Analysis of continuous measurements outside The QUARZ Corp, Drag, Tysfjord – report of measurements done in 2014

Summary

Since March 2012, a marine monitoring buoy close to the point of discharge from The QUARZ Corp. at Drag (Tysfjord, Norway) has continuously been measuring pH, turbidity, and oceanographic parameters at 10 and 20 m depth. This report is a presentation and analysis of the data from 2014. This year, as previous years, there is a clear connection between periods of acid washing in the plant and measurements of reduced pH at the buoy. In periods of acid washing, and when the current goes from the point of discharge towards the buoy, a pH reduction of >0.5 occurred 2.3% of the time, and a reduction of >0.75 occurred 0.6% of the time (under typical circumstances, this is equivalent to a pH below 7.4). Regarding turbidity (concentration of particles in the water), the sensor at 20 m was not functioning for most of the year and there was not enough data for analysis. For 10 m depth, we found that in the start of the year, there was a weak increase in turbidity when the current was directed from the point of discharge towards the monitoring buoy. This indicates that the plant's discharges leads to a detectable increase in turbidity. For the rest of the year, the variation of measured turbidity was atypical compared to the expected pattern if particle release from the plant was the cause of increased turbidity; that is, turbidity was neither related to current direction nor to the occurrence of flotation processes. Two periods with conspicuous peaks in turbidity are probably linked to actual episodes of high water flow in rivers and creeks (although this influenced salinity at 10 m in only one of these periods). Other periods of high turbidity measurements are probably artefacts of sensor fouling. The current data shows that in 2014, as in previous years, the current at the monitoring site was mostly directed towards the fjord bottom during wintertime. This indicates a current pattern going inwards on the southern/western side of the fjord and outwards on the northern/eastern side, wholly or partly due to wind directed along the fjord from the southeast. During summer, when there was less wind and usually directed across the fjord, the current was directed inwards and outwards equally often, following the tides.