Background, aim and scope Salt efflorescences markedly contribute to the alteration and deterioration of building material, in this case the Villamayor Sandstone of the facades in the Old Town of Salamanca, Spain (United Nations Educational, Scientific and Cultural Organization world cultural heritage site). A better understanding of the mechanisms of salt formation and the involved elements would allow more precise measures in monument conservation. The magnesium which is required for the salt precipitation originates from selective processes of hydrolysis. The source of sulphate, however, is presently not as clear. Identifying the source of the sulphur was the main goal of this research. Isotope ratio measurement of δ³⁴S and δ¹⁸O was used to clarify the origins of Mg sulphate salts. Materials and methods A total of 56 Mg sulphate samples were collected in two different seasons (July and November 2005) from monuments of the Old Town of Salamanca. These sampled salt efflorescences were analysed for δ³⁴S and δ¹⁸O by mass spectrometry. A ‘dual-inlet' type by VG Isotech was used for δ³⁴S and continuous flow type Isoprime by GV Instruments for δ¹⁸O. Samples were measured in triplicates and standard material was analysed for quality control. Results δ³⁴S values range between 3.6‰ and 15.4‰ with a median value of 10.2‰ for the July samples and of 10.1‰ for November samples. The results of the sulphur ratios hint towards a bimodal distribution (with modes at δ³⁴S = 6‰ and 12‰) for winter samples, which is less obvious during summer. δ¹⁸O values range from 7.1‰ to 41.1‰. However, most values range from 7.1‰ to 20.8‰, whereas only few summer samples show outliers towards higher δ¹⁸O values. The median δ¹⁸O value for July samples is 15.5‰ and for November samples 14.6‰. Discussion The isotopic ratios of the analysed sulphate samples were compared with values of possible source materials. Sulphur sources in the case of Salamanca are barites from the Villamayor Sandstone itself, sea spray, sulphides from regional rocks, biogenic sulphur (soil, avian excreta), as well as sulphur from anthropogenic sources such as building materials (especially mortar) or traffic exhaust. Salamanca is a representative site for non-industrial cities with no heavy industry and thus, there are no significant SO₂ emissions from industry. Conclusions Based on the measured isotopic ratios, it was ascertained that more than one sole sulphur source is present. However, based on additional information about the source material and possible transport ways, some sources could be excluded whereas others only played a minor role. Finally, there is strong indication that the main sulphur source is atmospheric pollution and the exhaust emissions from vehicles in particular, while mortar as building material also contributes to a minor extent. The δ¹⁸O values support this hypothesis. Moreover, the reported δ¹⁸O values are a strong indicator of the secondary nature of the Mg sulphates. Isotope ratio measurement and especially the combined use of δ³⁴S and δ¹⁸O values have proven to be a good instrument in clarifying the origin of salt efflorescences on buildings. Recommendations and perspectives Further studies should investigate more closely the isotopic composition of atmospheric aerosols in Salamanca in order to get a more detailed knowledge about the main sulphur sources, as well as to quantify the relation between the isotopic values and the amount and mineralogical form of the salts.

Background, aim, and scope Anti-tumour agents and their metabolites are largely excreted into effluent, along with other pharmaceuticals. In the past, investigations have focused on the input and analysis of pharmaceuticals in surface and ground water. The two oxazaphosphorine compounds, cyclophosphamide and ifosfamide are important cytostatic drugs used in the chemotherapy of cancer and in the treatment of autoimmune diseases. Their mechanism of action, involving metabolic activation and unspecific alkylation of nucleophilic compounds, accounts for genotoxic and carcinogenic effects described in the literature and is reason for environmental concern. The anti-tumour agents cyclophosphamide (CP) and ifosfamide (IF) were not biodegraded in biodegradation tests. They were not eliminated in municipal sewage treatment plants. Degradation by photochemically formed HO radicals may be of some relevance only in shallow, clear, and nitrate-rich water bodies but could be further exploited for elimination of these compounds by advanced oxidation processes, i.e. in a treatment of hospital waste water. Therefore, CP and IF are assumed to persist in the aquatic environment and to enter drinking water via surface water. The risk to humans from input of CP and IF into surface water is not known. Materials and methods The local and regional, i.e. nationwide predicted environmental concentration (PEClocal, PECregional) of CP and IF was calculated for German surface water. Both compounds were measured in hospital effluents, and in the influent and effluent of a municipal treatment plant. Additionally, published concentrations in the effluent of sewage treatment plants and surface water were used for risk assessment. Excretion rates were taken into account. For a worst-case scenario, maximum possible ingestion of CP or IF by drinking 2 L a day of unprocessed surface water over a life span of 70 years was calculated for adults. Elimination in drinking water processing was neglected, as no data is available. This intake was compared with intake during anti-cancer treatment. Results and discussion Intake of CP and IF for anti-cancer treatment is typically 10 g within a few months. Under such conditions, a relative risk of 1.5 for the carcinogenic compounds CP and IF is reported in the literature. In the worst case, the maximum possible intake by drinking water is less than 10⁻³ (IF) and 10⁻⁵ (CP) of this amount, based on highest measured local concentrations. On a nationwide average, the factor is approx. 10⁻⁶ or less. Conclusions The additional intake of CP and IF due to their emission into surface water and its use without further treatment as drinking water is low compared to intake within a therapy. This approach has shortcomings. It illustrates the current lack of methodology and knowledge for the specific risk assessment of carcinogenic pharmaceuticals in the aquatic environment. IF and CP are directly reacting with the DNA. Therefore, with respect to health effects a safe threshold concentration for these compounds cannot be given. The resulting risk is higher for newborns and children than for adults. Due to the lack of data the risk for newborns and children cannot be assessed fully. The data presented here show that according to present knowledge the additional risk of cancer cannot be fully excluded, especially with respect to children. Due to the shortage of data for effects of CP and IF in low doses during a whole lifespan, possible effects were assessed using data of high doses of CP and IF within short-term ingestion, i.e. therapy. This remains an unresolved issue. Anyway, the risk assessment performed here could give a rough measure of the risks on the one hand and the methodological shortcomings on the other hand which are connected to the assessment of the input of genotoxic and carcinogenic pharmaceuticals such as CP and IF into the aquatic environment. Therefore, we recommend to take measures to reduce the input of CP and IF and other carcinogenic pharmaceuticals. We hope that our manuscript further stimulates the discussion about the human risk assessment for carcinogenic pharmaceuticals in the aquatic environment. Recommendations and perspectives CP and IF are carcinogens. With respect to newborn and children, reduction of the emission of CP and IF into effluent and surface water is recommended at least as a precautionary measure. The collection of unused and outdated drugs is a suitable measure. Collection of patients' excreta as a measure of input reduction is not recommended. Data suitable for the assessment of the risk for newborn and children should be collected in order to perform a risk assessment for these groups. This can stimulate discussion and give new insights into risk assessment for pharmaceuticals in the environment. Our study showed that in the long term, effective risk management for the reduction of the input of CP and IF are recommendable.

Purpose To protect the environmental quality of soil, groundwater, and surface water near the landfill site, it is necessary to make an accurate assessment of the heavy metal mobility. This study aims to present the bio-immobilization behavior of heavy metals in landfill and provide some reference suggestion for the manipulation of heavy metal pollution control after closure. Materials and methods Two simulated bioreactor landfill system loaded with real municipal solid waste (MSW), namely, conventional bioreactor landfill (CL) and leachate recirculated bioreactor landfill (RL), were operated. Cu and Zn, the two conventional heavy metals with the highest contents in MSW, were chosen to track the heavy metal bio-immobilization behavior in landfill. Results The MSW in landfill is a great threat to environment because much of the heavy metal is “hidden” in different components. The weight ratio of Cu and Zn in landfill amounts to 0.00427% and 0.00437%, respectively. The accumulated effluent masses of Cu and Zn in CL increased all along, while they still kept at a stable level after day 105 in RL. Conclusions The microbes like sulfate-reducing bacteria mediate the behavior of Cu and Zn in bioreactor landfill system. Cu and Zn can be bio-immobilized in bioreactor landfill system with leachate recirculation like RL.

Background, aim, and scope Chlorinated volatile organic compounds (CVOCs), widely used in industry as solvents and chemical intermediates in the production of synthetic resins, plastics, and pharmaceuticals, are highly toxic to the environment and public health. Various studies reported that Fenton's oxidation could degrade a variety of chlorinated VOCs in aqueous solutions. In acidic conditions, ferrous ion catalyzes the decomposition of H₂O₂ to form a powerful •OH radical. In this study, wastewater from wash of ion-exchange resin containing typical CVOC, 1,2-dichloroethane, was treated using Fenton's oxidation. To reduce environmental load and processing costs of wastewater, Fenton process as a simple and efficient treatment method was applied to degrade 1,2-dichloroethane of wash water. Materials and methods The water samples were collected from three different washing stages of ion-exchange resin. The degradation of 1,2-dichloroethane and total organic carbon (TOC) of wash water of ion-exchange resin by Fenton process was studied with response surface method (RSM). Design of the experiments was conducted by central composite face, and factors included in three models were Fe²⁺ and H₂O₂ doses and treatment time. Relevant quadratic and interaction terms of factors were investigated. Results According to ANOVA, the model predicts well 1,2-dichloroethane reduction of all water samples and TOC reduction of samples 2 and 3. The Fe²⁺ and H₂O₂ doses used in the present study were most suitable when 1,2-dichloroethane concentration of the wash water is about 120 mg L⁻¹. In that case, Fenton's oxidation reduced 1,2-dichloroethane and TOC up to 100% and 87%, respectively, according to the RSM model. With 90-min reaction time and H₂O₂ dose of 1,200 mg L⁻¹, the required Fe²⁺ doses for 1,2-dichloroethane and TOC were 300 and 900 mg L⁻¹, respectively. The optimal H₂O₂/Fe²⁺ stoichiometric molar ratio was between 4-6. Then, concentration of Fe²⁺ was low enough and the amount of residual sludge can thus be reduced. It seems that most of TOC and part of 1,2-dichloroethane were removed by coagulation. Discussion Up to a certain extent, increase of Fe²⁺ and H₂O₂ doses improved the removal of 1,2-dichloroethane and TOC. High Fe²⁺ doses increased the formation of ferric-based sludge, and excessive H₂O₂ doses in sample 2 decreased the degradation of 1,2-dichloroethane. Excess amount of hydrogen peroxide may scavenge hydroxyl radicals, thus leading to loss of oxidative power. Also, the residual hydrogen peroxide of different samples increased with increasing H₂O₂ dose and H₂O₂/Fe²⁺ molar ratio and decreasing treatment time probably also due to scavenging reactions. Due to the saturated nature of 1,2-dichloroethane, the oxidation mechanism involves hydrogen abstraction before addition of hydroxyl radical, thus leading to lower rate constants than for direct hydroxyl radical attack, which for one increases the treatment time. Conclusions Complete removal of 1,2-dichloroethane was attained with initial concentration <120 mg L⁻¹. Also, TOC degraded effectively. Wash water with higher concentration of 1,2-dichloroethane requires longer treatment times and higher concentrations of Fe²⁺ and H₂O₂ for sufficient 1,2-dichloroethane removal. Recommendations and perspectives Due to the results achieved in this study, Fenton's oxidation could be recommended to be used for organic destruction of wash water of ion-exchange resin. Residual sludge, the main disadvantage in Fenton process, can be reduced by optimizing the ferrous dose or by using heterogeneous treatment where most of the reusable iron remains in the solid phase.

Background, aim, and scope The chemical substance 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) is a non-ionic surfactant used as an industrial defoaming agent and in various other applications. Its commercial name is Surynol 104® and the related ethoxylates are also available as Surfynol® 420, 440, 465 and 485 which are characterized by different grades of ethoxylation of TMDD at both hydroxyl functional groups. TMDD and its ethoxylates offer several advantages in waterborne industrial applications in coatings, inks, adhesives as well as in paper industries. TMDD and its ethoxylates can be expected to reach the aquatic environment due its widespread use and its physico-chemical properties. TMDD has previously been detected in several rivers of Germany with concentrations up to 2.5 µg/L. In the United States, TMDD was also detected in drinking water. However, detailed studies about its presence and distribution in the aquatic environment have not been carried out so far. The aim of the present study was the analysis of the spatial and temporal concentration variations of TMDD in the river Rhine at the Rheingütestation Worms (443.3 km). Moreover, the transported load in the Rhine was investigated during two entire days and 7 weeks between November 2007 and January 2008. Materials and methods The sampling was carried out at three different sampling points across the river. Sampling point MWL1 is located in the left part of the river, MWL2 in the middle part, and MWL4 in the right part. One more sampling site (MWL3) was run by the monitoring station until the end of 2006, but was put out of service due to financial constrains. The water at the left side of the river Rhine (MWL1) is influenced by sewage from a big chemical plant in Ludwigshafen and by the sewage water from this city. The water at the right side of the river Rhine (MWL4) is largely composed of the water inflow from river Neckar, discharging into Rhine 14.9 km upstream from the sampling point and of communal and industrial wastewater from the city Mannheim. The water from the middle of the river (MWL2) is largely composed of water from the upper Rhine. Water samples were collected in 1-L bottles by an automatic sampler. The water samples were concentrated by use of solid-phase extraction (SPE) using Bond Elut PPL cartridges and quantified by use of gas chromatography-mass spectrometry (GC-MS). The quantification was carried out with the internal standard method. Based on these results, concentration variations were determined for the day profiles and week profiles. The total number of analyzed samples was 219. Results The results of this study provide information on the temporal concentration variability of TMDD in river Rhine in a cross section at one particular sampling point (443.3 km). TMDD was detected in all analyzed water samples at high concentrations. The mean concentrations during the 2 days were 314 ng/L in MWL1, 246 ng/L in MWL2, and 286 ng/L in MWL4. The variation of concentrations was low in the day profiles. In the week profiles, a trend of increasing TMDD concentrations was detected particularly in January 2008, when TMDD concentrations reached values up to 1,330 ng/L in MWL1. The mean TMDD concentrations during the week profiles were 540 ng/L in MWL1, 484 ng/L in MWL2, and 576 ng/L in MWL4. The loads of TMDD were also determined and revealed to be comparable in all three sections of the river. The chemical plant located at the left side of the Rhine is not contributing additional TMDD to the river. The load of TMDD has been determined to be 62.8 kg/d on average during the entire period. By extrapolation of data obtained from seven week profiles the annual load was calculated to 23 t/a. Discussion The permanent high TMDD concentrations during the investigation period indicate an almost constant discharge of TMDD into the river. This observation argues for effluents of municipal wastewater treatment plants as the most likely source of TMDD in the river. Another possible source might be the degradation of ethoxylates of TMDD (Surfynol® series 400), in the WWTPs under formation of TMDD followed by discharge into the river. TMDD has to be considered as a high-production-volume (HPV) chemical based on the high concentrations found in this study. In the United States, TMDD is already in the list of HPV chemicals from the Environmental Protection Agency (EPA). However, the amount of TMDD production in Europe is unknown so far and also the biodegradation rates of TMDD in WWTPs have not been investigated. Conclusions TMDD was found in high concentrations during the entire sampling period in the Rhine river at the three sampling points. During the sampling period, TMDD concentrations remained constant in each part of the river. These results show that TMDD is uniformly distributed in the water collected at three sampling points located across the river. ‘Waves' of exceptionally high concentrations of TMDD could not be detected during the sampling period. These results indicate that the effluents of WWTPs have to be considered as the most important sources of TMDD in river Rhine. Recommendations and perspectives Based also on the occurrence of TMDD in different surface waters of Germany with concentrations up to 2,500 ng/L and its presence in drinking water in the USA, more detailed investigations regarding its sources and distribution in the aquatic environment are required. Moreover, the knowledge with respect to its ecotoxicity and its biodegradation pathway is scarce and has to be gained in more detail. Further research is necessary to investigate the rate of elimination of TMDD in municipal and industrial wastewater treatment plants in order to clarify the degradation rate of TMDD and to determine to which extent effluents of WWTPs contribute to the input of TMDD into surface waters. Supplementary studies are needed to clarify whether the ethoxylates of TMDD (known as Surfynol 400® series) are hydrolyzed in the aquatic environment resulting in formation of TMDD similar to the well known cleavage of nonylphenol ethoxylates into nonylphenols. The stability of TMDD under anaerobic conditions in groundwater is also unknown and should be studied.

INTRODUCTION: Naturally occurring hydroxylated polybrominated diphenyl ethers (OH-PBDEs), their methoxylated counterparts (MeO-PBDEs), and polybrominated dibenzo-p-dioxins (PBDDs), together with their potential precursors polybrominated phenols (PBPs) and polybrominated anisoles (PBAs), were analyzed in blue mussels (Mytilus edulis) gathered along the east coast (bordering the Baltic Sea) and west coast of Sweden (bordering the North Sea). Brown algae (Dictyosiphon foenicolaceus) and cyanobacteria (Nodularia spumigena) from the Baltic Sea, considered to be among the primary producers of these compounds, were also analyzed for comparison. MATERIALS AND METHODS: The samples were liquid–liquid extracted, separated into a phenolic and a neutral fraction, and subsequently analyzed by gas chromatography–mass spectrometry (GS-MS). RESULTS AND DISCUSSION: The levels of OH-PBDEs, MeO-PBDEs and PBDDs were significantly higher in Baltic Sea mussels than in those from the west coast, whereas the levels of PBPs and PBAs displayed the opposite pattern. The blue mussels from the Baltic Sea contained high levels of all analyzed substances, much higher than the levels of, e.g., polybrominated diphenyl ethers. In addition, the GC-MS chromatogram of the phenolic fraction of the west coast samples was dominated by four unknown peak clusters, three of which were tentatively identified as dihydroxy-PBDEs and the other as a hydroxylated-methyl-tetraBDE. CONCLUSIONS: Clearly, all of the compounds analyzed are natural products, both in the Baltic and the North Sea. However, the geographical differences in composition may indicate different origin, e.g., due to differences in the occurrence and/or abundance of various algae species along these two coasts or possibly a more extensive dilution on the west coast.

Introduction The pyrolytic method was employed to recycle metals and brominated compounds blended into printed circuit boards (PCBs). Methods PCBs were crushed into pieces 4.0-4.8 mm in size, and the crushed pieces were pyrolyzed at temperatures ranging from 200 to 500°C. The compositions of pyrolytic residues, liquid products, and exhaust were analyzed by inductively coupled plasma atomic emission spectrometer, inductively coupled plasma mass spectrometry, and gas chromatography-mass spectrometry. Pyrolytic exhaust was collected by an impinger system in an ice bath cooler to analyze the composition fraction of the liquid product, and uncondensable exhaust was collected for gas constituent analysis. Results Phenol, methyl-phenol, and bromo-phenol were attributed mainly to the liquid product. Metal content was low in the liquid product. In addition, CO, CO₂, CH₄, and H₂ were the major components of pyrolytic exhaust. Conclusions Brominated and chlorinated compounds—i.e., dichloromethane, trans-1,2 dichloroethylene, cis-1,2 dichloroethylene, 1,1,1-trichloroethane, tetrachloromethane, bromophenol, and bromoform—could be high, up to the several parts per million (ppm) level. Low molecular weight volatile organic compounds (VOCs)—i.e., methanol, acetone, ethyl acetate, acrylonitrile, 1-butene, propene, propane, and n-butane—contributed a large fraction of VOCs. The concentrations of toluene, benzene, xylene, ethylbenzene, and styrene were in the ppm range.

Background, aim and scope Perfluorinated compounds (PFCs) are global environmental pollutants that bioaccumulate in wildlife and humans. Laboratory experiments have revealed toxic effects such as delayed development, humoral suppression, and hepatotoxicity. Although numerous human blood levels have been reported, little is known about distribution in the human body. Knowledge about PFC distribution and accumulation in the human body is crucial to understanding uptake and subsequent effects as well as to conduct risk assessments. The present study reports PFC levels in human liver and breast milk from a general population living in Catalonia, Spain. Liver and milk levels are compared to previously reported levels in blood from the same geographic area as well as to other existing reports on human liver and milk levels in other countries. Materials and methods Human liver (n = 12) and milk (n = 10) samples were collected in 2007 and 2008 in Catalonia, Spain. Liver samples were taken postmortem from six males and six females aged 27-79 years. Milk samples were from healthy primipara women (30-39 years old). Both liver and milk were analyzed by solid-phase extraction and ultra-performance liquid chromatography tandem mass spectrometry. Results Six PFCs were detected in liver, with perfluorooctanesulfonate (PFOS, 26.6 ng/g wet weight) being the chemical with the highest mean concentration. Other PFCs such as perfluorohexanesulfonate (PFHxS), perfluorooctanoic acid (PFOA), and acids with chain lengths up to C11 were also detected, with mean levels ranging between 0.50 and 1.45 ng/g wet weight. On the other hand, PFOS and PFHxS were the only PFCs detected in human milk, with mean concentrations of 0.12 and 0.04 ng/mL, respectively. Discussion While milk concentrations were similar to reported levels from other countries, liver samples contained more PFCs above quantification limits and higher PFOS concentrations compared to the only two other reports found in the literature. Differences between the results of the present study and those concerning previous investigations can be due to declining levels of some PFCs, which have been reported for the USA. The relationship between PFC concentrations in human liver, milk, and blood was assessed using blood concentrations previously determined in Catalonia. Those levels resulted in liver/serum ratios of 1.7:1, 1.4:1, and 2.1:1 for PFOS, perfluorodecanoic acid, and perfluoroundecanoic acid, respectively. Accumulation in liver is suggested for PFOS and the perfluorocarboxylic acids with carbon chain lengths C9, C10, and C11. For PFOA and PFHxS, fivefold and 14-fold higher concentrations, respectively, were seen in serum as compared to liver. The mean concentration of PFOS and PFHxS in milk was only 0.8% and 0.6% of the reported mean serum level, respectively. Conclusions The results of the present study show that several PFCs could be detected in human liver samples of subjects living in Tarragona. Concerning human milk, the mechanism by which PFCs are transferred from mother's blood to breast milk is still unclear. Considering that PFCs are strongly bound to the protein fraction in blood, the possibility of PFCs entering the milk and accumulating to levels observed in maternal plasma is limited. Recommendations and perspectives Interestingly, the potential accumulation difference for PFCs with different chain lengths might be of great importance for risk assessment. Continuing studies on the distribution of different PFCs in human tissue are therefore justified.

Background, aim, and scope Linear alkylbenzene sulfonate (LAS) is the most used anionic surfactant in a worldwide scale and is considered a high-priority pollutant. LAS is regarded as a readily biodegradable product under aerobic conditions in aqueous media and is mostly removed in wastewater treatment plants, but an important fraction (20-25%) is immobilized in sewage sludge and persists under anoxic conditions. Due to the application of the sludge as a fertilizer, LAS reaches agricultural soil, and therefore, microbial toxicity tests have been widely used to evaluate the influence of LAS on soil microbial ecology. However, molecular-based community-level analyses have been seldom applied in studies regarding the effects of LAS on natural or engineered systems, and, to our knowledge, there are no reports of their use for such appraisals in agricultural soil. In this study, a microcosm system is used to evaluate the effects of a commercial mixture of LAS on the community structure of Alphaproteobacteria, Actinobacteria, and Acidobacteria in an agricultural soil. Material and methods The microcosms consisted of agricultural soil columns (800 g) fed with sterile water (8 ml h⁻¹) added of different concentration of LAS (10 or 50 mg l⁻¹) for periods of time up to 21 days. Sterile water was added to control columns for comparison. The structures of Alphaproteobacteria, Actinobacteria, and Acidobacteria communities were analyzed by a cultivation independent method (temperature gradient gel electrophoresis (TGGE) separation of polymerase chain reaction (PCR)-amplified partial 16S rRNA genes). Relevant populations were identified by subsequent reamplification, DNA sequencing, and database comparisons. Results Cluster analysis of the TGGE fingerprints taking into consideration both the number of bands and their relative intensities revealed that the structure of the Alphaproteobacteria community was significantly changed in the presence of LAS, at both concentrations tested. The average number of bands was significantly lower in the microcosms receiving 50 mg l⁻¹ LAS and in the lower portion of soil cores. The clear differentiation of the samples of the upper portion of the soil columns amended with LAS was specifically related to the presence and intensity of a distinctive major band (named band class 7). There was a statistically significant positive correlation between the concentrations of LAS detected in soil portions taken from LAS 10 mg l⁻¹ and LAS 50 mg l⁻¹ microcosms and the relative intensity of band class 7 in the corresponding TGGE profiles. Prevalent Alphaproteobacteria populations in the soil microcosms had close similarity (>99%) to cultivated species affiliated to genera of the Rhizobiaceae, Methylocystaceae, Hyphomicrobiaceae, Rhodospirillaceae, Brucellaceae, Bradyrhizobiaceae, and Caulobacteraceae families. The population represented by band class 7 was found closely related to the genus Phenylobacterium (Caulobacteraceae). According to cluster analysis of TGGE profiles, the structure of both Actinobacteria and Acidobacteria communities in the soil microcosms was remarkably stable in the presence of LAS at the two concentrations tested, as most bands were universally present in all samples and displayed fairly similar relative intensities. Discussion Previous studies by others authors, based on biological and chemical tests, concluded that LAS toxicity was not an important microbial selection factor in sludge amended soil, while work based on the use of molecular fingerprinting to evaluate the impact of LAS in aqueous media and marine sediments showed that concentrations as low as 1 mg l⁻¹ significantly influence the development of the bacterial community structure. Although TGGE is not a strictly quantitative method due to the bias introduced by the PCR reaction, changes of band intensity through experiments are a consequence of a change in the relative abundance of the corresponding populations in the community and can be used as a semiquantitative measure of bacterial diversity. Our results evidence that the Phenylobacterium population represented by band class 7 was favored by the presence of increasing concentrations of LAS in the soil and turned into a dominant population, suggesting its possible ability to use LAS in soil as a source of nutrients. As studies with pure cultures are required to confirm the ability of this population to degrade LAS, isolation strategies are currently under development in our laboratory. The weak effect of LAS on the structure of Actinobacteria and Acidobacteria communities is particularly interesting, as to our knowledge, there are no previous reports regarding the effects of LAS on these bacterial groups in soil. Conclusions, recommendations, and perspectives The Phenylobacterium-related alphaproteobacterial population identified in this work was selectively enriched in LAS polluted soil and is a plausible candidate to play a relevant role in the biotransformation of the surfactant under the conditions tested. The surfactant had no remarkable effects on the Actinobacteria and Acidobacteria fingerprints in soil, even when present at concentrations widely exceeding those reached in soil immediately after sludge application. TGGE fingerprinting provides a reliable and low time-consuming method for the monitoring of the bacterial community structure and dynamics, and we recommend its integration with the biological and chemical analyses usually applied in risk assessment of LAS in the environment.