Bottom sediments of two small shallow dam reservoirs, the Zalew Zemborzycki (ZZ) on the Bystrzyca River near Lublin and Brody Iłżeckie (BI) on the Kamienna River, were investigated. The sediment samples from both water reservoirs were collected at 17 sampling sites in the transects perpendicular to the shoreline, at the river inflow and at the frontal dam. The contents of total nitrogen (TN) and total phosphorus (TP) were mea- sured and the research results analyzed statistically. A relationship between TP concentration in sediments and TN, Fe, and Al levels was determined. The maps of spatial distribution of TN and TP were drawn.
Sediments of the BI showed greater differentiation of TN and TP contents than sediments in the ZZ, which resulted from a sediment dredging operation performed in most of its area. The dredged part of the BI reservoir had many times lower levels of both TN and TP as compared to sediments in the undredged part. In the ZZ reservoir sediments, longitudinal zonation of TN spatial distribution was observed: the lowest content in the sediments in left-bank part of the reservoir, medium along the middle part, the highest in the right-bank area. In this water reservoir, the zone of the highest TP accumulation occurred in sediments of the upper part and at the frontal dam. It is likely to be caused by the high external loads of P from the Bystrzyca River and by its sedimentation process along with silt and clay particles, respectively. The TN and TP distribution in sedi- ments in the BI was similar and displayed transverse zonation (parallel to the dam). Our research established a strong linear relationship between TP content and Fe and Al concentrations in BI sediments. It implies that a high level of Fe and Al in sediments of this reservoir contributed to the TP accumulation there.