Regional Synthetic Water Pollutants Embodied in Trade and Policy Simulations for Mitigating Pollutant Discharge in China

Abstract

Inter-regional trade in commodities causes the flow of water pollutants, referred to as virtual pollutant transfer. However, existing studies usually focus on a single water pollutant and cannot characterize the integrated discharge of multiple ones. As a result, it is impossible to analyze the integrated virtual flow of multiple water pollutants among regions, much less simulate the effects of possible water pollutant reduction scenarios. To this end, we empirically synthesize several water pollutant indicators as a whole and then make it the occupancy in the framework of input–output analysis, which helps us to quantify the virtual transfer of water pollutants and simulate scenarios’ mitigating effects. The constructed indicator is called the synthetic water pollutant (SWP) discharge index. By accounting for SWP and then its virtual flows based on the compiled multi-regional input–output tables, we analyze the temporal and spatial differences in synthetic net virtual transfer of regional multiple water pollutants occurring with inter-regional trade. The results show that the national SWP discharge scale of six water pollutants (chemical oxygen demand, ammonia nitrogen, total nitrogen, total phosphorus, petroleum, and volatile phenol) is falling from 2012 to 2020. The net intake of virtual pollutants has become more concentrated. Central (e.g., Shanxi and Hunan) and western (Xinjiang, Inner Mongolia) China are the central regions of net virtual receiving. The simulation results show that reducing 10% of importing regions’ inputs while cutting 10% of exporting regions’ consumption mitigates the SWP discharge of the entire economic system by 3.45%. The decrease rate is 3.02%, increasing international imports by 10% in all regions. An incremental SWP reduction of 2.75% by reducing SWP discharge per output unit by 10% in the top 10 regions of discharge intensity indicates reducing the SWP discharge intensity is the most direct and effective approach. However, the growth of fixed asset investment in wastewater treatment and its recycling seems to contribute little to achieving China’s policy target of wastewater treatment capacity increase by 2025. This study provides regional results for managing water pollutants in China and a basis for future policymaking.