Investigation of agricultural soils in Diyarbakir province in terms of humic acid and association with heavy metals

In this study, the humic acid contents of some (n: 118) agricultural soils in Diyarbakır Region were determined by suitable methods and some of these soil samples were determined as heavy metals (Al, As, Ba, Be, Cd, Fe, Mn, Pb, Sb, Sn, Se, V, P) concentrations were determined by ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry) method. The obtained results were evaluated with multivariate statistical methods. SRM 2586 NIST, CRM-SOIL-A Standard Reference Materials (SRM) were used for the accuracy of the methods The dissolving of the soil was done by three different dissolving processes. According to this, Al, P and Ba were well dissolved according to the method of classic Aqua regia, Be, Fe, Mn, and Cd according to the method of microwave Aqua regia and HF burning, As, Pb, Sb, Se, Sn and V according to microwave burning methods according to SRM contents. Analysis of the elements by ICP-OES showed recovery values of 91.6% to 105.9%. For the accuracy of humic acid analysis Humic acid sodium salt was used and obtained result was close to the content of the material.The mean, minimum and maximum values of the humic acid contents of the soil samples were 0.221, 0.040 and 2.340, respectively (%). The CV (Coefficient of Variation) value was found as 143.63% and the value of which is much variation in terms of the locations between the humic acid was found to be quite different. In Factor (PCA) and hierarchical clustering (HCA) analysis, HA and P were in the same group. There was no significant difference in the ANOVA (Analysis of Variance) regarding the HA averages between the regions. According to the Stepwise method, multiple regression analysis showed that when HA was the dependent variable, significant regression model with Mn and P (P <0.01). In simple linear regression analysis, when HA was independent variable, significant regression models were observed with some other variables (P <0.01,P <0.05). According to Pearson correlation, HA was significant positive with As (r = -0.282, P <0.01), significant positive with Fe (r = 0.185, P <0.05) (r = 0.242, P <0.05), significant positive with Se (r = 0.325, P <0.05) and significant positive correlation with P (r = 0.315, P <0.01). When we compare the element concentrations in the humic fraction to the element concentrations in the soil fraction, we were seen the status of elements are attached to HA and the order is As >P> V> Sn> Be> Se> Ba> Ca> Al> Fe> Mg> Sb> Mn> Pb> Cd. It has been understood that the territories in the region are poor in terms of HA and that the lands should be further enriched.