Uptake and Elimination of 4-Nonylphenol in the Enchytraeid Enchytraeus albidus.

We determined the uptake and elimination kinetics of 4-nonylphenol (4-NP) in Enchytraeus albidus. A relatively fast degradation of 4-NP in test soil occurred at 20°C (λ = 0.11 day(-1)). The concentration of 4-NP in worm tissue followed a three-phase kinetics model, with a short phase of fast 4-NP accumulation shortly after exposure start (k u = 0.97 mg kg(-1) day(-1)), followed by partial elimination (K e1 = 1.47 day(-1)) until reaching the equilibrium phase (A = 44.7 mg kg(-1) fresh tissue), and finally the elimination upon transfer to uncontaminated soil (K e2 = 0.67 day(-1)). During uptake, the internal concentration was similar to the concentration found in the soil, with a BAF ~ 1. In un-spiked soil, elimination took place within the first 24 h (elimination t1/2 ~ 1 day).

Worms from the Arctic are better adapted to freezing and high salinity than worms from temperate regions: oxidative stress responses in Enchytraeus albidus.

Enchytraeus albidus is a freeze-tolerant enchytraeid found in diverse habitats, from supra-littoral to terrestrial, and spanning temperate to arctic regions. Thus, this worm is often exposed to sub-zero temperatures and fluctuating salinity regimes that can lead to physiological stress. We therefore studied the oxidative stress by measuring lipid peroxidation, anti-oxidant defenses and neurotransmission activity in E. albidus from arctic (Greenland) and temperate (Germany) regions during a short-term exposure to saline conditions (0, 15, 35 and 50‰ NaCl) and low temperatures (+2, -2 and -5 °C). Various enzymatic and non-enzymatic oxidative stress markers were analyzed. Results have shown that both salt and freezing caused oxidative stress in E. albidus, particularly from Germany, as confirmed by catalase, glutathione-S-transferase and superoxide dismutase activities and lipid peroxidation levels. Neurotransmission (as judged from acetylcholinesterase activity) was reduced by saline conditions at +2 °C, but stimulated at -2 and -5 °C. Worms from Greenland had relatively higher and more stable levels of antioxidants than worms from Germany, reflecting their higher tolerance of freezing and saline conditions.

Age-induced perturbation in cell membrane phospholipid fatty acid profile of longevity-selected Drosophila melanogaster and corresponding control lines.

Various compositions of fatty acids can produce cell membranes with disparate fluidity and propensity for oxidation. The latter characteristic, which can be evaluated via the peroxidation index (PI), has a fundamental role in the development of the "membrane-pacemaker theory" of aging. This study tried to evaluate differences between the membrane phospholipid fatty acid (PLFA) profile of longevity-selected (L) and corresponding control (C) lines of Drosophila melanogaster with age (3, 9, 14 and 19 days) and its consequences on phase transition temperature as a function of membrane fluidity. Despite an equal proportion of polyunsaturated fatty acids, PI and double bond index over all ages in both experimental groups, monounsaturated fatty acids showed significant variation with advancement of age in both L and C lines. A significant age-associated elevation of the unsaturation vs. saturation index in parallel with a gradual reduction of the mean melting point was observed in longevous flies. PLFA composition of the L vs. C lines revealed a dissimilarity in 3-day old samples, which was based on the positive loading of C(14:0) and C(18:3) as well as negative loading of C(18:0). The findings of this study are not in agreement with the principle of the "membrane pacemaker theory" linking PI and longevity. However, the physiochemical properties of PLFAs in longevity lines may retard the cells' senescence by maintaining optimal membrane functionality over time. Identical susceptibility to peroxidation of both types of lines underlines the involvement of other mechanisms in protecting the bio-membrane against oxidation, such as the reduced production of mitochondrial reactive oxygen species or improvement of the antioxidant defense system in longer-lived phenotypes. Concurrent assessments of these mechanisms in relation to cell membrane PLFA composition may clarify the cellular basis of lifespan in this species.

Soil salinity increases survival of freezing in the enchytraeid Enchytraeus albidus.

Enchytraeus albidus is a freeze-tolerant enchytraeid found in diverse habitats, ranging from supralittoral to terrestrial and spanning temperate to arctic regions. Its freeze tolerance is well known but the effect of salinity in this strategy is still poorly understood. We therefore studied the combined effect of salinity (0, 15, 35, 50‰ NaCl) and sub-zero temperatures (-5, -14, -20°C) on the freeze tolerance of E. albidus collected from two distinct geographical regions (Greenland and Germany). A full factorial design was used to study survival, and physiological and biochemical end points. The effect of salinity on the reproduction of German E. albidus was also assessed. Exposure for 48 h to saline soils prior to cold exposure triggered an increase in osmolality and decrease in water content. Worms exposed to saline soils had an improved survival of freezing compared to worms frozen in non-saline soils, particularly at -20°C (survival more than doubled). Differential scanning calorimetry measurements showed that the fraction of water frozen at -5 and -14°C was lower in worms exposed to 35‰ NaCl than in control worms. The lowering of ice content by exposure to saline soils was probably the main explanation for the better freeze survival in saline-exposed worms. Glucose increased with decreasing temperature, but was lower in saline than in non-saline soils. Thus, glucose accumulation patterns did not explain differences in freeze survival. Overall, the physiological responses to freezing of E. albidus from Greenland and Germany were similar after exposure to saline soils. Soil salinity up to 30‰ improved reproduction by a factor of ca. 10.

Satiety, but not total PYY, Is increased with continuous and intermittent exercise.

OBJECTIVE: This study determined the hormonal and subjective appetite responses to exercise (1-h continuous versus intermittent exercise throughout the day) in obese individuals. DESIGN AND METHODS: Eleven obese subjects (>30 kg/m(2) ) underwent three 12-h study days: control condition [sedentary behavior (SED)], continuous exercise condition [(EX) 1-h exercise], and intermittent exercise condition [(INT) 12 hourly, 5-min bouts]. Blood samples (every 10 min) were measured for serum insulin and total peptide YY (PYY) concentrations, with ratings of appetite (visual analog scale [VAS): every 20 min]. Both total area under the curve (AUC), and subjective appetite ratings were calculated. RESULTS: No differences were observed in total PYY AUC between conditions, but hunger was reduced with INT (INT < EX; P < 0.05), and satiety was increased with both SED and INT conditions (INT > EX and SED > EX; P < 0.05). A correlation existed between the change in total PYY and insulin levels (r = -0.81; P < 0.05), and total PYY and satiety (r = 0.80; P < 0.05) with the EX condition, not the SED and INT conditions. CONCLUSIONS: The total PYY response to meals is not altered over the course of a 12-h day with either intermittent or continuous exercise; however, intermittent exercise increased satiety and reduced hunger to a greater extent than continuous exercise in obese individuals.

Assessment of endothelial function and blood metabolite status following acute ingestion of a fructose-containing beverage.

AIM: Fructose intake has increased concurrent with sugar intake and this increase has been implicated in contributing to the development of metabolic syndrome risk factors. Recent evidence suggests a role for uric acid (UA) as a potential mediator via suppression of nitric oxide (NO) bioavailability. The aim of this study was to explore this hypothesis by measuring changes in UA concentration and systemic NO bioavailability as well as endothelial function in response to acute ingestion of a glucose-fructose beverage. METHODS: Ten young (26.80 +/- 4.80 years), non-obese (body mass index: 25.1 +/- 2.55 kg m(-2); percent body fat: 13.5 +/- 6.9%) male subjects ingested either a glucose (100 g dextrose in 300 mL) or isocaloric glucose-fructose (glucose : fructose; 45 : 55 g in 300 mL) beverage. Blood was sampled pre- and every 15-min post-ingestion per 90 min and assayed for glucose, lactate, fructose, total nitrate/nitrate, UA and blood lipids. Forearm blood flow and pulse-wave velocity were recorded prior to and at 30 and 45 min time intervals post-ingestion, respectively, while heart rate, systolic and diastolic blood pressure were recorded every 15 min. RESULTS: The glucose-fructose ingestion was associated with a significant (P < 0.05) increase in plasma lactate concentration and altered free fatty acid levels when compared with glucose-only ingestion. However, UA was not significantly different (P = 0.08) between conditions (AUC: -1018 +/- 1675 vs. 2171 +/- 1270 micromol L(-1) per 90 min for glucose and glucose-fructose conditions respectively). Consequently, no significant (P < 0.05) difference in endothelial function or systemic NO bioavailability was observed. CONCLUSION: Acute consumption of a fructose-containing beverage was not associated with significantly altered UA concentration, endothelial function or systemic NO bioavailability.

Sugar sweet springtails: on the transcriptional response of Folsomia candida (Collembola) to desiccation stress.

Several species of Collembola survive stressful desiccating conditions by absorbing water vapour from the environment. To obtain insight into the transcriptomic responses underlying this 'water vapour absorption' mechanism we subjected Folsomia candida (Collembola) to transcriptome profiling. We show that ecologically relevant desiccation stress leads to strong time-dependent transcriptomic changes. Exposure of F. candida to 98.2% relative humidity over an interval of 174 h resulted in a high number of gene transcripts being differentially expressed (up to 41%; P-value < 0.05). Additional Gene Ontology analyses suggest that carbohydrate transport, sugar catabolism and cuticle maintenance are biological processes involved in combating desiccation. However, many additional pathways seem to be affected; additional experiments are needed to elucidate which responses are primarily linked to desiccation resistance.

Plasticity of heart rate signalling and complexity with exercise training in obese individuals with and without type 2 diabetes.

OBJECTIVE: To examine the responsiveness of cardiac autonomic function and baroreflex sensitivity (BRS) to exercise training in obese individuals without (OB) and with type 2 diabetes (ObT2D). DESIGN: Subjects were tested in the supine position and in response to a sympathetic challenge before and after a 16-week aerobic training program. All testing was conducted in the morning following a 12-h fast. SUBJECTS: A total of 34 OB and 22 ObT2D men and women (40-60 years of age) were studied. MEASUREMENTS: Heart rate variability (HRV) was measured at rest via continuous ECG (spectral analysis with the autoregressive approach) and in response to upright tilt. The dynamics of heart rate complexity were analyzed with sample entropy and Lempel-Ziv entropy, and BRS was determined via the sequence technique. Subjects were aerobically trained 4 times per week for 30-45 min for 16 weeks. RESULTS: Resting HR decreased and total power (lnTP, ms(2)) of HRV increased in response to exercise training (P<0.05). High frequency power (lnHF) increased in OB subjects but not in OBT2D, and no changes occurred in ln low frequency/HF power with training. Upright tilt decreased lnTP and lnHF and increased LF/HF (P<0.01) but there were no group differences in the magnitude of these changes nor were they altered with training in either group. Tilt also decreased complexity (sample entropy and Lempel-Ziv entropy; P<0.001), but there was no group or training effect on complexity. BRS decreased with upright tilt (P<0.01) but did not change with training. Compared to OB subjects the ObT2D had less tilt-induced changes in BRS. CONCLUSION: Exercise training improved HRV and parasympathetic modulation (lnHF) in OB subjects but not in ObT2D, indicating plasticity in the autonomic nervous system in response to this weight-neutral exercise program only in the absence of diabetes. HR complexity and BRS were not altered by 16 weeks of training in either OB or ObT2D individuals.

Differences in cold and drought tolerance of high arctic and sub-arctic populations of Megaphorura arctica Tullberg 1876 (Onychiuridae: Collembola).

The springtail Megaphorura arctica (Onychiuridae: Collembola) inhabits the arctic and sub-arctic parts of the northern hemisphere where it on a seasonal basis will be exposed to severe cold and desiccating conditions. In the present study we compared how traits of stress resistance differed between two populations of M. arctica that were collected at a high arctic site (Spitsbergen) and a sub-arctic site (Akureyri, Iceland) with contrasting thermal environments. In addition we investigated how cold and desiccation affected the phospholipid fatty acid composition of M. arctica from Spitsbergen. The springtails from Spitsbergen were the most cold tolerant and this was linked to an almost three times higher level of trehalose accumulation during cryoprotective dehydration (15% and 5% of tissue dry weight in the Spitsbergen and Iceland populations, respectively). Although cryoprotective dehydration is intimately related to desiccation stress it was shown that M. arctica had a higher mortality when dehydrated over ice (-10 or -20 degrees C) than when dehydrated at temperatures above 1 degrees C. Thus, survival was lower after exposure to -10 degrees C than after exposure to a relative humidity of 91.2% RH at +1 degrees C although both treatments led to the same level of dehydration. Exposure to both cold (-10 and -20 degrees C) and desiccation at +1 degrees C caused significant changes in the phospholipid fatty acid composition with some similarities. These changes included a decrease in average chain length of the fatty acids due primarily to an increase in the phospholipid fatty acids 16:0 and a decrease in 18:3 and 20:4 omega6.

Freeze tolerance in Aporrectodea caliginosa and other earthworms from Finland.

Earthworms that live in subarctic and cold temperate areas must deal with frost even though winter temperatures in the soil are often more moderate than air temperatures. Most lumbricid earthworms can survive temperatures down to the melting point of their body fluids but only few species are freeze tolerant, i.e. tolerate internal ice formation. In the present study, earthworms from Finland were tested for freeze tolerance, and the glycogen reserves and glucose mobilization (as a cryoprotectant) was investigated. Freeze tolerance was observed in Aporrectodea caliginosa, Dendrobaena octaedra, and Dendrodrilus rubidus, but not in Lumbricus rubellus. A. caliginosa tolerated freezing at -5 degrees C with about 40% survival. Some individuals of D. octaedra tolerated freezing even at -20 degrees C. Glycogen storage was largest in D. octaedra where up to 13% of dry weight consisted of this carbohydrate, whereas the other species had only 3-4% glycogen of tissue dry weight. Also glucose accumulation was largest in D. octaedra which was the most freeze-tolerant species, but occurred in all four species upon freezing. It is discussed that freeze tolerance may be a more common phenomenon in earthworms than previously thought.

Geographic variation for climatic stress resistance traits in the springtail Orchesella cincta.

Multiple traits of stress resistance were investigated in the epedaphic springtail Orchesella cincta. Second generation adults from five laboratory populations were compared with respect to resistance to extreme temperatures and desiccation, and traits relevant to climatic adaptation. Populations were collected along a 2000-km latitudinal gradient ranging from Denmark to southern Italy and reared under the same standard laboratory conditions. Traits investigated were resistance to high and low temperature, desiccation resistance, body size and water loss rate (WLR). Results showed genetically based differences in resistance to high and low temperature, desiccation, WLR, water pool and body size between populations. Individuals from the most northern population had the highest desiccation-and cold shock resistance, and the lowest heat shock resistance. Females were significantly more desiccation resistant than males. The results of cold shock resistance showed a positive increase with lowest environmental temperature recorded at the sites of population origin, whereas heat shock resistance showed a positive increase with highest recorded temperature at the sites of population origin. Desiccation resistance increased towards the most southern and northern population, suggesting that both low and high temperature extremes affect desiccation resistance. Body mass, water pool and WLR showed interpopulation as well as sex specific variation. This provides evidence for geographical variation in stress resistance of springtails related to climatic conditions.

The influence of nonylphenol on life-history of the earthworm Dendrobaena octaedra Savigny: linking effects from the individual- to the population-level.

We conducted a study to look at the effects of nonylphenol (NP) on the life-history of the parthenogenetic earthworm, Dendrobaena octaedra. During a 196-day study, we observed that the growth rate of juveniles and the percentage of worms producing cocoons were the only traits significantly affected by NP, while the total number of cocoons produced was marginally affected. Despite some fairly large changes in the average values of individual life-history traits caused by NP, the effects were difficult to detect statistically due to large interindividual variability. A declining trend was observed for population growth rate (lambda) with increasing NP concentration, but the decline was not statistically significant. The percent reduction in lambda was less than the percent reduction in the most sensitive life-history trait (fecundity). An elasticity analysis showed that lambda was more sensitive to changes in survival than to changes in reproductive traits. However, neither juvenile nor adult survival were affected by NP, and decomposition analysis showed that the minor changes in lambda were mainly caused by effects of NP on time to first reproduction, time between reproduction events and fecundity. The present study suggests that extrapolation from laboratory studies to population effects in the field may be greatly enhanced by combining ecotoxicological and demographic methods.

Sublethal soil copper concentrations increase mortality in the earthworm Aporrectodea caliginosa during drought.

Simultaneous effects of drought and a sublethal concentration of copper on the earthworm Aporrectodea caliginosa were investigated in the laboratory. Experiments were performed with exposure to 150 mg Cu kg(-1) dry soil and different levels of drought during a 3-wk period. Soil water potentials from pF 1.5 (wet) to pF 5 (very dry) were obtained. The soil water potential resulting in 50% mortality was significantly reduced from pF 4.48 in worms not exposed to copper to pF 4.09 in copper-exposed worms, thus demonstrating synergy-like effects of drought and copper. Development of estivation cells was significantly depressed in copper-exposed worms compared to worms not exposed to copper. For all drought levels (except the highest, where 100% mortality occurred), copper-exposed earthworms with no estivation cells had more than twice as high mortality and, at severe drought exposure, also lower water content than those which had developed the estivation cells. With increasing drought level, the whole-body burden of copper increased from about 40 microg Cu g(-1) dry weight to about 90 microg Cu g(-1). When the worms were exposed to drought, the osmolality in their body fluids increased. This was due to a greater concentration of already existing solutes resulting from extensive loss of water, and not to mobilization or synthesis of additional solutes.

Freeze or dehydrate: only two options for the survival of subzero temperatures in the arctic enchytraeid Fridericia ratzeli.

Hygrophilic soil animals, like enchytraeids, overwintering in frozen soil are unlikely to base their cold tolerance on supercooling of body fluids. It seems more likely that they will either freeze due to inoculative freezing, or dehydrate and adjust their body fluid melting point to ambient temperature as has been shown for earthworm cocoons and Collembola. In the present study we tested this hypothesis by exposing field-collected adult Fridericia ratzeli from Disko, West Greenland, to freezing temperatures under various moisture regimes. When cooled at -1 degrees C min(-1) under dry conditions F. ratzeli had a mean temperature of crystallisation ( T(c)) of -5.8 degrees C. However, when exposed to temperatures above standard T(c) for 22 h, at -4 degrees C, most individuals (90%, n= 30) remained unfrozen. Slow cooling from -1 degrees C to -6 degrees C in vials where the air was in equilibrium with the vapour pressure of ice resulted in freezing in about 65% of the individuals. These individuals maintained a normal body water content of 2.7-3.0 mg mg(-1) dry weight and had body fluid melting points of about -0.5 degrees C with little or no change due to freezing. About 35% of the individuals dehydrated drastically to below 1.1 mg mg(-1) dry weight at -6 degrees C, and consequently had lowered their body fluid melting point to ca. -6 degrees C at this time. Survival was high in both frozen and dehydrated animals at -6 degrees C, about 60%. Approximately 25% of the animals (both frozen and dehydrated individuals) had elevated glucose concentrations, but the mean glucose concentration was not increased to any great extent in any group due to cold exposure. The desiccating potential of ice was simulated using aqueous NaCl solutions at 0 degrees C. Water loss and survival in this experiment were in good agreement with results from freezing experiments. The influence of soil moisture on survival and tendency to dehydrate was also evaluated. However, soil moisture ranging between 0.74 g g(-1) and 1.15 g g(-1) dry soil did not result in any significant differences in survival or frequency of dehydrated animals even though the apparent wetness and structure of the soil was clearly different in these moisture contents.

Effects of starvation and body mass on drought tolerance in the soil collembolan Folsomia candida.

The effects of starvation and body mass on drought tolerance in Folsomia candida were investigated. Starvation for up to 6 weeks did not reduce tolerance to drought (98.2% RH) compared to a nonstarved control group. Animals starved for 1, 2 or 6 weeks prior to drought exposure showed no systematic differences in the accumulation of sugars and polyols (SP). In all groups exposed to drought SP constituted 9-13% of dry weight and was distributed in myoinositol, glucose and a third unidentified compound. At 97.3% RH large individuals (9 weeks old) survived better than small individuals (2 or 3 weeks old). However, no correlation was found between body mass and drought tolerance at relative humidities above 97.3% RH. The results suggest that starvation for ecologically relevant periods of time does not impair the ability to produce desiccation-protective SP in F. candida, and that both small and large life stages are well adapted to dry soil conditions.

Geographic variation of freeze-tolerance in the earthworm Dendrobaena octaedra.

Freeze-tolerance and some of the underlying biochemical defence mechanisms in the earthworm Dendrobaena octaedra was investigated. Survival after slow cooling to -2 degrees C, -4 degrees C, or -6 degrees C was analysed in D. octaedra from three geographic regions representing large differences in winter temperature (Denmark, Finland and Greenland). A large variation in freeze-tolerance between the three populations of D. octaedra was found. Earthworms from the northern populations (Finland and Greenland) tolerated lower temperatures (-6 degrees C) than earthworms from the Danish population (poor survival at -4 degrees C and -2 degrees C). In the Finnish population, freezing led to the production of high concentrations of glucose, which reached values much higher than controls (94 mg g(-1) vs. 2 mg g(-1) dry weight). Other potential cryoprotectants were not elevated after freezing. The Danish and Greenlandic populations had substantially lower mean glucose levels after freezing than the Finnish population (about 15 mg g(-1)). Danish earthworms rapidly frozen did not accumulate glucose, and did not survive freezing at -2 degrees C. Danish earthworms exposed to osmotic stress in Ringer's solutions, containing different concentrations of glycerol, showed significantly elevated glucose levels, but did not survive rapid freezing. It was determined if freezing had an influence on the reproduction of the earthworms. After warming to summer temperatures (15 degrees C), survivors of freezing produced viable cocoons. In a field experiment it was tested if natural acclimatization during autumn and winter months had an effect on freeze-tolerance in the Danish population. There was a significant increase of post-freeze survival during this period. The results of the freezing experiments are discussed in relation to the general ecology of D. octaedra.

Drought acclimation and lipid composition in Folsomia candida: implications for cold shock, heat shock and acute desiccation stress.

Many of the physiological adaptations evolved in terrestrial invertebrates to resist desiccation have also been shown to enhance the survival of low temperatures. In this study we have examined temporal changes in the physiology of the collembolan Folsomia candida during acclimation to mild desiccation stress (98.2% RH), and how physiological changes correlate with resistance to subsequent cold shock, heat shock and acute desiccation stress. Drought-acclimation increased the resistance to cold and acute drought but reduced the resistance to heat shock. The composition of membrane phospholipid fatty acids (PLFA) changed during acclimation resulting in a higher degree of unsaturation by the end of the 192-h acclimation period. This resembles typical membrane alterations seen in ectothermic animals exposed to cold. Only small changes were seen in the neutral lipid fraction. The temporal changes in cold resistance and drought resistance correlated well with changes in PLFA composition and accumulation of sugars and polyols ('cryoprotectives'). It is proposed that the drought-induced PLFA desaturation, combined with the membrane protecting accumulation of cryoprotectives, are important physiological adaptations providing tolerance to both desiccation and cold.

Effects and risk assessment of linear alkylbenzene sulfonates in agricultural soil. 3. Sublethal effects on soil invertebrates.

Sewage sludge applied to agricultural soils often contains considerable amounts of linear alkylbenzene sulfonates (LAS). Toxic effects of LAS on soil organisms should, therefore. be evaluated to ensure safe use of sewage sludge as a fertilizer. In this study, dose-response relationships for the toxicity of Na-LAS to six species of soil invertebrates (survival, reproduction, and growth) were established using a sandy, agricultural soil as test substrate. In general, toxic effects on reproduction and growth appeared when the concentration in soil exceeded 40 to 60 mg/kg. Reproduction was approximately fourfold more sensitive in earthworms and enchytracids than in springtails and mites. It is argued that this difference in sensitivity is related to the dependency of soil pore water, which is high in the annelids but comparatively low in the arthropods.

Effects and risk assessment of linear alkylbenzene sulfonates in agricultural soil. 4. The influence of salt speciation, soil type, and sewage sludge on toxicity using the collembolan Folsomia fimetaria and the earthworm Aporrectodea caliginosa as test organisms.

Sewage sludge applied to agricultural soils often contains linear alkylbenzene sulfonates (LAS) in the range of 1 to 10 g/kg dry weight, and their toxicity to relevant soil organisms should, therefore, be assessed to ensure safe use of sewage sludge as a fertilizer. Studies of LAS toxicity to soil organisms are few, and to our knowledge, factors that may influence the toxicity in the field have not been studied in detail. In this paper, we report on the influence of speciation of LAS in the test solution added to soil (soluble Na-LAS vs poorly soluble Ca-LAS or Mg-LAS), the influence of soil type, and the modifying effects of sludge amendment on the toxicity of LAS. These issues were investigated using reproduction of Collembola and growth of juvenile earthworms as test parameters. Speciation of the LAS added to test soil did not have any influence on toxicity for any of the test species. Likewise, in three different agricultural soils (sand, loam, and clay), we found almost equal toxicities. The LAS added to test soil in a sludge-water suspension was equally toxic as when it was added in an aqueous solution. However, anaerobic incubation for 7 and 14 d of the LAS-sludge suspension (with no decay of LAS) caused the toxicity to increase almost threefold in both collembolan and earthworm. The relationships between soil constituents, bioavailability, and toxicity are also discussed.

Effects and risk assessment of linear alkylbenzene sulfonates in agricultural soil. 5. Probabilistic risk assessment of linear alkylbenzene sulfonates in sludge-amended soils.

Linear alkylbenzene sulfonates (LAS) can be found in high concentrations in sewage sludge and, hence, may enter the soil compartment as a result of sludge application. Here, LAS may pose a risk for soil-dwelling organisms. In the present probabilistic risk assessment, statistical extrapolation has been used to assess the risk of LAS to soil ecosystems. By use of a log-normal distribution model, the predicted no-effect concentration (PNEC) was estimated for soil fauna, plants, and a combination of these. Due to the heterogeneous endpoints for microorganisms, including functional as well as structural parameters, the use of sensitivity distributions is not considered to be applicable to this group of organisms, and a direct, expert evaluation of toxicity data was used instead. The soil concentration after sludge application was predicted for a number of scenarios and used as the predicted environmental concentration (PEC) in the risk characterization and calculation of risk quotients (RQ = PEC/PNEC). A LAS concentration of 4.6 mg/kg was used as the current best estimate of PNEC in all RQ calculations. Three levels of LAS contamination (530, 2,600, and 16,100 mg/kg), three half-lives (10, 25, and 40 d), and five different sludge loads (2, 4, 6, 8, and 10 t/ha) were included in the risk scenarios. In Denmark, the initial risk ratio would reach 1.5 in a realistic worst-case consideration. For countries not having similar sludge regulations, the estimated risk ratio may initially be considerably higher. However, even in the most extreme scenarios, the level of LAS is expected to be well beyond the estimated PNEC one year after application. The present risk assessment, therefore, concludes that LAS does not pose a significant risk to fauna, plants, and essential functions of agricultural soils as a result of normal sewage sludge amendment. However, risks have been identified in worst-case scenarios.