水质

[中文适用范围]： 本文件规定了一种通过α光谱法测定各类水中227Ac活度浓度的测试方法。该测试方法适用于在正确取样和处理以及测试样品制备后测试供水/饮用水、雨水、地表水和地下水、海水以及冷却水、工业用水、生活用水和工业废水样品（参见 ISO 5667-1、ISO 5667-3，检测限取决于样品量、所用仪器、背景计数率、检测效率、计数时间、化学产量和子代生长。本文所述方法使用目前可用的α能谱仪，在直接测量227Ac的α峰时，检测限约为 0.03 Bq·l−1。该检测限低于世界卫生组织对任何锕系元素α发射体的饮用水安全饮用标准（0.1 Bq·l−1）。[4] 对于 1 升的样品，计数时间为 48 小时即可达到此值。只有一小部分 227Ac 通过α发射衰变（~1,42 %)。降低该方法检测限的一种方法是等待，让 227Ac 的子代生长，然后测量 227Ac 的 alpha 子代峰（例如 215Po）。这是一种较长的技术，但通过在净化后约 90 天重新计数样品，可以获得约 0,000 2 Bq·l−1 的较低检测限。可以在 90 天之前重新计数样品，但检测限会更高。本文件中描述的测试方法可用于计划、现有和紧急暴露情况以及废水和液体流出物，并进行特定修改，以增加总体不确定性、检测限和阈值。对于紧急情况，最好减少计数时间而不是样品量。本文件不涉及对悬浮物吸附的 227Ac 的分析。 [外文原描述]： This document specifies a test method to determine the activity concentration of 227 Ac in all types of waters by alpha spectrometry. The test method is applicable to test samples of supply/drinking water, rainwater, surface and ground water, marine water, as well as cooling water, industrial water, domestic, and industrial wastewater after proper sampling and handling and test sample preparation (see ISO 5667 - 1 , ISO 5667 - 3 , ISO 5667 - 10 ). Filtration of the test sample is necessary. The detection limit depends on the sample volume, the instrument used, the background count rate, the detection efficiency, the counting time, the chemical yield, and the progeny ingrowth. The method described in this document, using currently available alpha spectrometry apparatus, has a detection limit of approximately 0,03 Bq·l −1 , when directly measuring the alpha peak of 227 Ac. This detection limit is lower than the WHO criteria for safe consumption of drinking water for any actinide alpha emitter (0,1 Bq·l −1 ). [ 4 ] This value can be achieved with a counting time of 48 h for a sample volume of 1 l. Only a small fraction of 227 Ac decays through alpha emissions (~1,42 %). An option to lower the detection limit of the method is to wait, let the progenies of 227 Ac grow in, and measure an alpha progeny peak of 227 Ac (e.g. 215 Po). This is a longer technique, but a lower detection limit of approximately 0,000 2 Bq·l −1 can be obtained by re-counting the sample approximately 90 days after purification. The sample can be re-counted before 90 days, but with a higher detection limit. The test method(s) described in this document can be used during planned, existing and emergency exposure situations as well as for wastewaters and liquid effluents with specific modifications that can increase the overall uncertainty, detection limit and threshold. For an emergency situation, it is preferable to reduce the counting time rather than the sample volume. The analysis of 227 Ac adsorbed to suspended matter is not covered by this document.