Future scenarios to understand emissions, fate and transport of chemicals at global to regional scale
Authors:   , Nagesh Poornima 
Published: October 2024

Synthetic chemicals play a crucial role in our modern society but are also significant drivers of global environment and health challenges. The use of chemicals and their diversity has increased in the past decades and is expected to grow further, mostly driven by socio-economic developments. It is, therefore, crucial to understand the possible use of chemicals and related pollution across different spatial and temporal scales under different scenarios for socio-economic development and climate change. This also allows society to formulate effective risk reduction measures, if necessary.
In this context, this thesis explores the use, emissions, fate, and transport of chemicals in the future. We focus specifically on agrochemicals and their transformation products. This analysis is done at the catchment, national, European and global scales using qualitative scenario development and quantitative scenario-based modelling with a time horizon up to the year 2100. The calculations are done using the global integrated assessment model (IMAGE 3.3) to analyse the possible future use and emissions of chemicals and the catchment-specific Zin-AgriTRA model to project spatial and temporal changes in chemical fate and transport.
The scenarios on chemical use and emissions show widely diverging trends both at the European and global scales. Chemical emissions typically decrease in the sustainable scenario (SSP1), following current increasing trends in SSP2 and showing a stronger increase in the regional rivalry scenario (SSP3) for most selected chemicals and chemical groups. The scenarios show that regions like China, South America, Africa, the USA, and South Asia can become global hotspots of agrochemical emissions, with up to a 109% increase in maize and vegetable and fruit-related agrochemical emissions for Africa in SSP3. In contrast, the SSP1 diet scenario shows a reduction in global agrochemical emissions, especially for feed crops like maize (5.6%↘), rice (52.6% ↘), soybeans (23.5% ↘), wheat (18.9% ↘), and other crops (17.8% ↘). The results highlight that transitioning away from a meat-intensive diet and reducing food waste can aid in reduced agrochemical emissions. On a catchment scale, we show that the fate and transport of agrochemicals can also be determined by extreme climate events causing short-term peak river concentrations. In the long term, agrochemicals and their transformation products can accumulate in the environmental compartments. The findings of the thesis (presented as chemical use, emissions, fate, and transport scenarios under global change) can be further used to provide a perspective on the chemical pollution planetary boundary and support future chemical risk assessment and mitigation. Sustainable management of chemicals requires an integrated effort across all sectors, from producers to consumers, through policies, technological advancements, and environmental awareness. Within this complexity, scenario-based modelling is an important tool to evaluate possible mitigation options.