Utvärdering av Tväråns vattenkemi : Källor för metaller och organiska ämnen

Sammanfattning: Tvärån is an urban stream close to the center of Umeå that serve as a recipient of contaminants from various industries. Therefore, the county administrative board (Länsstyrelsen) in Västerbotten were interested in a compilation of water chemistry data from earlier studies done in Tvärån. In this study, I synthesize available information regarding Tväråns water chemistry as well as review potential emissions from the surrounding industries. Upstream samples were used as background references to deduce where in Tvärån and Klockarbäcken water was affected by industrial inputs of metals. The result from my study shows higher concentrations of all metals in water from Klockarbäcken, with the exception for arsenic (As). Leakage from acid sulfate soils can explain the concentrations of nickel (Ni), zink (Zn), and cadmium (Cd), while sources for lead (Pb) was assumed to come from the industrial area and a large road (E12). From Västerslätt industrial area all recently analyzed metal concentrations were higher in one stormwater outlet except for the elements As and Ni. The higher concentrations are likely explained by diffuse contamination from the local industries together with low pH. Organic contaminants (PAH, PCB, PFAS and Terbutryn) exceeded the detection limit downstream Tvärån, PAH and PCB had obvious upstream sources. As exceeded the Swedish environmental quality standards both up- and downstream the industrial area as well as in Klockarbäcken while Zn exceeded downstream and Klockarbäcken, Ni and Cd only in Klockarbäcken and bens(a)pyren only downstream. In conclusion, the higher concentrations of metals occurred in Klockarbäcken with the elevated levels continued downstream Tvärån where industrial activities also have had an impact on the metal and organic pollutant concentrations.