Increased risk for lead exposure in children through consumption of produce grown in urban soils.

Childhood Pb exposure is associated with a multitude of poor health outcomes. In food-insecure areas, growing fresh produce in backyard gardens or on vacant industrial properties is seen as an option for parents. The question arises, could Pb accumulate in consumable tissues of common produce when grown in metals-rich soils at concentrations that would pose a risk to children. This study investigated factors contributing to the accumulation of Pb in consumable tissues of nine common produce crops grown in metals-rich soils from backyard gardens and a former industrial property. Pb in consumable tissues was directly quantified at concentrations less than 1 µg g-1 via X-ray fluorescence (XRF) using protocols specifically developed for use in plant matrices. The accumulation of Pb in prepared raw consumable tissues in three Pb-rich soils was the greatest in modified taproot crops (mean Pb of 11.8 ± 14.6 µg g-1; turnip, beetroot, radish, carrot), with lesser concentrations in fruits (mean Pb of 2.0 ± 3.0 µg g-1; tomato, pepper), and potatoes (mean Pb of 0.7 ± 1.1 µg g-1). An exposure risk evaluation using the USFDA IRL for Pb indicates that consumption of less than 1 g of certain produce grown in this study, including produce grown in garden soils from residential properties, drastically increases the risk of Pb exposure in children. This study further indicates that the proportion of Pb contributed to the daily body burden in children from food is far greater than previously understood, and in all modeled cases, the contribution of Pb from food on a daily basis far outweighs the contribution of Pb from drinking water. For an average child, after addressing over-riding soil/dust impacts, addressing food quality is critical to minimizing Pb exposure.

Forty-Nine Major and Trace Element Concentrations Measured in Soil Reference Materials NIST SRM 2586, 2587, 2709a, 2710a and 2711a Using ICP-MS and Wavelength Dispersive-XRF.

Excellent agreement was noted in the concentration of major and trace elements in five NIST soil reference materials (NIST SRM 2586, 2587, 2709a, 2710a and 2711a) between measurement results from wavelength dispersive-XRF and ICP-MS from two independent laboratories, and NIST certificate of analysis and literature data. We describe the variability in concentrations of up to forty-nine elements (plus loss on ignition) and provide values for up to twenty-one elements previously uncharacterised by NIST in these soil RMs. The additional characterisation provided in this investigation can be utilised to reduce the measurement bias of custom calibration routines and improve the quality of control checks developed using these NIST RMs.

Comparison of the transport of Bacteroides fragilis and Escherichia coli within saturated sand packs.

Pathogens in groundwater accounted for ∼50% of waterborne disease outbreaks in the United States between 1971 and 2006. The fast and reliable detection of groundwater microbial contamination and the identification of the contamination sources are of critical importance to the protection of public health. Recent studies suggested that fecal anaerobe Bacteriodes spp. could be employed as an effective tool for surface water microbial source tracking (MST). The usefulness of Bacteroides spp. for groundwater MST depends strongly on its mobility within the subsurface system. This research provides laboratory results comparing transport and attachment of E. coli K12 and B. fragilis within packed quartz sands. The results indicate that at low ionic strengths both E. coli K12 and B. fragilis are readily transported through saturated sand packs. At higher ionic strengths such as may be found near concentrated sources of fecal contamination, B. fragilis displayed significantly higher mobility than E. coli K12. Analysis of the extended Derjaguin-Landau-Verweu-Overbeek (XDLVO) energy interactions for both types of bacteria showed a significant repulsive energy barrier exists between the sand surface and the bacteria, precluding attachment directly to the sand surface. However a secondary minimum energy level exists under higher ionic strength conditions. The depth of this energy low is greater for E. coli K12, which results in greater attachment of E. coli K12 than of B. fragilis. The high mobility of B. fragilis suggests that it represents a promising tool for the detection of groundwater fecal contamination as well as the identification of the microbial sources.

Demonstration of a method for the direct determination of polycyclic aromatic hydrocarbons in submerged sediments.

We describe the development of a novel method for real-time in situ characterization of polycyclic aromatic hydrocarbons (PAHs) in submerged freshwater sediments. Laser-induced fluorescence (LIF) spectroscopy, a mature technique for PAH characterization in terrestrial sediments, was adapted for shipboard use. A cone penetrometer-type apparatus was designed for probe penetration at a constant rate (1 cm/s) to a depth of 3 m. A field-portable LIF system was used for in situ measurements in which the output of a pulsed excimer laser was transmitted by optical fiber to a sapphire window (6.4-mm o.d.) in the probe wall; fluorescent emission was collected by a separate optical fiber for transmission to the spectrometer on deck. Four wavelengths (340, 390, 440, 490 nm) were selected via optical delay lines, and multiple-wavelength waveforms were created. These multiple-wavelength waveforms contain information on the fluorescence frequency, intensity, and emission decay rate. Field testing was conducted at 10 sites in Milwaukee Harbor (total PAH concentrations ranged from approximately 10 to 650 microg/g); conventional sediment core samples were collected concurrently. The core samples were analyzed by EPA methods 3545 (pressurized fluid extraction, PFE) and 8270C (gas chromatography-mass spectrometry, GC-MS) for PAHs. A partial least-squares regression (PLSR) model wasthen created based on laboratory LIF measurements and PFE-GC-MS of the core samples. The PLSR model was applied to the in situ field test data, and 13 of the 16 EPA-regulated PAHs were quantified with a relative error of <30% overall (the remaining three PAHs were found at levels insufficient to quantify). We additionally describe preliminary source apportionment relationships that were revealed by the PLSR model for the in situ LIF measurements.