هدف مطالعۀ حاضر، ارزیابی کیفیت آب و رسوبات رودخانۀ بادآور در شهرستان نورآباد (استان لرستان) است؛ به این منظور، 19 نمونه آب و 5 نمونه رسوب سطحی از رودخانه برداشت و شاخصهای فیزیکوشیمیایی نمونههای آب (شامل pH، هدایت الکتریکی، غلظت یونهای اصلی، آنالیز میکروبی و غلظت عناصر بالقوه سمی) و رسوب (شامل pH، مادۀ آلی، درصد کربنات، تبادل کاتیونی، غلظت عناصر اصلی و جزئی) اندازهگیری شد. نتایج نشان میدهند عوامل طبیعی (انحلال هالیت، ژیپس و انیدریت، تهنشست کلسیت، آراگونیت، دولومیت و فرایند تبادل یونی) و انسانی (تخلیۀ فاضلابهای خانگی و روانابهای کشاورزی) مهمترین فرایندهای کنترلکنندۀ غلظت یونهای اصلی در آب رودخانۀ بادآور هستند. غلظت عناصر بالقوه سمی بهویژه عنصر سرب در نمونههای آب بهواسطۀ فعالیتهای انسان افزایش یافته است. نتایج آنالیز میکروبی آب نیز نشاندهندۀ آلودگی آب رودخانۀ بادآور است. pH نمونههای رسوب خنثی تا قلیایی است. رسوبات حاوی مقدار زیادی مادۀ آلی و کربناتکلسیم هستند و ظرفیت تبادل کاتیونی رسوبات زیاد است. بر اساس نتایج آنالیز غلظت کل، رسوبات رودخانۀ بادآور به عناصر کادمیم، کروم، نیکل آلوده هستند. بر اساس محاسبۀ درجۀ آلودگی، نمونههای رسوب رودخانۀ بادآور در ردۀ آلودگی درخور توجه تا بسیار آلوده به عناصر بالقوه سمی قرار دارند؛ این امر از فعالیتهای انسان بهویژه تخلیۀ فاضلابهای شهری و روانابهای کشاورزی به رودخانۀ بادآور ناشی میشود.
عنوان مقاله [English]
Geochemical study of water and sediments in the Badavar River, Lorestan Province: environmental iImplications
The Badavar River is an important surface water resource in Lorestan province. The purpose of this study is to assess the quality of the Badavar water and sediments. For these purpose, 19 water and five surface sediment samples were collected. The physicochemical properties of the water (i.e. pH, electrical conductivity, the major ion concentrations, microbial analysis, and potentially toxic element concentrations) and sediment samples (i.e. pH, organic matter, carbonate calcium, cation exchange capacity, major and trace element concentrations) were determined using standard methods. The obtained results indicate that the concentration of major ions influenced by natural processes (i.e. halite and gypsum dissolution, calcite, aragonite and dolomite precipitation, and ion exchange) and anthropogenic factors (i.e. discharge of domestic wastewater and agricultural runoff into the river). The concentration of the potentially toxic elements, especially Pb, is influenced by anthropogenic activity. The results of the microbial analysis confirm the pollution of the water samples with pathogenic agents. On the basis of pH values, the sediment samples are placed in neutral to alkaline class. Sediment samples are rich in organic matter and CaCO3, and their cation exchange capacity is high. The total concentration of elements in sediments shows that there is a risk of pollution with Cd, Cr, and Ni. The contamination degree values show that the studied sediments are highly polluted, which is due to the discharge of urban and agricultural wastewaters into the Badavar River.
Keywords: Hydrogeochemistry, pollution, Sediment, Badavar River
Rivers are the most available water resources for different usage purposes in the world (Chidya et al. 2011). The environmental quality of surface waters is influenced by both natural and man-made factors, the most important of which are mixing, mineral precipitation/dissolution, ion exchange, and discharge of the urban, agricultural and industrial wastewaters (Suthar et al. 2009; Zhang et al. 2010). Naturally- and anthropogeically- sourced pollutants are typically distributed between water and sediments. Therefore, for evaluating the environmental pollution of the river systems, both water and sediment chemistry must be considered. River sediments usually act as a sink and source for the pollutants; therefore, they are a very important component of river systems (Malvandi 2017).
The Badaver is an important river in the Lorestan Province, west of Iran. This river provides the water required for agricultural and livestock usage. This river recharges from the Garin Mountains, East of Noorabad, and discharges into Seymareh River. The long of the Badavar River (with a E–W trend is about 75 Km and its drainage area is about 1800 Km2. The average water discharge of Badavr in spring and summer is 8.5 and 0.8 m3/sec, respectively. A part of the Badaver River passes through the Noorabad City. Indeed, agricultural activity is a usual practice around the river. Thus, the quality of water and sediments in Badavar River can be influenced by discharge of agricultural and domestic wastewaters. The aim of the present study is to investigate the environmental quality of water and sediments of Badavar River, and to find the impact of natural and anthropogenic factors on the river.
Material & Methods
Nineteen water and five surface sediment samples were collected in selected sites. At each sampling site, water samples were collected in 1-litre prewashed polyethylene bottles; indeed, one sample was collected in sterile dark bottles for microbial analysis. The first samples were filtered using a vacuum pump and 0.45μm pore-size filter papers in order to separate particulate matter. The filtered samples were then split into two portions: one portion was acidified with HNO3 for the measurement of dissolved elements and the second unacidified portion was used for determination of dissolved major ions. The samples were kept at 4°C prior to analysis. Some physicochemical properties of the water samples (i.e. pH and electrical conductivity) were measured in situ using a portable multi-meter. The major ion concentrations, microbial analysis, and potentially toxic element concentrations (in water samples) and pH, organic matter, carbonate calcium, cation exchange capacity, and element concentrations (in sediment samples) were determined using standard methods. In order to find the source of major ions in water samples and to determine the most significant processes controlling the water chemistry, ionic ratios, correlation coefficients, and the saturation index of minerals were calculated. The water quality for irrigation usage was accessed through the calculation of sodium adsorption ratio (Zhang et al. 2012) and magnesium hazard (Ravikumar and Somashekar 2011). Indeed, the EC and pH values of the samples were compared with standard values (Sundaray et al. 2009). Water Quality Index (WQI) as a useful method for quality assessment (Kumar et al. 2015, Vasanthavigar et al. 2010) was calculated on the basis of ion concentration, EC, pH and Total Hardness. The concentration of toxic elements in the water samples were compared with standard values of FAO (1985) for irrigation purposes and the standard values in world fresh waters (Markert 1994).
For sediment quality assessment, some indices including geo-accumulation index (Muller 1969), enrichment factor (Sutherland, 2000), contamination factor (Hakanson 1980), and modified contamination degree (Abrahim and Arker 2008) were calculated.
Discussion of Results & Conclusions:
The EC and pH of the water samples vary between 430-730 µs/cm and 5.6-7.1, respectively. The EC values of the samples collected in the city district are higher than other samples, whereas their pH values are a little lower, showing the influence of domestic wastewater discharge on EC and pH of the water samples. The lower pH values may also be an indication of calcite precipitation (Das 2005).
The calculation of ionic ratios, saturation index of minerals and correlation coefficient values indicate that the natural and anthropogenic factors influence the environmental quality of both water and sediments in Badavar River. The most important natural factors which affect the hydrochemical properties of the water samples (i.e. the concentration of major ions) include the dissolution of halite, gypsum and anhydrite, the precipitation of calcite, aragonite and dolomite, and ion exchange. Discharge of agricultural runoff and domestic wastewaters into the river is the most important anthropogenic factor decreasing the water quality, especially with respect to PO4, Pb, Cd, Cr, Cu, Mn and Zn concentrations. The values of Magnesium Hazard are mostly lower than 50%; indeed, the Sodium Adsorption Ratios are <2meq/l. Therefore, the water of Badavar River is suitable for irrigation. The values of WQI of the Badavar River varies between 58.4–42.7; indicating the good to excellent quality of the water samples. However, the river water is microbially polluted, mainly because of domestic wastewater discharge. The concentration of Pb in most sites is higher than FAO standard (5µg/L; FAO 1985) and the concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Se and Zn are lower than FAO guidelines (1, 50, 100, 200, 5000, 200, 200, 20, and 2000 µg/L, respectively; FAO 1985). The concentrations of Cd, Co, Ni, Pb and Se in some samples, and the concentrations of Cr, Cu, Mn and Zn in all samples are higher than their values in natural fresh waters (Markert 1994) which confirms the impacts of anthropogenic activities (i.e. agricultural and domestic wastewater discharge into the river) on water quality.
Physicochemical properties of sediments play a significant role in retention, adsorption and re-adsorption of pollutants (Duodu et al. 2017). The pH value of the sediment samples ranges between 7.7 to 8.5; thus the samples are placed in neutral to alkaline class. Sediment samples are rich in organic matter (7.8–14.7%) and CaCO3 (26–45.5%), and their cation exchange capacity is high (37.4–77.3 meq/100 gr). On the basis of total concentration data, the concentration of Cu in some stations and the concentration of Cr and Ni in all sites are higher than TEC values (36.1, 34.4, and 22.7 mg/kg, respectively; MacDonald et al. 2000). Moreover, the concentration of Ni and Cr in all stations is higher than Probable Effect Concentration (PEC) values (111 and 149 mg/kg; MacDonald et al. 2000). This evidences show that the ecosystem of the Badavar River is at risk of being threatened by Ni and Cr. On the basis of total concentration data, the Badavar River sediments are polluted with Cd, Pb, Cr, Zn, Cu, Mn and Ni. The calculation of enrichment factor shows that Pb, Cd and Cr are mainly from anthropogenic activities (EF>1.5), whereas Zn, Cu, Mn and Ni are mostly from natural sources (EF<1.5). The contamination factor values are higher in sediments collected in the city district, confirming the effect of anthropogenic factors on sediment quality. The contamination degree values show that the studied sediments are placed in highly polluted class, which is due to the discharge of urban and agricultural wastewaters into the Badavar River. The obtained results in this study emphasize on the necessity of environmental management in the study area. The discharge of different kinds of wastewaters must be controlled.