Farmland soil monitoring sites generally adopt the pollution site method and place the monitoring sites in suspected or confirmed areas of pollution. Distribution sites should give priority to those places where pollution is heavy and affect the importance of agricultural production. Monitoring sites should be focused on: Irrigated farmland soils; farmland soils surrounding factories and mines and towns; large amounts of industrial wastes, farmland soils around urban garbage sites; farmland soils that have long been affected by industrial exhaust gas and dust; large quantities of agricultural chemical substances such as pesticides, fertilizers, agricultural use Farmland soils such as plastics; Farmland soils with long-term application of sludge, municipal wastes and other solid wastes and fertilizers made from wastes as raw materials; Farmland soils with endemic diseases or areas with endemic diseases, and soils suspected of other pollution.
The layout of farmland soil monitoring points depends on the type of soil pollution. Water quality polluted soil monitoring points should be laid along with the flow direction of sewage irrigation channels. The dot density generally decreases with increasing distance from the water stream. Air pollution-type soil samples should be centered on air pollution sources, and be fan-shaped in one or several parties. The focus of monitoring points should be placed on the prevailing wind-wind direction. The closer to the pollution source, the denser the nodes, and vice versa. Agricultural contaminated soils: Soils contaminated with municipal waste, sludge, chemical fertilizers, and pesticides are all agricultural contaminated soils. Soil monitoring can be based on the distribution of pollutants evenly distributed, but the focus of the distribution point on the pollution load of the field. In the monitoring of solid waste piles contaminated soil, the sampling points shall be centered on the pollution source, and combined with the dominant wind direction and soil erosion direction all the year round. The density of dots decreases as the distance from the source increases.
The farmland soil monitoring samples are generally cultivated layer soil samples. A number of points of the cultivated layer soil are collected around the sampling point, and the equal-quantity uniformly mixed soil samples represent a sampling point of the soil sample. The number of points that make up the mixture is at least three. This is only a small step in the monitoring process. To obtain the final results, a portable agricultural environmental monitoring instrument can be used for accurate monitoring and analysis of the resulting samples, which in turn provides strong scientific data for the development of agriculture.
Plastic Flowmeter is a widely used instrument in water treatment engineering, mainly used for flow detection, usually installed after the water pump, to control the water intake of each structure, currently the most widely used are electromagnetic flowmeter and ultrasonic flowmeter. In the selection of the flowmeter, the first thing to consider is the corrosiveness of the measured medium to the flow-passing parts, so as to avoid affecting the service life of the flowmeter due to the corrosion of the medium; During the design and installation process of the flowmeter, the length of the straight pipes before and after the flowmeter needs to be considered. Usually, the principle of 5D before and 3D after the flowmeter is followed. Here, D is the inner diameter of the pipe. If the length is insufficient, the measurement accuracy will be affected. When using an ultrasonic flowmeter, the distance between the first 10D and the rear 5D must be met, and the distance from the flowmeter to the water pump must be more than 30D.
When selecting the type, the flow rate of the medium in the pipeline needs to be between the maximum value and the minimum value of the selected flowmeter, and avoid approaching the maximum or minimum value, so as to avoid affecting the measurement accuracy.
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