Considering the importance of nutrients in the soil for the plants development and the soil quality conservation and the quantification relevance of them for proper soil management, the aims of this research were: (i) to quantify the clay loss, adsorbed and soluble P from interrill erosion influenced by the presence of sugarcane residues on the ground surface; (ii) to determine the minimum percentage of residues to be maintained on the soil surface to not enrich the eroded sediment by clay and soluble P (Psed) and adsorbed (Pads). The experimental area is located in Guariba -SP, with soil classified as Red Dystrophic Oxisol. The experiment was designed based on results of previous experiments with residue analysis of variance for 40 plots. These experiments were conducted by our research group, which provided field representation and the establishment of a minimum number of degrees of freedom necessary to ensure normal distribution of results and variance homoscedasticity. The experimental design was completely randomized in a factorial design, 5 treatments with straw sugarcane and 3 repetitions, totaling 15 plots. In the treatments, the straw was manually distributed across the surface of the soil in amounts of 0; 0.16; 0.35; 0.52 to 0.7 Kg by plot, giving 0% coverage (SC0), 25% (SC25), 50% (SC50), 75% (SC75) and 100% (SC100), respectively. The experimental plots were subjected to simulated rain with average intensity of 60 mm h -1 for 65 minutes. To avoid enrichment ratio (ER) of the sediment eroded by Psed, Pads and clay, a minimum soil surface coverage (SC) of 42% is necessary.

The ethanol extracted from sugarcane is utilized in various countries in the form of pure fuel as an alternative for fossil fuels. Additionally, it can be employed as an additive for gasoline. As an additive, the anhydrous alcohol is added to gasoline at a concentration of 22% (v/v), forming a "gasohol" solution [1]. The hydrated form of alcohol (96% v/v) is directly employed in automotive vehicles presenting economic and ecological advantages in the form of decrease of petroleum-derivative consumption and absence of a wide group of toxic pollutants emitted during fossil fuel combustion.During the processes of production, transport, and storage of fuel ethanol, some organic and inorganic contaminants can be formed or introduced in this matrix, such as heavy metals, aldehydes, and anions such as chloride and sulfate, which can cause engine corrosion effects and environmental pollution [2]. Some analytical techniques such as spectrometric [3][4][5] and electrochemical [6-8] ones have been used for the study and determination of organic and metallic contaminants in fuel ethanol. However, there are few works on the methodology for dosage of anionic species such as chloride and sulfate in this matrix [2,[9][10][11].Conducting polymers constitute a kind of electrode surface-modifiers for use in solid electrodes. These modified electrodes are generally coated with films containing electroactive species selected according to their properties in terms of speciation for ionic species in solution [12]. In this context, polyaniline (PANI) consists of a polymeric film with good mechanical properties, whose preparation and other properties are reported in the literature [13][14][15]. Electrochemical polymerization is also a widely used method for conducting polymer film formation. This method presents several advantages such as one-step polymerization, thickness control, and low consumption of reagents [16]. In the case of PANI, it is generally accepted that multi-sweep cyclic voltammetry is the most adequate approach to prepare homogeneous conducting films. Interesting properties such as of chemical and mechanical durability have allowed PANI-modified electrodes to be used in flow systems [17,18]. As an example, Ye and Baldwin [17] used a polyaniline-coated platinum electrode with a glycine buffer as the mobile phase for FIA to detect subnanomolar amounts of nitrate and perclorate anions.Despite the advantages of chemically modified electrodes (CME) in the determination of a broad spectrum of anionic species, there are no works in the literature about chloride determination in fuel ethanol. So, the aim of