土壤与地下水污染防治soilandgroundwaterpollution课件

1、Colorimetric test Kits Fiber Optic Chemical SensorsGas Chromatography Graphite Furnace Atomic Absorption SpectroscopyImmunoassay Infrared Spectroscopy Laser-Induced Fluorescence Mass Spectrometry X-Ray FluorescenceField characterization technologies土壤與地下水污染防治(Soil and Groundwater Pollution Control)S

2、ource: /ord/SITE/ Colorimetric test Kits Field cColorimetric test Kits Test kits are self-contained analytical kits that use a chemical reaction that produces color to identify contaminants, both qualitatively and quantitatively. Wide applications- from simple colorimetric indicator tubes for health

3、 and safety monitoring to quantitative testing for definitive site characterization. Also, after the initial site characterization phase to monitor the operating conditions of a remediation system or to confirm that contaminated soils have been removed. Colorimetric test Kits Test kiAdvantagesSpeedP

4、ortabilityEase of useLow cost per sampleAdvantagesSpeedSome innovative technologiesKit nameContaminatesMedium matrixRange and DL*The Hanby field test kitPetroleum and constituents (gasoline, diesel fuel, jet fuel, crude oil, BTEX, PAHs, PCBsWater and soilSoil 1-1000 mg/kgWater 0.1-20 mg/LThe Clor-N-

5、Oil and Clor-N-Soil KitsPCBsOil, soil, or surface wipe samplesClor-N-Oil kit at 20, 50, 100, or 500 ppm Aroclor 1242Clor-N-Soil kit at 50 ppm Aroclor 1242The PetroFLAGGasoline, diesel fuel, jet fuel, fuel oil, motor oil, transformer oil, hydraulic fluid, greases, and many other types of hydrocarbons

6、soilCommon 20-2000 ppmJet fuel 200-2000 ppmWeathered gasoline 400-2000 ppmThe AccuSensorTCE, total THM (chloroform, bromodichloromethane, chlorodibromomethane, bromoform), BTEX, and PCEWaterTCE 5ppbTHM 10 ppbThe Envifrol Quick Test PCP, TNT, PAHsSoil or water (PCP only)PCP 1.5-90 ppmTNT 3-100 ppmPAH

7、s 1-3000 ppmDL= detection limitsSome innovative technologiesKMoreKit nameCosts, US$LimitationsThe deviceThe Hanby field test kit$17/testNot capable of distinguishing different hydrocarbon fractions in mixture samplesThe Clor-N-Oil and Clor-N-Soil KitsNot availableFalse positive due to other chlorina

8、ted organicsThe PetroFLAG$10-15/testFalse positive due to natural occurring waxes and oil; good for known hydrocarbonsThe AccuSensor$35/testChloroform would result in the TCE measurement error up to 40%The Envirol Quick Test $40/testTCP, TeCP can interference the resultsMoreKit nameCosts, US$Limitat

9、iMode of operation IHanby Field test kit (petroleum)weighing five grams of soil sample, placing it into a beaker, adding an ampoule of solvent to the soil, and stirring the sample for approximately two minutes to extract the contaminant. The extract then is poured from the beaker into a marked test

10、tube, and the catalyst is added to the test tube. The mixture is shaken for two minutes while the color change develops. The developed color of the precipitate is compared with a calibration photograph to obtain quantitative results. The water test is performed in the same manner, with the exception

11、 that a 500-milliliter (ml) water sample is extracted with solvent in a 500 ml separatory funnel, which is included in the water test kit. The procedure takes approximately 10 minutesDexsil Clor-N-Oil and Clor-N-Soil kit (PCBs)Several grams of sample are introduced into a vial that contains an ampou

12、le of organic solvent, and the PCBs are extracted from the sample medium with the solvent. The extract is treated with metallic sodium to strip chlorine from the biphenyl compound as chloride ions. An acidic buffer is added to the extract to quench any unreacted sodium and to transfer the chloride i

13、ons into the aqueous phase. Finally, chloride ions are measured colorimetrically by an indicator solution that creates a purple or yellow color depending on the presence of chloride ions. The purple color indicates the absence of chloride, and therefore the absence of PCBs, in the sample. A yellow o

14、r clear color indicates the presence of chloride, and therefore the presence of PCBs, in the sample. The procedure takes approximately 10 to 15 minutes. Mode of operation IHanby FieldExample- Hanby kit in screening TPHs in soil Example- Hanby kit in screeninMode of operation IIPetroFLAG (hydrocarbon

15、s)weighing 10 grams of soil by an electronic balance, placing the soil sample in a test tube, adding extraction solvent to the tube, shaking the tube intermittently for four minutes, filtering the extract into a vial that contains development solution, and allowing the solution to react for 10 minut

16、es. The filtration step is important because the analyzer measures the turbidity or optical density of the final solution. Approximately 25 samples can be analyzed per hour. The vial of developed solution is placed in the meter, and the instrument produces a quantitative reading that reveals the con

17、centration of hydrocarbons in the soil sample. AccuSensor (TCE/THM)a water sample is poured into a standard 40-ml volatile organic analysis (VOA) vial with an AccuSensor cap that has a Teflon membrane. The vial is shaken for 30 seconds to allow volatile compounds to partition into the headspace of t

18、he vial and reach equilibrium. The vial is inserted cap-first into the meter, exposing the gas phase in the headspace to the porous Teflon membrane. The volatile analytes in the headspace permeate the membrane and then encounter the reagent. The degree of absorbency is measured and the concentration

19、 is displayed in parts per billion (ppb). The concentration in the headspace, diffusion rate of the analyte, and reaction kinetics all are dependent on temperature. The AccuSensor meter incorporates a thermistor and software that provide automatic temperature compensation within an operating range o

20、f 0 to 50 degrees Centigrade. The procedure takes approximately five minutes. Mode of operation IIPetroFLAGMode of operation IIIEnvirol Quick Test (PCP)The Envirol Quick Test uses a photochemical reaction to produce a color proportional to the concentration of the analyte of interest. A small portab

21、le photometer called the Envirometer is used to measure the reaction. Three standards provided with each test kit are used to calibrate the Envirometer. The standard curve for the photochemical reaction is stored electronically in the unit. A calibration verification solution, also provided with eac

22、h test kit, is used to verify the calibration curve. A soil sample is weighed, extracted with a solvent, and then filtered. The single analyte test system entails using an organic solvent to extract the analytes from soil and employs various combinations of solid phase extraction (SPE), liquid-liqui

23、d extraction, and acid-base cleanup techniques to separate the analytes into an organic solvent. The extraction procedure used varies according to the specific test to be performed. Filtration helps to reduce interferences. The sample is placed in the Envirometer and the degree of absorbency of the

24、sample is measured and converted into a concentration of PCP, trinitrotoluene (TNT), or carcinogenic PAHs. The entire extraction and analysis procedure requires approximately 20 to 30 minutes.Mode of operation IIIEnvirol QFiber Optic Chemical Sensors (FOCS)Fiber Optic Chemical Sensors (Typical usage

25、sFOCS have primarily been developed to measure volatile petroleum constituents such as BTEX and chlorinated VOCs such as TCE, PCE, and carbon tetrachloride in water, air, or soil gas. The sensors have been developed to be placed down monitoring wells to provide in situ measurements of VOC concentrat

26、ions in groundwater. FOCS typically measure total VOC concentrations and are not capable of distinguishing individual volatile organic chemicals. With appropriate chemically selective layers, FOCS are capable of measuring SVOCs as well. Typical usagesFOCS have primarMode of operationLight is transmi

27、tted into the optical fiber from a light emitting diode (LED) and detected at the opposite end by a photodiode detector. A reference detector monitors the LED output and compensates for light source fluctuations. The amount of light transmitted to the detector is dependent upon the difference in ref

28、ractive index of the optical fiber core and the chemical coating. When the probe is immersed into water containing VOCs, the VOCs partition into the organophilic coating and change the effective refractive index of the coating allowing light to escape from the optical fiber. The resultant loss of li

29、ght reaching the detector correlates to the concentration of VOCs present. Mode of operationLight is tranAdvantagesThe design of intrinsic FOCS provides in situ and real time monitoring. FOCS are small in size due to small fiber optic diameters. Optical fibers are flexible within limits allowing gre

30、ater access to difficult locations. Transmission over long distances allow monitoring in deep wells and provide a measure of safety for monitoring of hazardous atmospheres. Multi-element analysis is possible using various fibers and a single central unit. AdvantagesThe design of intrinPerformance sp

31、ecificationsDetection Limits Typical detection limits are around 1 ppm for VOCs in water. Lower detection limits are possible with pre-concentration of the analyte. Calibration Calibration consists of measuring the response of the detector to a calibration standard. Calibration standards should cons

32、ist of a series of known analyte concentrations in a representative sample matrix. Detector response is plotted against analyte concentration to generate a calibration curve. As with most modern instrumentation, calibration and data acquisition is controlled and recorded with a microprocessor. Sampl

33、e Preparation FOCS are typically used for in situ measurements precluding sample preparation. Performance specificationsDeteLimitationsMany FOCS are not compound specific and will react to many VOCs and will produce a reading only for the concentration of total VOCs. The detection limits can be high

34、 compared with conventional analytical methods such as gas chromatography. FOCS are mainly used to detect gross contamination.Some sensors are temperature and time dependent. A temperature sensor can be added to the probe containing the FOCS to compensate for changes in temperature. Because sensor r

35、esponse is based on diffusion, the measured concentration may vary with time that the FOCS is in contact with the target analyte. Therefore, it is critical that equilibrium be achieved before a measurement is taken. Most FOCS reach equilibrium in 5 to 10 minutes which is indicated by a steady state

36、signal. The number of reversible reactions, that is adsorption and subsequent desorption, is limited, so probes may have to be regenerated after extended use.Dynamic ranges are usually lower than traditional electrodes which means that either the sample must be diluted or the sensor recalibrated. Li

37、mitationsMany FOCS are not cGas Chromatography Function of each partGas Chromatography Function ofTypical usesGas chromatography (GC) analysis is a widely used technique for field-based analysis. Analysis of organic compounds is possible for a variety of matrices such as water, soil, soil gas, and a

38、mbient air. Typical settings include:Site characterization Stationary source testing and monitoring Hazardous waste sites for determining personal protective equipment (PPE) level Fence line monitoring during removal or remediation activities Emergency response testing Typical usesGas chromatography

39、Commonly seen SW 846 methods need GCPhenols Method 8041 (GC-FID or ECD) Phthalates Method 8061A (GC-ECD) Amines Method 8070A (GC-NPD) Chlorinated pesticides Method 8081A (GC-ECD) PCBs Method 8082 (GC-ECD) PAHs Method 8100 (GC-FID) Chlorinated hydrocarbons Method 8121 (GC-ECD) Volatile organic chemic

40、als (VOC) Method 8240 Organophosphorus compounds Method 8141A (GC-NPD or FPD) Chlorinated herbicides Method 8151A (GC-ECD) MTBE Method 8260 (GC/MS) Halogenated VOC Method 8260B SVOCs/base neutral acids (BNA) Method 8270C (GC/MS) Dioxin Method 8280 (GC/MS) Commonly seen SW 846 methods nSeparation fac

41、torsStationary phase - An organic liquid compound that is either coated on or covalently bonded to the silica surface of a capillary column. Stationary phases are occasionally solids packed inside the column. The most widely used columns are the fused silica capillary columns due to strength and fle

42、xibility. The polarities of the compounds of interest dictate the choice of stationary phase, under the rule like dissolves like. Commonly used stationary phases include: (1) polydimethyl siloxane (referred to as OV-1 of SE-30) for PCB or PAH; (2) carbowax used for free acids, alcohols, and glycols;

43、 (3) OV-17 - for pesticides and glycols; (4) OV-210 - for chlorinated aromatics, nitroaromatics, and alkyl substituted benzenes; (5) OV-3 or SE-52 for halogenated organics. Carrier gas - The mobile phase is composed of an inert carrier gas, usually nitrogen, helium, or hydrogen. The choice of carrie

44、r gas is frequently determined by the type of detector used and subsequent purity requirements. The sample constituents are transformed into the gaseous phase and are carried along the column during separation. By increasing the speed (flow rate) of the carrier gas, the analysis time can be reduced;

45、 however, optimal resolution may be compromised. A faster flow rate also sweeps the injector more efficiently, improving introduction of the sample into the column. If resolution is not compromised, increased flow rates can also reduce analysis times. Length - Capillary columns vary in length from 1

46、5 to 100 meters is a coiled configuration to fit in the instrument oven. For environmental analysis, 30- to 60-meter columns typically are used. Shortening the length of the column can shorten the analysis time; however, resolution (separation) will be compromised. Again, if resolution is not compro

47、mised, analysis time can be reduced with a shorter column. Diameter - Diameters of open tubular capillary columns are typically between 0.32 and 0.25 millimeter, with high resolution columns having diameters of 0.20 to 0.15 millimeter. The smaller diameter columns require special injection splitting

48、 to reduce the sample size and prevent column overload. Columns referred to as mega bore open tube columns are also available and have a greater capacity but at the expense of resolution. However, these columns have better resolution than packed columns. Packed columns have diameters large as 2 mill

49、imeters. The smaller diameter produces better resolution and greater selectivity, but can handle only a small volume of sample (1 to 2 microliters). Column bleed- Another problem is column bleed. This phenomenon is best described as the elution of the stationary phase. A frequent cause of column ble

50、ed is excessive oven temperature. The end result of column bleed is a fouled detector. More sensitive detectors such ac electron capture detectors are highly susceptible to column bleed.Separation factorsStationary pPhotoionization Detector A photoionization detector (PID) consists of a special ultr

51、aviolet lamp, ranging in energy from 9.5 to 11.7 eV, mounted on a low-volume flow-through cell. As constituents of the sample pass through the cell, they are energized and ionized. The ions are collected at positively charged electrodes, where the change in current is measured. The 10.2 eV lamp emit

52、s ultraviolet light at 121 nanometers (nm), which is sufficient to ionize BTEX compounds and hexane. A few halogenated compounds that have ionization potentials of less than 11.7 eV can be detected by the higher-energy PID. The PID is more selective than the FID. The PID can detect VOCs (aromatic an

53、d chlorinated) and petroleum constituents including BTEX. The PID can detect BTEX in the low ppb to high part per trillion range. The PID is a nondestructive detector that can be used in series before other detectors. Using multiple detectors extends the range of compounds that can be detected in on

54、e analysis. PID is sensitive to water and must be recalibrated more often than the FID. Photoionization Detector A phoFlame Ionization Detector A flame ionization detector (FID) consists of a stainless steel jet constructed so that carrier gas exiting the column flows through the jet, mixes with hyd

55、rogen, and burns at the tip of the jet. Hydrocarbons and other molecules which ionize in the flame are attracted to a metal collector electrode located just to the side of the flame. The resulting electron current is amplified by a special electrometer amplifier which converts very small currents to

56、 millivolts. The FID is sensitive to almost all molecules that contain hydrocarbons. Examples include aromatic and chlorinated VOCs, petroleum constituents, SVOCs, and PCBs. The FID is a destructive detector that can be used in series only after nondestructive detectors. The FID is sensitive to wate

57、r, but has a wider linear range of detection than the PID. The FID also can detect more compounds than the PID. The FID can detect compounds that contain the low ppb to high part per trillion range. Flame Ionization Detector A flElectron Capture Detector An electron capture detector (ECD) consists o

58、f a sealed stainless steel cylinder that contains radioactive nickel-63. The nickel-63 emits beta particles (electrons) which collide with the carrier gas molecules ionizing them in the process. A stable cloud of free electrons thus forms in the ECD cell. When an electronegative molecule such as a h

59、alogenated molecule enters the cell, it immediately combines with one of the free electrons which temporarily reduces the number of free electrons. The detector electronics pulse at a variable rate to measure the electrons remaining in the cell. The ECD is highly sensitive to electronegative molecul

60、es (those capable of producing negatively charged ions) such as halogenated compounds or those that contain nitrogen. The ECD readily detects chlorinated pesticides, halogenated solvents, PCBs, and dioxins. The ECD is a nondestructive detector that can be used in series before other detectors. The E