Study On Environmental Benchmark And Standard System Of Soil Heavy Metals In Shandong Province

The deterioration of soil environment quality, caused by the rapid progress ofurbanization and industrialization, has been paid widespread attention in soil scienceand environmental science. Large amounts of pollutants, especially heavy metalcontaminants, penetrate into soil in different ways, leading to a serious deteriorationin the quality of soil ecological environment. Due to the complexity of soil type andvegetation variety in our country, it is difficult to employ a unified nationalenvironmental quality standard to evaluate the quality status of soil environment afterdifferent kinds of heavy metals go into the soil. Therefore, it is essential to build astandard system to reflect the local soil quality according to the characteristics of theregional soil. Which has a very important and practical significance to the scientificprotection of soil environment and the improvement of soil quality. The researchresults will provide a basis for soil environmental supervision and integrated pollutionprevention and control in Shandong Province, and will also provide referencemethods to build a regional standard system of soil environment quality.In this paper, in order to acquire the benchmark value of soil heavy metals,cinnamon soil, moisture soil and brown soil, which accounted for over90percent offarmland soil in Shandong Province, were taken as examples to analyze thebackground value, critical value of Cu, Zn, Pb and Cd by means of literatureconsulting, field research and simulation experiments of plant effect and soilmicrobial effect. On the basis of previous research results, the Quality standardsystem of soil heavy metals environment of Shandong Province will be established.Afterwards, the differences between the evaluation of quality of soil environment andsoil environmental capacity through the established standard system and the nationalsystem will be compared by different evaluation methods, in diverse study areas. The main conclusions are as follows:⑴The critical value of plant effect of heavy metals in soil: Taking the fact thatthe cabbage biomass reduces10%as the basis, through fitting equation, the fullamount critical value of Cu in cinnamon soil, moisture soil and brown soil inShandong are worked out to be respectively as96.11、101.8、36.21mg/kg; Zn,113.3、140.5、115.5mg/kg; Pb,45.59、408.0、236.4mg/kg; Cd,6.490、6.512、8.369mg/kg;the effective content critical value are: Cu,24.59、31.45、7.535mg/kg; Zn,19.26、23.07、22.73mg/kg; Pb,6.253、78.64、46.19mg/kg; Cd,6.253、78.64、46.19mg/kg.The full amount critical value differ a lot from the effective content critical value inthree soils in Shandong, for instance, in moisture, the full amount critical value of Cuis101.8mg/kg, however, in brown soil, it is just36.21mg/kg. the general trend is thatthe full amount critical values and the effective content critical values of Cu, Zn andPb are all highest in moisture soil. For Cd, in brown soil. This indicates that variousheavy metals have various effects to plants in different soils, thus evaluating thequality status with one unified standard inevitably biased.⑵The critical value of biomass effect of heavy metals in soil: Taking the factthat the urease activity decreases25%as the basis, through fitting equation, the fullamount critical value of Cu in cinnamon soil, moisture soil and brown soil inShandong are worked out to be respectively as161.0、130.0、225.0mg/kg; Zn,142.0、257.5、318.3mg/kg; Pb,487.6、630.0、492.5mg/kg; Cd,14.10、16.38、12.69mg/kg;the effective content critical value are:135.0、112.0、91.50mg/kg; Zn,44.33、47.0、64.5mg/kg; Pb,133.0、113.0、89.50mg/kg; Cd,8.881、10.08、9.318mg/kg. The fullamount critical values of Cu, Zn, Pb and Cd are all highest in moisture soil. Theeffective content critical value differ a lot, with Cu and Pb being highest in cinnamonsoil; Zn, in brown soil; Cd, in moisture soil.Taking the fact that the catalase activity decreases25%as the basis, throughfitting equation, the full amount critical value of Cu in cinnamon soil, moisture soiland brown soil in Shandong are worked out to be respectively as273.4、315.5、241.5mg/kg; Zn,239.4、247.0、183.5mg/kg; Pb,560.5、501.0、500.5mg/kg; Cd,16.58、 16.90、10.84mg/kg; the effective content critical value are:93.92、123.1、149.9mg/kg;Zn,48.96、48.31、63.10mg/kg; Pb,95.80、95.67、109.9mg/kg; Cd,9.821、10.46、7.994mg/kg. Various heavy metals have various effects to soil microorganism indifferent soils, so does it to plants and microorganisms. Thus overall consideration is amust when the critical values are applied in the calculation of environmental capacityand the benchmark value of soil.⑶By comprehensive analysis of various research results of main soil types inShandong between1979and1990, and according to the confirmation of field researchsampling in2009, the background values of Cu in cinnamon soil, moisture soil andbrown soil are worked out to be respectively23.58±1.29、22.70±1.32、22.94±9.10mg/kg; Zn,64.49±1.26、64.03±1.27、57.80±27.04mg/kg; Pb,22.41±6.24、25.98±1.22、30.22±16.33mg/kg; Cd,0.0813±0.0214、0.0985±0.0376、0.0607±0.0301mg/kg.The base of Cu and Zn is the reduction of plants being10%in the soil-plantssystem. The base of Pb and Cd is the critical value when the Pb and Cd absorbed byplants equals the National Food Hygiene Standards in the soil-plants system. Theresults are: the full amount critical values of Cu in cinnamon soil, moisture and brownsoil are96.11、101.8、36.21mg/kg；Zn,113.3、140.5、115.46mg/kg；Pb,126.7、134.9、92.84mg/kg；Cd,0.579、0.808、0.361mg/kg. The effective content criticalvalues in cinnamon soil, moisture soil and brown soil are: Cu,24.59、31.45、7.535mg/kg； Zn,19.26、23.07、22.73mg/kg； Pb,14.56、18.22、9.219mg/kg；Cd,0.381、0.650、0.315mg/kg. The full amount critical values of soil heavy metalsare all under the second level of National Soil Environmental Quality Standard. Thusit can be used as the basis of making the environmental quality standards of soilheavy metals of Shandong Province.⑷The building of soil heavy metals standard system of Shandong Province:abiding by the four basic principles of standards making, three levels of soil heavymetals standard system are made, which differentiate the types of soils and whole"binary value". The first level is the background values of heavy metals in cinnamonsoil, moisture and brown soil in Shandong; the second level is the critical values ofheavy metals in cinnamon soil, moisture soil and brown soil respectively. The third level is the second level standards of national soil environmental quality standardsclassified by pH values. The standard system thus constructed not only reflects thefeatures of the main farmland soil in Shandong Province, but also runs parallel withexisting national soil environmental quality standards. However, the critical values ofCd in cinnamon soil, moisture soil and brown soil in Shandong Province are0.6,0.8and0.5mg/kg respectively, which are higher than the values set in the second levelstandards of national soil environmental quality standards, i.e.,0.3,0.6, and0.3mg/kgrespectively. According to Article15of the Second Chapter of The People’s Republicof China Environmental Protection Law", the second level of critical values of Cd incinnamon soil, moisture soil and brown soil in Shandong Province are set to0.3,0.6and0.3mg/kg respectively. For the soil types in Shandong Province, the second levelof Cd standards are too restrictive.⑸The application of the standard system constructed in this paper to evaluateShandong basic farmland soil and Laiwu farmland soil with "single factor pollutionindex","accumulation pollution index" and "integrated pollution index" techniquesand the comparison of the results gained from the above process with results gainedadopting national soil environmental quality standard system has helped to find thesefindings below: In the areas where soil samples exceed not to much, provincial soilenvironmental quality standards and national soil environmental quality standardshave few differences. In the areas where soil samples exceed the provincial standardsbut do not reach the national standards, the results will differ: using the provincialstandards, the result will be "polluted", however, using the national standards, theresult will be "not polluted". While in the areas where soil samples exceed too much,the application of different standards will lead to different levels of pollution. Thisshould be paid attention to in real practice.Based on the provincial standard and the national standard of the second level ofthe total static and dynamic environmental capacity, there is no difference in Cd, littledifference in Cu, and rather big difference in Pb and Zn. The heavy metal contents inbasic farmland soil in Shandong Province ranges between the critical values of theprovincial standard and the national standard, so there are much difference between the static capacity and the individual environmental capacity index of the two existingstandards. The contents of heavy metals in the farmland of Laiwu are under thecritical values of the province standard and the national standard. Therefore, the staticcapacities in the two existing environmental standard system are different, whiledifferences between any individual environmental capacity index are not large.Due to many factors: the complexity of soil and vegetation, the shift andtransformation of heavy metals after they penetrate into soil, great difference ofbiotoxicity, the background values are always the aporia of this domain. Therefore,the key point of this paper is to explore based on the construction of research methodsand standard system of background values of regional soil heavy metals. The aim ofthis paper is to provide a basis for soil environmental supervision and integratedpollution prevention and control in Shandong Province, and also provide referencemethods to build a regional standard system of regional soil environment quality.