficiency. Field experiments were conducted in the Nigde-Nevsehir (arid) region on a Fluvents ( Entisols) soil to determine water and nitrogen requirements of potato crops under sprinkler and trickle irrigation methods. Irrigation treatments were based on Class A pan evaporation and nitrogen levels were formed with different nitrogen concentrations. The highest yield, averaging 47,505 kg ha −1, was measured in sprinkler-irrigated plots at the 60 g m −3 nitrogen concentration level in the irrigation treatment with limited irrigation (480 mm). Statistically higher tuber yields were obtained at the 45 and 60 g m −3 nitrogen concentration levels in irrigation treatments with full and limited irrigation. Maximum yields were obtained with about 17% less water in the sprinkler method as compared to the trickle method (not statistically significant). On the loam and sandy loam soils, tuber yields were reduced by deficit irrigation corresponding to 70% and 74% of evapotranspiration in sprinkler and trickle irrigations, respectively. Water use of the potato crop ranged from 490 to 760 mm for sprinkler-irrigated plots and 565–830 mm for trickle-irrigated treatments. The highest water use efficiency (WUE) levels of 7.37 and 4.79 kg m −3 were obtained in sprinkle and trickle irrigated plots, respectively. There were inverse effects of irrigation and nitrogen levels on the WUE of the potato crops. Significant linear relationships were found between tuber yield and water use for both irrigation methods. Yield response factors were calculated at 1.05 for sprinkler methods and 0.68 for trickle methods. There were statistically significant linear and polynomial relationships between tuber yield and nitrogen amounts used in trickle and sprinkler-irrigated treatments, respectively. In sprinkler-irrigated treatments, the maximum tuber yield was obtained with 199 kg N ha −1. The tuber cumulative nitrogen use efficiency (NUE cu) and incremental nitrogen use efficiency (NUE in) were affected quite differently by water, nitrogen levels and years. NUE cu varied from 16 to 472 g kg −1 and NUE in varied from 75 to 1035 g kg −1 depending on the irrigation method. In both years, the NH 4-N concentrations were lower than NO 3-N, and thus the removed nitrogen and nitrogen losses were found to be 19–87 kg ha −1 for sprinkler methods and 25–89 kg ha −1 for trickle methods. Nitrogen losses in sprinkler methods reached 76%, which were higher than losses in trickle methods.

Drainage basin security of hazardous chemical fluxe in the Yodo River basin

The Yodo River basin consists of three major tributary basins (and other small river basins) namely Uji, Katsura and Kizu, which overlap respectively Shiga, Kvoto and Nara prefectures' administrative areas. Lake Biwa, the largest lake in Japan, drains water through the Uji river. The water quality of the lake, in terms of BOD, continuously improved over the last decade. However, the quality in terms of COD did not show any improvement in spite of a large amount of infrastructure finance being introduced. Eutrophication of the lake still continues, showing no improvement in the nitrogen concentration level. Non-point as well as point source control is not strong enough. There is a gap between BOD and COD evaluations of the lake water quality. Hazardous chemical fluxes are estimated based upon PRTR reports of Japan (2001). PCBs are still discharged into the lake, although the report of Shiga Prefecture showed zero discharge. Dace fish monitoring clearly showed that PCB contamination of the fish had not changed since the 1980s in spite of a ban on use and production of PCBs in the 1970s. There is still leakage of PCBs into the lake. The major exposure of dioxins to Japanese is fish rather than meat and eggs. The risk of water contamination must take into consideration not only drinking water safety but also ecological magnification of food chains in water. The ecological health aspect of hazardous chemicals is also important, such as organotins with imposex of sea snails. Finally, public participation in hazardous chemical management is very important using the method of risk communication based upon the annual report of PRTR in Japan.

Magneto-optics on p-type ZnSe epilayers: the dependence on the nitrogen doping concentration

Photoluminescence (PL) experiments under high magnetic fields in the Faraday configuration on nitrogen-doped ZnSe epilayer structures grown by molecular beam epitaxy are applied to study the impurity centers in the compensation limit. Following the nitrogen concentration level [ N], different regimes of field dependence of the donor–acceptor pair transitions are reported. The wave function shrinkage model gives the mean distance 〈 R〉 between impurity centers as the critical parameter for this feature. The transitions related to excitons bound to shallow ( I 1) and deep acceptors I 1 p are also discussed. Their field-dependences are observed to be directly connected to the nitrogen doping density, and imply different capture rates depending on the nature of the neutral impurity.

Stickstoff-Immissionen als neuer Standortsfaktor in Waldgesellschaften - neue Entwicklungen am Beispiel südwestdeutscher Wälder

Investigations into the rate of atmospheric nitrogen deposition, of nitrogen recycling by litter and of nitrogen concentration levels in seepage water under different coniferous and broad-leaved tree stands in South-West Germany prove that the nitrogen status (e.g. input, turnover, balance) of the studied ecosystems is quite different from each other. The evident differences, presumably caused to a great deal by recent increase in deposition rates, is expressed by indicator species of ground vegetation only with delay and at a restricted scale. The species involved are correlated with more persistent site factors (e.g. soil reaction, buffer state, humus type), that do change only in a longer term. Species will show adapted reactions as their physiological reaction pattern is much greater than the ecological range in which they are normally present in actual forest vegetation types

Responses to Simulated Leaf and Root Herbivory by A Biennial, Tragopogon Dubius

Removal of 25 or 75% of leaf or root tissue, and 25% of both, was used to simulate above— and belowground herbivory on Tragopogon dubius. Plants with 25% of their leaf tissue removed did not differ significantly from controls in total biomass; those with any root tissue trimmed produced significantly less biomass while the 75% leaf removal treatment was intermediate. A similar pattern was exhibited for plant mortality and flower production. Plants that had one or more flowers removed by herbivores grew significantly larger and produced significantly more flowers than plants that lost no flowers, regardless of treatment. The greatest differences between treatments in nutrients allocation patterns occurred 1 d after manipulations were applied. Subsequently, differences between treatments moderated, and values tended to converge by 98 d postmanipulation, when the plants were harvested. Seeds had significantly higher nitrogen concentration levels than leaf or root tissue.

Nutritional Quality and Chemical Defence in the Ragwort-Cinnabar Moth Interaction

(1) Many studies suggest selection by insects for protein-rich foodplants and, in the cinnabar moth, also for alkaloid-rich foodplants. (2) Larvae reared on foodplants with different protein concentrations did not produce heavier pupae at the highest concentrations. (3) Nearest-neighbour analysis demonstrated absence of selection for high alkaloid concentrations. (4) Protein-nitrogen and alkaloid concentrations are positively correlated in the foodplant. (5) We suggest that ragwort-plants low in protein-nitrogen are nutritionally inadequate whereas plants with high protein are toxic because of the correlation between protein-nitrogen and alkaloid. (6) Nearest-neighbour analysis of oviposition in relation to the quality of foodplant populations and individuals confirmed an optimum response at an intermediate level of nitrogen concentration.

Forest-floor nitrogen dynamics in a 60-year-old paper birch ecosystem in interior Alaska

An analysis was conducted of nitrogen dynamics in the forest floor of a paper birch forest in subarctic Alaska. Low addition levels of high enrichment isotope (<1% of the total nitrogen pool with 95 to 99 atom percent excess15N) and isotope dilution analysis, were used to establish the kinetics of nitrogen flow. The pools examined were NH4, NO3+NO2, soluble organic-N and forest floor organic matter. This approach allows a more realistic assessment of rates of N movement at the levels of nitrogen concentration encountered in natural systems.

砂栽培に関する基礎的研究 (第3報)

It is generally accepted that the population of subterranean micro-organisms having a direct concern with the nitrogen metabolism of plants grown in the sand is rather scarce as compared with those in ordinary farm soil, and the ammonification as well as the nitrification processes in sand, in consequence, has been considered to be generally small. For raising of plants in sand, therefore, it is quite necessary to make clear the nitrification processes which take place in the sand, and also to get more advanced knowledge concerning the fertilizing method of nitrogen in the Suna Saibai (a type of sand culture). In this connection, the author carried out studies on the nitrogen metabolism in the Suna Saibai, e.g., the influence of water content in the sand, of the concentration of nitrogen in the sand, and the effect of applying clay (bentonite) to the sand under 30°C constant temperature condition.1. The ammonification and the nitrification in the sand took place quite sufficieutly. The nitrification of urea was detected 4 days after application.2. The effect of the water content of the sand upon the ammonification was relatively small, and when the concentration of applied nitrogen was 125 or 333ppm, the ammonification at the 4th day attained ca. 65 to 85% of total nitrogen.3. When the concentration of applied nitrogen was 125ppm, the nitrification was not influenced at all by the water content of the medium. The rate of nitrification per the total nitrogen attained ca. 95 to 100% at the 20th day. When it was 333 ppm the effect of the water content became detectable only after 12 days. The nitrification occurred earliest in the plot with a water content of 30ml per 150g of the sand, next in the plot of 20ml, and finally those of both 10 and 40ml. Namely, in the plots of 10, 20, 30 and 40ml water content, the nitrification attained to 35, 60, 70 or 40% on the 12th day and 60, 90, 95 or 60% of total nitrogen, respectively on the 20th day.4. When the water content was the most favorable (30ml of water per 150g of sand, i.e., ca. 60% of the maximum water holding capacity), the ammonification and the nitrification were remarkably influenced by the concentration of applied nitrogen, and the higher the concentration, the later these occurred. The rates of ammonification at each level of nitrogen concentration (125, 250, 500 and 1, 000ppm) were 80, 65, 50 and 35% on the 4th day, and the nitrification on the 16th day was 100, 95, 70 and 50% respectively.5. The added bentonite was refinitely effective in each of three different kinds of nitrogen levels, (250, 500 and 1, 000ppm), inducing good effect on the ammonification and the nitrification. In the case of 250ppm of nitrogen and 30ml water per 150g of sand, the effect of supplying bentonite at four different levels (0, 0.5, 1.5 and 4.5g) could be noticed on the 12th day after application when the population of soil organisms was considered to become sufficiently large. The nitrification rates on the 16th day were 45, 80 and 100%, respective to the increased application of bentonite upon pH was as follows: When 4.5g was added, pH was 7.2 at about 60% nitrification (on the 16th day). On the other hand, when the bentonite was not added at all, the pH value remained very low, being 4.6 at about 45% nitrification (on the 16th day). Thus the effect upon the ammonification, the nitrification and upon pH caused by the addition of bentonite was quite evident.