تاثیر واحدهای رسوبی در ترکیب و کیفیّت آب: مثالی از حوضه آبریز کارده، شمال شرق مشهد، ایران

کارده یکی از مهمترین حوضه های آبریز در استان خراسان رضوی است که در شمال شرق شهرستان مشهد قرار دارد و تامین کننده قسمتی از آب شرب و کشاورزی منطقه محسوب می‌گردد. بخش عمده منطقه توسط سازندهای کربناته مزدوران و سیلیسی آواری شوریجه و بخش کمتر توسط رسوبات نئوژن و عهد حاضر پوشیده شده است. هدف اصلی این پژوهش، مطالعه کیفیّت آب‌های سطحی و تاثیر سنگ شناسی منطقه بر آن است. بر اساس آنالیزهای نمونه‌های سنگی واحدهای کربناته، سیلیسی آواری و تبخیری، منشا احتمالی افزایش غلظت کاتیون‌های کلسیم، منیزیم، آهن، سدیم، آلومینیم و همچنین آنیون‌های سولفات و بیکربنات محسوب می‌گردند. بر اساس نتایج حاصل از مطالعات انجام شده و مطابقت آنها با استاندارهای بهداشت جهانی و ایران و استفاده از نمودارهای شولر، ویلکاکس و پاپیر، وجود مقدار ‌یون‌های کلسیم، منیزیم، سدیم، پتاسیم، کلر و سولفات و همچنین میزان اسیدیته، مواد جامد محلول در آب و سختی کل، سبب گردیده که آب حوضه آبریز کارده به دلیل خورندگی و رسوب‌گذار بودن جهت مصارف صنعتی مناسب نباشد. همچنین برخی نمونه‌های آبی، گرچه از نظر وجود کاتیون‌های سدیم و منیزیم و آنیون سولفات خوب تا قابل قبول بوده، اما به دلیل وجود tds و th بالا از نظر شرب انسانی نامناسب هستند. از سویی، عمده آب‌های حوضه آبریز کارده دارای کیفیّت خوبی بوده و به طور عمده سولفات و کلسیم ‌یون‌های غالب محسوب می‌گردند. لذا نوع آب به طور عمده سولفاته کلسیک است. در نهایت عمده نمونه‌های آب حوضه آبریز کارده در کلاس c2s1 طبقه‌بندی شده که جهت استفاده کشاورزی مناسب هستند.

The effect of sedimentary units on composition and quality of water: an example from the Kardeh catchment, northeast of Mashhad, Iran

IntroductionKardeh catchment is a part of the KopetDagh zone and contains a variety of lithological composition. Mozduran and Shurijeh formations, Neogene and recent deposits form most of the outcrops in this area (Nabavieh, 1998). In this study, considering the importance of Kardeh catchment area as sources of water for the underground and surface water resources for drinking in the west of Mashhad, we have analyzed water samples from each subcatchment and conducted chemical analysis of rocks. The impact of harmful elements in the river water, resulted from lithological erosion, in this basin are discussed. In addition, the water quality of the river in terms of agricultural use, drinking, and industry usage is also investigated (Li Zhang, 2008; Han et al, 2010). Materials and MethodsIn this study, 17 water samples and 9 rock samples were collected for analysis. For this reason, temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), concentration and absorption of some ions have been measured. Based on the results, in order to determine water quality for drinking, agriculture and industrial usage, we have made comparisons with the World Health Organization drinking water standards and data from the Standards and Industrial Research Institute of Iran (Schuler, Wilcox and Piper diagrams). Rock samples have been analyzed by ICP method. Two polished thin sections were studied to determine the composition of mineral components, using the Scanning Electron Microscope (SEM) equipped with EDS. DiscussionBased on the analysis carried out in the Kardeh catchment, the maximum TDS is 863.35 mg/l in the Al area, and the minimum is 571.95 mg/l in KarimAbad. The maximum electrical conductivity (EC) is 557 microzimens/sec in the Al area, and the minimum EC is 369 microzimens/sec in KarimAbad. The highest temperature of 24.6°C is related to the lake, and the minimum temperature measured is 10.3°C in the Mareshk area. The results indicate that among cations, magnesium and potassium have the lowest concentration, whereas sodium and calcium have the highest. Among anions, bicarbonate has the maximum concentration, and sulfate the minimum. Petrographic studies indicate that carbonate and sandstone are the main types of rocks in the study area. Carbonate facies are mainly dolomite, whereas sandstone facies are sublitharenite and feldspathic litharenite with silica, carbonate and iron oxide cements. Based on ICP analysis, aluminum, calcium, iron, potassium, magnesium, and sodium are the main elements in the rock samples. Mozduran (carbonate strata) and Shurijeh (siliciclastic strata) formations and also evaporative units are the probable sources of watersoluble ions (Kazemi et al., 1395).Based on the results of the analysis of water samples, the water is not suitable for industrial usage due to corrosion and precipitation of chemicals. Also, according to the Schuler diagram, some water samples are not suitable for drinking. On the other hand, according to the Piper diagram (Piper, 1944), the major water samples have good quality and contain sulfate, chloride, and calcium as main ions. Thus, according to the Wilcox diagram (Wilcox 1995), the major water samples are in class C2S1. So, based on the presence of slight salt in the water, therefore it is suitable for agricultural use. ConclusionThe main ions in the Kardeh water samples are sodium, calcium, magnesium, iron, sulfate, and carbonate. Based on the analytical results, for drinking all samples are moderate to good, and are classified in class C2S1 of the Wilcox diagram. Although these samples are acceptable for agriculture, they are unacceptable for industrial usage. Finally, based on the Piper diagram, the quality of water samples are in sulfate and chloride groups. In the Kardeh catchment, the probable source of ions in water samples could be carbonate and siliciclastic rocks as well as Neogene and recent deposits. Keywords: Kardeh catchment; Khorasan Razavi; lithology; water quality. ReferencesHan, G., Tang, Y., Xu, Z., 2010. Fluvial geochemistry of rivers draining Karst terrain in southwest China. Journal of Asian Earth Sciences, 38: 6575.Kazemi N., Poursoltani M.R., Fazel Valipour M.E. 2016. The study of Kardeh catchment groundwater, north of Mashhad, Iran, The Second Conference on Environmental Science and Engineering Technologies, Tehran University, 110 (in Persian).Li, S., Zhang, Q., 2008. Geochemistry of the Han River Basin China, 1: Spatial distribution of major ion compositions and their controlling factors. Applied Geochemistry, 23: 35353544.Nabavieh, S.M., 1998. Geological map of Kalat, 1:100000, Geological Survey of Iran.Piper, A.M., 1944. A graphic procedure in the geochemical interpretation of water analysis. Trans. American Geophysical Union, 25 (6): 914928.Wilcox, L.W., 1995. Classification and Use of Irrigation Water, U.S. Department of Agriculture, Washington, Circular, 969 p.