Guangyu Zhao

Mobile lidar system for environmental monitoring

A versatile mobile optical remote sensing system utilizing light detection and ranging (lidar) technology has been constructed and adapted for multidisciplinary environmental monitoring tasks on the Chinese scene. A key application is differential absorption lidar (DIAL) monitoring of distributions of gaseous air pollutants. The system includes a 20 Hz Nd:YAG laser-pumped dye laser, and two vertically looking Newtonian telescopes with diameters of 40 and 30 cm, respectively, over which folding mirrors can be hoisted over the laboratory roof to interrogate the remote target area. Using harmonic pulses from the Nd:YAG laser, remote laser-induced fluorescence (LIF) and laser-induced break-down spectroscopy (LIBS) can be performed. In this way, also water pollutants, vegetation, and soils can be studied. The wide applicability of the new system is illustrated in long-range measurements of atmospheric mercury and sulfur dioxide, and in LIF and LIBS monitoring. Remote passive monitoring of flying insects illustrates the additional functionality of the system.

Laser spectroscopy applied to environmental, ecological, food safety, and biomedical research

Laser spectroscopy provides many possibilities for multi-disciplinary applications in environmental monitoring, in the ecological field, for food safety investigations, and in biomedicine. The paper gives several examples of the power of multi-disciplinary applications of laser spectroscopy as pursued in our research group. The studies utilize mostly similar and widely applicable spectroscopic approaches. Air pollution and vegetation monitoring by lidar techniques, as well as agricultural pest insect monitoring and classification by elastic scattering and fluorescence spectroscopy are described. Biomedical aspects include food safety applications and medical diagnostics of sinusitis and otitis, with strong connection to the abatement of antibiotics resistance development.

The Scheimpflug lidar method

The recent several years we developed the Scheimpflug lidar method. We combined an invention from the 19th century with modern optoelectronics such as diode lasers and CMOS array from the 21st century. The approach exceeds expectations of background suppression, sensitivity and resolution beyond known from time-of-flight lidars. We accomplished multiband elastic atmospheric lidars for resolving single particles and aerosol plumes from 405 nm to 1550 nm. We pursued hyperspectral differential absorption lidar for molecular species. We demonstrated a simple method of inelastic hyperspectral lidar for profiling aquatic environments and vegetation structure. Not least, we have developed polarimetric Scheimpflug lidar with multi-kHz sampling rates for remote modulation spectroscopy and classification of aerofauna. All these advances are thanks to the Scheimpflug principle. Here we give a review of how far we have come and shed light on the limitations and opportunities for future directions. In particular, we show how the biosphere can be resolved with unsurpassed resolution in space and time, and share our expectation on how this can revolutionize ecological analysis and management in relation to agricultural pests, disease vectors and pollinator problematics.

Lidar mapping of atmospheric atomic mercury in the Wanshan area, China

A novel mobile laser radar system was used for mapping gaseous atomic mercury (Hg0) atmospheric pollution in the Wanshan district, south of Tongren City, Guizhou Province, China. This area is heavily impacted by legacy mercury from now abandoned mining activities. Differential absorption lidar measurements were supplemented by localized point monitoring using a Lumex RA-915M Zeeman modulation mercury analyzer. Range-resolved concentration measurements in different directions were performed. Concentrations in the lower atmospheric layers often exceeded levels of 100 ng/m3 for March conditions with temperature ranging from 5 °C to 20 °C. A flux measurement of Hg0 over a vertical cross section of 0.12 km2 resulted in about 29 g/h. Vertical lidar sounding at night revealed quickly falling Hg0 concentrations with height. This is the first lidar mapping demonstration in a heavily mercury-polluted area in China, illustrating the lidar potential in complementing point monitors.

Optical characterization of Chinese hybrid rice using laser-induced fluorescence techniques—laboratory and remote-sensing measurements: publisher’s note

This publishers note corrects the author listing and a figure caption in Appl. Opt.57, 3481 (2018)APOPAI0003-693510.1364/AO.57.003481.

Laser Spectroscopy applied to Environmental, Ecological, Agricultural and Food Safety Research

Laser spectroscopy has a multitude of applications of importance to human and ecosystem well-being, such as in the environmental, ecological, agricultural and food safety areas. Recent work, mostly from SCNU, will be reviewed.

Differential absorption lidar monitoring of atmospheric atomic mercury in China using a novel mobile system

Mercury is a severe pollutant in China. A novel mobile laser spectroscopy laboratory was constructed and used in differential absorption lidar mapping in major Chinese cities, a heavily polluted mining area and an archeological site.

Laser spectroscopy applications for ecology and environmental monitoring

Optical spectroscopy, and in particular laser spectroscopy, has numerous applications in the assessment and probing in ecology, such as agricultural field and flying pest insect monitoring, as well as in the measurement of atmospheric pollutants. An overview of recent work by our group is given.

Method to Monitor Atmospheric Atomic Mercury by a Differential Absorption Lidar System

A differential absorption lidar (DIAL) system has been developed for atomic mercury concentration monitoring and applied in ambient air monitoring in Guangzhou, China. A 24-hour measurement on background atomic mercury has been performed.

Studies on fruit ageing by fluorescence spectroscopy and diode laser absorption spectroscopy

A combination of fluorescence spectroscopy and diode laser absorption spectroscopy is used to investigate ageing processes in fruits, where the changes of chlorophyll content and molecular oxygen concentration are mainly studied.