~3He管中子土壤水分测量装置提高测量精度
|
摘要
宇宙射线中子法是一种先进的测定区域土壤水分含量的方法,但国内外对其制约因素的研究仍不成熟。该研究利用商业化宇宙射线中子仪(CRS1000)和自己组装的~3He管中子水分探测器(~3He管),在中国农业大学上庄试验站对土壤含水量进行持续监测,将测量的结果与烘干法测量的结果进行对比分析,验证2种仪器测量的准确性和稳定性,并比较2种仪器对土壤水分变化响应的灵敏性差异。研究结果显示,CRS1000和~3He管具有较高的稳定性,在太阳活动剧烈时,有必要考虑对中子入射强度进行校正;通过与烘干法获得的土壤水分数据比较,CRS1000和~3He管测量数据的均方根误差分别为0.036、0.015 cm~3/cm~3,说明2种仪器进行土壤水分测量的结果非常准确;利用2种仪器获得的土壤水分曲线的变化趋势具有较高的一致性,在降水事件发生时,2种仪器都迅速作出响应,但~3He管对土壤水分变化的反应更加灵敏,测量精度更高。同时,组装的~3He管中子水分探测器成本约为商业化宇宙射线中子仪的1/2,降低了成本,具有更加广阔的应用前景。
As a significant part of water resources in the ecosystem cycle,soil moisture plays an extremely important role in the process of matter and energy exchange between the surface and the atmosphere.But it is very difficult to accurately measure large scale soil moisture.Cosmic-ray neutron method is a promising way to measure soil moisture for intermediate spatial scales.This method bridges the scale gap between point measurements of soil moisture and remote sensing,making significant contribution to the measurement of soil moisture within a regional level.In 2008,Zreda et al.introduced a method to measure average soil water content over a larger area with a cosmic-ray neutron sensor(CRS).The footprint of a CRS covers a circle with an approximate radius of 300 m and the effective measurement depth varies between 10 and 70 cm below the soil surface.Desilets et al.proposed an equation with three constant shape parameters(a_0,a_1,a_2) and one calibration parameter(N_0),which needs to be calibrated with soil moisture values determined by oven-drying method from field soil samples in 2010.Franz et al.(2013) developed a universal calibration function for determination of soil moisture with cosmic-ray neutrons that takes into account three influencing factors including pressure,incoming neutron flux and water vapor in the air.Meanwhile,other scholars have explored other factors that influence the soil moisture content,including the depth and range of detection,the lattice water,soil organic carbon and vegetation biomass.In this study,experiments were conducted in China Agricultural University Experiment Station with commercial cosmic-ray neutron sensors(CRS1000) and self-assembly ~3He tube neutron moisture detector(~3He tube).In order to verify the accuracy and stability of these two instruments,we compared the soil moisture content data with the result from oven-drying method.Meanwhile,we made a comparison between the sensitivity of these two instruments for the response of precipitation event.Before using the two instruments,we needed to calibrate the N_0 from neutron conversion equation.And the calibration was based on soil moisture content derived directly from soil samples taken within the footprint of the sensor.After one correction,N_0 had certain stability over a long time.The intensity of the incoming neutron was one factor that affected the neutron count of the instruments,and it was necessary to calibrate the intensity of the incoming neutron when the solar activity was intense.Oven-drying method was used to measure the average moisture content within the footprint of the sensors.Then we used the average moisture content data to verify the stability of the two kinds of measurement.Comparing the soil moisture content data obtained from oven-drying method,it can be calculated that the root mean square error of the two instruments were respectively 0.036 and 0.015 cm~3/cm~3.It showed that the measurement results of two instruments were more accurate.The original neutron counts per hour of ~3He tube were about 10 times more than CRS1000,so we can conclude that the former was far more accurate than the latter.After corrected,soil moisture measurement results of CRS1000 and ~3He tube were more consistent.When precipitation event occurred,the change in ~3He tube was even more pronounced than CRS1000,showing that ~3He tube was more sensitive than CRS1000.At the same time,the cost of self-assembly ~3He tube neutron moisture detector was about half of commercial cosmic-ray neutron sensors.So ~3He tube will have a better application prospect.
As a significant part of water resources in the ecosystem cycle,soil moisture plays an extremely important role in the process of matter and energy exchange between the surface and the atmosphere.But it is very difficult to accurately measure large scale soil moisture.Cosmic-ray neutron method is a promising way to measure soil moisture for intermediate spatial scales.This method bridges the scale gap between point measurements of soil moisture and remote sensing,making significant contribution to the measurement of soil moisture within a regional level.In 2008,Zreda et al.introduced a method to measure average soil water content over a larger area with a cosmic-ray neutron sensor(CRS).The footprint of a CRS covers a circle with an approximate radius of 300 m and the effective measurement depth varies between 10 and 70 cm below the soil surface.Desilets et al.proposed an equation with three constant shape parameters(a_0,a_1,a_2) and one calibration parameter(N_0),which needs to be calibrated with soil moisture values determined by oven-drying method from field soil samples in 2010.Franz et al.(2013) developed a universal calibration function for determination of soil moisture with cosmic-ray neutrons that takes into account three influencing factors including pressure,incoming neutron flux and water vapor in the air.Meanwhile,other scholars have explored other factors that influence the soil moisture content,including the depth and range of detection,the lattice water,soil organic carbon and vegetation biomass.In this study,experiments were conducted in China Agricultural University Experiment Station with commercial cosmic-ray neutron sensors(CRS1000) and self-assembly ~3He tube neutron moisture detector(~3He tube).In order to verify the accuracy and stability of these two instruments,we compared the soil moisture content data with the result from oven-drying method.Meanwhile,we made a comparison between the sensitivity of these two instruments for the response of precipitation event.Before using the two instruments,we needed to calibrate the N_0 from neutron conversion equation.And the calibration was based on soil moisture content derived directly from soil samples taken within the footprint of the sensor.After one correction,N_0 had certain stability over a long time.The intensity of the incoming neutron was one factor that affected the neutron count of the instruments,and it was necessary to calibrate the intensity of the incoming neutron when the solar activity was intense.Oven-drying method was used to measure the average moisture content within the footprint of the sensors.Then we used the average moisture content data to verify the stability of the two kinds of measurement.Comparing the soil moisture content data obtained from oven-drying method,it can be calculated that the root mean square error of the two instruments were respectively 0.036 and 0.015 cm~3/cm~3.It showed that the measurement results of two instruments were more accurate.The original neutron counts per hour of ~3He tube were about 10 times more than CRS1000,so we can conclude that the former was far more accurate than the latter.After corrected,soil moisture measurement results of CRS1000 and ~3He tube were more consistent.When precipitation event occurred,the change in ~3He tube was even more pronounced than CRS1000,showing that ~3He tube was more sensitive than CRS1000.At the same time,the cost of self-assembly ~3He tube neutron moisture detector was about half of commercial cosmic-ray neutron sensors.So ~3He tube will have a better application prospect.
引文
[1]仝兆远,张万昌.土壤水分遥感监测的研究进展[J].水土保持通报,2007,27(4):107-113.Tong Zhaoyuan,Zhang Wanchang.Progress of soil moisture monitoring by remote sensing[J].Bulletin of Soil and Water Conservation,2007,27(4):107-113.(in Chinese with English abstract)
[2]刘志明,张柏,晏明,等.土壤水分与干旱遥感研究的进展与趋势[J].地球科学进展,2003,18(4):576-583.Liu Zhiming,Zhang Bai,Yan Ming,et al.Some research advances and trends on soil moisture and drought monitoring by remote sensing[J].Advance Earth Sciences,2003,18(4):576-583.(in Chinese with English abstract)
[3]邓英春,许永辉.土壤水分测量方法研究综述[J].水文,2007,27(4):20-24.Deng Yingchun,Xu Yonghui.A review of soil moisture measurement methods[J].Hydrology,2007,27(4):20-24.(in Chinese with English abstract)
[4]李琴,陈曦,Frank Veroustraete,等.干旱半干旱区土壤含水量反演与验证[J].水科学进展,2010,21(2):201-207.Li Qin,Chen Xi,Frank V,et al.Validation of soil moisture retrieval in arid and semi-arid areas.Advances in water science,2010,21(2):201-207.(in Chinese with English abstract)
[5]Zreda M,Desilets D,FerréT P A,et al.Measuring soil moisture content non-invasively at intermediate spatial scale using cosmic-ray neutrons[J].Geophys Res Lett,2008,35(21).DOI:10.1029/2008GL035655.
[6]Desilets D,Zreda M,FerréT P A.Nature’s neutron probe:Land surface hydrology at an elusive scale with cosmic rays[J].Water Resour Res,2010,46(11).DOI:10.1029/2009WR008726.
[7]Franz T E,Zreda M,FerréT P A,et al.Measurement depth of the cosmic-ray soil moisture probe affected by hydrogen from various sources[J].Water Resour Res,2012,48(8):1-9.
[8]Hess W N,Patterson H W,Wallace R,et al.Cosmic-ray neutron Energy Spectrum[J].Phys Rev,1959,116(2):445-447.
[9]Kodama M,Nakai K,Kawasaki S,et al:An application of cosmic-ray neutron measurements to the determination of the snow-water equivalent[J].Journal of Hydrology,1979,41(1):85-92.
[10]Franz T E,Zreda M,Rosolem R,et al.A universal calibration function for determination of soil moisture with cosmic-ray neutrons[J].Hydrol Earth Syst Sci,2013,17(12):453-460.
[11]Zreda,M,Shuttleworth,W J,Zeng X,et al.COSMOS:the cosmic-ray soil moisture observing system[J].Hydrol Earth Syst Sci Discuss,2012,9(4):4505-4551.
[12]Rivera Villarryes C A,Baroni G,Oswald S E.Integral quantification of seasonal soil moisture changes in farmland by cosmic-ray neutrons[J].Hydrol Earth Syst Sci,2011,15(12):3843-3859.
[13]Rivera Villarryes,C A,Baroni G,Oswald S E.Calibration approaches of cosmic-ray neutron sensing for soil moisture measurement in cropped fields[J].Hydrol Earth Syst Sci,2013,10(4):4237-4274.
[14]Rosolem R,Shuttleworth W J,Zreda M,et al.The effect of atmospheric water vapor on neutron count in the cosmic-ray soil moisture observing system[J].Journal of Hydrology,2013,14(5):1659-1671.
[15]Chrisman B,Zreda M.Quantifying mesoscale soil moisture with the cosmic-ray rover[J].Hydrol Earth Syst Sci Discuss,2013,10(6):7127-7160.
[16]Almeida A C,Dutta R,Franz T E,et al.Combining cosmic-ray neutron and capacitance sensors and fuzzy inference to spatially quantify soil moisture distribution[J].Sensors Journal IEEE,2014,14(10):3465-3472.
[17]Baroni G,Oswald S E.A scaling approach for the assessment of biomass changes and rainfall interception using cosmic-ray neutron sensing[J].Journal of Hydrology,2015,525:264-276.
[18]焦其顺,朱忠礼,刘绍民,等.宇宙射线快中子法在农田土壤水分测量中的研究与应用[J].地球科学进展,2013,28(10):1136-1143.Jiao Qishun,Zhu Zhongli,Liu Shaomin,et al.Research and application of cosmic-ray fast neutron method to measure soil moisture in the field[J].Advances in Earth Science,2013,28(10):1136-1143.(in Chinese with English abstract)
[19]贾晓俊,施生锦,黄彬香,等.宇宙射线中子法测量土壤水分的原理及应用[J].中国农学通报,2014,30(21):113—117.Jia Xiaojun,Shi Shengjin,Huang Binxiang,et al.Principles and application of cosmic-ray neutron method for measuring soil moisture[J].Chinese Agricultural Science Bulletin,2014,30(21):113-117.(in Chinese with English abstract)
[20]赵纯,袁国富,刘晓,等.宇宙射线土壤水分观测方法在黄土高原草地植被的应用[J].土壤学报,2015,52(6):1438-1444.Zhao Chun,Yuan Guofu,Liu Xiao,et al.Application of cosmic-ray method to soil moisture measurement to grassland in the loess plateau[J].Acta Pedologica Sinica,2015,52(6):1438-1444.(in Chinese with English abstract)
[21]王秋铭,王胜,樊军.宇宙射线快中子法在土壤水分测量中的应用:以陕北六道沟流域为例[J].中国水土保持科学,2015,13(5):125-131.Wang Qiuming,Wang Sheng,Fan Jun.Application of cosmic-ray fast neutron method to measure soil moisture:A case study of Liudaogou basin in Shanxi[J].Science of Soil and Water Conservation,2015,13(5):125-131.(in Chinese with English abstract)
[22]Ingo Heidbüchel,Andreas Güntner,Theresa Blume.Use of cosmic-ray neutron sensors for soil moisture monitoring in forests[J].Hydrol Earth Syst Sci,2016,20(3):1269-1288.
[23]Zreda M,Zeng X,Shuttleworth W J,et al.Cosmic-ray neutrons,an innovative method for measuring area-average soil moisture[J].Gewex News,2011,21(3):6-10.
[24]Desilets D,Zreda M.Footprint diameter for a cosmic-ray soil moisture probe:Theory and Monte Carlo simulations[J].Water Resour Res,2013,49(6):3566-3575.
[25]Desilets D,Zreda M.Spatial and temporal distribution of secondary cosmic-ray nucleon intensities and applications to in-situ cosmogenic dating[J].Earth Planet Sci Lett,2003,206(1):21-42.
[26]Zhu Z,Tan L,Gao S,et al.Observation on soil moisture of irrigation cropland by cosmic-ray probe[J].IEEE Geoscience and Remote Sensing Letters.2014,12(3):472-476.
[27]徐宗学,张玲,阮本清.北京地区降水量时空分布规律分析[J].干旱区地理,2006,29(2):186-192.Xu Zongxue,Zhang Ling,Ruan Benqing.Analysis on the spatiotemporal distribution of precipitation in the Beijing region[J].Arid Land Geography,2006,29(2):186-192.(in Chinese with English abstract)
[28]廖俊辉,谢一冈,陈元柏,等.用于热中子探测的正比管性能研究[J].核电子学与探测技术,2007,27(2):367-371.Liao Junhui,Xie Yigang,Chen Yuanbai,et al.Research on the proportional pipe performance for thermal neutron detection[J].Nuclear Electronics&Detection Technology,2007,27(2):367-371.(in Chinese with English abstract)
[29]Glenn F Knoll.Radiation Detection and Measurement[M].US:Wiley,2000.
[2]刘志明,张柏,晏明,等.土壤水分与干旱遥感研究的进展与趋势[J].地球科学进展,2003,18(4):576-583.Liu Zhiming,Zhang Bai,Yan Ming,et al.Some research advances and trends on soil moisture and drought monitoring by remote sensing[J].Advance Earth Sciences,2003,18(4):576-583.(in Chinese with English abstract)
[3]邓英春,许永辉.土壤水分测量方法研究综述[J].水文,2007,27(4):20-24.Deng Yingchun,Xu Yonghui.A review of soil moisture measurement methods[J].Hydrology,2007,27(4):20-24.(in Chinese with English abstract)
[4]李琴,陈曦,Frank Veroustraete,等.干旱半干旱区土壤含水量反演与验证[J].水科学进展,2010,21(2):201-207.Li Qin,Chen Xi,Frank V,et al.Validation of soil moisture retrieval in arid and semi-arid areas.Advances in water science,2010,21(2):201-207.(in Chinese with English abstract)
[5]Zreda M,Desilets D,FerréT P A,et al.Measuring soil moisture content non-invasively at intermediate spatial scale using cosmic-ray neutrons[J].Geophys Res Lett,2008,35(21).DOI:10.1029/2008GL035655.
[6]Desilets D,Zreda M,FerréT P A.Nature’s neutron probe:Land surface hydrology at an elusive scale with cosmic rays[J].Water Resour Res,2010,46(11).DOI:10.1029/2009WR008726.
[7]Franz T E,Zreda M,FerréT P A,et al.Measurement depth of the cosmic-ray soil moisture probe affected by hydrogen from various sources[J].Water Resour Res,2012,48(8):1-9.
[8]Hess W N,Patterson H W,Wallace R,et al.Cosmic-ray neutron Energy Spectrum[J].Phys Rev,1959,116(2):445-447.
[9]Kodama M,Nakai K,Kawasaki S,et al:An application of cosmic-ray neutron measurements to the determination of the snow-water equivalent[J].Journal of Hydrology,1979,41(1):85-92.
[10]Franz T E,Zreda M,Rosolem R,et al.A universal calibration function for determination of soil moisture with cosmic-ray neutrons[J].Hydrol Earth Syst Sci,2013,17(12):453-460.
[11]Zreda,M,Shuttleworth,W J,Zeng X,et al.COSMOS:the cosmic-ray soil moisture observing system[J].Hydrol Earth Syst Sci Discuss,2012,9(4):4505-4551.
[12]Rivera Villarryes C A,Baroni G,Oswald S E.Integral quantification of seasonal soil moisture changes in farmland by cosmic-ray neutrons[J].Hydrol Earth Syst Sci,2011,15(12):3843-3859.
[13]Rivera Villarryes,C A,Baroni G,Oswald S E.Calibration approaches of cosmic-ray neutron sensing for soil moisture measurement in cropped fields[J].Hydrol Earth Syst Sci,2013,10(4):4237-4274.
[14]Rosolem R,Shuttleworth W J,Zreda M,et al.The effect of atmospheric water vapor on neutron count in the cosmic-ray soil moisture observing system[J].Journal of Hydrology,2013,14(5):1659-1671.
[15]Chrisman B,Zreda M.Quantifying mesoscale soil moisture with the cosmic-ray rover[J].Hydrol Earth Syst Sci Discuss,2013,10(6):7127-7160.
[16]Almeida A C,Dutta R,Franz T E,et al.Combining cosmic-ray neutron and capacitance sensors and fuzzy inference to spatially quantify soil moisture distribution[J].Sensors Journal IEEE,2014,14(10):3465-3472.
[17]Baroni G,Oswald S E.A scaling approach for the assessment of biomass changes and rainfall interception using cosmic-ray neutron sensing[J].Journal of Hydrology,2015,525:264-276.
[18]焦其顺,朱忠礼,刘绍民,等.宇宙射线快中子法在农田土壤水分测量中的研究与应用[J].地球科学进展,2013,28(10):1136-1143.Jiao Qishun,Zhu Zhongli,Liu Shaomin,et al.Research and application of cosmic-ray fast neutron method to measure soil moisture in the field[J].Advances in Earth Science,2013,28(10):1136-1143.(in Chinese with English abstract)
[19]贾晓俊,施生锦,黄彬香,等.宇宙射线中子法测量土壤水分的原理及应用[J].中国农学通报,2014,30(21):113—117.Jia Xiaojun,Shi Shengjin,Huang Binxiang,et al.Principles and application of cosmic-ray neutron method for measuring soil moisture[J].Chinese Agricultural Science Bulletin,2014,30(21):113-117.(in Chinese with English abstract)
[20]赵纯,袁国富,刘晓,等.宇宙射线土壤水分观测方法在黄土高原草地植被的应用[J].土壤学报,2015,52(6):1438-1444.Zhao Chun,Yuan Guofu,Liu Xiao,et al.Application of cosmic-ray method to soil moisture measurement to grassland in the loess plateau[J].Acta Pedologica Sinica,2015,52(6):1438-1444.(in Chinese with English abstract)
[21]王秋铭,王胜,樊军.宇宙射线快中子法在土壤水分测量中的应用:以陕北六道沟流域为例[J].中国水土保持科学,2015,13(5):125-131.Wang Qiuming,Wang Sheng,Fan Jun.Application of cosmic-ray fast neutron method to measure soil moisture:A case study of Liudaogou basin in Shanxi[J].Science of Soil and Water Conservation,2015,13(5):125-131.(in Chinese with English abstract)
[22]Ingo Heidbüchel,Andreas Güntner,Theresa Blume.Use of cosmic-ray neutron sensors for soil moisture monitoring in forests[J].Hydrol Earth Syst Sci,2016,20(3):1269-1288.
[23]Zreda M,Zeng X,Shuttleworth W J,et al.Cosmic-ray neutrons,an innovative method for measuring area-average soil moisture[J].Gewex News,2011,21(3):6-10.
[24]Desilets D,Zreda M.Footprint diameter for a cosmic-ray soil moisture probe:Theory and Monte Carlo simulations[J].Water Resour Res,2013,49(6):3566-3575.
[25]Desilets D,Zreda M.Spatial and temporal distribution of secondary cosmic-ray nucleon intensities and applications to in-situ cosmogenic dating[J].Earth Planet Sci Lett,2003,206(1):21-42.
[26]Zhu Z,Tan L,Gao S,et al.Observation on soil moisture of irrigation cropland by cosmic-ray probe[J].IEEE Geoscience and Remote Sensing Letters.2014,12(3):472-476.
[27]徐宗学,张玲,阮本清.北京地区降水量时空分布规律分析[J].干旱区地理,2006,29(2):186-192.Xu Zongxue,Zhang Ling,Ruan Benqing.Analysis on the spatiotemporal distribution of precipitation in the Beijing region[J].Arid Land Geography,2006,29(2):186-192.(in Chinese with English abstract)
[28]廖俊辉,谢一冈,陈元柏,等.用于热中子探测的正比管性能研究[J].核电子学与探测技术,2007,27(2):367-371.Liao Junhui,Xie Yigang,Chen Yuanbai,et al.Research on the proportional pipe performance for thermal neutron detection[J].Nuclear Electronics&Detection Technology,2007,27(2):367-371.(in Chinese with English abstract)
[29]Glenn F Knoll.Radiation Detection and Measurement[M].US:Wiley,2000.