Sediment quality assessment in Latvia water bodies

Statistical examination of minor (l%-10 mg /g) and micro (<; 10mg /g) elements in lake, well and harbour sediments has been done. The tested element concentrations in lake and well sediments are less than their mean concentrations of the world´s sediments in 95% confidence level using assessment criteria c_i > s_ci×t_1-p/2(n) + C_bi (where s_ci - standard error of the mean, t_1-p/2 - Student distribution quantile, p - confidence level, and n - observations). The negative calculated geoaccumulation indexes (I_geo) testify unpolluted character of lake and well sediments in respect to Ni, Cr, V, Co, Br, Rb, Ba, Mn, Zn, Se, Zr, Ce, La, Nd, Lu, Tb, Eu, Sb, Yb, Cs, Sm, Sc, Hf, As, Gd, Ta, Th, and U. Contamination of well sediments with Cu and Sn characterises the following geoaccumulation index values - I_geo= 2.5 (Cu) and I_geo= 2.6 (Sn). The highest I_geo values were obtained for Cd (I_geo = 4.3) and Pb (I_geo = 4.6) in Liepaja military and for Cd (I_geo = 4.0) in Riga harbour. The maximum pollution load index (PLI) values were observed for sediment contamination of Liepaja military harbour (PLI - 5.0) and Riga harbour (PLI - 4.5).