# Transport pathway of the Ag+ following artificial precipitation enhancement activities

## TL;DR

This study tracks how silver from artificial rainmaking ends up in water and soil over 16 years, revealing its environmental transport pathway.

## Contribution

The study provides the first long-term data on the environmental transport of silver from artificial precipitation enhancement.

## Key findings

- Silver ion content in precipitation initially increased after APE and then dropped to zero.
- Soil silver content rose by 44% during the flood season compared to non-operation periods.
- Water bodies regulated silver ion levels, showing a 3.3% increase over 16 years due to APE.

## Abstract

Artificial precipitation enhancement (APE) activities have been applied extensively around the world to enhance water resources. However, the transport way of the silver iodide catalyst utilized remains completely unknown. To address this issue, in this study, we monitored the content of silver ions (Ag+) in a water body under the influence of APE for a period of 16 years (2004–2019). Additionally, we monitored the content of silver ions in the multi-period rainfall and soil. Our findings indicate that after the APE operation, the detected silver content in the precipitation initially demonstrated an upward trend and then decreased to 0. Furthermore, we observed that some of the silver ions remained in the air for a period extending from the time of artificial rain till the next rain. The silver ion content in the soil during the flood season was elevated by 44 % in comparison to the non-operation period; the concentration of silver ions in the water body during the operation period was 42.86 % higher than that in the non-operation period. During the long-term study, spanning 16 years, the water body played a leading role in regulating the content of silver ions released by the APE, resulting in an increase in silver ion content by 3.3 %. Our results revealed the presence of silver in the precipitation after the APE operation, indicating that silver iodide initially entered the precipitation after catalysis. Furthermore, upon the comparison of the soil and surface water during the operation period and non-operation period, the silver content during the operation period was observed to be higher than that in the non-operation period, indicating that silver iodide was incorporated into the underlying surface from the precipitation. Therefore, we have concluded that the transport pathway of silver involves its initial entry into precipitation after sowing, subsequently descending with the precipitation to reach the soil and surface water. The findings of this study establish a scale ruler for the impact of increasing global APE activities on the environment, as well as first-hand data for preventing possible future environmental risks.