Elevated food demand and population burst have influenced the global N cycle. This has further led to over production of reactive nitrogen since the times when Haber’s Bosch succeeded to produce ammonia artificially (Erisman et al., 2008; Fowler et al., 2013). Nitrogen plays a crucial role in biogeochemical cycle impacting ecological environment (Schlesinger et al., 2013; Vitousek et al., 1997; Galloway et al., 2004). Ecosystem productivity is impacted by the quantity of reactive nitrogen (reactive N) in the environment, in addition to various nutrients ranging from iron, phosphorus, and silica (Mills et al., 2004). Consequently, the carbon cycle, specifically the elimination of carbon dioxide (CO2) from the atmosphere by terrestrial and marine ecosystems, and the food production are associated with nitrogen availability (Duce et al. 1983; Galloway et al. 2008). Reactive nitrogen deposition (wet or dry) may benefit ecological systems by providing fertilizer or degrade them because of the acidification and buildup of extra nutrients (Driscoll et al., 2003).
Through a variety of human-induced (such as industry, transportation, and domestic wood burning) and natural (such as soils, thunder and lightning, plants, microbes, and viruses) sources reactive nitrogen compounds get released into the environment as its oxidized or reduced inorganic (IN) or organic (ON) forms (Neff et al. 2002; Dentener et al. 2006; Galloway et al. 2008). Reactive nitrogen (Nr) species play an important role in atmospheric chemistry. The abundance of nitrogen oxides determines the ozone levels, apart from contributions in acid precipitation. The predominant neutralizing gas for the acidic compounds is NH3. The nitric acid ranks second behind sulfuric acid as a major contributor to atmospheric acidity (Seinfeld and Pandis 2016). As a consequence, atmospheric chemistry is also affected by the scavenging of Nr species by the wet deposition.
Furthermore, quantifying past and future changes in atmospheric deposition of Nr, DOC and metals is necessary to assess the influence of N emissions on both the climate and the ecosystem (Kanakidou et al., 2016). If we look at the global scenarios, Latin America distinguishes apart as the part of the world with the greatest supplies of Nr by naturally occurring biological nitrogen fixation (BNF), which is equivalent to 25% of the world's Nr produced in terrestrial ecosystems (Galloway et al (2004). Although it was 5 times less than whatever occurs naturally in Latin America, the Nr production by BNF in cultivated plants that fix nitrogen (C-BNF) in 1995 was nevertheless equal to 16% of the global C-BNF. On the contrary, just 6% of the world's nitrogen emissions in 1995 originated from the combustion of fossil fuels, and only 4% of the world's nitrogen emissions were contributed from manmade N fertilizer (Galloway et al., 2004). In Indian scenario, fertilizer-N consumption grew from 1970 to 2010 by almost 11 times, contrasted to 3 times rise in crop uptake and a fourfold rise in reactive N (Nr) loss (Raghuram et al., 2020). Crop cultivation also provides N inputs through biological N-fixation (BNF), in addition to N-fertilizer. Based on a conservative assessment of BNF in Indian agriculture, grains provide 32% and grain legumes contribute 43%, comprising 5.20–5.76 Tg N, or around 9.5–10.6% of the worldwide agricultural BNF.
Additionally, as the demands of society for energy and transportation have grown due to economic development, Nr biased balance has become even more pronounced. Given the enormous assistance burden on the nation's the government's finances for fertilizer-N and the additional environmental burden, the urgency to consider the usefulness of the Nr challenge for India appears to be more of an economic nature. A comprehensive investigation to understand reactive nitrogen potential sources and provide mitigation to combat the associated issues that's beneficial to everyone (Abrol et al., 2017).
Wet deposition process is one of the main mechanisms for scavenging of pollutants from the atmospheric (Andreae and Rosenfeld, 2008; Guo et al., 2015; Pan and Wang, 2015; Charlson and Rodhe, 1982; Kulshrestha, 2013). There has been a great deal of research conducted on the atmospheric wet deposition of pollutants including heavy Nr species, carbonaceous species and metals (Singh et al., 2017; Kawamura et al., 2015; Pentalaki et al., 2018; Cheng et al., 2010; Katoch et al., 2023). The findings have implied that a wide range of variables, including the quantity of rainfall, local emission levels, and long-distance transportation of pollutants, have an influence on the concentrations and fluxes of different pollutants (Rodhe et al, 2002; Kim et al., 2000; Theodosi et al., 2010; Cong et al., 2010; Vuai and Tokuyama, 2011; Connan et al., 2013; Montoya- Mayor et al., 2013; Granet et al., 2002). In spite of the mixing effects from several anthropogenic activities and natural sources, the origins of the trace elements in atmospheric wet deposition are exceedingly complicated (Vuai and Tokuyama, 2011; Montoya- Mayor et al., 2013; Hara and Akimoto, 1993). It has been reported that the biogeochemical processes that govern the movement of these elements would be profoundly impacted by atmospheric wet deposition of trace elements, and the dual ecological consequences (nutrient and toxicity) on aquatic life could potentially have a negative influence on human health (Xing et al., 2017).