Anthropocentric perspective on climatic variability, potentially toxic elements, and health risk assessment in the Mansehra district: a case study of the Kunhar River, Pakistan

Various aspects of development depend significantly on rivers because they are an important source of freshwater (Link et al. 2016; Gleeson & Richter 2018). Grazing by livestock is the main anthropogenic disturbance of native grasslands, and the main factor affecting the accumulation of potentially toxic metals (PTMs) by grazing animals is the presence of the metals (Li et al. 2021). Human activities can alter dissolved organic matter (DOM) in lakes through both direct (i.e., exporting DOM of anthropogenic sources) and indirect effects (i.e., enhancing the autochthonous production of DOM via nutrient loading). Distinguishing between the direct and indirect effects of anthropogenic activities remains highly challenging due to the interdependence of associated environmental variables (Liu et al. 2022). Drinking water is typically acquired from surface waters such as surface water bodies (lakes, rivers, streams, etc.) and groundwater (springs, underground streams, etc.) (Asfaw et al. 2018; Coffer et al. 2021; Ali & Muhammad 2022; Muhammad & Usman 2022). Also, floods bring about immediate material damage caused by the direct effects of high water levels and accelerated flows (Soomro et al. 2021b). Agricultural overflow and effluents from settlements and factories make their way to rivers in a watershed, where pollutants are either diluted or transported downstream. Plants and factories, the hallmarks of industrialization, are essential to a country's economic growth (Yao et al. 2015). To protect the ecological environment, biodiversity, and natural resources, one must protect the integrity and authenticity of typical and unique ecosystems from damage, and leave a valuable natural heritage for future generations (Pan & Chen 2021; Zhao et al. 2022). A variety of physical and geochemical proxies for weathering intensity have been explored to understand loess provenances, environmental, and climatic variations in the regions of deposition (He et al. 2021). Physical and biogeochemical heterogeneity dramatically impacts fluid flow and reactive solute transport behaviors in geological formations across scales (Zhang et al. 2021). Rivers susceptible to residential wastewater discharge and other human influences and drivers of different factors were identified by utilizing a geographical detector, especially the influences of human activities in the region (Amin et al. 2021; Quan et al. 2022). The residential environment has been suggested as an important source of environmental chemicals to human exposure. House dust has been broadly employed to investigate the occurrences of environmental chemicals in an indoor environment (Yang et al. 2022). River ecosystems across the globe have already suffered from the impacts of climate change, and these impacts are only expected to worsen (Soomro et al. 2022). However, the raw materials for the production of wastes they release are harmful to the environment and cause water and soil contamination at multiple levels (López-Delgado et al. 2020; Silva et al. 2022; Verma & Sharma 2022). As more countries pursue plans for geologic disposal of accumulated high-level nuclear waste, quantifying the fate and transport of radionuclides in complex fractured rocks has become an important issue ((Zhang et al. 2022). Excessive reactive N in terrestrial and marine ecosystems from large applications of fertilizer has impacted the balance of the global N cycle and contributed to numerous eco-environmental problems (Lin et al. 2021). Precipitation is a major determinant of vegetation growth and the impact of precipitation variability is more pronounced in ecosystems where sensitive vegetation is apparent in the Kunhar River basin (Soomro et al. 2021a). Deficiency of high efficiency and cost-effective treatment technology prevents industrial effluents from obtaining safely treated and organizational control and monitoring inadequacy. Metals and alkaline earth metals with concentrations of more than 5 g cm³ were generally referred to as ‘heavy metals,’ a term that includes any metallic component with a high density (Liu et al. 2019; Tyopine et al. 2020). Human activities have accelerated global habitat loss and fragmentation, transforming continuous habitats into smaller, isolated habitat fragments surrounded by disturbed landcover (Yan et al. 2022). It's clear that these elements are significant for critical metabolic activities throughout all species of life, but at concentrations greater than any of those found naturally, they can be toxic (Brudvig et al. 2007; Mirrione et al. 2014; Muhammad & Ahmad 2020). Among the most key problems facing modern humanity is the pollution of earth and water by toxic substances connected to characteristics of confidentiality, stability, and permanence (Ernst 2012; Briffa et al. 2020).

Even while toxic substances could be detected in minerals, their occurrence is generally the direct result of human activities (Bloise et al. 2016; Rebello et al. 2021). The quality of drinking water may deteriorate when heavy metals affect the supply of water at various depths, especially surface water, reservoirs, and subsurface (Khatri & Tyagi 2015; Bhateria & Jain 2016; Gyamfi et al. 2019). Measuring the amounts of heavy metals in freshwater is one way to examine water pollution in the Kunhar River (Muhammad et al. 2021). Health complications and the incapability of people to get along with each other are two visible signs of the widespread poverty that have been recorded (Braithwaite & Mont 2009). The locals consume the water for all kinds of domestic purposes, including drinking, cleaning, bathing, and washing. The purpose of this research was to investigate whether or not it was safe to drink water from the Kunhar River, as well as to quantify the number of heavy metals in it.

The metals determined to be at harmful levels were examined regarding their potential effect on human life (Fe, Mn, Zn, Cd, and Cr). The analysis followed a healthcare risk-based approach of non-carcinogenic living beings, defined by Qiu et al. (2021). The toxic substances in the Kunhar River water were determined using the following formula (Muhammad et al. 2011).

Intake of antibiotics from the environment by drinking water and food may disturb the microbiome, especially the gut microbiota in the human body. A solid-phase extraction accompanied by an excessive performing separation system that used a mixture of liquid chromatography and mass spectrometry in tandem was performed to determine the chemicals in the surface water samples (HPLC-MS/MS) (Hong et al. 2021). Ethylenediaminetetraacetic acid (EDTA; 100 mg/200 ml) was combined with such a water sample (Madadrang et al. 2012). Two different solid-phase extraction (SPE) cylinders (3 ml, 60 mg) have been used, and the device was set to operate at a fluid rate of 5 ml/min. Before incorporating water samples into the instrument, 3 ml of acetonitrile–water was added into the concurrent SPE tubes, followed by 3 ml of Milli-Q at a continual fluid percentage of 3 ml/min. SPE containers are, therefore, placed through with a suction drying for 2 min. Consequently, the preferred antibiotic concentration levels contained in the SPE cylinder were retrieved using a combination of acetonitrile and water (2.5 ml) and methanol and formic acid, accompanied by 1 ml of Milli-Q water. Untreated sewage specimens were reduced from 10 to 1 ml by rinsing the molecules in a stream of nitrogen at 35 °C. The analysis was performed on a 1290 HPLC system utilizing HPLC-MS/MS to use a ZORBAX 1.8 m RRHD (502.1 mm) section (Matuszewski et al. 2003). In an intensity mode, 0.1% formic acid (A) was disintegrated in acetonitrile (B) at a flow rate of 0.4 ml/min, with the following criteria: 95% (A) for 1 min; from 95 to 50% (A) for 2 min; maintains at 50% (A) for 2.6 min; from 50 to 95% (A) for 2 min. A positive development stage evaluation was carried out on a Triple Quadruple 6400 ESI mass spectrometer by Ali et al. (2015). The MRM peak value transition was utilized for the monitoring, and the eventual change in results was controlled for quality control.

The mean observations categorized in the same human activities have been presented in graphs to assess the influence of various human activities in water samples using Origin 2018 software. Analysis of variance (ANOVA) was used to determine the statistical relationship between the influence of multiple human activities on the quality of water (ANOVA). To detect a statistical difference between the four different categories of human-caused activities, T-tests were performed to compare the amount that each pair of variables changed throughout the seasons in regards to the river water's quality using Microsoft Excel 2016 (Charfi et al. 2013). The criterion for evaluating whether or not a variation was substantial was a p-value of lower than 0.017. Each sample spot to measure physicochemical attributes, nutrition levels, and heavy metal content in factor analysis and principal component analysis (PCA) was executed using Origin 2018. The method detection limit for all variables below the measurement thresholds within the input data for the multivariate analysis was set at 50%.

One-way ANOVA showed that there was a significant difference; Station 7 was the source of the variation. Electrical conductivity measurements fluctuated around 0.09 and 0.26 mS/cm. From February to June, some levels reported at Station 5 were too excessive, while in January, certain values recorded at Station 7 were too high. An ANOVA showed statistically significant variability, with Stations 4 and 7 being the major contributors. Between 7.33 and 7.72, the pH concentrations were recorded. The outcomes of a one-way ANOVA testing exhibit that it was a statistically considerable variation throughout all locations. Turbidity readings varied between 1.13 and 2.74 mg/l. Each value was within the allowable range. The summary of the heavy metal content is presented in Table 1.

Each ANOVA revealed a statistically substantial variation between locations, indicating Station 2 as the source of variability. The TSS values were as follows: 0.4–9.7 mg/l. In all the stations, the results were between tolerable limits. According to a one-way ANOVA, Station 4 was the main source of the unique variance. The TDS levels were relatively constant, ranging between 64 and 142 mg/l. Depending on the outcomes of a one-way ANOVA, it is obvious that Stations 2 and 3 are the primary contributors to the variance observed. Chloride amounts were determined to be between 22 and 68 mg/l. Station 2 and 3 data from March 2021 to September 2021 revealed certain readings that were too high. An ANOVA using only the results at Stations 2 and 3 indicated a statistically considerable change. Nitrate concentrations were estimated to be anywhere from 0.02 to 0.09 mg/l. All assessed amounts were found to be within the allowed limits. A considerable difference was found, with Station 1 being the main contributor, according to a one-way ANOVA analysis.

Zinc (Zn) CDI results for children and adults in Station 5 were 0.031 and 0.072 mg/kg/day, respectively. Such values were 0.024 and 0.056 mg/kg/day in Station 3 for children, and 0.018, and 0.042 mg/kg/day in Station 3 for adults. In Station 7, the Cr levels for children and adults were 0.002 and 0.006 mg/kg/day, respectively. In Stations 1 and 4, the Cr values for children and adults were 0.001 and 0.003 mg/kg/day, respectively. Cadmium (Cd) values for adults and children in Station 8 were 0.002 and 0.004 mg/kg/day, respectively. In Stations 9 and 6, the values for adults and children were 0.001 and 0.003 mg/kg/day, respectively. Nickel was also only found in Station 2, where it was too high. The daily chronic intake for adults was 0.001 mg/kg/day and for children, it was 0.002 mg/kg/day.

For children and adults, the Fe is 9.71 and 22.4 in Station 1; 6.85 and 16.41 in Station 2; and 6.14 and 14.28 in Station 3, respectively. For both adults and children, the Fe was more than 1 in all the stations. In Station 1, the Mn for adults is 0.57 and for children it is 1.36. The children's HQ was greater than 1. In Station 1, the Zn for adults is 0.10 and for children, it is 0.24. In Station 2, it is 0.08 and in Station 3, it is 0.06 and 0.14. In Stations 1, 2, and 3, the Zn for both adults and children was less than 1. In Station 1, the Cr for adults and children is 0.67 and 20, respectively; in Station 2, it is 3.33 and 10; and in Station 3, it is 3.33 and 3.33, respectively. The Cr for children in Station 1 was higher than for adults and children in Stations 2 and 3. The HQ and CD for adults and children is stations 1, 2, and 6 in Station 2, and stations 2 and 2 in Station 3. In all of the stations, the HQ and CD for both adults and children was higher than 1. Ni for adults and children is only 0.05 and 0.1 at Station 1. The HQ was less than 1 for both adults and children. The HQ of the assessed heavy metals is presented in Figure 5.

The metal concentration levels at all monitoring sites have been above the adherence to safety thresholds, which may be responsible for the increase in anthropogenic and natural impacts due to human activities, particularly at Stations 1 and 2. When compared to results from other studies, the results obtained here were lower. Values in the range from 0.75 to 15.01 mg/l were found in a few northern parts of Pakistan's water sources, whereas agrarian warmer weather in the northern part measured levels around 1.12 and 5.10 mg/l. The element iron (Fe) is essential for the survival of almost all known living things. Iron is a crucial element of protein molecules, enzymatic, and hemoglobin. As a result of its frequent distribution in the natural environment, iron tends to be found at a higher concentration in Pakistan's freshwater ecosystem than other metals. Fe inadequacy, which can cause anemia and fatigue, is most common in children (those under 5 years of age), pregnant women, and people with compromised immune systems (Clark 2008). An excess of iron can also have harmful consequences for the nervous system, whereas the symptomatic iron toxic effects may induce mitochondrial dysfunction due to metal oxidative stress to the genetic material (Jomova & Valko 2011). Several of the evaluated concentration levels of heavy metals were observed to be incredibly high, particularly at Stations 1 and 2, and this could be due to the combined effects of all the human activities occurring in and around Station 1 and the downstream impacts of the effluent from Station 2 upstream outflow. Overall, the levels detected in this research dropped within the earlier assessed range of 0.06–0.51 mg/l (Iqbal & Shah 2015) in the northern region of Pakistan during the spring and early summer. Due to its contribution as a co-factor in various enzyme functions, manganese is an essential trace mineral for all living things (Hüssy et al. 2021). There is a lot of biochemical importance to heavy metals, and it is not harmful at all. Manganese-rich water is the norm instead of the exception in most regions. Manganism is a chronic disorder that occurs if too much manganese is consumed. Zn limits in drinkable water have been linked to children's recognition and behavior problems (Giri & Singh 2015). Manganese deficiency anemia can generate from persistent exposure to excessive amounts of heavy metals because it impedes the body's capacity to absorb the iron from nutrition. As with copper, manganese ingestion decreases the effectiveness of copper metalloenzymes. The intake of too much manganese can lead to hypertension in individuals over the age of 40 years and symptoms emulating Parkinson's disease (Malavolta & Mocchegiani 2018). Particularly at Stations 1 and 2, all recorded concentration levels of Zn were significantly higher than the upper limit expected. It is also feasible that geomorphological factors or human activities are reprimanded. Zn is also essential for healthy animal and human growth and survival. Its compounds or natural complexes can be found in almost all edible and consumable water bodies (Mandal et al. 1998). The growth of bone fragments and the development and function of the reproductive system are some of the infrequent consequences of zinc toxicity. Among the clinical symptoms of zinc toxic effects are digestive problems, dark urine, organ failure, kidney problems, and metabolic disorders (Cummings & Kovacic 2009). Since all of the measured concentration levels of metals were within the original study limit for acceptance, researchers have found no evidence of an issue. Anthropogenic activities could account for the comparatively high value observed at Stations 1 and 2. Concentration levels as low as 0.02 and 0.15 mg/l were evaluated in the spring and summer time in Pakistan, while (Ekere et al. 2014) few drinking sources of water of Northern Pakistan had already evaluated concentration levels of 0.21–2.65 mg/l. The evaluated concentration levels of metals were considerably higher than the permissible level. All these geomorphological and living thing aspects could be in practice, particularly at Stations 1 and 2. Once chromium thresholds in drinkable water are kept within the normal limit, they aid in the maintenance of healthy glucose uptake, trying to make chromium a vital nutrient for human beings. Disease and inflammation of the skin can generate when chromium concentration levels are too high. Stations 1 and 2 specifically had cadmium amounts that have been substantially greater than the recommended peak value, which could be due to human interference. It is not highly essential, but it can still be toxic because it contains impurities (Murphy et al. 2012). Cadmium, even in smaller concentrations, can harm the arteries of the kidneys. Chemically, Cd can substitute for Zn, resulting in higher blood pressure and kidney problems. Also, it induces human immune disease, which is incredibly painful and has consequences from enzyme intervention. High blood pressure, organ failure, and even the advancement of tumors are all possible scenarios of intense Cd toxicity in living beings (Engwa et al. 2019). Ni limits at Stations 1 and 2 have been observed every once in a while to be too high. Numerous distinct varieties of animals, microbes, and plants depend on Ni, and as a consequence, deficit or toxic effects could take place if there was not a sufficient amount of it (Cempel & Nikel 2006). Despite becoming widespread and essential for the mechanism of several living things, nickel's toxic effects could be precipitated by either human activity release or geological formations changing circumstances in the same regions. Those who are exposed to the toxic effects may encounter problems with their breathing and immune function. The majority of individuals are exposed to Ni largely through their nutrition and drinkable water (Puckett 1995).

Iron CDI levels both for adults and children were greater than that of the RfD (0.007 mg/kg/day) when consumed by humans. It is indeed feasible that the pH level of the river appears to contribute to the increased iron CDI value systems by trying to make the river's naturally high mineral content more drinkable. According to Lenntech (n.d.), a reduction in the pH enhances the water solubility from certain metals (Onyele & Anyanwu 2018); in a similar way, both show increased iron concentrations in the CDI. As an outcome, river water could pose a risk to individuals who drink something due to the presence of iron. The CDI amount of heavy metals for an adult was below the oral standard value (RfD) of 0.014 mg/kg/day, whereas that of children surpassed the RfD. Manganese was not regarded as a possible future risk to adults exposed to the water of Kunhar but not to the children. Zinc concentration levels in Kunhar River water were lower than the oral standard value (RfD) (0.3 mg/kg/day) both for children and adults (Muhammad et al. 2021). Živković et al. (2019) recorded lower CDI values for Zn. CDI values of chromium for adults and children were above the oral reference dose (RfD) (0.0003 mg/kg/day). All these natural and anthropogenic factors could contribute to increased cadmium CDI measurements. Consequently, river water containing cadmium may pose a risk for those who drink it. Nickel concentration levels primarily due to ingestion in Station 1 are significantly below the oral standard value (RfD) of 0.02 mg/kg/day for both adults and children.

All the stations had a HQ for metals greater than 1. Each of the stations had much greater iron levels (1), and only Station 1 and the children's concentration of manganese were too greater. All stations had zinc levels below the safe threshold for both adults and children. All these children and adults at all stations had excessively high cadmium amounts, and chromium levels were too high except for adults at Station 1. It was discovered that children were especially vulnerable because of the high HQ values from certain age categories (Mohammadi et al. 2019). Some of the metals perceived in this research also had an HQ value greater than 1. Some of the metals examined in this research had extremely high CDI values, which also likely contributed to the large HQ observed values. Water customers in all impacted stations may be exposed to such metals over a lengthy period. Because of the severity of the measured long-term health threat, the non-carcinogenic negative impact could be ignored as superficial.

All surface water samples gathered from the Kunhar River during the wet and dry seasons were confined to the PCA and correlational analysis (e.g., Pearson and Spearman analysis) to evaluate whether or not there was a correlation between the physical and chemical parameters, essential minerals, toxic substances, and anthropogenic impacts. The PCA identified eight essential aspects, that together took into account 86.67% of the overall variance in the set of data. In total, 75.1% of the variability in parameters of water quality might be clarified by the five fundamental elements that were obtained. Positive maximum load values higher than 0.3 are connected with pH, temperature, BOD5, Cu, Ni, and Zn on the initial singular value (PC1), which helps to explain 28.16% of the overall variability. Organic material and toxic substances (for instance, Cu, Ni, and Zn) in the Kunhar River may well be predominantly polluted by domestic and commercial wastes in the Mansehra district, as shown by the hopeful similarity between the PC1 and many samples taken at the residential and commercial locations. Samples from agrarian and less affected areas were negatively associated, revealing that agricultural practices in the Mansehra district did not result in significant organic material and heavy metal contaminations in the Kunhar River. This may be a result of the fact that the selected sample water was situated in the center of the Mansehra district, where it revealed both industrial effluents and domestic sewage from residential areas. Positive charging values ranging from 0.39 to 0.48 were coupled with conductivity, salinity, and DO on the second principal component, which also took into account 16.95% of the amount of variance. A perfect coefficient between residences and less impacted site specimens recommended that ionic compounds were prevalent in the surface water collected there. Approximately 10 and 7% of the amount of variance of all parameters of water quality were clarified by the constituents. Both residential and commercial wastewater may have an impact on the elements due to their similarity with organic matter and heavy metals.

There might have been an essential assessment of health risks because a few of the toxic substances evaluated were just too intense. There was no single heavy metal found to be a cause of the health risk to the stations, but the combined impact of all of them was fully evident in the HI. So, every station's HI was substantially higher than the threshold of 1. It has serious implications for the health of both children and adults who drink polluted water. To a great extent, anthropogenic activities accelerated naturally produced surface and groundwater sources of contamination with heavy metals. According to the limited working seasons for field involvements in the Himalayas, maintenance of high-altitude areas surrounding the Kunhar River is indeed a massive task for the globe. According to the results, the Kunhar River's water quality is excellent, except for a slightly higher BOD value that can be minimized by preventing the dumping of human-oriented trash around the river or stream. According to the metal concentration in the sediment, sediment particles may act as a drain for metals because it adsorbs particles and carries the largest environmental contamination load. Current quantities of metals in water present no risk to people or aquatic life. Metals in river sediments have been shown to have a minor concentration factor and contamination factor, which might arise with the period if human behaviors along the river are not controlled, which impacts air quality, sanitation and hygiene, and food and nutrition. Predictors of climatic variability effects on water quality and quantity may benefit from our research. As a result of the increased desire for the tourism sector, the land is now under increased stress, increasing the threat of soil degradation, contamination, the destruction of the environmental ecosystems, and the risk to threatened animals. There was also a lot of plastic trash accumulated on the riverbank, which is an increasing environmental danger. These impacts tend to slowly destroy the environmental and social resources that maintain the tourist industry. Climate change has been the major cause of river extinction in the past, so monitoring and management of natural resources are critical to ensure that rivers will not become completely extinct.

It is the author's wish to acknowledge and thank the Pakistan Meteorological Department (PMD) for providing valuable data for this research.

S-e-h.S. conceptualized the study; prepared the methodology; wrote and prepared the original draft; wrote, reviewed, and edited the article. X.S. conceptualized the study, acquired funds, was involved in project administration, collected resources, and supervised the study. J.G. conceptualized the study, acquired funds, wrote, reviewed, and edited the article. C.H. wrote, reviewed, and edited the article. S.J. and H.M.Z. wrote, reviewed, and edited the article, did data curation, and analysed the data.

This work was supported by the Projects of Natural Natural Science Foundation of China (51922065 and 52279069) and the National Natural Science Foundation of China (52179018).

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.