hydrochemical assessment of groundwater quality near
HYDROCHEMICAL ASSESSMENT OF GROUNDWATER QUALITY NEAR REGINA MUNICIPAL LANDFILL C. PAN, K.T.W. NG, AND A. RICHTER Environmental Systems Engineering, University of Regina, Saskatchewan, Canada
SUMMARY: Condie aquifer provides water for drinking and irrigation purposes for some neighbouring communities near Regina, and impacts to groundwater quality at Condie have been documented recently. Condie aquifer is susceptible to contaminants originating from the City’s landfill and the nearby industrial area due to their close proximity. Groundwater data from 27 wells were used in this study (i) to assess of the suitability of water for drinking and agricultural purposes, and (ii) to investigate the possible sources of contamination using various chemical indices and tools. Significant variations in groundwater chemical compositions were found with repsect to time and location. Generally, the order of abundance of cation concentrations was Ca+>Mg+>Na+>K+, whereas for anion it was SO42->HCO3->Cl-. Analysis of heavy metals indicated that three monitoring wells have higher arsenic concentration than the maximum allowable concentration in Canadian standards, and eight monitoring wells exceeded the maximum concentration for Uranium. Total dissolved solids and total hardness were 3,200 mg/L and 2,000 mg/L, respectively. Dissolved salts were likely derived from evaporation and precipitation processes. It is found that the groundwater from Condie is generally not suitable for drinking and agricultural purposes without further processing.
1. INTRODUCTION Groundwater is the major drinking water source in Canada and many places around the world. Given the large scale of industrial activities and emissions, aquifers near cities or hightly populated areas are especially vulnerable to contamination (Gu et al., 2015). Groundwater standards and testing methods are continuously developed by organizations such as The World Health Organization, Health Canada and the United States Environmental Protection Agency for assessment of water quality with repect to different purposes. Groundwater quality parameters and indices on the suitability of groundwater for drinking and agricultural purposes have been proposed and studied by different researchers. Recently, Nagaraju et al. (2014) studied the salinity hazard of groundwater as irrigation water in an Indian city and successfully assessed the groundwater using parameters such as absolute amount of ions, pH, electrical conductivity (EC), total dissolved solids (TDS), potential salinity (PS) and sodium adsorption ratio (SAR). Nagaraju et al. (2014) also classified water samples based on permeability index (PI), which can be employed as an indicator of the suitability of water for irrigation use, with Class I and II being suitable and Class III being unsuitable.
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Similar parameters and indices were used by Gu et al. (2015) to assess the groundwater quality of Liujiang basin in China. SAR, TDS, pH and total hardness were used to evaluate the water quality for irrigation purposes. Ionic concentration and constituents of groundwater were used to identify the possible sources of the contamination. Chloro-alkaline indices (CAI-I and CAI-II) were used in Gu et al. (2015) to evaluate the ion exchange status. In some studies, cluster analysis (CA) was conducted to determine the groundwater chemical types using the dominant chemicals presented within the study area (Gu et al., 2015; Hassen et al., 2016). The objectives of the present study were (i) to assess of the suitability of the water for drinking and agricultural purposes using the samples’ hydrochemical characteristics, and (ii) to identify the possible sources of contamination using chemical indices and cluster analysis techniques.
2. BACKGROUND INFORMATION 2.1 Canadian solid waste management and landfill disposal Canada has one of the highest per capita waste generation rates in the world (Bruce et al. 2016; Wang et al. 2016; Richter et al. 2017). In 2014, 25 million tonnes of waste were disposed in Canada, about 40% (9.7 million tonnes) of them originated from residential sources. The remaining 60% were from non-residential sources, including construction, renovation and demolition wastes, and industrial, commercial and institutional wastes. In Canada, land disposal is the most common waste treatment method, and Canadians send majority of their wastes to landfills (Environment and Climate Change Canada, 2017). Regina is the capital city of Saskatchewan, located at a latitude of 50˚26’ and a longitude of 104˚37’, with a cold semi-arid climate. The city covers a land area of 118.4 km2 with a total population of 247,000. According to Statistics Canada, the population growth from 2015 to 2016 was 26.0 per thousand in Regina, the second highest in the province (Statistics Canada, 2016). High population growth and limited landfill operating budget make waste disposal in Regina challenging. The per capita waste disposal rate in the province was 839 kg/capita in 2015, the second highest in Canada (Statistics Canada, 2016). Health and environmental issues associated with the use of landfill technlogy are of great concern to residents. Leachate is a common groundwater contaminant and it is therefore important to monitor and assess the impact of landfilling on the environment. 2.2 Regina landfill site and groundwater monitoring program The Fleet Street Solid Waste Disposal & Recovery Facility (Regina Landfill) is located in the northeast part of the city. The landfill is administered by the City of Regina as a municipal solid waste disposal site. The facility has operated since 1961 and accepts a variety of materials and wastes, including clean asphalt, concrete, standard waste, shingles, fill dirt and other materials (City of Regina, 2017). A provincial correction center is located east of the landfill, and a refinery is located to the west (Ashrafi, 2004). Regina is situated in the sedimentary basin (Roeper, 1990). The majority of the landfill disposal areas were built directly on top of the native materials without an engineered liner. The landfill stratigraphy consists of topsoil (~0.5m), lacustrine clay (0.5-4 m), the Condie Formation (6-20 m), the Battleford and Floral Formations’ till (10-30 m), and Upper Floral Formation Sand and Gravel Unit at depth over 30 meters (Table 1). The groundwater monitoring program is administrated by Saskatchewan Environment and Resource Management (SERM) and is performed by the City of Regina on an annual basis to
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
collect groundwater data from the underneath aquifers. Several aquifers located near Regina area, including the Condie (also known as ‘A’ zone), Regina (also known as ‘B’ zone), Zehner, Richardson, and Northern aquifers. The formations of these aquifers are complicated, and contamination of one aquifer may lead to the pollution of another aquifer. In this study, only the water quality of the Condie aquifer was examined as it is located directly undernealth the Regina landfill. Over the operating life of the landfill, many monitoring wells were installed and demolished. Currently there are 27 monitoring wells tapped into the Condie aquifer, the location of these wells and the corresponding IDs were shown on Figure 1. The broken line represents the total footprint of the100-ha Regina landfill. Table 1: Stratigraphy of Regina landfill site (City of Regina, 2015). Stratigraphy Surficial Stratified Drift Condie Formation Battleford & Floral Formation Upper Floral Formation Sand and Gravel Unit
Apr. Depth (m) 0.5-4 6-10 10-20 10-30 30
Lithology Lacustrine Clay Silt Sand Till (unoxidized clay matrix)
Hydrology Aquitard Aquitard Aquifer
Sand & Gravel
Aquifer (Regina)
Figure 1: Regina landfill and the 27 monitoring wells used in this study.
Aquitard
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3. METHODS 3.1 Groundwater samplings A total of two sampling events were performed by the City in 2015. To minimize cross contamination of samples, all samples were collected directly from bailers following standard procedures. Gloves were worn and electric tape readers were rinsed during each sampling. Most groundwater samples were drawn from the monitoring wells in June, and were analyzed by a company in Alberta for a number of indicator parameters, including conductivity, pH, sodium, chloride, ammonia and TOC, and heavy metals. 3.2 Grouping of results According to the environmental assessment results, the general groundwater flow direction around landfill site area is from northeast to the southwest (City of Regina, 2009; City of Regina, 2015). In order to identify the possible soures of groundwater contamination, samples from the 27 monitoring wells were categorised into 5 groups: § Group 1: Monitoring wells 67, 70, 69, and 78. These wells are located outside of the landfill site boundary. These upgradient wells are located at the north and east sides of the landfill and, therefore, are considered as the “background wells”. § Group 2: Monitoring wells 84, 35, 45, and 118. They are on the east side of the landfill and are within the site boundary. The groundwater in this area is impacted directly by the upper stream waterflow. § Group 3: Monitoring wells 112, 114, 103, and 104. These downgradient wells are located at the south boundary of the landfill site. § Group 4: Monitoring wells 81, 71, 23, 26, 85, 28, 30, and 32. These wells are located along the west boundary of the site. § Group 5: Monitoring wells 87, 86, 65, 64, 42, 43 and 62. These wells are located in the downstream west field and are further away from landfill boundary. 3.3 Parameters and indicators 3.3.1 Salinity and Sodium hazard High sodium concentration leads to sodium and salinity hazard, which is harmful to vegetation and plant growth. Sodium percentage (SP) can be used to indicate the relative sodium concentration, as defined by Wilcox (Wilcox, 1955; Hassen et al., 2016).
where all the parameters are in milliequivalents per litre (meg/L). EC is the capability of groundwater to conduct electricity. Wilcox diagram was used to assess the salinity of water samples on plant growth. Using the diagram, water samples were classified into different group, from excellent to unsuitable (Wilcox, 1955; Nagaraju et al., 2014). SAR is a measurement of the sodium content relative to calcium and magnesium, which is an index widely used for assessing the quality of irrigation water (Hassen et al., 2016; Hillel & Feinerman, 2000; Foster et al., 2000). SAR (Karanth, 1987) is defined as:
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
where all the parameters are in milliequivalents per litre (meg/L). The hazardous effect of sodium can also be assessed by Kelley’s ratio (Kelley, 1940). When Kelley’s ratio is greater than one, it is considered unsuitable for irrigation. Kelley’s ratio is defined as:
where all the parameters are in melliequivalents per litre (meg/L). 3.3.2 TDS, hardness and toxic metals Total dissolved solids and hardness can affect the texture and taste of water and therefore must be considered when assessing the suitability of the groundwater. The results were presented by groups to explore the possible source of the contaminants. Heavy metals such as manganese, arsenic, and uranium are toxic and must be evaluated. 3.3.3 Gibbs’ diagram, dissolved salts and correlation plots Major ion concentrations in Condie aquifer include cations such as Ca2+, Mg2+, and Na+, as well as anions such as P3-SO42-, Cl-, and HCO3-. Plots of TDS with ion ratios (Maiti et al., 2013; Hassen et al., 2016) were prepared to explore the origin of the dissolved salts. Ion correlation plots were used to explain the possible mechanisms behind the dissolution and precipitation processes. 4. RESULTS AND DISCUSSION 4.1 General hydrochemical analysis A long list of parameters were analyzed in the lab. However, some of the concentrations were below detection limits, or low enough to be excluded for this study. and take steps when needed. Table 2 summarized the key parameters and their concentrations from all 27 wells used in this study. The allowable concentrations specified by the Canadian Drinking Water Quality (Health Canada, 2014) and the WHO Standard (2011) were included when applicable. The abundance of major cation concentrations were Ca+>Mg+>Na+>K+ and SO42->HCO3->Clfor anions. The results indicated that most hazardous chemicals and heavy metal concentrations were relatively low, and may not cause serious health issues to residents. However, a considerable amount of samples exceeded the maximum permissible concentrations for arsenic and uranium. Although the mean concentrations are lower than the guildelines, it is recommended to keep monitoring the concentrations of these two heavy metals and take steps when needed. Table 2: Trace metals and general parameters (City of Regina, 2015). Canadian All monitoring wells Drinking WHO Water Standard Quality (2011) Mean Max Min (2014)
STD
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Trace Metals Arsenic Calcium Iron Magnesium Manganese Potassium Sodium Uranium
0.01 no value a 0.3 0.05
no value a 0.1 no value a 200
200 0.02 General Parameters
0.004 336.7 0.3 120.9 1.5 9.7 63.0 0.019
0.025 500 0.78 190 2.60 21 320 0.054
0.0003 120 0.06 32 0.18 5.3 17.0 0.007
Bicarbonate 422.2 700 Chloride 250 63.4 460 Nitrate 50 1.1 8.4 Sulphate 250 1094.1 1800 Total Dissolved Solids 1000 1886.3 3200 Tot. Hardne CaCO3 500 1333.3 2000 pH 6.5-8.5 7.77 8.17 Conductivity (us/cm) 2379 4300 Note: a “No value” for parameters not considered to establish a health-based in drinking water (WHO 2011).
0.005 104.7 0.28 44.4 0.60 2.96 59.8 0.010
290 94.2 1.3 97.0 0.01 2.13 180 430.7 530 713.8 440 437.5 7.43 0.19 860 822.8 guideline value
4.2 Sodium hazard and Irrigation water quality assessments A SAR of 0.4-0.6 was observed for majority of the wells, as shown in Figure 2. However, wells number 26 and 30 were about 4-7 times higher than the average, and both wells were in group 4. Figure 3 shows the mean, maximum and minimum values for each group. SARs from Group 1 not only were the lowest among the groups, but also with a narrower range. This is expected as Group 1 wells were located upgradient from the site, and some of the salts might originate from the landfill. Group 4, on the other hand, showed the highest mean SAR value, as well as larger uncertainties. This finding is consistent with the City’s observations (City of Regina, 2015).
Figure 2: Sodium adsorption ratio for all monitoring wells.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 3: SAR values by groups.
The results above suggest the possibility of sodium accumulation due to the operation of the landfill. However, the overall values were low and the SARs met the criteria of “excellent” class for alkalinity hazard (Richards, 1954). According to Hassen et al., 2016 and Nagaraju et al., 2014, EC values exceeding 2,000 would not be suitable for irrigation. Figure 4 shows that less than half of the well water samples met the criteria.
Figure 4: Suitablilty of the groundwate for irrigation purposes.
4.3 Drinking water quality assessment TDS consists of ions such as calcium, magnesium, sodium, potassium, carbonate, bicarbonate, chloride, sulphate and nitrate, and is commonly used as an indicator for drinking water quality. Health Canada (2014) recommended a TDS concentration below 500 mg/L for drinking water. Water with high TDS concentrations has unpleasant taste and may cause scaling in water pipes and boilers. Figure shows the TDS and pH for all monitoring wells. The mean TDS values for Groups 1 to 5 were 722 mg/L, 1800 mg/L, 977 mg/L, 1475 mg/L, and 1457 mg/L, respectively. It is not clear why group 2 wells had significantly higher TDS than the downgradient wells. More research is needed before a definite conclusions can be made. The background group (Group 1) again showed the lowest TDSs. Since TDSs were consistently larger than 500 mg/L, the groundwater is unsuitable for direct drinking. The pH of the groundwater were typical, about 7.5-8.1. Higher pH may lead to precipitation and lower the TDS.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 5: TDS and pH from all wells.
High hardness (as CaCO3) in water causes unpleasant taste and produces more deposits of precipitate. Hardness above 500 mg/L is considered unacceptable for drinking water. Figure 6 shows that almost all samples were larger than the acceptable value. Similar to the TDS values, Group 2 and 4 have the highest vales among all groups, with mean values of 1,800 and 1,475 mg/L, respectively. Again, hardness values were the lowest (723 mg/L) in upgradient wells.
Figure 6: Hardness in monitoring well groups.
Manganese concentrations also largely exceeded the drinking standard (Table 2). Manganese in groundwater may originate from weathered rocks and minerals and cause unpleasant taste. In addition, arsenic and uranium concentrations were too high in some wells and were not suitable for drinking purposes. 4.4 Ion correlation and exchange Gibbs’ diagrams (Gibbs, 1970) were prepared to identify the possible origins of the major dissolved salts. According to the analysis (Figure 7), the dissolved salts were mostly derived from evaporation and precipitation processes, with minimum rock weathering. This is probably due to the low ion ratios ( 500mg/L). The slope of the bestfit line of Na+ against Cl- (Figure 8a) was 0.9242, closely matched with the 1:1 ratio line, suggesting that salinity from the groundwater was dominated by halite dissolution (Hassen et al., 2016). On the other hand, the best-fit line of Ca2+ and SO42- deviated from the 1:1 ratio line, indicating that gypsum might not be the only source of calcium in the area. The deficit in Ca2+ was clear, as most of the points were below the 1:1 ratio line. The might be due to the carbonate precipitation.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 7: Gibbs' diagrams.
Figure 8: Ion correlation plots. a) Na+ vs. Cl-; b) Ca2+ vs SO42-.
5. CONCLUSIONS Groundwater from Condie were systematically assessed using various chemical indicators for both irrigation and drinking purposes. The sodium percentage and sodium adsorption ratio were generally low, but the groundwater was found unsuitable for irrigation use due to the high electrical conductivity. Several groundwater samples exceeded the maximum permissible concentrations for arsenic and uranium, which can lead to servious health and safety concerns. Total hardness and total dissolved solids were found considerably higher than the standards, indicating the unsuitability for direct drinking. Results from cluster analysis indicated that downgradient wells have higher salinity and TDS than upgradient wells, which are consistent with the City’s findings. It appears that some of the groundwater contaminants may originate from the operation of the Regina landfill. However, further research is needed before definite conclusion can be made. Gibbs’ diagrams suggested that the chemical composition was mainly controlled by evaporation and rock weathering processes. Analysis regarding ion correlations showed high linear relationships between Na+ and Cl- (R2=0.77) as well as Ca2+ and SO42- (R2=0.93). Salinity from groundwater appears to be dominated by halite dissolution, and gypsum is not the only source of calcium in the area.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
This paper highlighted some of the preliminary results from this study. Future study will be focusing on the development of the plumes with respect to time.
AKNOWLEDGEMENTS The research reported in this paper was supported by a grant (RGPIN-385815) from the Natural Sciences and Engineering Research Council of Canada. The authors are grateful for their support. Special acknowledgment goes to the City’s landfill team, who supported the data collection. The views expressed herein are those of the writers and not necessarily those of our research and funding partners.
REFERENCES Ashrafi F. (2004). Evaluation of the Potential Contamination Risk to Groundwater Pose by Municipal Landfill Leachate. Master Thesis, Environmental Systems Engineering, University of Regina, 2004. Bruce, N., Asha, A.Z., Ng, K.T.W. (2016). Analysis of solid waste management systems in Alberta and British Columbia using provincial comparison. Canadian Journal of Civil Engineering, 43 (4), 351-360 City of Regina. (2009). Fleet Street Solid Waste Division and Recovery Facility Expansion Project – Environmental Impact Statement. Regina, Saskatchewan, Canada. City of Regina. (2015). City of Regina Landfill Groundwater Monitoring Report. Regina, Saskatchewan, Canada. City of Regina. (2017). City of Regina Landfill – City of Regina. Retrieved from http://www.regina.ca/residents/waste/garbage-landfill/landfill/. Envrionment and Climate Change Canada. (2017). Municipal Solid Waste and the Environment. Retrived from https://www.ec.gc.ca/gdd-mw/default.asp?lang=En&n=5F6E5596-1. Foster, S., Chilton, J., Moench, M., Cardy, F., & Schiffler, M. (2000). Groundwater in rural development: facing the challenges of supply and resource sustainability. Papers, vol. 55, 264266. Gu H., Chi B., Li H., Jiang J., Qin W. And Wang H. (2015). Assessment of groundwater quality and idenfitifcation of contaminant sources of Liujiang basin in Qinhuangdao, North China. Environ Earth Sci., vol. 73, 6477-6493. Gibbs R. J. (1970). Mechanisms controlling world’s water chemistry. Science Vol. 170:1088– 1090. Hassen I., Hamzaoui-Azaza F. And Bouhlila R. (2016). Application of multivariate statistical analysis and hydrochemical and isotopic investigations for evaluation of groundwater quality and its suitability for drinking and agriculture purposes: case of Oum Ali-Thelepte aquifer, central Tunisia. Envrion Monit Assess., vol. 188, 135. Health Canada. (1979). Guidelines for Canadian Drinking Water Quality: Guideline Technical Document – Hardness. Ottawa, Ontario. Retrieved from https://www.canada.ca/en/healthcanada/services/publications/healthy-living/guidelines-canadian-drinking-water-qualityguideline-technical-document-hardness.html Health Canada. (2014). Guidelines for Canadian Drinking Water Quality – Summary Tabel. Water and Air Quality Bureau, Healthy Environments and CConsumer Safety Branch, Health Canada, Ottawa, Ontario.
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Hillel, D., & Feinerman, E. (2000). Salinity management for sustainable irrigation: Integrating science, environment, and economics. (Environmentally and socially sustainable development. Rural development). Washington, D.C.: World Bank. Karanth, K. (1987). Ground water assessment: development and management. Tata McGrawHill Education. Kelley, W. P. (1940). Permissible composition and concentration of irrigation water. Proceedings of the American Society of Civil Engineers, 607-613. Maiti, S., Erram, V. C., Gupta, G., Tiwari, R. K., Kulkarni, U. D., & Sangpal, R. R. (2013). Assessment of groundwater quality: a fusion of geochemical and geophysical information via bayesian neural networks. Environmental Monitoring & Assessment, 185, 3445-3465. Muricken, D. G. (2006). Groundwater and Contaminant Transport Modeling Through the Aquifers Underlying the City of Regina Landfill: A Case Study. Master Thesis, Environmental Systems Engineering, University of Regina, 2006. Nagaraju, A., Sunil Kumar, K. and Thejaswi A. (2014). Assessment of groundwater quality for irrigation: a case study from Bandalamottu lead mining area, Guntur District, Andhra Pradesh, South India. Appl Water Sci., vol. 4, 385-396. Richards, L. A. (1954). Diagnosis and improvement of saline alkali soils. US Departent of Agriculture, Handbook. Richter, A., Bruce, N., Ng, K.T.W., Chowdhury, A., Vu, H.L. (2017). Comparison between Canadian and Nova Scotia waste management and diversion models – A Canadian case study. Sustainable Cities and Society 30, 139-149. Statistics Canada. (2016). Total waste disposal – Statistics Canada. Retrived from http://www.statcan.gc.ca/tables-tableaux/sum-som/l01/cst01/envir32a-eng.htm Statistics Canada. (2017). Annual Demographic Estimates: Subprovincial Areas, July 1, 2016. Catalogue no. 91-214-X. Ottawa, Ontario. Retrived from http://www.statcan.gc.ca/pub/91-214x/91-214-x2017000-eng.pdf Schoeller H (1967) Qualitative evaluation of groundwater resources. Methods and techniques of groundwater investigation and development. Water research, Series-33: UNESCO, pp 44–52. Şen, Z. (2011). Groundwater quality variation assessment indices. Water Quality, Exposure and Health, vol. 3, 127-133. Wang, Y., Ng, K.T.W., Asha, A.Z. (2016). Non-hazardous waste generation characteristics and recycling practices in Saskatchewan and Manitoba, Canada. Journal of Material Cycles and Waste Management, 18, 715-724. World Health Organization (WHO). (2011). Guidelines for Drinking-water Quality - 4th edition. Geneva, Switzerland. Wilcox, L. (1955). Classification and use of irrigation water, circular 969. Washington, DC, USA.
SUMMARY: Condie aquifer provides water for drinking and irrigation purposes for some neighbouring communities near Regina, and impacts to groundwater quality at Condie have been documented recently. Condie aquifer is susceptible to contaminants originating from the City’s landfill and the nearby industrial area due to their close proximity. Groundwater data from 27 wells were used in this study (i) to assess of the suitability of water for drinking and agricultural purposes, and (ii) to investigate the possible sources of contamination using various chemical indices and tools. Significant variations in groundwater chemical compositions were found with repsect to time and location. Generally, the order of abundance of cation concentrations was Ca+>Mg+>Na+>K+, whereas for anion it was SO42->HCO3->Cl-. Analysis of heavy metals indicated that three monitoring wells have higher arsenic concentration than the maximum allowable concentration in Canadian standards, and eight monitoring wells exceeded the maximum concentration for Uranium. Total dissolved solids and total hardness were 3,200 mg/L and 2,000 mg/L, respectively. Dissolved salts were likely derived from evaporation and precipitation processes. It is found that the groundwater from Condie is generally not suitable for drinking and agricultural purposes without further processing.
1. INTRODUCTION Groundwater is the major drinking water source in Canada and many places around the world. Given the large scale of industrial activities and emissions, aquifers near cities or hightly populated areas are especially vulnerable to contamination (Gu et al., 2015). Groundwater standards and testing methods are continuously developed by organizations such as The World Health Organization, Health Canada and the United States Environmental Protection Agency for assessment of water quality with repect to different purposes. Groundwater quality parameters and indices on the suitability of groundwater for drinking and agricultural purposes have been proposed and studied by different researchers. Recently, Nagaraju et al. (2014) studied the salinity hazard of groundwater as irrigation water in an Indian city and successfully assessed the groundwater using parameters such as absolute amount of ions, pH, electrical conductivity (EC), total dissolved solids (TDS), potential salinity (PS) and sodium adsorption ratio (SAR). Nagaraju et al. (2014) also classified water samples based on permeability index (PI), which can be employed as an indicator of the suitability of water for irrigation use, with Class I and II being suitable and Class III being unsuitable.
Proceedings Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium/ 2 - 6 October 2017 S. Margherita di Pula, Cagliari, Italy / © 2017 by CISA Publisher, Italy
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Similar parameters and indices were used by Gu et al. (2015) to assess the groundwater quality of Liujiang basin in China. SAR, TDS, pH and total hardness were used to evaluate the water quality for irrigation purposes. Ionic concentration and constituents of groundwater were used to identify the possible sources of the contamination. Chloro-alkaline indices (CAI-I and CAI-II) were used in Gu et al. (2015) to evaluate the ion exchange status. In some studies, cluster analysis (CA) was conducted to determine the groundwater chemical types using the dominant chemicals presented within the study area (Gu et al., 2015; Hassen et al., 2016). The objectives of the present study were (i) to assess of the suitability of the water for drinking and agricultural purposes using the samples’ hydrochemical characteristics, and (ii) to identify the possible sources of contamination using chemical indices and cluster analysis techniques.
2. BACKGROUND INFORMATION 2.1 Canadian solid waste management and landfill disposal Canada has one of the highest per capita waste generation rates in the world (Bruce et al. 2016; Wang et al. 2016; Richter et al. 2017). In 2014, 25 million tonnes of waste were disposed in Canada, about 40% (9.7 million tonnes) of them originated from residential sources. The remaining 60% were from non-residential sources, including construction, renovation and demolition wastes, and industrial, commercial and institutional wastes. In Canada, land disposal is the most common waste treatment method, and Canadians send majority of their wastes to landfills (Environment and Climate Change Canada, 2017). Regina is the capital city of Saskatchewan, located at a latitude of 50˚26’ and a longitude of 104˚37’, with a cold semi-arid climate. The city covers a land area of 118.4 km2 with a total population of 247,000. According to Statistics Canada, the population growth from 2015 to 2016 was 26.0 per thousand in Regina, the second highest in the province (Statistics Canada, 2016). High population growth and limited landfill operating budget make waste disposal in Regina challenging. The per capita waste disposal rate in the province was 839 kg/capita in 2015, the second highest in Canada (Statistics Canada, 2016). Health and environmental issues associated with the use of landfill technlogy are of great concern to residents. Leachate is a common groundwater contaminant and it is therefore important to monitor and assess the impact of landfilling on the environment. 2.2 Regina landfill site and groundwater monitoring program The Fleet Street Solid Waste Disposal & Recovery Facility (Regina Landfill) is located in the northeast part of the city. The landfill is administered by the City of Regina as a municipal solid waste disposal site. The facility has operated since 1961 and accepts a variety of materials and wastes, including clean asphalt, concrete, standard waste, shingles, fill dirt and other materials (City of Regina, 2017). A provincial correction center is located east of the landfill, and a refinery is located to the west (Ashrafi, 2004). Regina is situated in the sedimentary basin (Roeper, 1990). The majority of the landfill disposal areas were built directly on top of the native materials without an engineered liner. The landfill stratigraphy consists of topsoil (~0.5m), lacustrine clay (0.5-4 m), the Condie Formation (6-20 m), the Battleford and Floral Formations’ till (10-30 m), and Upper Floral Formation Sand and Gravel Unit at depth over 30 meters (Table 1). The groundwater monitoring program is administrated by Saskatchewan Environment and Resource Management (SERM) and is performed by the City of Regina on an annual basis to
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
collect groundwater data from the underneath aquifers. Several aquifers located near Regina area, including the Condie (also known as ‘A’ zone), Regina (also known as ‘B’ zone), Zehner, Richardson, and Northern aquifers. The formations of these aquifers are complicated, and contamination of one aquifer may lead to the pollution of another aquifer. In this study, only the water quality of the Condie aquifer was examined as it is located directly undernealth the Regina landfill. Over the operating life of the landfill, many monitoring wells were installed and demolished. Currently there are 27 monitoring wells tapped into the Condie aquifer, the location of these wells and the corresponding IDs were shown on Figure 1. The broken line represents the total footprint of the100-ha Regina landfill. Table 1: Stratigraphy of Regina landfill site (City of Regina, 2015). Stratigraphy Surficial Stratified Drift Condie Formation Battleford & Floral Formation Upper Floral Formation Sand and Gravel Unit
Apr. Depth (m) 0.5-4 6-10 10-20 10-30 30
Lithology Lacustrine Clay Silt Sand Till (unoxidized clay matrix)
Hydrology Aquitard Aquitard Aquifer
Sand & Gravel
Aquifer (Regina)
Figure 1: Regina landfill and the 27 monitoring wells used in this study.
Aquitard
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
3. METHODS 3.1 Groundwater samplings A total of two sampling events were performed by the City in 2015. To minimize cross contamination of samples, all samples were collected directly from bailers following standard procedures. Gloves were worn and electric tape readers were rinsed during each sampling. Most groundwater samples were drawn from the monitoring wells in June, and were analyzed by a company in Alberta for a number of indicator parameters, including conductivity, pH, sodium, chloride, ammonia and TOC, and heavy metals. 3.2 Grouping of results According to the environmental assessment results, the general groundwater flow direction around landfill site area is from northeast to the southwest (City of Regina, 2009; City of Regina, 2015). In order to identify the possible soures of groundwater contamination, samples from the 27 monitoring wells were categorised into 5 groups: § Group 1: Monitoring wells 67, 70, 69, and 78. These wells are located outside of the landfill site boundary. These upgradient wells are located at the north and east sides of the landfill and, therefore, are considered as the “background wells”. § Group 2: Monitoring wells 84, 35, 45, and 118. They are on the east side of the landfill and are within the site boundary. The groundwater in this area is impacted directly by the upper stream waterflow. § Group 3: Monitoring wells 112, 114, 103, and 104. These downgradient wells are located at the south boundary of the landfill site. § Group 4: Monitoring wells 81, 71, 23, 26, 85, 28, 30, and 32. These wells are located along the west boundary of the site. § Group 5: Monitoring wells 87, 86, 65, 64, 42, 43 and 62. These wells are located in the downstream west field and are further away from landfill boundary. 3.3 Parameters and indicators 3.3.1 Salinity and Sodium hazard High sodium concentration leads to sodium and salinity hazard, which is harmful to vegetation and plant growth. Sodium percentage (SP) can be used to indicate the relative sodium concentration, as defined by Wilcox (Wilcox, 1955; Hassen et al., 2016).
where all the parameters are in milliequivalents per litre (meg/L). EC is the capability of groundwater to conduct electricity. Wilcox diagram was used to assess the salinity of water samples on plant growth. Using the diagram, water samples were classified into different group, from excellent to unsuitable (Wilcox, 1955; Nagaraju et al., 2014). SAR is a measurement of the sodium content relative to calcium and magnesium, which is an index widely used for assessing the quality of irrigation water (Hassen et al., 2016; Hillel & Feinerman, 2000; Foster et al., 2000). SAR (Karanth, 1987) is defined as:
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
where all the parameters are in milliequivalents per litre (meg/L). The hazardous effect of sodium can also be assessed by Kelley’s ratio (Kelley, 1940). When Kelley’s ratio is greater than one, it is considered unsuitable for irrigation. Kelley’s ratio is defined as:
where all the parameters are in melliequivalents per litre (meg/L). 3.3.2 TDS, hardness and toxic metals Total dissolved solids and hardness can affect the texture and taste of water and therefore must be considered when assessing the suitability of the groundwater. The results were presented by groups to explore the possible source of the contaminants. Heavy metals such as manganese, arsenic, and uranium are toxic and must be evaluated. 3.3.3 Gibbs’ diagram, dissolved salts and correlation plots Major ion concentrations in Condie aquifer include cations such as Ca2+, Mg2+, and Na+, as well as anions such as P3-SO42-, Cl-, and HCO3-. Plots of TDS with ion ratios (Maiti et al., 2013; Hassen et al., 2016) were prepared to explore the origin of the dissolved salts. Ion correlation plots were used to explain the possible mechanisms behind the dissolution and precipitation processes. 4. RESULTS AND DISCUSSION 4.1 General hydrochemical analysis A long list of parameters were analyzed in the lab. However, some of the concentrations were below detection limits, or low enough to be excluded for this study. and take steps when needed. Table 2 summarized the key parameters and their concentrations from all 27 wells used in this study. The allowable concentrations specified by the Canadian Drinking Water Quality (Health Canada, 2014) and the WHO Standard (2011) were included when applicable. The abundance of major cation concentrations were Ca+>Mg+>Na+>K+ and SO42->HCO3->Clfor anions. The results indicated that most hazardous chemicals and heavy metal concentrations were relatively low, and may not cause serious health issues to residents. However, a considerable amount of samples exceeded the maximum permissible concentrations for arsenic and uranium. Although the mean concentrations are lower than the guildelines, it is recommended to keep monitoring the concentrations of these two heavy metals and take steps when needed. Table 2: Trace metals and general parameters (City of Regina, 2015). Canadian All monitoring wells Drinking WHO Water Standard Quality (2011) Mean Max Min (2014)
STD
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Trace Metals Arsenic Calcium Iron Magnesium Manganese Potassium Sodium Uranium
0.01 no value a 0.3 0.05
no value a 0.1 no value a 200
200 0.02 General Parameters
0.004 336.7 0.3 120.9 1.5 9.7 63.0 0.019
0.025 500 0.78 190 2.60 21 320 0.054
0.0003 120 0.06 32 0.18 5.3 17.0 0.007
Bicarbonate 422.2 700 Chloride 250 63.4 460 Nitrate 50 1.1 8.4 Sulphate 250 1094.1 1800 Total Dissolved Solids 1000 1886.3 3200 Tot. Hardne CaCO3 500 1333.3 2000 pH 6.5-8.5 7.77 8.17 Conductivity (us/cm) 2379 4300 Note: a “No value” for parameters not considered to establish a health-based in drinking water (WHO 2011).
0.005 104.7 0.28 44.4 0.60 2.96 59.8 0.010
290 94.2 1.3 97.0 0.01 2.13 180 430.7 530 713.8 440 437.5 7.43 0.19 860 822.8 guideline value
4.2 Sodium hazard and Irrigation water quality assessments A SAR of 0.4-0.6 was observed for majority of the wells, as shown in Figure 2. However, wells number 26 and 30 were about 4-7 times higher than the average, and both wells were in group 4. Figure 3 shows the mean, maximum and minimum values for each group. SARs from Group 1 not only were the lowest among the groups, but also with a narrower range. This is expected as Group 1 wells were located upgradient from the site, and some of the salts might originate from the landfill. Group 4, on the other hand, showed the highest mean SAR value, as well as larger uncertainties. This finding is consistent with the City’s observations (City of Regina, 2015).
Figure 2: Sodium adsorption ratio for all monitoring wells.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 3: SAR values by groups.
The results above suggest the possibility of sodium accumulation due to the operation of the landfill. However, the overall values were low and the SARs met the criteria of “excellent” class for alkalinity hazard (Richards, 1954). According to Hassen et al., 2016 and Nagaraju et al., 2014, EC values exceeding 2,000 would not be suitable for irrigation. Figure 4 shows that less than half of the well water samples met the criteria.
Figure 4: Suitablilty of the groundwate for irrigation purposes.
4.3 Drinking water quality assessment TDS consists of ions such as calcium, magnesium, sodium, potassium, carbonate, bicarbonate, chloride, sulphate and nitrate, and is commonly used as an indicator for drinking water quality. Health Canada (2014) recommended a TDS concentration below 500 mg/L for drinking water. Water with high TDS concentrations has unpleasant taste and may cause scaling in water pipes and boilers. Figure shows the TDS and pH for all monitoring wells. The mean TDS values for Groups 1 to 5 were 722 mg/L, 1800 mg/L, 977 mg/L, 1475 mg/L, and 1457 mg/L, respectively. It is not clear why group 2 wells had significantly higher TDS than the downgradient wells. More research is needed before a definite conclusions can be made. The background group (Group 1) again showed the lowest TDSs. Since TDSs were consistently larger than 500 mg/L, the groundwater is unsuitable for direct drinking. The pH of the groundwater were typical, about 7.5-8.1. Higher pH may lead to precipitation and lower the TDS.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 5: TDS and pH from all wells.
High hardness (as CaCO3) in water causes unpleasant taste and produces more deposits of precipitate. Hardness above 500 mg/L is considered unacceptable for drinking water. Figure 6 shows that almost all samples were larger than the acceptable value. Similar to the TDS values, Group 2 and 4 have the highest vales among all groups, with mean values of 1,800 and 1,475 mg/L, respectively. Again, hardness values were the lowest (723 mg/L) in upgradient wells.
Figure 6: Hardness in monitoring well groups.
Manganese concentrations also largely exceeded the drinking standard (Table 2). Manganese in groundwater may originate from weathered rocks and minerals and cause unpleasant taste. In addition, arsenic and uranium concentrations were too high in some wells and were not suitable for drinking purposes. 4.4 Ion correlation and exchange Gibbs’ diagrams (Gibbs, 1970) were prepared to identify the possible origins of the major dissolved salts. According to the analysis (Figure 7), the dissolved salts were mostly derived from evaporation and precipitation processes, with minimum rock weathering. This is probably due to the low ion ratios ( 500mg/L). The slope of the bestfit line of Na+ against Cl- (Figure 8a) was 0.9242, closely matched with the 1:1 ratio line, suggesting that salinity from the groundwater was dominated by halite dissolution (Hassen et al., 2016). On the other hand, the best-fit line of Ca2+ and SO42- deviated from the 1:1 ratio line, indicating that gypsum might not be the only source of calcium in the area. The deficit in Ca2+ was clear, as most of the points were below the 1:1 ratio line. The might be due to the carbonate precipitation.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
Figure 7: Gibbs' diagrams.
Figure 8: Ion correlation plots. a) Na+ vs. Cl-; b) Ca2+ vs SO42-.
5. CONCLUSIONS Groundwater from Condie were systematically assessed using various chemical indicators for both irrigation and drinking purposes. The sodium percentage and sodium adsorption ratio were generally low, but the groundwater was found unsuitable for irrigation use due to the high electrical conductivity. Several groundwater samples exceeded the maximum permissible concentrations for arsenic and uranium, which can lead to servious health and safety concerns. Total hardness and total dissolved solids were found considerably higher than the standards, indicating the unsuitability for direct drinking. Results from cluster analysis indicated that downgradient wells have higher salinity and TDS than upgradient wells, which are consistent with the City’s findings. It appears that some of the groundwater contaminants may originate from the operation of the Regina landfill. However, further research is needed before definite conclusion can be made. Gibbs’ diagrams suggested that the chemical composition was mainly controlled by evaporation and rock weathering processes. Analysis regarding ion correlations showed high linear relationships between Na+ and Cl- (R2=0.77) as well as Ca2+ and SO42- (R2=0.93). Salinity from groundwater appears to be dominated by halite dissolution, and gypsum is not the only source of calcium in the area.
Sardinia 2017 / Sixteenth International Waste Management and Landfill Symposium / 2 - 6 October 2017
This paper highlighted some of the preliminary results from this study. Future study will be focusing on the development of the plumes with respect to time.
AKNOWLEDGEMENTS The research reported in this paper was supported by a grant (RGPIN-385815) from the Natural Sciences and Engineering Research Council of Canada. The authors are grateful for their support. Special acknowledgment goes to the City’s landfill team, who supported the data collection. The views expressed herein are those of the writers and not necessarily those of our research and funding partners.
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