Many scientific papers have been written concerning gas sensors for different sensor applications using several sensing principles. This review focuses on sensors and sensor systems for gaseous ammonia. Apart from its natural origin, there are many sources of ammonia, like the chemical industry or intensive life-stock. The survey that we present here treats different application areas for ammonia sensors or measurement systems and different techniques available for making selective ammonia sensing devices. When very low concentrations are to be measured, e.g. less than 2 ppb for environmental monitoring and 50 ppb for diagnostic breath analysis, solid-state ammonia sensors are not sensitive enough. In addition, they lack the required selectivity to other gasses that are often available in much higher concentrations. Optical methods that make use of lasers are often expensive and large. Indirect measurement principles have been described in literature that seems very suited as ammonia sensing devices. Such systems are suited for miniaturization and integration to make them suitable for measuring in the small gas volumes that are normally available in medical applications like diagnostic breath analysis equipment.

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Ammonia sensors and their applications - a review

The detection and measurement of gas concentrations using the characteristic optical absorption of the gas species is important for both understanding and monitoring a variety of phenomena from industrial processes to environmental change. This study reviews the field, covering several individual gas detection techniques including non-dispersive infrared, spectrophotometry, tunable diode laser spectroscopy and photoacoustic spectroscopy. We present the basis for each technique, recent developments in methods and performance limitations. The technology available to support this field, in terms of key components such as light sources and gas cells, has advanced rapidly in recent years and we discuss these new developments. Finally, we present a performance comparison of different techniques, taking data reported over the preceding decade, and draw conclusions from this benchmarking.

/pdf/optical-gas-sensing-a-review-4uaf589xiq.pdf

Optical gas sensing: a review

Adsorption of phenolic compounds by activated carbon—a critical review

Bioretention, or variations such as bioinfiltration and rain gardens, has become one of the most frequently used storm-water management tools in urbanized watersheds. Incorporating both filtration and infiltration, initial research into bioretention has shown that these facilities substantially reduce runoff volumes and peak flows. Low impact development, which has a goal of modifying postdevel- opment hydrology to more closely mimic that of predevelopment, is a driver for the use of bioretention in many parts of the country. Research over the past decade has shown that bioretention effluent loads are low for suspended solids, nutrients, hydrocarbons, and heavy metals. Pollutant removal mechanisms include filtration, adsorption, and possibly biological treatment. Limited research suggests that bioretention can effectively manage other pollutants, such as pathogenic bacteria and thermal pollution, as well. Reductions in pollutant load result from the combination of concentration reduction and runoff volume attenuation, linking water quality and hydrologic perfor- mance. Nonetheless, many design questions persist for this practice, such as maximum pooling bowl depth, minimum fill media depth, fill media composition and configuration, underdrain configuration, pretreatment options, and vegetation selection. Moreover, the exact nature and impact of bioretention maintenance is still evolving, which will dictate long-term performance and life-cycle costs. Bioretention usage will grow as design guidance matures as a result of continued research and application.

Bioretention Technology: Overview of Current Practice and Future Needs

Fungal biosorption — an alternative treatment option for heavy metal bearing wastewaters: a review

Kinetics of phenol biodegradation in high salt solutions.

Measurement of atmospheric ammonia at a dairy using differential optical absorption spectroscopy in the mid-ultraviolet

Although the use of pesticides is as old as agriculture, the advent of synthetic pesticides in the 1940s was one of the most important achievements that spawned the “Green Revolution” (Tilman 1998). Synthetic pesticides, along with the introduction of chemical fertilizers, enabled dramatic increases in agricultural productivity and quality without the need to increase farmland and labor (Seiber and Ragsdale 1999; Cooper and Dobson 2007). Pesticide use reduces the impact of pests on agricultural productivity by about half (Oerke and Dehne 2004; Oerke 2006), and many argue that reduction or cessation of pesticide use would lead to significant crop loss, increased food prices, and lack of food for the world’s growing human population (Fernandez-Cornejo et al. 1998; Ragsdale 1999; Oerke and Dehne 2004; Cooper and Dobson 2007). Moreover, the use of pesticides alleviates food shortages in developing countries, allowing them to grow crops multiple times a year and export produce to developed nations (Ecobichon 2000, 2001; Oerke and Dehne 2004).

Adsorption and Desorption of Chlorpyrifos to Soils and Sediments

Enhanced mobility of Pb in the presence of dissolved natural organic matter

Comprehension du processus de l'adsorption irreversible sur le charbon actif, influence sur l'equilibre d'adsorption. Essais realises en continu et semi-continu sur des solutes de phenols de bas poids moleculaire

David R. Yonge

Papers

Kinetics of phenol biodegradation in high salt solutions.

Measurement of atmospheric ammonia at a dairy using differential optical absorption spectroscopy in the mid-ultraviolet

Adsorption and Desorption of Chlorpyrifos to Soils and Sediments

Enhanced mobility of Pb in the presence of dissolved natural organic matter

Single-solute irreversible adsorption on granular activated carbon.