شناسايي خاستگاه مواد محلول آب رودخانه خررود (جنوب استان قزوين) با روش هاي آماري

Provenance determination of dissolved load of Khar-Rud River water (S Qazvin Province) using statistical parameters

سيستم هاي رودخانه اي يكي از پوياترين عوامل جابه جايي و ته نشست مواد رسوبي در طول دوره كواترنري هستند؛ آن ها مواد جامد و محلول حاصل هوازدگي رخنمون سازندها را به حوضه هاي رسوبي منتقل مي كنند. دراين پژوهش تاثير سازندهاي زمين شناسي بر ويژگي هاي هيدروژئو شيميايي آب رودخانه خررود از طريق آزمايشات شيميايي و بررسي آماري مورد بررسي قرار گرفته است. حوضه آبريز اين رودخانه در زون ساختاري ايران مركزي قرار دارد. 35 نمونه (متمركز در طول 40 كيلومتر از بازه باختري رودخانه)، در دو فصل خشك وترسال آبي 94-93 مورد آزمايش قرار گرفتند. سپس داده هاي هيدروژئوشيميايي با استفاده از تكنيك هاي آماري (ماتريكس همبستگي، آناليز خوشه اي و نمودار جعبه اي) با كمك نرم افزار SPSS مورد بررسي قرار گرفتند. نتايج حاصل از تحليل هاي آماري نشان دادند كه سولفات كلسيم و كلريد سديم (با منشا رسوبات تبخيري) بيش ترين نقش را در افزايش نمك هاي محلول آب رودخانه داشته اند. سنگ هاي كربناته در اين رابطه نقش كم تري داشته اند.

River systems are considered as dynamic sediment transport and deposition agents during Quaternary period; they carry dissolved and sediment loads which are produced by weathering of outcrops of geological formations to sedimentary basins. The aim of this study is to investigate geological parameters which affect on the hydrogeochemical properties of Khar-Rud River water، using chemical experiments and statistical methods. The river basin is located in Central Iran structural zone. 35 river water samples (taken from 40 km of the western sector of this river during wet and dry season of 2013-2014 hydrological year) were analyzed. The obtained data were analyzed by some statistical methods (correlation coefficient، cluster analysis and box plot) using SPSS software. The statistical results indicate calcium sulfate and sodium chloride (originated mainly from Miocene evaporite deposits) have the highest effect on the salt content of the river water. The role of carbonate rocks with this regard were not significant. Introduction: Quality of water resources are controlled by solubility and lithology of drainage basins; rivers are important as fresh-water resources and as an agent of ground-water recharge. The river-water quality is changed by chemical properties of the water of its tributaries. Carbonate and evaporate minerals are more important with this regard. The drainage basin of Khar-Rud river is a part of Namak-lake basin in Cntral Iran. The aim of this research is to find the origin of the salt content of this river. Therefore، the focus of the research was on the effect of the basin lithology on the river water quality. Materials and Method: In order to recognize the sources of the dissolved content of Khar-Rud river water، lithology of the outcrops in the river basin were studied; the emphasis was on layers with evaporate origin. 35 river water samples (taken from 40 km of the western sector of this river during wet and dry season of 2013-2014 hydrological year) were analyzed. Physiochemical analysis were performed on these samples. Water samples were taken from 10 cm depth of the water surface (Fig. 1). The physiochemical analysis include: temperature، pH، electrical conductivity، the main anion contents (Cl-، SO42-، CO32- and HCO3-)، the main cation contents (Na+، K+، Ca2+ and Mg2+) and total-dissolved solids (TDS، tables 1 and 2). The obtained data were also analyzed by some statistical methods (correlation coefficient، cluster analysis، CA، and box plot) using SPSS software (version 16 for Windows) and Excel software (2007) (Table 3; figs. 4 and 5). Results and discussion: Khar-Rud river flows westward along the Khar-Rud fault; the river basin is located in the west part of the Central_Iran Structural Zone، adjacent to the Sanandaj-Sirjan Structural Zone. The outcrops on the west (north) bank include Mesozoic formations (Lar، Shemshak، Delichay formations and Cretaceous limestone) and Qom Formation (Cenosoic). The outcrops on the east bank mainly consists of the Upper-Red Formation (Miocene)، most evaporite minerals (halite and gypsum) are found in this formation (Figs. 2 and 3). The Khar-Rud river has six tributaries (Fig. 1) each of which has a distinct effect on the chemical composition of the river water (Fig. 4). Based on the chemical composition of the waters، these tributaries are classified in three types: 1- sodium-chloride type (i.e، Shur، Dashatak، Qare-Mohammad and Hesar-Valiasr)، 2- calcium-sulfate type (Qare-Mohammad and Shur) and 3- calcium-carbonate type (Nalbandan). According to the Pearson's correlation coefficients results، TDS has a positive significant relation with SO4+2، Ca+2، Cl-، Na+ and a shows significantly negative relationship with HCO3-2 and K+; a negative correlation is also observed between TDS and HCO3-. This indicates that gypsum and halite are the main dissolved components in the Khar-Rud River water; carbonate minerals are not significant with this regard. The cluster analysis of data suggests that there are two distinct groups of components، which allows for a tentative assignment of geological sources. The first cluster contains TDS، SO4-2، Cl-، Ca+2، Mg+2، Na+، electrical conductivity (EC) which might be derived from the evaporate minerals of the Upper Red Fm.). The second cluster containing HCO3-2 and K+; they might be originated from other geological sources. Conclusion: This research was done in order to investigate geological parameters which affect on the hydrogeochemical properties of Khar-Rud River (S. Qazvin Province) water. Results show that gypsum and halite are the main dissolved components of the River water. They are mainly originated from the Upper-Red Formation (Miocene).