## 4 Discussion
### Black Carbon  
The in-situ observations of BC concentrations in precipitation, river water, and in the air from the HKH over three glaciers were the focus of this research. Results demonstrate that average BC concentrations in the air were lower than those reported for Indian and Nepalese sites [31]. In the 2017-2018 seasons, BC in the air from the glaciers at HKHwas summarized in Figure 7. The highest BC levels were observed in summer (May) and the results were consistent with [PERSON] et al. [41], while the lowest was recorded in September. It was consistently low from February to May. According to [PERSON] et al. [42], BC concentrations can be boosted by closeness to sources as well as melting, which lowers WSA. Due to variances in BC emissions or depositions, BC concentrations in the southeastern HKH glaciers were almost equivalent to those in the Tibet Plateau (TP) but were lower than those in Tien Shan and the northern TP [43; 44]. In general, BC values in the high mountains of Asia are significantly greater than as compared with northern Greenland surface snow [45], alpine [46], and arctic [47] ice cores. The amount of black carbon in the atmosphere varies throughout the year, directly altering the absorbance of solar radiation [48]. At Passu (Karakoram), BC concentrations were calculated as 2.39 \(\upmu\)g/m\({}^{3}\) in winter, 3.34 \(\upmu\)g/m\({}^{3}\) in spring, 2.48 \(\upmu\)g/m\({}^{3}\) in summer, and 1.05 \(\upmu\)g/m\({}^{3}\) in autumn. At Raikot (Himalaya) it was 1.97 \(\upmu\)g/m\({}^{3}\) in winter, 4.41 \(\upmu\)g/m\({}^{3}\) in spring, 4.45 \(\upmu\)g/m\({}^{3}\) in summer, and 2.55 \(\upmu\)g/m\({}^{3}\) in autumn. At Meragram (Hindukush) BC values were 1.86 \(\upmu\)g/m\({}^{3}\) in winter, 4.24 \(\upmu\)g/m\({}^{3}\) in spring, 3.49 \(\upmu\)g/m\({}^{3}\) in summer, and 1.57 \(\upmu\)g/m\({}^{3}\) in autumn. The WSA pattern at the HKH glaciers shows an increasing trend from November to January (mean albedo: 0.040), then stays relatively constant in spring (0.051) before rising again in June, July, and August (0.055) and declining in autumn (0.051). Cloud cover can also influence how much solar radiation a planet absorbs and how much sunlight it receives on its surface. In general, more cloud cover correlates with higher albedo and reduced solar energy absorption, as seen in the summer months, although BC concentration was rather high. Cloud cover has a significant impact on the Earth's energy budget, accounting for around half of total albedo [49; 50]. Although WSA has a slightly inverse association with BC concentrations at HKH (Figure 6d), higher WSA was attributed to a larger proportion of cloud cover presence on sampling dates throughout the summer months. These BC concentrations in the air were later deposited on glacier surfaces (either on ice or snow). As the BC concentration rises, it absorbs more sunlight and diminishes WSA, causing the surface of glaciers to warm. The findings suggest that the amount of BC in the air at HKH glaciers is likely to be loffed and then deposited, darkening the glacier surfaces, as has been observed at TP and Himalayan glaciers in the vicinity [8; 51]. The results of the numerous studies are not always directly comparable due to differences in analytical methodology, sampling dates, and snow conditions. Nonetheless, these studies show a significant variety of BC concentrations across glaciers and localities. Similarly, many other studies such as [PERSON] et al. [52]; [PERSON] et al. [49]; [PERSON] et al. [53] observed that the average snow albedo loss induced by BC at glaciers ranged between 0.27 and 23 percent for the combined effect and were equivalent but recognized as low relevance to diminish the albedo at glaciers. The amount of black carbon particles in the air varies with precipitation (rain and snow), which is subsequently deposited in ice, reducing snow albedo and influencing melting. Soot produced by incomplete combustion of fossil fuels, biofuels, and biomass is known as black carbon.