Soil Geochemical Background Value and Environmental Quality Assessment in Jinan City

Hongjin WANG Chao YU Wenkai REN Yan GUO

Abstract ［Objectives］This study was conducted to accurately assess soil and environmental quality in Jinan City.

［Methods］ Based on the multipurpose regional geochemical survey data of 1∶250 000 in Shandong Province, the differences between the soil geochemical background values of 54 indexes in Jinan City and the soil in the whole province and the comprehensive geochemical class of soil quality were studied.

［Results］ The contents of C and Cao in Jinan soil was significantly higher than the background values of Shandong Province. The Cd, Cr, Cu, F, Ni, Sn, MgO, Cao and Na2O contents and pH value were higher than the abundance of the A soil layer in China, but the nutrient index contents of Se, I and OrgC were lower than the national background values. The surface soil quality in the study area was generally good, with the sum of superior, good and medium accounting for 99.76% of the total area of the study area. The distribution area of poor soil was the least, accounting for only 0.24%, and it was scattered near industrial and mining enterprises in the urban area of Jinan City, Laiwu District, Gangcheng District and Zhangqiu District, which was closely related to human activities.

［Conclusions］ This study has practical guiding significance for improving land use efficiency.

Key words Surface soil; Background value; Geochemistry; Land quality; Assessment; Jinan city

Received: June 23, 2020  Accepted: August 25, 2022

Supported by Ministry-Province Cooperation Project (1212010310306).

Hongjin WANG (1979-), female, P. R. China, senior engineer, devoted to research about agro-ecological geochemical survey.

*Corresponding author.

With the gradual acceleration of the process of industrialization, human beings are also facing a series of serious problems such as environmental degradation and resource depletion.  Land is the most basic resource to ensure human survival. It is imperative to coordinate the relationship between man and land and maintain sustainable use of land resources. Therefore, accurate evaluation of land quality and determination of land quality classes have practical guiding significance for improving land use efficiency. Since 2003, Shandong Province has completed the multipurpose regional geochemical survey of 1∶250 000 more than 15 years in the provinces land area［1-5］. The data used in this study were all from these achievements.

General Situation of the Study Area

Jinan City is located in the central and western parts of Shandong Province, on the southeastern edge of the North China Plain, surrounded by Mount Tai in the south, across the Yellow River in the north, and fronting water and with hills on the back. It is located on the junction of the low mountains and hills in the central and southern Shandong and the impact plain in the northwest of Shandong, and has a total area of 10 244.45 km2 (Fig. 1). The terrain is high in the south and low in the north, showing the landforms of low mountains and hills, piedmont alluvial-proluvial inclined plain and Yellow River alluvial plain from south to north. The tectonic structure is located in the connecting area of the Jiyang Depression in the North China Depression of the North China Plate and the Central Shandong Uplift in the West Shandong Uplift. The north is the Jiyang depression and the Zibo-Chiping depression, and the south is the Central Shandong Uplift. Jinan City has a monoclinic structure inclining northward. The stratum is old in the south and new in the north. The southern part is dominated by Paleozoic limestone, and the northern part is dominated by Cenozoic loose deposits. The soil types are brown soil, cinnamon soil, fluvo-aquic soil, lime concretion black soil, paddy soil and aeolian sandy soil, among which brown soil and cinnamon soil are the two main soil types. The land use types mainly include paddy field, irrigated land, dry land, orchard, forest land, other forest land, other grassland, urban construction land, transportation land, water surface, tidal flat and other land.

Working Methods

Sample collection and analysis

The sampling depth of soil surface samples was 0-20 cm. The sampling density was 1 point/km2, and 4 km2 was combined into one analysis sample. A total of 2 543 samples were analyzed and tested. Total analysis was performed on 54 indexes including Ag, As, Au, B, Ba, Be, Bi, Cd, Co, Cr, Cu, F, Hg, La, Li, Mn, Mo, Nb, Ni, P, Pb, Rb, Sb, Sn, Sr, Th, Ti, U, V, W, Y, Zn, Zr, Ge, Ce, Tl, Se, Ga, Sc, Cl, Br, I, N, C, S, OrgC, K2O, MgO, CaO, Al2O3, TFe2O3, SiO2, Na2O and pH, and the testing work was completed by Hubei Geological Research Laboratory. The accuracy and precision were monitored with the national first-class soil standard material. The sample analysis quality was monitored by random inspection and abnormal point random inspection, and repeated analysis was carried out to assess whether sampling and analysis errors had a significant impact on regional geochemical changes, so as to ensure the reliability of analytical quality［3］.

Background value calculation methods

The soil element geochemical background values refer to the content values of the surface soil elements in the area formed by natural transformation and human activities (environment II), which are the results of the combined effect of environment I and environment II. On the one hand, they have a close inheritance relationship with the soil reference values, and are generally controlled by the soil reference values. On the other hand, due to long-term natural effects such as weathering and leaching, as well as the transformation of human activities such as production and life, the geochemical characteristics of the surface soil have changed to a certain extent, resulting in a certain difference with the reference values of the deep soil［4-8］.

The soil geochemical background values in the study area were first obtained according to Statistical interpretation of data―Normality tests (GB/T4882-2001), and a normality test was performed on the shape of the frequency distribution of the data［5-8］. When the statistical data obeyed a normal distribution, the arithmetic mean (X) represented the background value, and the arithmetic mean plus or minus 2 times the arithmetic standard deviation (X±2S) represented the variation range of the background value; for data subject to log-normal distribution, the geometric mean (Xg) represented the background value, and the geometric mean multiplied or divided by the square of the geometric standard deviation (Xg·S±2) represented the variation range of the background value; and when the data did not obey the normal distribution, elimination was performed according to the arithmetic mean plus or minus 3 times the arithmetic standard deviation (X±3S) or the geometric mean multiplied or divided by the cube of the geometric standard deviation (Xg·S±3), and when the data obeyed the arithmetic normal distribution or logarithmic normal distribution after repeated elimination, the soil background value was represented by the arithmetic mean or geometric mean, and the arithmetic mean plus or minus 2 times the arithmetic standard deviation (X±2S) or the geometric mean multiplied or divided by the square of the geometric standard deviation (Xg·S±2) represented the variation range of the background value. When the data still did not meet normal distribution or log-normal distribution after repeated elimination, and obeyed a skewed distribution, the background value was represented by the mode or average value; and when the distribution was bimodal or multimodal, the median or average value was used to represent the background value.

Agricultural Biotechnology2022

① Compared with the average soil values of Shandong Province (layer A), the surface soil background values of C and CaO in Jinan City were significantly higher, and specifically, they were 1.21 and 1.20 times of the average values of soil elements in Shandong Province, respectively; and the contents of As, B, Bi, Li, Se, and OrgC were relatively higher, while the content of Sr was relatively lower, and the contents of the remaining elements were equivalent to the background values of soil elements in the whole province. Compared with the A layer of the soil in China, Cd, Cr, Cu, F, Ni, Sn, MgO, CaO, Na2O and pH were 1.14-1.92 times of the national soil abundance in the A layer. Among them, the content of Cd was 1.6 times of the national soil abundance, and the background values of Ag, Sb, W, Se, I, and OrgC were 52%-74% of the national abundance. These are mostly beneficial elements for plant growth, which should be paid attention to.

② The coefficients of variation of the original data in the study area were between 0.09 and 3.61. The indexes with the coefficients of variation greater than 1 were Hg, Sb and Cl elements. The data had a high degree of dispersion, and the contents varied greatly, especially in densely populated urban areas. The indexes with coefficients of variation between 0.3 and 1.0 included Ag, Bi, Cd, Cr, Cu, Au, Ni, P, Pb, Sn, Th, W, Zn, Se, Br, I, C, S, OrgC, and CaO. The data had a relatively high degree of dispersion, and the contents changed greatly. The indexes with the coefficients of variation less than 0.15 included Nb, Ti, Y, Ge, Al2O3, SiO2, K2O and pH. The data had a small degree of dispersion, and the content distribution was uniform. After removing outliers outside the mean (±3) times the standard deviation from the original data, the degree of dispersion of the data was significantly reduced, and the coefficients of variation were between 0.04 and 0.46.

Comprehensive Geochemical Classification of Soil Quality

Classification basis and methods

Firstly, comprehensive geochemical classification was performed on the soil nutrients and soil environmental quality of the surface soil in the study area. Then, the comprehensive geochemical classes of soil nutrients and soil environmental quality were supoerposed according to Table 2, finally obtaining the comprehensive geochemical class of soil quality.

Evaluation results

The evaluation results showed (Fig. 2) that the surface soil quality in the study area was generally good, with the sum of superior, good and medium accounting for 99.76% of the total area of the study area. Among them, the good soil accounted for the highest proportion, at 58.91% of the total area of the study area, with an area of 6 034.74 km2, mainly distributed in Shanghe, Jiyang, Zhangqiu, Pingyin and parts of the main urban area; the area of superior soil was 3 020.96 km2, accounting for 29.49%, mainly distributed in the south of Shanghe River, the north of Jiyang District, Zhangqiu District and the southeast of the urban area. The soil distribution area of the medium area was 1 163.72 km2, accounting for 11.36%, distributed in Laiwu District, Gangcheng District, the urban area of Jinan City and the southeast mainly and in other areas in a scattered manner; and the higher contents of Cd, Cr, Cu, and Ni in the southeast of the urban area were related to the high background values of the bedrock area, and those in other areas were related to human production and living activities. The distribution area of poor soil was the least, at 24.59 km2, accounting for 0.24%. It was mainly distributed in the vicinity of urban chemical plants, thermal power plants and steel and coal mining enterprises, and the polluting elements were mainly Hg, Cu, Cr, Cd, Ni, and Pb, which was closely related to industrial coal combustion in enterprises and discharge of dust, waste water and waste residue.

Conclusions

① Compared with the average values of soil in Shandong Province (layer A), the contents of C and CaO were significantly higher, and specifically, they were 1.21 and 1.20 times of the average values of soil elements in Shandong Province, respectively; the contents of As, B, Bi, Li, Se and OrgC were slightly higher, while the content of Sr element was relatively lower, and the contents of other elements were equivalent to the background values of soil elements in the province. Compared with the A layer of the soil in China, Cd, Cr, Cu, F, Ni, Sn, MgO, CaO, Na2O and pH were 1.14-1.92 times of the national soil abundance in the A layer. Among them, the content of Cd was 1.6 times of the national soil abundance, and the background values of Ag, Sb, W, Se, I and OrgC were 52%-74% of the national abundance. These are mostly beneficial elements for plant growth, which should be paid attention to.

② For the original data in the study area, the indexes with the coefficients of variation greater than 1 were Hg, Sb and Cl elements. The data had a high degree of dispersion, and the contents varied greatly. The indexes with coefficients of variation between 0.3 and 1.0 included Ag, Bi, Cd, Cr, Cu, Au, Ni, P, Pb, Sn, Th, W, Zn, Se, Br, I, C, S, OrgC, and CaO. The data had a relatively high degree of dispersion, and the contents changed greatly. Affected by anthropogenic pollution, the urban soil was obviously enriched with heavy metals, OrgC, N, P and other indicators. Meanwhile, due to coal combustion and metal smelting, Se and TFe2O3 were also enriched around the city.

③ The surface soil quality in the study area was generally good, with the sum of superior, good and medium accounting for 99.76% of the total area of the study area. The medium and poor soils were mainly distributed near chemical plants, thermal power plants and iron and steel coal mining enterprises in Laiwu District, Gangcheng District and the urban area of Jinan City. The polluting elements were mainly Hg, Cu, Cr, Cd, Ni, and Pb, which was closely related to industrial coal combustion in enterprises and discharge of dust, waste water and waste residue, to which relevant departments should pay attention.

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