<p>This study evaluates the retention of nitrogen and phosphorus in four newly constructed wetlands in the municipality of Falkenberg, Sweden. The four wetlands have been selected because they have been specifically constructed with the aim to reduce nitrogen and phosphorus in farming areas. The process of selecting the specific wetlands has been done in collaboration with the county administration in Halland.</p><p> </p><p>Through field studies in collaboration with the landowners where the wetlands are sited, the areas that provide the wetlands with water were determined. The size of these drainage areas were determined in a GIS computer program. The type of land use within the drainage areas was also determined. During April 2010, water sampling in the wetlands was done and the water temperature and the flow of water was measured or calculated. Later the water samples were analyzed for containment of nitrogen (N-tot) and phosphorus (P-tot).</p><p> </p><p>An important part of the work was modeling calculation of the load of nutrients that reach the wetlands and the retention of nutrients in the same wetlands. Both simulated values and measured mean values during April 2010 of nitrogen (N-tot) and phosphorus (P-tot) were used in the models. Actual calculations of the nutrient retention during April 2010 were also done based on the flow of water and the concentrations of the nutrients in the in- and outflow of the wetlands. Another important factor that also has been calculated in the models is cost efficiency of nutrient retention in the wetlands. All four evaluated wetlands have been constructed with financial support from the county administration in Halland. The landowners may also receive a yearly benefit for maintaining the function of nutrient retention.</p><p> </p><p>The results of modeling and actual calculations show that the evaluated wetlands can be divided into two groups. In one of the groups the cost of construction has been considerably higher then the other group of wetlands. The first group of wetlands has smaller drainage areas with a lower proportion of cropland than the other group. Larger drainage areas with a higher proportion of cropland provide the wetlands in the second group with a higher flow of water that contains a higher load of nutrients. This means that these wetlands remove higher amounts of nutrients on a yearly basis. The group of evaluated wetlands that have the largest drainage areas with a higher proportion of cropland is also the group of wetlands that had the smallest costs of construction. These wetlands are therefore considerably more efficient in the terms of costs for nutrient retention than the other wetlands.</p><p> </p><p>The conclusions that can be drawn by this evaluation are that the larger drainage area that provide the wetland with water and the higher part of croplands within the same drainage area the better the modeling calculation describe the actual retention of nutrients. Furthermore the conclusion can be drawn that if only a wetlands drainage area is known and the land use within the same drainage area also is known; the retention of nutrients in the wetland can be calculated before the wetland is constructed. If the county administration request for an estimate of construction costs before a decision of financial support and obtains data of the size of the drainage area and land use within the drainage area, it is possible to evaluate the cost efficiency of nitrogen and phosphorus retention in the wetland. From this, wetland projects that should be given a higher priority than other wetland projects could be selected.</p>

This study evaluates the retention of nitrogen and phosphorus in four newly constructed wetlands in the municipality of Falkenberg, Sweden. The four wetlands have been selected because they have been specifically constructed with the aim to reduce nitrogen and phosphorus in farming areas. The process of selecting the specific wetlands has been done in collaboration with the county administration in Halland.   Through field studies in collaboration with the landowners where the wetlands are sited, the areas that provide the wetlands with water were determined. The size of these drainage areas were determined in a GIS computer program. The type of land use within the drainage areas was also determined. During April 2010, water sampling in the wetlands was done and the water temperature and the flow of water was measured or calculated. Later the water samples were analyzed for containment of nitrogen (N-tot) and phosphorus (P-tot).   An important part of the work was modeling calculation of the load of nutrients that reach the wetlands and the retention of nutrients in the same wetlands. Both simulated values and measured mean values during April 2010 of nitrogen (N-tot) and phosphorus (P-tot) were used in the models. Actual calculations of the nutrient retention during April 2010 were also done based on the flow of water and the concentrations of the nutrients in the in- and outflow of the wetlands. Another important factor that also has been calculated in the models is cost efficiency of nutrient retention in the wetlands. All four evaluated wetlands have been constructed with financial support from the county administration in Halland. The landowners may also receive a yearly benefit for maintaining the function of nutrient retention.   The results of modeling and actual calculations show that the evaluated wetlands can be divided into two groups. In one of the groups the cost of construction has been considerably higher then the other group of wetlands. The first group of wetlands has smaller drainage areas with a lower proportion of cropland than the other group. Larger drainage areas with a higher proportion of cropland provide the wetlands in the second group with a higher flow of water that contains a higher load of nutrients. This means that these wetlands remove higher amounts of nutrients on a yearly basis. The group of evaluated wetlands that have the largest drainage areas with a higher proportion of cropland is also the group of wetlands that had the smallest costs of construction. These wetlands are therefore considerably more efficient in the terms of costs for nutrient retention than the other wetlands.   The conclusions that can be drawn by this evaluation are that the larger drainage area that provide the wetland with water and the higher part of croplands within the same drainage area the better the modeling calculation describe the actual retention of nutrients. Furthermore the conclusion can be drawn that if only a wetlands drainage area is known and the land use within the same drainage area also is known; the retention of nutrients in the wetland can be calculated before the wetland is constructed. If the county administration request for an estimate of construction costs before a decision of financial support and obtains data of the size of the drainage area and land use within the drainage area, it is possible to evaluate the cost efficiency of nitrogen and phosphorus retention in the wetland. From this, wetland projects that should be given a higher priority than other wetland projects could be selected.

Mikroplast, här definierat som plastobjekt mindre än 5 mm, befaras kunna göra stor skada på vattenlevande djur. Fram tills idag har studier av mikroplastreduktion främst utförts i kommunala avloppsreningsverk där mycket av plasten avskiljs. De stora spillvattenflödena gör ändå reningsverken till betydande utsläppspunkter av mikroplast till sjöar och hav. Information har hittills till stor del saknats om mikroplastförekomst i dagvatten, vilket ofta släpps ut orenat och i större volymer än spillvatten. Förekomst av mikroplast &gt;20 µm (&gt;0,02 mm) har undersökts för tre tätorters dagvatten samt för två avloppsreningsverks utloppsvatten. Avskiljning av mikroplast har undersökts för två spillvattenvåtmarker och två dagvattendammar. Båda anläggningstyper är relativt billiga och effektiva när det gäller reduktion av tungmetaller och övergödande näringsämnen. Örsundsbro våtmark och våtmark Alhagen tar båda emot behandlat spillvatten från kommunala avloppsreningsverk. I våtmark Alhagen finns även ett inlopp för dagvatten från Nynäshamn. Till dagvattenanläggningen Korsängens vattenpark leds en stor del av Enköpings dagvatten, medan Tibbledammen tar emot det dagvatten som kommer från Kungsängen i Upplands-Bro kommun. Vatten från anläggningarnas inlopp och utlopp, samt från två punkter inuti våtmark Alhagen har pumpats genom 20 µm-filter och 300 µm-filter. Provtagningen har kompletterats med insamling av mindre vattenvolymer som har filtrerats på laboratorium. Kvantifiering av mikroplast har gjorts med hjälp av stereomikroskop och vanligt förekommande objekts material har undersökts genom FTIR-spektroskopi. I våtmark Alhagens inkommande spillvatten var mikroplastkoncentrationen 4 objekt/liter, vilket liknar de koncentrationer andra svenska studier uppmätt i behandlat spillvatten. I inkommande vatten till Örsundsbro våtmark var koncentrationen över 950 objekt/liter, långt över vad andra svenska studier uppmätt i helt obehandlat spillvatten. I dagvatteninloppen var mikroplastinnehållet 5,4–10 objekt/liter, vilket indikerar på att mikroplatsutsläpp via dagvatten kan befaras vara minst lika stora som via spillvatten. I alla anläggningars inkommande vatten, förutom i våtmark Alhagens dagvatteninlopp, uppmättes höga koncentrationer av rödfärgade partiklar. Partiklarna kan vara av plast eller av annat okänt material och är till utseendet relativt lika de som andra studier påträffat i svenska kustvatten. Svarta partiklar påträffades i alla inflöden och ofta i mer än 100 gånger högre halter än de för mikroplast och röda partiklar, förutom i våtmark Alhagens spillvatteninlopp där de röda partiklarna var något fler. Partiklarna tros kunna vara däck- och vägrester eller förbränningspartiklar. Alla anläggningar visade på en tydlig avskiljning, ofta 90-100 %, för mikroplast, svarta och röda partiklar &gt;20 µm. Till följd av resultatet samt anläggningarnas variation i ålder, storlek och utformning bör dagvattendammar och anlagda våtmarker generellt kunna förväntas fungera som effektiva barriärer mot spridning av mikroplast, svarta partiklar och röda partiklar. / Microplastics (MPs), here defined as plastic objects smaller than 5 mm, are suspected to cause great harm to fish when released into lakes and oceans. Studies of MP retention have until recently mainly been done for sewage treatment plants (STPs), where much of the plastics are shown to be retained in the sludge. However, due to large water flows in STPs, they can be seen as significant points for the spreading of MPs to recipient waters. Today there isn’t much information to be found about MP contents in stormwater. Stormwater is often released untreated and depending on climate it can be released in greater volumes than sewage water from urban areas. The occurrence of MPs &gt;20 µm (&gt;0.02 mm) has been studied in two STP effluents, and in stormwater from three urban catchments. The retention of MPs has been studied for two stormwater ponds, and for two free water surface wetlands constructed for tertiary treatment of sewage. Wetland Alhagen and Örsundsbro wetland both receive the effluents of secondary STPs. In wetland Alhagen there is also a stormwater inlet from the town of Nynäshamn. To the stormwater pond Korsängens vattenpark, stormwater is lead from the town of Enköping, while the stormwater pond Tibbledammen receives stormwater from Kungsängen in Upplands-Bro municipality. Influents and effluents from the facilities, as well as water from two points within wetland Alhagen was pumped through 20 µm and 300 µm filters. In addition, water from every sampling point was collected in minor volumes for later filtration carried out in a laboratory. Quantification was done with microscopy and a number of objects were analyzed with FTIR spectroscopy for material determination. In wetland Alhagen, the sewage inlet contained 4 MPs/liter, which is similar to results for STP effluents in other Swedish studies. In Örsundsbro wetland, the incoming water contained more than 950 MPs/liter, far greater than what other studies have shown for untreated sewage. The MP concentrations in the three stormwater inlets were between 5.4-10 MPs/liter. This indicates that untreated stormwater could be seen as a pathway for MPs at least as big as treated sewage. In almost all inlets, characteristic red particles were found in great numbers and in sizes of 20-300 µm. Analysis of some of the red particles indicated that they contained plastic while others were of unknown materials. The particles had a similar appearance to red particles commonly found in Swedish coastal waters. Black particles, a kind of microscopic particles that may originate in tyre wear (i.e. MPs) or combustion, was also found in large quantities. Except for in the main influents of wetland Alhagen, where the number of red particles was slightly higher, the black particles were always found in far greater numbers than both regular MPs and red particles (often &gt;100x greater). The retention of MPs, black particles and red particles &gt;20 µm was high in all the facilities, often around 90-100 percent. Based on these results and the variation of size, design and year of construction, stormwater ponds and constructed free water surface wetlands can be seen as effective barriers against the spreading of MPs.

Inom Rååns avrinningsområde, som är beläget i kommunerna Helsingborg, Landskrona, Svalöv och Bjuv, har anläggning av våtmarker pågått sedan 1990-talet. De anlagda våtmarkerna syftar till att minska näringsförlusterna från omkringliggande jordbruksmarker till vattendrag och gynna den biologiska mångfalden. I denna studie har 28 anlagda våtmarker inom Rååns avrinningsområde studerats. Studien hade två övergripande syften varav det ena var att undersöka sambandet mellan sedimentackumulering och våtmarkernas utformning samt placering i landskapet. Det andra syftet var att undersöka våtmarkernas renoveringsbehov. Renoveringsbehov syftar på åtgärder som behöver utföras för att upprätthålla våtmarkernas ursprungliga funktion och utformning såsom flödesvägar, vegetation, djupprofil samt in- och utlopp. Studien baserades på observationer och mätningar som utfördes i oktober år 2020. Resultatet visade att sedimentackumuleringen varierade mellan 0,2–2,3 cm per år och att både utformnings- och placeringsfaktorer påverkade sedimentackumuleringen. Det uppskattade ursprungliga vattendjupet hade en positiv korrelation med sedimentackumulationen och sedimentdjupet blev högre med våtmarkens ålder. Uppgrundningen var högre närmare inloppet i fyra av sju långsmala våtmarker (Längd-breddförhållande, 𝐿 ∶ 𝐵 &gt; 3). I de långsmala våtmarkerna fanns även en positiv korrelation mellan hydraulisk belastning (HL) och sedimentackumulering. I våtmarker med 𝐿: 𝐵 &lt; 3 fanns en övre gräns där höga värden på HL istället hade en negativ påverkan på sedimentackumuleringen. Våtmarkens storlek i relation till avrinningsområdet hade ett negativt samband med sedimentackumuleringen. Att många faktorer påverkade sedimentackumulationen gjorde att uppgrundningen skedde olika snabbt i våtmarkerna. Därmed kunde inte ett exakt åldersintervall för urgrävning fastställas. Däremot kan urgrävning potentiellt begränsas till början av våtmarker i de fall våtmarken är långsmal med djuphåla vid inloppet. De undersökta våtmarkerna hade varierande grad av renoveringsbehov. Urgrävning bedöms vara den mest resurskrävande åtgärden. Det är dock en nödvändig åtgärd om våtmarkerna ska fortsätta fungera som näringsfällor. Andra renoveringsbehov innefattade exempelvis enklare skötsel av vegetation, reparation av teknisk utrustning såsom rör och brunnar samt uppföljning av avtal med markägare för att se till att våtmarkerna förvaltas på sådant sätt att deras miljönytta gynnas. / Wetlands have been constructed within the catchment area of Råån since the 1990s. Råån is a river flowing through the municipalities Helsingborg, Landskrona, Svalöv, and Bjuv. The constructed wetlands aim to reduce nutrient leakage from surrounding agricultural land and increase biodiversity. In this study 28 constructed wetlands were studied with two aims: (i) to investigate the relationship between sediment accumulation in wetlands and wetland design and location in the landscape and (ii) investigate maintenance needs of the wetlands. Maintenance needs involve taking efforts to restore flow paths, depth profile, vegetation, and inlet and outlet to return the original function and design of the wetland. The study is based on observations and measurements carried out in October 2020. The results showed that sediment accumulation varied between 0.2–2.3 cm per year and that both wetland design and location affected sediment accumulation. Estimated original water depth had a positive correlation with sediment accumulation and sediment depth had a positive correlation with wetland age. The level of shoaling was higher closer to the inlet in four of seven long narrow wetlands (length- width ratio, L: W, &gt; 3). In the long narrow wetlands, there was also a positive correlation between HL and sediment accumulation. However, in shorter and wider wetlands (L: W &lt;3), there was an upper limit where high values of HL instead had a negative effect on sediment accumulation. Wetland area in relation to catchment area had a negative correlation with sediment accumulation. Shoaling rate is different in the wetlands since sediment accumulation is affected by many parameters. Thus, an exact time interval for excavation could not be determined. However, excavation can potentially be limited to the inlet of the wetlands if the wetland is long and narrow with a deep area near the inlet. The result showed that the wetlands had varying degrees of maintenance needs. Excavation is considered to be the most resource-intensive measure. However, excavation is necessary to maintain the function of the wetlands. Other maintenance needs include maintenance of vegetation, repair of technical equipment, and extension and enforcement of contracts with landowners to ensure that the wetlands are managed in such a way that the environmental function of the wetlands are favored.

Eutrophication, a surplus of nutrients, is a problem in aquatic environments and one of the Swedish Environmental Goals is that there should be no eutrophication caused by human activities. Constructed wetlands (CW:s) is a measure that could be implemented to decrease the transport of nutrients to water bodies through retention. To optimize the placement of CW:s, this project aims to understand how different factors affect the retention of P (phosphorus) and N(nitrogen) in constructed CW:s and if there are geographical and seasonal variations in retention. Water samples were collected during three sampling periods from CW:s in Halland, in south-western and Mälardalen in eastern Sweden. The variation in retention of P and N between Halland and Mälardalen and between the different sampling occasions was then investigated. The effect of different factors in the catchment area such as percentage of clay, silt and sand, agricultural land, P-AL (phosphorus extracted with ammonium lactate) in the soil, erosion riskclass and the depth of the CW:s on the retention of P and N was also tested. The TP (total phosphorus) load and retention differed between the CW:s in Halland and Mälardalen. In Mälardalen, the load was slightly higher, and had a higher variation in TP load, which can be related to the differences in erosion risk classes as more easily eroded soils usually release P during periods with a lot of runoff. TP retention deviated more from zero in Mälardalen compared with Halland. The retention of TN (total nitrogen) seemed to be higher during August despite the lower TN load. This could be because during the warmer season, there is more retention of inorganic N through denitrification and plant uptake. Many factors such as soil type, erosion risk class, share of agricultural land and hydraulic load (HL) was found to be positively correlated with the load. However, most of the examined factors in the catchment area showed no correlation with the retention of N or P. The percentage of clay in the area had a negative effect on the retention of TP, which is not coherent with previous studies. This could be because the TP retention was mostly zero or negative, which was thought to be because most of the sampling was during periods with high HL and colder weather, especially in Mälardalen, which may have resulted in poor retention and resuspension of nutrients from the sediments. For TN the only factor which had a correlation was the depth of the CW, which had a negative correlation. / Övergödning, överskott av näringsämnen, är ett problem i vattenmiljöer. Ett av de svenska miljömålen är att det inte ska ske någon övergödning orsakad av människan. Anläggning av våtmarker är en åtgärd som kan vidtas för att minska transporten av näringsämnen till vattendrag genom retention. Anlagda våtmarkers effektivitet beror på olika faktorer såsom jordtyp, markanvändning, utformning och årstid. För att optimera placeringen av anlagda våtmarker, syftar detta projekt till att förstå hur de olika faktorerna påverkar retentionen av fosfor (P) och kväve (N) i anlagda våtmarker och om det finns geografiska och säsongsmässiga variationer i retention. Vattenprover togs vid tre provtagningstillfällen från anlagda våtmarker i Halland, i sydvästra Sverige och Mälardalen i östra Sverige. Variationen i retentionen av P och N mellan Halland och Mälardalen och mellan de olika provtagningstillfällena undersöktes därefter. Effekten på retentionen av olika faktorer i avrinningsområdet såsom andel lera, silt och sand, jordbruksmark, P-AL (fosfor extraherat från jord med ammoniumlaktat) i marken, erosionsriskklass och medeldjupet av de anlagda våtmarkerna på retentionen av P och N undersöktes också.Belastningen och retentionen av TP (totalfosfor) skiljde sig mellan de anlagda våtmarkerna i Mälardalen och Halland. I Mälardalen var belastningen något högre, samt hade högre variation i TP-belastning, vilket kan relateras till skillnaderna i erosionsriskklasser då mer lätteroderade jordarter oftast släpper P under perioder med mycket avrinning. TP retentionen avvek mer från noll i Mälardalen jämfört med Halland. Retentionen av TN (totalkväve) var förhållandevis hög under augusti trots den förhållandevis lägre TN-belastningen jämfört med höst-och vinterprovtagningarna. Detta kan bero på att det under den varmare årstiden skermer retention av oorganiskt kväve genom denitrifikation och växtupptag.Många faktorer såsom jordart, erosionsriskklass, andel jordbruksmark och hydraulisk belastning (HL) var positivt korrelerade med näringsbelastningen. Däremot visade de flesta av de undersökta faktorerna i avrinningsområdet inget samband med retentionen av N eller P. Andelen lera i området hade en negativ effekt på retentionen av TP, vilket inte stämmer överens med tidigare studier. Detta kan bero på att TP-retentionen mestadels var noll eller negativ, vilket ansågs bero på att det mesta av provtagningen skedde under perioder med hög HL, vilket kan ha resulterat i dålig retention och resuspension av P från sediment. Den enda faktorn som var relaterad med TN retentionen var djupet i de anlagda våtmarkerna, som minskade med våtmarkens djup.