DE102006031800A1 - Pollutants e.g. inorganic and/or organic compounds, monitoring method, involves processing number of neutrons by microprocessor, from which type and quantity of pollutants are determined, after being conveyed to computer after digitization - Google Patents

Abstract

The method involves illuminating a soil and/or liquid medium with fast neutrons of high energy from an artificial neutron source (7) of a stationary probe (3). The neutrons are decelerated and captured by pollutants e.g. inorganic and/or organic compounds. The number of thermal neutrons is registered and conveyed to a computer (14) after digitization, and is processed by a microprocessor, from which type and quantity of the pollutants are continuously determined. An alarm (15) for intervention is released, when a determined value exceeds a permissible limit value. An independent claim is also included for a device for continuous monitoring of pollutants in a soil and/or liquid medium.

Description

The The invention relates to a method for monitoring pollutants in soils and / or liquid media, especially simultaneous monitoring a variety of chemical elements, inorganic and / or organic compounds in soil and / or liquid media in which the Type and amount of pollutant determined on site in situ and is displayed.

The The invention further relates to a device for monitoring pollutants in soils and / or liquid Media, in particular simultaneous monitoring a variety of chemical elements, inorganic or organic Compounds in the soil and / or liquid media, with an artificial Neutron source for irradiating the soil and / or the medium with a controlled source energy.

State of the art

For the detection of pollutants, it is known to use sensors with material-detecting elements and transducers, which converts the information about the presence and concentration of defined chemical compounds in the medium to be measured into an electrical signal (see SCHAUMBURG, "Sensors", p. 380-452, BG Teubner Stuttgart 1992 ). The substances to be measured are recorded either selectively or in summary.

This Prior art is unable to handle a variety of pollutants in the soil or in standing or flowing waters simultaneously continuously to detect, quantify and display on-site.

The use of artificial neutron sources for the purpose of quantitatively determining the presence of hydrocarbon oil or salt water in an earth formation penetrated by a borehole is known from US Pat DE 2 210 550 known. However, this prior art operates with a proportional gamma ray detector having a predetermined material which traps passing thermal neutrons.

This known prior art has the disadvantage that a secondary reaction is used and sufficient material for such reactions available have to be.

From the DE 36 10 800 A1 Further, there is known a method for measuring earth formation properties in which the earth formation is repeatedly irradiated with pulses of neutrons and the gamma rays emanating from the earth formation are detected, the cumulative counts for each pulse defining points on a cumulative count versus time curve that has a mathematical expression.

The Properties of the earth formation become from the cumulative counting windows by calculating the variables in the mathematical expression. This means that in this prior art, a cumulative count instead of the count rate curve is used to determine the formation properties.

A such measurement methodology leads to the disadvantage that ultimately only summative effects are detected can.

at In this prior art, the object of the invention is to provide a method of the type mentioned above available capable of producing waters and / or soil simultaneously on contaminations or impurities of any kind with high To monitor accuracy and a comprehensive assessment of the soil and / or waters Place in a short time and cost-effective make.

task

These Task is by a method of the type mentioned with the characterizing features of claim 1 and by a Device solved with the features of claim 8.

advantageous Embodiments of the method and the device are the dependent claims.

With the solution according to the invention is For the first time, an in-situ process is available with which pollutants different type and amount in the ground or in the standing or flowing waters continuously over a longer one Period can be measured and displayed. The inventive method can easily be under or over the day Use come.

A some kind of fixation on certain elements or connections, as it always occurs in biochemical sensors, completely eliminated. With the method according to the invention This will provide a comprehensive, objective burden assessment of Substrates, Rivers, wastewater or other liquids but also the location of foreign bodies possible in the ground.

The inventive method needed just a simple device configuration, which is essentially a modular probe with a fast Neutron source of about 14 MeV, neutron detectors, a power supply, includes a control board and a microprocessor with memory, the above a supply line is connected to a computer, with which all necessary parameters, such as the accumulation time, the Start time, the number of single readings and the monitoring period (Monitoring period) are adjustable.

The inventive method can be designed so that, for example, a pollutant component automatically monitored in the wastewater and when crossing a previously set limit concentration alarm or triggered also a general alarm version is driven.

During the monitoring operation works the inventive method completely self-sufficient. It leaves easily with further monitoring units network, so that correspondingly large areas or areas according to different Element groups or connections can be monitored.

The inventive method places no special demands on the measuring conditions. It must ultimately only enough There may be room to configure the device into the medium to be controlled.

The inventive method achieved as well an extremely high one Economy, especially expensive Sampling for chemical or mass spectroscopic analyzes can be omitted.

The inventive method also allows the degree of automation, for example, in the wastewater monitoring significantly increase.

Further Advantages and details will become apparent from the following description with reference to the attached Drawings.

embodiments

The Invention will be explained in more detail below with reference to two embodiments.

It shows

1 a representation of the device according to the invention, which realizes the pulse neutron neutron measurement,

2 a cross-linking variant of monitoring devices according to the invention,

3 the exemplary presentation of decay curves from a surface water,

4 the decay curves of a test specimen at different distances,

5 the proof of the test body with count rates in selected registration windows 4 .

6 the representation of the benzene concentration as a function for selected registration windows and

7 the calibration of the decay curves based on chemical analysis values.

With the in the 1 and 2 illustrated monitoring device according to the invention 1 should be in a first embodiment of a buried in 6 m depth foreign body 2 , For example, of iron, be detected.

In a second embodiment should with the inventive method displayed and monitored the Benzengehalt in a groundwater measuring station become.

The monitoring device 1 consists of a probe 3 according to a configuration suitable for the respective purpose, a control device 4 with storage and transfer function and a power supply 5 , The probe 3 is with the control device 4 through a cable 6 connected. The control device 4 has at least one interface for connecting a computer having an interface and a microprocessor card 14 on which made the necessary settings and the corresponding of the probe 3 supplied data.

The probe 3 is modular and has an artificial neutron source 7 with a source energy of about 14 MeV. This neutron source 7 is characterized by the fact that it can emit a high neutron flux per shot, has a fixed neutron output energy, has a controllable source energy and only controlled causes radioactive contamination. At low firing frequency, the source emits high neutron radiation.

The probe 3 is two-channel, ie it comprises two neutron detectors 8th and 9 and a detector 8th and a detector 9 , where the detector 8th opposite the detector 9 has a lower effectiveness. These detectors 8th and 9 register the decay time of the neutrons interacting with the environment (soil or liquid medium) and thus capture all effects during the lifetime of a single neutron via the thermal neutron distribution. Complete decay curves of the thermal neurons interacting with the environment are always recorded by counting the pulses.

To the probe 3 further includes a power supply 10 for the probe operation, a modem 11 for data transmission to the control unit, a control board 12 for the operating regime and a microprocessor 13 with memory for data.

For signal transmission from the probe 3 to the control device 4 a special data format is used. This ensures that a loss-free counting of the pulses is guaranteed. This also applies to the length of the counting window, which must be above the dead time of the system to be detected. Deadtime defines the period of regeneration of the system to record the next data cycle.

The 2 shows the construction of a decentralized network of several separate monitoring devices 1 , for example, from a Überlägig arranged in a stagnant water monitor 1.1 , a monitoring device positioned overflowing in a flowing water body 1.2 , a monitoring facility located underground in the vicinity of the ground 1.3 and a downhole downhole monitoring device 1.4 to a surveillance network 16 composed. Thus, the inventive method can be easily integrated into existing structures, be it in industrial processes, agriculture, road construction, etc. to monitoring tasks.

The measuring sequences are controlled by a relatively simple operating software, which via the connected computer 14 is read. All necessary parameters such as the monitoring period, the accumulation time, ie signal recording time, the start time, the number of single readings per accumulation time can be set.

The calculator contains comparative profiles for soils to be monitored and / or liquid media, river courses, sewers, etc., which contain the permissible contamination limits, so that if these values are exceeded an alarm is triggered by an alarm device 15 or triggering control commands that interfere with or influence the process.

τ

die Neutronenlebenszeit in μs

No

die Zählraten zu Beginn eines ausgewählten Zeitintervalls Τ

N

die Zählraten am Ende des ausgewählten Zeitintervalls.

The 3 shows exemplary decay curves of thermal neutrons from a surface water. These decay curves can be described with the following equations: τ = ΔΤ / lnN O - lnN / μs / (1) N = N O e -Τ / τ (2) in which mean:

τ

the neutron lifetime in μs

No

the count rates at the beginning of a selected time interval Τ

N

the count rates at the end of the selected time interval.

a, b, d

partielle Faktoren für das untersuchte Medium

c, e

Proportionalitätsfaktoren für Effekte aus dem Bohrloch und der Formation.

The cumulative count rates can be described as the sum of neutrons of different origin: N = a + b / 1 -exp (-cΤ) / + d / 1 -exp (-eΤ) / (3), in which mean:

a, b, d

partial factors for the investigated medium

c, e

Proportionality factors for borehole and formation effects.

The Factors a, b and d are strongly dependent on the probe geometry certainly. The equations show no dependencies on geometric Factors. For a two-channel device, as in the execution of the inventive method must be used both channels generally respond in the same way, however, will become change a, b and d, because they depend on the particular probe.

The Equations (1) to (3) average the effects of neutron reactions of the following type:

1. neutron capture (n, γ)

Of the Neutron capture is the main reaction for the deceleration of neutrons in the energy range between E = 0 ... 500 keV.

2nd pairing

At the In the impulse neutron neutron method, the pairing (n, 2n) is an important reaction. For one Neutron source with an energy of 14 MeV, as in the method according to the invention is used, Be and Cu tend to be very typical for this reaction.

3. neutron scattering (n, n ')

These Reaction represents the main process for the energy losses of neutrons to the thermal level, i. until their thermal equilibrium with the surrounding medium.

The following table shows characteristic capture cross sections for some selected materials: material Trapping cross section per unit volume [10 ²¹ Barns / cm ³ ] lead 5.21 iron 214.9 arsenopyrite 165.22 quartz 4.36 graphite 0.38 Halit 752.36 Pure water 22.08 oil 28,02 methane 0.028

Other capture cross sections are from the publication "Nuclear physical constants" (russ.), Publishing house gas atom 1963 refer to.

For monitoring of elements and / or compounds in the soil or liquid media according to the inventive method become mainly the braking reactions of the neutrons and the neutron scattering used. The braking reaction determines the length and the course of the decay curve and the neutron scattering the diffusion length, the the neutron overcomes, until it is captured. This leaves the place where that searched element occupies its place on the decay curve, specifically determine.

The Elements are based on plateaus in the decay curve and their Time assignment determined and the amplitude provides output values for concentration data.

In carrying out the method according to the invention, the pulses from the neutron detectors 8th and 9 registered, converted into digital signals, in the microprocessor 13 preprocessed and as count rates in the memory of the microprocessor 13 the probe 3 stored. About the modem 11 the stored signals in a special data format to the receiving part of the control device 4 transfer the data to the computer 14 for further processing.

to Minimization of statistical variations in the registration of counts is it going? Measuring process a sufficiently long time. There are measuring times every 2 minutes proved to be perfectly adequate. During this Time, for example, 10 data blocks are recorded and by the Calculator read.

The Processing of the data is done in a known manner, statistically adjusted values from the summation of block values and the formation of averages.

Out the determined values are then linear and semilogarithmic Abklingkurven constructed, the block values by means of "sliding window technique "additionally filtered become. For this purpose, different averaging intervals are used and related to the subsequent intervals.

These Edits are done both for measured count rates as well as from their quotients, whereby the quotients are chosen arbitrarily and an iterative approximation is used as a criterion.

After this the decay curves are present, the determination of the elements takes place and / or compounds, as further described by the following examples becomes.

example 1

A test body 2 made of iron, which simulates a mine, for example, was buried in the ground at a depth of 6 m.

In the meter distance holes were drilled, in which the probe 3 the monitoring device 1 for measuring by the method according to the invention was introduced.

The previously described decay curves were corresponding from the registered counts constructed.

The 4 shows the decay curves as a function of the registration window, which clearly group among others in the registration windows 10 and 20 or 30 and 45 and the influence of the test body 2 signal the strongest.

In 5 the proof of the test body is shown. It can clearly be seen that an increase in the count rates for measurements below the water level for the registration windows 10 and 20 at 5.2 m and for the registration window 30 and 45 at 6.8 m distance to the test body results. The test body is thus clearly detected.

Of the Increase in the decay curves gives a signal value of 230 c.u., the value for Iron corresponds.

Example 2:

In a borehole, the benzene content should be detected and controlled. The probe 3 the monitoring device 1 is brought into the well and connected via the cable with the latter. Naturally it is also possible to arrange the probe in flowing water. Samples were taken at individual test points and count rates were recorded at the same time and both are then compiled as a functional dependency. The graphic is used for calibration.

As soon as the calculator 14 detects exceeding the limit of benzene in the water, the latter solves an alarm by the alarm device 15 to intervene in the process.

1, 1.1, 1.2, 1.3, 1.4

monitoring device

2

foreign body

3

probe

4

control device

5

Power supply to the probe 3

6

electric wire

7

neutron source

8th, 9

neutron detectors

10

Power supply of 4

11

modem

12

control board

13

Microprocessor in 3

14

Calculator of 4

15

alarm device

16

network

Claims (14)

Method for monitoring pollutants in the soil and / or liquid media, in particular simultaneous monitoring of a plurality of chemical elements, inorganic and / or organic compounds, in which the type and amount of pollutant is determined in situ and displayed in situ, characterized characterized in that the soil and / or the liquid media are pulsed with high energy fast neutrons from an artificial neutron source and interact with the elements and / or compounds, the fast neutrons slowing down to the thermal energy range and the elements to be detected and / or compounds are detected, wherein the number of thermal neutrons registered, then fed to a computer after digitization and then processed by the latter to a decay curve, from which determines the type and amount of elements and / or compounds continuously, the thus determined Value with compared to a permissible limit value and an alarm is triggered when the limit value is exceeded. Method according to claim 1, characterized in that that the resulting distribution of thermal neutrons as Decay curve over the entire lifetime of the total of thermal neutrons below execution following steps for detection, to display the chemical elements and / or connections and to trigger control commands when crossing one for the soil and / or medium predetermined limit concentration used becomes: a) Detecting all interactions between neutrons and environment during the lifetime of a single neutron; b) Setting a Length of one Counting interval ΔΤ above a dead time of the system; c) Evaluation of the step after a) determined decay curves by dividing the curve into contiguous registration windows, where the count rates in every single or selected one Window by counting be determined and recorded d) determining the type of element and / or the connection on the decay curve by associating the determined count rates in the individual windows to from for the individual elements or Compounds present characteristic capture cross-sections for thermal neutrons e) determining the amount of the element and / or the Connection from the height the recorded count rate or the location on the decay curve. Method according to Claims 1 and 2, characterized that instead of counting rates the quotient of the count rates used to evaluate the decay curves. A method according to claim 1 and 2, characterized in that the suitable for evaluation Re be determined by an analysis of the decay curves, in particular with regard to their position to each other or their displacement. Method according to Claims 1 to 4, characterized that the decay curves are calibrated using chemical analysis values become. Method according to Claims 1 to 4, characterized that with the highest sensitivity determined registration window for the quantitative determination of organic Compounds is used. Method according to claim 1, characterized in that that several, in different floor areas and / or riverbeds misplaced neutron sources together to a decentralized Network be summarized. Apparatus for the continuous monitoring of pollutants in soils and / or liquid media, in particular simultaneous monitoring of a multiplicity of chemical elements, inorganic and / or organic compounds in the soil and / or liquid media, for carrying out the method according to claim 1, characterized in that stationary probe ( 3 ) with a fast neutron source ( 7 ) high energy for pulsed irradiation of the soil and / or liquid medium and with neutron detectors ( 8th . 9 ) is arranged for registering with the elements and / or compounds in the soil and / or medium interacting thermal neutrons in or on the ground or in the liquid medium, wherein in the probe ( 3 ) a microprocessor ( 13 ) for preprocessing the registered count rates and their temporary storage, a power supply ( 5 ) and a modem ( 11 ) for transferring a special data format to a computer ( 14 ) comprehensive external control equipment ( 4 ) provided with an alarm device ( 15 ) connected is. Device according to claim 8, characterized in that the probe ( 3 ) is formed at least two channels. Device according to claims 8 and 9, characterized that the probe for laying submersible or in liquids liquid- and pressure-tight. Apparatus according to claim 8, characterized in that the neutron source ( 7 ) has a source energy of up to 14 MeV. Device according to claim 8, characterized in that the detectors ( 8th . 9 ) respond to thermal neutrons. Device according to claim 8, characterized in that the probe ( 3 ) with the monitoring device ( 4 ) is connected by a cable up to 1000 m long. Apparatus according to claim 8 to 13, characterized in that a plurality of, in different floor areas and / or fluid areas routed probes ( 3 ) a decentralized network ( 16 ) to monitor a region.