Using a combination of bioassays, bioaccumulation kinetics and mixture toxicity tests to assess the ecotoxicological risk of CCA contaminated soils in Finland

In this thesis we studied the effects of Chromated Copper Arsenate (CCA) compounds in Finnish forest ecosystems. The research site was located in Hartola, southern Finland. Between 1958 and 1966, there was a small wood impregnation plant which used the so-called Lahontuho K-33 impregnating agent. The aim of this thesis is to use a combination of applied bioassays, uptake and elimination kinetics and binary mixture toxicity experiments to gain better understanding of the bioavailability of Cu, Cr and As and their potential eco(toxico)logical risk at the Hartola site. This approach fits the TRIAD method, which uses a combination of chemical analyses, bioassays and field observations to assess the actual risk of contaminated soils. The thesis contains three articles that approached the risk assessment of CCA compounds using different methods. In article I, bioassays were used to assess whether Cr, Cu and As are bioavailable to plants (Lemna minor and Lactuca sativa) and invertebrates (Enchytraeus albidus and Lumbricus rubellus) and whether they pose a risk to the ecosystem. Article II focused on the bioavailability of chromium, copper and arsenic in Hartola soils using an uptake and elimination kinetics approach with the earthworm Eisenia andrei. Article III determined the toxicity of the CCA metals, single and in binary mixtures, to earthworms (Eisenia andrei), in particular using reproduction as the endpoint. Based on the studies in article I, it was concluded that the CCA metals in the Hartola soils cause damage to organisms and pose a risk to the ecosystem. Metals did bioaccumulate, as shown by the metal concentrations in earthworms and plants. The toxic effects obtained in bioassays correlated best with the concentration of arsenic in the Hartola soils. In article II, earthworms were shown to take up and excrete chromium and copper in the same way: fast uptake and fast elimination occurred reaching steady state within 1 to 3 days. Arsenic uptake in the earthworms, however, was slow and did not reach equilibrium. Uptake and elimination rate constants were used to calculate the bioaccumulation factor (BAF), which was highest for As, supporting the conclusion of article I. In article III, at low concentrations copper and chromium had a hormetic effect on earthworm reproduction, which was not seen with As. Arsenic was already toxic to the earthworms at low concentrations. Arsenic-containing mixtures also were highly toxic. The binary mixtures of CCA metals generally acted antagonistic on earthworm reproduction when tested against to the Concentration Addition model. It seems that the CCA metals react with each other, leading to a reduced toxicity in the mixtures. The results of this thesis showed that at the study site the metals were bioavailable as shown from their bioaccumulation in invertebrates and plants, and that the risk of CCA pollution is mainly due to As. Based on our results we suggest that the TRIAD method is a useful approach to determining the potential eco(toxico)logical risk of CCA metals.Tässä väitöskirjassa tutkittiin kromia (Cr), kuparia (Cu) ja arseenia (As) sisältävän yhdisteen (CCA-yhdiste) vaikutuksia suomalaiseen metsäekosysteemiin Hartolassa, Etelä-Suomessa. Vuosien 1958 – 1966 välisenä aikana alueella kyllästettiin sähköpylväitä Lahontuho K-33 kyllästysaineella. Tutkimusmenetelminä käytettiin valikoituja biotestejä, metallien akkumulaatio- ja eliminaatiokinetiikkaa ja seostoksisuuskokeita, joiden avulla saatiin lisää tietoa kromin, kuparin ja arseenin biosaatavuudesta ja näiden metallien mahdollisesta eko(toksiko)logisesta riskistä ekosysteemille TRIAD-menetelmää hyödyntäen. Tämä lähestymistapa sopii TRIAD-menetelmän hyödyntämiseen, koska siinä hyödynnetään kemiallisten analyysien kombinaatioita, biotestejä ja kenttähavaintoja määritettäessä pilaantuneiden maiden todellista riskiä. Tutkimus jaettiin kolmeen osaan, joissa käsiteltiin CCA-yhdisteiden riskinarviointia em. menetelmiä apuna käyttäen. Artikkelissa I selvitettiin biotestien avulla, ovatko Cr, Cu ja As kasveille (Lemna minor ja Lactusa sativa) ja selkärangattomille (Enchytraeus albidus ja Lumricus rubellus) biosaatavassa muodossa ja aiheuttavatko ne riskiä ekosysteemille. Artikkelissa II tutkittiin kromin, kuparin ja arseenin biosaatavuutta, akkumulaatio- ja eliminaatiokinetiikan avulla. Tavoitteena oli selvittää, kuinka nopeasti lierot (Eisenia andrei) ottavat elimistöönsä ko. metalleja ja kuinka nopeasti ne pystyvät erittämään metallin pois sen jälkeen, kun lierot on siirretty puhtaaseen OECD standardin mukaisesti valmistettuun keinotekoiseen maahan. Näiden kokeiden avulla haluttiin tarkastella tarkemmin ko. metallien biosaatavuutta ja pohtia, miten maaperän ominaisuudet vaikuttavat metallien biosaatavuuteen sekä saada lisätietoa alueen riskinarvioinnin tueksi. Artikkelissa III selvitettiin yksittäisen metallin ja kahdesta metallista muodostettujen seosten (Cu-As, Cu-Cr, Cr-As) vaikutuksia lieroihin (Eisenia andrei), etenkin niiden lisääntymiseen käyttäen excel-pohjaista MIXTOX-mallia. Artikkelin I tutkimukset osoittavat, että CCA-yhdisteen metallit aiheuttavat eliöstölle haittaa ja aiheuttavat riskiä ekosysteemille. Cr, Cu ja As kertyivät selkarangattomiin. Arseenin pitoisuus maaperässä korreloi parhaiten biotesteissä saatuihin haitallisiin vaikutuksiin. Artikkelissa II lierot akkumuloivat ja eliminoivat kromia ja kuparia nopeasti 1 – 3 päivässä, kun taas arseenilla lierot eivät saavuttaneet tasapainoa kokeen aikana. Tulosten perusteella voidaan todeta, että As kertyy hitaasti lieroihin. Akkumulaatio- ja eliminaatiovaiheen kineettisten vakioiden avulla lasketut biokertyvyysvakiot (BAF) vahvistivat em. tulokset. Artikkelissa III tuli esille, että pienissä pitoisuuksissa kuparilla ja kromilla esiintyi hormesis-vaikutus, jota arseenilla ei esiintynyt. Tämä johtui siitä, että jo alhaisissa konsentraatioissa arseeni aiheutti haitallisia vaikutuksia lieroihin esiintyessään yksin ja metalliseoksissa. Kaikki seokset osoittivat antagonisia yhteisvaikutuksia lierojen lisääntymistesteissä. CCA-metallit reagoivat keskenään, mutta binäärisissä seoksissa niiden toksisuus vähenee. Tuloksiemme perusteella näyttää siltä, että riskinarvioinnissa käytettävä TRIAD-menetelmä, on hyödyllinen määritettäessä CCA-metallien ympäristövaikutusten todentamisessa

An uptake and elimination kinetics approach to assess the bioavailability of chromium, copper, and arsenic to earthworms (Eisenia andrei) in contaminated field soils

The aim of this study was to determine the bioavailability of metals in field soils contaminated with chromated copper arsenate (CCA) mixtures. The uptake and elimination kinetics of chromium, copper, and arsenic were assessed in the earthworm Eisenia andrei exposed to soils from a gradient of CCA wood preservative contamination near Hartola, Finland. In soils contaminated with 1480–1590 mg Cr/kg dry soil, 642–791 mg Cu/kg dry soil, and 850–2810 mg Ag/kg dry soil, uptake and elimination kinetics patterns were similar for Cr and Cu. Both metals were rapidly taken up and rapidly excreted by Eisenia andrei with equilibrium reached within 1 day. The metalloid As, however, showed very slow uptake and elimination in the earthworms and body concentrations did not reach equilibrium within 21 days. Bioaccumulation factors (BAF) were low for Cu and Cr (Peer reviewe

Toxicity of binary mixtures of Cu, Cr and As to the earthworm Eisenia andrei

Chromated copper arsenate (CCA) mixtures were used in the past for wood preservation, leading to large scale soil contamination. This study aimed at contributing to the risk assessment of CCA-contaminated soils by assessing the toxicity of binary mixtures of copper, chromium and arsenic to the earthwormEisenia andreiin OECD artificial soil. Mixture effects were related to reference models of Concentration Addition (CA) and Independent Action (IA) using the MIXTOX model, with effects being related to total and available (H2O and 0.01 M CaCl(2)extractable) concentrations in the soil. Since only in mixtures with arsenic dose-related mortality occurred (LC(50)92.5 mg/kg dry soil), it was not possible to analyze the mixture effects on earthworm survival with the MIXTOX model. EC(50)s for effects of Cu, Cr and As on earthworm reproduction, based on total soil concentrations, were 154, 449 and 9.1 mg/kg dry soil, respectively. Effects of mixtures were mainly antagonistic when related to the CA model but additive related to the IA model. This was the case when mixture effects were based on total and H2O-extractable concentrations; when based on CaCl2-extractable concentrations effects mainly were additive related to the CA model except for the Cr-As mixture which acted antagonistically. These results suggest that the CCA components do interact leading to a reduced toxicity when present in a mixture.Peer reviewe