The study area is located in the lower reaches of the Yellow River, with dense inland river networks. Geomorphological units are mainly alluvial, lacustrine and marine plains, with low terrain. The formation of soil is closely related to geological factors such as rivers, lakes and topography. The content of most soil elements in this area shows similar variation characteristics, and has a good correlation with the constant elements reflecting the soil geological background, such as SiO2 _ 2 and Al _ 2O _ 3, indicating that the content characteristics of most soil elements are controlled by the geological background.
By sampling and analyzing the suspended solids and filtered water, the source of elements in the water can be preliminarily determined, and it can be concluded that the new Wanfu River originated from the Yellow River and was influenced by agricultural planting. The filtered water and suspended solids in Xiaoqing River have a set of element combination characteristics of urban pollution. Due to the differences in the characteristics of element content and the formation background of major rivers, the causes of soil element anomalies along the river also have their own characteristics.
First, the cause analysis of element anomalies along the Yellow River.
According to the investigation results of three soil profiles in the upper, middle and lower reaches of the Yellow River in Shandong Province, the content of trace elements in soil is largely restricted by a large number of elements, and the profile distribution of trace elements fluctuates with the content of iron, aluminum, potassium, calcium and magnesium, and inversely with the content of silicon and sodium. As can be seen from Table 4- 10, the content of SiO2 _ 2 in the surface soil of three sections of the Yellow River is 7.3% lower than the regional average, and Na2 O is 0.44% lower, while Al2 O3, Fe2 O3, MgO, CaO and K2 O are 0.98%, 0.65%, 0.67%, 2.02% and 0.60% higher than the regional average respectively. Generally speaking, the higher the content of SiO2, the lower the content of al2o 3, fe2o 3 and MgO, and the more sandy and silty the soil texture is. On the contrary, the soil texture tends to be sticky. Through the discussion of three sections of the abnormal areas of heavy metals and other trace elements along the Yellow River, it can be inferred that the soil constant components are the important factors leading to the enrichment of trace elements and their abnormal reasons.
Figure 4-9a Element Distribution Map of Yucheng (TA) Section of Haihe River
Figure 4-9a Element Distribution Map of Yucheng (TA) Section of Haihe River
Figure 4-9a Element Distribution Map of Yucheng (TA) Section of Haihe River
Figure 4-9a Element Distribution Map of Yucheng (TA) Section of Haihe River
Table 4- 10 Comparison Table of Surface Soil Constant Components and Regional Background along the Yellow River Profile
Fig. 4- 10 Relationship between Trace Elements Content and Silica Content in Surface Soil of the Yellow River
Fig. 4- 10 and fig. 4- 1 1 are scatter plots of the relationship between some trace elements and the contents of silica and alumina, respectively. It can be seen from the figure that the contents of all trace elements except Hg are obviously linearly correlated with the contents of SiO _ 2 and Al2O3 (negatively correlated with SiO _ 2 and positively correlated with Al2O3), with only a few abnormal data points. The relationship between trace elements and Na2 O content is similar to that of SiO2, while the relationship between trace elements and Fe2 O3, MgO, CaO and K2 O is similar to that of Al2 O3.
Fig. 4- Relationship between trace elements and al2o 3 content in surface soil of Yellow River +0 1.
Table 4- 1 1 gives the regression coefficients of the linear fitting equations between trace elements and SiO2 _ 2 and Al _ 2O _ 3 in the surface soil of three sections of the Yellow River. As can be seen from the table, the fitting coefficients r2 of trace elements as, Cd, Co, Cr, Cu, F, Mn, Mo, Ni, Pb, V and Zn with SiO _ 2 and Al _ 2O _ 3 are all above 0.8, except that Cd is about 0.7, which shows that these elements are closely related to SiO _ 2 and Al _ 2O _ 3, and the trace elements are not. From the scatter plot, the slightly lower regression coefficient of Cd is due to the influence of individual abnormal values.
Table 4- Regression coefficient table of linear fitting equation of trace elements in surface soil with SiO _ 2 and Al _ 2O _ 3 (n = 88)
On the other hand, the regression coefficients r2 of B and Se are all around 0.4, which shows that their contents are related to the contents of SiO2 _ 2 and Al _ 2O _ 3, but also influenced by other factors. The regression coefficient r2 of Hg, P, N, S and other elements is small, and the S element is even 0.024, indicating that these elements are less affected by constant elements. From the analysis of biological and environmental geochemical properties of elements, Hg, P, N, S and other elements are not only the most typical pollution elements in the supergene environment, but also the most typical life elements.
Among the trace elements in deep soil determined in this survey, except for mercury, selenium, nitrogen, sulfur, boron, phosphorus and silicon dioxide, the regression coefficients of other elements are all greater than 0.8 (Table 4- 12), indicating that the content of these elements in deep soil is mainly controlled by the content of silicon dioxide in soil and to some extent by the soil texture.
Table 4- 12 Parameter Table of Regression Equation between Trace Elements and Silica in Deep Soil of Yellow River Section (n = 126)
From the profile distribution and statistical parameter characteristics of trace elements such as heavy metals along the upper, middle and lower reaches of the Yellow River in Shandong Province, it can be seen that the trace elements with abnormal distribution mainly include As, Cr, Co, Cr, Cu, F, Mn, Mo, Ni, Pb, V and Zn, with little abnormal contrast, showing the characteristics of being controlled by constant elements. It can be inferred that the formation of these anomalies is closely related to the characteristics of sediment composition in different time and space (the ratio of sandy to clay composition). In areas or soil layers with high sandy components and low clay components, the content of trace elements is relatively low, while the content of trace elements is in a high background or abnormal distribution state.
Compared with other trace elements, the linear regression coefficients of Hg, N and Se with the contents of soil constant components SiO2 _ 2 and Al _ 2O _ 3 are smaller, which reflects that the soil texture has little influence on these elements. From the scatter plot of element content, it can be seen that Hg, N, Se and other elements in the surface soil have no obvious correlation with SiO _ 2 and Al _ 2O _ 3, but after removing some abnormal points in the deep soil, Hg, N, Se and other elements have a good linear relationship with SiO _ 2 and Al _ 2O _ 3, so it can be inferred that these elements in the surface soil are obviously influenced by human activities or related to their active epigenetic geochemical activities. There is a nonlinear relationship between S and B in deep soil and soil texture, while the relationship between S and B in surface soil and soil texture becomes complicated, which is presumably related to the strong apparent geochemical activities and strong human interference of these two elements (both important life elements). No matter the surface soil or deep soil, its P content has nothing to do with soil texture, which reflects the unique geochemical properties of P element. The relationship between Hg, N, Se, S, B, N and soil texture is not as obvious as other trace elements, showing certain specificity, but these elements do not form large-scale and high-intensity anomalies along the Huang San strip profile, and most of them are single-point anomalies or low-contrast anomalies.
Based on the characteristics of trace element anomalies along Huang San, it is not difficult to draw a conclusion that the trace element anomalies in the soil along the Yellow River are closely related to the main components of the soil (reflecting the texture of the soil to some extent). Clay-rich soil conditions provide favorable conditions for the enrichment of various trace elements, while human pollution and lateral seepage of the Yellow River provide sources of trace elements.
Secondly, the causes of element anomalies along Xiaoqing River are analyzed.
From the horizontal and vertical distribution of soil element content in two sections along Xiaoqing River, it can be seen that trace elements in XA section are greatly influenced by urban polluted water and Jinan iron and steel plant pollution, showing obvious surface enrichment of Hg, Se, Cu and other elements, and the intensity of sampling points near Xiaoqing River and Jinan iron and steel plant is abnormal; The distribution of trace elements in XB section is discontinuous and abnormal, and the relationship between trace element abnormality and macro element distribution is similar to that along the Yellow River section, showing the characteristics of being restricted by soil texture.
Table 4- 13 compares the average contents of elements in the surface soil and deep soil of the two sections. As can be seen from the data in the table, the contents of Hg and Se in the surface soil of XA section are obviously higher than those of XB section, section along the Yellow River and regional surface soil, and the contents of Cd, Cr, Cu and P are relatively high, indicating that XA section has been affected by human pollution.
Table 4- 13 XA and XB average content of elements
sequential
Note: The content units of silica, alumina, ferric oxide, magnesium oxide, calcium oxide, sodium oxide and K2O are%; The content unit of other trace elements is 10-6.
The average content of most trace elements in XB topsoil is not much different from that in Yellow River topsoil, but SiO2 _ 2 and Na2 O in XB topsoil are far below the regional average, while Al _ 2O _ 3, Fe _ 2O _ 3, MgO, CaO and K2 O are higher than the regional average. In the deep soil of XB section, SiO2 _ 2 and Na2O are lower than those of the Yellow River, while Al _ 2O _ 3, Fe _ 2O _ 3, MgO, CaO and K2O are higher than those of the Yellow River, and the content of trace elements is also higher than that of the Yellow River, which reflects that the content of trace elements is restricted by a large number of elements.
Through the regression analysis of soil element content, it can be found that there is no significant linear relationship between trace elements and SiO2 _ 2 content in the surface soil of XA profile. After excluding some high-value points, the linear relationship between arsenic, vanadium, manganese, nickel and cobalt and silica is good, but the linear relationship between most trace elements and silica is still not good. It is worth noting that, except for a few elements such as Cd, the relationship between trace elements and SiO2 _ 2 content in the deep soil of XA profile is also very poor, even worse than that in the surface soil.
During field sampling, it was found that most farmland along the section was irrigated by Xiaoqing River, and it was inferred that there was an abnormal relationship between trace elements in deep soil and SiO2 _ 2 content. On the one hand, it may be related to the leaching of polluted elements from the surface to the deep soil after irrigation with Xiaoqing River polluted water. On the other hand, the polluted Xiaoqing River water may also affect the quality of agricultural shallow groundwater and the content of elements in deep soil on both sides of the strait through lateral seepage.
From Table 4- 14, it can be seen that the linear relationship between trace elements and SiO _ 2 content in the surface soil of XB section is good, and the linear relationship between some elements such As As, Cd and F and SiO _ 2 content is even better than that in the surface soil of the Yellow River. The linear relationship between trace elements and SiO _ 2 content in deep soil of XB profile is also good, but the linear relationship between trace elements and SiO _ 2 content is not as good as that in surface soil, and the regression coefficient between trace elements and SiO _ 2 is generally significantly lower than that in deep soil of the Yellow River. In general, the influence of human disturbance on deep soil is relatively weak, and its content should be closer to the natural background, and its relationship with soil main components and texture should be better than that of surface soil. The linear relationship between trace elements and SiO2 _ 2 content in deep soil in XB section is poor, which may be due to Xiaoqing River and Zhimai River irrigation in farmland near this section. It is speculated that trace elements in irrigation water are leached into deep soil similar to those in XA section.
Table 4- 14 Linear Fitting Regression Coefficient Table of Trace Elements and SiO _ 2 in XB Section and Yellow River Section of Xiaoqing River
To sum up, the Jinan section of Xiaoqing River (XA section) is strongly influenced by human activities, which is characterized by strong surface enrichment of elements such as Hg, Se and Cu, and most trace elements have a poor relationship with the main soil components such as SiO2 _ 2 and Al _ 2O _ 3 (reflecting soil texture). However, the surface soil of XB section in the lower reaches of Xiaoqing River is less affected by artificial superposition. The characteristics of trace elements content in deep soil show that both profiles have a certain degree of man-made superimposed influence, and the man-made influence of Jinan (XA) profile is greater than that of Dongying (XB) profile, which may be related to the irrigation of Xiaoqing River and the interaction between river water and shallow groundwater.
Thirdly, the cause analysis of element anomalies along the coast of Tu Hai.
Figures 4- 12 and 4- 13 show the dispersion distribution of some trace elements and silica contents in the surface and deep soil of Haihe River. As can be seen from the figure:
Fig. 4- 12 relationship between trace elements and silica content in surface soil of Yucheng section of Tu Hai.
1) Similar to the section along the Yellow River, most trace elements in the surface soil of Yucheng section in Tu Hai are negatively correlated with the content of SiO2 _ 2.
2) Except As, Ni and other elements, the correlation between deep soil and SiO _ 2 is more obvious than that of surface soil, and there is a good linear relationship between Hg and SiO _ 2 in deep soil of this profile.
3) Compared with several sections along the Yellow River, the correlation between most trace elements and SiO2 _ 2 in TA section of Tuhai River is lower than that in Yellow River, which indicates that the trace element content in Ta section of Tuhai River is not only controlled by the main composition and texture of soil, but also related to human pollution.
4) Compared with the two sections of Xiaoqing River, the TA section of Tuhai River has a good correlation with SiO2 _ 2, especially the Jin 'an (XA) section of Xiaoqing River.
The correlation between trace elements in the sections of the Yellow River, Tu Hai and Xiaoqing River and the main components of soil, such as SiO2 _ 2, reflects the intensity of man-made pollution superposition in each section.
Fig. 4- 13 relationship between trace elements and SiO _ 2 content in deep soil in Yucheng section of Tu Hai.