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: 9 62 01 03

AGRICULTURAL DOCTORAL THESIS

Supervisors:
1. Assoc. Prof. Pham Quang Ha
2. Assoc. Prof. Nguyen Dinh Manh

HA NOI, 2019

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The thesis published at:
VIETNAM ACADEMY OF AGRICULTURAL SCIENCES
Supervisors:
1. Assoc. Prof. Pham Quang Ha

2. 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:
1. National Library of Vietnam
2. Library of Vietnam Academy of Agricultural Sciences

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INTRODUCTION
1. 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.
2. 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.
3. Scientific and practical significance of the project
3.1. Scientific significance
- The study contributes to identifying and clarifying the current

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status of Cd in 4 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.
4. 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

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(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).
5. 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

5


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

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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 7 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

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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 5 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 3 areas: area 1 is
contaminated with Hg, Cd, Pb including (Thanh Tri, Linh Nam, Tran Phu
and Yen My). Area 2 is mainly contaminated with Hg including locations in
the East of national road 1A. Area 3 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

8


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 5 times the permitted standard. Research by Nguyen Thi
An Hang (1998), Cd content in vegetables in 2 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 9 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,

9


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 9 times
the permitted standard and 2 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 5
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.

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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.

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- 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)

1
(control)
1

2

3

4

5

2

3

4

6

+ 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
1
Treatment
2
3
4
5
(control)
Cd concentration in soil
0.04
2
3
4
6
(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.

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+ 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 8
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 2 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

1

0.008

Cd2

2

0.037

Cd3

3

0.044

Cd4

4

0.062

Cd5

6

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

1

0.007

Cd2

2

0.045

Cd3

3

0.058

Cd4

4

0.074

Cd5

6
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
2
0.101
Cd3
3
0.129

Cd4
4
0.144
Cd5
6
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 1 to 4 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 6 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 2 mg kg-1 to 6 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 1 mg kg-1 to 6 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

1.   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.
2.   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.
3.   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.
4.   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