Detail Extended Abstract

Evaluation of metal pollution in surface water at some mines mining copper and gold ore in Lao Cai provine by HPI index

MeetingVIWC2026
TopicOS3: Water Environment and Mining
AuthorCuc Thi Nguyen
OrganizationHanoi University of Mining and Geology; Post graduate of Faculty of Environmental Sciences, VNU University of Science
ID2022.1670559282

Content

  1. Introduction
Lao Cai province has relatively developed mining activities such as copper, zinc, gold, and iron apatite ore mining concentrated mainly in the districts of Bat Xat, Bao Thang, Van Ban and Lao Cai city. Besides economic benefits, mining activities, especially copper and gold ores, have a significant impact on surface water environment. In particular, the impact of heavy metal dispersion from ore bodies, landfills, chemicals used in mining and processing is degrading the surface water system around the mines. Some studies on environmental quality assessment in mining areas in Lao Cai province such as Cuc Nguyen Thi et al, 2020. The above studies have shown that surface water environment near the mining site, especially rivers and streams, where is the direct receiving source that is polluted by COD components BOD5, NO2-, NO3-… Most of the above studies focused mainly on assessing water quality by WQI index, using multivariate statistical calculations (MCA) or comparing with allowable standard. Level of pollution heavy metals in surface water are mainly evaluated individually by each index compared with the permitted standards. However, this does not give comprehensive assessment of the effect of metals composition on surface water quality. Therefore, having a unique value is the basis for assessing the impact of heavy metals on surface water quality such as HPI (Heavy metal pollution index, HEI (Heavy metal evaluation index) is very important. In this study, the author used HPI index to assess seasonal heavy metal pollution in surface water copper and gold ore mining areas in Lao Cai province. Specifically, the author uses the analysis results of suface water at copper Sin Quyen and gold Minh Luong mines in Lào Cai provine in 2018 to assess heavy metal pollution in surface water in here.
  1. Material and Methods
2.1. Study area      Sin Quyen copper mine in Bat Xat district, Lao Cai province has been exploited since 2006. The recovered products after processing are Cu and Fe ores. Exploited and processing wastewater after treatment is brought to receiving sources such as Hong River, Ngoi Phat Stream (Centre for Environment and Natural Resources Monitoring of Lao Cai province). Minh Luong gold mine in Van Ban district, Lao Cai province has been exploited since 2011 where Nam Xay stream and Chan stream flow through and is also the receiving source of wastewater from the mine. These are rivers and streams used by local people for living and irrigation purposes. Therefore, the assessment of surface water quality, especially heavy metal contamination is necessary. This paper uses the analysis of surface water samples in rivers and streams flowing through the two mines in the rainy season (6/2018) and the dry season in 2018 (12/2018) shows in table 1. The parameters used to evaluate heavy metal pollution in surface water include Cu, Pb, Zn, As, Fe, Cd. 2.2. Methods HPI index developed by Mohan et al in 1996. HPI index is considered to be an effective method to evaluate the aggregate effect of heavy metals on water quality. In addition, the HPI index can be calculated for individual metals, thereby showing the effects of the water quality in different degrees (Sheykhi and Moore, 2012). Recently, there are many studies using HPI index to evaluate the effect of heavy metals on surface and groundwater quality (Sheykhi and Moore, 2012, Bably Prasad, 2020) had high efficiency. Table 1. Details of the locations for surface water sampling at copper Sin Quyen and Minh Luong gold mines
S.no Code Sampling location Location details
Latitude Longtitude
1 SP1 Hong river water in front of the prossesing copper factory 2510208 397976
2 SP2 Hong river water behind the prossesing copper factory (300m downstream) 2502559 404004
3 SP3 Ngoi phat spring water at the foot of Ngoi Phat bridge 2502625 403857
4 SP4 Ngoi Phat spring water at the upstream of 500 underground 2502373 403720
5 SP5 Ngoi Phat stream at the downstream of 300m underground 2502028 403619
6 SP6 Nam Xay spring water 2434369 429180
7 SP7 Chan spring water in Minh Luong commune 2434737 428090
8 SP8 Chan spring water in Hoa Mac commune 2443491 442427
Source: Centre for Environment and Natural Resources Monitoring of Lao Cai province, 2018 The HPI is calculated with the following equation 1 (Mohan SV, 1996). For this study, the concentration limits (the highest permissive value for drinking water (Si) and maximum desirable value (Ii) for each parameter) were taken from the World Health Organization drinking water specifications (WHO 2006). The highest permissive value for drinking water (Si) refers to the maximum allowable concentration in drinking water in the absence of any alternative water source. The desirable maximum value (Ii) indicates the standard limits for the same parameters in drinking water. The HPI values of the groundwater water samples were computed as per the following equation, which was provided by Mohan et al (1996).   HPI =   (1) Where: Qi is the Sub index of the ith parameter Wi is the unit weight of the parameter and n is the number of parameters considered. The sub index (Qi) of the ith parameter is calculated by the Eq. 2 (2) Where: Mi is the monitored value of heavy metal of the ith parameter, Ii is the ideal value (maximum desirable value for drinking water) of the ith parameter, and Si is the standard value (highest permissive value for drinking water) of the ith parameter. The sign (-) indicates the numerical difference of the two values, ignoring the algebraic sign. Currenntly there are many scales to classify HPI values (Sobhanardakania et al. 2016; Prasad and Bose (2001); Edet and Offiong (2002). Specifically, Sobhanardakania et al 2016 divided HPI values in to 3 levels (Low heavy metal pollution: HPI <100; Heavy metal pollution on the threshold risk HPI = 100 and  High heavy metal pollution HPI  > 100). In this study, the author used  the classification scale of Edet and Offiong, 2002.
Pollution status HPI
Low < 25
Medium 25 - 50
High > 50
  1. Results and discussion
The summary statistics of metal concentration for dry and rainy seasons at the study area is presented in Table 2, 3. Statistical was calculated by SPSS. Table 2. The concentration of metals in surface water at copper Sin Quyen  and gold Minh Luong, Lao Cai in rainy season
STT Code Concentration of metals (mg/l
Cd Pb Cu Fe As
1 SP1 0,005 0,006 0,025 0,092 0,008
2 SP2 0,006 0,005 0,016 0,085 0,007
3 SP3 0,008 0,006 0,028 0,068 0,007
4 SP4 0,001 0,0012 0,06 0,64 0,002
5 SP5 0,001 0,008 0,05 0,47 0,006
6 SP6 0,003 0,001 0,029 0,856 0,006
7 SP7 0,002 0,001 0,009 0,34 0,002
8 SP8 0,004 0,001 0,024 0,087 0,002
Mean 0,0038 0,004 0,030 0,330 0,005
Min 0,0013 0,001 0,009 0,068 0,002
Max 0,0080 0,0080 0,0600 0,8560 0,0080
Std 0,0024 0,0024 0,017 0,302 0,0026
WHO 2006 0,003 0,010 2,0 - 0,010
Table 3. The concentration of metals in surface water at copper Sin Quyen  and gold Minh Luong, Lao Cai in dry season
STT Code Concentration of metals (mg/l)
Cd Pb Cu Fe As
1 SP1 0,002 0,003 0,048 0,08 0,001
2 SP2 0,004 0,002 0,051 0,072 0,006
3 SP3 0,003 0,005 0,027 0,059 0,007
4 SP4 0,002 0,001 0,05 0,54 0,006
5 SP5 0,002 0,001 0,08 0,64 0,002
6 SP6 0,001 0,0009 0,008 0,659 0,005
7 SP7 0,004 0,0009 0,012 0,732 0,001
8 SP8 0,002 0,0009 0,006 0,701 0,001
Mean 0,0024 0,002 0,035 0,435 0,004
Min 0,0010 0,001 0,006 0,059 0,001
Max 0,0040 0,0050 0,0800 0,7320 0,0070
Std 0,001 0,0014 0,0262 0,307 0,002
WHO 2006 0,003 0,010 2,0 - 0,010
From the statistical calculation results, the average contents of Cd, Pb, Cu, Fe, As were  respectively; 0.004; 0.030; 0.330; 0.005 mg /l in rainy and dry seasons is 0.0024; 0.002; 0.035; 0.435; 0.004 mg /l. Most of the metals in the water are below the permitted threshold of WHO (2006), especially the Cd content almost exceeds the permissible standard according to the standards for drinking water, the Fe content is suddenly high. In SP5, SP6 and SP7 these are the locations near the discharge site of ore mining. We can also see that the higher concentrations of Cu and Fe concentrated at the sampling location on Ngoi Phat stream, Nam Xay stream and Chan stream near the ore-mining area. In general, the average concentration of metals in the surface water system near copper and gold mining areas in Lao Cai in the rainy season is usually higher than that in the dry season. This shows that the cause of heavy metal pollution is not only from ore mining and processing activities but also by dispersion from surrounding soil and rock and other sources. If cause of only mining resource, the concentrate of heavy metal in the rainy season will is lower than that in the dry season beacause in the rainy, level of water on the rivers and streams is higher that in the dry season. This means that the concentrate heavy metal is diluted lead to lower. Although the water level on rivers and streams increases in the rainy season, but due to rain in mountainous areas, the terrain is steep, soil, dust, clay and other components increase due to leaching and erosion. The process of metal release into water leads to higher metal content in the water in rainy season than in dry season. The correlation matrix created for the metals are presented in Table 4. Table 4. Correlation matrix of the metals
  Cd Pb Cu Fe As
Cd 1
Pb 0,44 1
Cu -0,29 0,07 1
Fe -0,57 -0,53 0,03 1
As 0,47 0,65 -0,03 -0,37 1
Table 4 shows that the metals in surface water are related by correlation value (R). In which, the most positive correlation is the correlation between As and Pb (R = 0.65), between As and Cd (R = 0.47). Inverse correlation was shown between Fe and Cd (R = -0.57) between Fe and Pb (R = -0.53). From this correlation it can be seen that the metal groups As, Cd and Pb can be the same source of decomposition. Based on the metal concentrations in the water in the rainy season (June 2018) and the rainy season (December 2018) and the WHO limit values ​​(2006), the HPI value is calculated for Hong river and streams Ngoi Phat, Nam Xay and Chan. The parameters considered are Cd, Pb, Cu, Fe and As. HPI is determined by the formula ... Where, Mi  is the mean of the parameters in each river or stream. Si và Ii were taken from the World Health Organization drinking water specifications (WHO 2006). The highest permissive value for drinking water (Si) refers to the maximum allowable concentration in drinking water in the absence of any alternative water source. The HPI values of the surface water in the study area was calculated and classified follow classification scale of Edet and Offiong, 2002. The results shows in tables 5 and 6. Table 5. HPI values of the surface water at mining copper and gold ore areas in Lao Cai province in the rainy
River/Spring HPI Pollution status
Hong 41,32 Medium
Ngoi Phat 28,75 Medium
Nam Xay 23,49 Low
Minh Luong 24,41 Low
Table 6. HPI values of the surface water at mining copper and gold ore areas in Lao Cai province in the dry
River/Spring HPI Pollution status
Hong 24,22 Low
Ngoi Phat 17,58 Low
Nam Xay 9,53 Low
Minh Luong 25,13 Medium
From the tables 5 and 6 shows that surface  water in Nam Xay stream has the smallest HPI value of 9.53 in the dry season and the highest is at the Hong River location in the rainy season is 41.32. In general, the level of heavy metal pollution in rivers is mostly low, and some locations are moderate in the rainy season. The level of heavy metal pollution in the dry season tends to be lower than in the rainy season, which is consistent with the above statistical results. The calculation also showed that components Cd and As are the cause of the high HPI value in the study area. Although the water in rivers and streams in the study area is mainly for irrigation purposes, this will be a water source for domestic use when there is no alternative water source. Therefore, the HPI index is an important data to assess whether the water quality is suitable for domestic purposes or not. The HPI value in the water in most locations is from low to medium, but research results also show that the metal concentration in the water is not only affected by the mineral extraction process, but also has an impact. by other sources such as the process of releasing metals from rocky soil where flows pass and dust, clay ... in the surrounding environment. However, However, there are certain limitations to these methodologies. The HPI needs an ideal value (Ii) or a required value which is not provided by any agency for the metals. Moreover, the metals with lowest standards have the highest influence on the HPI as the weightage (Wi) is the inverse of the standard values of the (Si).
  1. Conclusion
The assessment results of heavy metal pollution in surface water in Hong River and Ngoi Phat, Nam Xay, Chan streams by HPI index showed that it is low to medium. The lowest found HPI value was 9.53 in the dry season in Nam Xay stream and highest at the Hong river location in the rainy season at 41.32. The statistical results and HPI index both show that the average concentration of metal in the water is higher in the rainy season than in the dry season, and the concentration variation level is also greater. Research results also show that the metal concentration in water is not only affected by mineral extraction, but also by other sources such as the release of metals from rocky soil and dust. , clay, clay ... in the surrounding environment. Thus, it can be seen that HPI is a useful method to assess whether water quality is affected by heavy metals or not. However, the HPI calculation method is also limited because for some metals we have difficulty determining the maximum permissible value for drinking water when there is no alternative source.
  1. Reference
Bably Prasad, Abhay Kumar Soni, Anusha Vishwakarma, Ratnesh Trivedi, Krishna Kant Kumar Singh, 2020. Evaluation of water quality near the Malanjhkhand copper mines, India, by use of multivariate analysis and a metal pollution index. Environmental Earth Sciences (2020) 79:259. doi.org/10.1007/s12665-020-09002-6. Centre for Environment and Natural Resources Monitoring of Lao Cai province, 2018. Annual emvironmental moritering reports in copper Sin Quyen and gold Minh Luong mines, Lao Cai. Cuc Thi Nguyen, Hoa Mai Thi Phan, Phuong Nguyen, Phi Quoc, NguyenHoa Anh Nguyen, Le Anh Hoang, 2020. Temporal-spatial variation of surface water affected by apatite mining activity in Lao Cai, Viet Nam. Journal of mining and earth sciences, vol 61, Issue 2 (2020)1-10. Edet AE, Offiong OE, 2002. Evaluation of water quality pollution indices for heavy metal contamination monitoring. A study case from Akpabuyo-Odukpani area, Lower Cross River Basin (southeastern Nigeria). GeoJournal 57:295–304. Mohan SV, Nithila P, Reddy SJ, 1996. Estimation of heavy metal in drinking water and development of heavy metal pollution index. J Environ Sci Health A 31(2):283–289. Prasad B, Bose JM, 2001. Evaluation of heavy metal pollution index for surface and spring water near a limestone mining area of the lower Himalayas. Environ Geol 41:183–188. Sheykhi V, Moore F (2012) Geochemical characterization of Kor River water quality, Fars Province, Southwest Iran. Water Qual Expo Health 4:25–38. Sobhanardakania S, Yarib AR, Taghavic L, Tayebid L, 2016. Water quality pollution indices to assess the heavy metal  contamination, case study: groundwater resources of Asadabad Plain in 2012. Arch Hyg Sci 5(4):221–228. WHO, 2006. Guidelines for drinking-water quality, 3rd edn. World Health Organization, Geneva.

Evaluation, surface water, Lao Cai