Method for preparing water body phosphate oxygen isotope sample through in-situ enrichment

Abstract

The invention, which belongs to the environment-friendly monitoring method field, relates to a method for preparing a water body phosphate oxygen isotope sample through in-situ enrichment. The methodcomprises the following steps: immersing a Zr-Oxide gel film into a water body, fishing out the Zr-Oxide gel film after a period of time, putting the Zr-Oxide gel film into a sodium hydroxide solution, carryin gout oscillating for 24 hours, and carrying out filtering to obtain a phosphorus-containing eluent; adjusting the pH value of the eluent to 5.8 and adding a cerous nitrate solution to adjustthe pH value to 5.5; adding nitric acid into a cerium phosphate precipitate, adding cation exchange resin after dissolving of the cerium phosphate precipitate, and carrying out oscillation for 12h; filtering the solution after cation exchange resin processing into a black centrifuge tube, adjusting the pH value to 8.5 by using ammonia water, adding a silver nitrate solution, carrying out centrifuging to obtain a silver phosphate precipitate; washing the silver phosphate precipitate with pure water, adding hydrogen peroxide to react for more than 3 hours, carrying out centrifuging to retain the precipitate, washing the centrifugal precipitate with pure water, and carrying out freezing and drying. Therefore, large-volume sampling can be avoided effectively; and the difficulty or steps of filtration and impurity removal can be reduced or simplified obviously. The method is a novel method for preparing a water body phosphate oxygen isotope sample.

Description

technical field [0001] The invention relates to a method for preparing a water body phosphate oxygen isotope sample, in particular to a method for preparing a water body phosphate oxygen isotope sample by in-situ enrichment; it belongs to an environmental protection monitoring method. Background technique [0002] Phosphate (PO 4 ) is a key pollutant that causes eutrophication in rivers, lakes and other water bodies. Sources of phosphate in water include not only exogenous industrial and agricultural wastewater, domestic sewage, and atmospheric dry and wet deposition, but also endogenous degradation of biological residues and release of phosphorus from sediments. The dynamic changes of different phosphate source types and input quantities will produce different environmental effects. Phosphate oxygen isotope (δ 18 o P ) as a new and effective tracer tool has gradually attracted widespread attention, and has been applied to the source analysis and biogeochemical research ...

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Problems solved by technology

[0003] At present, it is common to first convert the phosphate in the water to be tested into high-purity, stable Ag. 3 PO 4 Solid sample, then tested for Ag by EA-IRMS high temperature pyrolysis method 3 PO 4 Medium delta 18 o P , there are defects such as cumbersome operation, time-consuming and laborious:

[0004] 1) PO in natural water bodies 4 The content is low, and a large amount of raw water needs to be collected to enrich the sufficient amount of PO required for the test 4 , the workload of water collection is heavy and the cost is high

[0005] 2) It is necessary to perform cumbersome process operations such as filtration, impurity removal, and passive phosphorus concentration on raw water, and it is easy to cause phosphorus loss

[0006] 3) The raw water collection process is instantaneous sampling, and the obtained δ 18 o P The composition represents the δ at a certain moment 18 o P Composition information has a certain degree of randomness, so it is difficult to accurately reflect the dynamic change information of phosphate in raw water

[0007] 4) Impurities such as dissolved organic matter DOM and various anions / cations in raw water will seriously interfere with δ 18 o P Purification operation and test analysis, it needs to be completely removed, otherwise it will affect the δ 18 o P Accuracy of test results

Overall, δ 18 o P The separation and purification operation is a series of continuous and complex multi-step impurity removal and PO 4 extraction process (e.g. CePO 4 step washing Cl - The number of times is even as high as more than ten times), which not only consumes a lot of time and reagent materials, but also easily leads to low phosphorus recovery and fractionation of oxygen isotopes, which eventually leads to Ag 3 PO 4 The error of the sample result is large

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