Different enantioselective degradation of pyraclofos in soils

This study investigated the enantioselective degradation behavior of pyraclofos in three soils (NC, HZ, and ZZ) under native and sterilized conditions. The absolute configuration of pyraclofos enantiomers has been determined by the combination of experimental and calculated electronic circular dichroism spectra. S-(+)- and R-(-)-Pyraclofos were separated and determined on a cellulose tri-(4-chloro-3-methylphenylcarbamate) (Lux Cellulose-4) chiral column by reversed-phase high-performance liquid chromatography-tandem mass spectrometry. Pyraclofos enantiomers were configurationally stable in three soils and no interconversion was observed during the incubation of enantiopure S-(+)- or R-(-)-pyraclofos under native conditions. The enantioselective degradation behavior of chiral pyraclofos was dramatically different in three soils under native conditions, with half-lives (t(1/2)) of pyraclofos in NC, HZ, and ZZ soils of 2.6, 13.4, and 7.8 days for S-(+)-pyraclofos and 9.2, 9.3, and 8.2 days for R-(-)-pyraclofos. Compared to the half-lives (t(1/2)) of rac-pyraclofos of 21.5, 55.9, and 14.4 days in sterilized NC, HZ and ZZ soils, the degradation velocity was greatly improved in native soils, indicating that degradation was greatly attributed to microbially mediated processes in agricultural cultivating soils.     

Enantiomeric resolution and biotoxicity of methamidophos

Despite the fact that the biological processes of chiral pesticides are enantioselective, the biotoxicity of methamidophos with respect to enantioselectivity has so far received limited research. In this study, the enantiomeric separation and biotoxicity of the two enantiomers of methamidophos were investigated. Successful enantioseparation of methamidophos using high-performance liquid chromatography on a Chiralcel OD column was achieved. As indicated by the optical rotation and circular dichroism detection, (+)-methamidophos was eluted prior to (-)-methamidophos. The t test at the 95% level of confidence indicated significant differences between the enantiomers in their in vitro inhibition toward acetylcholinesterases of bovine erythrocytes and Electrophorus electricus and in vivo acute aquatic toxicity to Daphnia magna. The in vitro assays showed that (-)-methamidophos was about 8.0-12.4 times more potent to the enzymes than its (+)-form. In contrast, the (+)-enantiomer was 7.0 times more toxic to D. magna in 48 h tests. The toxicity of racemic methamidophos was intermediate in both in vitro and in vivo bioassays. These results suggest that the biotoxicity of chiral OPs to nontargeted organisms is enantioselective and therefore should be reevaluated with their pure enantiomers.     

多氯联苯（PCB_（153）与PCB_（28））对大型溞的毒性效应研究

选用大型溞作为受试生物,探讨多氯联苯（PCB153与PCB28）对浮游动物的急性和慢性毒性反应,初步评价多氯联苯（PCBs）对浮游动物的毒害效应。急性毒性试验中,PCB28和PCB153对大型溞的48h-LC50分别为27.08μg·L-1和579.16μg·L-1。实验表明,大型溞对PCB28的敏感性高于对PCB153的敏感性。慢性毒性试验显示,PCB28和PCB153对大型溞的生长、生殖均有不利影响,PCB28的影响表现为随浓度的升高,生长和生殖抑制效应加强;PCB153对大型溞生长的影响表现为随浓度升高而抑制效应增强,但其对大型溞的繁殖则表现为低浓度抑制而高浓度促进的现象虼耍团ǘ榷嗦攘剑≒CB153、PCB28）长期暴露的潜在毒性和高浓度多氯联苯的急性毒性在环境生态安全研究中值得高度关注。     

Single and joint acute toxicity of isocarbophos enantiomers to Daphnia magna

Although enantioselectivity in the toxicity of chiral pesticides has received considerable attention over recent years, how coexisting enantiomers interact with each other during their toxic action remains unknown. In this study, we attempted to resolve the enantiomers of a chiral organophosphate insecticide, isocarbophos, and investigated the acute toxicity of individual enantiomers and various enantiomer mixtures. Baseline enantiomeric separation of isocarbophos was achieved on a Chiralcel OD column with the mobile phase of n-hexane/isopropanol (90/10, v/v) at a flow rate of 0.8 mL/min. The resolved enantiomers were differentiated by their responses on a circular dichroism detector. The median lethal concentrations (LC 50) of racemate, (+)-enantiomer, and (-)-enantiomer of isocarbophos toward Daphnia magna were 13.9, 7.08, and 353 microg/L, respectively, after 48 h of static exposure, displaying a 50-fold difference between the enantiomers. Toxic unit (TU) analysis was employed to evaluate the joint toxicity of isocarbophos enantiomer mixtures. The calculated TU mix for the acute toxicity (48 h test) of various binary mixtures ranged from 0.83 to 1.04, suggesting a mode of additive effect. Further evaluation of available literature data for chiral organophosphorus insecticides showed that the joint toxicity of enantiomers may be additive, synergistic, and antagonistic. Therefore, when significant enantioselectivity exists for a chiral pesticide, it is important to also evaluate the interaction of enantiomers in the joint toxicity effect when enantiomers are present in a mixture.     

Enantiomeric resolution and growth-retardant activity in rice seedlings of uniconazole

The increasing application of chiral pesticides has enhanced interest in their enantioselectivity. However, little relevant information is currently available for enantioselective activity of chiral plant growth regulators. In an attempt to screen active enantiomers of uniconazole, this work investigated enantiomeric separation and the enantioselective effect of uniconazole on the growth of rice seedlings and cyanobacteria. Baseline resolution of uniconazole enantiomers was achieved on a Chiralpak AD column by chiral high-performance liquid chromatography (HPLC). The relationship among circular dichroism (CD), optical rotation (OR), and absolute configuration was successfully established by coupling of CD and OR detection. The t test at the 95% level of confidence indicated significant differences between the enantiomers in their retardant activity toward growth of rice seedlings and stimulation effect on growth of cyanobacteria, the natural biofertilizers in rice paddy fields. The S-(+)-enantiomer was more active than the R-(-)-enantiomer in retarding growth of rice seedlings and stimulating growth of Microcystis aeruginosa . This special enantiomeric selectivity was further elucidated by probing the binding mode of enantiomers to gibberellin (GA) 20-oxidase by molecular docking. The S-(+)-enantiomer was found to bind tightly with GA 20-oxidase. The results suggested that the S-(+)-enantiomer instead of a racemate of uniconazole should be used to improve rice seedling quality.     

Enantioselective degradation and ecotoxicity of the chiral herbicide diclofop in three freshwater alga cultures

Aryloxyphenoxypropanoates are a class of chiral herbicides. They have a pair of enantiomers, only the R(+) form of which is herbicidally active. Diclofop, the model compound of these herbicides, is commercialized as the racemate of the ester form, diclofop-methyl, consisting of a 1:1 mixture of the enantiomers. This study evaluated the enantioselectivity in aquatic toxicity and biodegradation of diclofop and diclofop-methyl. The herbicidally inactive S(-) enantiomers of both diclofop-methyl and diclofop were similar to or higher than the corresponding R(+) forms in toxicity to algae, depending on specific species. Although no enantiomeric conversion occurred for diclofop-methyl and diclofop, the difference in the enantioselective degradation of these herbicides observed in algae cultures suggested that their application forms were an important factor determining their enantioselective environmental behavior. The cell permeability and heat treatment of algae revealed that the enantioselective degradation of diclofop in algae cultures was governed primarily by the facilitated uptake by algae, whereas the enantioselective toxicity was primarily governed by the passive uptake. These results suggested that the acute toxicity test such as the 96 h EC 50 was insufficient to assess the ecological risk of chiral pesticides because of the differential degradation as well as possibly differential action sites of enantiomers. From this study, it was concluded that the enantioselective degradation and toxicity of chiral herbicides may result in their ecotoxicological effects being difficult to predict and that specific attention should thus be paid to currently used racemic pesticides as less active or inactive enantiomers may pose higher ecological risks.     

Enantiomeric differences in permethrin degradation pathways in soil and sediment

Chirality occurs widely in synthetic pyrethroids. Studies have shown significant differences in both aquatic toxicity and degradation rates between enantiomers from the same diastereomer of selected pyrethroids. To better understand chiral selectivity in biodegradation of pyrethroids, 14C-labeled permethrin was used to characterize enantiomeric differences in the formation of transformation intermediates in two soils and a sediment. Individual enantiomers of permethrin were spiked into soil and sediment samples, and transformation products were identified with known standards. Enantioselectivity was observed in most treatments when the dissipation of the parent enantiomers, the amount of intermediates and bound residues formed, and mineralization rates were compared between the enantiomers. The results show that all enantiomers of permethrin hydrolyzed rapidly and that the hydrolysis products were quickly further transformed. The direct hydrolysis products, cyclopropanic acid (Cl2CA), 3-phenoxybenzyl alcohol (PBalc), and 3-phenoxybenzoic acid (PBacid), were recovered at small percentages, ranging from 1 to 14% for Cl2CA and from 0.2 to 6% for PBalc and PBacid. The R-enantiomer of both cis- and trans-permethrin was mineralized more quickly than the S-enantiomer after hydrolysis. The degradation products from cis-permethrin were more persistent than those from trans-permethrin. As some transformation intermediates of permethrin may have greater acute and chronic toxicity than the parent compound, enantioselectivity in the formation of degradation intermediates may lead to different overall toxicities and merit further investigation. This study suggests that for chiral compounds, enantioselectivity may be reflected not only in the dissipation of the parent enantiomers but also in the kinetics of formation of intermediate transformation products.     

Toxicity of (+)- and (-)-gossypol to the plant pathogen,Rhizoctonia solani

The dimeric sesquiterpene gossypol occurs naturally in cottonseed and other parts of the cotton plant. Gossypol exists as enantiomers because of the restricted rotation around the central binaphthyl bond. The (-)-enantiomer is toxic to nonruminant animals while the (+)-enantiomer exhibits little, if any, toxicity to these animals. Developing cotton plants with low levels of the (-)-gossypol could expand the use of cottonseed as a feed source. Gossypol also may play a role in protecting the plant from pathogens. The relative toxicity of (+)- and (-)-gossypol to plant pathogens has not been reported. We measured the concentration of (+)- and (-)-gossypol in roots from cotton seedlings that were treated with the biocontrol agent Trichoderma virens that induces biosynthesis of gossypol and related terpenoids in cotton roots. (-)-Gossypol was the minor enantiomer in control and treated roots, but levels were slightly higher in roots from T. virens-treated seed. We also determined the toxicity of the gossypol enantiomers and the racemate to the seedling disease pathogen Rhizoctonia solani. The (+)- and (-)-enantiomers of gossypol and the racemate are equally effective in inhibiting growth of this pathogen. The lethal doses of the gossypols required to kill the pathogen appeared to be similar, but their toxicities are significantly less than those of related cotton and kenaf sesquiterpenes. The results indicate that altering the enantiomeric ratio in cotton roots will not adversely affect the resistance of seedlings to the seedling pathogen R. solani.     

Enantioselective separation and phytotoxicity on rice seedlings of paclobutrazol

The environmental significance of enantioselectivity in chiral insecticides and herbicides has been widely studied. However, little information is currently available on the enantioselective behavior of chiral plant growth regulators. In this study, paclobutrazol enantiomers were resolved and prepared by chiral high-performance liquid chromatography with a Sino-chiral OJ column. The relationship among absolute configuration, optical activity and circular dichroism of paclobutrazol enantiomers was established. The enantioselective behavior of paclobutrazol, including enantioselective effect of paclobutrazol on the growth of rice seedlings and cyanobacteria and enantioselective loss of paclobutrazol in rice seedling growth media, in rice culture system was studied. The (2S,3S)-(-)-enantiomer was almost 3.1 times more active than the (2R,3R)-(+)-enantiomer toward shoot growth as measured by 7 day EC50 values. Enantioselectivity could not be determined with respect to root growth of rice seedlings because a typical dosage response was not observed in the range of the concentrations studied. The dissipation of paclobutrazol in rice growth medium is not enantioselective. Enantiomers and diastereoisomer of paclobutrazol all facilitated the growth of cyanobacteria, which increase the effectiveness of rice biofertilizers. The (2S,3S)-(-)-enantiomer showed stronger stimulatory activity on Microcystis aeruginosa cyanobacteria than the (2R,3R)-(+)-enantiomer, whereas the latter was a more potent stimulator of Anabaena sp. growth. These observations indicate that application of the (2S,3S)-(-)-enantiomer of paclobutrazol and Microcystis aeruginosa in rice cultivation is a good strategy for improving rice seedling performance.     

Occurrence of (+)- and (-)-gossypol in wild species of cotton and in Gossypium hirsutum Var. marie-galante (Watt) Hutchinson

Gossypol occurs as a mixture of enantiomers in cottonseed. These enantiomers exhibit different biological activities. The (-)-enantiomer is toxic to animals, but it has potential medicinal uses. Therefore, cottonseed with >95% (-)-gossypol could have biopharmaceutical applications. The (+)-enantiomer shows little, if any, toxicity to nonruminant animals. Thus, cottonseed with >95% (+)-gossypol could be more readily utilized as a feed for nonruminants. The (+)- to (-)-gossypol ratio in commercial Upland (Gossypium hirsutum) cottonseed is usually about 3:2, whereas that in commercial Pima cottonseed (Gossypium barbadense) is approximately 2:3. Herein are reported the (+)- to (-)-gossypol ratios in the seed from 28 wild species of cotton (194 accessions), 94 accessions of G. hirsutum var. marie-galante, and 3 domesticated species (11 accessions). It was found that some or all of the accessions of Gossypium darwinii, Gossypium sturtianum, Gossypium areysianum, Gossypium longicalyx, Gossypium harknessii, and Gossypium costulatum produce an excess of (-)-gossypol but none >65%. At least one accession of Gossypium anomalum, Gossypium mustelinum, Gossypium gossypioides, and Gossypium capitis-viridis contained >94% (+)-gossypol. One of the 94 accessions of G. hirsutum var. marie-galante (i.e., no. 2469) contained 97% (+)-gossypol.     

Olive oil mill wastewater treatment using a chemical and biological approach

Olive oil mill wastewaters (OMW) are recalcitrant to biodegradation for their toxicity due to high values of chemical oxygen demand (COD), biological oxygen demand (BOD), and phenolic compounds. In the present study OMW, collected in southern Italy, were subjected first to a chemical oxidative procedure with FeCl3 and then to a biological treatment. The latter was performed in a pilot plant where mixed commercial selected bacteria, suitable for polyphenols and lipid degradation, were inoculated. The effect of treatments was assessed through COD removal, reduction of total phenols, and decrease of toxicity using primary consumers of the aquatic food chain (the rotifer Brachionus calyciflorus and the crustacean Daphnia magna). The results showed that the chemical oxidation was efficacious in reducing all parameters analyzed. A further decrease was found by combining chemical and biological treatments.     

重金属汞、镉和铬对明亮发光杆菌的生物毒性

以明亮发光杆菌（Photobacterium phosphoreum）T3变种作为毒性测试物种,测定了重金属Hg2＋、Cd2＋和Cr6＋的单一毒性;采用二次二因子回归通用旋转组合实验设计,研究了Hg2＋＋Cd2＋、Hg2＋＋Cr6＋和Cd2＋＋Cr6＋3种二元重金属混合物的联合毒性作用和主因子作用,建立了3个相应的数学模型。结果表明,与单一重金属Hg2＋、Cd2＋与Cr6＋相比,它们的二元混合物对明亮发光杆菌生物毒性的效应和强度完全不同;单一重金属Hg2＋、Cd2＋与Cr6＋对明亮发光杆菌的毒性有显著的正效应,毒性从大至小依次为Hg2＋、Cd2＋、Cr6＋,对明亮发光杆菌的EC50分别为0.044、6.05mg·L-1和30.65mg·L-1;3种二元重金属混合物对发光细菌的联合毒性作用也不同,总体上,Hg2＋与Cd2＋、Cd2＋与Cr6＋为加和作用,而Hg2＋与Cr6＋以拮抗作用为主。     

Evaluation of a Multi-species Test System for Assessing Acute and Chronic Toxicity of Sediments and Water to Aquatic Invertebrates: Effects of Pentachlorophenol on Daphnia magna and Chironomus prasinus (6 pp)

Background, Aims and Scope   Single-species toxicity tests are currently used as main tools for assessing effects in ecological risk assessments. Nevertheless, in higher-tier evaluations, alternative ecotoxicological methods can be required. Alternative methods should cover more realistic exposure conditions and/or additional species or endpoints. Water/sediment systems can be considered for covering additional exposure routes. A typical feature of water/sediment systems is the modification of exposure levels with time. The simultaneous exposure of different species within the same system can cover differences in sensitivity and relevance of exposure routes. The aim of this study was to develop a water/sediment test that could detect relevant effects on two selected species and explore the relevance of sediment and waterborne exposure routes. This alternative method may provide relevant information facilitating the design of microcosm and mesocosm studies.Methods   A multi-species water/sediment system was designed using two invertebrates: Chironomus prasinus a benthic detritivore invertebrate and Daphnia magna a pelagic filtering invertebrate was designed. Seven static water/sediments systems were built up: two controls and five treatments where sediments were spiked with NaPCP at nominal concentrations of 1.25, 2.5, 5, 10 and 20 mg/kg, respectively. Each system contained caged and free (unrestrained) Daphnia magna organisms to consider differences in the exposure route (through sediment and/or water column) and Chironomus prasinus organisms. Fate and partitioning of PCP within the water/sediment compartments were assessed. Acute (lethality) and chronic effects (reproduction) for Daphnia magna were monitored after 48 h and 16 days of exposure, respectively. Adult emergence and oviposition success of Chironomus prasinus were monitored at the end of test (16 days).Results and Discussion   Mortality and reproduction inhibition of Daphnia magna occurred at the two higher doses, corresponding to maximum measured PCP water concentrations of 1.95 and 0.746 mg/l, respectively. Chironomus prasinus was less sensitive to PCP than Daphnia magna. Concentrations inhibiting reproduction and provoking almost 100% adult mortality in D. magna only reduced slightly the emergence and reproduction of chironomids. The experimental design focussed on suitability of the system for assessing simultaneously assessing effects on D. magna and C. prasinus instead of calculations of toxicity endpoints for PCP. The results indicate that this experimental design can be useful to the field of sediment/aquatic toxicity testing, particularly through the comparison with single- species results. Assessment of relative contribution of two exposure routes for Daphnia magna and complementary chronic endpoints derived from two different species can be achieved. Another advantage is that differences in reproduction strategies of selected species (sexual vs. parthenogenetic) should permit one to detect mechanisms of action associated to with endocrine disrupters.Conclusion   The feasibility of a two-species test built-up in an artificial sediment/water system has been demonstrated. This experimental design represents a cost/effective test which can assess effects through water and sediment pathways and incorporates several relevant chronic endpoints in a single assay. Recommendation and Outlook   By building on the experience gained, improvements for further test designs are discussed. Test validation with a set of model chemicals will contribute to address the effectiveness of the test developed as comparing compared to single- species tests.     

Biogenetic studies in Mentha x piperita. 2. Stereoselectivity in the bioconversion of pulegone into menthone and isomenthone.

Mentha x piperita shoot tips and first leaf pairs were fed with aqueous solutions of different deuterium-labeled pulegone and various enantiomeric distributions. The essential oil was extracted by solid-phase microextraction and analyzed using enantioselective multidimensional gas chromatography/mass spectrometry. The genuine p-menthan-3-ones (-)-menthone and (+)-isomenthone as well as their labeled analogues were analyzed simultaneously. Both enantiomers of labeled pulegone were converted into the corresponding labeled p-menthan-3-ones by Mentha x piperita, indicating an unspecific reduction process. The generation of 4S- and 4R-configured p-menthan-3-ones differed in their stereoselectivities. Labeled (S)-pulegone was reduced by Mentha x piperita more rapidly rather than (R)-pulegone. From a comparison of labeled pulegone enantiomers the bioconversion preferrably led to 4S-configured diastereomers.     

Enantioselective degradation and chiral stability of malathion in environmental samples

The dissipation behaviors of the two enantiomers of the organophosphorus pesticide malathion (MA) in environment samples were elucidated using a normal-phase high-performance liquid chromatography with a cellulose-tris(3,5-dimethylphenylcarbamate) (CDMPC) chiral column. A validated chiral residue analysis method in soil and water was established; the average recoveries for the two enantiomers were 88-102% in soil and 81-99% in water. Racemic and enantiopure R-(+)- and S-(-)-MA were incubated in five soil and water systems. The results of the degradation of racemate in all of the environment samples showed the inactive S-(-)-enantiomer degraded more rapidly than the active R-(+)-enantiomer, resulting in a relative enrichment of the R-form. Moreover, when the enantiopure S-(-)- and R-(+)-MA were incubated in three well-chosen soil and water samples, respectively, inversion from one enantiomer to another was found, indicating that using the optically pure enantiomer will not help to increase the bioactivity and reduce the environmental pollution.     

Effects of dissolved organic matter on permethrin bioavailability to Daphnia species

Synthetic pyrethroids are widely used insecticides in both agricultural and urban environments. Recent studies show frequent appearances of pyrethroid residues in runoff effluents and sediments, which stimulated concerns over the potential ecotoxicological implications. Pyrethroids are known to have two contrasting characteristics, high aquatic toxicity and strong affinity for the solid phase, that may negate the actual toxicity in a multiphased system. This study evaluated the effect of dissolved organic matter (DOM) on the pyrethroid uptake by and acute toxicity to water-column invertebrates using permethrin as a model compound. During the bioassays, the freely dissolved permethrin concentration was simultaneously measured using poly(dimethylsiloxane) (PDMS) fibers as a biomimetic surrogate. The presence of DOM consistently decreased permethrin uptake and increased its LC(50). For instance, compared to the DOM-free treatment, the LC(50) of permethrin to Ceriodaphnia dubia in a pond water containing DOM at 10 mg L(-)(1) increased from 0.56 to 1.03 microg L(-)(1), whereas the bioaccumulation factor by Daphnia magna decreased by 56%. Permethrin accumulation on the PDMS fiber closely mimicked permethrin uptake by D. magna. Statistical analyses suggest that permethrin associated with DOM was completely unavailable to D. magna or C. dubia. The effect of DOM on permethrin bioavailability appeared to depend also on the source of the DOM. These results indicate that the inhibitory role of DOM should be considered in the development of toxicologically relevant water quality limits and in monitoring protocols for permethrin and other pyrethroids in runoff effluents and surface streams that ubiquitously contain DOM.     

More toxic and photoresistant products from photodegradation of fenoxaprop-p-ethyl

The photodegradation pathway of the commonly used herbicide fenoxaprop-p-ethyl (FE) was elucidated, and the effects of the photodegradation on its toxicity evolution were investigated. Under solar irradiation, FE could undergo photodegradation, and acetone enhanced the photolysis rates significantly. The same photoproducts formed under the irradiation of lambda > 200 nm and lambda > 290 nm through rearrangement, loss of ethanol after rearrangement, de-esterification, dechlorination, photohydrolysis, and the breakdown of the ether linkages. One of the main transformation products, 4-[(6-chloro-2-benzoxazolyl)oxy] phenol (CBOP), was resistant to photodegradation under the irradiation of lambda > 290 nm, and its photolysis rate was seven times slower than the parent under the irradiation of lambda > 200 nm. Among the metabolites, CBOP (48 h EC50 of 1.49-1.64 mg/L) and hydroquinone (48 h EC50 of 0.25-0.28 mg/L) were more toxic to Daphnia magna than the parent FE (48 h EC50 of 4.2-6.9 mg/L). Thus, more toxic and photoresistant products were generated from photolysis of the herbicide. Ecotoxicological effects of phototransformed products from pesticides should be emphasized for the ecological risk assessment of these anthropogenic pollutants.     

多杀菌素对小菜蛾及其天敌的毒力研究

研究评价多杀菌素(菜喜)对小菜蛾及其主要天敌的毒力结果表明,菜喜对小菜蛾具有很高的毒力和良好的田间防治效果,菜喜对青翅蚁型隐翅虫和菜蛾绒茧蜂具有直接杀伤作用,其1000倍稀释液24h使菜蛾绒茧蜂死亡率达62.2%,36h死亡率达88.7%,药液直接处理寄生蜂茧或饲喂均导致很高的死亡率,但对拟环纹狼蛛影响较小。多杀菌素对小菜蛾有很好的控制效果,但对小菜蛾天敌,特别是寄生蜂有相当的负面影响。     

Role of soil properties in sewage sludge toxicity to soil collembolans

Soil properties are one of the most important factors explaining the different toxicity results found in different soils. Although there is knowledge about the role of soil properties on the toxicity of individual chemicals, not much is known about its relevance for sewage sludge amendments. In particular little is known about the effect of soil properties on the toxicity modulation of these complex wastes. In addition, in most studies on sewage sludges the identity of the main substances linked to the toxicity and the influence of soil properties on their bioavailability remains unknown.In this study, the toxicity of a sewage sludge to the soil collembolan Folsomia candida was assessed in nine natural soils from agricultural, grassland and woodland sites, together with the OECD soil. Correlations between the relative toxicity of sludge for collembolans in the different soils and their physical and chemical soil properties were assessed in order to identify the main compounds responsible for the effects observed. Furthermore, the relationships between the toxic effects to collembolans and water-soluble ions released by sludge, pH and electric conductivity were also assessed, together with the modulating effects of soil properties.Sludge toxicity was directly linked to the water extractable ammonium, which explained most of the mortality of the collembolans, and part of the inhibition of reproduction. For the last endpoint, nitrite also contributed significantly to the inhibition observed. The varied levels in water extractable ammonium in the different soils at equal dosages seem to be, in turn, modulated by some soil properties. Higher organic carbon contents were associated with lower toxicity of sludge, both for survival and reproduction, probably related to its higher ammonium sorption capacity. In addition, for reproduction, increasing the C/N ratio and pH appeared to increase the toxicity, probably due to both the greater difficultly in nitrification and the known unsuitability of alkaline soils for this species.     

Cottonseed with a high (+)- to (-)-gossypol enantiomer ratio favorable to broiler production

This study was designed to evaluate the relative toxicity of (+)- and (-)-gossypol enantiomers in 0-3-week-old broilers. Treatments consisted of broiler starter diets formulated with either a glandless, which did not contain gossypol, a commercial glanded [62. 2% (+)-gossypol], or a glanded moco [83.2% (+)-gossypol] crushed cottonseed (CCS) (six replicates/treatment) plus a soybean meal negative control. Glandless cottonseed was mixed with the moco cottonseed (2.4% free gossypol) so that both the commercial glanded and moco glanded cottonseeds contained equivalent concentrations of free gossypol (2.0%). The cottonseed treatments were added at 5 and 10% of the diet. Body weights and feed conversions were determined weekly. Body weights and feed-to-gain ratios of broilers fed 5 and 10% glandless CCS and 5% moco CCS were not significantly different. Broilers receiving 10% commercial glanded CCS weighed significantly less than those subjected to all other treatments. Feed-to-gain ratios were significantly higher for broilers receiving 10% commercial glanded and 10% moco CCS as compared to 5% moco and glandless CCS, 10% glandless CCS, and control. Relative liver weights of birds receiving 10% moco CCS were significantly less than those of birds receiving 10% commercial CCS. The data clearly showed that broilers fed moco CCS containing a relatively high (+)- to (-)-gossypol enantiomer ratio performed better than broilers receiving commercial CCS with a lower (+)- to (-)-gossypol enantiomer ratio.