Remote sensing is an efficient way to detect environmentally vulnerable terrain, where waste chemicals and excess fertilizers must result to considerable pollution of soil and groundwater. The indicators of such vulnerable formations were analyzed and applied for investigation of ground microdepressions. First indicator was the humidity level that was well recognized from the satellite images by calculation of normalized water index (NWI). Another active indicator used for the detection was the relief. The method of relief plastics joint with morphodynamic analysis was suggested for the data processing. The scheme of water basins and the map of environmentally fragile areas were created by combination of the indicators of soil humidity and topography. On the basis of the created maps, the restrictions for used chemicals can be developed in order to preserve considerable environmental impact of the pollution.
TopIntroduction
The problems of ecological monitoring and remote analysis of chemical pollution are closely related to environmental chemistry (Bahadir & Duca, 2009). It is important to develop the methods of remote sensing that can be efficiently applied for detection of environmentally fragile areas, where waste chemicals and excess fertilizers must result to considerable pollution of soil and groundwater. Such vulnerable terrestrial formations like temporary ponds or ground microdepressions were not widely investigated. However, these formations greatly influence the environment, because pollutants tend to concentrate here and then propagate to groundwater (Keesstra et al., 2012).
There are different sources of contaminants including agrochemicals, natural gas, petroleum hydrocarbons and potentially toxic elements (Gholizadeh et al., 2018). The pollutants can be detected using extensive sampling and conventional techniques of analytical chemistry. This requires a complex infrastructure to support the entire sampling, laboratory and field based analysis, as well as data processing activities (McLean et al., 2019). So, it is important to develop more simple, rapid and cost-effective sensing technologies that can be used for monitoring of large areas, where the analytical networks have not been constructed.
Remote sensing approach is based on characterization of investigated object without direct contact. There are a lot of sensor systems that are developed for this purpose: object presence and motion detectors, directional microphones and thermometers, variety of photodetectors, radar stations etc. In contrary, widely used chemical sensors are not appropriate for remote detection. Analyzed substance interacts with a sensor by way of physical or chemical processes on its surface (Manilov et al., 2019). Thus, a contact of the analyte and the detector is necessary. It can be used to analyze the sample at the monitoring site. However, the ability to determine certain chemical compounds without contact is very important for applications in aerospace sensor systems.
Remote sensing data for characterization of the Earth’s surface can be registered by terrestrial stations, aircraft (especially pilotless vehicles), space stations or satellites. Passive or active sensing methods are used (Lillesand, Kiefer, & Chipman, 2015). Main way of the passive data collection is detection of electromagnetic waves received from investigated objects. Measurements of spectral reflectance are made to separate areas with different types of soil, water and vegetation. The most valuable results are obtained in visible, near infrared and thermal, long wavelength infrared range. The multichannel detectors working in corresponding spectral bands are installed on research aircraft and satellites. The active methods of remote sensing are mainly released by radar systems working in microwave band. Main focus of the radar measurements is exploration of land and water surface in order to produce maps and digital elevation models. Monitoring of an atmosphere and meteorological processes are also provided (Chen et al., 2005; Clevers et al., 2008; Maeda et al., 2015).
Most of the remote sensing systems are devoted to the problems of mapping, weather and climate control, natural resources and agriculture, as well as disaster risk management. However the problems of ecological monitoring and remote analysis of chemical pollution are also important. The data obtained by remote sensing are used for detection of heavy metals and excessive fertilizers in soil, crops and forests. Analysis of atmospheric pollution, emission from urban zones and vehicles is also supported by satellite data, as well as search of oil spills in water. The specialized detectors are developed that help to improve the quality of remote sensing data from the standpoint of environmental chemistry (Keesstra et al., 2012; Kostyuchenko et al., 2013).