Eutrophication is a major problem in many parts of the world today. Eutrophication means that more nutrients are added than nature can absorb, which can lead to algal blooms, overgrowth and sometimes even a lack of oxygen at the seabeds. One of the environmental quality goals in Sweden is No eutrophication and this goal is far from being achieved as extensive problems with eutrophication remain. Phosphorus is a substance that plays a significant role in eutrophication. To find out how much phosphorus there is in a watercourse water samples are taken, usually monthly. However, this is too sparse and peaks with higher levels therefore risk being missed and the phosphorus load in the watercourse can thus be underestimated. However, the sampling frequency required to obtain more reliable results is too expensive to carry out as far too many samples would need to be taken. However, there are solutions to this problem. By using high-frequency turbidity measurements with the help of sensors in watercourses the monthly measurements can be supplemented and gaps filled. Turbidity can be used as an indirect measurement of the phosphorus content as there is a connection between turbidity and phosphorus. This report examines the relationship between turbidity and total phosphorus content for seven different watercourses. Relationships are also compared between different seasons and flows for two of the watercourses. In addition, the total phosphorus load of the different watercourses is calculated and a comparison is made between high-frequency turbidity measurements and grab samples to find out if sensors are suitable at the investigated site. For all stations there was a significant relationship between turbidity and the total phosphorus content. The relationship was in some cases different for different seasons and also for different flows. At some of the stations the relationship was improved when the parameters conductivity and TOC (Total organic carbon) were added to the analysis. The phosphorus load on the different watercourses varied with the season in a similar way for each station with a lower load in the summer and a higher one in the winter and spring. When comparing the load calculated on the basis of sensors and the load calculated on the basis of grab samples the sensors sometimes gave a higher value and sometimes a lower value. This indicates that grab samples in some cases may be sufficient while sensors in some cases may be an important complement as the grab samples could give an underestimated total phosphorus content.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-446227 |
| Date | January 2021 |
| Creators | Haglund, Maria |
| Publisher | Uppsala universitet, Institutionen för geovetenskaper |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | UPTEC W, 1401-5765 ; 21036 |
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