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Elevated atmospheric reactive nitrogen (Nr) emissions and the subsequent nitrogen (N) deposition have negatively impacted the global environment, particularly in China. In order to assess the long-term trends in atmospheric N deposition in the south of China, Taojiang County in Hunan Province was selected as a representative rural area for study. We analyzed interannual variation in atmospheric Nr, including gaseous ammonia (NH3), nitrogen dioxide (NO2), nitrate acid (HNO3) vapor, particulate ammonium (NH4+), and nitrate (NO3−) in air and NH4+-N and NO3−-N in precipitation from 2011 to 2020. The 10-year average atmospheric wet-plus-dry N deposition was 41.9 kg N ha−1 yr−1, which decreased by approximately 24% after 2012, indicating that NH3 and NOx emissions were effectively reduced by emission controls introduced in 2013. Wet deposition accounted for approximately 74% of the total N deposition and was significantly influenced by annual precipitation amount. Reduced N (NH3, pNH4+, and NH4+ in rainwater) was the dominant form, comprising approximately 58% of the total N deposition, while oxidized N (pNO3−, NO2, HNO3, and NO3− in rainwater) accounted for 42% of the total N deposition. Atmospheric HNO3, NO2, and NH3 concentrations and deposition declined by 30–80% over the decade, while particulate NH4+ and NO3− concentrations and deposition remained at relatively stable levels, which suggests that ongoing research and policy should focus on rural particulate pollution. Future strategies must concentrate on the integrated control of NH3 and NOx emissions to mitigate air pollution and protect human health, particularly in rural areas because current abatement efforts are primarily directed toward urban areas and the industrial sector, whereas non-point source NH3 pollution, influenced mainly by agricultural activities, dominates in rural regions. [ABSTRACT FROM AUTHOR]

When the production or use of a product imposes a cost or benefit on a third party, this is referred to as an externality. Externalities of pesticides are associated with social and environmental costs. However, there is still a lack of a systematic method for evaluating and internalizing the externalities of pesticides. This study utilizes the pesticide's environmental impact quotient and environmental accounting methods to assess the external costs associated with pesticide usage in the winter-wheat–summer-maize cropping system in China's northern plains, with a specific focus on the pesticide use in Botou City during the year 2020 as a case study. Additionally, we introduce the concept of the net external value of pesticides and propose a methodology for its internalization, aiming to quantify the external costs induced by pesticide usage and explore the possibility of integrating them into market transactions. The results showed that the total external costs of pesticide use are 423.9 USD ha−1, with a positive external value of 171.9 USD ha−1 and a net external value of −252.0 USD ha−1. The negative external costs associated with pesticide use outweigh the positive external values. External costs varied significantly according to environmental receptors, after retaining two significant figures: applicators accounted for 45% of the total external costs, followed by pickers (32%), consumers (11%), groundwater (4.5%), fish (3.9%), beneficial insects (1.7%), birds (1.3%), and bees (1.1%). The external costs of maize cultivation were 33% higher than those of wheat cultivation. The application of herbicides resulted in the highest external costs compared with fungicides and insecticides. Based on the internalization of the results, imposing an ecological tax on pesticide users is recommended, with rates of 3.29% for wheat and 6.76% for maize. This research contributes to sustainable agricultural development by providing valuable insights for farmers in selecting environmentally friendly pesticides and informing the implementation of ecological taxes on pesticide usage. [ABSTRACT FROM AUTHOR]