A device for the depth penetration measurement based on the transmition of He-Ne laser light power through samples of river water was developed.

Abstract not available.

Differential optical absorption spectroscopy has been applied in atmospheric ammonia monitoring. The absorption of gaseous ammonia in the UV region between 190 nm and 230 nm has been examined and compared with spectra of interfering species and atmospheric transmission. A wavelength region around 210 nm was utilized in measurements of atmosphric ammonia over a 265 m path in a rural area with a detection limit of 1 ig/m

Ammonia monitoring is needed in most schemes for denitrification of power plant emission. In the PALAMON system we use a 500 MHz tunable, single mode, single line, CO2 laser as light source for a low pressure, high temperature, photoacoustic cell. With this cell we can resolve the sR(5,O) line of the ammonia spectrum, and suppress the interfering C02(9R30) absorption line down to a lppm NH3 detection limit. The validity of the measured ammonia concentrations is strongly dependent on details of the sampling system and on the reliability of the calibration routines. In particular calibration with certified mixtures of NH3:N2 has proved insufficient due to the multiple and long time constants caused by adsorption of ammonia to different materials in the system. Presence of water vapor in the gas greatly reduces these time constants. Therefore a number of methods for simple production of moist calibration gases from macroscopic amounts of NH3 are applied. The calibrations are translated to response from an easily managable absorber in order to allow automated recalibration of the photoacoustic response. Data from a field test of the system, and calibration data will be presented.

In the environmental problem of acidification, deposition of atmospheric ammonia is an important factor in NW Europe. Background concentrations are generally low but variations due to local sources may be large and rapid, so a sensitive measuring instrument with a high dynamic range and good time resolution is required. A photoacoustic ammonia measurement system with a detection limit for NH3 of about 1 ppbv and a time resolution of about 5 minutes is described. The results of 'a measurement campaign in the field during the spring of 1989, with the instrument installed in a caravan, will be reported. Concentrations were determined at a single position above the ground (2 m.). The instrument has since then been adapted to measurements at four different heights from which vertical fluxes can be derived. The encouraging first results will be presented.

With the passage of the 1977 Clean Air Act Amendments, the United States Congress emphasized visibility protection for the pristine areas of the country as a major national goal. Federal programs were implemented to estimate existing levels of atmospheric extinction. Until recently, this has been accomplished primarily by the use of various techniques to measure apparent target/horizon sky contrast. While the ability of these methods to accurately determine contrast is well proven, the estimation of extinction using the Koschmieder relationship is usually compromised by theoretical assumptions that are typically not met in practice. To address this problem, the United States National Park Service has supported the development, testing, and deployment of an instrument that accurately and reliably measures the transmission of an ambient atmospheric optical path. The average atmospheric extinction coefficient of the path can be calculated directly from this measurement. This transmissometer consists of a constant output light source transmitter and a computer-controlled photometer receiver. The irradiance at visible wavelengths from the transmitter can be measured to a high degree of accuracy both day and night over path lengths of 0.5 to 30km. A complete description of the transmissometer will be presented. Atmospheric optical considerations will be combined with design parameters and experimental data to confirm the ability of this instrument to make an accurate, precise, and reliable extinction measurement.

A quantitative measurement of laser light extinction during particle growth in an expansion chamber of a condensation nuclei counter was performed. The attenuated light flux and the light flux scattered at a chosen scattering angle are monitored simultaneously during the particle growth process. From the transmitted light flux vs time the light extinction during particle growth can be determined quantitatively. The experimental scattered light flux vs time allows a precise determination of particle sizes at various times during particle growth. Knowing the actual particle size the light attenuation obtained from the transmitted light flux allotis a direct, quantitative determination of particle number concentration without referring to any calibration of the apparatus and can be regarded as an absolute method.

In this paper a near-JR diode laser system for emission and process control has been designed and tested. The system utilizes derivative spectroscopy to increase the sensitivity of the measurement due to the low line strengths of the absorption lines in the 0.7 - 1.7 p.m wavelengths region. A minimum detectable absorbance of 2 iO-5 was obtained at an integration time of 3 ms. Oxygen was used in the experiments and the corresponding minimum detectable concentration was 200 ppm. No interference effects was observed from co-existing emission gases. The system utilizes a unique modulation concept for compensation of non'gas-related transmission variations in the measurement path. Due to the short response time the system is very useful for on-line process control.

Mercury is the only atmospheric pollutant that is present in the atmosphere in atomic form. Range-resolved Hg mapping can be performed using the differential absorption lidar (dial) technique employing the 254 nm Hg resonance line. We have used the lidar technique both for mapping of industrial plumes and for background concentration measurements. Our studies also include mercury of geophysical origin. A field test has been performed in Icelandic geothermal fields. We have also attempted studies of Hg emission from lake surfaces.

Optical and laser remote sensing techniques provide powerful tools for environmental monitoring in particular for determination of concentrations of atmospheric pollutants .TheifferentiaI absorption and catteiing (DAS) lidar method is very well suited and widely used to measure from ground conceniration of e.g. 502, NO2, NO and O316. The available systems are mainly stationary in laboratories of research institutes and few of them are now mobile, mounted on trucks and trailers. ARGOS (advanced remote gaseous Qxide ensor) is based on many years experimental experience in the area of remote air pollution measurements of the in Geesthacht, a resaerch institute located in the vincinity of Hamburg. In this paper the objectives, specifications and realization of a vanboine air pollution measurement system will be presented based on advanced electro-optical and computer equipment as well as on a wind profile sensor. The emphasis of the development is to realize a mobile and operational system not to verify applied methods and techniques.

By linking a battery operated logger unit and power supply with a submersible fluorometer we have been able to make continuous untended measurements ofphytoplankton chlorophyll fluorescence, and hence estimate algal biomass for periods of up to 35 days at moorings. Calibration aixi data processing procedures are described, and some examples of the results of deployments in waters around the United Kingdom are presented.

New, optical, approaches to automatize and to accelerate the analysis of algae are discussed. Firstly, the application of flow cytometric analysis will be presented. This technique is based on classification of particles in flow by measuring several optical properties per individual particle. Characteristics of the Optical Plankton Analyser, a flow cytometer constructed specifically for the analysis of phytoplankton, will be presented. Two experiments that demonstrate the suitability of this instrument for the analysis of coastal phytoplankton will be presented. Subsequently, the applicability of flow cytometry and other optical approaches to the measurement of phytoplankton, in particular for monitoring purposes, will be discussed. Microscopy, as well as in-situ measurement and optical remote sensing are approaches that each offer specific advantages for the determination of phytoplankton. An optimal and integrated picture of the development of the distribution of phytoplankton species in space and time can be obtained by the combined application of these techniques.

The exciatation light intensity 'e provided by a 6 mW He-Ne laser is switched by a combination of an acousto-optical modulator OS and a mechanical shutter MS. A switching-time below 0.3 s and a power density of 10 mW/cm2 at the object are achieved. Two photoinultipliers measure the fluorescence intensities F685(t) and F730(t) at the two peak wavelengths (685 mu and 730 mn), the nieasuring signals are synchronously stored by a transient recorder with a time resolution of 10 p.s and a capacity of 8000 pairs of measuring values and by a computer with a time resolution which is decreased in steps from 200 1L5 to 200 ins within the total measuring time of 5 mm. The combined use of OS and MS ensures the stability of 'e within 5% during the total measuring time. In addition to the peak intensity F0 and the steady-state intensity F5 which are commonly determined b' devices with low time resolution, the initial intensity Fb and its time derivative Db and intensity F1, time tj, and time derivative D of the inflection point can accurately be determined by the device. The ratio R(t) = F730(t)/F685(t) shows an initial value Rb which is similar to the steady-state-value R5 and two minimum values Rml and Rm2 near 10 ms and 15, respectively.

Three novel techniques of fiber-optic spectroscopy have been recently introduced into research of forest decline. These include measurement of luminescence changes and fluorescence-decay of chiorophylls (i) under continuous irradiation, and after pulse-induction in the (ii) long-term and the (iii) picosecond time range. These changes will be correlated both with environmental factors such as air pollutants, soil, fertilization and various experimental and physiological conditions.

Ultraviolet fluorescence spectroscopy is now widely used in surveys and monitoring studies for the determination of hydrocarbon concentrations in seawater. This paper describes a high sensitivity in-situ ultraviolet fluorimeter, discusses calibration methods and illustrates some appl icat ions.

The developed laboratory prototype fluorimeter is the first step to a new in-situ instrument, and is based on a pulsed nitrogen laser (pumping a color dye laser and the laserbeam passing through a frequency doubler) with a pulse width less than 1 nsec. With such a short excitation pulse it is possible to measure the exponential decay of the fluorescence from the aromatic compounds and thus determine the fluorescence lifetime-curves, which are typically in the region of 5-40 nsec. The emitted fluorescence is collected simultaneously in 35 channels in the wavelength region 250-600 nm. If the fluorescence falls within the transmission areas of the interference filters in each channel the light will be collected by a plastic light guide (doped PMMA) in the actual channel and transmitted to the channels photo multiplier tube (PMT). (The use of the plastic light guide improves the sensitivity). The signal from the PMT is passed on to a 200 MHz 8-bit flash AID-converter connected to a local memory. From this local memory the digital lifetime curves from each channel are transmitted to a computer for presentation of the 3-dimensional spectrum. This spectrum has been obtained with a single laser shot.

Use of UV-visibletransmitting optical fibers for real-time, remote, in situfluorescencemeasurementsof chemical constituents in environmental samples is described. In order to improve the capability of fluorescence techniques for resoMng complex mixtures we have deVelOped a fiber optic-based system that uses a pulsed nrogen laser to induce fluorescence and a time-gated linear photodiode array coupled to a spectrograph for measuring resutting emisalon spectra This permfts rapid extraction of both spectral information and temporal data (fluorescence decay times). The performance of the system for monftoring aromatic hydrocarbons directly in seawater over a bare-ended" fiber optic cable is discussed. Techniques for extending the Capability to determination of metals and other non-fluorescing compounds are presented. A system in which a fluorogenic indicator molecule for metal ions is constantly renewed at the sensing end of the fiber is described that (1)exhibits very fast response times (1 second) and (2)eliminates problems of reversibility common with immobilized indicators. Presently, the pulsed-laser/photodiode fiber optic system is being adapted to a truck-mounted cone penetrometer system for characterizing the distribution of chemical contaminants at hazardous waste sites. The system can push a 35.7 mm diameter rod up to 50 m into the sI at a rate of approximately 2 cm/sec. The penetrometer probe tip will be equipped with sapphire viewing windows that permft one fiber to screen for aromatic orgarc compounds and a fluorogeruc indicator release system that can be used with a second fiber for trace metal screening.

Since 1988 oceanographic vehicles equipped with a variety of optical sensors have been deployed successfully from ships-of-opportunity in the North Sea as part of an environmental monitoring programme. The towed vehicles are deployed and recovered by the ship's crew and the instrument packages are activated automatically during the tow by electronic sea water switches. The vehicles carry sensors for measuring chlorophyll fluorescence, turbidity, conductivity, temperature, depth and upwelling and downwelling light in three wavebands; the measurements are stored in a solid state logger. The filters used in the irradiance sensors have wavelengths at 412, 450 and 550 nm with sensitivity at 0.1 pW cm2. The light measurements are used for the determination of the diffuse attenuation coefficient and the reflectance of blue light (R4l2, R450) and green light (R55O) and together with measurements of chlorophyll fluorescence are being used for the development of an algorithm for estimation of primary production in coastal waters and the open sea. Data are shown from a number of fixed-depth and variable-depth vehicle deployments from selected shipping routes in 1988/89, including a Copenhagen, Kattegat, Skagerrak, North Sea, Harwich route. From March 1990 a nutrient sensor measuring combined nitrite, nitrate in a continuous flow analyser will be carried by these towed vehicles.

In the proposed paper an empirical method has been developed for determination of nitrous oxide concentration using the absorption band 2'), in proximity of), 3.87J4m, free from overlapping with absorption bands from other atmospheric gases. The transmission spectra of the atmospheric air are recorded with unresolved rotation-vibration structure. The method is inexpensive, simple and efficient It may be used for determination of enviromental pollution in homogeneous media (laboratory or production plant conditions, ground layer of atmosphere) and of unhomogeneous composistion mixtures when studying the contents of nitrous oxide along slope paths in troposphere and stratosphere.

The design and the main features of the new double pendulum type michelson interferometer (DPI) by Kayser-Threde are presented. The advantages of this spectrometer in comparison to conventional Fourier spectrometers are discussed. The DPI is compact in design, mobile, insensitive to vibrations and temperature changes and, thus, well adapted to field measurements. The spectrometer was applied to emission as well as immission measurements of air pollutants. Several molecules could be identified and their concentrations could be estimated. The detection limit of the DPI yields 15 - 60 ppm depending on the analyzed gas for emission measurements, 6 - 84 ppb for immission measurements.

The problems of the use of space photographic survey are discussed regarding exploration of the Earth natural resources. The concrete information is presented on the successfully operated Soviet equipment system. A conclusion is drawn on the feasibility to set up international Earth remote sensing global system with a view to enhance economy efficiency, scientific research, environment monitoring and contribute to solving other problems pertaining to development of the mankind habitat.