| Environmental workers,agriculturists and those scientific researchers are all keen on the study of soil heavy metal pollution.In the context of ecological civilization and food security,the safety of agricultural products,including heavy metal pollution at the origin of agricultural products,has become a major obstacle to agricultural development.With the ever-changing science and technology,how to quickly and effectively build a soil heavy metal evaluation system has also become a major research hotspot.By studying the system of information and assessment of soil heavy metal pollution at home and abroad,the present study found that most of the current studies on soil heavy metal systems in B/S framework are only in the stage of "sharing results data",and there are few studies on"sharing of functions".However,for the increasing data and changes in user needs,it is not enough to just stay at the level of sharing results data.In this study,B/S WebGIS architecture program was used to establish a database of heavy metal pollution information of soil based on the data of heavy metal sampling sites in a certain area.WebGIS visualization technology,HighCharts charting technology,Canvas technology and ArcGIS API for JavaScript programming interface were selected,and combined with the commonly used evaluation methods and a variety of evaluation analysis model of soil heavy metal pollution,a method of evaluating and visualizing system of soil heavy metal pollution based on the sharing of geographic processing services was developed.The main contents and results are as follows:(1)In this paper,the single-factor index method and Nemerow comprehensive pollution index method were used to evaluate the data of heavy metal sampling sites in soil.At the same time,a set of soil heavy metal pollution information database was established according to the database design principles and specifications,combined with the relevant environmental data of the study area,aiming to providing data support for follow-up soil heavy metal pollution system development.(2)In consideration of the needs of customers,development costs,convenience and comprehensiveness,this system uses the geographic processing service which is provided by ArcGIS Server to realize the sharing of soil heavy metal pollution evaluation model.That is to say,by combining various ArcTool tools,this paper uses the geoprocessing service of ArcGIS to construct a variety of statistical application model of soil heavy metal pollution evaluation and analysis,which provides method support for the implementation of the sharing of soil heavy metal data and analysis of the service.(3)In the aspect of map loading,the system uses the double caching technology of map tiles and On-demand loading technology to achieve rapid and efficient display of base map and some heavy metal data in soil.In raster data rendering,this paper discusses the current rendering technology of the Web animation graphics to find and select the feasible scheme and technology for this system.In the visualization of statistical charts,this paper discusses the visualization techniques of dynamic charts and selects the suitable drawing technology for this system.(4)A new set of WebGIS geo-processing services for soil heavy metal pollution evaluation and visualization system is established.It mainly includes the following three modules:the function of basic map,Spatio-temporal visualization of pollution and the comprehensive analysis of pollution.The system has many features such as multi-scale,adjustable parameters,modularization,real-time processing and real-time statistical analysis,in which the comprehensive sharing of results data and model functions can be fully achieved.The system has a clean and tidy interface with detailed description and simple operation.It provides simple,fast and accurate technical support for the relevant industries and departments to carry out heavy metal pollution analysis and prevention and treatment work. |
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