Lyndon Berwick

Molecular characterisation of the dissolved organic matter of wastewater effluents by MSSV pyrolysis GC-MS and search for source markers.

Microscale sealed vessel pyrolysis (MSSVpy) was used to characterise the hydrophobic (HPO) and colloid (COL) fractions of dissolved organic matter (DOM) from the effluents (EFFs) of two waste water treatment plants (WWTPs) and several primary source waters (SWs). The EFFs showed a large range of anthropogenically sourced organics - including the metabolites of industrial chemicals (e.g., dioxanes, n- and sec-alkyl substituted benzenes and long chain alkyl phenols), pharmaceuticals (e.g., N- and S-heterocycles) and human waste (e.g., S- and N-organics, steranes/sterenes) - as well as high concentrations of alkyl aromatic and N-organic products (e.g., alkyl indoles, carbazoles and β-carbolines) attributed to the treatment biota. Some anthropogenic chemicals are potentially toxic at even trace levels, whilst the N-organics may be precursors for toxic N-disinfection by-products. Much lower concentrations of just a few of the anthropogenic and N-organic products were detected by more traditional flash pyrolysis (Flash-py) of the EFF samples, reflecting the higher sensitivity of MSSVpy to many chemical functionalities. Few of these products were detected in the corresponding MSSVpy analysis of the SWs, but these samples did show relatively high abundances of lignin (e.g., alkylphenols) and carbohydrate (e.g., furans) derived products. Their lower EFF abundances are consistent with efficient removal by the water treatment procedures applied. Conversely, the detection of the anthropogenics in the treated EFFs reflects their general resistance to treatment. Their occurrence in the HPO fractions isolated by XAD resin separation suggests a potential relationship with the structurally stable macromolecular fraction of the DOM.

The use of MSSV pyrolysis to assist the molecular characterisation of aquatic natural organic matter

Microscale sealed vessel pyrolysis (MSSVpy) with online gas chromatography mass spectrometry (GC-MS) was used with several other established and complementary analytical methods to robustly characterize the structure of aquatic natural organic matter (NOM) and to practically assess the analytical value of MSSVpy. The NOM used in the study was from North Pine (NP) reservoir, which is one of the major source waters supplying Brisbane, the capital city of the Australian state of Queensland. The reservoir has moderate dissolved organic carbon (DOC; 5mgL(-1)) levels and is impacted by algae which periodically occur in bloom proportions. The hydrophobic (HPO; 65% initial DOC) and transphilic (TPI; 12%) fractions showed H/C values >1, low UV(abs) and low aryl-C measured by NMR which are all indicative of low aromaticity. MSSVpy produced distinctly higher product concentrations than traditional flash pyrolysis and the molecular profile of the HPO and TPI fractions revealed by MSSVpy was correlated with the other analytical data to help establish their structural relevance. Prolific distributions of alkyl substituted aromatic (e.g., benzenes, naphthalenes) and hydroaromatic (e.g., tetralins) products detected in the HPO fraction were attributed to the aromatisation of terpanes and other aliphatic compounds from algal, and possibly also plant sources. Alkyl phenols also detected in HPO in high abundance, are probably from algal biopolymers, but may also reflect a contribution from non-methoxylated lignin units of catchment grasses. There was no analytical evidence of the dihydroxy or methoxy aromatic structures typical of wood lignin or tannin. N-organic pyrolysates (e.g., alkyl pyrroles, pyridines, indoles) of diagenetically altered proteins were concentrated in the TPI fraction. The quantitative importance of the N-organic moiety of the TPI fraction was corroborated by a low C/N ratio and distinctive amide and amine signals detected by (13)C NMR and FTIR. This integrated study demonstrates that the qualitative speciation provided by MSSVpy can make a significant contribution to the structural characterisation and source recognition of aquatic NOM.

Distribution of iron- and sulfate-reducing bacteria across a coastal acid sulfate soil (CASS) environment: implications for passive bioremediation by tidal inundation

Coastal acid sulfate soils (CASS) constitute a serious and global environmental problem. Oxidation of iron sulfide minerals exposed to air generates sulfuric acid with consequently negative impacts on coastal and estuarine ecosystems. Tidal inundation represents one current treatment strategy for CASS, with the aim of neutralizing acidity by triggering microbial iron- and sulfate-reduction and inducing the precipitation of iron-sulfides. Although well-known functional guilds of bacteria drive these processes, their distributions within CASS environments, as well as their relationships to tidal cycling and the availability of nutrients and electron acceptors, are poorly understood. These factors will determine the long-term efficacy of “passive” CASS remediation strategies. Here we studied microbial community structure and functional guild distribution in sediment cores obtained from 10 depths ranging from 0 to 20 cm in three sites located in the supra-, inter- and sub-tidal segments, respectively, of a CASS-affected salt marsh (East Trinity, Cairns, Australia). Whole community 16S rRNA gene diversity within each site was assessed by 454 pyrotag sequencing and bioinformatic analyses in the context of local hydrological, geochemical, and lithological factors. The results illustrate spatial overlap, or close association, of iron-, and sulfate-reducing bacteria (SRB) in an environment rich in organic matter and controlled by parameters such as acidity, redox potential, degree of water saturation, and mineralization. The observed spatial distribution implies the need for empirical understanding of the timing, relative to tidal cycling, of various terminal electron-accepting processes that control acid generation and biogeochemical iron and sulfur cycling.