Fate of diuron and terbuthylazine in soils amended with two-phase olive oil mill waste

The addition of organic amendments to soil increases soil organic matter content and stimulates soil microbial activity. Thus, processes affecting herbicide fate in the soil should be affected. The objective of this work was to investigate the effect of olive oil production industry organic waste (alperujo) on soil sorption-desorption, degradation, and leaching of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and terbuthylazine [N2-tert-butyl-6-chloro-N4-ethyl-1,3,5-triazine-2,4-diamine], two herbicides widely used in olive crops. The soils used in this study were a sandy soil and a silty clay soil from two different olive groves. The sandy soil was amended in the laboratory with fresh (uncomposted) alperujo at the rate of 10% w/w, and the silty clay soil was amended in the field with fresh alperujo at the rate of 256 kg per tree during 4 years and in the laboratory with fresh or composted alperujo. Sorption of both herbicides increased in laboratory-amended soils as compared to unamended or field-amended soils, and this process was less reversible in laboratory-amended soils, except for diuron in amended sandy soil. Addition of alperujo to soils increased half-lives of the herbicides in most of the soils. Diuron and terbuthylazine leached through unamended sandy soil, but no herbicide was detected in laboratory-amended soil. Diuron did not leach through amended or unamended silty clay soil, whereas small amounts of terbuthylazine were detected in leachates from unamended soil. Despite their higher sorption capacity, greater amounts of terbuthylazine were found in the leachates from amended silty clay soils. The amounts of dissolved organic matter from alperujo and the degree of humification can affect sorption, degradation, and leaching of these two classes of herbicides in soils. It appears that adding alperujo to soil would not have adverse impacts on the behavior of herbicides in olive production.     

Single and combined application of two-phase olive mill waste and dairy cattle slurry to soil: Short-term effects on N and C dynamics

Abstract

Two-phase olive mill waste (TPOMW) and dairy cattle slurry (CS) are two organic materials with low economic value and limited potential for reutilization despite their high concentrations of nitrogen (N) and organic matter. A laboratory incubation for ca. 100 d was performed to assess the short-term N and carbon (C) dynamics in a soil amended with TPOMW, CS and a mixture of both materials in order to: (i) explore the potential benefits of mixing TPOMW with CS to promote mineral N immobilization and avoid nitrate leaching, and (ii) assess the potential for increased soil C stocks after TPOMW, CS or TPOMW+CS application. Our results clearly showed that the combined application of TPOMW+CS caused N immobilization; hence, it contributes to tying up the applied N, resulting in a decrease of critical N leaching, which is usually observed after CS application. No clear N mineralization was observed in the TPOMW+CS treatment during the incubation period.

It appears that an application of 30 Mg ha^?1 of TPOMW is enough to decrease net N mineralization from applied CS, as the C:N ratio of the mixture TPOMW+CS is 27. More than 40% of the TPOMW-derived C remained in the soil at the end of the experiment in treatments with single and combined application of TPOMW+CS, indicating that such materials have the potential to increase C stocks in soil. It can be concluded that a combined application of TPOMW+CS is of interest to maintain the CS-derived N in organic form during a longer time period and minimize risks of nitrate leaching, although further studies are necessary to define a better TPOMW:CS ratio which allows a proper plant N uptake.     

多菌灵重复施药对其持久性及土壤微生物群落功能多样性的影响

选择浙江大学华家池校区大棚蔬菜试验田,研究了多菌灵(以active ingredient,a.i.计)0.94、1.88和4.70 kg hm-2三种剂量重复施药对其持久性及土壤微生物功能多样性的影响。结果表明,第1次施药后,多菌灵在土壤中的降解速率分别为0.11、0.25、0.74 mg kg-1d-1;第4次施药后,多菌灵在土壤中的降解速率分别达到0.18、0.39、1.00 mg kg-1d-1。随着施药次数的增加,多菌灵的降解速率逐渐增大。初次施药后,土壤微生物群落AWCD值明显低于对照,土壤微生物群落的Shannon、Simpson和McIntosh指数也均低于对照水平。第4次施药后,三个处理土壤微生物群落的AWCD值、Shannon、Simpson和McIntosh指数均恢复到对照水平。     

Short-term effects in soil microbial community following agronomic application of olive mill wastewaters in a field of olive trees

Olive mill wastewater (OMW) creates a disposal problem. The large amounts generated, combined with the high phenol and chemical oxygen demand concentrations, are the main difficulties in finding a solution for the management of these wastewaters. We investigated the short-term effect of spreading OMW on the soil surface of an olive grove on the soil microbial communities. Analyse of ester-linked fatty acid methyl ester (EL-FAME) were used to assess variation in soil microbial community structure after agronomic application of OMW. EL-FAME analysis showed significant shifts of specific groups of fatty acids 30 days after application of OMW to a field of olive trees at rates of 0 (control soil), 30, 60, 100, and 150 m³ ha⁻¹ of OMW. In particular, the branched saturated fatty acids indicative of Gram-positive bacteria decreased and the unsaturated fatty acids commonly found in Gram-negative bacteria and fungi increased. The fungal/bacterial ratio measured increased significantly with increasing OMW. Lower cy19/18:1ω7c and cy17/16:1ω7c ratios were found in the amended soil than the control soil, and we interpret that as an indication that nutrient availability may be more limiting in the control soil. Similarly, the relative abundances of monounsaturated fatty acids increased with added OMW, and this is consistent with the presence of high substrate availability in OMW-treated soil. Principal Components Analysis of the FAME profiles showed discrimination between the control soil and OMW amended soil. Differences in fatty acid profiles between OMW-treated soil and control soil suggests that amendment of soil with OMW favors specific groups of organisms. To our knowledge, this is the first report of alterations in the FAME profile in soils due to agronomic application of OMW.     

Effects of olive oil mill wastewater on chemical,microbiological, and physical properties of soil incubated under four different climatic conditions

The objective of this study was to understand the degradation of the organic matter of olive mill wastewater (OMW) and its phytotoxic and water repellent effects in dependence on four different climatic conditions. We hypothesized that warm conditions with sufficient soil moisture ensure optimal biological activity and thus minimize negative effects of the OMW treatment. Therefore, OMW-treated soil was incubated for 60 days under four climatic conditions. During incubation, we monitored pH, contents of nitrate, manganese and phenolic compounds, soil respiration, soil water repellency, and δ¹³C. Additionally, calorific value and thermal stability of the soil organic matter at the beginning and end of incubation were determined. Soil samples of the wet-cold and moist-warm incubation were tested for phytotoxicity using a seed germination bioassay with Lepidium sativum. As a function of climatic conditions, positive and negative effects, e.g., addition of nutrients, phytotoxicity, and soil water repellency, were observed. Under dry-hot conditions, the soil was still water repellent after 60 days of incubation whereas the wet-hot, moist-warm, and wet-cold incubation show that soil would stay wettable if soil moisture before OMW treatment would be sufficient. Thus, the impact of OMW treatment on soil quality strongly depends on the environmental conditions which should favor an enhancement of microbial activity to minimize negative effects.     

Effect of processing conditions, prestorage treatment, and storage conditions on the phenol content and antioxidant activity of olive mill waste

The impact of two- and three-phase processing systems and malaxation conditions on phenol content (both total and individual phenols) and antioxidant capacity of laboratory-generated olive mill waste (OMW) was assessed. Two-phase olive processing generated a waste with higher phenol content and antioxidant capacity. Using the two-phase system, both malaxation time and temperature affected the phenol content and antioxidant capacity. The effects of different prestorage drying treatments on phenol content and antioxidant capacity were also compared. Air drying and drying at 60 degrees C resulted in a substantial decrease in the phenol content and antioxidant capacity. Drying at 105 degrees C and freeze-drying produced less degradation. The phenol content and antioxidant capacity of OMW stored at 4 degrees C and of OMW preserved by 40% w/w ethanol and 1% w/w acetic acid and stored at 4 degrees C were monitored for 30 days and compared with those of OMW stored at room temperature. None of these storage conditions could prevent the rapid decrease in phenolic concentrations and antioxidant capacity, which happened within the first 24 h.     

Bioactivity and analysis of biophenols recovered from olive mill waste

Biophenols have attracted increasing attention during the past few years due to their biological activities and natural abundance and are potential targets for the food and pharmaceutical industries. Olive mill waste (OMW) is rich in biophenols and typically contains 98% of the total phenols in the olive fruit, making value addition to OMW an attractive enterprise. The phenolic profile of OMW is complex, yet this complexity has not been fully exploited in the valorization of the waste. Most work on the bioactivity of OMW has focused on antioxidant and antimicrobial activities. The analytical techniques used to identify and quantify active biophenols are also reviewed.     

Nitrogen mineralization of silk waste applied to soil under aerobic conditions

Silk waste which is a byproduct of silk reeling consists mainly of silk proteins such as sericin and fibroin. Although silk waste has a high N content (164 g kg^-1) and low CjN ratio (2.16), net N mineralization in soil at 30°C under aerobic conditions was very slow (21.4% in 184 d). The N mineralization rate of silk waste applied to soil after hydrolysis with HCI was higher than that of untreated silk waste. The effect of hydrolysis with 0.2 M HCI for 60 min at 97°C on the net N mineralization for 56 d was twice as high as that with 1 M HCI for 60 min at 97°C. Molecular mass distribution of silk proteins shifted to the lower range by hydrolysis, whose effect with 1 M HCI was more pronounced than that with 0.2 M HCI. The content of the crystal region in silk protein was estimated to be approximately 45% based on the relationship between the reaction (acid hydrolysis) time and the weight of insoluble residues. X-ray diffraction patterns of these residues showed that the crystal structure persisted until at least 180 min after hydrolysis with 1 M HCI at 97°C. These results suggest that crystal regions and the scattered distribution in silk proteins inhibit the decomposition of silk waste in soil. Silk waste could thus be utilized as slow-release fertilizer.     

Influence of organic fertilizer application on pendimethalin volatilization and persistence in soil

Laboratory studies were undertaken to evaluate the influence of fertilizers on pendimethalin volatilization and persistence in soil. Various organic fertilizers such as liquid humic substances and urea were used at doses of 100 L/ha or 170 kg of N/ha, respectively. Herbicide residues were determined in air, soil solution, and soil samples by GC-ECD; the recovery of pendimethalin from spiked fertilized or control samples was found to be 81-103%. Liquid humic fertilizers increased pendimethalin dissipation during the first part of the assay, although 4 months after application, herbicide levels were similar to those observed in unfertilized soil. Fertilization of soil with urea decreased, in general, pendimethalin volatilization but increased herbicide levels in soil solution and persistence in soil, with a pendimethalin half-life approximately 70% higher than that found in unfertilized soil.     

Fate of isoxaflutole in soil under controlled conditions

Isoxaflutole (IFT, 5-cyclopropyl-1,2-oxazol-4yl-alpha,alpha,alpha-trifluoro-2-mesyl-p-tolyl ketone) is a new pre-emergence proherbicide used in maize and sugarcane. Its two main derivatives are a diketonitrile derivative, 2-cyano-3-cyclopropyl-1-(2-methanesulfonyl-4-trifluoromethylphenyl)propane-1,3-dione, called DKN, and a benzoic acid derivative, 2-methanesulfonyl-4-trifluoromethylbenzoic acid, called BA. Few data are available of the factors influencing the degradation of IFT in soil, and the purpose of the present work was to determine the relative importance of, and factors affecting, the degradation of IFT in soil. Experiments were conducted on five soils with distinct physicochemical characteristics, at different temperatures and moisture contents in biotic and abiotic conditions. The isomerization of IFT to DKN is rapid, increasing with higher moisture contents and higher temperatures. It depends strongly on pH and is governed by chemical processes. The degradation of DKN to BA appeared to be essentially due to the biological activity of the soil.     

Antioxidant and other biological activities of olive mill waste waters.

During olive oil production, large volumes of water are generated and subsequently discarded. Olives contain a variety of bioactive components, and some of them, according to their partition coefficients, end up in the water phase. The current investigation aimed at comparing different methods for the extraction of biologically active components of the olive mill waste waters (OMWW) and evaluating the in vitro antioxidant and anti-inflammatory activities of the resulting extracts. The results indicate that OMWW extracts are able to inhibit human LDL oxidation (a process involved in the pathogenesis of atherosclerosis) and to scavenge superoxide anions and hypochlorous acid at concentrations as low as 20 ppm. Finally, two of the three extracts also inhibited the production of leukotrienes by human neutrophils. The potency of the extracts depended on their degree of refinement: extracts containing only low molecular weight phenols were the most effective.     

Short-term effects of olive mill waste water (OMW) on chemical and biochemical properties of a semiarid Mediterranean soil

Olive mill waste water (OMW), a by-product of the olive mill industry, is produced in large amounts in Mediterranean countries. Olive mill waste water contains a high organic load, substantial amounts of plant nutrients but also several compounds with recognized toxicity towards living organisms. Moreover, OMW may represent a low cost source of water. Thus, the use of OMW for soil fertigation is a valuable option for its disposal, provided that its impact on soil chemical and biochemical properties is established. Investigations were performed on the short-term influence of OMW on several chemical and biochemical properties of a soil from a continental semi-arid Mediterranean region (Morocco). The soil was amended with 0, 18 and 36 ml 100 g⁻¹ soil of OMW (corresponding to a field rate of 0, 40 and 80 m³ ha⁻¹, respectively) and changes in various functionally related properties such as microbial biomass, basal respiration, extractable C and N, and soil hydrolases and oxido-reductases activities were measured over time. The variations of the main physical and chemical properties as well as the residual phytotoxicity of OMW amended and non-amended soils as assessed by tomato seed germination tests were also monitored. Temporary and permanent changes in several chemical and biochemical soil properties occurred following OMW application, thus being these properties varied in sensitivity to the applied disturbance. A sudden increase of total organic C, extractable N and C, available P and extractable Mn and Fe contents were measured. Simultaneously, a rapid increase of soil respiration, dehydrogenase and urease activities and microbial biomass (at 14 day incubation) of OMW amended soils occurred. In contrast, the activities of phosphatase, β-glucosidase, nitrate reductase and diphenol oxidase decreased markedly. The soil became highly phytotoxic after OMW addition (large decline of soil germination capability), mainly at 80 m³ ha⁻¹ OMW. After 42 days' incubation, however, a complete recovery of the soil germination capability and a residual phytotoxicity of about 30% were observed with 40 and 80 m³ ha⁻¹ OMW, respectively. These findings indicate that the impact of OMW on soil properties was the result of opposite effects, depending on the relative amounts of beneficial and toxic organic and inorganic compounds present. The toxic compounds contained in OMW most likely counteracted the beneficial effect of organic substrates provided, which promoted the growth and activity of indigenous microorganisms.     

Comparison of the persistence of atrazine and metolachlor under field and laboratory conditions

A study was carried out in a loamy soil to evaluate the degradation of atrazine and metolachlor under laboratory-controlled and field-variable conditions as a function of temperature and soil moisture content. In laboratory trials, metolachlor showed fast degradation, with half-lives from 100 to 5.7 days in a temperature range from 5 to 35 degrees C at 100% of field capacity, whereas in the same conditions the degradation rate of atrazine was relatively slow, with half-lives from 407 to 23 days. Modeling of laboratory degradation data to predict field persistence was carried out. Field persistence of atrazine and metolachlor was measured in the same soil during the corn growing seasons in 1993, 1994, and 1996. In the three years the mean half-dissipation times for atrazine and metolachlor were 36 and 21 days, respectively. Calculations from model equations gave acceptable prediction of field dissipation of both herbicides. Limitations and perspectives of employed modelization procedure are discussed.     

控制条件下水肥耦合对黄泥田还田秸秆腐解及土壤碳转化的影响

【目的】研究秸秆还田后不同水温和肥剂管理措施下土壤碳素转化特征。【方法】以华中双季稻区低产水稻土黄泥田为供试材料,模拟早稻和晚稻秸秆还田的田间环境,在实验室控制条件下,开展了两种温度环境中(15℃、35℃)不同水分(40%和100%最大田间持水量,即40%WHC、100%WHC)、配施氮肥类型(尿素、猪粪即U、M)、以及促腐菌剂添加对秸秆腐解效果及其过程中土壤碳素转化影响的研究。对水稻秸秆腐解过程中土壤CO2释放量、以及土壤可溶性有机碳(DOC)和总有机碳(TOC)含量在105天培养周期内变化特征进行动态监测分析。【结果】两种温度环境中整个培养周期内,各处理的CO2释放速率和释放总量通常表现为100%WHC-M100%WHC-U40%WHC-M40%WHC-U,即猪粪优于尿素的规律,而不论配施何种氮肥都存在100%WHC40%WHC(P0.01)的现象,同时40%WHC条件下辅施菌剂可显著提升CO2释放量;与此相反,两种温度环境下DOC含量都表现为40%WHC-M40%WHC-U100%WHC-M100%WHC-U(后两者差异小),即40%WHC条件下DOC含量显著高于100%WHC(P0.05),且配施猪粪处理优于配施尿素处理,但这两种氮肥处理间差异随培养时间延长而减小;以CO2-C释放量计算0 7 d、0 28 d、0 105 d内物料分解率,结果表明,35℃时100%WHC-U的处理中物料分解最快,15℃时40%WHC-M的处理中物料分解最慢。与之对应,105 d内TOC含量和净增量则在35℃时100%WHC-U的处理中最小(P0.01),而在15℃时40%WHC-M的处理中最大(P0.01);TOC的净增量和净损失量在相同温度条件下,尤其试验前期不同水分(P0.01)、氮素(P0.05)间均存在显著差异,且促腐菌剂添加普遍减小TOC含量;培养周期内所有处理的CO2释放速率与DOC含量间存在显著相关(P0.05)。【结论】水分状况对碳素的转化存在极大影响,其次是氮肥类型,且氮肥的影响作用随秸秆还田时间的延长而减弱;高湿条件更利于促进秸秆腐解,但导致土壤DOC含量较低,TOC的固持量也较少,而配施猪粪则可促进土壤DOC含量的提升及TOC的固持;促腐菌剂添加可促进秸秆腐解,但由于40%WHC条件下显著激发了CO2的释放而不利于土壤固碳。因此在华中低产黄泥田双季轮作稻区,早稻还田时由于气温高周期短,建议保持100%WHC、辅施适量尿素、并配合添加秸秆腐解菌剂,侧重秸秆快腐;而晚稻还田时气温低周期长,建议保持40%WHC并辅施缓效猪粪,侧重土壤固碳。     

Nitrous oxide emission from animal manures applied to soil under controlled conditions

Animal manures may differ strongly in composition and as a result may differ in the emission of N₂O following application to soil. An incubation study was carried out to assess the effects of type of mineral N fertilizer and manure, application technique and application rate on N₂O emission from a sandy soil with low organic matter content. Fluxes of N₂O were measured 30 times over a 98-day period. The total N₂O emission from mineral N fertilizer ranged from 2.1 to 4.0% of the N applied. High emissions were associated with manures with high contents of inorganic N, easily mineralizable N and easily mineralizable C, such as liquid pig manure (7.3-13.9% of the N applied). The emission from cattle slurries ranged from 1.8 to 3.0% and that of poultry manures from 0.5 to 1.9%. The total N₂O emission during the experimental period tended to increase linearly with increasing N application rate of NH₄NO₃ and liquid pig manure. The N₂O emission from surface-applied NH₄NO₃ was significantly smaller than that following the incorporation of NH₄NO₃ in the soil. The N₂O emission from pig manure placed in a row at 5 cm depth was significantly higher than from surface-application and other techniques in which manure was incorporated in the soil. The results show that modification of the composition and application technique may be tools to mitigate emission of N₂O.     

Responsiveness of Kansas soil series to sulfur application under greenhouse conditions

Abstract

Soil series of extensive acreage were selected to evaluate their S‐supplying power under greenhouse conditions using alfalfa in one study and corn and grain sorghum as test crops in a second study. The soils were divided into two major groups by textural classification for statistical evaluations. The addition of sulfur significantly increased dry matter yields and sulfur content of the plant material on all soils through the course of these studies. Significant predictors of sulfur uptake include extractable SO₄‐S and organic matter. Organic matter was a significant predictor of the percent yield response above the check yields on soils receiving S applications using corn and grain sorghum as test crops. Based on this equation, yield response would be expected in this greenhouse study with an organic matter content of 2.6% or less.     

The fate of organic matter brought into soil by olive mill wastewater application at different seasons

Purpose

Application of olive mill wastewater (OMW) to soil may cause positive or negative effects. The present study aims at a better understanding of the fate of organic matter brought into soil by OMW application under different environmental conditions.

Materials and methods

Single OMW application to soil was conducted in spring, dry summer, summer with irrigation, and in winter. Two days and 18–24 months after the application, soil samples from two depths were analyzed for thermal soil organic matter (SOM) properties, total organic carbon, water-extractable dissolved soil organic carbon, and its specific ultraviolet absorbance at 254 nm.

Results and discussion

After winter and irrigated summer treatments, OMW was largely leached from the upper horizon within 2 days. Application in spring and summer dry initially increased the thermolabile fraction and the calorific value of SOM, however, in a different degree due to different transport, transformation, and immobilization mechanisms. At the long term, SOM content was still elevated after summer dry treatment. The reduction of the thermostable fraction in spring treatment indicates a priming effect of the labile OMW constituents.

Conclusions

Application in winter or with irrigation cannot be recommended for the investigated site. Under hot and dry conditions, SOM content increased most persistently due to stronger mineral-organic interactions. Favorable conditions for biodegradation during OMW application in spring reduced the effects on SOM quantity in the long term. However, a possible priming effect and the persistence of changes in thermal properties need to be further investigated for repeated applications.

     

Chemical and cellular antioxidant activity of phytochemicals purified from olive mill waste waters

The isolation and identification of a phytocomplex from olive mill waste waters (OMWW) was achieved. The isolated phytocomplex is made up of the following three phenolic compounds: hydroxytyrosol (3,4-DHPEA), tyrosol (p-HPEA) and the dialdehydic form of decarboxymethyl elenolic acid, linked with (3,4-dihydroxyphenyl)ethanol (3,4-DHPEA-EDA). The purification of this phytocomplex was reached by partial dehydration of the OMWW, followed by liquid-liquid extraction with ethyl acetate and middle pressure liquid chromatography (MPLC) on a Sephadex LH-20 column. The phytocomplex accounted for 6% of the total phenolic content of the OMWW. The phytocomplex and individual compounds were tested for antioxidant capacity by the oxygen radical absorbance capacity (ORAC) method. The ORAC phytocomplex produced 10,000 ORAC units/g dry weight, whereas the cellular antioxidant activity, measured by the cellular antioxidant activity in red blood cell (CAA-RBC) method, demonstrated that the phytocomplex and all of the components are able to permeate the cell membrane thus exhibiting antioxidant activity inside the red blood cells. Our phytocomplex could be employed in the formulation of fortified foods and nutraceuticals, with the goal to obtain substantial health protective effects due to the suitable combination of the component molecules.     

Turnover of microbial tissue in soil under field conditions

The microbial population of a Brown Chernozemic soil was labelled in situ by adding ¹⁴C-glucose and ¹⁵NH₄¹⁵NO₃ to the plow layer. The loss of ¹⁴C, nitrogen immobilization-mineralization reactions, bacterial numbers (plate count, direct count) and fungal hyphal lengths were determined periodically throughout the growing period in amended and unamended microplots and in the surrounding field soil. After 5 days, 90 per cent of the labelled N occurred in the organic form with little subsequent mineralization. Of the labelled C added, 63, 56 and 39 per cent, remained in the soil after 3, 14 and 104 days, respectively.The ratio of fungal C to bacterial C increased as soil moisture decreased. Viable (plate count) and total numbers of bacteria in samples from unamended plots and field soil were significantly correlated with each other and with soil moisture. Fungal hyphal lengths from amended soil were also significantly related to moisture but the rate of loss of ¹⁴C and mineralization of ¹⁵N were not. The synthesized microbial material (tissue and metabolites) exhibited a high degree of stability throughout the study. The half-life of labelled C remaining in the soil after 30 days was calculated to be 6 months compared to only 4 days for the added glucose C. The amount of energy used for maintenance by the soil population under field conditions was calculated from measurements of biomass C, respired labelled C and respired soil C.     

Bioaugmentation and biostimulation effects on PAH dissipation and soil ecotoxicity under controlled conditions

The degradation of spiked anthracene (ANT), pyrene (PYR) and benzo[a]pyrene (B[a]P) in soil (3000 mg ∑ 3 PAHs kg⁻¹ dry soil) was studied in aerobically incubated microcosms for 120 d. The applied treatments aimed at enhancing PAH removal from the heavily contaminated soils are: (i) bioaugmentation by adding aged PAH-contaminated soil (ACS) containing activated indigenous degraders; and (ii) combined bioaugmentation/biostimulation by incorporating sewage sludge compost (SSC) and decaying rice straw (DRS). The adopted treatments produced higher PAH dissipation rates than those observed in unamended PAH-spiked soils, especially for ANT and PYR in the presence of DRS or ACS (>96%). However, B[a]P was the most recalcitrant hydrocarbon to biodegradation. Extracellular enzyme investigation revealed the existence of ligninolytic activities in all soil treatments, including control but no relationship could be found with PAH dissipation. The ecotoxicological assessment indicated that regardless of applied treatment, PAH-spiked soils were chronically lethal to ostracod Heterocypris incongruens and confirmed the sensitivity of the microcrustacean to the concomitant presence of these three hydrocarbons. Lettuce root elongation inhibition was correlated with PAH level but the presence of SSC conferred a strong phytotoxic capacity to PAH-spiked soils. DRS amendment may constitute a cost-effective alternative for hydrocarbon bioremediation as it has impacted positively on soil microbial activity and enhanced PAH removal with no apparent changes in soil physico-chemical properties.