Biomedical subjects

M Bueno

Publications and source records attributed to M Bueno.

At least 19 recordsLinked to original sources

PubMed2006

Diversity of metabolic syndrome risk factors in obese children and adolescents.

The aim of this study was to investigate the frequency of metabolic syndrome (MS) variables in a group of spanish obese children and adolescents, to asses MS prevalence in this population and to describe it's relationship with other metabolic risk factors. 103 children were studied : 54 male and 49 female, mean age 10.08+/-2.3 with exogenous obesity. Obesity was defined when BMI was higher than the age and sex specific equivalent to 30 kg/m(2) in adults. MS variables considered were waist circumference, blood pressure, fasting blood triglycerides, fasting glucose/insulin and HDL-cholesterol. The children were considered as having the MS when three or more characteristics showed abnormal values according to Cook and De Ferranti definitions. HOMA index, ApoB and ApoA1 were studied too. The most frequent features of the metabolic syndrome were excess waist circumference and hypertension. The MS markers with the lowest frequency were dyslipidemia and fasting hyperglicemia. MS prevalence was 29,9% (Cook et al. criteria) and 50% (De Ferranti et al. criteria). Fasting insulin and HOMA index values increased significantly (p < 0.05) when three or more abnormalities of the MS variables were present. Apo B increased significantly only in females (p < 0.05) and Apo Al decreased significantly (p < 0.05) in both sexes when MS was present. Adequate metabolic syndrome risk factors criteria, mainly cut-off values, need to be defined in the European paediatric population.

Adolescent↗

PubMed2006

Anthropometric body fat composition reference values in Spanish adolescents. The AVENA Study.

OBJECTIVE: To determine reference values for body mass index (BMI), sum of six skinfolds (sigma6 skinfolds) and body fat percentage (BF%) in Spanish adolescents aged 13-18 years, included in the AVENA Study (Alimentación y Valoración del Estado Nutricional en Adolescentes: Food and Assessment of the Nutritional Status of Adolescents). DESIGN: Multicentre cross-sectional study. SETTING: Representative sample of Spanish adolescents. SUBJECTS: The population was selected by means of a multiplestep, simple random sampling. The final number of subjects included in the AVENA Study was 2859 adolescents; 2160 adolescents had a complete set of anthropometric measurements and were then included in this study (1109 males and 1051 females). INTERVENTIONS: Weight, height and six skinfold thicknesses were measured. As indices of total adiposity, we calculated BMI, summation sigma6 skinfolds and BF% with the formulas described by Slaughter et al. RESULTS: Sigma6 skinfolds and BF% in each age group were significantly higher in females than in males. In males, age showed a significant effect for BMI, sigma6 skinfolds and BF%; however, in females, the effect was only significant for BF%. The percentile distribution was more disperse towards higher sigma6 skinfolds and BF% values in males when compared with females. CONCLUSIONS: The presented percentile values will help us to classify adolescents in comparison with a well-established reference population, and to estimate the proportion of adolescents with high or low adiposity amounts. SPONSORSHIP: The AVENA-Study was supported by the Spanish Ministry of Health (FIS 00/0015), and grants from Panrico SA, Madaus SA and Procter and Gamble SA. This study was also supported by Instituto de Salud Carlos III (Spain), RCESP (C03/09) and Spanish Ministry of Education (AP2003-2128).

Adipose Tissue↗

PubMed2005

Equilibrium phi-analysis of a molten globule: the 1-149 apoflavodoxin fragment.

The apoflavodoxin fragment comprising residues 1-149 that can be obtained by chemical cleavage of the C-terminal alpha-helix of the full-length protein is known to populate a molten globule conformation that displays a cooperative behaviour and experiences two-state urea and thermal denaturation. Here, we have used a recombinant form of this fragment to investigate molten globule energetics and to derive structural information by equilibrium Phi-analysis. We have characterized 15 mutant fragments designed to probe the persistence of native interactions in the molten globule and compared their conformational stability to that of the equivalent full-length apoflavodoxin mutants. According to our data, most of the mutations analysed modify the stability of the molten globule fragment following the trend observed when the same mutations are implemented in the full-length protein. However, the changes in stability observed in the molten globule are much smaller and the Phi-values calculated are (with a single exception) below 0.4. This is consistent with an overall and significant debilitation of the native structure. Nevertheless, the fact that the molten globule fragment can be stabilised using as a guide the native structure of the full-length protein (by increasing helix propensity, optimising charge interactions and filling small cavities) suggests that the overall structure of the molten globule is still quite close to native, in spite of the lowered stability observed.

Anabaena↗

PubMed2005

Carbamide peroxide bleaching agents: effects on surface roughness of enamel, composite and porcelain.

This study examined the effect of 10 and 35% carbamide peroxide bleaching agents on the surface roughness of enamel, feldspathic porcelain, and microfilled and microhybrid composite resins. Standardized cylindrical specimens were prepared for restorative materials. Enamel samples were obtained from buccal and lingual surfaces of human molars. Samples from each substrate were divided in three subgroups (n=10), according to surface treatment: distilled water (control), and 10 and 35% carbamide peroxide. The 10% agent was applied 3 h daily and the 35% agent was applied for 30 min/week, at 37 degrees C, during 21 days. Control samples remained stored in distilled water, at 37 degrees C. Roughness measurements (Ra, microm) were made at 24 h and repeated after 7, 14 and 21 days of exposure. Data were analyzed using ANOVA (split-plot design) and Tukey's test (5% significance level). Samples from control groups showed no significant alteration during all test periods, while for exposure to 10% agent, only the porcelain presented a rougher surface after 21 days (p<0.05). For the 35% product, roughness means significantly increased during the first and second weeks for enamel (p<0.05), and after 21 days for porcelain (p<0.05) and for the microhybrid composite (p<0.05). Microfilled samples showed no significant alteration throughout the 21-day period, regardless of the surface treatment.

Aluminum Silicates↗

PubMed2005

Homeostatic model assessment (HOMA) index cut-off values to identify the metabolic syndrome in children.

The aim of the study was to establish the best cut-off value for the homeostatic model assessment (HOMA) index in identifying children and adolescents with the metabolic syndrome. The study included 72 non-obese and 68 obese children aged 7 to 16 years. Obesity is defined using the criteria proposed by Cole et al., being included as metabolic syndrome variables waist circumference, systolic blood pressure, diastolic blood pressure and seric values of glucose, uric acid, fasting insulin, leptin, triglycerides and HDL-cholesterol. Children were considered as having the metabolic syndrome when four or more characteristics showed abnormal values. The HOMA index was calculated as the product of the fasting plasma insulin level (microU/mL) and the fasting plasma glucose level (mmol/L), divided by 22.5. HOMA index cut-offs from the 5th to the 95th percentile were used. A receiver operating characteristic (ROC) curve was generated using the different HOMA cut-offs for the screening of the metabolic syndrome. The areas under the ROC curve, 95% confidence intervals, and the point to the ROC curve closest to 1, were calculated. The area under the ROC curve was 0.863 (95% C.I.: 0.797, 0.930). The point closest to 1 corresponds to the 60th percentile of the HOMA index distribution in our sample. HOMA index value at the 60th percentile was 2.28. Cut-off values corresponding to a range of HOMA index from the 50 to the 75 percentile, showed similar distances to 1. HOMA index values for percentiles 50 to 75 ranged from 2.07 to 2.83. In conclusion, HOMA index could be a useful tool to detect children and adolescents with the metabolic syndrome. HOMA cut-off values need to be defined in the paediatric population; however, values near to 3 seem to be adequate.

Adolescent↗

PubMed2005

Body fat measurement in adolescents: comparison of skinfold thickness equations with dual-energy X-ray absorptiometry.

OBJECTIVE: To compare the most commonly used equations to predict body fatness from skinfold thickness, in male and female adolescents, with dual-energy X-ray absorptiometry (DXA) as a reference method of fatness measurement. DESIGN: Cross-sectional nutrition survey. SETTING: General adolescent population from Zaragoza (Spain). SUBJECTS AND METHODS: A total of 238 Caucasian adolescents (167 females and 113 males), aged 13.0-17.9 y, were recruited from 15 school groups in 11 public and private schools. The percentage fat mass (%FM) was calculated by using skinfold-thickness equations. Predicted %FM was compared with the reference %FM values, measured by DXA. The lack of agreement between methods was assessed by calculating the bias and its 95% limits of agreement. RESULTS: Most equations did not demonstrate good agreement compared with DXA. However, in male adolescents, Slaughter et al equations showed relative biases that were not dependent on body fatness and the limits of agreement were narrower than those obtained from the rest of equations. In females, Brook's equation showed nonsignificant differences against DXA and the narrowest 95% limits of agreement. Only biases from Brook and Slaughter et al equations were not dependent on body fatness in female adolescents. CONCLUSIONS: Accuracy of most of the skinfold-thickness equations for assessment of %FM in adolescents was poor at the individual level. Nevertheless, to predict %FM when a relative index of fatness is required in field or clinical studies, Slaughter et al equations may be used in adolescents from both sexes and the Brook equation in female adolescents.

Absorptiometry, Photon↗

PubMed2005

Secular trends in waist circumference in Spanish adolescents, 1995 to 2000-02.

Two studies, in 1995 and 2000-02, were compared to assess changes in waist circumference in adolescents. Between the two time periods, waist circumference increased significantly in males at 13 years and in females at 14 years. Significant changes in waist circumference were observed during the study period; the rates of change were 0.53 and 0.86 cm/y in boys and 0.67 and 0.87 cm/y in girls. Future morbidity in adolescents may be affected due to accumulation of excess central fat.

Adipose Tissue↗

PubMed2004

Micro-environmental and socio-demographic determinants of childhood obesity.

AIM: To review the available data in Spain about the socio-demographic and home environmental determinants in children and adolescents. METHOD: Review of the main studies conducted in Spain that have analysed the relationship between overweight and socio-economic and environmental determinants in children and adolescents. RESULTS: In children aged 6-7 y from Aragon (Spain), the socio-demographic determinants of childhood overweight were size of municipality, year of examination, gender, and province; in adolescents aged 13-14 y, the socio-demographic determinants were year of examination, type of school, size of municipality, gender, and province; overweight showed a significant positive main effect with public schools and low municipality size. In a nationally representative sample of Spanish adolescents from 13 to 18.5 y (AVENA Study), there was a significant relationship between overweight and socio-economic status in males but not in females; in males, the lowest overweight prevalences were observed in both extreme socio-economic groups; moreover, overweight prevalences increased when socio-economic status decreased, from the high to the medium-low socio-economic group. The studied variables related with family environment did not show any significant effect in overweight prevalence. CONCLUSION: Better knowledge of the relationship between social class and childhood obesity would lead to clearer hypotheses for the relationship in adults and might improve the preventive measures by identifying children at risk.

Adolescent↗

PubMed2004

Body composition in adolescents: measurements and metabolic aspects.

INTRODUCTION: Adolescence is a decisive period in human life in which important body composition changes occur. Increase of total body mass and its relative distribution are mainly related to gender and pubertal development. OBJECTIVE: This review explores the specific measurements that may be used in this age group to assess excess body fat and to define obesity and overweight. RESULTS: Identification of subjects at risk for adiposity requires simple anthropometric cutoffs for the screening of overweight and obesity. In this context, BMI criterion is the most frequently used but, in spite of its high sensitivity and specificity, an important number of adolescents classified as overweight or obese do not have really high adiposity (32.1% of females and 42% of males). Excess total body fat and intra-abdominal visceral fat are related to metabolic abnormalities that increase the risk of cardiovascular diseases. Waist circumference seems to be the best simple anthropometric predictor for the screening of the metabolic syndrome in children and adolescents. CONCLUSIONS: Early identification of adolescents at risk for adiposity and its related metabolic complications requires reliable, simple and specific measures of excess body fat for this age group.

Adolescent↗

PubMed2003

Insulin resistance and impaired glucose tolerance in obese children and adolescents.

In developed countries, obesity prevalence has strongly increased in the last decades. This has also been observed in children and adolescents. Until recently, type 2 diabetes mellitus was considered very rare among children and adolescents; however, in the last decades, some cases have been observed mainly in obese adolescents of some minority populations. The aim of our study was to assess the prevalence of type 2 diabetes, impaired glucose tolerance (IGT) and insulin resistance, and the metabolic features, in obese children and adolescents. We have studied 95 obese children and adolescents, 53 males and 42 females, aged 4-16 years. The prevalence of IGT in obese children and adolescents studied was 7.4%; there was not any child with type 2 diabetes. Fasting glucose and insulin serum concentrations did not show significant differences between obese children with or without IGT; however, 120 minutes after an oral glucose tolerance test, glucose and insulin serum concentrations showed statistically significant differences between both groups. Insulin resistance is defined as a HOMA index higher than 4. The prevalence of insulin resistance in obese children studied was 35.8%. Trygliceride serum concentrations were higher and HDL-C serum concentrations were lower in obese children with IGT than in those without IGT, but the differences were not statistically significant. IGT and insulin resistance are frequent in obese children and adolescents; early treatment in obese children and adolescents with IGT constitutes a strategy of reversing progression to beta-cell failure and in preventing type 2 diabetes.

Adolescent↗

PubMed2003

Psyllium fibre and the metabolic control of obese children and adolescents.

In children and adolescents from developed countries, obesity prevalence has strongly increased in the last decades and insulin resistance and impaired glucose tolerance are frequently observed. Some dietary components such as low glycemic index foods and dietary fibre could be used in order to improve glucose homeostasis in these children. Psyllium or ispaghula husk (the husk of the seeds of Plantago ovata) is a mixture of neutral and acid polysaccharides containing galacturonic acid with a ratio of soluble/insoluble fibre of 70/30. Some foods could potentially be enriched with psyllium, like breads, breakfast cereals, pasta and snack foods. The aim of this review was to assess the usefulness of psyllium in the management of obese children and adolescents with abnormalities of carbohydrate and lipid metabolism. After psyllium supplementation, the percentage change in postprandial glucose in type 2 diabetes patients, ranged from -12.2 to -20.2%. In hypercholesterolemic children, the effect of psyllium in LDL-cholesterol serum concentrations ranged from 2.78 to -22.8%; the effect in HDL-cholesterol from -4.16 to 3.05%; and the effect on triglycerides from 8.49 to -19.54%. The reviewed evidence seems to show that psyllium improves glucose homeostasis and the lipid and lipoprotein profile; however, more well controlled trials and further studies are needed to clarify it's effects and the mechanisms involved.

Adolescent↗

PubMed2003

T(H)1/T(H)2 cytokine profile, metalloprotease-9 activity and hormonal status in pregnant rheumatoid arthritis and systemic lupus erythematosus patients.

During the course of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), several immune and neuroendocrine changes associated with pregnancy may exert positive (amelioration) or negative (exacerbation) effects on the clinical outcome. In order to shed light on the mechanisms underlying these responses, we performed a prospective longitudinal study in RA and SLE pregnant women, including healthy pregnant women as a control group. Cytokine messenger RNA (mRNA) expression assessed by quantitative competitive polymerase chain reaction (PCR) in peripheral blood mononuclear cells (PBMC), cytokine levels and lymphocyte proliferation responses (LPR) following phytohaemagglutinin (PHA) stimulation of PBMC, plasma metalloprotease-9 activity (MMP-9) and hormonal status during pregnancy were determined. TNFa was the most abundant cytokine mRNA expressed in PBMC in all groups studied (healthy pregnant women, RA and SLE pregnant patients). However, a general TH2 response reflected by high IL-10 levels was found in RA, as well as SLE, patients. A significant change in IFN-gamma was observed in RA patients but only during the first trimester of pregnancy. This compared with a major TH1 response in healthy pregnant women. Interestingly, our study showed a homogeneous hormonal pattern in RA and SLE patients. Although decreased cortisol levels were observed in all patients studied, this is possibly related to the remission of disease activity status brought about by steroid treatment before and during pregnancy. In summary, we suggest that complex immune and hormonal networks are involved in pregnancy and that rheumatic diseases are very dynamic immune processes that cannot be described with a clear-cut cytokine profile. Furthermore, the observations in this study may reflect treatment-related immune effects more than those associated with disease.

Adult↗

PubMed2002

Determinants of resting energy expenditure in obese and non-obese children and adolescents.

Resting energy expenditure (REE) is the largest component of total daily energy expenditure. Objectives of this study were to examine whether differences in REE exist after obesity develops in a group of children and adolescents, and to determine the effects of body composition, gender, age, pubertal development and parental obesity on REE. In 116 Caucasian children and adolescents (57 obese and 59 non-obese), aged 7.8 to 16.6 years, REE was assessed by open-circuit indirect calorimetry and different anthropometric variables and bioelectrical impedance were obtained (weight, height, skinfold thicknesses, waist and hip circumferences). Anthropometric indices and body compartments were calculated: the body mass index, surface area (SA), fat-free mass (FFM), fat-mass (FM) and percentage of FM. Differences between obese and non-obese subjects were tested and stepwise multiple regression analysis was performed with REE as dependent variable. Results show that REE was significantly higher in obese than in non-obese children and adolescents but REE/FFM ratio was not significantly different between these groups. In the non-obese group, FFM explained 73.1% of the variability in REE and gender, age and SA added 3.8%, 2.6%, and 2.6% to it, respectively. In the obese group, FFM was also the most powerful predictor of REE with 72.3%, followed by waist circumference and age with 2.5% and 2.1%, respectively. These results show that REE differences between obese and lean children do not seem to justify the maintenance of obesity. The main determinant of REE is FFM in both groups. No significant contribution of FM, pubertal development or parental obesity in REE was found in children and adolescents.

Adipose Tissue↗

PubMed2002

Resting energy expenditure in children and adolescents: agreement between calorimetry and prediction equations.

BACKGROUND AND AIMS: To assess the degree of agreement between indirect calorimetry and five equations commonly used to predict resting energy expenditure (REE) in obese and non-obese children and adolescents. METHODS: In 116 children and adolescents (57 obese and 59 non-obese) aged between 7.8 and 16.6 years, REE was measured (MREE) by open-circuit indirect calorimetry under standardized conditions. REE was predicted (PREE) in all subjects with equations from the Food and Agriculture/World Health Organization/United Nations University (FAO/WHO/UNU), Maffeis et al., Harris and Benedict, and two from Schofield: one using weight (W) and one using height and weight (H-W). Agreement between indirect calorimetry and equations was assessed following the Bland-Altman method. RESULTS: In the entire cohort group, only data from FAO/WHO/UNU, Schofield-W and Schofield-HW equations showed non-statistic differences against calorimetry results. When agreement between equations and calorimetry was tested, Schofield-HW equation showed the lowest mean MREE-PREE difference: 3.7 kcal/d (limits of agreement -293 and 300 kcal/d; 95% confidence interval for the bias -24.0 to 31.5 kcal/d) and the best agreement. Group by group, equations which obtained the best agreement were: FAO/WHO/UNU in girls, Schofield-HW in boys, Schofield-HW in obese, and Schofield-W in non-obese. CONCLUSIONS: Until more accurate prediction equations are developed, we recommend Schofield-HW equations for REE studies with a mixed population of obese and non-obese children and adolescents; however, FAO/WHO/UNU equation may also be useful in girls and Schofield-W equation in non-obese children.

Adolescent↗

PubMed2002

Leptin and metabolic syndrome in obese and non-obese children.

Metabolic syndrome is characterized by a clustering of metabolic abnormalities: insulin resistance - hyperinsulinemia, dyslipidemia (high triglycerides and low HDL - cholesterol serum concentrations), impaired glucose tolerance and/or type 2 diabetes, and hypertension. The aim of this study was to analyse the role of different variables of metabolic syndrome, including leptin, in 74 non-obese children and 68 children with non-syndromal obesity. As metabolic syndrome variables, we have included body mass index, waist circumference, trunk-to-total skinfolds (%), systolic blood pressure, diastolic blood pressure, glucose, uric acid, fasting insulin, triglycerides and high-density lipoprotein-cholesterol (HDL-C). Factor analysis showed 4 factors in each group. In non-obese children, waist circumference, BMI, fasting insulin, triglycerides, trunk-to-total skinfolds (%), leptin and uric acid loaded positively on factor 1, and HDL-C loaded negatively on this factor; systolic and diastolic blood pressure had high positive loadings in factor 2; HDL-C and leptin showed positive loadings and triglycerides and uric acid, negative loadings in factor 3; and, finally, glucose and insulin showed positive loadings in factor 4. These four factors explained 72.16 % of the total variance in the non-obese group. In obese children, BMI, waist circumference, leptin, diastolic blood pressure and systolic blood pressure loaded positively on factor 1; diastolic blood pressure, trunk-to-total skinfolds (%), uric acid and systolic blood pressure showed high positive loadings in factor 2; fasting insulin, glucose and triglycerides showed positive loadings in factor 3; and, finally, triglycerides showed positive loadings and HDL-C negative loadings in factor 4. These four factors explained 74.18 % of the total variance in the obese group. Our results point to a different homeostatic control of metabolic syndrome characteristics in obese and non-obese children. Leptin seems to play a key underlying role in metabolic syndrome, especially in the obese group.

Blood Glucose↗

PubMed2002

Waist circumference for the screening of the metabolic syndrome in children.

AIM: To identify the best anthropometric predictor of the metabolic syndrome in children. METHODS: Screening performance was evaluated in a clinical setting. The study included 140 children: 72 non-obese and 68 with non-syndromal obesity. Body mass index (BMI), waist circumference and triceps/subscapular skinfolds ratio were used as predictor variables, and systolic blood pressure, diastolic blood pressure, glucose, uric acid, fasting insulin, triglycerides and HDL-C as metabolic syndrome variables. RESULTS: The areas under the receiver operating characteristic (ROC) curves were 0.849 (95% CI: 0.780, 0.919) for BMI, 0.868 (95% CI: 0.801,0.934) for waist circumference and 0.834 (95% CI: 0.757,0.910) for the triceps/subscapular skinfolds ratio. No statistically significant differences were found for the three areas under the ROC curves. The point on the ROC curve closest to 1 corresponded to the 65th percentile for BMI, to the 70th percentile for waist, and to the 40th percentile for the triceps/subscapular skinfolds ratio. CONCLUSION: Waist circumference seems to be the best predictor of children with the metabolic syndrome in paediatric clinical settings.

Adipose Tissue↗

PubMed2001

Serine/threonine protein phosphatase 5 (PP5) participates in the regulation of glucocorticoid receptor nucleocytoplasmic shuttling.

BACKGROUND: In most cells glucocorticoid receptors (GR) reside predominantly in the cytoplasm. Upon hormone binding, the GR translocates into the nucleus, where the hormone-activated GR-complex regulates the transcription of GR-responsive genes. Serine/threonine protein phosphatase type 5 (PP5) associates with the GR-heat-shock protein-90 complex, and the suppression of PP5 expression with ISIS 15534 stimulates the activity of GR-responsive reporter plasmids, without affecting the binding of hormone to the GR. RESULTS: To further characterize the mechanism by which PP5 affects GR-induced gene expression, we employed immunofluorescence microscopy to track the movement of a GR-green fluorescent fusion protein (GR-GFP) that retained hormone binding, nuclear translocation activity and specific DNA binding activity, but is incapable of transactivation. In the absence of glucocorticoids, GR-GFP localized mainly in the cytoplasm. Treatment with dexamethasone results in the efficient translocation of GR-GFPs into the nucleus. The nuclear accumulation of GR-GFP, without the addition of glucocorticoids, was also observed when the expression of PP5 was suppressed by treatment with ISIS 15534. In contrast, ISIS 15534 treatment had no apparent effect on calcium induced nuclear translocation of NFAT-GFP. CONCLUSION: These studies suggest that PP5 participates in the regulation of glucocorticoid receptor nucleocytoplasmic shuttling, and that the GR-induced transcriptional activity observed when the expression of PP5 is suppressed by treatment with ISIS 15534 results from the nuclear accumulation of GR in a form that is capable of binding DNA yet still requires agonist to elicit maximal transcriptional activation.

Active Transport, Cell Nucleus↗

PubMed2001

Effect of solid surface composition on the migration of tributyltin in groundwater.

Tributyltin (TBT) is the most important organotin compound that has been introduced into aquatic ecosystems. A better understanding of its interactions with solid surfaces is essential to estimate the possibilities of TBT migration through subsurface environments. For this purpose, TBT sorption onto a porous matrix of natural origin, a quartz sand as an aquifer material, was studied at low concentration levels with a monodirectional model of column type allowing sequential investigation of sorption and desorption processes. Different treatments of the solid phase were performed by injecting alkaline solutions, NaOH at pH 10.8 or NaClO-NaCl at pH 11.5, by decreasing the ionic strength or by adding kaolinite to change the surface composition and properties. The removal of iron and aluminum (hydr)oxides from the sand surface did not affect so much the sorption (decrease in 14% as compared to sorption on the raw sand). The original use of X-ray photoelectron spectroscopy to control treatment efficiency and to characterize sand surface modifications permitted to relate TBT sorption onto the aquifer material to quartz, the main component of the sand, and clay minerals (mainly kaolinite) present at trace levels at the sand surface. A first attempt of transport modeling with these two surface sites showed the consistency of our assumption. Moreover, estimation of Langmuir-type constants showed that TBT sorption affinity for the quartz surface (KL = 26.7 L micromol(-1)) was much greater than for kaolinite (KL = 6.3 L micromol(-1)).

Adsorption↗