Annual report of the UNU Project in Vietnam, 2001

I. INTRODUCTION

Phthalates used in modern commerce are extremely common. One of their primary uses is as plasticizers in flexible polyvinyl chloride (PVC) products such as blood bags and children's toys, etc.. They are also used as fixatives, detergents, lubricating oils, and solvents. As a result of these diverse uses, phthalates are found in many consumer products, such as cosmetics, as well as in applications, such as wood finishes, that inevitably create opportunities for human exposure. Moreover, phthalates which occupies 67% of final product weight (O. Hutzinger, 1991), recently have been demonstrated to have weak estrogenic activity and thus can alter the estrogen level in hormone system of human being as well as animal resulting in serious health problems like cancer induction, reproductive and development impairment.   

In Vietnam, the use of phthalate has been being increasing since early 1990s together with development of plastic industry. However, there has been still no any due attention given toward its possible effects to environment contamination and human exposure. In addition, discharge of used plastic products containing phthalates is with only little management that makes presence of this compound ubiquitous in environment.     

For the above concerns and in the frame of the UNU project "Environmental Monitoring and Governance EDC Pollution in the East Coastal Hydrosphere" in Vietnam,  we have established the first dealing with the contamination of phthalates in aquatic environment under the specific condition in Vietnam. This research was conducted in three sites, including Red river (Hanoi city), its estuary (Balat, Thaibinh province), and Tamgiang-Cauhai-Langco lagoon (Thua Thien Hue province). The samplings were carried out two times during the year of 2000 and 2001 with surface water were collected for analysis of the following target compounds: DEP (Di-ethyl phthalate), DBP (Di n-butyl phthalate), DEHP (Di 2-ethyl hexyl phthalate) and DEHA (Di 2-ethyl hexyl adipate)

For continuous monitoring of alkylphenol, bisphenol-A and organochlorine compounds, surface water samples were also collected at the same three sites as presented in the 2001 report. This analysis is to assess the current pollution status and to evaluate time-trend variation of such compounds.

II. SAMPLING PROCEDURES

2.1. Selection of location

Water samples, including seawater and river water (for Red river) were collected in both rainy and dry season during year 2000 and 2001 except Red river and Balat estuary in dry season.

Because the levels of the monitored organochlorines compounds from the last study were constant between the forms of tide (see annual report year 2000), water samples taken in these events were mainly evaluated for seasonal variation.  Tab.A.1 and Tab.A.2 and Tab.A.3 (Appendix A) indicate more information related to the sampling conditions in Tamgiang-Cauhai-Langco lagoon, Red river and Balat estuary, respectively. Sampling time is given in table 2.1.

Table 2.1. Sampling time and location of the collected samples

Location	Sampling time	Chemicals analyzed
Red river	Jul. 2000 (Rainy season)	Phthalate, Bisphenol-A, alkylphenols, Organochlorines.
	Jan. 2001 (Dry season)	Phthalate, Bisphenol-A, alkylphenols, Organochlorines
Balat Estuary (sea water)	Jul. 2000 (Rainy season)	Phthalate, Bisphenol-A, alkylphenols, Organochlorines
	Jan. 2001 (Dry season)	Phthalate, Bisphenol-A, alkylphenols, Organochlorines
TamGiang lagoon	Aug. 2000 (Dry season)	Phthalate, Bisphenol-A, alkylphenols, Organochlorines
	Jan. 2001 (Rainy season)	Phthalate, Bisphenol-A, alkylphenols, Organochlorines

(Phthalate: the target compound of research 2001)

Water samples were collected in the surface layer (20 cm to 30 cm depth). They were contained in 2 liters glass bottles, immediately stored in the icebox and transported in less than 3 days to the laboratory where they would be kept in refrigerator until analysis.

Three sampling sites in this study are same as the sites selected for our previous study in 1999 (Vietnam annual report of UNU project, 1999). Our target is to continuously monitor the concentrations of the interested pollutants in those three areas so that we can evaluate their time-trend and seasonal variations. Details of sampling sites are showed in fig.2.1

2.2. Sampling sites description

The Red river is the most important river in Northern Vietnam that build up a delta spreading over an area of 2146 sq km with population around 2,736,400 people and providing largest rice production in the North. Hanoi, capital city of Vietnam and Thaibinh province are both located along Red river, Hanoi is in the middle and Thaibinh is in the downstream of this river.  Both cities are known as biggest rice producing provinces in the North. However, together with development of agriculture, many environmental problems became also concerned aspects because a large amount of pesticides and herbicides have been being used every year to protect crops from pest and weeds. In addition, many industrial centers in the Red river delta such as Hanoi, VietTri, ThaiBinh, HaiPhong are believed to daily discharge their wastewater containing toxic pollutants to aquatic environment through small rivers and creeks. These toxic substances all come to Red river, the largest inland reservoir. This problem is therefore, posing a potential danger for environment and human health of the population living along the river.

Located about 650 km in the south of Hanoi city and with population of 1,045,130 (1999), Thua Thien-Hue is an important province well known for its tourism activities and traditional, fine agricultural products. Belonging to this province, Tamgiang-Cauhai-Langco lagoon system spreads over 23,650 hectares, with 70 km of length along the northwest coast. These lagoons are recognized as one of the biggest ones in Asia and play a very important role to remain diversity of ecosystem in large coastal area.  The lagoon is also a reservoir of water from five regional rivers including Huong river, Olau river, Bo river, Truoi river, Loinong river and Cauhai river.

2.3. Sample preparation and analysis

The preparation of water samples for analysis of organochlorine compounds, bisphenol-A, alkylphenols and phthalates were performed according to the suggested standard procedures of UNU (Anonymous, 2001).

For phthalates analysis in each water samples, take 100 mL of water samples into a 100 mL volumetric flask. Add 5 mL n-hexane into this. Then further add 100 mL of 100 ppm IS1, IS2 and surrogate compound in this again. Shake the volumetric flask for 1 minute and let it staying for about 5 minute and finally pick up n-hexane layer and enter to vial of 1ml. Inject 2 mL to GC/MS.

Analysis of organochlorine compounds, bisphenol-A, alkylphenols has carried out by application of the combined procedure, which was suggested in annual report of the UNU project in Vietnam, 2001. Fig. 2.2 shows the flow chart for preparation of water samples for analyzing simultaneously alkylphenolic, bisphenol-A and organochlorine compounds.

Target compounds were quantified by a GCMS-QP500 (Shimadzu). The GC column employed was DB-1 fused silica capillary (0.32 mm x 30 m) coated with 100% dimethylpolysiloxane at 0.25 mm film thickness. The quantification was conducted by calculating the ratio of peak area of the sample with peak area of internal standard to the corresponding ratio of peak area of standard with peak area of internal standard. Appendix B reports the detail conditions for setting up GC/MS for qualitative and quantitative analysis of bisphenol-A and alkylphenols. Because the conditions for setting up GC/MS for analysis of organochlorine compounds were thoroughly described in the previous annual report, it was not repeatedly described in this report.

Figure 2.1. Combined analytical produce for simultaneous analyzing of alkylphenolic, bisphenol-A and organochlorines compounds in water

III. RESULTS AND DISCUSSIONS

3.1. Obtained results of water samples

3.1.1 Phthalates

Concentration of four compounds diethylphthalates (DEP), di- n- butylphthalates (DBP), di- 2- ethylhexyladiphates (DEHA) and di- 2- ethylhexylphthalates (DEHP) in water samples has been collected from three chosen areas are shown in Table 3.1. Detailed levels of these target compounds in each water sample are illustrated in the Table C.1, Table C.2, and Table C.3 (Appendix C).

Table 3.1. Concentrations of DEP, DBP, DEHA, DEHP (ng.L^-1) in collected water samples

No	Compounds	Red river RS (n=5)	Balat estuary RS (n=15)	Tamgiang- Cauhai- Langco lagoon
				DS (n=24)	RS (n=24)
1	DEP	< 2 (< 2)	< 2 (< 2)	4.9 (< 2- 17.6)	3.7 (< 2  - 6)
2	DBP	4.6 (< 1.2- 8.3)	3.9 (< 1.2 - 16.9)	2.3 (< 1.2- 9.2)	2.1 (< 1.2- 8)
3	DEHA	< 4 (< 4)	5.5 (< 4  - 7.2)	6.5 (< 4- 13.8)	6.3 (< 4  - 28.8)
4	DEHP	18.3 (8.8- 25.6)	17.2 (2.3- 36.2)	18.8 (< 1.1  - 78)	14.3 (2- 32)
5	S Phthalates	22.9 (0.01- 25.6)	21.1 (<  - 36.2)	26 (<  - 78)	20.1 (<   - 32)
	Figures in parentheses ( ) indicate the  range      RS: rainy season;     DS: dry season   ;      n: amounts of analyzed samples
	S Phthalates = DEP+DBP+DEHP.

As being seen in table 3.1, in rainy season, level of DEP was lower than detection limit (2 ng.L^-1) in both sites at Red river and Balat estuary. However, in Tamgiang- Cauhai- Langco lagoon, DEP concentration was found at average concentration of 3.7 ng.L^-1 in rainy season and also in this site, the concentration was 4.9 ng.L^-1 in dry season.

DBP on the other hand was determined in al three sites with only low concentrations: 4.6, 3.9, and 2.1 ng.L^-1 in Red river, Balat estuary and Tamgiang- Cauhai- Langco lagoon respectively, in the rainy season. In particular, DBP was found with 2.3 ng.L^-1  in Tamgiang- Cauhai- Langco lagoon, in the dry season.

The third compound, DEHA was lower than detection limit (4 ng.L^-1) in Red river, and around 5.5 and 6.3 ng.L^-1 in Balat estuary and Tamgiang- Cauhai- Langco lagoon in the rainy season. In dry season, DEHA was found at 6.5 ng.L^-1 in Tamgiang- Cauhai- Langco lagoon.

DEHP is probably most abundant compounds in phthalate group accounting for 70-80% of total phthalate concentration and ranging from about 14 to 19 ng.L^-1. DEHP concentration seemed to be higher in Red river than that in Balat estuary (18.3 comparison to 17.2 ng.L^-1). In Tam Giang lagoon, on the other hand, DEHP level was higher in dry season in comparison to that in the rainy season. This difference may due to the dilution of water in that lagoon during rainy season.

Figure 3.1a. Concentrations of DEP, DBP, DEHA, DEHP in rainy season (2001) 
at Red river (<), Balat estuary (=)

Figure 3.1b. Concentrations of DEP, DBP, DEHA, DEHP in rainy season (s) and dry season (=) at Tamgiang-Cauhai-Langco lagoon

In conclusion, there were maybe no significant differences of concentrations among DEP, DBP, DEHA and DEHP at all three investigated sites and those levels may suggest the background level of such compounds in aquatic environment.

However,

at Tamgiang- Cauhai- Langco lagoon, concentrations of four phthalates increased more slightly in the dry season than that in the rainy season. That may be resulted from the dilution of these compounds by water in the rainy season.

However, the above mentioned is only a few preliminary appreciations, based on the results of this research. In order to achieve an overall conclusion about the change in time or season of phthalates in general and its target compounds in particular, thorough researches should be pronounced.

3.1.2. Bisphenol- A and alkylphenols

Concentration of bisphenol- A and alkylphenols (ng.L^-1) in water samples at Red River, Balat estuary and Tamgiang- Cauthai- Langco lagoon are showed in table 3.2.

Table 3.2. Concentrations of bisphenol- A and alkylphenols (ng.L^-1) in collected water samples

No	Compounds	Red river RS (n=5)	Balat estuary RS (n=15)	TG, CH, LC, TT, SH lagoon
				DS (n=24)	RS (n=24)
1	4-t-Butylphenol	6.3 (4.9- 7.9)	8.9 (<0.13- 22.8)	5.1 (0.8- 10.1)	4.8 (<0.13- 4.8)
2	2,4-Dichlorophenol	1.9 (<0.15- 2)	<0.15 (<0.15)	1.1 (<0.15- 2)	<0.15 (<0.15)
3	4-n-Butylphenol	7.4 (4.9- 11.1)	4.9 (0.3- 8.1)	4.8 (<0.1- 9.6)	1.5 (<0.1- 7.4)
4	4-n-Pentylphenol	1.6 (1.1- 2.0)	1.1 (<0.1- 6.3)	0.8 (<0.1- 3.1)	0.4 (<0.1- 0.5)
5	4-n-Hexylphenol	0.4 (0.3- 0.6)	15.7 (<0.1- 25.7)	18 (5.8- 47.5)	1.4 (<0.1- 3.2)
6	4-t-Octylphenol	<0.15 (<0.15)	1.1 (<0.15- 2.4)	2.9 (<0.15- 17.9)	1.9 (<0.15- 13.4)
7	4-n-Heptylphenol	1.6 (0.4- 4.4)	<0.23 (<0.23)	8.2 (<0.23- 15.8)	3.3 (<0.23- 4.5)
8	4-Nonylphenol	25.9 (2.8- 70.3)	9.7 (<1- 22.5)	63.1 (<1- 131.2)	<1 (<1)
9	4-n-Octylphenol	3.1 (<0.1- 8.8)	0.3 (<0.1- 0.5)	3.1 (<0.1- 14.1)	2.7 (<0.1- 12.9)
10	Pentachlorophenol	0.9 (<0.2- 1.1)	<0.2 (<0.2)	6 (<0.2- 7.4)	3.6 (<0.2- 8.8)
11	Bisphenol-A	9.8 (6.9- 15.6)	3.2 (0.8- 6.2)	13.9 (6.7- 44.9)	16.8 (<0.5- 45.8)
12	S alkylphenols	46.3	41.7	106	16

Figures in parentheses( ) indicate the  ranges

RS: rainy season;     DS: dry season;

n: amounts of analyzed samples

S alkylphenols= 4-t-Butylphenol+ 4-n-Butylphenol+4-n-Pentylphenol+4-n-Hexylphenol+ 4-t-    Octylphenol+ 4-n-Heptylphenol+ 4-Nonylphenol+ 4-n-Octylphenol.

In general, the levels of total alkylphenols and bisphenol-A varied from 16 to about 106 ngL^-1 in rainy and dry season in Tam Giang lagoon. In Red river and its estuary, the concentration was higher than that in Tam Giang lagoon in the same rainy season.

By comparing the results of 2001 with that of 2000, we see that:

At the Red River, in the rainy season, the level of total alkylphenols was sustainable, but bisphenol-A was three times lower than that in 2000 (30 ng.L^-1 in 2000 and 9.8 ng.L^-1 in 2001).

At Balat estuary, in the rainy season, the level of total alkylphenols was three times higher than that in 2000 (41.7 compared to 12 ng.L^-1 in 2000). Meanwhile, the level of bisphenol-A in this study (3.2 ng.L^-1) has increased lightly than in 2000 (5.4 ng.L^-1).

In similar comparison, at lagoons of Hue province, concentration of total alkylphenols and bisphenol-A has increased. In the rainy season, total alkylphenols were 6.8 ng.L^-1, 16 ngL^-1 and bisphenol-A were 0.9 ng.L^-1, 4.7 ng.L^-1 in 2000, 2001 respectively. In the dry season, the level of total alkylphenols and bisphenol-A was higher than that in the rainy season (total alkylphenols were 31 ng.L^-1, 106 ng.L^-1 and bisphenol-A were 3.4 ng.L^-1, 13.9 ng.L^-1 in 2000, 2001 respectively. Nevertheless, total alkylphenols from our study was still below the safely level.

Figure 3.2.  Histogram illustrate total of alkylphenols, bis phenol-A at Red River (n),         Balat estuary (n), Tamgiang-Cauhai-Langco lagoon (V)

3.1.3 Organochlorines

Concentration of the main organochlorines compounds in collected water are indicated in Table 3.3 and more detailed in Table C1, Table C2 (appendix C)

      Table 3.3. Concentrations of orgarochlorines (ng.L^-1 ) in collected water samples.

No	Compounds	Red river RS(n=5)	Balat estuary RS(n=15)	TG, CH, LC, TT, SH lagoon
				DS(n=24)	RS(n=24)
1	p,p'-DDE	<2 (<2)	<2 (<2)	<2 (<2)	<2 (<2)
2	p,p'-DDD	<2 (<2)	<2 (<2)	<2 (<2)	<2 (<2)
3	p,p'-DDT	<2 (<2)	3 (<2 - 9.94)	5.8 (<2 - 10.53)	<2 (<2)
4	S p,p'-DDTs	<2	3	5.8	<2

Figures in parentheses( ) indicate the  range

RS: rainy season ;     DS: dry season   ;

S p,p'-DDTs= p,p’-DDE+ p,p’-DDD+ p,p’-DDT

Similar to the results of previous campaigns, aldrin, dieldrin, andrin and HCHs were not present in any of the collected water samples that once again confirm the possibility of not using these compounds around the studied areas.

The whole of three compounds of p,p’-DDE, p, p’-DDD, were identified in all water collected samples in Red River, Balat estuary and in Tamgiang- Cauhai- Langco lagoon. However, p, p’-DDT presented with a quite low levels in Balat estuary (rainy season) and Tamgiang- Cauhai- Langco lagoon (dry season) with concentrations 3 ng.L^-1 and 5.8 ng.L^-1 respectively.

In comparison with the results of the year of 2000 (2.97 ng.L^-1), S p, p’-DDTs in Balat estuary did not fluctuate much in the rainy season.

Although there was not enough time for collecting and analyzing water samples in the dry season, concentration of these compounds were predicted still vary slightly thanks to the previous data. In short, in Balat estuary and Red River, the levels of S p, p’-DDTs still follow the trend, that decreases according to time and seasons.

Figure 3.3.a Temporal changes of å p,p’-DDTs at Balat estuary

Figure 3.3.b Temporal changes of å p,p’-DDTs at Red river (<) and Tamgiang-Cauhai-Langco lagoon (=)

At Tamgiang- Cauhai- Langco lagoon, in the dry season, concentration of S p, p’-DDTs were 5.8 ng.L^-1, which was higher than that in 2000 (not detectable), but much lower than that in 1999. At low concentration the changes of S p, p’- DDTs in 2001 was not really considerable and when comparing it with the previous results, However, further researches should be worked out to explain clearly the reasons for the fluctuation of the level of S p, p’-DDTs at Tamgiang- Cauhai- Langco lagoon.

3.2. Quality control and quality assurance

The quality of data was checked for every batch of 20 samples by using blank samples and spiked samples at the concentrations of 30 ng.L^-1 for alkylphenols and bisphenol-A and of 15 ng.L^-1 for organochlorine compounds. However, that was executed for every batch of 5 samples in case of phthalates at the concentrations of 40 ng.L^-1.

The performance of the analytical procedure for phthalates compounds suggested by UNU (Anonymous, 2001) was evaluated by applying blank samples, spiked samples, replicate samples. Fig.4.3b is an example of a chromatogram of blank sample. DEP, DBP, DEHP compounds were identified in the blank samples. The reason for presence of the target compounds in blank could be due to their ubiquity, e.g. in organic solvents, some parts of instrument, even air in the room. However, after blank subtraction, high recoveries, low values of deviation and CV have shown the good performance of the analytical procedure (Tab 3.4). Replicate injections (reappearance test) were also carried out. The precision of results (Tab.3.5) indicated the stabilization of the analytical instrument and the sustainable volume of the sample injected.

Our used analytical procedure were performed basing on combination of two analytical procedures provided by UNU and with necessary modifications. High recoveries of alkylphenolic, bisphenol-A and of organochlorine compounds, clearly have demonstrated the good performance of this analytical procedure (Tab. 3.6), (Tab. 3.7), (Tab. 3.8), (Tab. 3.9). The settings for GC/MS running in this case however, were remained same as those for individual program for alkylphenols and organochlorine compounds.

Figure 3.4a.  Chromatogram of solvents for phthalates

Figure 3.4b. Chromatogram of blank sample for phthalates

Table 3.4. Recoveries of phthalates from spiked samples (40 ng.L^-1)

No.	Compounds	1	2	3	4	5	Average	Deviation	CV%
1	DBP-d4	I.S.	I.S.	I.S.	I.S.	I.S.
2	DEP	39.615	37.435	38.445	28.248	33.303	37.658	1.407	3.74
3	DBP	42.742	42.896	42.937	43.923	41.415	42.783	0.801	1.87
4	DPeP-d4	19.996	21.106	19.980	19.384	18.423	19.778	0.980	4.96
5	DOP-d4	I.S.	I.S.	I.S.	I.S.	I.S.
6	DEHA	37.640	38.102	39.768	38.195	39.345	38.610	0.806	2.09
7	DEHP	43.248	44.303	42.448	40.018	39.548	41.913	1.842	4.39

Table 3.5. Reappearance of phthalates compounds (40 ng.L^-1)

No.	Compounds	1	2	3	4	5	Average	Deviation	CV%
1	DBP-d4	42786	41389	46868	45629	45641	44462.6	2039.268	4.586
2	DEP	37397	38704	39986	37645	40166	38779.6	1282.782	3.308
3	DBP	90555	92609	94988	90909	93342	92480.6	1818.201	1.966
4	DPeP-d4	62833	60033	60568	64754	66633	62964.2	2784.529	4.422
5	DOP-d4	37626	36192	36166	35483	37315	36556.4	888.3841	2.430
6	DEHA	8780	8465	8581	8550	8607	8596.6	115.6257	1.345
7	DEHP	145508	144317	146218	143282	144582	144781	1128.649	0.780

Table 3.6. Recoveries of alkylphenols and bisphenol-A from spiked samples (30 ng.L^-1)

No.	Compounds	1	2	3	4	5	Average	Deviation	CV %
IS1	Naphthalene-d8	I.S.	I.S.	I.S.	I.S.	I.S.
1	4-t-Butylphenol	28.71	31.38	30.73	30.98	30.71	30.95	0.31	1.01
2	2,4-Dichlorophenol	29.01	25.59	31.19	31.94	30.73	30.71	1.24	4.04
3	4-n-Butylphenol	31.04	26.34	31.02	25.71	31.65	31.24	0.36	1.14
4	4-n-Pentylphenol	31.69	27.95	30.38	26.58	30.08	30.72	0.86	2.79
5	4-n-Hexylphenol	29.29	29.35	30.34	31.31	33.20	30.07	0.96	3.18
6	4-t-Octylphenol	34.30	30.59	30.90	31.51	31.40	31.10	0.43	1.38
7	4-n-Heptyphenol	30.48	33.05	29.99	30.18	32.19	30.71	1.01	3.28
8	4-nonylphenol	33.17	32.98	28.42	33.02	30.78	32.49	1.14	3.52
IS2	Phenathrene-d10	I.S.	I.S.	I.S.	I.S.	I.S.
9	4-n-Octylphenol	31.31	29.62	31.52	31.72	31.56	31.15	0.87	2.78
10	Pentachlorophenol	28.76	29.08	32.33	30.99	30.29	30.12	0.97	3.21
IS3	Pyrene-d10	I.S.	I.S.	I.S.	I.S.	I.S.
Surr	Bisphenol-A d16	83.01	84.81	91.67	83.65	93.23	83.82	0.91	1.09
11	Bisphenol-A	29.18	34.46	31.21	28.52	29.04	29.49	1.18	4.01

Table 3.7. Reappearance of alkylphenolic compounds and bisphenol-A (30 ng.L^-1)

No.	Compounds	1	2	3	4	5	Average	Deviation	CV(%)
IS1	Naphthalene-d8	117944	110835	113785	116437	120846	114750	3125	2.72
1	4-t-Butylphenol	23448	20558	23079	22796	22713	23009	332	1.44
2	2,4-Dichlorophenol	6268	6276	6347	6415	6638	6327	69	1.09
3	4-n-Butylphenol	31703	29992	30903	31397	33743	30999	748	2.41
4	4-n-Pentylphenol	36862	31612	32976	33634	35616	32741	1031	3.15
5	4-n-Hexylphenol	37787	34722	35297	37329	38173	37147	1280	3.45
6	4-t-Octylphenol	32284	28085	29964	32064	32525	31709	1179	3.72
7	4-n-Heptyphenol	38459	35369	36791	37837	40920	37114	1352	3.64
IS2	4-nonylphenol	54896	54862	54217	56591	57299	55142	1016	1.84
8	Phenathrene-d10	3283	3053	3130	3252	3380	3180	107	3.37
9	4-n-Octylphenol	37106	33206	36238	35885	38268	36874	1061	2.88
10	Pentachlorophenol	2515	2266	2429	2447	2428	2455	41	1.67
IS3	Pyrene-d10	79447	72709	75732	79510	87368	78230	2163	2.77
Surr	Bisphenol-A d16	53823	51801	53423	55102	54261	53682	720	1.34
11	Bisphenol-A	15947	13996	14634	15088	15609	15320	578	3.77

  Table. 3.8. Recoveries of organochlorine compounds from spiked samples (15 ng.L^-1)

No.	Compounds	1	2	3	4	5	Average	Deviation	CV%
IS1	Phenanthrene-d10	IS	IS	IS	IS	IS
1	a-HCH	14.86	14.85	14.78	14.05	14.25	14.55	0.38	2.61
2	b-HCH	14.04	14.95	14.75	14.87	14.87	14.69	0.37	2.52
3	y-HCH	14.87	14.12	14.48	14.79	14.07	14.46	0.37	2.56
4	d-HCH	15.24	15.04	15.09	15.81	15.01	15.23	0.33	2.17
IS2	Pyrene-d10	I.S.	I.S.	I.S.	I.S.	I.S.
5	Aldrin	14.95	14.58	14.56	14.86	15.01	14.79	0.22	1.49
6	Dieldrin	15.18	15.46	14.96	15.06	14.95	15.12	0.21	1.39
7	p,p'-DDE	14.95	15.08	15.14	15.26	14.54	14.99	0.28	1.87
8	p,p'-DDD	15.06	15.12	14.86	15.06	15.43	15.1	0.34	2.25
9	Endrin	15.85	15.42	14.98	15.56	15.23	15.4	0.4	2.60
10	p,p'-DDT	15.68	15.94	15.24	15.49	15.85	15.64	0.38	2.43

            Table. 3.9. Reappearance of organochlorine compounds (15 ng.L^-1)

No.	Compounds	1	2	3	4	5	Average	Deviation	CV%
IS1	Phenanthrene-d10	303181	299341	294163	319341	323039	307813	12691.3	4.12
1	a-HCH	6677	6568	6692	6768	6496	6640.2	107.68	1.62
2	b-HCH	5733	5551	5619	5751	5787	5688.2	99.15	1.74
3	y-HCH	5500	5740	5701	5740	5676	5671.4	99.61	1.76
4	d-HCH	4645	4583	4575	4583	4616	4600.4	29.51	0.64
IS2	Pyrene-d10	368078	346278	355603	346278	351225	353492	9033.70	2.56
5	Aldrin	3580	3396	3419	3396	3454	3449	76.98	2.23
6	Dieldrin	2178	2365	2443	2365	2219	2314	111.09	4.80
7	p,p'-DDE	17106	16751	15267	16751	16421	16459.2	709.13	4.31
8	p,p'-DDD	22665	24724	24690	24724	24456	24251.8	894.09	3.69
9	Endrin	1521	1696	1609	1596	1434	1571.2	98.69	6.28
10	p,p'-DDT	4918	4903	4821	4903	4807	4870.4	52.08	1.07

3.3. Problems encountered

The blank samples always be contaminated by some target compounds such as DBP, DEHP, etc (Fig.2.3). To overcome obstacles, before analysis we used the best solvents, cleanly instruments and using 1 blank sample for 5 samples. When quantitation the results were subtracted with blank sample. And water before used as blank sample was at least three times pretreated by dichlomethane following the extraction procedure of the analytical method applied. 

Similar to the comments provided by Shimadzu experts, the recoveries of alkylphenolic and bisphenol-A compounds (indicated by the recoveries of bisphenol-A-d16) were always recognized lower when the samples were prepared in the environment with high temperature (>25^oC). Therefore, all water samples of these two events were prepared at the temperature ranging from 15^oC - 20^oC. 

IV. CONCLUSIONS

60 water samples were collected at Red River, Thaibinh estuary and Tamgiang-Cauhai-Langco lagoon in the rainy and dry season. The samples were analyzed to assess the pollution of EDCs including organochlorine, alkylphenolic, bisphenol-A and phthalates compounds.We observed that concentrations of phthalates were ranged from ngL^-1to ten ngL^-1. Phthalates were recognized  higher in dry season and smaller in rainy season, specially at Hue. DEP, DBP, DEHA, DEHP were found in sample but under safe threshold. The concentrations of phthalates are decrease from Red river to Balat to Hue (22.9 ngL^-1 to 20.1 ngL^-1) in rainy season.

In comparison to the previous study in Tamgiang-Cauhai-Langco lagoon the total sum of found alkylphenolic compounds in 2001 was three times higher than those of the year 2000. While the total sum of the found alkylphenols in 2001 at sampling sites of Red River stayed almost unchanged compared to those of 2000, the found level of bisphenol-A in 2001 decreased to about only one third compared to the previous year.

In general, the level of EDCs were recognized higher in dry season, the total sum of p,p^’- DDT derivates continuously decreased and declined with the time and appeared as variation depending on the season. Unfortunately, we could not take samples in Red river and Balat estuary in dry season to follow the possible changes of the investigated compounds as depending on season as we did in Tamgiang-Cauhai-Langco lagoon. But we estimate, the trends of these pollutants would be staying quite similar as observed in previous years.

Similar to the study conducted in the year 2000, aldrin, dieldrin, endrin and particularly, hexachlorocyclohexane isomers were practically absent (below detection limits). Therefore, it probably affirms that these compounds were never used in significant amounts at the study areas. Concentrations of DDTs were revealed predominant at all sites, variability in season.

 V. REFERENCES

Anonymous (1997) Manual for Sample Collection and analysis. Environmental Monitoring and governance, UNU Project, The United Nations University.

Anonymous (1998) List of Pesticides Permitted, Restricted and Banned to Use in Vietnam. Ministry of agriculture and Rural Development, Vietnam.

A. Bachmann, P. Walet, P. Wijnen (1988) Applied and environmental microbiology.

Connel, D. W (1997) Basic Concepts of Environmental Chemistry. Lewis Publishers, New York.

O. Hutzinger (1991) Environmental chemistry. Vol. 3, part C, pp. 165-184

A. Johnson, D. Norton, B. Yake (1988) Archives of environmental contamination and toxicology. pp. 289-297

R. Robinson and F. Korte (1992) Chemosphere, Vol. 25, N₀. 5, pp. 719-725

Warhurst, M. (1994) An Environmental Assessment of Alkylphenol Ethoxylates and Alkylphenols. Friends of the Earth, Scotland.

APPEDIX A

Sampling collection information for EDCs

Table A.1. Sampling Collection information for EDCs in Red river

No	At site	Type of sample	Co - ordinate		Date	Remarks
			North	East
1	SH-1	RW	21^002.616'	105^051.660’	01/07/20	Rainy season
2	SH-2	RW	21^002.967’	105^051.354’	01/07/20	Rainy season
3	SH-3	RW	21^003.319’	105^051.198’	01/07/20	Rainy season
4	SH-4	RW	21^003.914’	105^051.141’	01/07/20	Rainy season
5	SH-5	RW	21^004.539’	105^050.603’	01/07/20	Rainy season

Table A.2. Sampling Collection Information for EDCs in Water from Balat estuary

No	At site	Type of sample	Co - ordinate		Date	Remarks
			North	East
1	S1	RW	20^015.575’	106^034.149’	01/07/13	Rainy season
2	S2	RW	20^016.880’	106^033.802’	01/07/13	Rainy season
3	S3	RW	20^016.804’	106^033.809’	01/07/13	Rainy season
4	S4	RW	20^017.109’	106^033.578’	01/07/13	Rainy season
5	S5	RW	20^017.245’	106^033.401’	01/07/13	Rainy season
6	S6	RW	20^017.435’	106^033.280’	01/07/13	Rainy season
7	S7	RW	20^017.905’	106^032.867'	01/07/13	Rainy season
8	S8	RW	20^017.654’	106^032.912’	01/07/14	Rainy season
9	S9	RW	20^017.019’	106^033.512’	01/07/14	Rainy season
10	S10	RW	20^016.602’	106^033.858'	01/07/14	Rainy season
11	S11	RW	20^015.855’	106^034.704’	01/07/14	Rainy season
12	S12	RW	20^014.595’	106^035.306’	01/07/14	Rainy season
13	S13	RW	20^014.588’	106^035.493’	01/07/14	Rainy season
14	S14	RW	20^015.057’	106^035.217’	01/07/14	Rainy season
15	S15	RW	20^016.325’	106^034.595’	01/07/14	Rainy season

Table A.3. Sampling Collection Information for EDCs in Water Sample in Hue

No	At site	Type of sample	Co - ordinate		Date	Remarks
			North	East
1	M1-1	SW	16^038.918’	107^027.710’	01/06/18	Dry season
	M1-2	SW	16^038.645’	107^027.570’	01/06/18	Dry season
	M1-3	SW	16^038.415’	107^027.463’	01/06/18	Dry season
2	M2-1	SW	16^037.129’	107^030.988’	01/06/18	Dry season
	M2-2	SW	16^036.927’	107^030.931’	01/06/18	Dry season
3	M3-1	SW	16^035.609’	107^033.851’	01/06/18	Dry season
	M3-2	SW	16^035.400’	107^033.672’	01/06/18	Dry season
	M3-3	SW	16^035.136’	107^033.583’	01/06/18	Dry season
4	M4	SW	16^033.635’	107^037.253’	01/06/18	Dry season
5	M5	SW