I

Vietnam Country Report 2002

Pham Hung Viet

National Project Coordinator of Vietnam

I. Introduction

Global chemical pollution has been a matter of great concern with the increase in public awareness towards environmental problems. Among a large number of man-made chemicals, a greater attention has been drawn on EDCs (Endocrine Disrupting Chemicals).

In general, EDCs are chemicals that are persistent, hard to be decomposed naturally, accumulative in environment and food chain and likely affective or deprivable to the normal function of human and animal’s metabolite, growth, reproduction hormone.

EDCs can be classified in many categories. However, the most well known one is Persistent Organic Pollutants (POPs), including DDT, dieldrin, chlordane, heptachlor, PCBs and dioxins... Mostly, those chemicals were produced arming to increase the effectiveness in industrial and agricultural operations. However, their reverse affects to the environment and human have been an increased concern for the managers and authorities. Over decades, many extensive surveys on POPs have conducted all over the world and people took global actions in order to reduce and eliminate the discharge of these chemicals into environment.

Known as an agriculture-based country in the South East Asia, Vietnam has millions ha of rice farms and different plants and the demand of such agrochemicals as pesticides, herbicides, etc. is estimated approximately around 45,000-50,000 tons/year. Although there are more than 50 pesticide manufactures with the total output capacity of 130,000 tons/year, still Vietnam has to import a very large amount of pesticide. Reported by the Ministry of Trade in 2002, Vietnam imported more than 34,000 tons of pesticide, mainly from China. The application of agrochemical is a motivating factor to the increase in crop yields. However, hazardous and persistent agrochemicals such as DDT and CBS, which conform less well to the guidelines issued by Plant Protection Department of Vietnam, were abused intensively for long period to improve crop yields (Tahoe et al. 1993). Statistical data show that 104 tons of DDT was utilized in Vietnam and Cambodia over the last decade (Voldner and Li, 1995). Due to the lack of scientific information, safety constructions in pesticide, the number of pesticide- infected people and the residue of those agrochemicals in the environment have been remarkable.

Following the investigation of the residues of agrochemicals-sourced POPs in rivers and estuaries, an implementation of primary evaluation in hydrosphere environment in Vietnam, West Lake (Hanoi city) and Babe Lake (Bac Kan Province) were conducted. Unlike the previous years, the occurrence of POPs was mainly focused on freshwater samples with a view to getting a basic data in different component of the environment. The survey was conducted during the period of the year 2002 in the frame of the project “Environmental Monitoring and Governance: POPs in the East Asia Hydrosphere” which is still conducting simultaneously by nine East Asia partner countries. The fresh water and sediment were collected in order to determine compounds, including hexachlorobenzene (HCB), heptachlor, aldrin, trans-chlordane, cis-chlordane, dieldrin, endrin and p, p’-DDT.

2. Sampling procedure

2.1. Selection of locations

Babe Lake is a significant natural upland lake in the North of Vietnam. The lake was formed by the combination of the tectonic force and severe in karst area. Surrounding by limestone hills of upto 500-600 m above sea level, the lake consists of three parts, Pe leng, Pe lu and Pe lam of which the total length is 9 km, the width changes between 0.2 km and 1.7km and the average depth varies from 17 to 23 m ( maximum depth reaching 38 m). Babe Lake is connected with the Nang River by Be Cam Channel, to which the water drains during the dry season. The lake thus serves as a natural reservoir for the Nang River system, while Dau Dang Waterfall plays a role of dam for the lake.

The people living in areas next to Babe Lake are generally ethnical minorities, whose key activities are for farming products such as: upland rice, wetland rice, maize, ground nuts, sugar cane, etc. Besides, they make efforts to cover forests’ surface, aimed at preventing soil from erosion and converting the land-use from desolate land to green forest, etc.

Babe Lake is considered as a representative principle location for investigating POPs because the people in this areas use DDT as a main ingredient in anti-mosquito materials.

Located in the western part of Hanoi City, West Lake is the largest lake in the Red River delta. It is horseshoe shaped and divided in to two parts: the upper part, 176 ha in area, is small and shallow; the lower part, 273 ha, is longer and deeper. The area of the lake has been progressively reducing, from 446 ha in 1960 to 413 ha in 1992, as a result of the encroachment of the residents living around. The lake had originally been a segment of the course of the Red River but is now a semi-closed water body with only small inflow and outflow channel.

West Lake is a significant hub for interesting outdoor activities such as fishing, boating, sightseeing, etc. Notably, West Lake has been the largest area for the cultivation of fruit trees, vegetables, ornamental plants and fishes in Hanoi City for a long time. In addition, located in the middle of the capital, West Lake is the center for commercial activities, especially industrial activities.

2.2. Condition during the sample collection

Water and sediment samples were collected in rainy (August 2002) and dry season (December 2002) in both Babe Lake and West Lake.

Samples of fresh water (10-20cm depth) were collected directly at the surface layer into 2 liters glass bottles. Surface sediment samples were collected by specialized equipment. All samples were immediately stored in the ice box and transported to the laboratory where they were kept in refrigerator until analysis. The sampling duration is indicated in table 2.1.

Table 2.1. Sampling time and location of the collected samples

Location	Type of sample	Sampling time	Chemicals to be analyzed
Babe lake	Freshwater and sediment	Aug. 2002 (Rainy season)	HCHs, HCB, heptachlor, aldrin, cis-chlordane, dieldrin, endrin, p,p’-DDE, p,p’-DDD, p,p’- DDT
Babe lake	Freshwater and sediment	Dec. 2002 (Dry season)	HCHs, HCB, heptachlor, aldrin, cis-chlordane, dieldrin, endrin, p,p’-DDE, p,p’-DDD, p,p’- DDT
West lake	Freshwater	Aug. 2002 (Rainy season)	HCHs, HCB, heptachlor, aldrin, cis-chlordane, dieldrin, endrin, p,p’-DDE, p,p’-DDD, p,p’- DDT
West lake	Freshwater and sediment	Dec. 2002 (Dry season)	HCHs, HCB, heptachlor, aldrin, cis-chlordane, dieldrin, endrin, p,p’-DDE, p,p’-DDD, p,p’- DDT

2.3. Sample preparation and analysis

The preparations of water and sediment samples for analysis of persistent organochlorine compounds were followed by the suggested standard procedures of UNU. The performance of the applied methods was presented in the quality control and assurance section.

2.3.1. Fresh water preparation

Fig 2.2. shows the flowchart of the analytical procedure for analyzing of organochlorine compounds in fresh water samples. 1 liter of water sample, after adding 30 g NaCl and 30 mL of 1ppm surrogate compound, was at first liquid-liquid extracted by 50 mL n-hexane. Extracted solvent was then dehydrated by passing through sodium sulfate and then concentrated to approximately 1 mL. Next, the clean up was carried out by the solid phase extraction method using silica gel cartridge ( LC- Si, 500 mg). The cartridge was extracted by 6 mL of 5% (v/v) acetone in n-hexane. Internal standard, pyrene-d10, was added by injecting 30 mL of 1 mg/mL stock solution into extracted solution. The solution was then evaporated and mess up to 1mL by n-hexane. The final aliquot was subjected to inject into the gas chromatograph-mass spectrometer (Shimadzu GC/MS-QP2010) for the quantitative and qualitative analysis.

Figure 2.2. Analytical procedure for analyzing of organochlorine compounds

in fresh water samples

2.3.2. Sediment preparation

Figure 2.3. Analytical procedure for analyzing of organochlorine compounds

in sediment samples

Briefly, 15 grams of sediment sample were Soxhlet extracted by 200 mL of 50% acetone in n-hexane (v/v). Extracted solvent was then dehydrated by passing through sodium sulfate and then concentrated to approximately 1 mL. The clean up was carried out with activated florisil packed in a glass column and eluted with mixture of n-hexane: dichloromethane . The collected solvent was then evaporated by nitrogen gas and mess up by n-hexane. The internal standard, pyrene-d10, were added by injecting 30 mL of 1 mg/mL stock solution. 2 mL of the final aliquots was injected into the gas chromatograph-mass spectrometer (Shimadzu GC/MS-QP2010) and gas chromatograph equipped with ECD detector (Shimadzu GC/ECD) for the quantitative and qualitative analysis (Fig 2.3).

Results of target compounds in this report were quantified from the GC/MS-QP2010. The GC column employed was DB-1 fused silica capillary (0.32 mm x 30 m) coated with 100% dimethylpolysiloxane at 0.25 um film thickness. The quantification was calculated from the ratio of peak area of the sample with peak area of internal standard to the corresponding ratio of peak area of the standard with peak area of internal standard. Appendix B reports the detail conditions for setting up the GC/MS.

III. Analytical results

3.1. Results of water samples

Table 3.1 and Fig 3.1 show the statistical data of analyzed compounds in water samples collected from Babe Lake and West Lake. Detail levels in each sample are tabulated in table C1 (Apendix C).

3.1.1. Babe lake

HCB, cis-chlordane, dieldrin, endrin, p,p’-DDD were not present in quantifiable amounts in any of the collected water samples. Whereas, HCHs, aldrin, p,p’-DDE, p,p’-DDT were identified in some samples with low concentration about nanogram per litter.

p,p’-DDT was only found in BW7 and BW9 samples in dry season with average concentrations 0.32 ngL^-1 and 0.28 ngL^-1, respectively. Similar to p,p’-DDT, aldrin also was identified in two samples BW9, BW10 in dry season, with average concentrations 1.07 ngL^-1 and 3.31 ngL^-1, respectively.

Isomers of HCHs were detected in some collected water samples in these campaigns, for example, a-HCH in BW2, BW7; b-HCH in BW2, BW7 and g-HCH in BW1, BW7, BW10 samples. The levels of HCHs were relative higher among others. Therefore concerns on HCHs should be increased to find out the reasons.

In this current research, heptachlor is a new target compound, but it was not found merely in any of the collected water samples, except BW1 sample in dry season.

Table 3.1. Concentrations of organochlorines ( ngL^-1) in water samples

Compounds

Babe lake (n= 20)

West lake (n= 22)

Rainy season

Dry season

Rainy season

Dry season

a- HCH

1.2

(< 0.25 -1.2)

0.52

(<0.25 - 0.52)

<0.25

(< 0.25 )

0.63

(< 0.25- 0.63)

b- HCH

<0.25

(< 0.25 )

1.58

(< 0.25 - 2.33)

<0.25

(< 0.25 )

< 0.25

(<0.25 )

g- HCH

< 0.25

(<0.25 )

1.55

(< 0.25 - 1.76)

< 0.25

(<0.25 )

< 0.25

(< 0.25 )

d- HCH

< 0.25

(< 0.25 )

< 0.25

(< 0.25 - 4.61)

< 0.25

(< 0.25 )

< 0.25

(< 0.25 )

HCHs

21.1

(<0.25– 19.9)

3.39

(<0.25 – 1.76)

< 0.25

(< 0.25)

0.63

(< 0.25 – 0.63)

HCB

<0.2

(< 0.2 )

< 0.2

(<0.2 )

< 0.2

(< 0.2 )

< 0.2

(< 0.2 )

Heptachlor

< 0.2

(< 0.2 )

1.86

(< 0.2 - 1.86 )

0.35

(<0.2-0.35 )

9.25

(<0.2 - 13.91)

Aldrin

< 0.4

(< 0.4 )

2.19

(<0.4 - 3.31)

< 0.4

(< 0.4 )

< 0.4

(< 0.4 )

Cis-chlordane

< 0.45

(< 0.45 )

< 0.45

(< 0.45 )

< 0.45

(< 0.45 )

< 0.45

(< 0.45 )

Dieldrin

< 1.5

(< 1.5 )

< 1.5

(< 1.5 )

< 1.5

(< 1.5 )

< 1.5

(< 1.5 )

Endrin

< 2

(< 2 )

< 2

(< 2 )

< 2

(< 2 )

< 2

(< 2 )

p,p’-DDE

< 0.25

(< 0.25 )

0.47

(< 0.25 - 0.64)

< 0.25

(< 0.25 )

1.43

(< 0.25 - 2.06)

p,p’-DDD

< 0.5

(< 0.5 )

< 0.5

(< 0.5 )

< 0.5

(< 0.5 )

< 0.5

(< 0.5 )

p,p’-DDT

< 0.1

(< 0.1 )

0.3

(< 0.1 - 0.32)

< 0.1

(< 0.1 )

< 0.1

(< 0.1 )

p,p’-DDTs

< 0.1

(< 0.1)

0.77

(< 0.1 - 0.32)

< 0.1

(< 0.1)

1.43

(<0.1 - 2.06)

Note: HCHs= aHCH + b-HCH + g-HCH + d-HCH

DDTs= p,p’-DDE + p,p’-DDD + p,p’-DDT

3.1.2. West lake

None of organochlorine compounds were identified in quantifiable amounts in al 11 water samples collected from West lake in rainy season. HCHs, heptachlor and p,p’-DDE were determined in four water samples in dry season, ranging from nanogram per litter to ten nanogram per litter.

Interestingly, heptachlor was found highest at West lake areas and higher compared to those at Babe Lake in dry season.

p,p’-DDT was not identified in any water samples at West lake. However the degradation product, p,p’-DDE, was present with average amount of 1,43ngL^-1.

Figure 3.1. Distribution of target POPs in freshwater samples at Babe and West lake

In general, the concentrations were relatively low, ranging between nanogram per litter. However, there were small variations between seasons. The concentrations were slightly higher in dry season compared to those in rainy season. It was also recognized that the concentrations of quantifiable compounds in West Lake is slightly higher than those in Babe Lake, particularly in dry season.

Because the West Lake is relatively closed to the river system, the exchanges of the water body are limited through the small channel. Therefore, the fluctuations of the water levels of the lake seem mainly changed by the rainwater amount between seasons. The higher water level could explain for the lower concentrations of analyzed compounds in rainy season when they were diluted.

In Babe Lake, the washout of chemicals from higher areas to the lower areas had not played important role in the variation of the concentrations of analyzed compounds when they were measured similar between seasons. The results on DDTs were not representative as expected for the area where this chemical still used as a main ingredient in anti-mosquito materials. However, it was quietly suitable for a natural upland where the use and the pollution of POPs are limited in accordance with the development of agriculture and industry.

3.2. Results of sediment samples

3.2.1. Babe lake

Similar to the water samples, HCB, cis-chlordane, dieldrin, endrin were not detected in all analyzed sediment samples in both seasons. The amount of HCHs is about 1 ng/g dry wt.

Heptachlor was recognized in 5 of 10 samples with the average concentration is 0.79 ng/g dry wt (rainy season) and 1.06 ng/g dry wt (dry season).

The presence of p, p’-DDE, p,p’- DDD, and p,p’-DDT in all samples of two seasons with the concentration ranging from nanogram to tens nanograms per gram of dry weight indicated the accumulation of those chemicals on sediment.

3.2.2. West lake

Because it is hard for us to handle the time to collect and analyze samples in rainy season, so only the result of analyzed samples in dry season was complete.

Similar to Babe Lake, HCB, cis-chlordane, dieldrin and endrin were not detected in all collected samples from West Lake. The results reveal that materials containing those compounds were not used in the study areas.

The concentrations of HCHs were from 1 to 100 ng/g dry wt, about 100 times higher than those in Babe Lake. The concentrations in sediment were not coincident with those in water when they were recognized higher in West Lake compared to Babe Lake in average. This uncorrelated relation indicated HCHs were accumulated in West Lake for time, while they have been increased used in Babe Lake.

The average concentration of aldrin in rainy season (1.04 ng/g dry wt) was not changed much compared to these in dry season (0.78 ng/g dry wt).

Except p,p’-DDT, the concentrations of p,p’-DDD and p,p’-DDE were higher in West Lake compared to those in Babe Lake. The average concentrations of p,p’-DDT; p,p’-DDD and p,p’-DDE in West Lake were 0.73 ng/g dry wt, 5.37 ng/g dry wt and 29.94 ng/g dry wt. The higher concentrations in West Lake sediment compared to Babe Lake sediment as well as the higher levels of p,p’-DDD, p,p’-DDE comparing to p,p’-DDT in West Lake indicated larger amounts of DDT have been used for time in West Lake area.

Table 3.2. Concentrations of organochlorines (ng /g dry wt) in sediment samples

Compounds

Babe lake (n= 20)

West lake (n= 22)

Rainy season

Dry season

a- HCH

0.31

(< 0.20 - 1.2)

3.46

(<0.20- 0.52)

6.1

(< 0.20 - 15.1)

b- HCH

0.5

(< 0.2- 0.5 )

< 0.2

(< 0.2 )

2.55

(< 0.2- 2.55)

g- HCH

< 0.2

(< 0.2 )

< 0.2

(< 0.2 )

< 0.2

(<0.2- 2.36 )

d- HCH

<0.20

(< 0.20 -1.13 )

< 0.20

(< 0.20 )

2.36

(< 0.20- 2.36 )

HCHs

0.59

(< 0.2- 1.13)

3.46

(<0.2- 5.26)

6.92

(<0.2- 15.1)

HCB

< 0.2

(< 0.2 )

< 0.2

(< 0.2 )

< 0.2

(< 0.2 )

Heptachlor

0.79

(< 0.15- 1.02)

1.06

(< 0.15- 1.06 )

<0.15

( 0.15)

Aldrin

< 0.25

(< 0.25 )

0.78

(< 0.25- 1.4 )

1.04

(< 0.25- 1.04 )

Cis-chlordane

< 0.5

(< 0.5 )

< 0.5

(< 0.5 )

< 0.5

(< 0.5 )

Dieldrin

< 1.5

(< 1.5 )

< 1.5

(< 1.5 )