基于气体膜扩散机理和实时电化学传感机制的氨气原位动态监测技术

As the most important alkaline gas, ammonia plays an indispensable role in water, soil and atmospheric environment. Moreover, it is also considered as the main reason for water eutrophication, non-point source pollution, atmospheric haze and other urgent environmental issues. Although some ammonia monitoring approaches have been developed in recent years, they have one common major drawback, that is, they cannot achieve in-situ real-time dynamic ammonia monitoring. To solve this problem, in this study, a new membrane-based electrochemical ammonia sensing technique is proposed. The optimization experiment will be firstly implemented to select optimal membrane that can selectively extract ammonia through, to select optimal inner receiving solution that can immediately react with permeated ammonia to produce product that can be electrochemically detected, and to select optimal electrochemical transducer that can real-time detect reaction product. In addition, the relationship between ammonia permission mechanisms, diffusion rate and real-time response of electrochemical transducer signal will be investigated to quantitatively analyze real-time in-situ ammonia concentration. Furthermore, in order to completely meet the requirements of in-situ ammonia monitoring in water, soil and atmospheric environment, four kinds of actual ammonia monitoring situations will be considered, so that four kinds of in-situ ammonia monitoring methods, i.e., immersion, flow-injection, interfacial suspension and open-air ammonia monitoring methods, will be specifically come up in this study. In the era of big-data, the development of such universal in-situ ammonia monitoring technique not only provides reliable real-time data for solving ammonia related environmental issues, more importantly, point out a new exploration direction for in-situ real-time trace gases monitoring, which is of great significance for both academic and practical study.

氨气作为最重要的碱性气体，在与人们生产生活息息相关的水、土壤和大气环境中都起着非常重要的作用，也是引起水体富营养化、农业面源污染和大气雾霾等众多亟待解决的环境问题的重要原因。当前对于氨气监测技术存在的最大问题就是很少能做到原位实时监测，本研究就是针对解决这个关键问题，提出了一种新的基于膜扩散机理和电化学响应机制的原位氨气实时传感技术，通过筛选和优化实验条件，使原位氨气能够选择性的透过膜并与内部吸收液反应，通过探究并构建氨气透过膜机理、速率与实时电化学响应信号变化之间的关系，来实时分析原位氨气浓度，并结合四种实际氨气原位监测形式，有针对性的提出浸入式、流动注射式、界面悬挂式和开放式的原位氨气监测技术，使其成为一种适用于水、土和大气中氨气原位监测的通用技术，不仅为大数据时代下解决氨气相关的环境问题提供可靠的原位数据支持，也为原位微量气体的实时监测提供了一种新思路，具有重要的学术和应用价值。

原位实时氨监测是防控水体富营养化、农业面源污染以及大气雾霾等亟待解决的环境问题的重要手段。鉴于目前监测仪器制造成本高，人员投入大，难以实现高分辨率原位监测等问题，本项目通过耦合膜透过与电化学检测技术，自主研发了基于膜扩散的电化学氨气实时传感系统。首先，项目完成了核心技术条件选择与优化，包括确定微孔疏水气透膜（0.22μm的PTFE与PVDF）作为耐用膜材料、特制硼酸溶液（含0.5M硼酸）作为特异吸收剂以及改进的四点电极电导法作为精准离子检测的电化学方法，以实现高灵敏度长期稳定监测。同时，针对不同的监测应用场景需求，结合水、水/土-气和气三种氨气实际存在的界面特点，分别提出和研发了基于膜透过的浸入式、流动注射式、界面悬挂式三种氨气实时监测技术和传感装置，并探究了三种形式下的膜扩散驱动机理、膜扩散方式和电化学信号响应机制，由此建立了原位氨浓度/通量-膜扩散速率-实时电信号之间的响应关系，继而系统地构建了基于膜扩散和电化学传感的氨气原位连续监测技术原理，并成功完成了基于膜透过的浸入式、流动注射式、界面悬挂式的氨气监测原理的验证以及潜在影响因素（温度、流速等）的排除与校正。最后，通过与当前常用的氨监测方法对比，验证了所研发技术在多种实际环境下（天然开放水体、复杂封闭水体和农田等）进行原位氨氮/氨挥发实时监测的可行性、优越性和应用潜力。本项目的开展不仅能为原位氨气实时动态监测提供有力的技术支持和可靠的数据支持，也将为探索环境微量气体在线监测提供新的理论依据，具有重要的学术意义和广阔的应用潜力。