Measurement method of nitrogen and oxygen stable isotope of nitrate in seawater

Abstract

The invention belongs to the technical field of water nitrate pollution treatment and control, and in particular relates to a measurement method of nitrogen and oxygen stable isotope of nitrate in seawater. The method comprises the steps of carrying out off-line treatment on the nitrate in the seawater to be measured by denitrifying bacteria without N2O reductase activity, and then converting the treated nitrate into nitrous oxide gas; and carrying out on-line continuous measurement on the nitrogen and oxygen stable isotope by combining a trace gas pre-concentrating apparatus (Precon) and gas chromatography (GC)-isotope ratio mass spectrometer (MS). After the measurement method is used, a culture method of the denitrifying bacteria is optimized, a formula of a culture medium is improved, the nitrate is not added, the cultivation effect is relatively good, the growth of the bacteria is stable, whether the culture medium has the residual nitrate or not after enrichment culture is not required to be tested, and the pollution is not caused in the subsequent sample treatment; the culture medium is good in bacteria enrichment effect, short in bacterial culture period and high in efficiency, and the cultivation cost is reduced.

Description

technical field [0001] The invention belongs to the technical field of treatment and control of nitrate pollution in water bodies, and specifically relates to a method for determining stable isotopes of nitrogen and oxygen in seawater nitrate. Background technique [0002] In recent decades, with the rapid development of social economy and the intensification of human activities, a large number of pollutants produced by industry, life, and agricultural activities have entered the coastal waters, resulting in the concentration of nitrogen nutrients in my country's coastal waters seriously exceeding the standard, and the degree of eutrophication in the sea area. Serious year by year, red tide occurs frequently. Therefore, it is particularly important to control nitrogen pollution in coastal waters and to study the sources of nitrogen in water bodies and biogeochemical cycles. [0003] As a new technology, stable isotope method has been widely used in oceanographic research. N...

AI Technical Summary

Problems solved by technology

Bacterial denitrification method has been widely used in foreign countries. At present, domestic denitrification method is rarely used in the determination of nitrate nitrogen and oxygen isotopes. The main reasons that affect the widespread use of this method in China are: (1) The requirements for the cultivation of denitrifying bacteria are relatively harsh. Discontinuous and unstable culture will affect the results of sample pretreatment; (2) Nitrate is added to the denitrifying bacteria culture formula commonly used at home and abroad. If the net added nitrate is not consumed during the bacterial enrichment culture process, the sample will be polluted. cause errors in sample determination

(3)N 2 The on-line continuous measurement of O gas generally uses Tracegas or Gasbench for pre-concentration and separation of gas. These instruments are relatively expensive, and there are few units that have purchased these instruments in China, which limits the application of this method in China.

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