In-situ soil nitrate ion concentration sensor
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 (NO 3 − ) concentrations. The transflection dip probe may be read with spectrometer with an input deuterium light source.
1. An in-situ ion measurement system, comprising:
a tube, said tube having a distal end;
wherein the distal end of said tube comprises a porous section; and
wherein the porous section comprises pores sized to allow diffusion and bulk fluid flow of a soil solution therethrough to form a measurement solution;
a probe body having a central bore, said probe body coaxial with said tube; and
a probe placed within the central bore of the probe body, wherein a sensitive portion of the probe measures at least one characteristic of the measurement solution.
2. The in-situ ion measurement system as recited in claim 1 , wherein the probe is an Ion Selective Probe.
3. The in-situ ion measurement system as recited in claim 1 , wherein the probe is a nitrate Ion Selective Probe.
4. The in-situ ion measurement system as recited in claim 1 , wherein the probe is an optical probe.
5. The in-situ ion measurement system as recited in claim 4 , wherein the probe is a transflection dip probe.
6. The in-situ ion measurement system as recited in claim 5 , wherein the transflection dip probe allows absorption of an input light source as the input light passes through the measurement solution into an output signal.
7. The in-situ ion measurement system as recited in claim 4 , further comprising:
a deuterium light source that provides an input light source;
an optical spectrometer that measures an output signal from the passage of the input light source through the measurement solution.
8. The in-situ ion measurement system as recited in claim 7 , further comprising:
a computer that controls a collection of in-situ measurements through the spectrometer.
9. The in-situ ion measurement system as recited in claim 8 , further comprising:
a program executable on the computer, capable of performing steps comprising:
collecting the in-situ measurements through the spectrometer,
wherein the in-situ measurements are ion concentration measurements.
10. The in-situ ion measurement system as recited in claim 8 , further comprising:
a program executable on the computer, capable of performing steps comprising:
collecting the in-situ measurements through the spectrometer,
wherein the in-situ measurements are nitrate ion concentration measurements.
11. The in-situ ion measurement system as recited in claim 8 , further comprising:
a program executable on the computer, capable of performing steps comprising:
collecting the in-situ measurements through the spectrometer,
wherein the in-situ measurements are measured on one or more components of BTEXS concentration measurements.
12. The in-situ ion measurement system as recited in claim 11 , wherein BTEXS comprises one or more of a contaminant selected from a group of contaminants consisting of: benzene, toluene, ethyl benzene, xylene, and styrene.
13. The in-situ ion measurement system as recited in claim 7 , further comprising:
a program executable on the computer, capable of performing steps comprising:
collecting the in-situ measurements through the spectrometer,
wherein the in-situ measurements are measured on one or more of a contaminant selected from a group of contaminants consisting of: a polychlorinated biphenyl, tetrachloroethylene, sulfur dioxide, arsenic, selenium, petroleum, petroleum distillates, petroleum byproducts, hydrocarbon, pentachlorophenol, creosote, a pesticide, a polycyclic aromatic hydrocarbon (PAH), a volatile organic carbon (VOC), a dioxin, a dibenzofuran, copper, lead, zinc, hexavalent chromium(VI), cadmium, and mercury.
14. The in-situ ion measurement system of claim 1 , wherein the porous section comprises a tubular section concentric with the tube.
15. The in-situ ion measurement system of claim 1 , wherein the porous section has the same inner and outer diameter as a reservoir cup that terminates in a conical section.
16. An in-situ measurement system, comprising:
a tube, said tube having a distal end;
wherein the distal end of said tube comprises a porous section; and
wherein the porous section comprises pores sized to allow diffusion and bulk fluid flow therethrough;
a probe body having a central bore;
wherein said probe body is coaxial with said tube;
a solution in material surrounding the probe body that diffuses and flows through the porous section to produce a measurement solution;
a probe placed within the central bore of the probe body, wherein a sensor portion of the probe measures at least one characteristic of the measurement solution; and
a computer that controls a collection of in-situ measurements from the sensor portion of the probe.
17. The in-situ measurement system as recited in claim 16 , wherein the probe comprises an Ion Selective Electrode probe.
18. The in-situ measurement system as recited in claim 16 , wherein the probe comprises a transflection dip probe.
19. The in-situ measurement system as recited in claim 18 , wherein the transflection dip probe is capable of measuring absorbance in the range of 200 nm through 1100 nm.
20. The in-situ measurement system as recited in claim 18 , wherein the transflection dip probe is capable of measuring absorbance in the range of 235 nm through 240 nm.
21. The in-situ measurement system as recited in claim 18 , wherein the transflection dip probe is capable of measuring solution absorbance at one or more of the wavelengths selected from the group of wavelengths consisting of: 235 nm, 238 nm, and 240 nm.
22. An in-situ ion measurement system, comprising:
a tube, said tube having a distal end;
wherein the distal end of said tube comprises a porous section; and
wherein the porous section comprises pores sized to allow diffusion and bulk fluid flow therethrough;
an in-situ probe body having a central bore;
wherein said probe body is coaxial with said tube;
a soil solution in soil surrounding the probe body wherein the soil solution diffuses and flows through the porous section to form a measurement solution; and
a probe placed within the central bore of the probe body, wherein a sensitive portion of the probe measures at least one characteristic of the measurement solution.
23. The in-situ ion measurement system of claim 22 , further comprising:
a deuterium light source, wherein the deuterium light source provides illumination to the sensitive portion of the probe.
24. The in-situ measurement system of claim 22 , further comprising:
a spectrometer, wherein the spectrometer provides measurement solution absorption spectra to a computer.
25. The in-situ measurement system of claim 22 , further comprising:
a displacement attachment situated on the probe;
wherein the probe is an optical probe, said optical probe having a bottom; and
wherein the displacement attachment protrudes from the bottom of the optical probe;
whereby the optical probe senses the measurement solution.
26. The in-situ measurement system of claim 22 , further comprising:
a plano-convex lens that transmits a deuterium light source from an illumination source fiber to a mirror through the measurement solution; and
a returning signal fiber disposed to collect the light reflected through the measurement solution from the mirror and focused by the plano-convex lens.
27. The in-situ measurement system of claim 22 , wherein the probe is removable.