Methodologies using soil organisms for the ecotoxicological assessment of organic wastes

Consultable des del TDXA la portada: Centre de Recerca Ecològica i Aplicacions Forestals (CREAF)Títol obtingut de la portada digitalitzadaLa correcta gestió dels residus orgànics és un dels principals reptes actuals a la Unió Europea, en resposta al fort increment en la seva producció en les darreres dècades. Les creixents limitacions en la incineració i el dipòsit en abocador de residus orgànics ha conduit cap a un increment en el reciclatge en el sòl d'aquests residus en forma d'esmena orgànica, perfilant-se aquesta com la principal via de gestió actual i futura. Malgrat tot, els residus orgànics són també el destí final de contaminants originats amb les activitats humanes. Per tant, el reciclatge de residus orgànics en sòls pot també representar un risc, ja que podria malmetre de manera irreparable els organismes edàfics i les funcions que duen a terme, bàsiques per al funcionament dels ecosistemes terrestres i les societats humanes. Actualment, a la Unió Europea no existeixen requeriments de qualitat mínima per a permetre el reciclatge de residus en el sòl, amb l'excepció dels fangs de depuradora, pels quals existeix una legislació específica. A més, en els escassos casos en què existeix aquesta avaluació de qualitat, el criteri utilitzat és exclusivament basat en anàlisis químiques, i fins ara, els bioassaigs no han estat incorporats en la legislació malgrat els seus avantatges en termes de rellevància per a situacions reals. Malgrat tot, un pas necessari per a aquesta incorporació és la definició de quins bioassaigs són adients per a aquesta finalitat. En aquesta tesi, diversos bioassaigs amb organismes terrestres i aquàtics (Microtox, cladòcers, microorganismes del sòl, plantes, lumbrícids, enquitreids i col·lèmbols), paràmetres biològics (letals i subletals), i procediments (fase sòlida o extractes dels residus) són comparats per al seu ús el l'avaluació de risc ecotoxicològic de diversos residus orgànics per tal de seleccionar-ne els més adients. Posteriorment, per cada residu, i a partir d'un conjunt de dades de toxicitat per a diversos organismes habitants del sòl, s'estimen dosis segures d'esmena, les quals es comparen amb les dosis habituals i amb treballs de camp sobre els efectes d'esmenes orgàniques en la biota del sòl. Finalment, s'estudia la validesa dels resultats de toxicitat d'un residu orgànic obtingut en el sòl artificial OECD per a fer extrapolacions de resultats en sòls naturals. A més, s'avalua la influència de les propietats tant en els organismes test com en la pròpia toxicitat d'un mateix residu.Correct organic wastes management is one of the main challenges in the European Union given its production increase in the last decades. Increasing limitations to organic waste incineration and landfilling, together with its fertilizing potential, has lead to their recycling as soil amendment. In fact, waste use in soil is currently the main waste management option, and it is predicted to increase in the next years. However, organic wastes also are the final sink of pollutants released by human activities. Disposal in soil might lead to irreparable damage for soil organisms and their functions, which play a central role in terrestrial ecosystems and human societies. No requirements of a minimum organic wastes quality exist in the European Union for their recycling in soils, with the exception of sewage sludge, for which specific legislation exist. In this particular case, only chemical assays are taken into account and, to date, bioassays are not considered for this purpose, despite their advantages in terms of relevance for real situations. However, a first step for the inclusion of bioassays into legislation for the quality assessment of wastes is to define suitable methods for this purpose. In this thesis, a wide range of bioassays (Microtox, daphnids, soil microorganisms, plants, earthworms, enchytraeids, and collembolans), endpoints (lethal and sublethal), and procedures (waste's solid-phase and eluates), are evaluated to be used for the ecotoxicological risk assessment of different organic wastes (dewatered, composted and thermally-dried sewage sludges, and thermally-dried pig slurry) in order to select the most suitable methods for this purpose. Furthermore, safe amendment rates for each waste are derived from laboratory data and compared with usual amendment rates and with published field works on waste effects on soil-dwelling organisms. Finally, the validity of OECD artificial soil for waste testing is also assessed by comparison of toxicity results in different natural soils using the same waste. In addition, the biasing influence of soil properties on waste toxicity results is also evaluated, through their effects on the test organisms as well as through their influence on the toxicity of wastes

The Cocoon System : ecotechnology for ecological restoration and rainfed agriculture in the mediterranean basin

Ecological restoration projects of degraded natural areas or rainfed agriculture in the Mediterranean region, especially when they include the plantation of woody species, generally shown to be very expensive and inefficient, mainly due to the large number of leaks during the first summer drought. Even in cases where support irrigation is carried out, medium-term mortality rates remain high, as root systems developed under irrigation conditions present superficial growth being more vulnerable to drought episodes. One of the current initiatives to address this problem is the so-called "Cocoon". It is a 100% biodegradable device, built with recycled plant fibers. It is designed to reduce water stress for the planted seedlings during the first drought season, while also encouraging the development of a deep root system. This device has been successfully implemented in various countries around the world and in a wide range of different environmental conditions and objectives, from the restoration of areas affected by desertification to the recovery of agricultural uses in abandoned lands. Results after first summer drought demonstrate that Cocoon ecotechnology is working well, improving survival ratios and physiological state of the seedlings, despite its efficacy depends on the species and the environmental conditions of the site. Moreover, Cocoon is acting as refuge for some insects and could favor the growing of some commercially interesting fungi. In general, the perception of the agricultural and forestry owners, and the administrations involved, is very positive

Ecotoxicological characterization of biochars : role of feedstock and pyrolysis temperature

Seven contrasting feedstocks were subjected to slow pyrolysis at low (300 or 350 °C) and high temperature (550 or 600 °C), and both biochars and the corresponding feedstocks tested for short-term ecotoxicity using basal soil respiration and collembolan reproduction tests. After a 28-d incubation, soil basal respiration was not inhibited but stimulated by additions of feedstocks and biochars. However, variation in soil respiration was dependent on both feedstock and pyrolysis temperature. In the last case, respiration decreased with pyrolysis temperature (r = − 0.78; p < 0.0001, n = 21) and increased with a higher volatile matter content (r = 0.51; p < 0.017), these two variables being correlated (r = − 0.86, p < 0.0001). Collembolan reproduction was generally unaffected by any of the additions, but when inhibited, it was mostly influenced by feedstock, and generally without any influence of charring itself and pyrolysis temperature. Strong inhibition was only observed in uncharred food waste and resulting biochars. Inhibition effects were probably linked to high soluble Na and NH4 concentrations when both feedstocks and biochars were considered, but mostly to soluble Na when only biochars were taken into account. The general lack of toxicity of the set of slow pyrolysis biochars in this study at typical field application rates (≤ 20 Mg ha− 1) suggests a low short-term toxicity risk. At higher application rates (20-540 Mg ha− 1), some biochars affected collembolan reproduction to some extent, but only strongly in the food waste biochars. Such negative impacts were not anticipated by the criteria set in currently available biochar quality standards, pointing out the need to consider ecotoxicological criteria either explicitly or implicitly in biochar characterization schemes or in management recommendations

Short-term mesofauna responses to soil additions of corn stover biochar and the role of microbial biomass

Biochar additions have been suggested to influence soil microbial communities that, through a cascade effect, may also impact soil fauna. In turn, any direct biochar effects on fauna can influence microbial communities through grazing, physical fragmentation of organic debris (and biochar) and modifying soil structure. If biochar creates a favorable environment for soil microorganisms, it is also plausible for fauna to be attracted to such microbially enriched habitats. However, how soil fauna respond to biochar addition to soil and what are the main factors that drive their behavior has rarely been experimentally addressed. Therefore, the behavior of two mesofauna species was assessed as a result of corn stover biochar (slow pyrolysis at 600 °C) additions to a loamy temperate soil, after preincubation for 2, 17, 31 and 61 d, and related to variations in microbial biomass and activity. Microbial biomass increased by 5-56% and activity by 6-156% with increasing biochar rates for the different preincubation times. Over the incubation time, microbial biomass did not change or increased at most 15% with the different biochar rates, while in turn microbial activity decreased steadily (around 70-80% at day 61). Enchytraeids generally did not show avoidance or preference to biochar when provided with an alternative unamended soil, while collembolans often showed avoidance responses. However, collembolan avoidance to biochar decreased or disappeared in biochar mixtures with higher microbial biomass and water extractable NH4-N content, agreeing with the plausible role of microorganisms to potentially attract soil fauna after biochar applications. Avoidance response was mainly explained by environmental preferences of the test species and not by any toxic effect of the biochar in this study. However, avoidance after the application of biochar may still need to be considered due to the potential negative impacts of individuals' migration on soil ecosystem functioning

Medium-term effects of corn biochar addition on soil biota activities and functions in a temperate soil cropped to corn

Biochar addition to soil has been generally associated with crop yield increases observed in some soils, and increased nutrient availability is one of the mechanisms proposed. Any impact of biochar on soil organisms can potentially translate to changes in nutrient availability and crop productivity, possibly explaining some of the beneficial and detrimental yield effects reported in literature. Therefore, the main aim of this study was to assess the medium-term impact of biochar addition on microbial and faunal activities in a temperate soil cropped to corn and the consequences for their main functions, litter decomposition and mineralization. Biochar was added to a corn field at rates of 0, 3, 12, 30 tons ha−1 three years prior to this study, in comparison to an annual application of 1 t ha−1. Biochar application increased microbial abundance, which nearly doubled at the highest addition rate, while mesofauna activity, and litter decomposition facilitated by mesofauna were not increased significantly but were positively influenced by biochar addition when these responses were modeled, and in the last case directly and positively associated to the higher microbial abundance. In addition, in short-term laboratory experiments after the addition of litter, biochar presence increased NO2 + NO3 mineralization, and decreased that of SO4 and Cl. However, those nutrient effects were not shown to be of concern at the field scale, where only some significant increases in SOC, pH, Cl and PO4 were observed. Therefore, no negative impacts in the soil biota activities and functions assessed were observed for the tested alkaline biochar after three years of the application, although this trend needs to be verified for other soil and biochar types

Applying a GLM based approach to model the influence of soil properties on the toxicity of phenmedipham to Folsomia candida

Purpose: Soil properties are the main explanation to the different toxicities obtained in different soils, due to their influence on chemical bioavailability and the test species performance itself. However, most prediction studies are centred on a few soil properties influencing bioavailability, while their direct effects on test species performance are usually neglected. In our study we develop prediction models for the toxicity values obtained in a set of soils taking into account both the chemical concentration and their soil properties. Materials and methods: The effects on the avoidance behaviour and on reproduction of the herbicide phenmedipham to the collembolan Folsomia candida is assessed in twelve natural soils and the OECD artificial soil. The toxicity outcomes in the different soils are compared and explanatory models are constructed by Generalized Linear Models (GLMs) using phenm edipham concentrations and soil properties. Results and discussion: At identical phenmedip ham concentrations, the effects on reproduction and the avoidance response observed in the OECD soil were similar to those observed in natural soils, while effects on survival were clearly lower in this soil. The organic matter and silt content explained differences in the avoidance behavior in different soils; for reproduction, there was a more complex. Conclusions: Our results highlight the need for approaches taking into account all the soil properties as a whole, as a necessary step to improve the prediction of the toxicity of particular chemicals to any particular soil pattern involving several soil properties

Tap water, bottled water or in-home water treatment systems : Insights on household perceptions and choices

This article addresses household strategies for coping with perceived tap water quality issues. By using a household survey (n = 581) in Catalonia (Spain) and three models, this article analyses the drivers and motivations behind the installation of in-home water treatment systems, and the use of bottled water for drinking and cooking. The main explanatory factors of the higher consumption of bottled water were the perception of poor tap water quality, the lack of in-home treatment systems, and the presence of children at home. Income did not appear as a significant variable explaining the use of bottled water, unlike in other studies. The presence of in-home treatment systems is related to factors, such as perceived bad water quality, larger households, and single-family housing. Income and housing tenure appeared as explanatory variables only when considering systems requiring some kind of installation: lower incomes or renting a multi-family house reduce the probability of having an in-home water treatment that required installation because of important investments and operating costs, and the space needed in the housing units. In-house water treatment systems may become a solid alternative to bottled water when tap water raises problematic perceptions related to bad taste, odor, or lime presence

Environmental impacts of an imidaclopridcontaining formulation: from soils to waters

The neonicotinoid pesticide imidacloprid is among the top sold agrochemicals worldwide. Due to its widespread use in mixtures with different solvents and co-adjuvants, studying the environmental impact of its derived commercial formulations has become mandatory. In this study we used laboratory ecotoxicological tests to quantify the impact of the imidacloprid-containing formulation Confidor® 20SL on the terrestrial and aquatic compartments. Lethal and sublethal effects of recommended application doses of the product were assessed on standard terrestrial invertebrates Eisenia fetida and Folsomia candida whereas the toxicity of leachates from contaminated soils was evaluated in the aquatic model organisms Daphnia magna and Raphidocelis subcapitata. The exposure to environmentally relevant concentrations of imidacloprid causedno mortality to earthworms (LC50 of 4.23 mg imidaclopridkg-1 dry soil) but altered their behavior and reproductionpatterns (EC50 values for avoidance and reproduction testsof 0.43 and 1.40 mg imidacloprid kg-1 dry soil, respectively).Effects on collembolans F. candida were negligible.Imidacloprid presented moderate leachability, with recoveryrates that ranged from 25.4 to 50.4% of the amountpresent in soils and concentrations in water extracts from13.05 to 71.8 μg L-1. Standard aquatic ecotoxicity testswere not able detect chronic or acute toxicity in standardtest organisms. Nonetheless, concentrations of the insecticidein water extracts were high enough to pose a lethalthreat to several other non-standard aquatic organisms

Ecotoxicological assessment of organic wastes using the soil collembolan Folsomia candida

The reproduction test with the collembolan Folsomia candida is used as a tool to evaluate the ecotoxicological potential of organic wastes currently applied to soil. Seven organic wastes (dewatered sewage sludges, thermally dried sewage sludges, composted sewage sludges, and a thermally dried pig slurry) were tested. These wastes had different origins, treatments, and pollutant burdens, and were selected as a representative sample of the wide variety of wastes currently generated. F. candida showed varied sensitivity depending on the waste, but also depending on the endpoint assessed. Reproduction was more sensitive than survival, although no correlations between reproduction and physico-chemical parameters and pollutant burden could be found. On the other hand, mortality was directly related to the lack of stability of wastes, probably reflecting the toxicity of end-products such as ammonium. Body length was not shown to be a sensitive endpoint for waste testing, as it was neither affected nor even stimulated by waste concentrations. Organic matter, pH, and electrical conductivity varied with waste concentration in soil-waste mixtures, although their effect on collembolan performance was expected to be low and part of the complex effect exerted by wastes when applied to real soils. Selection of the water content is the most problematic aspect in waste testing, as it may affect the performance of test organisms. In this study, a qualitative approach for water content selection in waste testing was considered to be the most suitable. Treatment of wastes affected composition and toxicity. Composting of sewage sludge increased its stability, compared to the initial sludge, but decreased its non-persistent organic pollutant burden and toxicity. On the other hand, thermally dried wastes from sludge and pig slurry displayed high toxicity, mainly attributable to their low stability. The results from the study indicate the inability of chemical methods to predict the effects of complex mixtures on living organisms with respect to ecotoxicity bioassays, but also the need for stabilization treatments of organic wastes prior to their reuse in soils