Efficient and sustained inhibition of ammonia nitrogen release from sediment in water by microbial self-aggregation zeolite layer.

Despite global efforts to manage water eutrophication, the continual release of ammonia nitrogen from sediments maintains the eutrophic state of water bodies, presenting serious challenges to the management. In order to find an efficient method for sediment remediation, the experiment of using signal molecules to enhance the adhesion of microorganisms on zeolite was carried out. Five different zeolitic ammonium adsorptions were examined using two different signal molecules, N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) and N-(ß-ketocaproyl)-DL-homoserine lactone (C6), to enhance microbial attachment on two types of zeolites. The results showed that the modified microbial attached Z1 zeolite reinforced with signal molecule C6 had the best effect. The effect was better in the case of high ammonium adsorption, and the TN removal could reach 7.99 mg·L-1 with an inhibition rate of 90.08%. The ammonia nitrogen removal reached 4.75 mg·L-1 with an inhibition rate of 87.64%, and the ammonia nitrogen and total nitrogen of the overlying water reached the surface III water quality standard. In addition, the addition of the signal molecule increased the zeta potential on the surface of the bacterial colloid. In addition, the amount of protein I in the dissolved organic matter (DOM) fraction increased, improving microbial adhesion ability and facilitating their attachment to the zeolite surface. The signal molecule C6 could increase the zeta potential of microbial surface and promote the production of protein I, thus strengthening the attachment of zeolite biofilm and improving the water quality.

A study on the simultaneous determination of nitrogen content and 15N isotope abundance in plants using peak height intensities at m/z 28 and 29.

A method for simultaneous determination of nitrogen content and 15N isotope abundance in plants was established by Elemental analysis-gas isotope ratio mass spectrometry. Taking poplar leaves and l-glutamic acid as standards, nitrogen content was determined using the standard curve established by weighted least squares regression between the mass of nitrogen element and the total peak height intensity at m/z 28 and 29. Then the 15N isotope abundance was calculated with the peak height intensity at m/z 28 and 29. Through the comparison of several sets of experiments, the impact of mass discrimination effect, tin capsule consumables, isotope memory effect, and the quality of nitrogen on the results were assessed. The results showed that with a weight of 1/x2, the standard curve has a coefficient of determination (R2) of 0.9996. Compared to the traditional Kjeldahl method, the measured nitrogen content deviated less than 0.2 %, and the standard deviation (SD) was less than 0.2 %. Compared to the sodium hypobromite method, the 15N isotopic abundances differed less than 0.2 atom%15N, and the SD was less than 0.2 atom% 15N. The established method offers the advantages of being fast, simple, accurate, and high throughput, providing a novel approach for the simultaneous determination of nitrogen content and 15N isotope abundance in plant samples.