Olli-Pekka Penttinen

Increasing lake water and sediment oxygen levels using slow release peroxide

The sediment and hypolimnion of many Finnish lakes suffer from anoxia due to increasing nutrient loading. The aim of this research was to develop a method for increasing the oxygen level using granulated calcium peroxide (CaO₂) as a slow oxygen releasing compound. This compound releases oxygen (O₂) in a reaction with water during 5 to 7 months. The method was tested in both laboratory and field conditions. In the field test granulated CaO₂ were then spread manually from a rowing boat over the whole surface of the test pond. The granules sink onto and into the sediment. No mixing was needed. The dissolved oxygen concentration increased significantly during a laboratory experiment with a CaO₂ amendment of 75 g m⁻² and in a pond experiment with a CaO₂ amendment of 50 g m⁻². In the pond experiment, the effect was visible for the entire 40-week experiment. In the laboratory, the abundance of aerobic bacteria increased in the sediment after CaO₂ addition, while the pond experiment gave more mixed results. The organic matter content of the sediment did not change during the experiment in the control pond, but decreased from 18% to 4% in the pond with the CaO₂ amendment. This was possibly due to enhanced microbial activity in the test pond. Although the results show improved oxygen concentrations and effects on the sediment organic matter following CaO₂ amendment, the usability of this method in larger lakes remains to be tested.

Acute toxicity of birch tar oil on aquatic organisms

Birch tar oil (BTO) is a by-product of processing birch wood in a pyrolysis system. Accumulating evidence suggests the suitability of BTO as a biocide or repellent in terrestrial environments for the control of weeds, insects, molluscs and rodents. Once applied as biocide, BTO may end up, either through run-off or leaching, in aquatic systems and may have adverse effects on non-target organisms. As very little is known about the toxicity of BTO to aquatic organisms, the present study investigated acute toxicity (LC50/EC50) of BTO for eight aquatic organisms. Bioassays with the Asellus aquaticus (crustacean), Lumbriculus variegatus (oligochaeta worm), Daphnia magna (crustacean), Lymnea sp. (mollusc), Lemna minor (vascular plant), Danio rerio (fish), Scenedesmus gracilis (algae), and Vibrio fischeri (bacterium) were performed according to ISO, OECD or USEPA-guidelines. The results indicated that BTO was practically nontoxic to most aquatic organisms as the median effective BTO concentrations against most organisms were >150 mg L-1. In conclusion, our toxicity tests showed that aquatic organisms are to some extent, invariably sensitive to birch tar oil, but suggest that BTO does not pose a severe hazard to aquatic biota. We deduce that, unless BTOs are not applied in the immediate vicinity of water bodies, no special precaution is required

Birch tar oil is an effective mollusc repellent: field and laboratory experiments using Arianta arbustorum (Gastropoda: Helicidae) and Arion lusitanicus (Gastropoda: Arionidae)

Populations of two molluscs, the land snail Arianta arbustorum and the Iberian slug Arion lusitanicus, have increased substantially in many places in the northern Fennoscandia in recent years. This has resulted in considerable aesthetic and economic damage to plants in home gardens and commercial nurseries. Birch tar oil (BTO), is a new biological plant protection product, and was tested against these molluscs. In this study we examined whether 2 types of BTO, used either alone, mixed together, or mixed with Vaseline®, could be applied as 1) a biological plant protection product for the control of land snails by direct topical spray application, 2) as a repellent against snails when painted on a Perspex® fence, and 3) as a repellent against slugs when smeared on pots containing Brassica pekinensis seedlings. Both the fences and the pots with seedlings were placed in each field with a high population of the target organism. When applied as a spray on snails, BTO did not act as a toxic pesticide but rendered the snails inactive for a period of several months. The BTO barriers were effective in repelling both snails and slugs. However, the repellent effect of BTO alone against the molluscs was short-term. Repeated treatments were required to keep the slugs away from the plants and we found that the interval between treatments should not exceed two weeks. A collar fastened around the rim of the pots, combined with the BTO treatment, did not give any additional benefit in hindering slugs from invading the plants. Most noticeably, the BTO+Vaseline® mixture prevented the land snails from passing over the treated fences for up to several months. The results of these experiments provide evidence that BTO, especially when mixed with Vaseline®, serves as an excellent long-term repellent against molluscs.

Body residues as dose for sublethal responses in alevins of landlocked salmon (Salmo salar m. sebago): A direct calorimetry study

Questions of organism-specific factors, toxicity endpoints, and their relation to mode-of-action all are related to consistency and applicability of body residue-based approaches. To address this issue, direct calorimetry was used to evaluate metabolic responses of alevins of landlocked salmon (Salmo salar m. sebago) to pentachlorophenol (PCP) exposure ranging from 0 to 1.04 microM for 24 h or 24, 48, and 72 h (0, 0.26, and 0.55 microM, respectively). The body residues were used as a dose metric for sublethal responses. The body size, rapid ontogenetic development, and exposure to a specific pollutant all were heat output-modifying factors. The acute exposure (24-72 h) to PCP led to a heat output-enhancing effect, which directly was related to an internal concentration of PCP in the range of 0.01 to 0.15 micromol/g. Within the treatments, body size per level of metabolic rate and magnitude of physiological response were not correlated, thus the alevins with higher mass-specific metabolic rate were not more sensitive to PCP. Primarily, increasing metabolic rate during posthatch development controls PCP toxicity only by affecting bioaccumulation kinetics, not the toxic potency of the chemical. New information of a relationship between observed natural variation in measured physiological trait of fish and PCP-induced response and its body residue-based level is of ecotoxicological importance.

Selective toxicity at low doses: experiments with three plant species and toxicants.

During the last decade, the paradigm that low toxicant doses often have stimulatory effects on plants has become widely accepted. At the same time, low toxicant doses of metal salts have been observed to inhibit the growth of the most vigorous seedlings of a population in vitro, although mean plant size has remained unaffected. We hypothesized that this kind of selective low-dose toxicity is not restricted to inorganic contaminants. We exposed annual plants (babys breath Gypsophila elegans, purslane Portulaca oleracea, and duckweed Lemna minor) to 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-γ-2-benzopyran (HHCB) and 4-tert-octylphenol and lead acetate. As compared to unexposed G. elegans roots, 4-tert-octylphenol did not affect the mean root size of all seedlings, but it reduced the average length of roots longer than the 98th percentile. A comparable response was found in case of G elegans roots treated with lead acetate beyond the 90th percentile. The average size of roots beyond the 90th percentile was decreased also when L. minor was exposed to lead acetate though the means of all roots were constant. P. oleracea seemed to be insensitive to selective toxicity. We conclude that selective toxicity at low doses should be considered in parallel with hormesis.

Effects of birch tar oils on soil organisms and plants.

Koivupuun pyrolyysissa puuaine hajoaa lammon vaikutuksestaerilaisiksi tuotteiksi. Prosessin yhteydessa syntyy muun muassa koivuoljytisletta (birch tar oil BTO). Koivuoljytisle nayttaa useiden viela tarkemmin tutkimattomien todisteiden mukaan toimivan rikkakasvien, tuhohyonteisten ja jyrsijoiden torjunta-aineena. Sen koostumuksesta, vaikutuksista ymparistoon ja myrkyllisyydesta elioille on kuitenkin saatavilla hyvin vahan tietoa. Taman tutkimuksen tarkoitus oli selvittaa koivuoljytisleen 1) vaikutus maaperan ankyri- ja sukkulamatoihin seka mikro-organismeihin seka maarittaa koivuoljytisleen 2) 14 vrk:n LC50 arvo peltolierolle (Aporrectodea caliginosa) ja 28 vrk EC50 arvo hyppyhantaisen (Folsomia candida) lisaantymiselle. Koivuoljytisleen vaikutukset maaperan ankyrimatojen biomassaan- ja sukkulamatojen lukumaaraan olivat vahaisia. Kasvillisuuteen BTO vaikutti tappaen suurimman osan kasvien maan paallisista osista vuorokauden kuluessa. Kasvillisuuden toipuminen alkoi kuitenkin nopeasti eika kenttakokeessa havaittu 2.5 kk kuluttua kasittelyista kasvibiomassassa ja kasvilajistossa eroa, vuohenputkea (Aporrectodea caliginosa) lukuunottamatta, eri kasittelyjen kesken. Sen sijaan mikrokosmoksissa tehdyissa kokeissa kasvibiomassa oli viela 50 vrk kuluttua kasittelyista 100% koivutisleella kasitellyissa maissa merkitsevasti pienempi kuin kontrollimaissa. Koivutisle ei vaikuttanut mikrobien biomassaan. Sen sijaan se vaikutti positiivisesti mikrobiaktiivisuuteen heti lisayksensa jalkeen toimien ilmeisesti lisaresurssina mikrobeille. Negatiivinen vaikutus mikrobiaktiivisuuteen 28 ja 42 vrk kuluttua koivutisleen lisayksesta saattoi johtua kasvien kuihtumisesta: kasvit kuolivat eivatka siten vapauttaneet juurieritteita maaperaan, mutta kuolleesta kasvillisuudesta ei ollut viela ehtinyt modostua kariketta mikrobien ravinnoksi, jolloin ne vaipuivat lepotilaan. Kaiken kaikkian koivuoljytisleen vaikutus maaperan ravintoverkkoon oli vahainen. 14 vrk:n LC50 arvo peltolierolle (Aporrectodea caliginosa) oli 6560 mg BTO1 kg-1 ja 28 vrk EC50 arvo hyppyhantaisen (Folsomia candida) lisaantymiselle oli 5100 mg BTO1 kg-1. Luvut viittaavat koivutisleen olevan elioille myrkyllista vasta suurina pitoisuuksina verrattuna moniin nykyisin kasvinsuojelussa vastaavissa tarkoituksissa kaytettyihin kemiallisiin yhdisteisiin.

Ecological Risks of an Old Wood Impregnation Mill: Application of the Triad Approach

Abstract Although many studies deal with the distribution and mobility of chromated copper arsenate (CCA) metals in soil, the ecotoxicity of CCA-contaminated soils is rarely studied. The Triad approach was applied to determine the ecological risks posed by a CCA mixture at a decommissioned wood impregnation mill in southern Finland. A combination of (1) chemical analyses; (2) toxicity tests with plants (aquatic: Lemna minor; terrestrial: Lactuca sativa), earthworms (Lumbricus rubellus), and enchytraeids (Enchytraeus albidus) conducted on contaminated soils, their aqueous extracts, and well water collected from the site; and (3) determination of the abundance of enchytraeids and nematodes and the bioaccumulation of metals in plants (horsetail) collected from the field were used to assess the actual risk. Although metal concentrations were low, L. minor growth appeared to be reduced by As contamination of the well water. In soil, metals were heterogeneously distributed with total concentrations of 14.8 to 4360 mg As/kg, 15.2 to 1740 mg Cr/kg, and 4.83 to 790 mg Cu/kg. In several samples, concentrations were above Finnish regulatory guideline values and exceeded the half maximal effective concentration (EC50) or 50% lethal concentration (LC50) values for the toxicity of the individual metals to earthworms and enchytraeids, indicating hazards to the ecosystem. (Bio)availability of metals was high, as indicated by weak electrolyte extractions and body residues in L. rubellus and E. albidus exposed in bioassays. Earthworm survival correlated significantly with body metal concentrations, but not with soil total metal concentrations. Enchytraeid responses in the soil bioassays were less sensitive to CCA metal exposure. Plant growth was affected by CCA pollution, with L. sativa root elongation correlating significantly with total and available As concentrations and L. minor development being significantly reduced in H2O extracts of the most contaminated soil sample. Abundance of enchytraeids and nematodes in the field was much lower than in nonpolluted Finnish soils but did not significantly correlate with CCA contamination. Arsenic accumulation in horsetail did not correlate with As concentrations in soil. Overall, the results of the 3 lines of evidence of the Triad approach indicate possible increased risks to the ecosystem at the most contaminated sites of the CCA treatment area.

Using the critical body residue approach to determine the acute toxicity of cadmium at varying levels of water hardness and dissolved organic carbon concentrations

The linkage between acute adverse effects of cadmium and internal cadmium levels were investigated for the oligochaete worm Lumbriculus variegatus in water at varying degrees of hardness and two different dissolved organic carbon (DOC) concentrations. The LC₅₀s for the effect of cadmium on the survival of the worms greatly differed depending on water hardness and DOC. We found less variability in internal metal toxicity metrics (lethal residue; LR₅₀s) than in external toxicity metrics (lethal concentration; LC₅₀s): LC₅₀s varied from 2.4 to 66.1 μmol/L, while LR₅₀s varied only from 226 to 413 μmol/kg wet weight. The cadmium body burden appeared to be independent of exposure conditions. From our experimental data, a critical cadmium body residue (324 ± 78 μmol/kg wet weight) associated with 50% lethality was derived. The protective role of DOC and water hardness against cadmium toxicity was evident.

Low toxicant concentrations decrease the frequency of fast-growing seedlings at high densities of annual baby's breath (Gypsophila elegans)

Very low toxicant concentrations reduce the frequency of most vital seedlings in dense stands in vitro.

Validation of the OECD reproduction test guideline with the New Zealand mudsnail Potamopyrgus antipodarum using trenbolone and prochloraz

The Organisation for Economic Cooperation and Development (OECD) provides several standard test methods for the environmental hazard assessment of chemicals, mainly based on primary producers, arthropods, and fish. In April 2016, two new test guidelines with two mollusc species representing different reproductive strategies were approved by OECD member countries. One test guideline describes a 28-day reproduction test with the parthenogenetic New Zealand mudsnail Potamopyrgus antipodarum. The main endpoint of the test is reproduction, reflected by the embryo number in the brood pouch per female. The development of a new OECD test guideline involves several phases including inter-laboratory validation studies to demonstrate the robustness of the proposed test design and the reproducibility of the test results. Therefore, a ring test of the reproduction test with P. antipodarum was conducted including eight laboratories with the test substances trenbolone and prochloraz and results are presented here. Most laboratories could meet test validity criteria, thus demonstrating the robustness of the proposed test protocol. Trenbolone did not have an effect on the reproduction of the snails at the tested concentration range (nominal: 10–1000 ng/L). For prochloraz, laboratories produced similar EC10 and NOEC values, showing the inter-laboratory reproducibility of results. The average EC10 and NOEC values for reproduction (with coefficient of variation) were 26.2 µg/L (61.7%) and 29.7 µg/L (32.9%), respectively. This ring test shows that the mudsnail reproduction test is a well-suited tool for use in the chronic aquatic hazard and risk assessment of chemicals.