Nghiên cứu cadimi trong một số nhóm đất ở việt nam và tích luỹ cadimi trong rau ăn lá tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURAL SCIENCES HA MANH THANG STUDY ON CADMIUM IN SOME VIETNAMESE SOIL GROUPS AND CADMIUM ACCUMULATION IN LEAFY VEGETABLES Major: Soil Science Code: 62 01 03 AGRICULTURAL DOCTORAL THESIS Supervisors: Assoc Prof Pham Quang Ha Assoc Prof Nguyen Dinh Manh HA NOI, 2019 The thesis published at: VIETNAM ACADEMY OF AGRICULTURAL SCIENCES Supervisors: Assoc Prof Pham Quang Ha Assoc Prof Nguyen Đinh Manh Reviewer 1: Reviewer 2: Reviewer 3: The thesis will be defended in front of the doctoral thesis examination board of Vietnam Academy of Agricultural Sciences At: Time: Date: The thesis can be found at: National Library of Vietnam Library of Vietnam Academy of Agricultural Sciences INTRODUCTION Rationale Cadmium (Cd) is one of the most toxic heavy metals for soil ecological environment, plant, human and animal health (FAO, 1992) Cd has contaminated in soil from a variety of sources such asindustrial activities, urbanization and even agricultural intensive farming, all potentially increase Cd in the environment in general and soil environment in particular Systematical studies on the current status of Cd in soil according to vietnam soil classification, the level of Cd pollution in soil environment in Vietnam are still short and there is not enough reliable scientific basis to determine the threshold level of Cd for warning and prevent soil and plan contamination in different soil groups, soil types relative with crop growth and toxicity There are very few data on the relationship between soil Cd and Cd accumulated in crops The main cause of Cd contamination in the soil, Cd over-warning levels, as well as the impact of Cd in soil to plants and ecological environment, especially for leafy vegetables are directly consumed by humans, have not been determined The results of this study will contribute to overcome this shortage such as assessing the status of Cd pollution in the soil, finding out the cause of Cd pollution, determining the relationship between Cd content in soil and vegetables to provide a reliable scientific basis for revising standards and regulations on soil Cd warning level, and propose solutions to control Cd contamination and pollution in agricultural production especially for vegetable lands Research objectives - To determine and evaluate the content of Cd in some major soil groups for agricultural production in Vietnam, the relationship of Cd in soil and Cd accumulated in crops as impacted by intensive agricultural production and industrial waste, urban, craft villages activities - To determine the effect of Cd levels in soil on growth, yield and as well as Cd accumulation in leafy vegetables (brassicaceae, water spinach) grown on alluvial soil of Red river and degraded gray soil of Vietnam Scientific and practical significance of the project 3.1 Scientific significance - The study contributes to identifying and clarifying the current status of Cd in major soil groups (gray soil, alluvial soil, red soil and sandy soil) located in different ecological regions and various pedogenesis factors It also provides a scientific basis for formualting or revising national standards and regulations on agricultural production and environmental protection concerning with Cd contamination control - Studies showed the impacts and pressures of industry and urban waste, and intensive agricultural production on to the accumulation and pollution of Cd in agricultural production land, providedinformationon the effects of Cd pollution in soil on the quality of cropproducts as well as its impact on the ecological environment and human health - Contributing a scientific back ground on the impact of Cd on the environment as well as Cd toxicity to humans and the ecological environment, formulating solutions to reduce Cd pollution in cropland in areas with high risk of Cd pollution 3.2 Practical significance The study has determined the effect of Cd content in soil on growth and development of leafy vegetables (brassicaceae, water spinach), accumulated Cd in plants grown on two main soil types (degraded gray soil, alluvial soil of the Red River) and provided the basis for the construction and improvement of national standards and regulations on soil environment, contributing to the determination of safe vegetable production areas, especially for alluvial soils and degraded gray soils of Vietnam Research subjects and scope 4.1 Research subjects - Soils: Alluvial soil, gray soil, yellow-red soil, sandy soil In which, select degraded gray soil and alluvial soil of the Red River were used to study on Cd accumulationin experimental conditions - Crops: Rice, sweet potatoes, mungbean, chilli, water spinach and some other popular vegetables In which, selection of brassicaceae and water spinach is used to study the effect of Cd poluted soil on the Cd accumulation in crop under experimental conditions 4.2 Research scope - Study and assess the current status of total Cd content in some major soil types (gray soil, alluvial soil, sandy soil, red soil) in Vietnam - Study on Cd accumulation as affected by in a number of crops (food and field crops) in some key provinces and agroecological zone as affected by agricultural activities and waste from other activites (industry, handcraft villages) - Study the effect of Cd in soil on growth and accumulate Cd in leafy vegetables (brassicaceae and water spinach) on two main soil groups (alluvial soil of Red river and degraded gray soil) New contributions - Asystematic quantitative study about Cd in some main types and groups of soil used for agricultural production in Vietnam especially on vegetable production areas - Relationship between Cd in soil and plants has been identified, the ability of Cd to accumulate in leafy vegetables, as well as the effects of Cd in soil on the growth and development of leafy vegetables grown on alluvial soil of Red River and degraded gray soil - The results added more of scientific basis for formulating Cd contaminationtreatment technologies in key vegetable growing areas, solutions to minimize Cd pollution in soil as well as solutions to minimize Cd accumulation for crops in areas with high risk of Cd contamination for agricultural production land in Vietnam today and in the future CHAPTER 1: LITERATURE REVIEW 1.1 Cadmium and some applications Cadmium, chemical sign (Cd), Cd is widely used in the industry of manufacturing reactors, welding technology, metal plating, fabricating yellow paint, manufacturing various types of batteries, and usages in jewelry and toys industry 1.2 Cd toxicity in plants Cd is not considered a nutrient element for plants, so when it enters the plant, it inhibits growth and development Cd at a concentration of 2.5 – 4.0 mg kg-1 dry soil, this concentration makes wheat yield decrease by 21%, the germination rate of corn decreases by 28% (Pham Quang Ha, 2001) Leaf blight, leaf roll and stunting are the main and conspicuous symptoms of Cd toxicity in plants Leaf yellowing can occur as Fe deficiency (Haghiri, 1973), phosphorus deficiency or reduced Mn transport (Godbold and Hutterman, 1985) The inhibition caused by Cd leads to Fe (II) deficiency and it seriously affects photosynthesis (Alcantara et al., 1994) Cd reduces the uptake, transport and use of some elements (Ca, Mg, P, K) and water in plants (Das P et al., 1997) Cd also reduces nitrate uptake and its transport from roots to shoots (Hernandez et al., 1996) Cd also affects nitrogen fixation and assimilation of ammonia in soybean nodules (Balestrasse et al., 2003) The influence of Cd on plants depends on the concentration in soil, pH, redox potential, temperature and concentration of other elements in the soil (Clarkson and Luttge, 1989; Rivetta et al., 1997) Generally, Cd firstly goes to root, the Cd content in the plant decreases in the order: roots > stems > leaves > fruits > seeds (Blum, 1997) 1.3 Cd toxicity to organisms and environment Cd compounds in water, air, solution and food are toxic In air, the maximum allowable concentration of Cd is 0.1 mg per cubic meter For animals, the death dose is 210 mg Cd kg-1 body weight Inhaling an amount of Cd vapor will make the body tired, give headache, poor appetite, weight loss, cough, loose teeth, hair loss, kidney disorders (Pham Quang Ha, 2001) According to the report of the Canadian Ministry of Environment (1997), Cd affects soil microorganisms, significantly affecting the growth of some beneficial microorganisms, when Cd content in soil is at threshold 2,9 mg kg-1 of dry soil made the total number of bacteria and fungi starting to decrease significantly According to Pham Khac Hieu (1998), pets and wild animals can suffer from Cd poisoning when eating Cd-rich food, the level of toxicity depends on species, age and weight as well as depending on other cations in food Cd infiltrates in the soil from agricultural activities, mining and industrial waste due to leakage in management 1.4 Toxicity of Cd to humans Cadmium penetrates into the body and deactivates many enzymes due to Cd2+ ions having a strong affinity for molecules containing the -SH and -SCH3 groups of the enzymes When Cd poisoning occurs, people may vomit, diarrhea or may have seizures, or even develop bone, liver, and cardiovascular diseases At a concentration of 0.25-0.5mg kg-1 body weight through the gastrointestinal tract may cause stomach ulcer and serious intestinal diseases The average lethal dose (LD50) in rats passing the gastrointestinal tract is 88-357mg CdCl2 kg-1 body weight, if in the environment containing Cd oxide, the LD50 passing through the respiratory tract is 29mg Cd per cubic centimeter in 15 minutes In addition, the rate of prostate cancer and lung cancer is also quite large in the group of people who often exposed to this poison 1.5 Source of pollution in Cd in agricultural land Source of Cd pollution from nature and atmosphere: Cd pollutes in soil through atmosphere, industrial and agricultural waste and soil itself (parent rock) Cd in soil exists in very different forms (mineral phase, organic phase, free ) Cd is absorbed by plants through vegetative and metabolic pathways When people use crop products, Cd accumulates and causes toxicity accordingly Source of Cd pollution from agricultural production: Using fertilizers and pesticides over the years also caused Cd accumulation in the soil With the types of fertilizers used in agricultural production, the inorganic phosphate fertilizers have a large source of Cd and other heavy metals Rock phosphate in Senegal and Togo contains the largest Cd content, about 160-255 g Cd tonnes-1 of P2O5 (Alloway, 1990) Phosphate fertilizer with an average Cd content of about µg g-1 will contribute about 660 tonnes of Cd to the soil in the world through the use of phosphate fertilizers in agricultural production (Williams, 1985) According to Le Van Khoa (2000), the content of Cd in phosphate is from 0.1-190 ppm, in sludge is 2-3,000 ppm, in manure from 0.1-0.8 ppm Source of Cd pollution from industrial and waste activities: In the mining and industrial areas, Cd content in soil is very high, from 2-336 mg kg-1 for mining areas and from 1.8-1500 mg kg-1 for industrial areas The peri-urban area has a Cd content of 0.02-17 mg kg-1 in irrigating water and fertilizer is 0.4-167 mg kg-1 Areas affected by urban waste have lower levels of Cd pollution than mining areas and industrial impacts (Alina Kabata, 2010) Liu and Yizhang (2013) studied Cd in soil from a coal mining area, showing that in the study area, arable land contained 0.42– 42 mg Cd kg-1 meanwhile in the area that is not affected, Cd content only reached 0.12–8.5 mg kg-1, thus agricultural activities and coal mining significantly increase the soil Cd content Research by Nguyen Bich Thu et al (1997) irrigating with textile industrial wastewater and washing powder industry, Cd accumulation in sweet brassicaceae was significantly higher than control, Cd content in the vegetables was higher than the Standards of Ministry of Health for safe vegetables, heavy metal accumulation in the area affected by industrial wastewater is alarming: Cd levels are 1.5 to times higher, thus the impact of industrial waste has been the main cause of Cd accumulation in soil and crop products 1.6 Overview of Vietnamese soils and some studies on Cadmium in soil, crops and environment in Vietnam 1.6.1 Some major agricultural soil types in Vietnam The soil types used in agriculture today are mainly alluvial soil, degraded gray soil, yellow-red soil, sandy soil, saline soil and acid sulfate soil (Le Van Khoa, Le Duc, 2014) 1.6.2 Some study results on Cadmium in soil, plants and environment in Vietnam * Cadimi in soil: According to Pham Quang Ha et al (2007), Cd in soil groups of Vietnam are much fluctuated, depending on the type of soil and ecological region The lowest average Cd is in sandy soil, the highest in saline soil Alluvial soil in some locations in Hanoi, Cd content in soil is below the threshold of Vietnamese Standard (QCVN 03-MT: 2015/BTNMT) for agricultural land (Le Duc, 1994) According to the study results of the ACIAR project, the Soils and Fertilizers Research Institute (2005), the concentration of Cd accumulated in the soil in the three districts of Gia Lam, Dong Anh and Tu Liem is very different, but still within the safe range for soil agricultural production According to Nguyen Dinh Manh (2004), Hanoi’s soil environment is polluted in areas: area is contaminated with Hg, Cd, Pb including (Thanh Tri, Linh Nam, Tran Phu and Yen My) Area is mainly contaminated with Hg including locations in the East of national road 1A Area includes northern Thanh Tri to Van Dien, Vinh Quynh, Ngoc Hoi towns, soil contaminated with Cd and Pb According to Nguyen Xuan Hai (2009), soil and mud in flooded and irrigated fields in Van Noi and Vinh Quynh (Thanh Tri) had warning signs of Cd pollution According to the study of Bui Lan Huong et al (2012), in some key vegetable growing areas of Hanoi (Dong Anh, Thanh Tri, Me Linh) and Vinh Phuc, the results show that 733/733 (100%) soil samples are found with Cd contamination The residue of Cd collected from soil samples of the three districts (Dong Anh, Soc Son and Tu Liem) is lowest and there is absolutely no sample exceeding the maximum permitted level of QCVN 03-MT: 2015/BTNMT for agricultural production land (1.5 mg kg-1) Meanwhile, the soil collected from (Gia Lam, Long Bien, Thanh Tri, Hoang Mai) has high content of Cd and exceeds the threshold of QCVN 03-MT: 2015/BTNMT for agricultural land * Cadimi in vegetables: According to Nguyen Dinh Manh et al (2004), the areas of Dong Anh and Gia Lam with some vegetable spices are lightly contaminated with Cd; Thanh Tri area is contaminated with Cd and some elements such as Pb, Hg, even some vegetable samples with Cd content exceeding times the permitted standard Research by Nguyen Thi An Hang (1998), Cd content in vegetables in regions of Van Dien and Hanel ranges from 0.0007 - 0.0125 ppm, lower than WHO’s standard According to Nguyen Dinh Manh et al (1999), study the content of Cd and Pb in vegetables along the Hanoi area shows that the content of Cd in cabbage and broccoli has a Cd content of 0.009-0019 ppm The content of Cd in some types of fruit and vegetables is 0,009-0,014 ppm; Cd content in some types of edible vegetables and tubers from 0.009-0,014 ppm and in the spice vegetables with Cd content from 0.009-0.028 ppm These results show that there are some spice vegetable samples with Cd content exceeding the safety standard (0.028 ppm) * Cadmium uptake capacity of some plants: Some plants have ability to uptake and accumulate heavy metals (Cu, Zn, Pb, Cd) from soil, water such as (reed, vetiver grass, water hyacinth, water spinach, Limnophila aromatica, mangrove palm), this showed that there are many potentials and prospects in the application of biotechnology in the treatment of contaminated soil and water (Anh B.T.K., et al., 2014) Tran Kong Tau et al (2005) investigated the possibility of Cd and Zn accumulation of popular ornamental plants (daisy, Schefflera heptaphylla, ornamental perilla, Justicia gendarussa, hibiscus, Acalypha hispida, Aglaia duperreana, Nerium oleander and Aglaonema) showed that, the plants with potential for the purpose of treating contaminated soil, especially daisies and Schefflera heptaphylla are two types of plants with high accumulation and potential for treating Cd and Zn contaminated soil According to Ho Thi Lam Tra et al (2000), the cumulative Cd cabbage gradually increased with the amount of sludge applied, with the rate application of 50% of sludge, the Cd content in cabbage increased times the permitted standard and times more than the control without sludge application The authors concluded that cabbage can be used as a Cd treatment agent 1.7 Overview of some studies on Cadmium in soil, crops and the environment in the world According to Rietra et al (2017), about 55% of total Cd in food is related to Cd in soil According to McLaughlin (1996), the Cd content in topsoil in the Netherlands and Spain is quite high of 1.70-1.76 ppm Cd in soil in countries such as Sweden, Australia, Belgium, Denmark gives the lowest results (Cd ranges from 0.20-0.33 ppm), the remaining countries have higher Cd content in soil Cd in soil depends very much on the Cd content in parent rock forming soil The average Cd in basic rock is 0.13 mg kg-1, acid rock is 0.09, sediment is 0.17 mg kg-1, in the weathered shell is 0.11 mg kg-1; the range of Cd content in parent rock is 0.01-2 mg kg-1 (Lindsay, 1979) According to McLaughlin (1996), the risk of Cd contamination from fertilizer is very high, especially in phosphate fertilizer produced from phosphate ore Cd content in phosphate ores in different countries or regions gives very different results: Cd content in western American’s phosphate ore from 60-340 ppm, Russia is 0.2 ppm, China is ppm Agricultural land without fertilizer has a Cd content of 0.05-0.97 mg kg-1 and agricultural land using fertilizers with higher Cd content reaches > 0.09 mg kg-1 Some crops have very strong absorption capacity of Cd in the soil such as verbenaceae, garden balsam, carnation, celosia, and five crystals that can absorb Cd from soil from 50-56g Cd ha-1 year-1 (Elliott and Hoang, 1996) According to Li Xiong et al (2016), beets have high Cd accumulation capacity According to De Oliveira and Vinicius Henrique (2016), increasing soil pH by liming is an effective method in reducing Cd toxicity for the development of seedlings 10 CHAPTER 2: MATERIALS, CONTENTS AND METHODS 2.1 Materials 2.1.1 Soil: The study was based on the analysis of total Cd content in 194 gray soil samples, 273 alluvial soil samples, 253 yellow-red soil samples and 200 sandy soil samples Experiments were conducted to study on Cd toxicity on alluvial soil of Red River and degraded gray soil 2.1.2 Crop: Study Cd accumulation in crops: some food and field crops (paddy, peanuts, water spinach, sweet potatoes, peppers) Experiments were conducted to study on Cd toxicity to brassicaceae and water spinach 2.2 Period and locations 2.2.1 Period: from 2013 to 2018 2.2.2 Locations: - Soil and plant sampling: In agricultural production areas in some provinces nationwide - Pot experiments: Experimental area of Agricultural Environment Institute in Phu Do, Nam Tu Liem, Hanoi 2.3 Contents of study - Evaluate Cd content in some main soil types of agricultural production in Vietnam (gray soil, alluvial soil, yellow-red soil, sandy soil) according to the original soil formation and the ecological distribution areas - Investigate the correlation of Cd content in soil and crops (food and field crops) due to agricultural production and waste impacts (industry, urban, craft villages) - Determine the influence on Cd content in soil onthe accumulation of Cd in leafy vegetables (brassicaceae and water spinach) grown on alluvial soil of Red River and degraded gray soil 2.4 Methods 2.4.1 Soil and plant sampling and treatment * Sampling - Soil sample: Topsoil soil layer (0-30 cm), sampling points away from residential areas and national road, sampling by using stainless steel sampling tools 11 - Plant sample: Taking edible part, dry weight about 15g * Sample treatment - Soil sample: ground and passed through 2mm aluminum sieve - Plant sample: Rinsed with distilled water twice, drain, air dry, dry at 40oC and ground for analysis 2.4.2 Pot experiment * Experiment 1: Study and evaluate the effect of some Cd thresholds in alluvial soil of Red River to brassicaceae and water spinach Table 2.1 Experimental treatments and studied Cd concentrations on alluvial soil Treatment Cd concentration in soil (mg kg-1) (control) + Experimental design: Randomized Complete Block Design (RCBD) with 05 treatments and 03 replications; in foam containers, size 50 x 30 cm + Fertilizers and heavy metal salts contain Cd: only use chemical fertilizers, application according to farmers' fertilizer rates; use pure CdCl2.5H2O as Cd source applied in soil * Experiment 2: Study and evaluate the effect of some Cd thresholds in degraded gray soil to brassicaceae and water spinach Table 2.3 Experimental treatments and studied Cd concentrations on degraded gray soil Treatment (control) Cd concentration in soil 0.04 (mg kg-1) + Experimental design: Randomized Complete Block Design (RCBD) with 05 treatments and 03 replications; in foam containers, size 50 x 30 cm, 20 kg soil/pot 12 + Fertilizers and heavy metal salts contain Cd: only use chemical fertilizers, application according to farmers' fertilizer rates; use pure CdCl2.5H2O as Cd source applied in soil 2.4.3 Soil and plant analysis Analysis of Cd in soil and plant: according to the Vietnamese Standard (TCVN 6496-99) 2.4.4 Data analysis - Cd data collected in soils and plants were calculated and analysed: Median (Me), minimum (Min), maximum (Max), average ( m ), standard deviation (Std), confidence interval (CI) of the average value (m), normal distribution and crop yield data using Excel processing and GenStat 2013 CHAPTER 3: RESULTS AND DISCUSSION 3.1 Evaluation of the content of Cadmium in some major agricultural land groups in Vietnam 3.1.1 Cd in alluvial soil group of Vietnam Table 3.2 Concentrations of Cd (mg kg-1) in alluvial soils Statistical parameter < Alluvial soil River system Red River Mekong River Ma River Lam River Others n 273 47 91 16 20 86 Min Max 0.01 1.7 0.133 1.600 0.010 1.620 0.045 1.250 0.035 1.100 0.200 1.700 Average 0.567 0.769 0.53 0.371 0.315 0.620 Std 0.401 0.411 0.442 0.441 0.387 0.263 0.519 0.615 0.6730.914 0.438 0.622 0.1630.606 0.1340.496 0.5640.677 m , 95% < The concentration of Cd accumulated in alluvial soils ranged from 0.519-0.615 mg kg-1; average Cd in soil in the Red River Delta had the highest value (0.769 mg kg-1); The average Cd in the alluvial soil of Ma River and Lam River was lowest among the studied soils The concentration 13 of Cd in soil tended to accumulate mainly in the topsoil layer (0-30 cm) and gradually decreased with depth of the studied soil profile (0-30; 30-80; 80120 cm) 3.1.2 Cd in gray soil (Acrisols) groups of Vietnam Table 3.8 Concentrations of Cd (mg kg-1) in Gray soils of Vietnam Statistical parameter n < Gray soils Gray Plinthic/ Degraded on old soils on Gleyic gray soils alluvial old gray on old with light alluvial soils alluvial texture 67 11 43 13 Gray Gray Degraded soils on soils on gray soils magma granite on slope acid 37 10 14 Min 0.05 0.03 0.2 0.33 0.03 0.08 0.08 Max 1.11 0.78 1.31 1.0 0.82 0.49 0.43 Average 0.426 0.420 0.456 0.638 0.270 0.292 0.274 Std 0.228 0.256 0.188 0.206 0.148 0.139 0.098 m , 95% < 0.37 0.48 0.25 - 0.9 0.40 - 0.51 0.51 - 0.76 0.22 0.32 0.19 - 0.39 Cd content in gray soil reached from 0.003-0.850 mg kg-1 At the 95% confidence level, the average Cd content in gray soils in Vietnam ranged from 0.19-0.76 mg kg-1 The largest Cd has been found in gray soil on old alluvial with light texture and the lowest has been found in gray soil on granite Cd in gray soil was very low, Cd tended to accumulate mainly in the topsoil layer of the soil profile and gradually decreased at a depth of 3080 cm and 80-120 cm 3.1.3 Cd in yellow-red soil group of Vietnam Cd content was very high, ranging from 0.01 to 3.95 mg kg-1, the average of 2.08 mg kg-1, exceeding of 1.5 mg kg-1 compared to the allowable limits of heavy metals in the soils of the Vietnamese Standard issued by Ministry of Natural Resources and Environment (QCVN 03-MT: 2015/BTNMT) Cd in 14 0.22 0.33 red soil in the South East region reached the highest level About 95% of the average value of soil Cd content ranged from 3.16 to 3.50 mg kg-1, an average of 3.33 mg kg-1 was 1.22 times higher than the limit of QCVN 03MT: 2015/BTNMT Results of analysis on 23 yellow-red soil profiles in Vietnam showed that Cd content was highest at 0-30 cm and gradually decreased in the 30-80 cm layers and the 80-120 cm layer, but Cd content at the depth of more than 120 cm tended to increase Table 3.10 Concentrations of Cd (mg kg-1) in yellow-red soils of Vietnam n Min Max Average Std Yellowred soil in Vietnam 253 0.01 3.95 2.08 1.20 Northern mountain 49 0.65 3.75 2.06 0.63 m , 95% < 1.93-2.23 1.88-2.24 Statistical parameter < Ecological region Central Central Coast Highland 49 134 1.50 0.01 3.43 3.95 2.71 1.66 0.35 1.40 2.61-2.81 1.42-1.90 Eastern South 21 2.63 3.93 3.33 0.37 3.16-3.50 Cd content was very high, ranging from 0.01 to 3.95 mg kg-1, the average of 2.08 mg kg-1, exceeding of 1.5 mg kg-1 compared to the allowable limits of heavy metals in the soils of the Vietnamese Standard issued by Ministry of Natural Resources and Environment (QCVN 03-MT: 2015/BTNMT) Cd in red soil in the South East region reached the highest level About 95% of the average value of soil Cd content ranged from 3.16 to 3.50 mg kg-1, an average of 3.33 mg kg-1 was 1.22 times higher than the limit of QCVN 03-MT: 2015/BTNMT Results of analysis on 23 yellow-red soil profiles in Vietnam showed that Cd content was highest at 0-30 cm and gradually decreased in the 30-80 cm layers and the 80-120 cm layer, but Cd content at the depth of more than 120 cm tended to increase Cd content was very high, ranging from 0.01 to 3.95 mg kg-1, an average of 2.08 mg kg-1, exceeding of 1.5 mg kg-1 compared to the limit of QCVN 03-MT: 2015/BTNMT Cd in red soil in the South East region reached the highest level There was 95% of the average value of Cd 15 content in soil ranging from 3.16-3.50 mg kg-1, an average of 3.33 mg kg-1, 1.22 times higher than the limit of QCVN 03-MT: 2015/BTNMT Results of analysis on 23 yellow-red soil profiles in Vietnam showed that Cd content was highest at 0-30 cm and gradually decreased in layers 30-80cm and 80-120 cm However, in deeper layer (> 120 cm) Cd content tended to increase 3.1.4 Cd in sandy soil group of Vietnam Bảng 3.13 Concentrations of Cd (mg kg-1) in sandy soils Ecological region North South Central Central Coast Coast 110 56 0.03 0.11 0.72 0.39 0.28 0.22 0.15 0.07 Statistical parameter Sandy soil in Vietnam North East n Min Max Average Std 209 0.03 1.29 0.28 0.16 14 0.09 0.43 0.23 0.11 0.26-0.30 0.16-0.29 < m , 95% < 0.25-0.30 0.20-0.23 South 29 0.15 1.29 0.38 0.26 0.28-0.48 Cd content in Vietnam's sandy soil was low, an average of 0.28 mg -1 kg At the confidence interval with 95% of the mean value, Cd in the sandy soil group was 0.26 - 0.30 mg kg-1 Cd was highest in sandy soil samples in the Southern region (0.38 mg kg-1) and lowest in the Northeast region (0.23 mg kg-1) Samples of sandy soil are considered to be clean for Cd content 3.1.5 Cd in soil in some areas at risk of pollution due to impacts of waste Research on Cd content in soil in some areas at risk of pollution due to the impact of waste showed that the sites at which vegetable growing was still considered clean, most of the studied soil samples have Cd content lying below the permitted threshold of the QCVN 03-MT: 2015/BTNMT for agricultural land Cd in the soil at the study sites in the outskirts of Hanoi city ranged from 0.015-2.500 mg kg-1, of which Cd content in some sites exceeded the permitted level of the QCVN 03-MT: 2015/BTNMT for agricultural land However, the accumulation of Cd in the soil was locally, 16 due to being directly affected by industrial and domestic waste sources from Hanoi city 3.2 Cd content in some major crops in Vietnam 3.2.1 Concentration of Cd accumulated in vegetables in some regions of Vietnam For leafy vegetables (basil, onion, spinach, some brassicaceae vegetables ): Residual content of Cd was from 0.02 to 0.4 mg kg-1 of dried vegetables The average cumulative Cd content was 0.15 mg kg-1 of dried vegetables for sweet potatoes leaves; Cd content in water spinach was 0.2 mg kg-1 of dried vegetables For root vegetables: Cd ranged from 0.01 to 0.62 mg kg-1 of dried vegetables Comparison of residual Cd content in studied vegetable groups showed that the average Cd accumulation in root vegetables was highest (0.21 mg kg-1 of dry matter), followed by water spinach (0.20 mg kg-1 of dry matter), Cd contents in leafy vegetables and sweet potato leaves were lowest among the studied vegetables 3.2.2 Cd in food and field crops in some regions in Vietnam The concentration of Cd residues in paddy ranged from 0.01 to 1.58 mg -1 kg of dry matter Residual Cd content in sweet potatoes ranged from 0.02 to 0.10 mg kg-1 Cd content remained in peanuts from 0.02 to 0.24 mg kg-1, Cd content in cultivated soil was from 0.02 to 0.17 mg kg-1 of dry soil Cd residues in chili ranged from 0.05 to 1.17 mg kg-1 of dry matter The content of Cd in chili and soil grown chili tended to be higher than Cd accumulated in peanuts and soil grown peanut at the studied sites 3.3 Relationship of Cd content in soil and crops under different types of impacts 3.3.1 Relationship of Cd content in soil and crops under the impact of agricultural intensification The relationship between Cd content in soil and crops, synthesized on a total of 187 pairs of soil and plant samples, results from the study showed that soil Cd content in agricultural areas has not been affected to the ability of Cd accumulation in some researched crop products (root vegetables, leafy vegetables, sweet potatoes leaves, peanuts, paddy) yet The correlation coefficients between soil Cd content and leafy vegetables, 17 between soil and seet potatoes tubers, and between soil and paddy had a very low value, which proves that Cd accumulation caused in leafy vegetables, sweet potatoes tubers and paddy was not from soil but this might be from other causes 3.3.2 Relationship of Cd content in soil and crops in some areas affected by industrial waste, urban waste and craft village waste Study on a total of 103 pairs of samples (soil - crop) including pairs of soil - paddy; 11 pairs of samples of soil – water spinach; 64 pairs of samples (soil - leafy vegetables) and 20 pairs of samples (soil - root vegetables) were collected in Hanoi, Binh Duong and Ho Chi Minh City The results of calculating the correlation coefficient between soil and plants showed that the Cd content in soil in the study areas had no correlation with the accumulation of Cd in the studied crop products This means that the current soil Cd content in areas at risk of contamination does not have a clear impact on Cd accumulation in crop products However, in the group of water spinach and paddy, the correlation coefficient (r) between Cd in soil and crop was quite large, close to the statistically significant level; therefore, in terms of potential risks of Cd contamination from soil, measures would be implemented to minimize the amount of Cd accumulated in the land in near future 3.4 Effect of Cd thresholds in soil on Cd accumulation in leafy vegetables grown on alluvial soil of Red river and degraded gray soil 3.4.1 Some chemical, physical properties and heavy metal of experimental soil The results of gray soil analysis before conducted experiment showed that the soil is rather acidic, OC in soil at poor level, moderate silt texture, soil Cd content about 0.04 mg kg-1 of dry soil The analysis of alluvial soil of the Red River before conducted experiment showed that the soil was relatively acidic; OC in the soil was at medium level, light to medium texture, the soil Cd content was 1.0 mg kg-1 of dry soil 18 3.4.2 Effect of Cd in soil on growth, yield of brassicaceae and water spinach grown on degraded gray soil and alluvial soil of Red River 3.4.2.1 Alluvial soil of Red River * Brassicaceae: The Cd content in soil was from 1-6 mg kg-1, the growth of brassicaceae was quite good, even better than the control treatment (Cd1); The average height of brassicaceae reached from 18.5 to 22.4 cm; The average yield of fresh vegetable in experimental treatments ranged from 3.97 to 9.01 tonnes ha-1; the yield of treatments with Cd application was higher than that of the control treatment * Water spinach: The Cd content in soil was from 1-6 mg Cd kg-1, without affecting the growth of water spinach; Plant height in treatments reached 43.8-58.3 cm; The average yield of fresh vegetable in all treatments was from 16.53 to 21.33 tonnes ha-1 Comparison of growth, plant height and yield showed that the Cd doses added to the soil did not affect the growth and yield of water spinach grown on alluvial soil of the Red River 3.4.2.2 Degraded gray soil * Brassicaceae: The Cd content in soil was from 0.04-6.00 mg kg-1 of soil; brassicaceae growed and developed quite well; The average height of brassicaceae reached 17.8 - 22.1 cm; The average height was highest in treatment Cd2 and lowest in treatment Cd5 The average fresh yield in experimental treatments ranged from 3.15-3.94 tonnes ha-1, the average yield of brassicaceae in treatments with high Cd application (Cd4 and Cd5) showed lower yield compared to the remaining treatments * Water spinach: The results showed that the average height of water spinach ranged from 35 to 39.3 cm; The average fresh yield in all treatments was 8.0-12.5 tonnes ha-1 Comparison of plant height and yield within treatments showed that at the levels of Cd application did not affect the height or yield of water spinach grown on the alluvial soil of the Red River 19 3.4.3 Effect of soil Cd on Cd accumulation in brassicaceae, water spinach grown on alluvial soil of Red River and degraded gray soil of Vietnam 3.4.3.1 Effect of soil Cd on Cd accumulation in brassicaceae, water spinach grown on alluvial soil of the Red River Table 3.28 Cd in soil and brassicaceae grown on alluvial of the Red River Treatment Cd in dry soil (mg kg-1) Cd in fresh vegetable (mg kg-1) Cd1 0.008 Cd2 0.037 Cd3 0.044 Cd4 0.062 Cd5 0.088 Residual Cd content in brassicaceae increased gradually from 0.008 to 0.088 mg Cd kg-1 of fresh vegetable; thus, the Cd content in soil in the experimental treatments has increased the accumulation of Cd in brassicaceae grown on alluvial soil of Red river at 99% confidence level (P = 0.01) Cd in brassicaceae in all experimental treatments were at the safe threshold as prescribed by the Ministry of Health (QCVN 8-2:2011-BYT) that is 0.2 mg Cd kg-1 of fresh vegetables Table 3.29 Cd in soil and water spinach grown on alluvial of Red River Treatment Cd in dry soil (mg kg-1) Cd in fresh vegetable (mg kg-1) Cd1 0.007 Cd2 0.045 Cd3 0.058 Cd4 0.074 Cd5 0.096 In alluvial soil, the treatment without Cd application, accumulated Cd content reached from 0.007 - 0.96 mg kg-1 of fresh vegetables; The concentration of Cd in soil in experimental treatments has increased the 20 accumulation of Cd in brassicaceae grown on the alluvial soil of Red river at 99% confidence level (P = 0.01) However, Cd in brassicaceae in all experimental treatments was still at the safe threshold as prescribed by the Ministry of Health (QCVN 8-2:2011-BYT) 3.4.3.2 Effect of soil Cd on Cd accumulation in brassicaceae, water spinach grown on degraded gray soil Table 3.30 Cd in soil and brassicaceae grown on degraded gray soil Cd in dry soil Cd in fresh vegetable Treatment (mg kg-1) (mg kg-1) Cd1 0.04 0.011 Cd2 0.101 Cd3 0.129 Cd4 0.144 Cd5 0.175 Cd in brassicaceae reached from 0.011 to 0.175 mg kg-1 of fresh vegetable; In the treatment with highest level of Cd application (Cd5), Cd content in brassicaceae reached 0.175 mg kg-1 of fresh vegetables, nearly 16 times higher than that of the control treatment Assessing the correlation between Cd content in soil and brassicaceae grown on gray soil showed that Cd in soil in experimental treatments increased Cd accumulation in brassicaceae at the confident level of 95% (P = 0, 05) Table 3.31 Cd in soil and water spinach grown on degraded gray soil Cd in dry soil (mg Cd in fresh vegetable Treatment kg-1) (mg kg-1) Cd1 0.041 0.028 Cd2 2.080 0.104 Cd3 3.371 0.154 Cd4 4.142 0.217 Cd5 6.218 0.332 With Cd levels in the studied soil, Cd accumulated in water spinach reached respectively (0,104; 0,154; 0,217 and 0,332) mg kg-1 of fresh matter Cd in vegetable of treatments Cd4 and Cd5 reached levels exceeding the permitted level of the QCVN 8-2:2011-BYT The 21 concentration of Cd in soil at the study levels had an effect on increasing Cd accumulation in water spinach grown on degraded gray soil (at P = 0.01) Results of Cd content in alluvial soil of Red river and degraded gray soil grown brassicaceae and water spinach showed that Cd accumulated in vegetables were at the correlated level of 95 to 99% The results of this study are entirely consistent with the research results of the ACIAR/LWR/1998/119 project and of Bui Lan Huong (2015) 3.4.4 Effect of soil Cd on total microorganisms on alluvial soil of Red river and degraded gray soil * Alluvial soil: The total microbial density in soil in the experimental treatments ranged from 6.55 x 106 - 8.08 x 106 CFU g-1 soil In this study, the doses of Cd application from to mg kg-1 of soil did not affect the total microorganism in the alluvial soil of the Red river However, when increasing the doses of Cd at (5 mg kg-1 and mg kg-1 of soil), total microorganisms tended to decrease * Degraded gray soil: The total microbial density in all treatments were from 1.37 x 106 - 4.08 x 106 CFU g-1 soil, reaching the highest level in treatment Cd3 and lowest level in treatment Cd5 Research results on gray soil also showed that in the treatments Cd4 and Cd5, total microorganisms in soil tended to decrease CHAPTER 4: CONCLUSIONS AND SUGGESTION 4.1 Conclusions - Cd accumulated in the topsoil layer and the profiles of the alluvial soil and gray soil in Vietnam werestill much lower than the allowable limits of QCVN03-MT: 2015/BTNMT for agricultural production land Cd in the sandy soil group had the smallest value among the studied soil groups, followed by Cd in gray soil and alluvial soil However, the study results of Cd content in yellow-red soil group were very high in all study areas, average Cd in yellow-red soil group reached from 2.06 to 3.3 mg kg-1 of soil, higher than the allowable limits of QCVN 03-MT: 2015/BTNMT - In the studied soil groups (sand, gray, alluvial), Cd content in soil tended to decrease in depth of soil profile (0-30 cm; 30-80 cm; 80-120 cm 22 and >120 cm) For yellow-red soil, the trend of accumulating Cd in the depth of soil profile was unclear - Areas affected by industrial waste of craft villages, Cd accumulation phenomenon in the soil was higher than the allowable limits of QCVN03-MT: 2015/BTNMT for agricultural land which has occurred locally - Low correlation was found between total Cd in soil and Cd accumulated in some crops (root crops, leafy vegetables, leafy sweet potato, peanuts, paddy) Thus, the cause of Cd accumulation in the studied crops is not probably from soil but this might be from other causes (such as irrigation water, fertilizers ) - At levels of Cd application from mg kg-1 to mg kg-1 of soil, there were shown no effects on growth, development, plant height and yield of brassicaceae and water spinach; on the other hand, the yield of Cd treatments were even a bit higher than that of the treatment without Cd application - On alluvial soil of the Red river with the applied Cd levels increasing from mg kg-1 to mg kg-1 of soil causing Cd accumulation in brassicaceae increased from 0.008-0.088 mg kg-1 of fresh matter; Cd in water spinach increased from 0.007-0.096 mg kg-1 of fresh matter In degraded gray soil, soil Cd content increased from 0.04-6.00 mg kg-1 of soil, this increased the amount of Cd accumulated in brassicaceae from 0.0110.175 mg kg-1 of fresh matter and Cd accumulated in water spinach from 0.028-0.332 mg kg-1 of fresh matter 4.2 Suggestion - It is necessary to revise the QCVN 03-MT: 2015/BTNMT issued by the Ministry of Natural Resources and Environment on the maximum allowable limits for heavy metals in the soil in order to update more details on agricultural production land by groups, because very high Cd content in the yellow-red soil group in many locations have been found in this study, and the average Cd in yellow-red soil exceeded the allowable limit of QCVN 03-MT: 2015/BTNMT, but there was no correlation between total Cd in soil and Cd accumulated in crop products 23 - The concentrations of Cd accumulated in the soil have been exceeded the allowable limit of QCVN 03-MT: 2015/BTNMT in some of sites in this sutdy that affected by waste (industrial, urban, craft villages) It is recommended to strengthen the warning and taking measures to manage pollution sources and waste treatment before discharging into the environment to minimize the causes of Cd accumulation in the soil - Some vegetables have been able to accumulate high Cd Although Cd in soil environment increases, it does not affect plant growth and biomass This is a potential long-term risk factor, because the amount of Cd accumulated in plants can affect the health of humans and pets Therefore, in order to have more complete data, it is necessary to have long-term studies of Cd accumulation in different crops, as well as related to soil microbial activities to accurately assess the effects of different Cd froms in soil to the quality of agricultural products and the environment./ 24 LIST OF PUBLISHING   Ha Manh Thang, Pham Quang Ha (2013), “Overview of Cadmium content in some major soil groups in Vietnam and warning of Cadmium contamination in soil in some areas affected by waste”, Journal of Agriculture and Rural Development, March, pp 91-95   Ha Manh Thang, Nguyen Thi Tham, Hoang Thi Ngan (2015), “Results of monitoring the soil environment in Vietnam in the period of 2010-2014 and proposing tasks for the period 20162020”, Proceedings of the conference to review the work of environmental protection in agriculture and rural areas in the period of 2011-2015 and the orientation for the period of 20162020 Ministry of Agriculture and Rural Development, pp 338350   Mai Van Trinh, Ha Manh Thang, Bui Thi Phuong Loan, Đo Thu Ha, Le Hong Lich (2015), “Situation of Vietnamese soil environment”, Workshop on Vietnam National Land, current utilization and challenges Vietnam Soil Science Association, November, pp 97-107   Ha Manh Thang, Pham Quang Ha (2016), “Effect of Cd content in soil on Cd accumulation ability in brassicaceae grown on alluvial soil of Red River”, Vietnam Journal of Agricultural Science and Technology, No 10 (71); pp 63-66 25 ... Ha Manh Thang, Bui Thi Phuong Loan, Đo Thu Ha, Le Hong Lich (2015), “Situation of Vietnamese soil environment”, Workshop on Vietnam National Land, current utilization and challenges Vietnam Soil... crop products 1.6 Overview of Vietnamese soils and some studies on Cadmium in soil, crops and environment in Vietnam 1.6.1 Some major agricultural soil types in Vietnam The soil types used in agriculture... results on Cadmium in soil, plants and environment in Vietnam * Cadimi in soil: According to Pham Quang Ha et al (2007), Cd in soil groups of Vietnam are much fluctuated, depending on the type of soil