Method for evaluating bioavailability of zinc oxide nanoparticles in soil

Abstract

The invention relates to a method for evaluating bio-availability of zinc oxide nanoparticles in soil, which comprises the following steps: 1) removing animal and plant residues from a collected soil sample, crushing, air-drying and sieving for later use; 2) weighing a proper amount of diethylenetriamine pentaacetic acid and adding into ultrapure water to prepare a DTPA extracting agent or weighing a proper amount of calcium chloride powder and adding into ultrapure water to prepare a calcium chloride extracting agent; (3) weighing a certain amount of soil sample, putting the soil sample into a centrifugal tube, adding an extracting agent, and carrying out oscillation treatment; and (4) centrifuging the content in the centrifugal tube, passing through a membrane, taking supernate, and determining the content of the effective-state Zn by adopting inductively coupled plasma mass spectrometry. The method is wide in application range, small in amount of extracted soil samples, and suitable for analyzing the bio-availability of the nano zinc oxide in different soil types. And the method is simple to operate and low in cost, can comprehensively know the environmental risk and health risk of the nano-zinc oxide in the soil, and has important practical significance for evaluating the soil environmental safety and the health of people.

Description

Technical Field

[0001] The invention belongs to the technical field of soil chemistry, and in particular relates to a method for evaluating the bioavailability of zinc oxide nanoparticles in soil. Background Art

[0002] Nanomaterials are defined as particles with at least one dimension between 1 and 100 nm (ISO 2015). The rapid development of nanotechnology has led to the mass production of artificial nanoparticles, especially metal nanoparticles, and their wide application in various industries. Nanoparticles have special physical and chemical properties such as small size, large surface area, biocompatibility, stability and easy surface modification. They play a key role in different fields such as biomedical research, fuel cells, electronics, health care, cosmetics, nanosensors, etc.

[0003] However, the extensive use of metal nanoparticles will inevitably lead to their release into the environment, posing direct or indirect threats to the environment and human health. Metal nanoparticles can enter the environment through industrial emissions, household emissions, and the use of nanopesticides. Nanoparticles are particularly prone to deposition in the soil, and nanopesticides and irrigation wastewater containing nanoparticles, as well as the use of cosmetics and personal care products containing nano zinc oxide, can enter the soil. Nanoparticles can also enter the soil through air deposition. (8-28%) of the nanoparticles discharged into the environment are released into the soil. With the increasing use of metal nanoparticles, considering their potential health risks to humans and risks to the environment, more research should be conducted on the bioavailability of metal nanoparticles in the soil.

[0004] Since metal nanoparticles and the ionic metals released by their dissolution in soil can be absorbed by soil organisms, how to quickly and accurately evaluate the bioavailability of metal nanoparticles in soil is a key issue that needs to be solved. The bioavailability of metal nanoparticles refers to the part of the nanoparticles in soil or the metal ions released by their dissolution that can be used by soil organisms. The commonly used methods for evaluating the bioavailability of metal nanoparticles in soil include total amount prediction method, biological evaluation method, chemical extraction method, etc. However, the total amount prediction method ignores the unique particle characteristics of nanoparticles, and the biological evaluation method has the disadvantages of being time-consuming, cumbersome to operate, and low in accuracy. The chemical extraction method has the advantages of simple operation, high efficiency, and low cost, and has attracted the attention of more and more researchers. However, the environmental transformation of soluble metal nanoparticles such as nano-copper oxide and nano-zinc oxide is easily affected by environmental conditions such as pH. Therefore, the classic Tessier sequential extraction method and BCR continuous extraction method may overestimate the bioavailability of metal nanoparticles in soil, resulting in deviations in the results. Therefore, the present invention proposes a method for evaluating the bioavailability of metal nanoparticles in soil using a neutral chemical reagent DTPA and a CaCl2 extractant in combination with an inductively coupled plasma mass spectrometer, which is of great significance for the investigation of effective trace zinc elements in agricultural soils. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for quickly and accurately evaluating the bioavailability of nano zinc oxide in soil. The method is simple to operate, highly efficient, and low in cost, and is of great significance in evaluating the bioavailability of nano zinc oxide in soil.

[0006] The present invention is specifically implemented through the following technical solutions:

[0007] A method for evaluating the bioavailability of zinc oxide nanoparticles in soil, the method comprising the following steps:

[0008] 1) Sample pretreatment: After removing animal and plant residues from the collected soil samples, crush them, air-dry them, and sieve them for later use;

[0009] 2) Preparation of extractant: weigh an appropriate amount of diethylenetriaminepentaacetic acid and add it to ultrapure water to prepare DTPA extractant, or weigh an appropriate amount of calcium chloride powder and add it to ultrapure water to prepare calcium chloride extractant;

[0010] 3) Extraction of nano zinc oxide: Weigh a certain amount of soil sample and place it in a centrifuge tube, add the extractant and shake it;

[0011] 4) Determination of available metal ions: After the contents in the centrifuge tube are centrifuged through a membrane, the supernatant is taken out and the available Zn content is determined by inductively coupled plasma mass spectrometry.

[0012] The preparation of the DTPA extractant is specifically as follows: TEA is dissolved in ultrapure water to obtain solution A; DTPA and CaCl2·2H2O are then added to solution A, and stirred continuously to dissolve them completely to obtain solution B; concentrated hydrochloric acid is added to solution B while stirring to adjust the pH to obtain the DTPA extractant.

[0013] Furthermore, the soil sample in step 1) is at least one of brown loam, brown soil, red soil and chestnut soil.

[0014] Furthermore, in step 1), the particle size of the soil sample is less than 100 mesh.

[0015] Furthermore, in step 2), the DTPA extractant comprises 0.005 mol / L DTPA, 0.01 mol / L CaCl2 and 0.1 mol / L triethanolamine, and the pH range is 7.4-7.8, preferably 7.6.

[0016] Furthermore, in step 2), the concentration of the calcium chloride extractant is 0.01-0.05 mol / L, preferably 0.05 mol / L.

[0017] Furthermore, during the shaking treatment in step 3), the amount of the soil sample and the DTPA extractant added is: 2-6 mL of DTPA extractant is added to every 1 g of soil sample, preferably 4 mL; the amount of the soil sample and the calcium chloride extractant added is: 10-20 mL of calcium chloride extractant is added to every 1 g of soil sample, preferably 20 mL.

[0018] Furthermore, in step 3), the shaking temperature is 25±1° C., the shaking speed is 180-200 rpm, and the shaking time is 110-130 minutes.

[0019] Furthermore, in step 4), the centrifugal conditions are as follows: the centrifugal speed is 3000-4000 rpm, the centrifugal time is 8-10 minutes, and the pore size of the filter membrane used is 0.22-0.45 μm.

[0020] The detection of effective state of soil nano zinc oxide is carried out on a Perkinelmer NexION2000 inductively coupled plasma mass spectrometer, and the sampling system is preferably cleaned with 2% nitric acid to provide detection accuracy.

[0021] The present invention has the following beneficial effects:

[0022] 1) Both DTPA and CaCl2 extractants are neutral chemical reagents, which will not affect the morphology of metal nanoparticles in the soil during extraction and can accurately evaluate the bioavailability of metal nanoparticles in the soil;

[0023] 2) This extraction method has a wide range of applications, requires a small amount of soil sample for extraction, can achieve rapid detection of large quantities of soil samples, and is suitable for analyzing the bioavailability of metal nanoparticles with different physical and chemical properties in different soil types;

[0024] 3) This extraction method is simple to operate, easy to implement, and low in cost, and is of great significance in evaluating the bioavailability of metal nanoparticles in soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The Zn can be extracted by DTPA in different soils treated with nano zinc oxide;

[0026] Figure 2 Nano-zinc oxide was used to treat CaCl2 in different soils to extract Zn. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific embodiments to facilitate a better understanding of the present technical solution.

[0028] In the present invention, 30 nm ZnONPs (nano zinc oxide) (99.9%) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., DTPA (diethylenetriaminepentaacetic acid) (analytical grade) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., TEA (triethanolamine) (superior grade) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CaCl2·H2O (calcium chloride dihydrate) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., and HCl (hydrochloric acid) was purchased from Shanghai Titan Technology Co., Ltd.

[0029] The invention adds nano zinc oxide into the soil from an exogenous source to simulate the environment in which nano particles enter the soil.

[0030] Example

[0031] Soil selection: The present invention mainly collected 6 types of soil, namely brown loam, brown soil, brown desert soil, brick red soil, red soil and millet-calcium soil. Among them, the brown loam was collected from Huai'an, Jiangsu, the brown soil was collected from Linfen, Shanxi, the brown desert soil was collected from Emin, Xinjiang Uygur Autonomous Region, the brick red soil was collected from Lingao, Hainan, the red soil was collected from Dehong, Yunnan, and the millet-calcium soil was collected from Dingxi, Gansu.

[0032] Soil treatment: The collected soil was air-dried and crushed, and passed through a 20-mesh sieve. Ultrapure water was used to adjust the moisture content of the air-dried soil to about 16%, and a plastic rod was used to stir for 10 minutes to evenly distribute the water. 6.0±0.1 mg of nano zinc oxide with a particle size of 30 nm was weighed, and the nano zinc oxide was added to 600 g of soil with adjusted moisture content. Stirring was continued for 20 minutes to fully mix the nano zinc oxide and soil, and the concentration of nano zinc oxide in the soil was 10 mg / kg. The experimental soil was spread flat on a disposable plastic culture dish with a diameter of 90 mm, and about 20 g of soil was placed in each culture dish. The culture dish lid was covered and the experiment was carried out under laboratory conditions. Ultrapure water was added to the soil every day to keep the soil weight at 20 g. Samples were taken at 0, 1, 3, 5, 10, 15, 22 and 31 days respectively. .

[0033] Sampling: Four culture dishes were randomly selected at each time point, and about 2 g of soil samples were taken from each dish, and extracted with 0.05 mol / L DTPA and 0.01 mol / L CaCl2, respectively. About 2 g of soil was added to two 50 mL centrifuge tubes, and 4 mL of DTPA and 20 mL of CaCl2 were added for extraction. Oscillate at 180 rpm for 120 minutes in a constant temperature shaking incubator at 25 ° C. Then centrifuge at 3000 rpm for 10 minutes, take the supernatant and pass it through a 0.22 μm membrane, and add 1 drop of concentrated hydrochloric acid to keep the sample acidic. Zn was determined using an inductively coupled plasma mass spectrometer. 2+ concentration.

[0034] The results are as follows Figure 1-2 As shown in the figure, it can be found that the concentration of DTPA-extractable Zn in most soils is higher than that of CaCl2-extractable Zn, while in red soil, the concentration of DTPA-extractable Zn and CaCl2-extractable Zn is very close. In addition, the concentrations of DTPA-extractable Zn and CaCl2-extractable Zn in brown soil, brown soil, brick red soil and red soil all show a downward trend over time, indicating that the bioavailability of ZnONPs in these soils decreases over time. In brown desert soil and millet-calcium soil, the concentration of DTPA-extractable Zn shows a downward trend over time, while the concentration of CaCl2-extractable Zn shows an upward trend over time, indicating that the bioavailability of ZnONPs in these soils decreases over time, but the concentration of Zn that can be directly used by plants increases over time.

Claims

1. A method for evaluating the bioavailability of zinc oxide nanoparticles in soil, characterized in that: The method comprises the following steps: 1) Sample pretreatment: After removing animal and plant residues from the collected soil samples, crush them, air-dry them, and sieve them for later use; 2) Preparation of extractant: weigh an appropriate amount of diethylenetriaminepentaacetic acid and add it to ultrapure water to prepare DTPA extractant, or weigh an appropriate amount of calcium chloride powder and add it to ultrapure water to prepare calcium chloride extractant; 3) Extraction of nano zinc oxide: Weigh a certain amount of soil sample and place it in a centrifuge tube, add the extractant and shake it; 4) Determination of available metal ions: After the contents in the centrifuge tube are centrifuged through a membrane, the supernatant is taken and the available Zn content is determined by inductively coupled plasma mass spectrometry.

2. A method for evaluating the bioavailability of zinc oxide nanoparticles in soil according to claim 1, characterized in that The soil sample in step 1) is at least one of brown soil, brown soil, red soil and chestnut soil.

3. A method for evaluating the bioavailability of zinc oxide nanoparticles in soil according to claim 1, characterized in that The particle size of the soil sample in step 1) is less than 100 mesh.

4. A method for evaluating the bioavailability of zinc oxide nanoparticles in soil according to claim 1, characterized in that In step 2), the DTPA extractant contains 0.005 mol / L DTPA, 0.01 mol / L CaCl2 and 0.1 mol / L triethanolamine, and the pH range is 7.4-7.

8.

5. A method for evaluating the bioavailability of zinc oxide nanoparticles in soil according to claim 1, characterized in that The concentration of the calcium chloride extractant in step 2) is 0.01-0.05 mol / L.

6. A method for evaluating the bioavailability of zinc oxide nanoparticles in soil according to claim 1, characterized in that During the shaking treatment in step 3), the amount of the soil sample and the DTPA extractant added is: 2-6 mL of the DTPA extractant is added to every 1 g of the soil sample; the amount of the soil sample and the calcium chloride extractant added is: 10-20 mL of the calcium chloride extractant is added to every 1 g of the soil sample.

7. A method for evaluating the bioavailability of zinc oxide nanoparticles in soil according to claim 1, characterized in that In step 3), the shaking temperature is 25±1° C., the shaking speed is 180-200 rpm, and the shaking time is 110-130 minutes.

8. A method for evaluating the bioavailability of zinc oxide nanoparticles in soil as claimed in claim 1, characterized in that In step 4), the centrifugal conditions are as follows: the centrifugal speed is 3000-4000 rpm, the centrifugal time is 8-10 minutes, and the pore size of the filter membrane used is 0.22-0.45 μm.

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