Geochemical Distribution of Arsenic, Antimony and Mercury in Surface Waters and Bed Sediments from Aq- Darreh River, Takab, Northwest Iran
Total Page:16
File Type:pdf, Size:1020Kb
E3 Journal of Environmental Research and Management Vol. 4(3). pp. 0197-0208, April, 2013 Available online http://www.e3journals.org ISSN 2141-7466 © E3 Journals 2012 Full Length Research Paper Geochemical distribution of arsenic, antimony and mercury in surface waters and bed sediments from Aq- Darreh river, Takab, northwest Iran Yousef Rahimsouri 1*, Abdolmajid Yaghubpur 2 , and Soroush Modabberi 3 1 Department of Geology, Faculty of Sciences, University of Urmia, Urmia 57153 - 165, Iran. 2 Department of Geology, Faculty of Sciences, University of Tarbiat Moalem, 49 Mofateh Street, Tehran 15614 , Iran. 3 School of Geology, University College of Sciences, Tehran University, Enqlab Street, Tehran, Iran. Accepted 25 February, 2013 Aq-Darreh mining district is located in the Aq-Darreh river watershed, NW, Iran. The water and river-bed sediments of this area are very polluted due to the severe weathering and erosion of waste piles of Aq-Darreh Bala abandoned Sb mine and Aq-Darreh Au deposit. The concentration of As and Sb in water of Aq-Darreh river ranges from 3.2 to159 µg/l and 1.32 to 54.00 µg/l respectively. Also the amount of As, Sb and Hg in the Aq- Darreh river-bed sediments ranges from 38.6 to 1087.4 mg/kg (As), 1.87 to 93 mg/kg (Sb) and 0.096 to 23.7 mg/kg (Hg). Detailed chemical analyses of water and bed sediments samples of Aq-Darreh river and its distributaries indicate that geochemical background of this area, and also mining activities are responsible for these high concentrations of toxic elements. According to the analytical results (As, Sb and Hg concentrations) and their comparison to world river average values it is concluded that Aq-Darreh river is amongst the heavily polluted water bodies of the world. Keywords: Environmental geochemistry, water pollution, river-bed sediment contamination, Aq-Darreh mining district, Takab, NW Iran. INTRODUCTION Aq-Darreh mining district (including Aq-Darreh gold The main water source of the mine area is Aq-Darreh deposit and Aq-Darreh Bala abandoned antimony mine) river flowing from northwest of the mine to the southeast is located 38 km northwest of Takab, west Azerbaijan (Figure. 1). More than 80 percent of the runoff of Aq- province, NW Iran (Figure. 1). Gold, As and Hg Darreh Au mine area reaches to Aq-Darreh river and the mineralization in these prospects were classified as rest flows to Sarouq River by Qiz Qapan and Angurd Carlin-like type (Karimi, 1993) and some of them are streams that are flowing in the southeast of mine area currently mined without paying enough attention to (Figure. 2). The runoff of Aq-Darreh Au mine area joins environmental consideration. Aq-Darreh deposit is mined the Sarouq River mostly via Aq-Darreh river that along for gold and the waste rocks containing high with several other small stream waters from other concentration of potentially toxic elements, especially As, prospects flows to the lake of Zarrineh Rud reservoir dam Sb and Hg are dumped as mine heaps. (Figure. 1). The annual discharge of Sarouq River to the Takab area has a semi-arid climate with moderate Zarrineh Roud reservoir dam is estimated to be more summers and very cold winters with an average annual than 225 million cubic meters (Modabberi and Moore, C. Annual precipitation is about 2004a). The water in the Zarrineh Roud reservoir dam is؛ temperature of about 9 400 mm, falling mostly as snow (Modabberi, 2004; used for agricultur and urban use of several cities in Modabberi and Moore, 2004a). Kurdistan and East and West Azerbaijan provinces (Modabberi, 2004). Mining activities in Aq-Darreh mining district has been taken place in two stages. The ancient mining activities *Corresponding authors: E-mail: [email protected] (first stage) dates back to about 1000 years ago (Zavosh, 0198 E3. J. Environ. Res. Manage. Figure: 1 Location map of the study area. Figure: 2 Geological map of Aq-Darreh mining district and downstream environment. Rahimsouri et al 0199 1976), in an area of 6 km 2. The new phase of activities The ore minerals include arsenian pyrite or melnikovite, (second stage) have been started in 1965 (Urdea et al., arsenopyrite, scorodite, jarosite, cinnabar, orpiment, 1970). In 1990 the gold occurrence in Aq-Darreh area realgar, stibnite, sphalerite, iron oxides (hematite,goethite have been explored by the geologists of Iranian ministry and limonite), manganese oxides, barite and fluorite of mines and metals (Kansaran, 1992). The total reserve (Yaghubpur and Rahimsouri, 2009). of Au in the eastern and western parts of Aq-Darreh Au Gypsiferous marl with interlayers of sandstone and deposit is estimated to be about 11.5 and 2.16 million conglomerate (OMmq) that according to Babakhani tons with an average concentration of 2.48 and 1.53 and Ghalamghash (1995) is also Early-Middle mg/kg respectively. The mineable reserves in the eastern Miocene in age. and western parts are estimated to be about 9 and 2 Red marl and sandstone (Ms) with gypsum million tons respectively (Baghosian and Shivaei, 2003). interlayers covering discordantly the andesite At present, more than 850000 ton of rocks containing (OMva) and gypsiferous marl(OMmq) in the north some sulfide minerals and toxic elements including As and east of the study area. This rock unit is overlain by horizontal layers of Quaternary travertine (Qtr) . and Hg with lesser amounts of Sb have been piled up as The rest of area is covered by recent sediments waste dump in the mine area, that should be carefully including gravel fans, surface soil and agricultural studied in terms of their potential environmental impacts lands (Qt2) and recent alluvium (Qal) . (Yaghubpur and Rahimsouri, 2009). In the northwest of Aq-Darreh Bala village a granitic intrusive body crops out (Aq-Darreh granite , Gr ) which is an equigranular body composed of quartz, pertitic Geology feldspars and few muscovite. Based on field observation and its relation to the surrounding rock units, it appears According to Stocklin (1968), the Aq-Darreh area is that the age of this granite is post-Cambrian and pre- located in Sanandaj-Sirjan structural zone and based on Oligocene and it is probably Jurassic in age. Nabavi (1976), the area is a part of Khoy-Mahabad zone. From the structural point of view, the area is composed of It seems that Aq-Darreh area is located in the intersection a syncline in the north and an anticline in the south of Aq- between Alborz-Azerbaijan, Central Iran and Sanandaj- Darreh Au mine area with their axes trending northwest– Sirjan structural zones (Babakhani and Ghalamghash, southeast (Ghanati, 1995). Three fault systems trending 1995). NW–SE, NE–SW and N–S have been noted in the Aq- Proterozoic, early Cambrian and Tertiary rock units Darreh mining district. The main fault is trending crop out in the north of Takab. In the south of Aq-Darreh northwest–southeast and it controls the course of the Bala Village (abandoned Sb mine valley) which is also Aq-Darreh river (Figure. 2). the site of ancient mining activities, a black shale unit, 3 to 6 meters thick, crops out for about one kilometer long and it is apparently proterozoic in age. This shale is MATERIALS AND METHODS overlain by an Oligo-Miocene calcareous marl, marly tuff, and limestone containing some antimony-bearing The geological map of the study area (Figure. 2) were siliceous veins. Different rock units in the Aq-Darreh river prepared using satellite images (Google Earth, 2009- watershed have been studied (Figure. 2) and are briefly Cns/Spot Image, Imagenery date Apr. 6, 2004), 1:100000 described here: geological map (modified after Babakhani and Tuff and hyaloclastic tuff breccia (Tf), thin to thick Ghalamghash, 1995) and detailed field work (rock bedded with andesitic composition and porphyritic and sampling, structural geology and petrographical studies). vitrophyric textures. One hundred twenty six thin and 148 polished sections Andesites (OMva), gray, brown or violet in color. The from host, waste, and other rock units were studied to age of this rock unit ranges from 14.4±0.3 to 16.3±0.3 Ma obtain mineralogical and petrological characteristics and according to Mehrabi et al. (1999). This rock unit extends 22 stations were selected for river-bed sediment and from north to northeast of the Aq-Darreh river watershed. water sampling according to geological informations and Thick bedded to massive limestone (OMl2q) forming location of the distributaries of Aq-Darreh and Sarouq high reliefs in the Aq-Darreh Au mine area. The age of rivers (Figure. 3). this limestone has been postulated to be early-Middle Water samples were collected in June 2007. In all Miocene based on their characteristic fossils (Babakhani stations, field parameters including pH, Eh, TDS (total and Ghalamghash, 1995). This unit extends throughout dissolved solids), EC (electrical conductivity), salinity and the Aq-Darreh Au mine area and it is the host rock of gold temperature of water were measured by Sension 156 mineralization. Concentrations of gold in this unit ranges multiparameter measuring instrument. from 0.2 to 19.3 ppm and concentrations of potential toxic Two water samples were carefully taken with 250 CC elements are As (0.17 to 19.5 %), Sb (0.022 to 1.7 %) open-mouth polyethylene bottles in each station. and Hg (0.001 to 0.22 %) (Kansaran, 1992). 0200 E3. J. Environ. Res. Manage. Figure: 3 Location of sampling stations in the study area. Table: 1 The accuracy and precision estimating results (in %) Accuracy (A) of the analytical method for elements was of As and Sb in water samples . estimated by calculating the absolute systematic error between the determined (X a) and recommended values As Sb (X b) of standard materials using equation: %A= ( │Xa- Accuracy 3.1 0.7 Xb │/Xb)×100.