Monitoring the impact of fertilizers on soil leachates using sequential injection analysis for multiparametric determination

Forest fires are one of the most common environmental disasters in the Iberian Peninsula, with incidences increasing every year. In just two decades, the probability of a fire year in Portugal burning 100,000 hectares has increased from 30% to 61%, and the risk of a fire year burning over 500,000 hectares is expected to grow over the next decade [1]. The high temperatures that occur during these events seem to deeply affect the soil’s physical properties, including soil permeability [2]. These changes may, therefore, affect the leaching of nutrients and other compounds. The lack of nutrients in the soil in many geographic regions has led to an increased usage of fertilizers during the last decade. Excessive use of nitrogen fertilizers can lead to the contamination of the soil and, consequently, compounds can reach groundwaters through leaching, with potential environmental and agricultural consequences [3]. For these reasons, it has become a necessity to monitor the soil/water interface. This work aimed to set up and monitor laboratory scale soil columns (LSSCs) using flow analysis methods for assessing nutrient and pH levels and characterizing soil leachates from both indigenous and burned soil. A flow analysis method was developed to determine calcium and magnesium concentrations (given these metal ions are common parameters in water analysis) and iron concentrations (since inorganic fertilizers are commonly supplemented with this metal ion), overcoming the disadvantages of conventional methods in terms of time consumption, waste production and cost. The LSSCs were set up with burned and indigenous soil cores from the same sampling site. Leachates were obtained through rain simulations with rain water and rain water with the addition of inorganic fertilizer.