Application of mixed‐effects modelling and rule‐based models to explain copper variation in soil profiles of southern Germany

Copper (Cu) is an essential element for plants and microorganisms at larger concentrations a toxic pollutant. A number of factors controlling Cu dynamics have been reported, but information on quantitative relationships scarce. We aimed to (i) quantitatively describe predict soil (CuAR) in aqua regia considering site-specific effects pH, organic carbon (SOC) cation exchange capacity (CEC), (ii) study the suitability mixed-effects modelling rule-based models analysis long-term monitoring data. Thirteen uncontaminated profiles southern Germany were analysed. Since there was no measurable trend increasing CuAR with time respective depth ranges sites, data from different sampling dates combined horizon-specific regression analyses including model simplifications carried out 10 horizons. Fixed- site as random effect useful horizons significant contributions (either main or interactions) SOC, CEC pH present 9, 8 7 horizons, respectively. Horizon-specific cubist described similarly well. Validations successful given population after splitting into calibration validation samples, not independent validations according sites. Overall, site, CEC, SOC provide important description using approaches. Highlights Information scarce Site, closed sites