Richard Gibson

The analysis of a group of acidic pharmaceuticals, carbamazepine, and potential endocrine disrupting compounds in wastewater irrigated soils by gas chromatography-mass spectrometry.

The analysis of pharmaceuticals and potential endocrine disruptors in the environment has rightly concentrated on their presence in wastewaters and possible contamination of receiving bodies, such as groundwaters. However, wastewater is increasingly being reused for irrigation and in order to fully understand the environmental fate of these compounds, reliable methods for their analysis in soil are required, of which there are relatively few available. This article reports a method for a range of acidic pharmaceuticals, carbamazepine, and endocrine disrupting compounds in soils with final analysis by gas chromatography-mass spectrometry. Two soil types (Phaeozom and Leptosol) and three fortification levels were used to validate the method. Recoveries of acidic pharmaceuticals varied between 62 and 102%, carbamazepine from 75 to 118%, and potential endocrine disruptors between 54 and 109%; most recoveries were between 75 and 95% and relative standard deviations were generally less than 10%. Detection limits were between 0.25 and 2.5 ng/g except for phthalates and 4-nonylphenols (25 ng/g). The method was used to analyze soils where untreated wastewaters have been used to irrigate crops for approximately 90 years. Concentrations of acidic pharmaceuticals in the soil were <1 ng/g and potential endocrine disruptors varied from below the limit of detection (estrone, 17beta-estradiol, and 17alpha-ethinylestradiol) to 2079 ng/L (bis-diethylhexyl phthalate). This data indicated that despite the continuous application of the contaminants over many years, concentrations were generally lower than those expected to be contributed by a single irrigation event. Only carbamazepine, at concentrations of 6.48 ng/g (in Phaeozem) and 5.14 ng/g (in Leptosol), showed any evidence of persistence in the soils analyzed.

Accumulation and leaching potential of some pharmaceuticals and potential endocrine disruptors in soils irrigated with wastewater in the Tula Valley, Mexico.

The reuse of wastewater for irrigation of agricultural land is a well established practice but introduces many contaminants into the terrestrial environment including pharmaceuticals and personal care products. This study reports the persistence and leaching potential of a group of acidic pharmaceuticals, carbamazepine, and three endocrine disruptors in soils from the Tula Valley in Mexico, one of the largest irrigation districts in the world that uses untreated wastewater. After irrigation of soil columns with fortified wastewater over the equivalent of one crop cycle, between 0% and 7% of the total added amounts of ibuprofen, naproxen, and diclofenac and between 0% and 25% of 4-nonylphenol, triclosan, and bisphenol-A were recovered from the soil profiles. Carbamazepine was more persistent, between 55% and 107% being recovered. Amounts in leachates suggested that movement through the soil was possible for all of the analytes, particularly in profiles of low organic matter and clay content. Analysis of soil samples from the Tula Valley confirmed the general lack of accumulation of the acidic pharmaceuticals (concentrations from below the limit of detection to 0.61 μgkg(-1)) and endocrine disruptors (concentrations from below the limit of detection to 109 μgkg(-1)) despite continual addition through regular irrigation with untreated wastewater; there was little evidence of movement through the soil profiles. In contrast, carbamazepine was present in horizon A of the soil at concentrations equivalent to several years of additions by irrigation (2.6-7.5 μgkg(-1)) and was also present in the deeper horizons. The persistence and mobility of carbamazepine suggested a potential to contaminate groundwater.

The influence of particle size and structure on the sorption and oxidation behaviour of birnessite: II. Adsorption and oxidation of four polycyclic aromatic hydrocarbons

Environmental context Sorption and oxidation reactions at mineral surfaces can substantially influence the mobility and toxicity of environmental contaminants. An understanding of the factors that control these reactions is crucial for predicting the fate of contaminant species. We investigate the reactivity of manganese oxides towards polycyclic aromatic hydrocarbons, persistent organic compounds of environmental concern. Abstract Birnessites are ubiquitous components of natural systems and may exert a significant influence on the mobility and toxicity of different types of contaminants, including organic species. Their small particle sizes and internal structure provide them with high sorption capacities and oxidising abilities for redox sensitive species. In the present work, the interactions of two MnIV birnessites (δ-MnO2 and acid birnessite) of different particle sizes and layer vacancy contents were investigated with four hydrophobic polycyclic aromatic hydrocarbons (PAHs) of three and four rings. Fluorene and anthracene were oxidised to produce the corresponding and less toxic quinones by both birnessites, but at a higher rate and extent by δ-MnO2. Phenanthrene and fluoranthene only adsorbed to δ-MnO2 but not to acid birnessite. The higher reactivity of δ-MnO2 is only partly explained by its higher specific surface area (114 v. 39m2g–1), i.e. by its smaller particle size. The repulsive effect of water molecules from hydrated cations sorbed on layer vacant sites is most likely decisive, because acid birnessite shows a considerably larger content of these vacancies. The results presented provide a fundamental understanding of the potential influence of birnessite minerals on the attenuation of low molecular weight PAHs in environments with low organic matter content, such as deep aquifers.