A review of the characteristics of rainfall simulators in soil erosion research studies.

Rainfall simulators are widely employed in soil erosion studies, and it is common for these simulators to be customized to address specific research questions. Nevertheless, there are certain characteristics that rainfall simulators should fulfill in the context of soil erosion studies. Rainfall simulators should simulate natural precipitation as accurately as possible. It is essential to monitor the size spectrum of generated raindrops, their maximum or terminal velocity, the uniformity of the surface distribution of rain, the kinetic energy and the overall intensity of the rain. This review aims to outline the characteristics and the corresponding measurement methods for rainfall simulators in soil erosion research. Electronic instruments like distrometers are considered more suitable for precise and comprehensive measurements than traditional instroments or literature based derivatives. By adhering to these characteristics, researchers can ensure the reliability and accuracy of their findings. Consequently, this overview serves as a valuable resource for researchers seeking to employ rainfall simulators in their investigations of soil erosion.

Investigating the dispersal of macro- and microplastics on agricultural fields 30 years after sewage sludge application.

Plastic contamination of terrestrial ecosystems and arable soils pose potentially negative impacts on several soil functions. Whereas substantial plastic contamination is now traceable in agro-landscapes, often internal-caused by the application of fertilizers such as sewage sludge, questions remain unanswered concerning what happens to the plastic after incorporation. Based on a combined surface and depth sampling approach, including density separation, fluorescence staining and ATR-FTIR or µFTIR analyses, we quantified macro- and microplastic abundance on two agricultural fields-34 years after the last sewage sludge application. By sub-dividing the study area around sludge application sites, we were able to determine spatial distribution and spreading of plastics. Past sewage sludge application led to a still high density of macroplastics (637.12 items per hectare) on agricultural soil surfaces. Microplastic concentration, measured down to 90 cm depth, ranged from 0.00 to 56.18 particles per kg of dry soil weight. Maximum microplastic concentrations were found in regularly ploughed topsoils. After 34 years without sewage sludge application, macro- and microplastic loads were significantly higher on former application areas, compared to surrounding areas without history of direct sewage application. We found that anthropogenic ploughing was mainly responsible for plastic spread, as opposed to natural transport processes like erosion. Furthermore, small-scale lateral to vertical heterogeneous distribution of macro- and microplastics highlights the need to determine appropriate sampling strategies and the modelling of macro- and microplastic transport in soils.