Methods to reduce nickel accumulation and nickel bioavailability in rice

Abstract

The present invention provides a method for reducing nickel accumulation and nickel bioavailability in rice, and reduces nickel accumulation and nickel bioavailability in rice by spraying sodium ferric ethylenediaminetetraacetate on the leaves. The present invention adopts biofortification measures to increase the iron content in rice grains and simultaneously reduce nickel accumulation and nickel bioavailability in rice grains. Different from the previous complex and time-consuming means of reducing nickel accumulation in rice through soil remediation, the present invention uses a simple means of spraying sodium ferric ethylenediaminetetraacetate on the leaves to simultaneously reduce the nickel content and nickel bioavailability of rice and improve the iron nutritional quality of rice. The present invention will establish new measures for the prevention and control of health risks of nickel exposure and make new contributions to my country's food safety assurance capabilities.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy metal prevention and control, and particularly relates to a method for reducing nickel accumulation in rice and nickel bioavailability. Background Art

[0002] The most widely studied heavy metals in the environmental field are arsenic, lead, cadmium, mercury, etc. Their presence in the environment mostly comes from coal burning, industrial "three wastes" emissions, traffic exhaust, pesticides and fertilizers and other human pollution behaviors. However, soil nickel pollution mainly comes from high background values ​​of soil and weathering of background parent materials. Basalt weathered soils are widely distributed in eastern my country, and the background value of nickel is 24.6–422 mg kg -1 , which is 3.68 times the average background value of nickel in soil worldwide. Excessive nickel intake can cause skin inflammation, trachoma, chronic pharyngitis, tracheitis, and even cancer. The nickel element in the soil is easily enriched in rice grains and ingested by the population as rice is eaten, resulting in potential adverse effects. Intake of nickel through rice is considered to be the main route of nickel exposure for the population. Therefore, how to conveniently, reasonably, effectively and safely control the health risks of residents in areas with high nickel background values ​​in the soil through eating rice has become an urgent issue to be solved. The most widely used technology at present is to take measures to reduce the accumulation of nickel in rice, such as repairing contaminated soil or applying passivators, screening low nickel accumulation rice varieties, etc., but no matter which method is used, it requires huge manpower and financial resources and time costs for exploration.

[0003] Considering the bioavailability problem of rice after ingestion by the human body, that is, only the nickel with bioavailability can be absorbed by the digestive tract and enter the blood circulation, controlling the bioavailability of rice nickel is undoubtedly an effective measure to regulate human nickel exposure. Early studies have shown that nickel and iron have similar chemical properties and environmental behaviors, and the iron absorption channel in the human digestive tract is also the main pathway for nickel absorption. On the other hand, the absorption pathways of nickel and iron in plants are also considered to be common. Replenishing the iron content in plants by spraying iron on the leaves can promote competition between iron and nickel in the transport process in plants. Summary of the invention

[0004] Currently, the prevention and control of the health risks of nickel in rice are mostly carried out by reducing the activity of nickel in the soil and passivating the nickel element to indirectly reduce the absorption and accumulation of nickel in rice. There is a lack of directly reducing nickel accumulation at the rice plant level, and there is a lack of developing corresponding bioavailability regulation measures from the perspective of the bioavailability of nickel in the human gastrointestinal tract after ingestion to reduce the health risks of human nickel exposure.

[0005] The purpose of the present invention is to improve the iron content of rice by developing rice iron biofortification measures, and simultaneously reduce the nickel accumulation of rice and reduce the nickel bioavailability, so as to ultimately achieve the purpose of regulating the health hazards of rice nickel.

[0006] The present invention adopts biofortification measures to increase the iron content in rice grains and simultaneously reduce the nickel accumulation and nickel bioavailability of rice grains. Unlike the previous complex and time-consuming means of reducing nickel accumulation in rice through soil remediation, the present invention uses a simple foliar spraying of sodium ferric ethylenediaminetetraacetic acid to simultaneously reduce the nickel content and nickel bioavailability of rice and improve the iron nutritional quality of rice. The present invention will establish new measures for the prevention and control of nickel exposure health risks and make new contributions to my country's food safety assurance capabilities.

[0007] The technical solution is:

[0008] A method for reducing nickel accumulation and nickel bioavailability in rice, by spraying sodium ferric ethylenediaminetetraacetate on the leaves.

[0009] The specific steps include:

[0010] (1) Collection and preparation of nickel-contaminated soil

[0011] Contaminated soil was collected from nickel-contaminated farmland in areas with high nickel background, and after natural air drying, debris was removed, passed through a 2 mm sieve, mixed evenly, and then divided into plastic basins, with about 35 kg of dry soil per basin;

[0012] (2) Greenhouse rice cultivation and foliar spraying of sodium ferric EDTA

[0013] Select hybrid indica rice varieties commonly grown in East my country, spread rice seedling substrate on rice seedling trays, evenly sprinkle seeds and cover with a thin layer of substrate soil, and finally spray water to ensure that the entire substrate is fully moistened; spray water frequently during the seedling raising period to ensure that the rice seedlings have sufficient moisture until transplanting, and the seedling period shall not exceed 1 month;

[0014] One week before transplanting, the paddy soil in the plastic pot was fully flooded with water, with the soil surface covered by 1-2 cm of water; when transplanting, the rice seedlings were transplanted into the plastic pot with their roots, and the root system of the rice seedlings was ensured to be relatively intact during the process. About 18 seedlings were transplanted in each pot of soil; after transplanting, the growth and development of rice were managed according to the principle of "deep water for greening, shallow water for tillering, sufficient seedlings for field drying, and alternating dry and wet in the later period"; a control group and a foliar iron fertilizer treatment group were set up. After the rice entered the grain filling period, the foliar iron sodium ethylenediaminetetraacetic acid was sprayed on the foliar spraying group, and the spraying frequency was 2L of 1g L twice a week. -1 EDTA sodium iron solution, 2L solution is evenly sprayed on the leaves of three pots of rice each time;

[0015] (3) Rice harvesting and processing

[0016] After the rice enters the waxy stage, it is harvested, and the rice ears, aboveground stalks, leaves and roots are cut for the following treatment and analysis; after the rice ears are harvested, they are brought back to the laboratory and naturally dried for one week, and the grains need to calculate the yield data of ear weight and number of ears before being peeled off from the rice ears, and the peeled rice grains need to calculate the yield data of thousand-grain weight, and then hulled by a rice mill to form polished rice; part of the polished rice samples are ground into powder for element analysis; the aboveground stalks are rinsed with tap water and pure water, and then freeze-dried and ground into powder for element analysis; the roots are fully washed with tap water and pure water, and then freeze-dried and ground into powder for element analysis;

[0017] (4) Analysis of nickel and iron elements in rice grains and plant parts

[0018] (5) Determination of the bioavailability of nickel in rice

[0019] (6) Evaluation of human nickel exposure due to rice intake

[0020] Taking into account the nickel content and bioavailability in rice, and based on the amount of rice consumed weekly by adults or children, the weekly nickel exposure dose caused by rice intake in the control group and the foliar iron spraying treatment group was calculated and compared, and iron biofortification measures that can reduce the bioavailability of rice nickel and the nickel intake dose in humans were established.

[0021] Specifically, the method for analyzing nickel and iron elements in rice grains and plant parts in step (4) is:

[0022] Quantitatively weigh 0.5 g of polished rice, rice aerial part or root sample powder, add 10 mL of HNO3 aqueous solution, wherein HNO3 and water in the HNO3 aqueous solution are mixed in a volume ratio of 1:1;

[0023] Place in graphite furnace digester and digest at 105℃ for 6h;

[0024] After cooling, add 2 mL of H2O2, put into the ink furnace digester, and continue to digest at 105°C until the residual amount of the digestion solution is <1 mL;

[0025] The digestion solution was fixed to 50 mL using pure water; the contents of nickel and iron in the digestion solution were then determined using an inductively coupled plasma mass spectrometer and an inductively coupled plasma atomic emission spectrometer, respectively, and the contents of nickel and iron in polished rice and rice plant parts were finally calculated;

[0026] The control group and the foliar iron spraying treatment group were compared, and the effect of foliar iron spraying on the accumulation of nickel and iron in the grains, as well as the effect on the accumulation of nickel and iron in the aboveground parts and roots of rice were analyzed.

[0027] Since the iron fertilizers used for foliar spraying are diverse, the same purpose of iron supplementation to reduce nickel accumulation and nickel bioavailability in rice can be achieved by spraying other iron fertilizers such as ferrous sulfate, ferric citrate, amino acid chelated iron and nano-iron.

[0028] The applicant's research shows that the purpose of reducing the bioavailability of nickel in rice can also be achieved by directly adding iron salts such as sodium ferric EDTA, ferric citrate, ferrous sulfate, ferrous gluconate and other iron supplements to the rice diet.

[0029] Different from the previous technical means of reducing nickel accumulation in rice, the present invention can not only effectively reduce the nickel accumulation of rice by simply spraying iron fertilizer on the leaves, but also effectively regulate the nickel intake from the perspective of nickel bioavailability of rice. An iron biofortification measure that can simultaneously reduce nickel accumulation and nickel bioavailability in rice has been developed to achieve the purpose of reducing the health hazards of nickel exposure to the population. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flow chart of an embodiment. DETAILED DESCRIPTION

[0031] The specific technical solution of the present invention is explained in conjunction with embodiments.

[0032] like Figure 1 As shown, foliar application of sodium ferric EDTA reduced nickel accumulation and nickel bioavailability in rice.

[0033] (1) Collection and preparation of nickel-contaminated soil

[0034] Contaminated soil was collected from nickel-contaminated farmland in areas with high nickel backgrounds. After natural air drying, debris was removed and the soil was passed through a 2 mm sieve. After uniform mixing, the soil was divided into plastic basins (60 cm long, 30 cm wide, and 20 cm deep), with about 35 kg of dry soil in each basin.

[0035] (2) Greenhouse rice cultivation and foliar spraying of sodium ferric EDTA

[0036] Select hybrid indica rice varieties commonly grown in East my country, spread rice seedling substrate on the rice seedling tray, evenly sprinkle seeds and cover with a thin layer of substrate soil, and finally spray water to ensure that the entire substrate is fully moist. During the seedling period, spray water frequently to ensure that the rice seedlings have sufficient water until transplanting, and the seedling period shall not exceed 1 month.

[0037] One week before transplanting, the paddy soil in the plastic pot should be fully flooded with water, with 1-2 cm of water covering the soil surface. When transplanting, transplant the rice seedlings with their roots into the plastic pots. During the process, ensure that the root system of the rice seedlings is relatively intact. Transplant about 18 seedlings per pot of soil. After transplanting, manage the growth and development of rice according to the principle of "deep water for greening, shallow water for tillering, sufficient seedlings for sun drying, and alternating dry and wet in the later period". A control group and a foliar iron fertilizer treatment group were set up. After the rice entered the filling period, the foliar spraying group was sprayed with sodium ferric ethylenediaminetetraacetate, and the spraying frequency was 2L of 1g L twice a week. -1 Sodium ferric EDTA solution (iron content is about 150 mg L -1 ), 2L solution was evenly sprayed on the leaves of three pots of rice each time.

[0038] (3) Rice harvesting and processing

[0039] After the rice enters the waxy stage, it is harvested and the rice ears, aboveground stems, leaves and roots are cut for the following processing and analysis. After the rice ears are harvested, they are brought back to the laboratory and dried naturally for a week. Before the grains are peeled off from the rice ears, the yield data such as ear weight and number of ears need to be calculated. The peeled rice grains need to calculate the yield data such as thousand-grain weight, and then they can be hulled using a rice mill to form polished rice. Some polished rice samples are ground into powder for elemental analysis. The aboveground stems are rinsed with tap water and pure water, freeze-dried and ground into powder for elemental analysis. The roots are thoroughly washed with tap water and pure water, freeze-dried and ground into powder for elemental analysis.

[0040] (4) Analysis of nickel and iron elements in rice grains and plant parts

[0041] Quantitatively weigh polished rice, rice aerial parts or root sample powder (0.5 g), add 10 mL 1:1 (V:V) HNO3, put it into a graphite furnace digester, and digest it at 105 °C for 6 h; after cooling, add 2 mL H2O2, put it into a graphite furnace digester, and continue to digest it at 105 °C until the residual amount of the digestion solution is <1 mL; use pure water to make the digestion solution dilute to 50 mL; then use inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometer (ICP-OES) to determine the contents of nickel and iron in the digestion solution, respectively, and finally calculate the contents of nickel and iron in polished rice and rice plant parts respectively (mg kg -1 The control group and the foliar iron spraying treatment group were compared to analyze the effect of foliar iron spraying on the accumulation of nickel and iron in grains, as well as the effect on the accumulation of nickel and iron in the aboveground part and root of rice.

[0042] (5) Determination of the bioavailability of nickel in rice

[0043] In vivo experiments were conducted on mice to determine the relative bioavailability (RBA) of nickel in rice compared to pure nickel sulfate, which reflects the bioavailability of nickel in rice. The following is a brief description of the experimental process: First, the harvested rice sample was weighed, put into a household electric rice cooker and boiled with appropriate pure water. After the rice was cooked, it was poured out of the pot, squeezed into rice balls and freeze-dried; in addition, a quantitative mixture of an aqueous solution containing nickel sulfate and blank commercial rice (nickel content less than 0.04 mg kg -1 ) The rice ball feed containing nickel sulfate was also prepared by boiling. After preparation, the rice ball feed was quantitatively exposed to mice for a total of 7 days. The mice were kept in metabolic cages and could freely eat rice ball feed and pure water. After the mice were exposed for 7 days, the nickel-containing rice ball feed was replaced with blank rice feed on the 8th day, and the exposure period ended after continuing to feed for one day. The urine excreted by the mice during the entire 8-day exposure period was collected using a clean centrifuge tube, and the volume was fixed to the same volume. After high-speed centrifugation, it was filtered through a 0.45mm filter membrane. The urine sample was diluted by an appropriate multiple and the nickel content was determined by ICP-MS. The rice ball consumption of each mouse (excluding the blank rice on the eighth day) was calculated and combined with the nickel concentration in the rice to calculate the total nickel intake. The mouse nickel excretion factor, that is, the ratio of the total amount of nickel excreted in urine to the total nickel intake, was calculated. The excretion factor of the mice that ate the nickel rice sample was compared with the excretion factor of the mice that ingested nickel sulfate, and the percentage value was the relative bioavailability of nickel in the corresponding rice sample. The control group and the foliar iron spraying group were compared to analyze the effect of foliar spraying of sodium ferric EDTA on the relative bioavailability of nickel in rice.

[0044] (6) Evaluation of human nickel exposure due to rice intake

[0045] Taking into account the nickel content and bioavailability in rice, and based on the amount of rice consumed weekly by adults or children, the weekly nickel exposure dose caused by rice intake in the control group and the foliar iron spraying treatment group was calculated and compared. Iron biofortification measures that can reduce the bioavailability of rice nickel and the human nickel intake dose were established. These measures can be used to guide rice production safety in areas with high nickel backgrounds and provide guidance for protecting human health.

[0046] From 2020 to 2021, our research group used the method of the present invention to conduct two repeated greenhouse potted experiments using high-nickel background soil in Xuyi, Jiangsu Province. During the rice planting process, a control group and a treatment group sprayed with ethylenediaminetetraacetic acid sodium ferric were set up. After the rice matured, the rice samples were harvested and ground and husked into polished rice. Based on the results of the two years, the foliar spraying of iron fertilizer increased the nickel content of polished rice from 3.56 to 3.71 mg kg -1 Reduced to 1.05-1.10 mg kg -1 , the iron content ranges from about 10 mg kg -1 Up to 30 mg kg -1 Foliar spraying of iron fertilizer effectively reduced nickel accumulation in rice grains and improved the iron nutritional quality of rice. The bioavailability of nickel in rice was measured by exposing harvested control group rice and iron-sprayed group rice to mice. The results showed that foliar spraying reduced the bioavailability of nickel in rice from 70.4-77.8% to 42.4-53.7%. The increase in iron in rice effectively reduced the bioavailability of nickel in rice.

[0047] The present invention starts from two aspects: the growth and development process of rice and the absorption process of nickel rice after the human body ingests it, and provides a two-pronged advantageous measure for the prevention and control of the health hazards of nickel in rice to the human body. It provides a fully advantageous scientific basis for further exploring nutrient element biofortification measures to reduce human nickel exposure in the future, and provides new ideas and strategies for reducing the health hazards of nickel to the human body.

Claims

1. A method for reducing nickel accumulation and nickel bioavailability in rice, characterized in that: Reduction of nickel accumulation and nickel bioavailability in rice by foliar spraying of sodium ferric EDTA; The specific steps include: (1) Collection and preparation of nickel-contaminated soil Contaminated soil was collected from nickel-contaminated farmland in areas with high nickel background, and after natural air drying, debris was removed, passed through a 2 mm sieve, mixed evenly, and then divided into plastic basins, with 35 kg of dry soil per basin; (2) Planting rice in greenhouse and spraying EDTA sodium iron on leaves Select hybrid indica rice varieties commonly grown in East my country, spread rice seedling substrate on rice seedling trays, evenly sprinkle seeds and cover with a thin layer of substrate soil, and finally spray water to ensure that the entire substrate is fully moistened; spray water frequently during the seedling raising period to ensure that the rice seedlings have sufficient moisture until transplanting, and the seedling period shall not exceed 1 month; One week before transplanting, the paddy soil in the plastic pot was fully flooded with water, with the soil surface covered by 1-2 cm of water. When transplanting, the rice seedlings were transplanted into the plastic pots with their roots. During the process, the root system of the rice seedlings was ensured to be relatively intact. About 18 seedlings were transplanted in each pot. After transplanting, the growth and development of rice were managed according to the principle of "deep water for greening, shallow water for tillering, sufficient seedlings for field drying, and alternating dry and wet in the later period". A control group and a foliar iron fertilizer treatment group were set up. After the rice entered the grain filling period, the foliar iron sodium ethylenediaminetetraacetic acid was sprayed on the foliar spraying group. The spraying frequency was 2 L of 1 g L -1 EDTA sodium iron solution, 2 L solution was evenly sprayed on the leaves of three pots of rice each time; (3) Rice harvesting and processing (4) Analysis of nickel and iron elements in rice grains and plant parts (5) Determination of the bioavailability of nickel in rice (6) Evaluation of human nickel exposure due to rice intake Taking into account the nickel content and bioavailability in rice, and based on the amount of rice consumed weekly by adults or children, the weekly nickel exposure dose caused by rice intake in the control group and the foliar iron spraying treatment group was calculated and compared, and iron biofortification measures that can reduce the bioavailability of rice nickel and the nickel intake dose in humans were established.

2. The method for reducing nickel accumulation and nickel bioavailability in rice according to claim 1, characterized in that: Step (3) The rice harvesting and processing method is as follows: After the rice enters the waxy stage, it is harvested and the rice ears, aboveground stems, leaves and roots are cut for the following processing and analysis; after the rice ears are harvested, they are brought back to the laboratory and naturally dried for a week. Before the grains are peeled off from the rice ears, the ear weight and ear number yield data need to be calculated. The peeled rice grains need to calculate the thousand-grain weight yield data, and then they are husked using a rice mill to form polished rice; part of the polished rice samples are ground into powder for elemental analysis; the aboveground stems are rinsed with tap water and pure water, and then freeze-dried and ground into powder for elemental analysis; the roots are fully washed with tap water and pure water, and then freeze-dried and ground into powder for elemental analysis.

3. The method for reducing nickel accumulation and nickel bioavailability in rice according to claim 1, characterized in that: Step (4) The method for analyzing nickel and iron elements in rice grains and plant parts is as follows: Quantitatively weigh 0.5 g of polished rice, rice aerial part or root sample powder, add 10 mL of HNO3 aqueous solution, wherein HNO3 and water in the HNO3 aqueous solution are mixed in a volume ratio of 1:1; Place in graphite furnace digester and heat at 105 o C for 6 h; After cooling, add 2 mL of H2O2 and place in the ink furnace digester. Continue to o Digest under C conditions until the residual volume of the digestion solution is <1mL; The digestion solution was fixed to 50 mL with pure water. The nickel and iron contents in the digestion solution were determined by inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry, respectively. Finally, the nickel and iron contents in polished rice and rice plant parts were calculated. The control group and the foliar iron spraying treatment group were compared, and the effect of foliar iron spraying on the accumulation of nickel and iron in the grains, as well as the effect on the accumulation of nickel and iron in the aboveground parts and roots of rice were analyzed.

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