Abstract

The Northern Dvina River is the main source of water and riverine suspended matter supply of the White Sea. The most part of suspended particulate matter (SPM) and particulate organic carbon (POC) is delivered to the White Sea during floods. In our study we use results of our expeditions in 1997–2006 and the data set of Arkhangelsk Center for Hydrometeorology and Monitoring of the Environment. In the Maimaksa Branch of Northern Dvina delta from the Solombala Island to Lapominka the highest concentrations of SPM in the surface layer are recorded during the spring flood: in May 2005 they were 16.52 mg/l on average, in May 2004 – 10.2 mg/l on average. The SPM concentrations in Maimaksa are much lower in low water seasons. In the mixing zone the concentrations of SPM sharply decrease with the increase of salinity. In the marginal filter of Northern Dvina the following processes sequentially change each other on the way from the river to the sea: gravitational sedimentation, physical-chemical processes (coagulation and flocculation), and, finally, biological processes (growth of phytoplankton with conversion of dissolved elements to biogenic suspended matter and the process of biofiltration). In the delta–sea intermediate zone the distribution of temperature, salinity and SPM are influenced by tides. During the maximal tide thermo- and haloclynes are pronounced, SPM concentration decreases under the picnoclyne. During the ebb all water column is gomogeneously mixed, values of temperature, salinity and turbidity are constant with the increasing the depth. Some anomalous values of SPM concentration were registered near the ship routes after ship passing.

Keywords: suspended particulate matter, Northern Dvina, White Sea, marginal filter