• ISSN 2097-1893
  • CN 10-1855/P

基于多频段GPR早期信号的绿洲盐渍土水分反演

Soil moisture inversion of oasis saline soil based on early-time signals of multi-frequency GPR

  • 摘要: 干旱区绿洲农业持续面临水资源短缺与土壤次生盐渍化双重挑战,准确获取土壤水分时空分布特征对维系农业可持续发展意义重大. 探地雷达(ground penetrating radar, GPR)等地球物理探测方法已成为中尺度土壤水分监测的可行手段. 然而,传统GPR方法在高电导率盐渍土中因电磁波衰减与散射导致探测性能下降,同时现有GPR早期信号研究多局限于均质或低损耗介质,对高盐分与空间异质性并存的绿洲农田环境缺乏系统性验证,严重制约了该方法在盐渍土水分反演中的推广应用. 本研究通过构建基于椭圆随机介质的多尺度盐渍土模型,结合正演模拟与新疆绿洲棉田野外试验,量化对比了天线频率(250 MHz和1000 MHz)与早期信号指标中载频振幅(carrier frequency amplitude, CFA)和平均包络振幅(average envelope amplitude, AEA)在盐渍土水分反演中的表现. 结果表明:(1)两种早期信号方法在电导率高达0.36 S/m的盐渍土中仍保持稳定反演精度(R2 > 0.60),证实了GPR早期信号方法在强盐渍环境中定量反演土壤水分的可行性;(2)基于早期信号的盐渍土水分反演精度对天线频率和介质异质性高度敏感,其中250 MHz低频天线在0~30 cm耕作层水分监测中表现出较好的深度适应性和抗干扰能力,而1000 MHz天线对表层小尺度异质体的散射效应更为敏感;(3)CFA指标在低土壤水(< 15%)条件下对介电常数变化有更高的灵敏度,而AEA指标在高含水量(> 20%)环境中表现出更高的稳定性. 本研究提出了针对不同土壤异质性程度和水分条件的GPR早期信号盐渍土水分反演指标优化策略,并通过野外试验验证了250 MHz天线配合CFA、AEA指标在绿洲农田环境的应用可行性,为干旱区绿洲农业水盐精准管理提供创新技术支持.

     

    Abstract: Oasis agriculture in arid regions persistently faces dual challenges of water scarcity and secondary soil salinization, making accurate acquisition of spatiotemporal soil moisture distribution characteristics critical for sustaining agricultural development. Geophysical detection methods such as ground penetrating radar (GPR) have become viable approaches for mesoscale soil moisture monitoring. However, conventional GPR methods suffer performance degradation in high-conductivity saline soils due to electromagnetic wave attenuation and scattering. Additionally, existing GPR early-time signal studies are predominantly limited to homogeneous or low-loss media, lacking systematic validation in oasis farmland environments characterized by high salinity and spatial heterogeneity, which severely constrains the widespread application of this method in saline soil moisture inversion. This study constructs a multi-scale saline soil model based on elliptical random media, integrating forward simulations with field experiments in Xinjiang oasis cotton fields to quantitatively compare the performance of antenna frequencies (250 MHz and 1000 MHz) and early-time signal indices including carrier frequency amplitude (CFA) and average envelope amplitude (AEA) in saline soil moisture inversion. The results demonstrate that: (1) Both early-time signal methods maintain stable inversion accuracy (R2>0.60) in saline soils with conductivities up to 0.36 S/m, confirming the feasibility of GPR early-time signal methods for quantitative soil moisture inversion in highly saline environments; (2) The accuracy of saline soil moisture inversion based on early-time signals is highly sensitive to antenna frequency and medium heterogeneity, with the 250 MHz low-frequency antenna exhibiting superior depth adaptability and anti-interference capability for monitoring the 0-30 cm plough layer, while the 1000 MHz antenna shows heightened sensitivity to scattering effects from small-scale surface heterogeneities; (3) The CFA index demonstrates higher sensitivity to dielectric constant variations under low soil moisture conditions (<15%), whereas the AEA index exhibits enhanced stability in high moisture environments (>20%). This study proposes an optimized strategy for GPR early-time signal saline soil moisture inversion indices tailored to different degrees of soil heterogeneity and moisture conditions, and validates through field experiments the practical applicability of 250 MHz antennas combined with CFA and AEA indices in oasis farmland environments, providing innovative technical support for precision water-salt management in arid oasis agriculture.

     

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