23 research outputs found
Analys och riskbedömning för kemiska variabler som styr oorganiskt aluminium i ytvatten
Modellverktyget Àr robust och kan anvÀndas för bedömningen av Ali halter. En empirisk funktion för skattning av Ali som framtogs tidigare kan dÀremot inte anvÀndas.
Fluoridkomplexen dominerar Ali inom pH intervallet 5 till 6.5. Modellering kan förklara den kemiska variationen och sĂ€rskilt effekter pĂ„ Ali vid höga fluoridhalter (> 10 ÎŒekv/l = ca 0.2 ppm). I omrĂ„den med lĂ„ga halter av humus (TOC 30 ppb) bör fluorid alltid bestĂ€mmas.
BÄde alkalinitet och pH kan anvÀndas som första mÄtt för risk av höga halter av Ali. En nÄgorlunda skarp grÀns mellan höga (> 30 ppb) och lÄga (< 30 ppb) halter av Ali observeras om alkalinitet Àr under 0.025 mekv/l. En mindre skarp grÀns observeras nÀr pH sjunker under pH 5.6.
I omrÄden med naturlig höga humushalter (TOC > 15 mg/l) i kombination med naturlig lÄga pH (pH 60 ppb) förekomma.
Höga halter av Ali (nĂ€ra till 30 ppb) kan Ă€ven upptrĂ€da nĂ€r pH Ă€r över 6. Detta observerades sĂ€rskilt i kalkade eller omrĂ„den som kalkades tidigare. Ăven Altot vĂ€rden högre, det Ă€r oklart om dessa högre Ali vĂ€rden Ă€r ekologiskt betydelsefulla.
Skillnader i anpassningen av Ali och AliMOD i sjöar och vattendrag tyder pÄ att sjöar har en stabilare vattenkemi. I sjöarna kan stabila organiska komplex bildas samt att vissa sjöar verka stÄr i jÀmvikt med en fastfas Àven nÀr pH Àr under 6.
Altot kan skattas frÄn pH och filtrerad abs (absF_420nm/5cm alternativt fÀrg) om pH Àr över 5.5. Denna ekvation kan anvÀndas för att jÀmföra Altot bÄde i naturlig sura och försurade omrÄden. Halter av Ali kan sedan skattas med hjÀlp av grafiska hjÀlpmedel eller genom kemisk jÀmviktsmodellering. Vid lÀgre pH styr andra processer och en enkel och lineÀr skattning via bara pH och abs av Altot Àr inte möjligt.
I ett antal omrÄden finns det tydliga samband mellan fluorid och Na vilket gör det möjligt att skatta vÀrden för F nÀr man bara har tillgÄng till vÀrden för natrium.
En del omrÄden avviker tydlig. Detta beror förmodligen pÄ att vattendragen inte nÄtt jÀmviktslÀge för Ali och/eller att Ali kan pÄverkas av havssalt.
Halterna Altot frĂ„n âKalkslutâ och âKalkintensivâ Ă€r i genomsnitt systematisk högre Ă€n i âRefintensivâ nĂ€r pH Ă€r över 5.5. Ăven vid samma kemiska förhĂ„llanden med avseendet pĂ„ pH och TOC verkar försurade vatten har systematiskt högre Altot. Detta tyder pĂ„ att försurningen har vittrat Al frĂ„n marken. Till följd av detta Ă€r Ali vĂ€rden högre efter kalkavslut
Toxicity of Inorganic Aluminium in Humic Streams
Aluminium (Al) has been recognised as a main toxic factor alongside pH in acidified water ecosystems. The toxic effect of Al has been attributed to inorganic Al (Ali), though there are few in situ studies in ambient humic waters which are the focus of this thesis. The aim was to estimate Ali toxicity and thus also Ali concentrations in Swedish humic streams. Subsequently it is necessary to analyse Ali correctly, which was studied by modelling and method intercalibrations. The hypothesis was that the effect of Ali could be followed via physiological effects and Al accumulation, as well as by mortality. Toxicity was studied by in stream exposures of brown trout (Salmo trutta L.) and two salmonid prey organisms (Gammarus pulex and Baetis rhodani) during spring flood. The modelling of the Ali fraction was performed using monitoring data covering all of Sweden with satisfactory results. The essential variables for Ali modelling were determined; Al, DOC, pH and F, while Fe, Ca and Mg had less effect. The automated analytical procedure for Ali (with cation exchange followed by complexation with pyrocatechol violet) was modified and validated and showed to be the preferred method for laboratory analyses. To avoid detrimental effects for brown trout Ali should be <20 ”g/L and pH >5.0; mortality was high when the Ali was above 50 ”g/L. The invertebrates were more sensitive, as mortalities occurred at pH <6.0 and Ali >15 ”g/L for G. pulex, and at pH <5.7 and Ali >20 ”g/L for B. rhodani. It is prudent to use a wide view and let the most sensitive species set the tolerance limits; a pH above 5.7-6.0 and Ali below 15-20 ”g/L allows the stream ecosystems to thrive. Today, as waters are recovering from acidification, the aim of mitigating liming is to carefully adjust dosage to avoid suboptimal water quality. The thresholds found in this thesis can be used to efficiently but carefully decrease liming, as both Ali and pH levels have to be balanced to sustain the recovering aquatic biota
Toxicity of Inorganic Aluminium in Humic Streams
Aluminium (Al) has been recognised as a main toxic factor alongside pH in acidified water ecosystems. The toxic effect of Al has been attributed to inorganic Al (Ali), though there are few in situ studies in ambient humic waters which are the focus of this thesis. The aim was to estimate Ali toxicity and thus also Ali concentrations in Swedish humic streams. Subsequently it is necessary to analyse Ali correctly, which was studied by modelling and method intercalibrations. The hypothesis was that the effect of Ali could be followed via physiological effects and Al accumulation, as well as by mortality. Toxicity was studied by in stream exposures of brown trout (Salmo trutta L.) and two salmonid prey organisms (Gammarus pulex and Baetis rhodani) during spring flood. The modelling of the Ali fraction was performed using monitoring data covering all of Sweden with satisfactory results. The essential variables for Ali modelling were determined; Al, DOC, pH and F, while Fe, Ca and Mg had less effect. The automated analytical procedure for Ali (with cation exchange followed by complexation with pyrocatechol violet) was modified and validated and showed to be the preferred method for laboratory analyses. To avoid detrimental effects for brown trout Ali should be <20 ”g/L and pH >5.0; mortality was high when the Ali was above 50 ”g/L. The invertebrates were more sensitive, as mortalities occurred at pH <6.0 and Ali >15 ”g/L for G. pulex, and at pH <5.7 and Ali >20 ”g/L for B. rhodani. It is prudent to use a wide view and let the most sensitive species set the tolerance limits; a pH above 5.7-6.0 and Ali below 15-20 ”g/L allows the stream ecosystems to thrive. Today, as waters are recovering from acidification, the aim of mitigating liming is to carefully adjust dosage to avoid suboptimal water quality. The thresholds found in this thesis can be used to efficiently but carefully decrease liming, as both Ali and pH levels have to be balanced to sustain the recovering aquatic biota