Preliminary data of the biodiversity in the area

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Development of Water Quality Index for Coastal Zone and Application in the Haạ Long Bay

Nguyễn Thị Thế Nguyên

^1,

*, Đồng Kim Loan

²

, Nguyễn Chu Hồi

²

^*

Nguyen Thi The Nguyen

^*,

¹

, Dong Kim Loan

²

, Nguyen Chu Hoi

²

^*

1 Water Resources University

2 VNU University of Science² VNU University of Science, 334 Nguyen TraiNguyễn Trãi, Thanh Xuân, Hanoi, Vietnam

Received 05 October 2013

Revised 14 November 2013; Accepted 15 December 2013Received 6 Frbruary 2013 Revised 16 March 2013; Accepted 20 June 2013

Abstract: In this study, a water quality index (WQIHL) has beenwas developed in accordance with the nature of coastal zone and applied to assess the water quality in Ha Long Bay. The nNine parameters, including %DOsat (0.08), COD (0.11), TOC (0.08), oil and grease (0.17) total coliforms or feacal coliform (0.07), TSS (0.17), TN or NH4 (0.11), TP or PO+ 43- (0.11) and chlorophyll a (0.11) are employed for the estimation of water quality. The Nnumbers in the parentheses areindicate weight of each parameter. Sub-indices are built based on the QCVN 10:2008/MONRE, the standards on coastal water quality of ASEAN, Australia, Japan … and other requirements offor water quality forin marine ecosystems. The aAssessment of the eclipsing and ambiguous effects and the sensitivity of four aggregation functions reveal that the weighted geometric mean function is the most appropriate to calculate WQIHL with the selected weights. The application of the developed WQIHL in the Haạ Long Bay shows that the water quality in the core zone is good, except some tourist areas and fishing villages. The buffer zone of the Bay possesses poor water quality. The WQIHL formula can be a good tool for water quality management and planning, which supports for the integrated coastal zone management.

Keywords: Water quality index, weighted geometric mean function, coastal zone, Haạ Long Bay.

1. Introduction ^*

The use of water quality index gained acceptance in many years before. It is a tool to improve understanding of water quality issues by integrating complex data and generating different levels that describes water quality status and evaluates water quality trends [1]

[16]. In this way, the index can be used to assess water quality relative to its desirable

* Corresponding author. Tel.: 84-983033532 E-mail: nguyenntt@wru.edu.vn

state (as defined by water quality objectives) and to provide insight into the degree to which water quality is affected by human activity.

Although some information is lost when integrating multiple water quality variables, this loss is outweighed by the gain in understanding of water quality issues by the public and decision makers [2]. [14].

A review of studies and usages of water quality index around the world (by the authors) reveals that few studies involved in estuaries

and coastal zone and the remainder was restricted to inland water or surface water. In Vietnam, there is not any study about WQI for the coastal area.

In this study, a WQI is developed suitably with coastal zone conditions and tried to apply in assessment of water quality in the Ha Long Bay. Coastal characteristics and issues in the Ha Long Bay are taken into account during the WQI development. Therefore, the study result is significant for tasks of environmental assessment, planning and management in the coastal zone.

2. Methodology

There are four steps involved in the development of most water quality indices [1, 3] [16], .. These include: (1) selecting the set

of water quality parameters

(indicators/variables) of concern, (2) weighting the indicators based on their relative importance to overall water quality, (3) developing sub indices for comparing indicators on a common scale (Indicator transformation), and (4) formulating and computing the overall water quality index (Aggregation function).

2.1. Indicator selection

There are six criteria for a meaningful variable [4] [18], including: (1) Water quality variables that are widely and regularly measured; (2) Variables that have clear effects on aquatic life, recreational use, or both; (3) Variables that have man-made sources as opposed to natural sources; (4) Variables those are amenable to control through pollution abatement programs, (5) Realistic ranges of each variable - from no pollution to gross pollution, (6) Sensitivity to reasonably small

changes in water quality. In addition, Dunnette (1979) and Tebbutt T.H.Y (2002) recommended that variables of concern should be selected from 5 commonly recognized impairment categories like (1) oxygen status and demand, (2) eutrophication, (3) health aspect, (4) physical characteristics, and (5) solid substances [5-7]. [15], [17], .

2.2. Indicator weighting

It is also generally acknowledged that some indicators are more important to

“average water quality” than others [8] . It is thus necessary to weight the indicators appropriately. In this study, the weight of the indicator is determined through importance and roles of the indicator to aquatic system and current status of that parameter in the Ha Long Bay. Temporary weight is developed by dividing the significant rating by the average significance rating of individual parameters.

Then, weighting scale for each parameter is defined as the ratio of temporary weight to the sum of temporary weights. Final weight (Weighting scale) is obtained by approximating the ratio of temporary weight for each variable to the sum of temporary weights [4]. [18].

2.3. Indicator transformation

Water quality indicators are generally in many different units. This makes simple aggregation impossible. As a consequence, another important step in developing an index involves a transformation of all indicators to an equal, dimensionless scale. This results in sub indices [3]. . In this study, the sub indices are from 1 to 100 which represent the poorest and the highest water quality respectively. The development of the sub-index of each selected variable in this study bases on following information: (1) National technical regulation

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on coastal water quality - QCVN 10:

2008/BTNMT, (2) Marine and coastal water quality standards and criteria of ASEAN, Thailand, Indonesia, Japan, Australia [9] [13], and (3) Requirements of water quality for coral reef and seabed grass.

2.34. Aggregation function

The aggregation process is one of the most important steps in calculating any environmental index. Generally, aggregation functions, either additive or multiplicative forms, are suffered from both eclipsing and ambiguous effects [1] [16]. There are some kinds of functions to calculate an aggregated score (index score) for WQI. To minimize the ambiguity and eclipsing effect, it is necessary to identity an appropriate function for calculating an aggregated score. Four kinds of functions have been considered in this study.

They are the weighted Solway function [8] , the weighted arithmetic mean function [10] , the weighted geometric function [10] and the weighted harmonic mean function [1]. [16].

3. Results and discussions

3.1. Variable selection

(1) Oxygen status and demand: Indicator for the oxygen status in water body is %DOsat. Organic matter has the greatest impact on dissolved oxygen concentrations [11]. [1].

Consequently, COD and oil and grease should be taken into account. Oil pollution prevents not only oxygen in atmosphere from dissolving into the sea water but also phytoplankton from catching carbonic in atmosphere for photosynthetic reaction. In addition, the process of biodegradation of oil makes some microorganisms more active and then reduces the amount of oxygen in the water. TOC is

also an important parameter is selected as the Vietnamese coast receives many organic pollutants and grease. The TOC content is a measure of the concentration of organically bound carbon and is therefore a direct indication of the pollution levels by organic compounds [12]. [12].

(2) Eutrophication: the indicators for the eutrophication are: TN, NO3- , NO2- , NH4+ , TP, PO4 and chlorophyll-a. The chosen indicators3-

are TN, TP, and chlorophyll-a. The two parametters TN and TP can be replace by NH4 +

and PO43- . The two parameters NO3- , NO2 can-

be ignored in calculating the WQI for coastal waters for the following reasons: Due to tidal activity in the coastal zone, NO2- is not high and easily transformed into NO3- . High concentration of NO3- makes algae flourish and thereby causes adverse effects to the environment if the eutrophication occurs.

Then, chlorophyll a is a more important parameter to measure the eutrophic state than NO3- .

(3) Health aspect: The parameters in this group include total coliform, fecal coliform and heavy metal [9, 11]. [1], [13]. The heavy metal concentrations are not selected to develop WQI for the following reason:

Theoretically, the ions of heavy metals in water are usually absorbed by clay particles and suspended sediment. Due to high salinity and pH in the coastal areas, the clay particles and suspended sediment flocculation is settle down and make the content of heavy metals in the water are much lower than those in the sediments. Therefore, the concentrations of heavy metals in coastal water do not adequately reflect the level of heavy metal pollution in coastal areas. That kind of pollution needs to be assessed by the accumulation of heavy metals in plankton, benthic organisms or bed sediment. Such assessment is beyond the scope of this study.

For the reason above, the selected parameter is

total coliforms (or Feacal coliform). This parameter needs to be controlled in the coastal areas having water sports activities [9] [13].

Currently, the total coliforms is monitoring quite often so that it is convenient for evaluation of microbial pollution in general.

However, to strictly control the quality of the coastal water used for aquatic sports activities such as swimming or water skiing, the fecal coliform parameter is more important and should be included in monitoring programs.

(4) Physical characteristics: While the importance of this category is evident for freshwater systems, the meaning of physical characteristics in term of coastal zone is not significant for coastal water [8] .

Due to the dynamic nature of estuarine and coastal water masses under “normal”

conditions, physical characteristics in that water bodies are highly variable and could not be controlled. The pH is strongly controlled by the mixing of marine and fresh water [5] [15].

Given the buffering capacity of sea water, the pH of river water entering an estuary will be driven to 8. Thus, the pH of estuarine and coastal water generally increases towards the sea. Salinity (measure of total dissolved solids) is a much more important indicator of the extend of seawater mixing than water quality impairment [5] [15]. In fact, it is the brackish nature of estuarine and coastal water that makes this habitat unique and contributes to its resource value. Temperature of coastal water greatly depends on solar energy, mixing of sea currents and other water than human impacts.

Consequently, this parameter is not considered as pollutant. However, oxygen concentration in water body will decrease when the temperature raises. Thus, the temperature should be taken into account in process of oxygen concentration determination.

As a consequence of above, the parameters of the physical characteristics are not chosen for WQI in the coastal zone.

(5) Solid substances. The selected parameter is total suspended solids (TSS). In the water, TSS consists of organic matter, minerals, heavy metals, sulfur, algae (including toxic algae), and bacteria (including pathogenic bacteria). TSS contributes to turbidity of the water and reduces not only the amount of transmitted light needed for photosynthesis but also the landscape of the coast. High TSS concentration (above 20 mg/l) will degrade or can destroy mangrove, coral reefs, sea grass ecosystems.

The selected parameters for the WQI for the coastal zone are summarized in the table 1.

3.2. Indicator weighting

The weights of parameters are determined depending on whether they have direct or indirect effects on the ecosystem. Two types of parameters that directly affect aquatic ecosystems can be distinguished: those that are directly toxic to biota, and those that, while not directly toxic, can result in adverse changes to the ecosystem [11] [1]. The parameters that directly affect aquatic ecosystems have higher weight than those that, while not directly toxic, can result in adverse changes to the ecosystem.

The detail importance and final weights are shown in the table 1.

3.3. Sub-indices

Sub-indices (qi) are within the range 1-100 (1 is the worst and 100 is best). They are divided into 3 parts (1-34-67-100) which are followed the QCVN 10:2008/MONRE and other document listed in part 2.2. The sub- index transformation curses of each selected variable have been developed and shown in figure 1. They are developed based on criteria of protecting aquatic life in coastal water and human contact. The value of the sub-index at an any concentration Cq is calculated by referring to the sub-index transformation

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curses (Figure 1) or by the method of linear interpolation of the values in Table 2.

Table 1. 1 The selected parameters for the WQI in the coastal zone and their weights No. Parametter Importance Temporary

weight Final

weight Note 1 Oil and grease;

TSS 1 2.5 0.17 Stressors directly toxic to marine

ecosystems [11] [1]

2

COD, TN (or NH4+ ), TP (or PO43- ), chlorophyll a

1.5 1.7 0.11 Stressors that are not directly toxic but can directly affect marine ecosystems [9, 11]

[1][13]

3 TOC 2 1.3 0.08 - Assess the level of organic pollution which is major pollution problem in the Ha Long Bay

4

Total coliforms (or Feacal coliform),

DO 2.5 1 0.07

- Total coliforms (or Feacal coliform) directly toxic to human being [9] [13]

- DO affect process of respiration of marine creature [9, 11] [1][13]

Table 2. 2 Sub-index values (qi)

i qi

Concentration values (Ci) for each parameter TOC

(mg/l) COD

(mg/l) DO%sat Oil and grease

(mg/l) TN

(mg/l) TP

(mg/l)

1 100 ≤ 1.2 ≤ 3 100 0 ≤ 0.25 ≤ 0.02

2 67 1.6 4 65 or 140 0.1 0.35 0.05

3 34 10 25 40 0.2 0.75 0.5

4 1 > 20 > 50 20 > 0.3 > 1.5 > 1

i qi PO43— P (mg/l)

NH4+ -N (mg/l)

Chla (µg/l)

T. Coli (MPN/100ml)

F. Coli (F.Coli/100ml)

TSS (mg/l)

1 100 ≤0.015 ≤ 0.1 ≤ 1.4 ≤500 ≤100 ≤ 20

2 67 0.045 0.3 3 1000 - 50

3 34 0.08 0.5 10 - 500 -

4 1 > 0.5 > 1 > 20 >2000 >1000 >100

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Figure 1. The sub-index transformation curses of each selected variable.

dg

3.4. Aggregation function

In this study, for the purpose of minimizing the eclipsing and ambiguous effects on the formulation for WQI, the four aggregation functions, including the Solway function, the weighted arithmetic mean function, the weighted geometric function and the weighted harmonic mean function, were chosen to compare the eclipsing and ambiguous effects on the final results of WQI.

These functions are widely used to develop WQI over the world. The aggregation function should be also sensitive to small changes in water quality.

The assessments of the eclipsing and ambiguous effects on the final results of WQI and the sensitivity of the aggregation function are done by verifying one of the qi values from 1 to 100. Then, the eclipsing and ambiguous effects, the sensitivity and the nature of easy application of the four functions mentioned above are evaluated by scoring from 1 to 4.

The more easily functions calculate, the higher score they have; the more ambiguous the functions are, the lower score they get; the more eclipsing the functions are, the lower score they get; the more sensitive the functions are, the higher score the functions are (Table 3).

Table 3. 3 General assessment of the average functions TT Property Weighted

arithmetic Weighted

geometric Weighted

harmonic Weighted Solway

1 Easy to apply 4 4 2 3

2 Ambiguous 4 3 2 1

3 Eclipsing 1 3 4 4

4 Sensitive 1 3 3 4

Sum 10 13 11 12

Table 4. 4 Thresholds ofwaterqualityclassification

No. Threshold States of parameters in comparison with the allowance in the QCVN 10:2008/BTNMT and others

Upper limit 100

1 Excellent From good threshold to 100

2 Good One water quality parameter exceed allowance for aquaculture and aquatic conservation (qi = 67) or qi min ≥ 67

3 Medium One water quality parameter exceed allowance for beach or areas for recreation activities with directed water contact (qi = 34)

4 Bad One water quality parameter exceed allowance for “other areas” like ports … (qi = 1) 5 Very bad Three water quality parameters exceeds allowance for “other areas” like ports …(qi = 1)

Lower limit 1

Table 5. 5 Water quality classification and usages No. WQIHL Water quality Water use ability

1 97 - 100 Excellent Can be used for any purpose.

2 92 – 96 Good Can be used for any purpose, except protection of aquatic life or special aquaculture

3 70 - 91 Medium Tourism, recreation without direct water contract, ports and navigation, industrial water supply

4 35 - 69 Bad Ports and navigation, industrial water supply or other purposes which do not need high water quality.

5 1- 34 Very bad Ports and navigation only gj

Based on the analysis results in Table 3, the weighted geometric mean function has the highest score. Consequently, the weighted geometric mean is use to build WQI for the coastal zone. With the selected weights in this study, the weighted geometric mean has a small eclipsing and ambiguous effects and a high sensitivity. In addition, the weighted geometric mean is easy to apply in the comparison to the harmonic mean or the Solway. Finally, the WQI for the coastal zone is following:

WQI HL =

n i 1

1/ w 1

(

ⁿ q_i^wi

)





In which, qi and wi are the sub-indices and weights of the chosen parameters which shown in the table 1.

3.5. Water quality classification and range scales

In order to evaluate water quality and environmental management effectiveness, it is necessary to have descriptor categories and ranges of WQI scores. Classification scale is determined based on the level and number of parameters violating the allowable limits. WQI

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values are divided into 5 ranges which are very good, good, medium, bad and very bad as shown in table 4. Waterqualityclassification is calculated by the WQI HL formula with the thresholds in the table 4. The final results of water quality classification are summarized in table 5.

3.6. Application in assessment of water quality in the Ha Long Bay

* Data: Monitoring data at 12 points in 4/2013 (table 6) and at 32 points in 8/2013 in the Ha Long Bay.

* Results and discussions:: The example results are shown in table 6 and figure 1. It can be seen that the water quality in the buffer zone of the bay is from very bad to medium, while that in the core is still good to very good.

However, there is local pollution in the core zone, especially at the tourist areas and fishing villages. In the figure 1, that locations are monitoring point number 11 (Thien Cung – Dau Go islands), 12 (Titop island), 17 (Cong Do area), 19 (Hoa Cuong fishing village), 20 (Cua Van fishing village).

The calculation results also reveal that there are differences between the three

calculation methods. For example at the monitoring point of Cua Van fishing village, the two formulas WQIHL and WQIPNH show that the water quality is very good, whereas the CWQI formula gives bad result. Monitoring results here show that most of the water quality parameters are within the allowable limits, only COD value (3.1 mg/l) was slightly higher than the allowance (3 mg/l) of QCVN 10:2008/BTNMT for aquatic conservation areas. The CWQI formula results in poor water quality due to the parameter F1 (% ratio between the number of failed parameters and the total number of parameters) affects largely to the final results. This is one of the limitations pointed out in the workshop on water quality indicators in Canada in 2003 [14].

It can be concluded that the usage of the WQIHL to evaluate and classify the water quality in the Ha Long bay with monitoring data in 4/2013 and in 8/2013 gives quite reasonable results. Still it needs more testing with other monitoring sites in the coastal zone of Vietnam.

Table 6. 6 Some examples of the water quality classification in the Ha Long Bay in 4/2013

with different WQI formula

No. Monitoring point WQIHL CWQI WQI P.N.H

1 Bang bridge 69 Medium 37 Bad 88 Bad to

Medium

2 At the middle of Cua Luc Bay 48 Bad 27 Bad 54 Medium

3 Bai Chay bridge 55 Bad 29 Bad 71 Medium

4 Bai Chay beach 60 Bad 20 Bad 32 Very bad

5 Bai Chay tourist wharf 30 Very bad 29 Bad 61 Medium

6 Tuan Chau beach 66 Bad to

Medium 20 Bad 33 Very bad

7 Ha Long I market 22 Very bad 24 Bad 31 Very bad

8 Pillar 5 - pillar 8 56 Bad 33 Bad 75 Medium

9 Nam Cau Trang wharf 49 Bad 40 Bad 50 Bad

10 Islet 1 100 Excellent 100 Excellent 100 Excellent

11 Titop beach 96 Excellent 100 Excellent 100 Excellent

12 Cua Van fishing village 98 Excellent 41 Bad 97 Excellent

Color WQI Water

quality clarification 97-100 Excellent

92-96 Good

70-91 Medium

35-70 Bad

1-34 Very bad

Figure 1. Some examples of the water quality classification in the Ha Long Bay in 8/2013.

3.7. Overall assessment of the water quality index for the coastal zone

The WQIHL is evaluated following 15 characteristics that an ideal water quality index should possess [10] . . Evaluation results show that the WQIHL formula has met 13 out of 15 characteristics for the ideal water quality index recommended by the Environmental Protection Agency of the U.S. This is due to the keeping abreast of the recommended characteristics in the construction of the WQIHL. Thus, the WQIHL formula can be used to assess the status and changes in water quality in the coastal zone and serve the management and conservation natural ecosystems here.

4. Conclusion

In this study, the water quality index has been built in accordance with the nature the coastal zone in Ha Long Bay. The index consists of 9 parameters, including %DOsat

(0.07), COD (0.11), TOC (0.08), oil and grease (0.17) total coliforms or feacal coliform (0.07), TSS (0.17), TN or NH4 (0.11), TP or PO+ 43- (0.11) and chlorophyll a (0.11). The weighted geometric mean function is used to integrate sub-indices. The WQIHL provides a convenient way for evaluating the water quality of the coastal zone in terms of the specific water use for marine ecosystem protection and human contact, and comparing water quality among different areas of the coast. The application of the developed WQIHL shows that the water environment in the core zone of Ha Long Bay is good, except some points that concentrate tourist activities and fishing villages. The core zone currently is subjected to damage by the poor water quality in the buffer zone which is

The buffer zone The core zone

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currently impacted by socio - economic activities in Ha Long city.

References

[1] Cude Curtis G. (2001). Oregon water quality: A tool for evaluating water quality management effectiveness. Journal of American Water Resources Association. Vol. 37, No. 1, pages 125 – 137.

[2] CCME (2003). National Water Quality Index Workshop Proceedings, Halifax, Nova Scotia, Canada.

[3] Ram Pal Singh et al. (2008). “Selection of Suitable Aggregation Function for Estimation of Aggregate Pollution Index for River Ganges in India”, Journal of Environmental Engineering, Vol 134, No. 8, August 1 (2008). ©ASCE, ISSN 0733-9372/2008/8-689–701.

[4] Ott W.R (1978). Environmental indices theory and practice. Ann Arbor Science. Michigan, USA.

[5] Cooper J. A. G. (2000). Geomorphology, ichthyofauna, water quality and aesthetics of South African estuaries. Technical report.

Department of Environmental Affairs & Tourism of South Africa.

[6] Dunnette, D.A. (1979). A geographically variable water quality index used in Oregon. Journal of Water Pollution Control Federation 51(1), pages 53-61.

[7] Tebbutt T.H.Y (2002). Principles of Water Quality Control. Butterworth Heinemann (An imprint of Elservier Science).

[8] Tim Carruthers and Catherine Wazinak (2004).

Development of Water Quality Index for Maryland Coastal Bays. Maryland Department of Natural Resources. Annapolis, MD 21401. US.

[9] ASEAN Secretariat (2008). ASEAN Marine Water Quality: Management Guidline and Monitoring.

[10] U.S. EPA (1978). Water Quality Indices: A survey of indices used in the United States. U.S.

Environmental Protection Agency.

[11] ANZECC & ARMCANZ (2000). Australian water quality guidelines for fresh and marine waters. Australian and New Zealand

Environment and Conservation Council Agriculture and Resource Management Council of Australia and New Zealand. Canberra, Australia.

[12] APHA (2005). Standard methods for the Examination of Water and Wastewater. 21st Edition. American Public Health Association, Washington, D.C.

[13] ASEAN Secretariat (2008). ASEAN Marine Water Quality: Management Guidline and Monitoring

[14] CCME (2003). National Water Quality Index Workshop Proceedings, Halifax, Nova Scotia, Canada.

[15] Cooper J. A. G. (2000). Geomorphology, ichthyofauna, water quality and aesthetics of South African estuaries. Technical report.

Department of Environmental Affairs & Tourism of South Africa.

[16] Cude Curtis G. (2001). Oregon water quality: A tool for evaluating water quality management effectiveness. Journal of American Water Resources Association. Vol. 37, No. 1, pages 125 - 137

[17] Dunnette, D.A. (1979). A geographically variable water quality index used in Oregon. Journal of Water Pollution Control Federation 51(1), pages 53-61

[18] Ott W.R (1978). Environmental indices theory and practice. Ann Arbor Science. Michigan, USA

[19] Pham Ngoc Ho (2012), Total Water Quality Index Using Weighting Factors and Standardized into a Parameter. Available online at www.tshe.org/EA EnvironmentAsia 5(2) (2012) 63-69

Ram Pal Singh et al. (2008). “Selection of Suitable Aggregation Function for Estimation of Aggregate Pollution Index for River Ganges in India”, Journal of Environmental Engineering, Vol 134, No. 8, August 1 (2008). ©ASCE, ISSN 0733- 9372/2008/8-689–701

U.S. EPA (1978). Water Quality Indices: A survey of indices used in the United States. U.S.

Environmental Protection Agency

Tebbutt T.H.Y (2002). Principles of Water Quality Control. Butterworth Heinemann (An imprint of Elservier Science)

Xây dựng chỉ số chất lượng nước cho vùng ven biển và áp dụng đánh giá chất lượng nước vịnh Hạ Long

Nguyễn Thị Thế Nguyên

¹

^*,

, Đồng Kim Loan

^{1 2}

²

, Nguyễn Chu Hồi

²

^*

²

1 ¹ Đại học Thủy Lợi

2 Trường Đại học Khoa học Tự nhiên – Đại học Quốc gia Hà Nội, ĐHQGHN, 334 Nguyễn Trãi, Thanh² Xuân, Hà Nội, Việt Nam

Received 6 Frbruary 2013

Revised 16 March 2013; Accepted 20 June 2013

Tóm tắt: Trong nghiên cứu này, chỉ số chất lượng nước (WQIHL) đã được xây dựng phù hợp với tính chất của vùng biển ven bờ và áp dụng để đánh giá chất lượng nước vịnh Hạ Long. Các thông số sử dụng để tính toán WQI là %DOBH (0.07), COD (0.11), TOC (0.08), dầu và mỡ (0.17) tổng coliforms hoặc feacal coliform (0.07), TSS (0.17), TN hoặc NH4+ (0.11), TP hoặc PO43- (0.11) và chlorophyll a (0.11). Trọng số của các thông số được ghi trong dấu ngoặc. Các chỉ số phụ được xây dựng dựa trên QCVN 10:2008/MONRE, các tiêu chuẩn chất lượng nước biển ven bờ của ASEAN, Australia, Nhật … và các yêu cầu chất lượng nước cho các hệ sinh thái biển. Quá trình đánh giá tính mơ hồ, tính che khuất, độ nhạy và mức độ dễ tính toán của các phương pháp tổng hợp chỉ số phụ thường dùng cho thấy hàm tích có trọng số là phương pháp tổng hợp thích hợp nhất để tính WQIHL. Việc áp dụng công thức WQIHL để đánh giá chất lượng nước vịnh Hạ Long cho thấy chất lượng nước vùng lõi vịnh còn tốt, trừ một số khu vực tập trung hoạt động du lịch hoặc làng chài. Tuy nhiên, vùng lõi vịnh đang chịu áp lực lớn bởi chất lượng nước khá xấu tại vùng đệm. Công thức WQIHL là một trong những công cụ hiệu quả trong quản lí và phân vùng chất lượng nước nhằm phục vụ quá trình quản lí tổng hợp vùng bờ.

Từ khóa:Cchỉ số chất lượng nước, tích có trọng số, vùng ven bờ, vịnh Hạ Long.

.

Geochemical characteristics of Quaternary sediments

in the Hanoi area

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Dang Mai1,*, Nguyen Thuy Duong1, Tong Thi Thu Ha2, Dang Quang Khang1, Nguyen Van Niem2, Dinh Xuan Than

h

¹

1

Falculty

of Geology, VNU University of Science, 334 Nguyen Trai, Hanoi, Vietnam

2

Vietnam Institute of Geosciences and Mineral Resources

Nhận ngày 01 tháng 4 3 năm 2013

Chấp nhận xuất bảnChỉnh sửa ngày 029 8 tháng 4 năm 2013; chấp nhận đăng ngày 07 tháng 5 năm 2013

Abstract. 17 samples collected from two drill holes (QO.01 and QO.03) at Quoc Oai (Hanoi)

were analysed the main chemical compositions in oxides SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O by XRF method and some trace metal elements such as As, Cu, Pb, Zn, Sb, V, Cr, Ni, Cd by AAS method. According to these results, content of SiO2, Al2O3, Fe2O3 are the highest, the next is K2O, TiO2 and the other oxides are very low. The sediments in the Vinh Phuc formation have rich Fe2O3 by laterization, whereas those in the Hai Hung formation have rich K2O by the potassium-absorption in the organic matters. In the sediments, there are close relationship between the alkaline and alkaline earth elements, and the titan oxide is positively correlative with Al

2

O

3

and Fe

2

O

3

.

The arsenic content in almost samples is

higher than 10mg/kg, somewhere else up to 41 mg/kg, exceeding many folds compared to the average level found in the earth’s crust and in the clay sedimentary. The antimony content (Sb) is also increased high with the clark index from 8.06 to 125.6 mg/kg. The behaviors of As, Cu, Pb, Zn are very similar to each other in the samples of 02 holes QO.01 and QO.03, that is highly concentrated in the upper

sediments of the Vinh Phuc formation and in the rich-organic lower sediments of the Hai Hung formation. It seem probable that As is existed as sulfur phases and absorbed by the organic materials. It is able to infer sedimentary source and accumulated arsenic content from the linear correlation coefficient between siderophile and Cu, As, which, as a basic for judging the cause pollution of Hanoi groundwater.

Keywords: Vinh Phuc formation; arsenic, antimony, copper; siderophile elements; drill hole;

Hanoi area 1.

Introduction^

According to finding

of researcher at Vietnam and abroad, arsenic concenstrations in the groundwaters of the Holocene and Pleistocene layers

in Hanoi is very high, at many sites higher than the level permitted by the World Health

Organization (WHO

) (Do Trong Su, 2000; Pham Hung Viet, 2001; Nguyen Van Dan, 2004; Nguyen Kim Dung, 2006; Berg.M., 2008: Norman J., 2008). Arsenic concenstrations in water well in Hoai Duc, Phu Xuyen, Thuong Tin is more than 100g/l that is exceeded 10 time comparing to WHO’s criteria. According to Bui Huu Viet (2010) soil in the west of Hanoi has been polluted by heavy elements, such as As, Cu, Ni, Mn, Cr, Zn, Cd.

Content of trace elements found in the soil and the water have a close relationship with the host rocks that first of all is the Quaternary sedimentary. Indeed, on the causes of arsenic

Tác giả liên hệ. ĐT: 84-4-38584943.

E-mail: anhtn@vnu.edu.vn

contamination, most researchers cling to the point of view that, the arsenic found in groundwater originated from the Quaternary sediments [1, 3, 5, 6, 9, 10]

In order to find more evidences and to know geochemical characteristics at the soil of the Quaternary sediments in the Hanoi, arsenic and heavy metal elements concentration were researched in Quaternary sediments of Quoc Oai (Hanoi).

2.

Methods

The sediment samples were collected in 3 deep drill holes, which belonged to project VINOGEO. One of 3 drill holes that names QO.03 was in Tam village, Thach Than commune, Quoc Oai district (Ha Noi) and the othes were ịn Quoc Oai district (Ha Noi). The depths of the drill holes were 48, 53 and 42 m. The drill hole samples were collected about 300gr for each 1m depth and packaged in the polypropylene bags at the sites.

The major elements and some heavy metals (such as: V, Cu, Cr, Ni, Sr, Ba, Zn, Rb, Zr) chemical compositions of sedimentary were determined by X-ray Fluorescent (XRF Philips 2404). The heavy metals, such as As, Pb, Cu, Zn, Cd, were analyzed by atomic absorption spectrometry method (AAS). As was analysed on an atomic absorption spectrometry device employing a graphite burnt furnace (Perkin-Elmer 4110 ZL Zeeman), and the other elements were determined by a flame absorption spectrometry (Analytik Jena, AAS Vario 6).

3. General ideas on the Quaternary

sediments at the Hanoi

area

The Quaternary sediments in Ha Noi belong to 5 formations whose age were from early Pleistocene to Holocene, such as: 1) Le Chi formation; 2) Ha Noi formation; 3) Vinh Phuc formation; 4) Hai Hung formation and 5) Thai Binh formation (Ngo Quang Toan et al, 1998).

The Le Chi formation (

Q¹1lc

): includes early Pleistocene’s fluvial deposits; was not appear in the surface and only found them in drill holes at depths from 45 to 80m. Their thickness was from 2.5 to 24.5m. The

lithological compositions

of the Le Chi formation include: pebble (

quartz, silica, marble)

,

gravel, sand, silt, brown-gray clay

…

The Ha Noi formation (Q

12-3

hn), that aged in middle-late Pleistocen, was formed from the fluvial and diluvial deposits. They were distributed in the edges of mounds, hills and plains of Ba Vi, Soc Son include Xuan Mai, Thach That, Hoa Lac, Ba Vi, Da Phuc, Kim Anh, Minh Tri areas. Their materials were cobble, pebble, gravel and yellow clay-silt layer at the upper part. In some areas around hills and mounds, the upper part of the sediment were hardly weathered to form a young laterite layer. The fluvial deposits could be found in almost drill holes and their thickness were from 9.9 to 34m.

This

formation

could be considered as

the main

underground water

containing object

of the Hanoi

. In relationship to other formations, the Ha Noi formation lies unconformable upon the Le Chi formation and was covered unconformable by the Vinh Phuc formation.

The Vinh Phuc formation (Q

13

vp), which was formed in late-Pleistocene, occurred as the first

bench (the area exposed on the surface) and widely distributed at Soc Son, Dong Anh, Thach

That, Quoc Oai, Chuong My, Xuan Mai and Co Nhue. They were at the absolute altitude of 8-

20m; whereas down in the plains, from South Dong Anh, Co Nhue to further south, they were

1-10

appeared at 2-26.5 m deep of the drill holes. The sedimentary origin of the Vinh Phuc formation were fluvial, fluviolacustrine, fluviomarine. Material of fluvial deposit includes

gravel, sand, quartz sand, silt, clay. Their structure was oblique lamination.

The laterized sedimentary surface was mottled yellow-gray and brown-red. The fluviolacustrine was restrictedly distributed and includes silt, gray and dark-gray clay, white-gray kaolin clay containing late-Pleistocene floral relics. The composition of fluviomarine was silty clay mixed with gray sand. Their surface was weathered mottled.

In Hanoi area, the origin of Hai Hung formation (Q

21-2

hh) was bog lake, fluviomarine and marine. The bog lake sediment whose material was dark gray silty clay containing floral relics and lens-shaped peat, was formed before the Flandrian transgression. The components of the fluviomarine sediments mainly include

silty clay fixed fine-grained sand

, dark gray silty sand, peat containing floral relic and foraminifera that was appeared in the early-middle Holocene. The marine sediments belong to lagoon phase mainly include clay, silty clay mixed with a little fine-grained sand that is green gray or yellow gray, plastic and smooth. The clay mineral association are: hydromica, kaolinite, montmorilonite, chlorite

The Thai Binh formation (Q

23

tb) includes the modern sediments that was formed after the marine regression period. The formation’s deposits belong to the inner-dyke and outer-dyke alluvial facies. Their composition was sand, silt, clay, gravel, pebble, grit.

4. Results and discussion Major

compositions

[1] Table 1. Oxide contents (% wt.) of Quaternary sediments in Hanoi area Samples Drill

hole

Depth

(m) SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O

NH.07 QO-01 9.2 61.96 0.90 17.77 7.29 0.04 1.46 0.29 0.58 3.09

NH.10 QO-01 11.7 46.92 2.79 21.82 16.79 0.03 0.45 0.17 0.10 0.88

NH.17 QO-01 20.2 75.61 1.26 6.31 11.63 0.03 0.12 0.03 0.01 0.34

NH.21 QO-01 25.7 43.57 4.02 30.42 8.39 0.01 0.43 0.11 0.07 1.23

NH.25 QO-01 35.7 48.16 2.80 21.63 16.06 0.06 0.49 0.11 0.08 1.46

NH.30 QO-01 44.7 60.03 1.97 19.33 8.49 0.06 0.58 0.18 0.08 1.66

NH.65 QO-03 3.7 71.96 0.67 10.20 7.21 0.10 0.94 0.44 0.73 2.00

NH.66 QO-03 4.3 57.00 0.86 21.43 6.19 0.08 1.67 0.34 0.45 3.32

NH.69 QO-03 8.3 60.10 0.88 17.32 5.03 0.04 1.72 0.49 0.61 2.94

NH.71 QO-03 9.8 68.26 0.74 14.28 6.77 0.03 0.64 0.22 0.13 1.97

NH.72 QO-03 12.3 75.76 0.62 11.08 4.45 0.03 0.49 0.14 0.12 1.91

NH.75 QO-03 19.2 72.20 1.85 15.25 2.07 0.02 0.53 0.08 0.10 1.40

NH.76 QO-03 20.8 68.54 1.91 16.90 3.44 0.02 0.56 0.10 0.10 1.43

NH.77 QO-03 22.0 23.67 1.59 10.93 51.67 0.12 0.21 0.19 0.07 0.41

High contents were SiO

2

, Al

2

O

3

and Fe

2

O

3

, next was K

2

O, TiO

2

the other oxides were very low, especially MnO (table 1). In average, SiO

2

was the highest in the Thai Binh formation (71.96%), next was in the Hai Hung formation (62.06%) and was the lowest in the Vinh Phuc formation (54.1% - table 3). Al

2

O

3

was from 6.31% to 30.42%. This constituent in average was the highest in the Vinh Phuc formation (18.12%) and the lowest in the Thai Binh formation (10.20%). The average of Fe

2

O

3

was highest in Vinh Phuc formation (10.46%) relating to the laterization; the lowest in gray-green clay of the Hai Hung formation (6.45%) and reached average in the Thai Binh formation (7.21%).

K

2

O in the Hai Hung formation was surpassed the other formations because of relating to the potassium absorption of organic materials. The collected samples of the Hai Hung formation had K

2

O from 1.91 to 3.32%. in average 2.87% (table 3). whereas in the Vinh Phuc formation.

K

2

O was from only 0.34 to 1.66%. and within the Thai Binh formation. the average content of K

2

O was just 2%. The other alkali and alkaline earth elements were very low but they were close correlated close each other with a linear correlation coefficient higher than 0.8 (table 4).

TiO

2

that was also importance in the Quaternary sediments varied from 0.62 to 4.02% (table 1). It was the highest in the Vinh Phuc formation with an average value of 1.94%; next was in the Hai Hung formation (0.86%). and the lowest in the Thai Binh formation (0.67%). TiO

2

was correlated positively to Al

2

O

3

and then Fe

2

O

3

(table 4)

1-10 Trace elements

The trace elements that were researched consisted of the chalcophile elements such as Cu. Zn.

Sb. As. Pb. Cd and the siderophile elements such as V. Cr. Ni. Their components are displayed in table 2. The following describes in detail their behaviors that are influential hardly in soil and water.

Arsenic

The arsenic content of drill hole QO.01 was varied from 10.1mg/kg in mottled clay layer of Vinh Phuc formation to 41.5 mg/kg in greenest gray mixed-clay layer of Hai Hung formation.

According to Smedley P.L. Kinniburgh D.G. (2002). the average As level of the friable sediments was ranged from 3 to 10 mg/kg. and then As content of research area was so much higher. If compared to the average As level of the earth’s crust. which was 1.7 mg/kg (Vinogradop. 1962) then it was 8 to 24 times higher. So. this thing show that regional sedimentary could be source to pollute Hanoi underground water.

In the drill hole QO.03. As content was from 5.77 mg/kg at 19.3 m depth in mottled clay of Vinh Phuc formation to 14.8 mg/kg at 4.3 m depth in greenest gray, dark gray clay- mud of Hai Hung formation (tab. 1). In comparison to the clay deposits. the As maximum was 2.2 times higher and 9 times higher than the average level in the earth’s crust. It is possible that the source of arsenic of underground water in Ha Noi area could be from sedimentary layers.

In variation charts. As content decreased with depth (Fig. 1a. 2a)

[2] Table 2. Trace element contents (mg/kg) of Quaternary sediments in Hanoi area

Sampl e

Drill hole

Dept

h (m) Cu Zn Sb As Pb Cd V Cr Ni

NH.07

QO-01 9.2 35.2 102.

0 12.4 18.7 35.2 0.04

8 135 104 56

NH.10

QO-01 11.7 92.8 94.1 6.6 41.5 47.6 <0.0

1 456 339 64

NH.17

QO-01 20.2 62.7 55.8 4.4 13.7 6.1 <0.0

1 122 174 71

NH.21

QO-01 25.7

116.

0

130.

0 62.8 15.3 22.2 <0.0

1 279 248 137

NH.25

QO-01 35.7

112.

0

173.

0 4.8 21.1 25.9 <0.0

1 336 246 125

NH.30

QO-01 44.7 70.8 118.

0 4.0 10.1 16.6 <0.0

1 204 129 95

NH.65

QO-03 3.7 20.1 63.0 7.1 12.2 16.1 0.05

7 78 87 42

NH.66

QO-03 4.3 42.8 124.

0 4.7 14.8 34.1 0.18 167 120 71

NH.69

QO-03 8.3 35.8 152.

0 3.9 13.3 29.4 0.12 139 113 58

NH.71

QO-03 9.8 30.0 139.

0 3.1 10.9 18.2 <0.0

1 110 90 42

NH.72

QO-03 12.3

105.

0 69.3 8.0 13.6 21.5 <0.0

1 84 74 30

NH.75

QO-03 19.2 43.4 63.8 5.6 5.8 23.1 <0.0

1 183 130 38

NH.76

QO-03 20.8 49.6 78.3 11.0 6.5 25.1 <0.0

1 197 129 44

[3] Table 3. The mean of chemical component contents of Quaternaary sediment formations in Hanoi area ⁽*)

Formations Oxides (%)

SiO

2

TiO

2

Al

2

O

3

Fe

2

O

3

MnO MgO CaO Na

2

O K

2

O Thai Binh 71.96 0.67 10.20 7.21 0.10 0.94 0.44 0.73 2.00

Hai Hưng 68.04 0.75 14.23 5.42 0.03 0.95 0.28 0.29 2.27

Vinh Phuc 54.84 2.27 17.82 14.82 0.04 0.42 0.12 0.08 1.10

Ha Nôi 80.78 0.20 9.48 2.28 0.38 0.85 0.50 0.21 1.31

Le Chi 78.59 0.28 9.12 2.85 1.44 0.97 0.65 0.17 1.39

Trace elements (mg/kg)

Cu Zn Sb As Pb Cd V Cr Ni

Thai Binh 20.10 63.00 7.10 12.20 16.10 0.06 78.00 87.00 42.00 Hai Hưng 49.76 117.26 6.42 14.26 27.68 0.12 127.00 100.20 51.40 Vinh Phuc 78.19 101.86 14.17 16.29 23.80 <0.01 253.86 199.29 82.00

Ha Nôi - - - - - - - - -

(*)

The data of Ha Noi and Le Chi formations from [12]

1-10

Le Chi - - - - - - - - -

Copper

In the drill hole QO.01. the lowest of Cu content was 35.2 mg/kg in the top soil layer and the highest was 116 mg/kg at 25.7 m depth in mottled clay of Vinh Phuc formation. In the drill hole QO.03. it was varied from 20 mg/kg at 3.7 m depth in silt sand layer of Thai Binh formation to 105 mg/kg at 22.5 m depth in clay layer of Vinh Phuc formation. Copper component was trended to increase with depth (Fig. 1b. 2b). With the average level in sedimentary of the world [6]. copper content in this area reaches approximately and has clark index from 0.62 to 2.04.

Lead

The lead content in the sedimentary layers in drill hole QO.01 was ranged from 6.13 mg/kg at 20.2 m depth in Vinh Phuc formation to 47.6 mg/kg at 11.7 m depth in Hai Hung formation.

In general. it was very close to the average level of the world. In drill hole QO.03. variation of

lead content was from 16.1 mg/kg at 3.7 m depth in silt-sand sedimentary layer of Thai Binh

formation to 34.1 mg/kg at 4.3 m depth in clay layer of Hai Hung formation. The

concentration coefficient of lead in clay layers is fluctuated from 0.27 to 1.71. and it’s clark

index is from 1 to 2. So. in researched area. lead content is the same as the average level of

the world. Like arsenic. lead tends to decrease with depth. (Fig. 1c. 2c)

As Content (mg/kg)

5 10 15 20 25 30 35 40 45

0 20 40 60

a - As

Depth (m)

Cu Content (mg/kg)

5 10 15 20 25 30 35 40 45

0 50 100 150

b - Cu

Depth (m)

Pb Content (mg/kg)

5 10 15 20 25 30 35 40 45

0 20 40 60

c - Pb

Depth (m)

Zn Content (mg/kg)

5 10 15 20 25 30 35 40 45

0 50 100 150 200

d - Zn

Depth (m)

Sb Content (mg/kg)

5 10 15 20 25 30 35 40 45

0 20 40 60 80

e - Sb

Depth (m)

[4] Figure 1. The variation of trace element contents with depth in drill holes QO.01 (longitude:105⁰38’11,46”;

latitude: 20⁰59’41,03”)

Zinc

The variation of zinc contents trends to differ at the 2 drill holes a little bit. The zinc tends to increase in drill holes QO.01 (fig. 1d) and decrease in drill hole QO.03 (fig. 2d) with the depth. In the drill hole QO.01. Zn content was varied from 55.8 mg/kg at 20.2m depth in sediments of Hai Hung formation to 173 mg/kg in sedimentary layers of Vinh Phuc formation. In drill hole QO.03. it was ranged from 63 mg/kg at 3.7 m depth in sediments of Thai Binh formation to 152 mg/kg at 8.3m depth in sediments of Hai Hung formation. In comparison to the general level of the world. the Zn content in Hanoi friable sediments was reached the average level and its concentration coefficient in clay layers was from 0.7 to 2.16 and its clark index was 0.79 to 1.83.

Antimony

1-10

In drill hole QO.01. the antimony content was ranged from 4.03 mg/kg to 62.8 mg/kg. It was higher 2.4 to 31.4 times than the average level in clay stones and 8.1 to 125.6 times than the average Sb level in the earth’s crust. Unlike other elements. it was difficult to find the Sb content variation (fig. 1c. 2c). In the top and bottom sedimentary layers. the Sb content was very low and about the same but in the middle layer at 25.7 m depth. the Sb content was increased to 62.8 mg/kg. In drill hole QO.03. the Sb content was varied from 3.07 mg/kg at 9.8 m depth in Hai Hung formation to 11 mg/kg at 20.8 m depth in Vinh Phuc formation.

However. in the average level. Sb content in the sediments of Vinh Phuc formation was higher than its of Hai Hung and Thai Binh formation. The concentration coefficient of Sb was reached to 1.54 - 5.5. and the clark index was from 6.14 to 22. Thus. the Sb content in research area was much higher than its common situation in the world.

As Content (mg/kg)

3 5 7 9 11 13 15 17 19

0 5 10 15

a - As

Depth (m)

Cu Content (mg/kg)

3 5 7 9 11 13 15 17 19

0 50 100 150

b - Cu

Depth (m)

Pb Content (mg/kg)

3 5 7 9 11 13 15 17 19

0 20 40

c - Pb

Depth (m)

Zn Content (mg/kg)

3 5 7 9 11 13 15 17 19

0 100 200

d - Zn

Depth (m)

Sb Content (mg/kg)

3 5 7 9 11 13 15 17 19

0 5 10 15

e - Sb

Depth (m)

[5] Figure 2. The variation of trace elements with depth in drill holes QO.03

[6] (longitude:105⁰37’43,16”; latitude: 20⁰59’33,93”).

The siderophile elements

The siderophile elements that was analysed include V. Cr. Ni and Ti. In almost samples. their contents were very low and below the average level in the global sedimentary. Therefore. they had non-significant roles to the researched area environment.

The correlation between the chemical components

Researching the correlation between the chemical components enabled to define sedimentary origin and behavior of the elements.

That are similar for behaviours of As. Pb. Zn and Cu by their distribution in sedimentary layers. They gathered high content at 11.7 m depth in mottled clay layers of Vinh Phuc formation. That suggests that As element could be substitutional element remaining sulfur phases in the sediments. The correlative matrix of the chemical components is given in table 4. The data show that there are close combinations each other of siderophile elements such as Fe. V. Cr. Ni. Cu and their correlative coefficients are higher than 0.55. In the other side. As also has a very close relation to V (r = 0.74). Cr (r = 0.77). Fe

2

O

3

(r = 0.8) and Ni (r = 0.23).

So. in the Quaternary sediments of researched area. there is element assemblage including Fe.

Cu. V. Cr. Ni. As. This element assemblage was determine in the weathering crust upon the mafic volcanic rocks of the Vien Nam formation belong to gold ore zone of Doi Bu (Luong Son – Hoa Binh) by Dang Mai et al (2000) [4]. These data show that the Quaternary sedimentary could be created from weathering mafic rocks of Vien Nam formation. This is source of As that pollutes Hanoi underground water.

[7] Table 4. Correlate coefficients of chemical components

SiO2 TiO2 Al2O3 Fe2O3 MgO CaO Na2O K2O V Cu Cr Ni Zn As Pb SiO2 1,0 -0,7 -0,9 -0,6 -0,1 0,0 0,1 0,0 -0,8 -0,7 -0,8 -0,8 -0,8 -0,6 -0,6

TiO2

- 0,7 * ⁽ )

1,0 0,7 0,5 -0,5 -0,5 -0,5 -0,5 0,8 0,9 0,8 0,8 0,5 0,3 0,2

Al2O3 -0,9 0,7 1,0 0,2 0,1 0,0 -0,1 0,1 0,7 0,6 0,6 0,7 0,7 0,3 0,5

Fe2O3 -0,6 0,5 0,2 1,0 -0,3 -0,2 -0,3 -0,4 0,7 0,7 0,8 0,6 0,4 0,8 0,2

MgO -0,1 -0,5 0,1 -0,3 1,0 0,9 0,8 0,9 -0,3 -0,5 -0,4 -0,2 0,3 -0,1 0,4

CaO 0,0 -0,5 0,0 -0,2 0,9 1,0 0,9 0,8 -0,3 -0,5 -0,4 -0,3 0,1 0,0 0,3

Na2O 0,1 -0,5 -0,1 -0,3 0,8 0,9 1,0 0,8 -0,4 -0,5 -0,4 -0,3 0,0 -0,1 0,2

K2O 0,0 -0,5 0,1 -0,4 0,9 0,8 0,8 1,0 -0,4 -0,6 -0,6 -0,2 0,3 -0,2 0,4

V -0,8 0,8 0,7 0,7 -0,3 -0,3 -0,4 -0,4 1,0 0,8 0,9 0,5 0,5 0,7 0,6

(*)r: Significant corelation

1-10

Cu -0,7 0,9 0,6 0,7 -0,5 -0,5 -0,5 -0,6 0,8 1,0 0,9 0,9 0,6 0,5 0,1

Cr -0,8 0,8 0,6 0,8 -0,4 -0,4 -0,4 -0,6 0,9 0,9 1,0 0,6 0,4 0,8 0,4

Ni -0,8 0,8 0,7 0,6 -0,2 -0,3 -0,3 -0,2 0,5 0,9 0,6 1,0 0,8 0,2 0,0

Zn -0,8 0,5 0,7 0,4 0,3 0,1 0,0 0,3 0,5 0,6 0,4 0,8 1,0 0,2 0,3

As -0,6 0,3 0,3 0,8 -0,1 0,0 -0,1 -0,2 0,7 0,5 0,8 0,2 0,2 1,0 0,7

Pb -0,6 0,2 0,5 0,2 0,4 0,3 0,2 0,4 0,6 0,1 0,4 0,0 0,3 0,7 1,0

5. Conclusions

In Hanoi Quaternary sediments. components that include SiO

2

. Al

2

O

3

. Fe

2

O

3

were high. then lower were K

2

O. TiO

2

and other

oxides were negligible. The sedimentary of Vinh Phuc formation was characterized by high Fe2O3 that was a result of laterization. whereas in Hai Hung formation. K2O was high because of potassium absorption by organic materials. In researched sediments. there are close relationship between the alkaline and earth alkaline elements; TiO2 is positively correlative with Al2O3 and Fe2O3.

In the Hanoi Quaternary sediments. the arsenic content that pollutes underground water was much higher than average level of the earth’s crust. Like arsenic. antimony was also high concentrated. its clark index was higher than 20. The behaviors of As. Cu. Pb. Zn were same.

Their contents were high in the upper sediments of Vinh Phuc formation and low layer of Hai Hung formation where organic material remainders gather. Those events suggest that. arsenic which is dangerous polluting Hanoi underground water could be in sulfide phases and absorption forms of organic substances of Hai Hung formation.

The close relationship between Fe. V. Cr. Ni. Cu. As show that mafic rocks in Vien Nam formation were a source to have a part in forming the Quaternary sediments in Hanoi and to rich As there. However. there are more detailed researches on sedimentology and mineralogy.

Acknowledgements

This current research was supported by Vietnam National University. Hanoi in project QGTĐ.10.03. We deeply appreciate the heading board of the Project VINOGEO allow to collect the hole drill samples and Geochemistry and Mineralogy Institute. University of Freiburg (Germany) help to analyse chemical compositions by XRF and AAS.

References

Berg.M., Pham Thi Kim Trang, Caroline Stengel, Johanna Buschmann, Pham Hung Viet, Nguyen Van Dan, Walter Giger, Doris Stüben. Hydrological and sedimentary controls leading to arsenic contamination of groundwater in the Hanoi area. Vietnam: The impact of iron- arsenic ratios. peat. river bank deposits. and excessive groundwater abstraction. Chemical Geology 249 (2008) 91-112.

Bui Huu Viet, Mai Trong Tu, Pham Hung Thanh, Nguyen Van Niem, Do Duc Nguyen, Pham

Thi Nhung Ly, Doan Thi Ngoc Huyen, Nguyen Van Luyen. Reports on the pollution status