基于绝热脉冲序列的地下水有机污染晕磁共振探测方法研究

A high pollution ratio is produced of organic in underground water. Traditional technology is difficult to achieve the measurement in situ with high resolution for the pollution plume which is made by organic diffusion. In principle, the method of surface magnetic resonance sounding (MRS) owns the advantages of quantitative analysis for organic pollution plume, however, it is too difficult to break the bottlenecks for the weak signals amplitude of MRS. . As pre-polarization magnetic field (direct current) and adiabatic pulses (frequency-sweep of alternating current) can increase the signal of shallow and deep area, respectively. In this project, an idea which detects the water pollution by utilizing these two approaches together is proposed to maximize both of the MRS signal and excitation fields. Under the effect of earth magnetic field, adiabatic magnetic field and active magnetic field, the forward modelling and formulas are presented to get the simulation methods of adiabatic responses and optimize the excitation conditions. To sufficiently separate the signal of water and organic pollution, a high precision inversion strategy of sparse transverse relaxation time T2 is also need to be improved. Establishing the instrument of active source combining with adiabatic pulses, taking the technology of microsecond frequency sweep and rapid current variation, achieving the measurement of field organic pollution detecting qualitative and quantitative, defining the MRS application conditions in different geological environment. . In this project, a new method which can detect the organic pollution in situ is provided to expand the application areas of MRS. The technique will become one of key scientific technical supports for water pollution govern in our country.

有机物在我国地下水污染中占据很高的比例。针对有机物扩散形成的污染晕，传统技术难以实现野外原位精细测量。地面磁共振方法具有定量分析有机污染的优势，但其信号极为微弱，成为了污染原位监测的瓶颈与难点。. 本项目依据主动源（直流）增大浅部信号，绝热脉冲场（交流扫频式）提高深部信号的特性，提出双场复合发射测量水污染这一设想，以最大化提升磁共振信号幅度及激发场作用范围。推导地磁场、绝热场、主动场共同作用下的三维正演计算方程，研究绝热态响应模拟方法，优化激发条件；探索基于稀疏矩阵的弛豫时间T2高精度反演技术，实现水与污染信号的最优化分离。构建主动源绝热系统，攻克微秒级扫频与快速变流技术，完成野外水污染探测的定位与定量探测，明确不同地质环境下磁共振技术的适用条件。. 本项目将提供一种有机污染原位探测的新方法，拓展磁共振技术应用范围，为我国水污染治理提供关键的科学技术支撑。

本项目积极响应国家生态文明建设号召，针对我国野外大范围有机污染难测量、难量化等瓶颈难题，在传统地面磁共振地下水探测方法技术上，提出了具有定量分析有机污染优势的绝热有机污染晕磁共振测量方法。结合有机污染物痕量、弱响应特性，本项目依据主动源（直流）增大浅部信号，绝热脉冲场（交流扫频式）提高深部信号的特性，提出双场复合发射测量水污染设想，以最大化提升磁共振信号幅度及激发场作用范围。推导了地磁场、绝热场及主动场共同作用下的三维正演计算方程，研究了混场源条件下绝热态磁共振响应模拟方法，并优化了扫频、变幅交流发射激励条件；探索基于稀疏矩阵的弛豫时间T2高精度反演技术，实现水与污染信号的最优化分离；构建主动源绝热探测系统原理样机，攻克微秒级扫频与快速变流技术，并构建了典型有机污染物数据库；结合理论研究及仪器系统研制，完成了野外水污染探测的定位与定量探测，明确不同地质环境下磁共振技术的适用条件。综上所述，本项目提供了一种有机污染原位探测的新方法，有效拓展了传统地面磁共振技术应用范围，为我国水污染治理提供了重要科学技术支撑。