Characteristics of suspended matter in the River Sava watershed, Slovenia

A combination of C/N ratios, delta C-13 and delta N-15 values in suspended matter was used to examine the seasonal (late summer 2004 and spring 2005) relationship with hydrological characteristics of the River Sava watershed in Slovenia. The values of C/N ratios range from 1.2 to 19.1, delta C-13 values range from -29.2 to -23.0 parts per thousand and delta N-15 values from 0.5 to 16.7 parts per thousand and indicate that the samples are a mixture of two end members: modern soils and plant litter. A simple mixing model was used to indicate that soil organic carbon prevails over plant litter and contributes more than 50% of suspended material. The calculated annual particulate organic carbon flux is estimated as 5.2 x 10(10) g C/year, the annual particulate nitrogen flux 8.5 x 10(9) g N/year and the total suspended solid flux is estimated to be 1.3 x 10(12) g/year. Anthropogenic impact was detected only in a tributary stream of the River Sava, which is located in an agriculture-industrial area and is reflected in higher delta N-15 values in suspended matter and high nitrate concentrations in the late summer season.