This study aims to construct simple devices to ascertain the concentrations of ammonium (NH4+) and nitrate (NO3-). The device structure comprises a visible and near-infrared absorption meas-urement room, along with an RGB (red, green, and blue) absorption measurement room, con-stituting the two measuring rooms. Both the measurement rooms are equipped with light sources and detectors configured to operate in opposed or thru-beam modes. A tiny processor is utilized for processing the measurements, with an algorithm implemented within its memory. During the algorithm development phase, ranges for measuring the quantity of nutrients were categorized using a discriminant analysis approach. Thirty percent of the soil sample data were utilized as verification data, while the remaining 70 percent served as training data. Nutrient content values from reliable measuring instruments were incorporated into all datasets. Discriminant analysis was employed to classify the amount of NH4+ into five ranges based on the test results. When tested with soil samples, the accuracy was 66.13% compared to the reference value of a reliable measuring device. Similarly, NO3- was classified into four ranges with an accuracy of 81% com-pared to the reference value of a reliable measuring device.

Elevated ammonium (NH4+) concentrations in untreated waterways contribute to eutrophication and dissolved oxygen depletion, which cause severe degradation of water quality. Ion exchange processes are a robust, low operational cost and efficient option for ammonium removal with zeolites being the most widely used. Geopolymers are a sustainable and low-cost option compared to zeolites that follows the same ion exchange technology. In the present study, a metakaolin-based porous geopolymer was synthetized, characterised and validated as adsorbent material. The laboratory batch tests showed a maximum adsorption capacity (Qm) of 18.35 mg/g being 27% higher than reference zeolites. Kinetics followed the Weber-Morris rate equation being the intraparticle diffusion the limiting process and continuous experiments indicated a maximum removal of 97% in the first hours. The material was validated in a wastewater treatment pilot plant where values in pH, electrical conductivity and NH4+ concentration were monitored. The obtained data indicated that the material achieved up to 80% NH4+ removal which is similar to traditional zeolites. The results demonstrate that this sustainable, low-cost and easy-to-install metakaolin-based geopolymer can be used effectively for NH4+ treatment.

Nitrogen (N) is an important mineral nutrient for plant growth, as well as a limiting factor for crop yield, and how to improve the utilization efficiency of N fertilizer by plants is currently a research hotspot. This article uses bioinformatics methods to identify and analyze members of the glutamine synthetase (GS) and glutamate synthase (GOGAT) gene families in pecan. A total of 6 GS genes and 4 GOGAT genes were identified, and their physicochemical properties, gene structures, and homologous evolutionary relationships were analyzed. Analysis of tissue-specific expression of GS and GOGAT genes based on transcriptome data from pecan. The enzyme activities of GS and GOGAT and the gene expression were quantitatively analyzed under different N form ratios in pecan. According to the results, the promoter cis-acting elements of GS and GOGAT genes can be roughly divided into three types: light-responsive elements, hormone-responsive elements, and stress-responsive elements. The results of homologous evolution showed that there was no tandem duplication event for the two gene families, and GS and GOGAT have undergone purification during the evolutionary process. CiGS2s and CiFd-GOGATs were expressed mainly in leaves, and CiNADH-GOGATs were expressed mainly in fruits. The qPCR analysis results showed that T4 treatment significantly increased the expression levels of CiGS and CiGOGAT genes in the leaves. The enzyme activities of GS and GOGAT in pecan were significantly increased under T3, T4, and T5 treatments. In summary, a higher proportion of ammonium nitrogen (NH4+) in the nutrient solution was profit to pecan NH4+ assimilation. This study determined the appropriate nitrogen ratio for pecan, promoting a theoretical basis for reducing environmental pollution caused by nitrogen fertilizer and improving the nitrogen utilization efficiency of pecan. In summary, both CiGSs and CiGOGATs exhibit tissue specificity, and an ammonium-nitrate mixture with a higher proportion of NH4+ is more favorable for NH4+ assimilation in pecan. This study provides a reference basis for further understanding the functions of CiGSs and CiGOGATs in pecan, and offers a theoretical foundation for improving N use efficiency in pecan.

Nitrogen (N) is a major limiting factor for plant growth and vegetable production. Understanding the regulatory mechanisms of N uptake, transport, and assimilation is key to improving nitrogen use efficiency in plants. Ammonium transporters (AMTs) play an important role in plant N metabolism. In this study, we isolated an important AMT1 subfamily member (BcAMT1;5) with a highly conserved signatural AMT1 subfamily motif from flowering Chinese cabbage. Based on functional complementation in yeast mutant 31019b and overexpression of BcAMT1;5 in Arabidopsis, BcAMT1;5 is a functional ammonium transporter. Tissue expression analysis showed that BcAMT1;5 was mainly expressed in roots and showed multiple N regime transcript patterns to respond to varying nutritional conditions. This was up-regulated by N-deficiency and down-regulated by supplying NH4+. The glucuronidase (GUS) activities of BcAMT1;5pro::GUS showed a similar change in response to different N conditions. Overexpression of BcAMT1;5 accelerated the growth of transgenic seedlings, increased NH4+ net influxes, and enhanced the content and accumulation of NH4+ and NO3- at low N concentrations. Additionally, it increased the transcript levels of N assimilation-related genes in shoots. These results indicate that the transcriptional regulation of BcAMT1;5 in flowering Chinese cabbage may participate in N uptake and assimilation under various N conditions.

Differences in the physical and chemical properties of reclaimed water (RW) and natural surface water (SW) lead to the differences in terms of nitrogen and phosphorus release when pipeline sediments enter these water bodies. The nitrogen and phosphorus release kinetics from pipe sediments with different particle sizes have been investigated. The results demonstrated that both SW and RW had a pH buffering effect after sediment addition, and the final pH (approximately 8.1) of RW was lower. The release of total phosphorus (TP) and ammonia nitrogen ( NH₄⁺-N) fitted the first-order kinetic model where the release of TP reached equilibrium; TP release was inhibited in both SW and RW, where RW exhibited the lowest (by a factor of 1.23~2.44) release (0.002 mg/g). The release of NH4+-N was promoted in both SW and RW; the maximum release in RW was 0.0188 mg/g. The amounts of NH₄⁺-N released in SW and RW were 1.02-1.40 and 1.30-1.80 times that of the control group (CG), respectively. The percentage of TP and NH₄⁺-N release in the three groups was highest in 75-154 μm pipe sediment, reaching 34.53% and 43.51% in SW and RW, respectively. These results can assist in the development of water quality evolution models for specific urban scenarios, and provide important guidance for the precise regulation of recharge water quality during and after rainfall.

The seasonal and vertical spatial variation characteristics of total N, NH4+—N and NO3-—N in the soil in Picea mongolica forest at different stand ages were studied. The results showed that: (1) NH4+ —N in the soil in Picea mongolica forest was positively correlated with sample date, soil NO3-—N and forest age (P <0.05), and negatively correlated with soil depth (P < 0.01). NO3-—N in the soil in Picea mongolica forest was negatively correlated with sample date and forest age (P < 0.05), and significantly negatively correlated with soil depth (P < 0.01); (2) the content of NH4+—N is greater than that of NO3-—N in each soil layer of Picea mongolica forest at three forest ages. The correlation analysis showed which had an impact on the content of NH4+—N and NO3-—N in the soil in Picea mongolica forest. The content was lower in February and November, and higher in May and August；(3) The contents of total N, NH4+—N and NO3-—N in the soil of Picea mongolica forest in the three forest ages increased with the depth of soil layer (0-50cm), and showed an overall downward trend. The contents of NH4+—N in the soil layer of young forest (0-10cm, 10-20cm and 20-30cm, 30-40cm and 40-50cm) were significantly different (P＜0.05), and the contents of NO3-—N were also significantly different (P＜0.05), while their contents of middle-aged forest and near mature forest increased with the depth of soil layer, There was no significant difference in the content of NH4+—N; (4) The content of NH4+—N in the soil in Picea mongolica forest generally showed the following change trend near mature forest > middle-aged forest > young forest. The change trend of soil NO3-—N content is consistent with that of the content of NH4+—N in the soil in Picea mongolica forest.