In-situ soil nitrate ion concentration sensor

• US 7,927,883 B2
• Filed: 11/10/2008
• Issued: 04/19/2011
• Est. Priority Date: 11/09/2007
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Hopmans, Jan W., Shaw, Benjamin D., Kamai, Tamir, Tuli, Atac
• Primary Examiner(s): Soderquist; Arlen
• Application Number:
  US12/267,895
• Publication Number:
  US 20090166520A1
• Time in Patent Office: 890 Days
• Field of Search: 422 8201- 8209, 436/25, 436/28, 436/110, 436149-151, 436/164, 436171-172
• US Class Current: 436/110
• CPC Class Codes: G01N 2033/245 for agricultural purposes
• CPC Class Codes: G01V 9/00 Prospecting or detecting by methods not provided for in groups G01V1/00 - G01V8/00
• CPC Class Codes: Y10T 436/173076 Nitrite or nitrate
• CPC Class Codes: Y10T 436/25375 Liberation or purification of sample or separation of material from a sample [e.g., filtering, centrifuging, etc.]

Abstract

A method and apparatus for near real-time in-situ soil solution measurements is presented. An outer sleeve is placed in soil where ionic concentrations of organic or inorganic species are to be measured. A porous section connects with the outer sleeve (the porous section initially loaded with distilled water) equilibrates with the solution present in soil pores to form a solution to be measured. The initial distilled water is displaced within the porous section by a removable plunger. After substantial equilibration of the solution to be measured within the apparatus, the plunger is removed and a removable probe replaced. The probe may be an Ion Selective Electrode, or a transflection dip probe. The probe then may be used under computer control for measurement of solution properties. The Ion Selective Electrode may measure nitrate (NO₃⁻) concentrations. The transflection dip probe may be read with spectrometer with an input deuterium light source.

Claims

1. A method of in-situ measurement of solution ion measurement in soil, comprising:

placing a measurement system, comprising an outer tube sleeve, into a soil that is to be measured, wherein the distal section of the outer tube sleeve comprises a porous section;

initially contacting a quantity of distilled water with the porous section;

allowing the quantity of distilled water to equilibrate with a soil solution to be measured, through the porous section, so as to equilibrate into a solution to be measured;

contacting the solution to be measured with a probe;

measuring the solution to be measured with the probe;

inserting a plunger into the outer tube sleeve, thereby contacting the distilled water with the porous section; and

after the solution equilibrates; and

replacing the plunger with the probe.

2. The method of in-situ measurement of solution ion measurement in soil of claim 1, wherein the probe is selected from a group of probes consisting of:

an Ion Selective Electrode probe, and a transflection dip probe.

3. The method of in-situ measurement of solution ion measurement in soil of claim 2, wherein the Ion Selective Electrode probe is a nitrate Ion Selective Electrode probe.

4. The method of in-situ measurement of solution ion measurement in soil of claim 2, wherein the transflection dip probe is capable of measuring absorbance in the range of 235 nm to 240 nm.

5. The method of in-situ measurement of solution ion measurement in soil of claim 4, wherein the transflection dip probe measures absorbance at one or more of the wavelengths selected from the group of wavelengths consisting of:

235 nm, 238 nm, and 240 nm.