Introduction
1924 American Scholar FW Clark first published a report on environmental background values, so the average content of various chemical elements in crust, rock, atmosphere and water is also called Clark value. With the development of environmental science, environmental pollution investigation and monitoring requires the normal range of chemical elements in environmental elements, so in recent years, all countries in the world have carried out environmental background values. Understanding the environmental background values of the region on environmental quality evaluation, predicting environmental pollution trends, formulating environmental standards, and formulating a reasonable layout plan for industrial and agricultural production, all have important significance. However, in the case where the global environment is generally polluted, it is very difficult to find the environmental background value that is absolutely no affected by human activities. Therefore, the environmental background value is actually composed of basic chemistry of environmental elements without direct contamination.
Environmental background value classification
In various regions of the earth, due to the different process of natural substances and the natural development process, the background content of various chemical elements in the natural environment is also different. . According to different classification standards, it can be divided into the following categories:
(1) can be divided into atmospheric background values, water background value, soil background value, plant background value;
(2) Separating the environmental cell background value, regional background value, global background value;
(3) is divided into high environmental background values and low environment background values by biological effects.
Environmental background value survey
Environmental background value survey is the foundation of environmental impact assessment, environmental background value investigation should include the following information:
(1) Natural environment : Geological and soil, surface water and groundwater, air quality, climate conditions;
(2) Biological conditions: vegetation, water organism, ecosystem type, endangered plants, protected zone;
(3) Social Economic Conditions: Social and Economic Development Status, Tourism Resources, Infrastructure, Traffic conditions, land use types, cultural and historical resources.
Environmental background value Determination
To determine the background value, sample should be collected from the source of the pollution source, and the determination of its chemical element content, and then, the method, test analysis, etc. As a result, take the average value or numerical range of the analysis data as the background value.
Important meaning
The measurement and research of environmental background values is a basic work of environmental science, the evaluation and prediction of environmental quality, and the law of migration conversion in the environment. And the development of environmental standards, is also provided by environmental illnesses for local diseases and urban reasonable layouts.