ارزیابی کیفیت آب رودخانۀ چالوس با استفاده از تجزیه ‌و تحلیل آماری و شاخص کیفیت آب (wqi)

آلودگی رودخانه‌ها یکی از خطرات جدی برای محیط‌ زیست، سیستم‌های آبی و سلامت انسان است. در این مطالعه اثر فعالیت‌های انسانی بر کیفیت آب در رودخانۀ چالوس مورد ارزیابی قرار گرفت. بدین‌منظور، نمونه‌برداری در دو دوره (مهر 1398 تا شهریور 1399) انجام شد. در هر دوره از هر ایستگاه سه نمونه از آب‌های سطحی جمع‌آوری و مورد تجزیه‌ و تحلیل قرار گرفت. در این پژوهش پارامترهای کیفیت آب (دما، ph، هدایت الکتریکی، مواد جامد محلول، جامدات معلق، کدورت، شوری، کاهش پتانسیل اکسیداسیون، قلیایی، سختی کل)، اکسیژن‌رسانی (اکسیژن محلول، اشباع اکسیژن، نیاز اکسیژن بیولوژیکی)، مواد مغذی (n-nh4, n-no2, n-no3، کل فسفات، کل فسفر)، عناصر کمیاب، آلودگی غیرآلی و محتوای کلروفیل معلق از جمله پارامترهای بیولوژیکی بررسی شدند. روش‌های آماری متعددی برای نتایج تجزیه‌ و تحلیل پارامترها از جمله روش آماری مولفه‌های اصلی (pca)، شاخص همبستگی پیرسون (pci) و تجزیه‌ و تحلیل خوشه‌ای (ca) مورد استفاده قرار گرفت و هم‌چنین از شاخص کیفیت آب (wqi) برای تعیین کیفیت جریان آب و ضریب خطر (hq) و شاخص خطر (hi) جهت بررسی ارزیابی ریسک از نظر بهداشت عمومی برای عناصر کمیاب استفاده شد. نتایج نشان داد که کیفیت آب رودخانه چالوس از ایستگاه s1 به‌سمت پایین‌دست به‌دلیل افزایش فعالیت‌های انسانی، جاده‌سازی در حاشیۀ بستر رودخانه، ورود پساب از زمین های کشاورزی و فاضلاب خانگی و تخلیه فاضلاب مزارع پرورش دام در رودخانه کاهش ‌یافته است و هم‌چنین بررسی کیفیت آب رودخانه از نظر خطرات بهداشت عمومی نشان ‌داد که می­توان از آب ایستگاه s1 به‌عنوان آب آشامیدنی استفاده کرد و خطری بالقوه برای سلامت بزرگسالان و کودکان ندارد، اما از آب ایستگاه s2 و به‌ویژه ایستگاه s3 نمی‌توان برای آشامیدن استفاده کرد و باعث ایجاد خطرات بالقوه برای سلامت بزرگسالان و کودکان می‌شود.

Evaluation of water quality in the Chalus River using the statistical analysis and water quality index (WQI)

Introduction River pollution is one of the serious risks to the environment, water systems, and human health. Regular monitoring and protection of river water quality is therefore vital to meet environment, and human needs. The increasing trend to fresh water highlights the management of river water resources as a crucial resource. Meanwhile, population growth, irregular urbanization, industrialization, overuse of chemicals materials in agriculture (such as fertilizers and pesticides), discharge of domestic sewage, and solid waste into watercourses, sand mining in riverbeds, water transfer diversion, has seriously challenged the rivers regimes and river ecosystems.Materials and MethodsThe effect of agricultural activities on water quality in the Chalus River was examined. Sampling was conducted and analyzed in surface water at three points from October 2019 to September 2020. Three surface water samples were collected from each station and water quality variables were analyzed. The following water quality parameters have been analysed in the current study; temperature, pH, conductivity, soluble solids, suspended solids, turbidity, salinity, reduction of oxidation potential, alkali, total hardness. Also, oxygen demand parameters of dissolved oxygen, oxygen saturation, biological oxygen requirement were examined. Meanwhile, the nutrientrelated water quality parameters include NNH4, NNO2, NNp3, total phosphate, total phosphorus are also evaluated. The heavy metals, inorganic pollution parameters, and suspended chlorophyll content of biological parameters were the other investigated parameters. Multiple statistical methods were used for the results of analyzing the parameter including principal component analysis (PCA), Pearson correlation Coefficient (PCC), and cluster analysis (CA). In addition, water quality index (WQI) was used for determining quality of surface water, hazard quotient (HQ), and hazard index (HI) for evaluating the public health risk for heavy metals.Results and Discussion The water quality of Chalous River has decreased from S1 station to downstream. The water quality index based on public health risk assessment showed that station S1 water could be used as drinking water and did not pose a potential risk to the health of adults and children. However, the water quality at Station S2, and especially Station S3, cannot be used for drinking puprpos, due to improper quality and may poses potential risks to the health of adults and children. The station S1 with an average of 15.62 categorized in the excellent water quality category. Meanwhile, the station S2 and S3 with an average of 25.5, and 49.8 assigned as good water quality status, respectively. The amount of As, Cd, Co, Ni, Pb was very small at the studied stations. The hazard coefficient (HQ) and hazard index (HI) values calculated to determine the risk of heavy metal effects on health were identified as noncarcinogenic. HI values of heavy metals calculated for adults and children were Mn> Cu> Al> Zn> Fe, respectively. The manganese and copper are more involved in noncarcinogenic health risks. Also, the values of HQingestion and HQdermal values and the HI value are less than one.Conclusion A combination of point and nonpoint source pollution have been identified as the main source of water quality deterioration. The water quality parameters of Chalous River in S1 station has not exceeded the permissible level of the national standard of Iran. While, the water quality in S2, and S3 stations has decreased that poses potential risks to the human health and need a pollution prevention action plan. The factors such as municipal wastewater, septic tank and water leakage from horse stables, natural and artificial fertilizers used in agriculture, runoff and rock pebbles in the basin are the causes of pollution.