CN111751513A - Analysis method for analyzing heavy metal accumulation and morphological characteristics of profile soil of rice field to analyze main pollution source of heavy metal - Google Patents
Analysis method for analyzing heavy metal accumulation and morphological characteristics of profile soil of rice field to analyze main pollution source of heavy metal Download PDFInfo
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Abstract
The invention relates to a method for analyzing main pollution sources of heavy metals in profile soil of a rice field by means of accumulation and morphological characteristics analysis of the heavy metals, which comprises the following steps: the method comprises the steps of firstly, collecting a sample; secondly, pretreating a sample; determining and analyzing a sample; fourthly, evaluating the heavy metal pollution; fifthly, carrying out statistical analysis on the data. The invention provides an analysis method for evaluating the pollution risk of the paddy field soil in the area by adopting a single pollution index and a comprehensive pollution index and analyzing the main possible pollution source in the area with unknown pollution source by utilizing the morphological distribution characteristics of the heavy metal in the soil in the area with known pollution source.
Description
Technical Field
The invention belongs to the field of ecological environment protection, relates to a soil heavy metal source analysis technology, and particularly relates to an analysis method for analyzing main pollution sources of heavy metals by heavy metal accumulation and morphological characteristics of profile soil of a rice field.
Background
Under the action of natural cultivation, leaching and the like, heavy metals accumulated in soil can migrate transversely and longitudinally, so that the heavy metals present different accumulation characteristics and morphological distributions in the soil section. Research shows that the accumulation and morphological distribution characteristics of heavy metals in profile soil are influenced by a pollution source, the surface enrichment phenomenon of heavy metals such as Cd, Pb, Cu and the like in the rice field soil of the Gannan tungsten mine area is obvious, and the bottom enrichment phenomenon of heavy metals in a soil profile near a new mine opening of the Fenghuang lead-zinc mine area is obvious; in the surface soil of the paddy field in the polluted area of the copper smelting plant, the effective Cu and Cd are respectively and obviously related to the effective Zn and Pb; the application of farmyard organic fertilizer can obviously increase the total amount and exchangeable state proportion of Cu and Zn in surface soil.
At present, researches on accumulation characteristics and form distribution of heavy metals in profile soil of a paddy field in a long puddle area are less, particularly researches under the influence of different pollution sources indicate that the heavy metals in the paddy field soil near a Hunan lead-zinc mining area are mainly concentrated on the surface layer, and the content of available Cd in the paddy field soil can be enhanced by exogenous heavy metals and the mobility of the Cd in the paddy field soil.
The invention provides a preliminary identification method for mainly possible pollution sources based on accumulation and morphological characteristic analysis of heavy metal in paddy field profile soil, and provides a theoretical basis for preventing and treating polluted soil from sources by taking accumulation characteristics and morphological distribution rules of six heavy metal elements (Cd, Pb, Cu, Zn, Cr and Ni) in normal fertilization (organic fertilizers such as pig manure) areas, pig farm biogas slurry irrigation areas, lead-zinc mining areas, industrial areas and other nearby paddy field profile soil without obvious pollution sources in Hunan Changtai lake areas as research objects.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide an analysis method which adopts a single pollution index and a comprehensive pollution index to carry out risk evaluation on the paddy field soil in the area and utilizes the accumulation and morphological distribution characteristics of the soil heavy metal in the area with known pollution source to analyze the main possible pollution source in the area with unknown pollution source.
The technical problem to be solved by the invention is realized by adopting the following technical scheme:
an analysis method for analyzing heavy metal accumulation and morphological characteristics of profile soil of a rice field to analyze main pollution sources of heavy metals comprises the following steps:
first sample collection
Collecting 11 soil sections, wherein the serial numbers of the soil sections are CS-1 to CS-11, the serial numbers of the soil sections are CS-1 to CS-7, the serial numbers of the soil sections are known as pollution sources, the serial numbers of the soil sections are CS-8 to CS-11, the serial numbers of the soil sections are unknown as pollution sources, each section is sampled in seven layers, the sampling is respectively 0-10cm, 10-20cm, 20-30 cm, 30-40 cm, 40-60 cm, 60-80cm and 80-100cm, and 77 soil samples are collected;
sample pretreatment
After being air-dried, collected soil samples are ground, sieved and bagged for measuring the pH and TOC of the soil and analyzing the total amount and the form of heavy metals Cd, Pb, Cu, Zn, Cr and Ni;
determination and analysis of sample
The pH value of the soil adopts 0.01mol/L CaCl2Fully oscillating the solution for 30min, standing for 1h, measuring by using a pH meter, removing inorganic carbon in soil by using 2mol/L HCl for soil TOC, and measuring by using a TOC measuring instrument;
the total amount of different heavy metals in the soil is HNO3-H2O2The method comprises the steps of digestion, continuous extraction of chemical forms of the heavy metals in the soil by adopting a BCR extraction method, and finally measuring the total amount of the six heavy metals of Cd, Pb, Cu, Zn, Cr and Ni and the content of each form by using inductively coupled plasma physique emission spectrum;
fourth heavy metal pollution evaluation method
Adopting a soil pollution index method, and adopting the following calculation formula:
Pi＝Ci/Si(1)
in the formula: piIs the pollution index of a single pollutant;
p is the composite pollution index of various pollutants;
Ci(mg/kg) is the measured concentration of contaminant i in the soil, Si(mg/kg) is the evaluation standard concentration of contaminant i;
n is the number of contaminants;
fifthly, carrying out statistical analysis on the data.
In addition, CS-1 and CS-2 in the sample collection and pretreatment steps are collected from rice fields without obvious pollution sources and normally applied organic fertilizers in Changsha county, CS-3 is collected from rice fields irrigated by biogas slurry near pig farms in Liuyang city, CS-4, CS-5 and CS-6 are collected from rice fields near lead and zinc mining areas in the southwest of Longling city and 10 kilometers from sampling points, CS-7 is collected from rice fields near plastic factories and ceramic factories in the east of Longling city, CS-8 to CS-11 are collected based on GPS positioning points and are randomly sampled in the Changsha county, the Wancheng county and the Hunan county, so that CS-1 to CS-7 are known profiles of pollution sources, and CS-8 to CS-11 are unknown profiles of pollution sources.
Moreover, the soil sample is sieved with a mesh size of less than 2mm in the sample pretreatment step.
Furthermore, CaCl in the sample determination and analysis step2The soil-liquid ratio in the solution treatment is 1: 5.
Moreover, the overall pollution index P is graded as follows:
furthermore, statistical analysis of data statistical analysis was performed using Microsoft Excel 2013 and SPSS 23.0, data processing and plotting was performed using Origin 9, and the sample plot was plotted using Arcgis 10.2
The invention has the advantages and positive effects that:
1. the method takes a long plant pond area as a typical area, selects paddy field soil as a research object, and collects 11 soil profiles (numbered from CS-1 to CS-11) in 8 months in 2017. CS-1 and CS-2 are collected from rice fields without obvious pollution sources and normally applied organic fertilizers in Changsha county, CS-3 is collected from rice fields irrigated by biogas slurry near pig farms in Liuyang city, CS-4, CS-5 and CS-6 are collected from rice fields near lead and zinc mining areas (about 10 kilometers from sampling points) in southwest of Longling city, CS-7 is collected from rice fields near industrial areas such as plastic plants and ceramic plants in east of the Longling city, CS-8 to CS-11 are sampled randomly in the rice fields in Changsha county, Tancheng county and Hunan quan county based on GPS positioning point selection, so that CS-1 to CS-7 are known profiles of pollution sources, and CS-8 to CS-11 are unknown profiles of pollution sources.
2. The method for evaluating the heavy metal pollution in the method adopts a soil pollution index method: the soil environment quality index also refers to a soil environment quality index, and the soil environment quality can be quantitatively described by taking a regional soil background value or a regional soil background value as an evaluation standard. The single factor index method is a relative dimensionless index used when evaluating the soil and crop pollution degree or soil environment quality grade, can relatively comprehensively reflect the pollution degree of each pollution, and the single pollution index (Pi) is the grade of the soil pollution degree or soil environment quality represented by a single factor; the comprehensive pollution index method is based on a single-factor pollution index and obtains the comprehensive pollution index through a series of calculations.
3. The following conclusions can be obtained by the method of the invention: compared with the soil background value of the region, Cd, Pb and Zn in the surface soil of the research region are accumulated to a certain degree, wherein the average content of Cd exceeds the soil pollution risk screening value of the national soil environment agricultural land, and the accumulation degree of Cd, Pb, Zn and the like is closely related to the type of a pollution source. Secondly, the high values of the single pollution indexes of Cd and Pb are concentrated on the surface layer, and slight or slight accumulation and few moderate accumulation appear at part of point positions; zn is mainly accumulated slightly and accumulated moderately, and is extremely accumulated severely, so that pollution risks exist in individual regions; and the comprehensive pollution index evaluation result shows that the surface soil in the research area is heavily or moderately accumulated. Thirdly, TOC in soil near a normal fertilization area and a pig farm is obviously or extremely obviously related to organic combined state Cu and Zn; exchangeable Pb in soil near a lead-zinc ore polluted area and exchangeable Cd and Zn show extremely obvious correlation; only the exchangeable Pb and the exchangeable Cd are in extremely obvious correlation near the industrial area, so that the main sources of the heavy metals in the soil can be preliminarily identified by means of the main occurrence forms and the correlation of the heavy metals in the soil.
In conclusion, the invention provides an analysis method for preliminarily identifying main possible pollution sources based on the accumulation and morphological characteristics of heavy metal in profile soil of a paddy field, and provides a theoretical basis for preventing and treating polluted soil from sources, wherein the analysis method takes the accumulation characteristics and morphological distribution rules of six heavy metal elements (Cd, Pb, Cu, Zn, Cr and Ni) in profile soil of the paddy field nearby such as a normal fertilization (organic fertilizers such as pig manure) area, a pig farm biogas slurry irrigation area, a lead-zinc mining area, an industrial area and the like without obvious pollution sources in a long pond area in Hunan province as research objects. The method effectively overcomes the defects of the prior art, and provides an analysis method which adopts a single pollution index and a comprehensive pollution index to carry out risk evaluation on the paddy field soil in the area and utilizes the accumulation and morphological distribution characteristics of the heavy metals in the soil in the area with known pollution sources to analyze the possible pollution sources in the area with unknown pollution sources.
Drawings
FIG. 1 is a soil profile sampling profile for the method of the present invention;
FIG. 2 is a graph showing the trend of the content of pH, TOC and each heavy metal in 11 sections of the sampled soil along with the change of the depth of the soil in the method of the invention;
FIG. 3 is a profile soil comprehensive evaluation index distribution diagram and a profile surface and subsurface soil heavy metal single-factor index distribution diagram of 11 profiles in the method of the present invention;
FIG. 4 is a graph showing the morphology of heavy metals in soil of seven sections of known sources of contamination in the method of the present invention;
FIG. 5 is a graph showing the distribution of heavy metal forms in soil of four sections of unknown pollution sources in the method of the present invention.
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
Hunan province is one of the most serious provinces of heavy metal pollution in China. In 30 important control areas related in the competitive assessment and examination of national heavy metal pollution control key areas, 11 Hunan provinces are monopolized, and the 10 important control areas are mainly distributed in non-ferrous metal mining areas and Hunan river watersheds. The Changan Tan area is used as a core area for economic development and urbanization in Hunan province, and the industrial structure of the Changan Tan area is mainly the traditional manufacturing industries such as nonferrous metallurgy, mechanical manufacturing, chemical raw materials and the like, so that the Changan Tan area becomes a main area seriously polluted by people, and heavy metals such as Cd, Pb, Zn, Cr and the like in the paddy field soil of the area are accumulated to different degrees.
The invention provides an analysis method for analyzing heavy metal accumulation and morphological characteristics of profile soil of a rice field to analyze main possible pollution sources of heavy metals by taking the accumulation characteristics and morphological distribution rules of six heavy metal elements (Cd, Pb, Cu, Zn, Cr and Ni) in profile soil of the rice field nearby such as a normal fertilization (organic fertilizers such as pig manure) area, a pig farm biogas slurry irrigation area, a lead-zinc mining area, an industrial area and the like without obvious pollution sources in a long pond area in Hunan province.
1 materials and methods
1.1 overview of the study region
The long Tantang city group is located at the east of Hunan province (110 degrees 53 '-114 degrees 15' E, 26 degrees 03 '-28 degrees 40' N), and has an area of about 2100 km2. The three cities are distributed adjacently in a shape like Chinese character 'pin' in the downstream of Hunan river, are core areas of economic development and urbanization in Hunan province, and are important urban dense areas in the middle of China. The region is in red-yellow soil zone, the difference of air temperature and rainfall is not obvious, the rock types and the matrix of the formed soil are basically consistent, and the soil mainly comprises red soil, purple soil, red clay and moisture soil, and is acid soil.
1.2 sample Collection and Pre-treatment
Taking a long plant pond area as a typical area, selecting paddy field soil as a research object, and collecting 11 soil profiles (numbered from CS-1 to CS-11) in 8 months in 2017. CS-1 and CS-2 are collected from rice fields without obvious pollution sources and normally applied organic fertilizers in Changsha county, CS-3 is collected from rice fields irrigated by biogas slurry near pig farms in Liuyang city, CS-4, CS-5 and CS-6 are collected from rice fields near lead and zinc mining areas (about 10 kilometers from sampling points) in southwest of Longling city, CS-7 is collected from rice fields near industrial areas such as plastic plants and ceramic plants in east of Longling city, CS-8 to CS-11 are based on GPS positioning point selection, and are randomly sampled in rice fields in Changsha county, Tancheng county and Hunan county, so that CS-1 to CS-7 are known profiles of pollution sources, and CS-8 to CS-11 are unknown profiles of pollution sources. The distribution of sample points is shown in figure 1. Each section is sampled in seven layers (0-10cm, 10-20cm, 20-30 cm, 30-40 cm, 40-60 cm, 60-80cm and 80-100cm), and 77 soil samples are collected. After being air-dried, the soil is ground, sieved (2 mm) and bagged for measuring the total amount of heavy metals (Cd, Pb, Cu, Zn, Cr and Ni), the TOC and the pH of the soil and analyzing the form of heavy metal elements.
1.3 sample determination and analysis
The pH value of the soil adopts 0.01mol/L CaCl2The solution (soil-to-liquid ratio: 1:5) was sufficiently shaken for 30min, and then left to stand for 1h, followed by measurement with a pH meter (Mettler Toledo, Multi parameter Instrument). Soil TOC was determined using a TOC analyzer (Analytik Jena muti N/C3100) after removing inorganic carbon from soil with 2mol/L HCl.
The heavy metal in the soil is dissolved and removed by adopting HNO3-H2O2The method comprises digestion, continuous extraction of soil heavy metal chemical form by improved BCR three-step extraction method, and comprises exchangeable state (F1), reducible state (F2), oxidizable state (F3) and residue state (F4). And finally, measuring the contents of the six heavy metals of Cd, Pb, Cu, Zn, Cr and Ni by using inductively coupled plasma (ICP-OES, Optima 5300DV) spectrometry.
1.4 heavy Metal pollution evaluation method
Soil pollution index method: the soil environment quality index also refers to a soil environment quality index, and the soil environment quality can be quantitatively described by taking a regional soil background value or a regional soil background value as an evaluation standard. The single factor index method is used to evaluate the soil and crop pollution courseA relative dimensionless index used in the soil or soil environment quality grade can relatively comprehensively reflect the pollution degree of each pollution and a single pollution index (P)i) The soil pollution degree or the soil environment quality grade is expressed by a single factor; the comprehensive pollution index method is based on a single-factor pollution index, and obtains a comprehensive pollution index (P) through a series of calculations, wherein the calculation formula is as follows:
Pi＝Ci/Si(1)
in the formula: piIs the pollution index of a single pollutant;
p is the composite pollution index of various pollutants;
Ci(mg/kg) is the measured concentration of contaminant i in the soil, Si(mg/kg) is the evaluation standard concentration of contaminant i;
n is the number of contaminants;
the overall pollution index P is graded as shown in table 1 below.
TABLE 1 grading Standard for soil environmental quality evaluation
1.5 statistical analysis of data
Statistical data analysis was performed using Microsoft Excel 2013 and SPSS 23.0, data processing and mapping was performed using Origin 9, and the sample plot was plotted using Arcgis 10.2.
2 results and discussion
2.1 Change characteristics of heavy Metal content in soil Profile
As shown in FIG. 2, the pH of the soil on the section taken varies from 4.33 to 6.84, wherein the point with pH less than 6.5 accounts for 90.9% (70/77), the point is mainly concentrated in 5.0 to 6.5, the soil belongs to acid soil, and the pH of the soil tends to increase along with the increase of the depth of the soil layer (FIG. 2 a). The TOC content of the soil shows a significant downward trend (FIG. 2b), because the topsoil (0-20cm) is susceptible to production activities such as fertilization and irrigation, and surface biology, climatic conditions, etc., and therefore the TOC accumulation phenomenon exists in the topsoil.
The average contents of Cd, Pb, Cu, Zn, Cr and Ni in the surface soil (0-10cm) were 0.78, 54.51, 43.63, 158.66, 106.16 and 23.33mg/kg, respectively. Relative to the background value of heavy metals (Cd: 0.5 mg/kg; Pb: 38.1 mg/kg; Cu: 95 mg/kg; Zn: 60.3 mg/kg; Cr: 64.9 mg/kg; Ni: 29.4mg/kg) in soil in a pond area with long plants, other heavy metals in a research area except Cu and Ni are accumulated to a certain degree, and the average content of Cd exceeds the soil pollution risk screening value (Cd: 0.3mg/kg, GB 15618-2018) of the soil pollution in the national soil environment agricultural land.
As the depth of the section increases, the average contents of the heavy metal elements except Cr and Ni are reduced to different degrees, but the average contents of Cd, Pb and Zn in the subsurface (10-20cm) soil are still 4.0%, 15.5% and 93.9% higher than the local background value respectively, and the average content of Zn in the deep (80-100cm) soil is still as high as 77.29mg/kg (figure 2 f). In a general view (fig. 2 c-fig. 2h), Cd, Zn and Pb in the soil of 0-20cm in the research area are enriched to different degrees, the average content of the Cd, Zn and Pb is 1.78-5.03 times of the content of deep soil, and the enrichment degree of Zn is relatively high.
Compared with the research result of heavy metal accumulation characteristics of surface soil of farmland in 2008, the accumulation degree of Zn and Cr is increased, especially Zn is increased by 2.57 times compared with that of 2008; the average contents of the remaining four heavy metals such as Pb and the like are reduced, and particularly, the contents of Cd and Cu are reduced by 50.34% and 75.69% respectively.
Specifically, the Cd contents in the surface soil of CS-4, CS-5, CS-6 and CS-11 are obviously high (all are more than 1.0mg/kg, and the highest content is 1.66mg/kg)Indicating significant point source contamination; meanwhile, the surface soil has a significantly higher content of Cd and a smaller standard deviation (0.54) relative to subsurface and deep soils (table 2), indicating that the accumulation characteristics of Cd in the surface soil of the study area have integrity. For Zn, sampling points (such as CS-3, CS-4 and CS-5) which are partially adjacent to a pig farm and a mining area have higher Zn content (all are larger than the background value of the area and reach 421.47 mg/kg); meanwhile, the standard deviation of Zn in surface soil and subsurface soil is obviously higher (Table 2), further explaining that Zn generally accumulated in the surface soil of the region is caused by artificial pollution. Although the average value of Pb in the research area is low, Pb in topsoil of CS-4, CS-5, CS-6 and CS-11 presents a remarkably high value (up to 141.24 mg/kg), wherein CS-4, CS-5 and CS-6 are close to a lead-zinc ore mining and smelting area, so that the content of Pb, Zn and Cd in topsoil of a nearby agricultural area is remarkably high. Similarly, the mean value of Cu in the study area was also lower, but sample CS-3 was near the pig farm, with biogas slurry irrigation causing abnormally high levels of Cu and Zn in the profile. Therefore, elements such as Cd, Zn, Pb and the like obviously accumulated in the rice field soil of the research area are closely related to the type of the pollution source. Previous researches also indicate that the types of pollution sources have obvious influence on the accumulation characteristics of heavy metals in soil, for example, Pb, Zn and Cd are used as main pollution elements of lead-zinc tailings, mercury ores and coal mines, so that the heavy metals such as Pb, Cd, Zn and the like in the soil of rice fields near mining areas are obviously accumulated; long-term application of pig biogas residues causes accumulation of As, Cd, Cu and Zn in paddy soil[23](ii) a The content of Cd, Pb and the like in soil near roads and factories is 2-6 times higher than the background value]。
Statistical characteristics of heavy metal content of soil with 211 sections in table
2.2 evaluation of heavy Metal contamination of surface soil of different profiles
Compared with surface soil, the single pollution indexes of heavy metals in subsurface soil are reduced (fig. 3a and 3b), which indicates that the surface soil is greatly influenced by artificial pollution. The average single-item pollution index of Zn is more than or equal to 2, the slight accumulation and the medium accumulation are taken as main materials, and the severe accumulation occurs in few sampling points. Cd. The average single pollution index of Pb is more than 1, high values are mainly concentrated in surface soil, slight or light accumulation occurs in part of point sites, and only few points are moderate accumulation.
As the soil depth increases, the mean value of the comprehensive pollution indexes of the 11 sections is in a descending trend. At 60-80cm, due to the accumulation of Pb, Cr and other elements, the comprehensive pollution indexes of CS-2, CS-3 and CS-4 are all larger than 2, so that the average value of the comprehensive pollution indexes is increased. According to the comprehensive pollution index evaluation result, more than half point of the surface soil reaches the medium accumulation and above. However, the conclusion of the comprehensive pollution index method is often influenced by the point positions with high heavy metal content in the sampling points, for example, the Pb and Zn contents of partial sections in the research area are very high, so that the evaluation result in the area is light and medium accumulation, and even reaches heavy accumulation. In general, three elements of Cd, Pb and Zn are accumulated to a certain degree, and pollution risks exist in individual areas.
2.3 morphological distribution characteristics of heavy metal elements in the profile under the influence of different pollution sources
The morphological distribution characteristics of heavy metals in 11 sections of soil in the study area are shown in fig. 4 and 5. In general, the same heavy metal element has similar morphological change trend. Cd mainly exists in exchangeable state, especially has the highest proportion in surface soil, but the exchangeable state Cd is also easy to change under the influence of external environment, for example, Cd can be converted to lower-activity organic state under long-term flooding condition; however, as the profile deepens (the pH of the soil rises), the ratio of the Cd in the carbonate binding state to that in the iron-manganese oxide binding state increases. Pb is mainly in a reducible state and a residual state. Cu and Zn are mainly present in the form of residue (more than 50%), wherein the specific gravity of the organic binding state in the CS-8 and CS-9 sections is increased, possibly related to the section organic matter content and the soil physicochemical property with relatively high soil pH.
Research indicates that heavy metals from different sources have different occurrence forms. Cu and Zn are the most main accumulated elements in the organic fertilizer and mainly exist in an organic combination state; in lead-zinc mine areas, Cd has the affinity to the geochemistrySulfur, so Cd can substitute like a homogeneous image for Zn to enter Zn-bearing mineral]The method is characterized in that the contents of Cd, Pb and Zn in atmospheric particulates discharged by mining and smelting activities are high (CS-4, CS-5 and CS-6 have the same obvious accumulation of the three elements in surface soil), the atmospheric particulates are mainly in exchangeable states, the industrial areas are influenced by different industrial types, production modes and the like, the types and components of generated pollutants are complex, the main heavy metal elements and the forms thereof are difficult to determine, previous researches indicate that the form distribution characteristics of heavy metals in the soil are obviously influenced by the pollution sources, Pb in weak acid extraction states of surface soil of certain lead-zinc mine areas in southwest has high correlation with Zn and Cd respectively, Cu, Zn and Cd contents in farmland soil polluted by pig manure and pig manure biogas slurry are obviously increased, the contents of exchangeable Cu, Zn and organic matters are obviously increased, the contents of exchangeable states Cu, Zn and Cd are obviously increased, the known profiles of the pollution sources in the research, the research are taken as an example, if the profiles of the pollution sources are related to oxidizable states of Cu3 and Zn3 and the exchangeable states of Pb (1) and the exchangeable states of Pb and the exchangeable states of the industrial truck pollution sources respectively, the pollution sources are taken as a cross section map, the cross section of a normal truck bed shows that the environmental pollution source is similar to a normal truck bed (CS-2, a cross section of a truck bed (CS-2, a truck bed shows a cross section of a normal truck bed (CS-2) and a cross section of a truck bed (7, a cross section of a truck bed is similar section of a truck bed, a truck), a truck bed is similar section of a truck bed, a truck bed is similar section of a truck bed is similar truck bed, a truck bed is similar to a truck bed, a truck bed is similar to a truck bed, a truck bed.
Although studies have shown that the total amount of heavy metals in soil under the influence of different pollution sources also shows a certain correlation, such as: significant correlation exists among surface soil Hg, Pb, Zn and the like near a lead-zinc mining area of the south lake Zhou; cr, Cd and Hg in soil of a certain tungsten ore area of the Hunan Xianghualing mountain show extremely obvious positive correlation, and Pb and Zn show obvious positive correlation; the contents of Cd, Cu, Zn and Pb in farmland soil in the great Baoshan mining area are in positive correlation with each other, and the contents of TOC and Cu and Zn are in extremely significant correlation under the influence of biogas slurry irrigation (CS-3) in a pig farm in the research (Table 3), but if the total amount of each element is used for correlation analysis, the sections affected by different pollution sources cannot be well distinguished (Table 3).
TABLE 3 Pearson's correlation coefficient for total amount of elements and morphology in different sections
Significant correlation; significant correlation of the poles
As mentioned above, the morphological distribution characteristics of heavy metal elements can provide useful information for identifying the main pollution source of heavy metals in soil. Taking the section of the study in which the source of contamination is unknown as an example (table 3), it can be found that: the forms of the elements in the section CS-8 have no obvious correlation, and the total amount of each element is relatively lowest, so that no obvious pollution source exists; the TOC in section CS-9 showed significant (0.83) and very significant (0.98) correlations with Cu3 and Zn3, respectively, and the correlations of Pb1 with Cd1 and Zn1 were not strong, and were in agreement with the characteristics of section CS-2 as a whole, indicating that the effect of organic fertilizer application may be greater; the total amount of Cd, Pb, Cu and Zn in the section CS-11 is relatively highest, while Pb1 is very significantly (0.91) and significantly (0.83) related to Cd1 and Zn1, respectively, while the very significant correlation between TOC and Cu3 (0.94) may be due to the relatively high organic content (31.22g/kg) in the soil of the section and the tendency of Cu to bind with oxidizable substances (such as organics and sulfides), so CS-11 may be more affected by mining smelting; for the section CS-10, since the contents of the elements are centered, Pb1 and Cd1 and TOC and Cu3 are significantly related (0.86 and 0.81 respectively), and the characteristics are not obvious, so that the main pollution source is difficult to judge.
Therefore, the main occurrence form and the correlation of the heavy metal in the soil can be used for preliminarily judging the main source of the heavy metal in the soil.
3 conclusion
a) The average content of Cd, Pb, Cu and Zn in surface soil of a long pond area is higher than a local background value, and the average content of Cd exceeds the soil pollution risk screening value of national soil environment agricultural land (GB 15618-2018). Meanwhile, Zn is still accumulated in the deep soil, and the average content is 77.29 mg/kg.
b) The high values of the single pollution indexes of Cd and Pb are concentrated in surface soil, slight or mild accumulation occurs in part of point positions, and only a few point positions are moderate accumulation; zn is mainly accumulated in a slight way and a medium way, and is heavily accumulated in a few sampling points, so that pollution risks exist in individual regions.
c) The main sources of heavy metals in the soil can be preliminarily identified by means of the main occurrence forms and the relativity of the heavy metals in the soil.
Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the embodiments disclosed.
Claims (6)
1. A method for analyzing the accumulation of heavy metals in profile soil of a rice field and analyzing the main pollution sources of the heavy metals by morphological characteristics is characterized by comprising the following steps: the method comprises the following steps:
first sample collection
Collecting 11 soil sections, wherein the serial numbers of the soil sections are CS-1 to CS-11, the serial numbers of the soil sections are CS-1 to CS-7, the serial numbers of the soil sections are known as pollution sources, the serial numbers of the soil sections are CS-8 to CS-11, the serial numbers of the soil sections are unknown as pollution sources, each section is sampled in seven layers, the sampling is respectively 0-10cm, 10-20cm, 20-30 cm, 30-40 cm, 40-60 cm, 60-80cm and 80-100cm, and 77 soil samples are collected;
sample pretreatment
After being air-dried, collected soil samples are ground, sieved and bagged for measuring the pH and TOC of the soil and analyzing the total amount and the form of heavy metals Cd, Pb, Cu, Zn, Cr and Ni;
determination and analysis of sample
The pH value of the soil adopts 0.01mol/L CaCl2Fully oscillating the solution for 30min, standing for 1h, measuring by using a pH meter, removing inorganic carbon in soil by using 2mol/LHCl for soil TOC, and measuring by using a TOC measuring instrument;
the total amount of different heavy metals in the soil is HNO3-H2O2The method comprises the steps of digestion, continuous extraction of chemical forms of the heavy metals in the soil by adopting a BCR extraction method, and finally measuring the total amount of the six heavy metals of Cd, Pb, Cu, Zn, Cr and Ni and the content of each form by using inductively coupled plasma physique emission spectrum;
fourth heavy metal pollution evaluation method
Adopting a soil pollution index method, and adopting the following calculation formula:
Pi＝Ci/Si(1)
in the formula: piIs the pollution index of a single pollutant;
p is the composite pollution index of various pollutants;
Ci(mg/kg) is the measured concentration of contaminant i in the soil, Si(mg/kg) is the evaluation standard concentration of contaminant i;
n is the number of contaminants;
fifthly, carrying out statistical analysis on the data.
2. The method for analyzing the main pollution sources of heavy metals by the accumulation and morphological characteristics of the heavy metals in the profile soil of the rice field according to claim 1, wherein the method comprises the following steps: in the sample collection and pretreatment steps, CS-1 and CS-2 are collected from rice fields without obvious pollution sources and normally applied organic fertilizers in Changsha county, CS-3 is collected from rice fields irrigated by biogas slurry near pig farms in Liuyang city, CS-4, CS-5 and CS-6 are collected from rice fields near Pb-Zn mining areas in southwest of Changshan city and 10 kilometers from sampling points, CS-7 is collected from rice fields near plastic plants and ceramic plants in east of Changshan city, CS-8 to CS-11 are selected based on GPS positioning, and are randomly sampled in Changsha county, Tancheng county and Hunan county, so that CS-1 to CS-7 are known profiles of pollution sources, and CS-8 to CS-11 are unknown profiles of pollution sources.
3. The method for analyzing the main pollution sources of heavy metals by the accumulation and morphological characteristics of the heavy metals in the profile soil of the rice field according to claim 1, wherein the method comprises the following steps: and in the sample pretreatment step, the soil sample is sieved by a sieve mesh of less than 2 mm.
4. The method for analyzing the main pollution sources of heavy metals by the accumulation and morphological characteristics of the heavy metals in the profile soil of the rice field according to claim 1, wherein the method comprises the following steps: CaCl in sample determination and analysis step2The soil-liquid ratio in the solution treatment is 1: 5.
5. The method for analyzing the main pollution sources of heavy metals by the accumulation and morphological characteristics of the heavy metals in the profile soil of the rice field according to claim 1, wherein the method comprises the following steps: the classification of the comprehensive pollution index P is as follows:
6. the method for analyzing the main pollution sources of heavy metals by the accumulation and morphological characteristics of the heavy metals in the profile soil of the rice field according to claim 1, wherein the method comprises the following steps: statistical data analysis was performed using Microsoft Excel 2013 and SPSS 23.0, Origin 9 was used for data processing and mapping, and the sample plot was plotted using Arcgis 10.2.
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| CN115647028A (en) * | 2022-11-15 | 2023-01-31 | 中国长江三峡集团有限公司 | Method for restoring lead-polluted soil of acid pyrite mine |
| CN115647028B (en) * | 2022-11-15 | 2023-09-12 | 中国长江三峡集团有限公司 | Restoration method for lead-polluted soil of acidic pyrite mountain |
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