Paul Northrup

Control of sulfidogenesis through bio‐oxidation of H2S coupled to (per)chlorate reduction

We investigated H2S attenuation by dissimilatory perchlorate-reducing bacteria (DPRB). All DPRB tested oxidized H2S coupled to (per)chlorate reduction without sustaining growth. H2S was preferentially utilized over organic electron donors resulting in an enriched (34S)-elemental sulfur product. Electron microscopy revealed elemental sulfur production in the cytoplasm and on the cell surface of the DPRB Azospira suillum. Based on our results, we propose a novel hybrid enzymatic-abiotic mechanism for H2S oxidation similar to that recently proposed for nitrate-dependent Fe(II) oxidation. The results of this study have implications for the control of biosouring and biocorrosion in a range of industrial environments.

Surface loading effects on orthophosphate surface complexation at the goethite/water interface as examined by extended X-ray Absorption Fine Structure (EXAFS) spectroscopy

To investigate the effect of P surface loading on the structure of surface complexes formed at the goethite/water interface, goethite was reacted with orthophosphate at P concentrations of 0.1, 0.2, and 0.8 mmol L(-1) at pH 4.5 for 5 days. The P concentrations were chosen to ensure that P loadings at the surface would allow one to follow the transition between adsorption and surface precipitation. Extended X-ray Absorption Fine Structure (EXAFS) spectra were collected in fluorescence mode at the P K-edge at 2150 eV. The structural parameters were obtained through the fits of the sorption data to single and multiple scattering paths using Artemis. EXAFS analysis revealed a continuum among the different surface complexes, with bidentate mononuclear ((2)E), bidentate binuclear ((2)C) and monodentate mononuclear ((1)V) surface complexes forming at the goethite/water interface under the studied conditions. The distances for P-O (1.51-1.53Å) and P-Fe (3.2-3.3Å for bidentate binuclear and around 3.6Å for mononuclear surface complexes) shells observed in our study were consistent with distances obtained via other spectroscopic techniques. The shortest P-Fe distance of 2.83-2.87Å was indicative of a bidentate mononuclear bonding configuration. The coexistence of different surface complexes or the predominance of one sorption mechanism over others was directly related to surface loading.

Residence time and pH effects on the bonding configuration of orthophosphate surface complexes at the goethite/water interface as examined by Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy

Identifying the mechanisms by which P is bound to soils and soil constituents is ultimately important as they provide information on the stability of bound species and their reactivity in the environment. EXAFS studies were carried out to provide information on how the local chemical environment of sorbed P changes as an effect of pH and time. Goethite was reacted with orthophosphate at a P concentration of 0.8mmolL(-1) P at pH 3.0, 4.5 and 6.0. The residence time effect on the mechanisms of P sorption on goethite was also evaluated for two different reaction times, 5 and 18days, on goethite suspensions reacted at pH 4.5. The objective of this study was to understand how P sorption mechanisms change over a wide pH range when subjected to P concentrations above the P saturation ratio of goethite. Phosphorus K-edge EXAFS spectra were collected at 2150eV in fluorescence mode and the structural parameters were obtained through the fits of sorption data using Artemis. The monodentate surface complex was shown to be the predominant mechanism by which P sorbs at the goethite surface under the experimental conditions. The lack of a discrete Fe-P shell and the presence of highly disordered structures, particularly, at R-space ⩾3.5 suggested the formation of P surface precipitates at the goethite/water interface.

Software development for multi-wavelength image correlation

The National Synchrotron Light Source II (NSLSII) at Brookhaven National Laboratory offers a large variety of synchrotron based imaging techniques that provide users with structural and chemical information of materials at the nanoscale. Multiple imaging techniques such as light microscopy, infrared imaging and X-ray fluorescence microscopy are commonly used to correlate information from the same sample. Correlating the important information in such images presents a large technological challenge because the various imaging techniques generate images of different sizes and spatial resolutions. To overcome this challenge, there are two goals involving software development: the first to identify a method for using fiducial markers to correlate visible light images with Xray fluorescence microscope images at the micro- to nanoscale and the second to develop software for the fusion (i.e. overlap) and correlation of these images. Numerous programs were identified to complete this project such as Matlab, Python, Photoshop, ImageJ and Fiji. After doing much research and testing a variety of these programs, it was clear that Fiji was the best and most efficient program for solving these challenges. It has the capability to align images automatically by converting the image to 8-bit gray scale, finding the maxima, i.e. darkest points, and stacking as well as corresponding these max points to align images with pin point accuracy. Moreover, it has the capability to use manually chosen fiducial point markers where the user inputs landmarks or fiducial points on the image and the program triangulates the points to align them. In addition, a user manual was written so that other synchrotron users can benefit from this methodology as well. Overall, this process will prove to be very useful in the future of the laboratory in cases where image correlation is vital. The majority of photon sciences involve correlating images and analyzing the data that come out.

Technical Report: Growth of Environmental Science at the NSLS

In the 25 years since the National Synchrotron Light Source (NSLS) began operations, synchrotron “user facilities” have had a growing impact on research in molecular environmental science (MES). For example, synchrotron-based analytical techniques have allowed researchers to determine the molecular-level speciation of environmentally relevant elements and evaluate their spatial distribution and phase association at very low concentration levels (low parts per million) with micrometer or nanometer resolution [1]. For the environmental scientist, one of the primary advantages of these synchrotron-based techniques is that samples need not be disturbed or destroyed for study; characterization can often be done in-situ in dilute and heterogeneous natural samples with no need for species separation, pre-concentration, or pre-treatment [2]. Liquids, hydrated solids, and biological samples can also often be directly analyzed, which is of fundamental importance in environmental science for understanding the molecular-scale processes that occur at mineral–water interfaces and in understanding how abiotic and biotic processes are involved in the distribution, mobility and ultimate fate of molecular species in the environment.

Developing EnviroSuite Resources at the National Synchrotron Light Source

The objective of Brookhaven National Laboratorys EnviroSuite Initiative is to develop the facilities, user support infrastructure, and techniques necessary to conduct world-class molecular environmental science research at the NSLS. This is intended to benefit the research of ERSD-supported scientists, both through direct access and assistance and through the indirect benefits of a broader network of environmental scientists as collaborators and users. Much of the EnviroSuite research involves close collaboration with members of the Center for Environmental Molecular Science (CEMS), an EMSI based at BNL and nearby Stony Brook University and jointly supported by ERSD (Project 1023761, P. Kalb) and NSF. This offers unique opportunities to benefit from both national laboratory facilities and university resources. Other collaborators, from around the US and the world, investigate various aspects of the underlying molecular-scale processes in complex natural systems. In general, synchrotron techniques are ideal for studying the molecular-scale structures, chemical/physical interactions, and transformations that govern the macroscopic properties and processes (e.g. transport, bioavailability) of contaminants in the environment. These techniques are element-specific, non-destructive, and sensitive to the very low concentrations found in real-world samples.