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BACKGROUND: The distribution of nitrogen isotopes has important significance in paleoclimate, paleosedimentary and evolutionary characteristics. Nitrogen is one of the important heteroatomic elements in crude oil. The nitrogen content of crude oil is generally 0.1% to 2%, mainly in the non-hydrocarbon and asphaltene fractions, and can be divided into basic and non-basic nitrogenous fractions according to polarity. Due to the high carbon/nitrogen ratio of crude oils, accurate nitrogen isotope analysis results cannot be obtained from direct testing for most crude oils. As a result, the research on nitrogen isotopes in crude oil has been developed slowly, and the available data are few, while not being well applied in practice. OBJECTIVES: To determine the nitrogen isotopic distribution characteristics of different nitrogen-containing components in crude oil, and to address the problem of low nitrogen content in crude oil, which makes the direct determination of nitrogen isotopes less stable and reproducible. METHODS: A two-stage separation pre-treatment method was utilized to successively separate the nonhydrocarbon and asphaltene fractions of crude oil, and the basic and neutral nitrogen fractions were separated from the non-hydrocarbon fraction. The characteristics of nitrogen isotope distribution in different nitrogenous components of crude oil were determined by the Dumas combustion method. Multiple stable nitrogen isotope standards (USGS61, USGS62, USGS63) were selected for quality control of nitrogen isotope results. RESULTS: The nitrogen isotope data obtained by this method for each component of crude oil were of good quality, with the uncertainties less than ±0.4‰. By separating and measuring crude oil samples from marine and continental sedimentary environments, the results showed that the nitrogen isotope of crude oil samples in continental sedimentary environment was heavier than that in a marine sedimentary environment. The distribution of nitrogen isotopes of asphaltene fractions was heavier than that of non-hydrocarbon fractions. The distribution characteristics of the nitrogen isotopes of the different polar nitrogen-containing compounds also differed significantly. CONCLUSIONS: The technical dilemma that crude oil samples cannot accurately produce stable nitrogen isotopes due to the disparity in carbon to nitrogen ratios is solved and technical support for the practical application of a crude oil nitrogen isotope index is also obtained. [ABSTRACT FROM AUTHOR]

In order to explore the effect of hydraulic retention time (HRT) on the treatment effect of constructed wetland, the anaerobic tank surface flow constructed wetland (AT-SFCW) system was used to treat the tail water of sewage plant. The removal rules of CODcr, NH4+N, NO3- -N and TP pollutants in the system were discussed by investigating the effect of HRT change on the removal effect of pollutants. The results show that the removal efficiency of CODcr, NH4+N, NO3- -N and TP in AT-SFCW system increases first and then decreases with the extension of HRT. The optimal HRT of the system is 5 d, and the highest removal efficiency of each pollutant is 83.68%,86. 22%,88.99% and 69.87% respectively. When HRT =5 d, the concentration change of each pollutant shows that the pollutants are significantly reduced along each treatment unit, and most of CODcr and NO3- -N are removed in the anaerobic tank, which are reduced to 18. 19 mg/L and 0.29 mg/L respectively; The removal of NH-N and TP mainly occurred in the surface flow wetland, decreasing to 1.50 mg/L and 0.55 mg/L respectively. This study provides a theoretical basis for the selection of the best HRT for the combined constructed wetland. The quantitative analysis of nitrogen and phosphorus removal pathways has important guiding significance for the in-depth understanding of the law of nitrogen removal in the constructed wetland and the improvement of the removal rate of nitrogen and phosphorus. [ABSTRACT FROM AUTHOR]

To study the responses on addition of nitrogen to photosynthetic characteristics in Pinus massoniana seedlings under different phosphorus conditions and nitrogen addition×phosphorus condition interaction, two-year-old Pinus massoniana seedlings were used as study material.Two soil phosphorus conditions[including no additional phosphorous(8.18 mg·kg-1,P0) and phosphorus addition(80 mg·kg-1,P1)],three nitrogen addition levels[i.e.,no nitrogen addition(0 kg·hm-2·a-1,N0),low nitrogen addition(30 kg·hm-2·a-1,N1)and high nitrogen addition(60 kg·hm-2·a-1,N2)] were set up in May 2021,the variation in gas exchange parameters, chlorophyll content, RuBisCO activity, and leaf nitrogen and phosphorus content in each treatment were observed at the end of July and the end of October.The results showed: nitrogen addition significantly increased net photosynthetic rate (Pn) and transpiration rate (Tr). In the early stage of the experiment (the end of July), it significantly increased stomatal conductance (Gs) and intercellular CO2concentration (Ci), and inhibited the Gs of P1 in the later stages (the end of October). In the early stages of the experiment, the addition of nitrogen and phosphorus significantly increased the content of chlorophyll b, N1 significantly increased the total chlorophyll content and RuBisCO enzyme activity, P1 significantly reduced the RuBisCO activity under N0 and N2 treatment, and nitrogen application in P1 significantly increased the content of phosphorus in leaves.In the later stages, nitrogen addition significantly increased the content of nitrogen, phosphorus, and total chlorophyll, promoting the synthesis of chlorophyll b under the P0 condition.The activity of RuBisCO increased with the addition of nitrogen and phosphorus.Correlation analysis showed that Pn of Pinus massoniana was significantly positively correlated with gas exchange parameters and total chlorophyll content.In conclusion, nitrogen addition significantly affects the net photosynthetic rate of Pinus massoniana seedlings in the short term without influencing the soil phosphorus condition.Nitrogen application can increase the content of nitrogen and phosphorus in leaves, thereby promoting the synthesis of total chlorophyll, and affect the photosynthetic rate of Pinus massoniana seedlings by regulating the stomata by promoting stomatal expansion, and increasing transpiration to enhance photosynthetic capacity. [ABSTRACT FROM AUTHOR]

【Objective】Analysis of nitrogen fertilizer efficiency and yield of six high-quality conventional rice varieties at different nitrogen applications was conducted. It provides theoretical basis for the production selection of nitrogen-efficient varieties of high-quality rice and reasonable reduction of nitrogen fertilizer application.【Method】The test varieties are Guixiang 18,Guiyu 12,Guiyu 9,Guiyu 11,Guiyu 18 and Guiyu 8.The control variety is Liushayouzhan 202. Set four nitrogen fertilizer application levels:0（no nitrogen）,112.5（low-medium nitrogen）,150（conventional nitrogen） and 187.5（high nitrogen） kg/hm2(The treatment sequences are N0,N7.5,N10.0 and N12.5).Determination and analysis on the nitrogen utilization of each varieties by measuring physiological efficiency（PE）,agronomic efficiency（AE）,recovery efficiency（RE）,partial factor productivity（PFP）, and yield difference was compared and nitrogen efficiency was evaluated.【Result】The physiological efficiency and agronomic efficiency of nitrogen fertilizer of six high quality conventional rice varieties were the highest under N7.5 and all of them were significantly higher than N12.5（P<0.05,the same as below）.There was no significant difference in the recovery efficiency of nitrogen fertilizer of Guiyu 12,Guiyu 11,and Guiyu 18 among various nitrogen applications（P>0.05,the same as below）.The recovery efficiency of nitrogen fertilizer of Guixiang 18,Guiyu 9 and Guiyu8 were the highest at N10.0,N7.5 and N12.5.The partial factor productivity of nitrogen fertilizer of tested varieties decreased significantly with the increase of nitrogen application. There was no significant difference in yield at N7.5,N10.0 and N12.5 of Guixiang 18,Guiyu 12,Guiyu 9 and Guiyu 11. The yield of Guiyu 18 and Guiyu 8 were significantly higher than that when N7.5 compared to N12.5.The yield of six high-quality conventional rice varieties at N7.5 were significantly higher than that of CK.It is higher than that of CK under treatment of N10.0 and N12.5. It showed that the yield of these 6 varieties could be maintained under the condition of 25 % reduction of nitrogen application.Grains per spike,filled-grain percentage and 1000-grain weight of six high-quality conventional rice varieties are no significantly different at N7.5,N10.0 and N12.5.There was no significant difference in the effective spike of Guixiang 18,Guiyu 12,Guiyu 11 and Guiyu 8 at N7.5,N10.0 and N12.5.The effective spike of Guiyu 9 was not significantly different between N7.5 and N10.0.The effective spike number of Guiyu 18 was not significantly different between N7.5 and N12.5.The effective spike of CK increased significantly with the increase of nitrogen application.The effective spike of these six varieties remained high at low nitrogen level(N7.5),which was the main reason for the high yield at reduced nitrogen application.【Conclusion】The yield of six varieties of high quality conventional rice in Guangxi at low nitrogen level（nitrogen application 112.5 kg/hm2） can reach or exceed the yield at the level of normal nitrogen（nitrogen application 150 kg/hm2） and high nitrogen（nitrogen application 187.5 kg/hm2）,and it is significantly higher than the yield of the control varieties in the Guangxi regional test with the same ripening group under normal nitrogen application. These varieties are nitrogen-efficient varieties that meet the yield requirements of nitrogen-efficient varieties in production promotion. [ABSTRACT FROM AUTHOR]

Returning to the field was the optimal way out for the great deal of slurry from dairy farms in China at the moment. Nitrogen and phosphorus were important nutrient measurable indicators. Variation in nitrogen and phosphorus content was influenced by many natural factors involved in temperature, wind speed, and rainfall so that it was hard to quickly and accurately quantify, leading to the difficulty of returning the slurry to the field. Therefore, aimed at learning the influence of typical seasonal factors on the variation of nitrogen and phosphorus contents in the slurry of large-scale dairy farms together with the prediction results of near-infrared spectroscopy models, it was significantly meaningful that provide the basis of setting up the testing method and standard system for guiding them safely and scientifically returning the slurry to the field. 250 slurry samples were gathered in the whole process of slurry treatment from 27 large-scale dairy farms in Tianjin both in spring and autumn. The influence of season on the distribution characteristics of chemical values of nitrogen and phosphorus in the slurry was analyzed, meanwhile the near-infrared spectra of the whole samples were collected and subjected to the principal component analysis. Then the Partial Least Squares (PLS) was used to establish the seasonal models that involved the spring model, autumn model, and mixed model of both, as well as the demi-season models for the quantified analysis of the nitrogen and phosphorus contents in the slurry. The results showed that the nitrogen and phosphorus contents of the samples appeared varying degrees of variability with seasonal changes. In the seasonal models, the Root Mean Squared Error of prediction set (RMSEP) of three Total Nitrogen (TN) models was 338.26, 334.23, and 382.29 mg/L, respectively. The correlation coefficients of calibration set (Rp) was 0.98, 0.94, and 0.96, respectively. The Residual Predictive Deviations (RPD) was 4.67, 2.83, and 3.56, respectively. RMSEP of three Total Phosphorus (TP) models was 20.04, 22.73, and 23.51 mg/L, respectively. Rp was 0.90, 0.81 and 0.83, respectively. RPD was 2.03, 1.68, and 1.80, respectively. As a whole, the spring model showed a better result than the autumn model, which highlighted the effect of seasonal influence on the prediction. RMSEP of two TN models for mutual prediction between spring and autumn was 934.57 and 845.82 mg/L, respectively. Rp was 0.97 and 0.92, respectively. RPD was 2.28 and 2.58, respectively. RMSEP of two TP models for mutual prediction between spring and autumn was 50.06 and 24.81 mg/L, respectively. Rp was 0.84 and 0.48, respectively. RPD was 0.94 and 1.64, respectively. The overall effect of the demi-season model was inferior compared to the seasonal models. And the performance of the demi-season model was too poor to be used for the determination of nitrogen and phosphorus content in the slurry. In summary, the interior seasonal model of nitrogen and phosphorus in the slurry was superior to the demi-season model and the prediction results of the nitrogen and phosphorus model in the slurry were influenced by the seasonal factors. All the results indicated that the nitrogen and phosphorus contents of slurry were influenced by the seasons. Further objective would be designed to establish the comprehensive forecast models with overall seasonal elements to enhance the feasibility and stability of models that providing the technical support for the development of portable measurement facilities, breaking through the dilemma of quantified analysis under the complicated situation in numerous intensive dairy farms, leading to the slurry recycling back to the field in safely and scientifically meanwhile controlling over the environmental pollution risk. [ABSTRACT FROM AUTHOR]

The Liaohe Delta region, one of the main commodity grain production bases in northeast China, has better temperature and light conditions for paddy rice with higher yields and good taste. However, it is common for local farmers to use up to 270~300 kg N·hm-2 to increase rice grain yield. In the present study, the optimal nitrogen fertilizer application rate（ONR）in this area was determined based on a long-term field experiment with treatments comprising different nitrogen application rates（pure nitrogen 0~420 kg·hm-2）in 2012, 2014, 2016, and 2018. Both yield-response curve and rice-soil nitrogen balance analysis methods were adopted to obtain the ONR. The results showed that ONR for rice planting in Liaohe Delta was determined to be 217 kg·hm-2 via the yield-response curve method and 221~235 kg·hm-2 based on the rice-soil nitrogen balance method. Moreover, the maximal nitrogen use efficiency varied from 36% to 43% with nitrogen application rates ranging from 210 kg·hm-2 to 260 kg·hm-2. Based on a combination of the factors affecting the nitrogen use efficiency of rice, rice target yield and rice-soil nitrogen balance, the ONR for rice planting in Liaohe Delta was finally determined to be 217~235 kg· hm-2,which was 13%~28% lower than the amount conventionally used by local farmers. This study provides a practical theoretical basis for reducing nitrogen surplus for rice planting in Liaohe Delta on the premise of guaranteeing grain yield of rice and is also helpful for reducing the risk of nitrogen leaching to both local soil and underground water. [ABSTRACT FROM AUTHOR]

The garlic (Allium sativum L.) planting in Guanzhong plain of Shaanxi Province has a common problem of excessive application of nitrogen fertilizers. Establishing model of critical nitrogen concentration dilution curve is an effective approach to assess nitrogen status and optimize nitrogen management in garlic production. Based on 2-year field experiments, the model of critical nitrogen concentration dilution curve was constructed for 2 representative garlic varieties‘Cangshan’and‘Gailiangsuan’in local area. In 2015-2016, the experiment was carried out in the Institute of Water Saving Agriculture in Arid Areas of China, Northwest A&F University, Yangling, Shaanxi province, Northwest China (108°5 ′ E、34°19 ′ N); In 2016-2017, the experiment was carried out in Jintiezhai village of Wugong county, Shaanxi province, Northwest China, (108°16 ′ E、34°15 ′N). The experiment was conducted with 6 nitrogen levels: 0 (N0), 60 (N60), 120 (N120), 180 (N180), 240 (N240), 300 (N300) kg/hm². In 2017-2018, the experiment was also conducted in the Institute of Water Saving Agriculture in Arid Areas for model validation. The plant samples of different treatments were collected 5 times during the study periods, i.e., 15, 30, 40, 50, 70 (or 73) d respectively after garlic returning green in spring. Aboveground dry matter, nitrogen concentration and yield of garlic were determined. With the analysis of critical nitrogen concentration and maximum dry matter in each sample date, the results showed that there existed a negative power function between aboveground maximum dry matter and critical nitrogen concentration of garlic. Using the observed maximum and minimum nitrogen concentration at each sampling date, 2 boundary curves were also determined. With the validation of independent test, the normalized root mean square error of‘Cangshan’and ‘Gailiangsuan’were 9.37% and 7.75%, respectively. It indicated that the simulation performance of these models were proven to be excellent. The nitrogen nutrition index (NNI) calculated based on critical nitrogen concentration dilution curve could directly reflect the real- time nitrogen nutrition status of garlic. The NNI values of N240 treatment varied around 1 in 2-year experiment for 2 garlic varieties, meanwhile this treatment can also obtain the maximum relative yields of garlic scape and bulb. Moreover, the NNI values of N300 treatment were greater than 1, which suggested that the nitrogen concentration in N300 treatment was excessive, resulting in the waste of nitrogen fertilizer. The NNI of 2 garlic varieties were both increased gradually with the raise of nitrogen application level in this study. With the nitrogen level lower than or equal to N240, the significant correlations between the NNI and aboveground dry matters, relative yields of garlic scape and bulb were found. According to the change of NNI value under different nitrogen levels, we suggested the appropriate nitrogen application rate of 240 kg/hm² for 2 local garlic varieties in this area. [ABSTRACT FROM AUTHOR]

In order to establish more accurately and rapid pretreatment method for the nitrogen stable isotope analysis of soil ammonium nitrogen, diffusion and N2O produced method were compared, and combined with two commercially available equipment’s, i.e., elemental analyzer-isotope ratio mass spectrometer（Flash HT-IRMS） and trace gas preconcentration-stable isotope mass spectrometry（PreCon-IRMS）, respectively, for the analysis of the nitrogen stable isotope abundance inammonium sulfate reference solutions and soil ammonium nitrogen extracted from different paddy soil samples. The stable isotope measurement results showed that both the diffusion and N2O produced method coupled IRMS analytical systems were able to provide good analytical data for ammonium sulfate reference solutions in accuracy with precision of superior to 0.5% and 0.2%, respectively. However, there was a nitrogen isotope fractionation accrued in the diffusion-treated process, and the test results needed to be corrected by a standard curve. At the same time, the 15N-stable isotope abundance in ammonium nitrogen extracted from different paddy soils were determined by diffusion and N2O produced method. The comparison of the analytical data from the two analytical methods indicated that N2O produced method coupled with PreCon-IRMS provided better nitrogen stable isotope data in reproducibility and accuracy than the data obtained by the other method. In addition, through the auxiliary automatic trace nitrogen conversion-N2O generated device, nitrogen stable isotope abundance of soil ammonium nitrogen could be simultaneously analysis online in batch process, and the pretreatment analysis time was short, the sample consumption was small, only need 10 μg N for one sample（<5 mL soil extract solution）. Therefore, for the analysis of nitrogen isotopes in micro-amounts of soil ammonium, the N2O produced method coupled with PreCon-IRMS analysis method has more advantages than the diffusion method coupled Flash HT-IRMS analysis method. [ABSTRACT FROM AUTHOR]