Improving trace element measurement accuracy: Lysimeter cleaning and material effects

Lysimeters are widely used to collect soil solutions with minimal disruption to the natural distribution of trace elements (TEs); however, sorption and release of TEs to and from lysimeter materials can introduce significant errors at trace concentrations. This study reports optimized cleaning protocols and evaluates TE sorption and release from three commonly used tension lysimeters: Rhizon MOM, SPE20 nylon, and SiC20. Cleaning involved sequential rinsing with acids and ultrapure water (UPW), followed by soaking and sonication in UPW. The sorption and release behaviors of lysimeters were evaluated before and after cleaning using soil leachate. Rhizon lysimeters cleaned more quickly than others due to lower residual TE concentrations. Blanks from Rhizon and SPE20 nylon lysimeters after cleaning generally showed low TE concentrations (1-100 ng L^-1), except for Al, Fe, and Zn (>100 ng L^-1), and Tl and Th (<1 ng L^-1; Th <5 ng L^-1 in nylon), demonstrating the effectiveness of cleaning protocols. In contrast, SiC lysimeters released high concentrations of Al, V, Fe, Ni, Zn, and Sr (>1 µg L^-1) even after cleaning, and showed significant sorption and release of Al, Ag, Ba, Cd, Cs, Cu, Fe, Mn, Tl, V, and Zn. These results provide crucial information to assist researchers in selecting the right lysimeter and cleaning protocols depending on research objectives and desired detection limits.