Method for quantitatively determining fluoride output load in different land types of lake basin

Abstract

The invention belongs to the technical field of soil, and particularly relates to a method for quantitatively determining fluoride output loads in different land types of a lake basin. Comprising the following steps: S1, determining a fluoride source area of a lake basin, and determining the range of different land utilization types in the area; s2, collecting fluorides in the soil in the range of different land utilization types in the S1; s3, measuring A, A0 and Ah in different land utilization types by using an isotopic tracer technology based on the fluorides in the soil collected in the S2; and S4, on the basis of a result calculated in the S3, calculating fluoride-carried output loads in different land utilization types. According to the method, soil physicochemical property analysis is combined with an isotopic tracing technology, the sources and loads of different land utilization types of the particulate fluoride in the lake basin can be quantitatively analyzed, and the key areas of the sources of the particulate fluoride can be quantitatively identified according to the load source quantities of the particulate fluoride of different land utilization types; and then the key area is controlled.

Description

Technical Field

[0001] The invention belongs to the field of soil technology, and in particular relates to a method for quantitatively determining fluoride output loads in different land types in a lake basin. Background Art

[0002] Fluorine is widely distributed in the lithosphere and hydrosphere. As the most active element in the halogen family, it is widely involved in the earth's biochemical cycle. Fluorine is one of the elements necessary for the human body, but when its content exceeds a certain threshold, it will cause varying degrees of damage to human teeth, bones, soft tissue organs, etc. At the same time, excessive intake of fluorine will also affect the normal growth and development of animals and plants.

[0003] Similar to heavy metals, fluorine has the characteristics of concealment, hysteresis, long-term and irreversibility of pollutants after entering water bodies and organisms. Excessive fluorine entering the aquatic ecosystem will seriously destroy the ecological balance of the water body and threaten the health of aquatic plants and animals.

[0004] As a receiving unit of fluorine, lakes continuously enrich fluorine in the process of biogeochemical cycle. It is reported that many factors affect the migration of F- from soil to water. The adsorption and desorption of F- in soil directly affect the ability of soil to supply F- to downstream water. Factors such as rainfall intensity, basin slope, basin vegetation coverage, basin land use and human disturbance indirectly affect the migration of fluorine from soil to water by affecting soil erosion intensity.

[0005] Fluoride in the soil migrates to downstream water bodies through soil erosion driven by rainfall runoff. However, because soil erosion occurs over a long period of time and continuously, it is still difficult to quantitatively analyze the load of fluoride entering the lake driven by soil erosion to distinguish the relationship between high lake fluoride and soil erosion. Through the use of specific monomer stable isotope technology (CSSI) and environmental radionuclide tracer technology (FRN), combined with long-term monitoring, the relationship between the entry of fluoride into the lake due to soil erosion and high lake fluoride can be distinguished to a certain extent. Existing studies have combined the FRN-CSSI tracer technology to quantitatively analyze the sources of sediment entering rivers and lakes from different land use types, but did not take into account the fluoride content carried in the sediment.

[0006] Fluorine, as an indispensable element in soil parent material, is widely present in soil and sediment. The FRN-CSSI combined tracer technology can be used to quantitatively analyze the fluoride load entering the lake. Through long-term monitoring of the lake and the main rivers entering the lake, the response relationship between surface water and lake fluoride concentrations can be determined. Chenghai is located in Yunnan Province, China, at the junction of the Yunnan-Guizhou Plateau and the Qinghai-Tibet Plateau. It is a sinkhole lake with no outflow for many years. Previous monitoring data showed that the fluoride concentration in Chenghai was high all year round. This study analyzed the reasons for the high fluoride concentration in Chenghai from two aspects: surface water and quantitative estimation of fluoride carried into the lake by sediment through long-term water quality monitoring, watershed surveys, and FRN-CSSI combined tracer technology. Summary of the invention

[0007] In view of the above-mentioned problems, the purpose of the present invention is to propose a method for quantitatively determining the fluoride output load in different land types in a lake basin. By using soil physical and chemical property analysis combined with isotope tracing technology, the sources and loads of particulate fluoride in different land use types in the lake basin can be quantitatively analyzed. According to the source amount of particulate fluoride load in different land use types, the key areas of the source of particulate fluoride can be quantitatively identified, and then the key areas can be controlled.

[0008] In order to achieve the above technical effects and the above objectives, the present invention provides a method for quantitatively determining the fluoride output load in different land types in a lake basin, comprising:

[0009] S1: Identify the fluoride source area in the lake basin and determine the extent of different land use types within the area;

[0010] S2: Collect fluoride in soil within the range of different land use types in S1;

[0011] S3: Based on the fluoride in the soil collected in S2, the A, A0 and A in different land use types were measured using isotope tracing technology. h , A h is the soil profile above depth h 137 Total Cs content, Bq / m 2 ; A is the actual measurement in the sampling year 137 Cs area activity, A0 is the sampling year 137 Cs background value, calculate soil loss and sand source contribution rate of different land use types in S1;

[0012] S4: Based on the results of S3, calculate the fluoride output load carried by different land use types.

[0013] Preferably, the calculation process of soil erosion rate of different land use types in S3 includes:

[0014] S3.1: Calculate the average annual soil erosion thickness of agricultural and non-agricultural lands;

[0015] S3.2: Calculate soil erosion rate based on the average annual soil erosion thickness in S3.1;

[0016] S3.3: Calculate the amount of soil loss based on the soil erosion rate in S3.2.

[0017] Preferably, in S3.1,

[0018] The average annual soil erosion thickness of cultivated land is calculated as:

[0019]

[0020] Where: A is the actual measurement result of the sampling year 137 Cs area activity, A0 is the sampling year 137 Cs background value, Bq / m 2 ; H is the average tillage depth, cm; h is the average annual soil erosion thickness, cm yr -1 ; N is the sampling year;

[0021] The average annual soil erosion thickness of non-agricultural land is calculated as:

[0022]

[0023] Among them, A h is the soil profile above depth h 137 Total Cs content, Bq / m 2 ; A is the actual measurement in the sampling year 137 Cs area activity, Bq / m 2 ; λ is the exponential profile distribution coefficient.

[0024] Preferably, in S3.2,

[0025] The soil erosion rate of agricultural land is calculated as:

[0026] R n =10 4 ρh

[0027] Among them, R n is the soil erosion rate of cultivated land, t ha -1 yr -1 ρ Bulk density of agricultural soil (g / cm 3 );

[0028] The soil erosion rate of non-agricultural land is calculated as:

[0029] R n '=10 4 ρ'h'

[0030] Among them, R n ' is the soil erosion rate of non-agricultural land t ha -1 yr -1 ; ρ' is the bulk density of non-agricultural soil (g / cm 3 ).

[0031] Preferably, in S3.3,

[0032] The amount of soil loss from cultivated land is:

[0033] E=R n ×t

[0034] Where: E is the amount of soil loss from cultivated land t ha -1 , R n is the soil erosion rate of cultivated land, t ha -1 yr -1 ; t is time yr -1 ;

[0035] The amount of soil loss from non-agricultural land is:

[0036] E'=R n '×t

[0037] Where: E is the amount of soil loss from cultivated land t ha -1 , R n is the soil erosion rate of cultivated land, t ha -1 yr -1 ; t is time yr -1 .

[0038] Preferably, the source of fluoride-carrying sediment in different land use types in S3 includes:

[0039] Step 1: Determine fatty acid delta 13 C content:

[0040]

[0041] Where: 13 C FA Fatty acid δ 13 C, δ 13 C FAME Methyl fatty acid δ 13 C, δ 13 C Methanol Methanol δ 13 C; X: carbon number of fatty acid;

[0042] Step 2: Based on the results of step 1, the Iso-source mixing model is used to determine the carbon isotope ratios of different land use sources in the sediment mixture:

[0043]

[0044] Where: 13 C FAT To collect the fatty acid δ 13 C content, I n is the isotopic contribution ratio of the nth source soil in the mixture estimated using the isotopic mixing model, δ 13 C FAn is the isotope value of the nth source soil;

[0045] Step 3: Substitute the calculation results of the Iso-source model into the following formula to finally obtain the sediment source contribution rate:

[0046]

[0047] Where: S n % is the contribution rate of soil to the nth source of sediment, C n % is the soil organic carbon content of the nth source, determined experimentally.

[0048] Preferably, the calculation formula for the fluoride output load carried by different land use types in S4 is:

[0049] F n =C×E×S n %×S n

[0050] Where: F n is the fluoride output load carried by sediments of different land types; C is the fluoride concentration of soil (mg / kg); E is the soil erosion amount of the nth source land use type of sediments, S n % is the contribution rate of soil to the nth source of sediment; S n is the land use area of ​​the nth source of sediment.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1. Compared with the conventional monitoring method, which requires the deployment of dense monitoring points in the watershed, this method simplifies the monitoring points in the watershed process and only needs to consider the relationship between pollution sources and sinks, which greatly reduces the workload and cost of monitoring. It helps to improve the level of agricultural non-point source pollution prevention and control, and is practicing precise tracing, providing technical support for targeted and precise governance.

[0053] 2. The present invention extends the front-end technology of tracing the source. First, the fluoride concentration of soil and sediment in the study area is analyzed. Then, through the collection of soil erosion source-sink samples and the use of isotope tracing technology, the source and load of sediment in different land use types are calculated. Then, the fluoride concentration in soil and sediment in the previous basin is brought in, and finally the source and load of fluoride carried by sediment in different land use types are calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0055] In the attached picture:

[0056] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0057] The following is combined with Figure 1 The preferred embodiments of the present invention are described. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0058] A method to quantify fluoride export loads from different land types in lake basins includes:

[0059] S1: Identify the fluoride source area in the lake basin and determine the extent of different land use types within the area.

[0060] According to the topography of Chenghai Basin, Chenghai was divided into east, south, west and north areas. In the four areas, sampling was carried out using the serpentine method according to the land use type to investigate the background value of fluoride in the soil (sediment) in the basin.

[0061] Table 1 Fluoride loading into the lake in different land use types in Chenghai Basin

[0062]

[0063]

[0064] S2: Collect fluoride from the soil in the area determined in S1 and analyze it;

[0065] Collect 0-20cm soil samples from forests, gardens, cultivated land, grasslands and bare land, 8 samples for each land use type, and 59 samples for 5 land use types. At the same time, 3 sediment samples were taken from the north, middle and south provincial controlled sections of Chenghai Lake, and 5 sediment samples and 8 sediment samples were taken from the lake. A total of 48 samples. The soil (sediment) fluoride determination method refers to "Soil Agrochemical Analysis". Fluoride determination adopts ion selective electrode method.

[0066] S3: Based on the fluoride in the soil collected in S2, the A, A0 and A in different land use types were measured using isotope tracing technology. h , where A h is the soil profile above depth h 137 Total Cs content, Bq / m 2 ; A is the actual measurement in the sampling year 137 Cs area activity, A0 is the sampling year 137 Cs background value, calculate soil loss and sand source contribution rate of different land use types in S1;

[0067] In the lake basin, undisturbed grassland under the forest was selected as the reference point, and fluoride sampling was carried out in different soil layers in the area determined by S1. The area consistent with the soil fluoride collection point in S2 was selected to collect soil nuclide samples for calculating the soil erosion rate. At the same time, samples were collected in the areas where soil fluoride was collected and in the areas where sediment was collected to calculate the soil loss amount and sand source contribution rate of different land use types. The analysis of isotope samples was carried out using the same method as the scattered environmental radionuclide tracer technology and the stable isotope analysis of specific monomer compounds.

[0068] Specific:

[0069] (1) Land use types prone to water erosion and sample collection in the Chenghai Basin

[0070] Preliminary investigations show that there are five types of land use that are prone to water erosion in the Chenghai River Basin, namely forest land, grassland, cultivated land, gardens and urban land. Since the ground of urban land is mostly hardened and soil erosion is not prone to occur, urban land was excluded from this study.

[0071] The four land use types were considered as four sources, and each source area was divided into six areas of similar size. Ten points were selected for sampling in each area using the grid method, and then the 10 points were mixed into one sample and recorded using GPS positioning. The general distance was 10-100 meters. After cleaning the organic matter on the soil surface at each point with a CSSI sampling drill, 0-2 cm mobile sediment samples were collected. After mixing the soil samples from all points, about 2 kg of soil samples were taken through a 2 mm sieve and recorded and saved before being brought back to the laboratory for processing and analysis. Six mixed samples were planned for each land use type, and a total of 24 source samples were collected.

[0072] Land sink sample collection: Find three typical slopes on the mountains facing east, south, west and north in the Chenghai Basin, collect one sample downhill from each typical slope, collect 10 points for each sample, and then mix them, finally get 3 mixed samples in each direction. Collect 12 mixed samples in total.

[0073] Analysis and testing:

[0074] (1) Soil sample processing

[0075] The collected soil samples were sieved (2 mm) and air-dried. Before fatty acid extraction, the air-dried soil samples were placed in a tin box or stainless steel box and dried in an oven at 60°C for 8-12 hours.

[0076] (2) Experimental reagents and instruments

[0077] Experimental reagents (reagent types and specifications): diatomaceous earth, dichloromethane, n-hexane, methanol (CH3OH), boron trifluoride methanol solution, hydrochloric acid (HCl), potassium hydroxide (KOH), anhydrous sodium sulfate (needs to be dried in a muffle furnace at 450℃ for 1h), saponification solution: 0.1mL KOH, 95mL CH3OH and 5mL H2O are required for 100mL solution.

[0078] (3) Experimental consumables (specifications)

[0079] Centrifuge tubes (50ml), chicken heart bottles (50ml and 100ml), stoppered test tubes, cell bottles (2ml and 4ml), droppers, glass columns, pH test papers, and cotton wool: soak in CH2Cl2 and ultrasonicate twice, for 60min and 30min respectively.

[0080] (4) Instruments and equipment

[0081] Accelerated solvent extractor (ASE 350, Thermo Fisher Scientific), rotary evaporator and air pump, vortex mixer, nitrogen blower, ultrasonic cleaner, water bath.

[0082] (5)Bulk 13 Extraction and determination of C

[0083] Weigh 5g of air-dried and sieved (0.15mm) soil sample into a 50mL centrifuge tube, add 2mL of 1mol / L hydrochloric acid and shake to remove inorganic carbon. After the mixture produces foam and hissing, add 1mL of acid and continue the reaction for 1h. If there is no bubble or hissing, it means that the carbonate has been removed. Then centrifuge at 3000 rpm for 5min and discard the liquid. Repeat this three times.

[0084] (6) Extraction and determination of fatty acids

[0085] (1) Extraction of fatty acids: ASE (accelerated solvent extraction) extraction, sample concentration, saponification reaction, impurity removal, and methyl esterification.

[0086] (2) Determination

[0087] Preparation of standard solution, fatty acid composition and content analysis (GC-MS), fatty acid methyl ester δ 13 C determination (GC-IRMS).

[0088] S3 The calculation process of soil erosion rate for different land use types includes:

[0089] S3.1: Calculate the average annual soil erosion thickness of agricultural and non-agricultural lands;

[0090] The average annual soil erosion thickness of cultivated land is calculated as:

[0091]

[0092] Where: A is the actual measurement result of the sampling year 137 Cs area activity, A0 is the sampling year 137 Cs background value, Bq / m 2 ; H is the average tillage depth, cm; h is the average annual soil erosion thickness, cm yr -1 ; N is the sampling year;

[0093] The average annual soil erosion thickness of non-agricultural land is calculated as:

[0094]

[0095] Among them, A h is the soil profile above depth h 137 Total Cs content, Bq / m 2 ; A is the actual measurement in the sampling year 137 Cs area activity, Bq / m 2 ; λ is the exponential profile distribution coefficient.

[0096] S3.2: Calculate soil erosion rate based on the average annual soil erosion thickness in S3.1; in S3.2,

[0097] The soil erosion rate of agricultural land is calculated as:

[0098] R n =10 4 ρh

[0099] Among them, R n is the soil erosion rate of cultivated land, t ha -1 yr -1 ρ Bulk density of agricultural soil (g / cm 3 );

[0100] The soil erosion rate of non-agricultural land is calculated as:

[0101] R n '=10 4 ρ'h'

[0102] Among them, R n ' is the soil erosion rate of non-agricultural land t ha -1 yr -1 ; ρ' is the bulk density of non-agricultural soil (g / cm 3 ).

[0103] S3.3: Calculate the amount of soil loss based on the soil erosion rate in S3.2.

[0104] The amount of soil loss from cultivated land is:

[0105] E=R n ×t

[0106] Where: E is the amount of soil loss from cultivated land t ha -1 , R n is the soil erosion rate of cultivated land, t ha -1 yr -1 ; t is time yr -1 ;

[0107] The amount of soil loss from non-agricultural land is:

[0108] E'=R n '×t

[0109] Where: E is the amount of soil loss from cultivated land t ha -1 , R n is the soil erosion rate of cultivated land, t ha -1 yr -1 ; t is time yr -1 .

[0110] Soil sample per unit area 137 Calculation formula of total Cs content:

[0111]

[0112] Where: CPI is the unit area of ​​the sampling point 137 Total content of Cs (Bq / m 2 ), i is the sampling layer number, n is the number of sampling layers, 1000 is the unit correction factor, Ci is the i-th sampling layer 7 Be activity (Bq / m 2 ); Bdi is the soil bulk density of the i-th sampling layer (g / m 3 );Di is the depth of the i-th sampling layer (m).

[0113] S3 The sources of fluoride-carrying sediment in different land use types include:

[0114] Step 1: Delta 13 The C results were determined by soils of different land use types. Appropriate fatty acids were selected by variance analysis to determine the carbon isotope ratios of different land use sources in sediment. Because the methyl groups of FAME produced by adding to fatty acids during the determination process have different isotope values ​​from fatty acids, 5% boron trifluoride and methanol solution (BF3 / METH) was used to correct the methyl groups added during the fatty acid derivatization process, and then the fatty acid δ 13 C content:

[0115]

[0116] Where: 13 C FA Fatty acid δ 13 C, δ 13 C FAME Methyl fatty acid δ 13 C, δ 13 C Methanol Methanol δ 13 C; X: carbon number of fatty acid;

[0117] Step 2: Based on the results of step 1, the Iso-source mixing model is used to determine the carbon isotope ratios of different land use sources in the sediment mixture:

[0118]

[0119]

[0120] Where: 13 C FAT To collect the fatty acid δ 13 C content, I n is the isotopic contribution ratio of the nth source soil in the mixture estimated using the isotopic mixing model, δ 13 C FAnis the isotope value of the nth source soil;

[0121] Step 3: Substitute the calculation results of the Iso-source model into the following formula to finally obtain the sediment source contribution rate:

[0122]

[0123] Where: S n % is the contribution rate of soil to the nth source of sediment, C n % is the organic carbon content of the nth source soil (determined by experiment).

[0124] S4: Based on the results of S3, calculate the fluoride output load carried by different land use types. The calculation formula is:

[0125] F n =C×E×S n %×S n

[0126] Where: F n is the fluoride output load carried by sediments of different land types; C is the fluoride concentration of soil (mg / kg); E is the soil erosion amount of the nth source land use type of sediments, S n % is the contribution rate of soil to the nth source of sediment; S n is the land use area of ​​the nth source of sediment.

[0127] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for quantitatively determining the fluoride output load in different land types in a lake basin, characterized by: include: S1: Identify the fluoride source area in the lake basin and determine the extent of different land use types within the area; S2: Collect fluoride in soil within the range of different land use types in S1; S3: Based on the fluoride in the soil collected in S2, the A, A0 and A in different land use types were measured using isotope tracing technology. h , where A h is the soil profile above depth h 137 Total Cs content, Bq / m 2 ; A is the actual measurement in the sampling year 137 Cs area activity, A0 is the sampling year 137 Cs background value, calculate soil loss and sand source contribution rate of different land use types in S1; S4: Based on the results of S3, calculate the fluoride output load carried by different land use types.

2. A method for quantitatively determining the fluoride output load in different land types in a lake basin according to claim 1, characterized in that: S3 The calculation process of soil erosion rate for different land use types includes: S3.1: Calculate the average annual soil erosion thickness of agricultural and non-agricultural lands; S3.2: Calculate soil erosion rate based on the average annual soil erosion thickness in S3.1; S3.3: Calculate the amount of soil loss based on the soil erosion rate in S3.

2.

3. A method for quantitatively determining the fluoride output load in different land types in a lake basin according to claim 2, characterized in that: In S3.1, The average annual soil erosion thickness of cultivated land is calculated as: Where: A is the actual measurement result of the sampling year 137 Cs area activity, A0 is the sampling year 137 Cs background value, Bq / m 2 ; H is the average tillage depth, cm; h is the average annual soil erosion thickness, cmyr -1 ; N is the sampling year; The average annual soil erosion thickness of non-agricultural land is calculated as: Among them, A h is the soil profile above depth h 137 Total Cs content, Bq / m 2 ; A is the actual measurement in the sampling year 137 Cs area activity, Bq / m 2 ; λ is the exponential profile distribution coefficient.

4. A method for quantitatively determining the fluoride output load in different land types in a lake basin according to claim 3, characterized in that: In S3.2, The soil erosion rate of agricultural land is calculated as: R n =10 4 h Among them, R n is the soil erosion rate of cultivated land, tha -1 yr -1 ρ Bulk density of agricultural soil (g / cm 3 ); The soil erosion rate of non-agricultural land is calculated as: R n '=10 4 p'h' Among them, R n ' is the soil erosion rate of non-agricultural land tha -1 yr -1 ; ρ' is the bulk density of non-agricultural soil (g / cm 3 ).

5. A method for quantitatively determining the fluoride output load in different land types in a lake basin according to claim 4, characterized in that: In S3.3, The amount of soil loss from cultivated land is: E=R n ×t Where: E is the amount of soil loss from cultivated land tha -1 , R n is the soil erosion rate of cultivated land, tha -1 yr -1 ; t is time yr -1 ; The amount of soil loss from non-agricultural land is: E’=R n ’×t Where: E is the amount of soil loss from cultivated land tha -1 , R n is the soil erosion rate of cultivated land, tha -1 yr -1 ; t is time yr -1 .

6. A method for quantitatively determining the fluoride output load in different land types in a lake basin according to claim 5, characterized in that: S3 The sources of fluoride-carrying sediment in different land use types include: Step 1: Determine fatty acid delta 13 C content: Where: 13 C FA Fatty acid δ 13 C, δ 13 C FAME Methyl fatty acid δ 13 C, δ 13 C Methanol Methanol δ 13 C; X: carbon number of fatty acid; Step 2: Based on the results of step 1, the Iso-source mixing model is used to determine the carbon isotope ratios of different land use sources in the sediment mixture: Where: 13 C FAT To collect the fatty acid δ 13 C content, I n is the isotopic contribution ratio of the nth source soil in the mixture estimated using the isotopic mixing model, δ 13 C FAn is the isotope value of the nth source soil; Step 3: Substitute the calculation results of the Iso-source model into the following formula to finally obtain the sediment source contribution rate: Where: S n % is the contribution rate of soil to the nth source of sediment, C n % is the soil organic carbon content of the nth source, determined experimentally.

7. A method for quantitatively determining the fluoride output load in different land types in a lake basin according to claim 3, characterized in that: The calculation formula for the fluoride output load carried by different land use types in S4 is: F n =C×E×S n %×S n Where: F n is the fluoride output load carried by sediments of different land types; C is the fluoride concentration of soil (mg / kg); E is the soil erosion amount of the nth source land use type of sediments, S n % is the contribution rate of soil to the nth source of sediment; S n is the land use area of ​​the nth source of sediment.

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