Experimental Zn(II) retention in a sandy loam soil by very small columns

The use of column experiments, usually performed to better approximate field conditions, may provide information that is not available from batch experiments. In such experiments heavy metals are often adsorbed until saturation followed by desorption experiments. When the affinity of the metal to soil is high, the retention factor (R) could be greater than thousands and the duration of experiments can become impractically long. In order to use reasonable laboratory time, the flow rate should be increased or the column size decreased. The increase in flow rate produces undesirable kinetic and dispersion effects, so we used very small soil columns (pore volume = 0.31–0.70 ml) and relatively high flow rates (0.03–0.12 ml min⁻¹) in studies of Zn(II) adsorption and retention in soils. Conservative tracer flow column experiments under saturation conditions were carried out to determine flow parameters for different flow rates. Column pore volume (V_p), Peclet numbers (Pe) and longitudinal dispersion coefficients (D_L) were determined from breakthrough curves. The effect of type of electrolyte and ionic strength on the Zn(II) retention onto soil was determined. The influence of flow rate and bed height on the retention coefficient and on the mass transfer zone was also studied. The effect of different influent Zn(II) concentrations on the R values obtained was analyzed. Freundlich parameters from column experiments were compared with batch ones. The leaching efficiency of different electrolytes, salts of weak organic acids and EDTA was also studied.     

Behavioral and life-history evidence for interspecific competition in the larvae of two heliconian butterflies

Interspecific competition in herbivorous insects remains a controversial issue. To date, many studied systems have not met assumptions of the traditional competition theory, and a new paradigm has been emerging. We examined the behavioral and life-history consequences of common host plant use of Heliconius erato and Dryas iulia (Nymphalidae) in relation to Passiflora suberosa (Passifloraceae). Larvae of the former use the apical portion of this host; the latter is presumably able to explore all plant parts. We assessed host use pattern in relation to leaf age, when reared either alone (D. iulia) or together (D. iulia and H. erato). Larval feeding choice tests with respect to leaf age were performed, and performance was recorded. Observations were made to assess antagonistic behavior of H. erato and D. iulia towards each other, if any. Similarly to H. erato, D. iulia fed on the young leaves significantly more than the mature ones; larvae were not induced to prefer mature leaves. First instars of H. erato used only the apical parts of P. suberosa and displayed aggressive behavior towards D. iulia, which moved to the lower shoot portions. Larval mortality and development time of both species significantly increased when reared together; such performance costs were more pronounced in D. iulia than H. erato. Our study gathers evidences that use of P. suberosa by these heliconian butterflies represent a case of competitive exclusion resulting in niche differentiation, where costs are higher for D. iulia than H. erato.     

Mercury and selenium concentrations in the crab Callinectes arcuatus from three coastal lagoons of NW Mexico

Environmental Science and Pollution Research - Mercury and selenium concentrations and Se:Hg molar ratio in edible muscle and hepatopancreas of the crab Callinectes arcuatus from coastal lagoons of...     

Four challenges when conducting bibliometric reviews and how to deal with them

Environmental Science and Pollution Research - The evidence base in environmental sciences is increasing steadily. Environmental researchers have been challenged to handle massive volumes of data...     

Lethal and sublethal effects of the natural and healthy spinosad-based formulation Tracer™ on tadpoles of two neotropical species

Environmental Science and Pollution Research - This paper presents the first acute toxicity data of the natural insecticide spinosad in amphibians. The sensitivity of two neotropical sympatric...     

Vegetation productivity under climate change depends on landscape complexity in tropical drylands

Mitigation and Adaptation Strategies for Global Change - All Clean Development Mechanism (CDM) projects are designed to contribute to the sustainable development of the host country. Livelihood is...     

Effects of lead exposure on salivary glands of rats: insights into the oxidative biochemistry and glandular morphology

Environmental Science and Pollution Research - This study aimed to investigate the effects of lead (Pb) exposure on parotid and submandibular glands through morphological aspects as well as the...     

Detection and quantitative analysis of 21 veterinary drugs in river water using high-pressure liquid chromatography coupled to tandem mass spectrometry

Introduction

The use of veterinary drugs in food production focuses on the control and improvement of animal health. The disadvantage of this practice is that pharmaceuticals and their metabolites are released into the environment, finding their way to natural water systems and becoming a potential risk to non-target organism.

Methods

This paper reports the development and validation of a quantitative method, based on high-performance liquid chromatography coupled to tandem mass spectrometry, for the simultaneous analysis of 21 veterinary drugs, antimicrobials, corticosteroids, coccidiostats and antifungal agents, in surface water.

Results

The precision of the method was established by calculating the mean recoveries, which were in the range of 94?C101%. The developed method was employed to conduct the first monitoring study on the presence of veterinary drugs in the Galicia region, Northwest of Spain and was applied to 235 surface water samples. Eleven veterinary drugs were detected at concentrations from below the limit of quantification to 2,978.6?ng?L^?1. Limits of detection and quantification were in the range of 6.2 (betamethasone, cortisone, decoquinate, dexamethasone, maduramycin, monensin, narasin, salinomycin, sulfachloropyridazine, sulfamethoxypyridazine and trimethoprim) to 12.5?ng?L^?1 (for the rest of the selected drugs) and 12.5 (betamethasone, cortisone, decoquinate, dexamethasone, maduramycin, monensin, narasin, salinomycin, sulfachloropyridazine, sulfamethoxypyridazine and trimethoprim) to 25.0?ng?L^?1 (for the remaining pharmaceuticals), respectively.

Conclusion

Sulfonamides were the group most frequently found, which are widely used in veterinary medicine.     

Development of a green and efficient methodology for the heterocyclic aromatic amine determination in biomass samples generated from cigarette combustion and tobacco

Environmental Science and Pollution Research - A green methodology was developed for the analysis of ten heterocyclic aromatic amines (HAAs) in biomass samples from cigarette combustion such as...