Surface flux and vertical profile of dimethyl sulfide in acid sulfate soils at Cudgen Lake, northern New South Wales, Australia.

A dimethyl sulfide (DMS) vertical concentration profile and DMS surface emission flux were quantified in undisturbed acid sulfate soils (ASS) at Cudgen Lake on the north coast of New South Wales, Australia. A deuterated internal standard was used to account for soil adsorption characteristics. The DMS vertical concentration profile increased exponentially from 0.6 m depth to the surface layer. This profile reflected the adsorption properties of the ASS horizons present and the experimentally determined octanol/water partition coefficient for DMS of 1.36, suggesting that DMS would be mobilised in the soil water medium for upward translocation in time due to surface evaporation. The organic material in the oxidised ASS crustal layer had a chemically strong adsorption affinity for DMS, which appeared to restrain its emission from surface soil particles to the atmosphere. The seasonally averaged DMS surface flux estimate from the Cudgen Lake ASS was 9 ng S m-2 min-1, which is relatively low by comparison to DMS fluxes reported from other wetland soils such as salt-marshes and acidic peat bogs. The worldwide annual average DMS emission from ASS was estimated to be 1.14 × 10-3 Tg S, which is globally insignificant by comparison to DMS emission from the world's oceans.

Coral reef aerosol emissions in response to irradiance stress in the Great Barrier Reef, Australia.

We investigate the correlation between stress-related compounds produced by corals of the Great Barrier Reef (GBR) and local atmospheric properties-an issue that goes to the core of the coral ecosystem's ability to survive climate change. We relate the variability in a satellite decadal time series of fine-mode aerosol optical depth (AOD) to a coral stress metric, formulated as a function of irradiance, water clarity, and tide, at Heron Island in the southern GBR. We found that AOD was correlated with the coral stress metric, and the correlation increased at low wind speeds, when horizontal advection of air masses was low and the production of non-biogenic aerosols was minimal. We posit that coral reefs may be able to protect themselves from irradiance stress during calm weather by affecting the optical properties of the atmosphere and local incident solar radiation.

The relative abundance of dimethylsulfoniopropionate (DMSP) among other zwitterions in branching coral at Heron Island, southern Great Barrier Reef.

Dimethylsulfoniopropionate (DMSP) and eleven other target zwitterions were quantified in the branch tips of six Acropora species and Stylophora pistillata hard coral growing on the reef flat surrounding Heron Island in the southern Great Barrier Reef (GBR), Australia. Hydrophilic interaction liquid chromatography mass spectrometry (HILIC-MS) was used for sample analysis with isotope dilution MS applied to quantify DMSP. The concentration of DMSP was ten times greater in A. aspera than A. valida, with this difference being maintained throughout the spring, summer and winter seasons. In contrast, glycine betaine was present in significantly higher concentrations in these species during the summer than the winter. Exposure of branch tips of A. aspera to air and hypo-saline seawater for up to 1 h did not alter the concentrations of DMSP present in the coral when compared with control samples. DMSP was the most abundant target zwitterion in the six Acropora species examined, ranging from 44-78% of all target zwitterions in A. millepora and A. aspera, respectively. In contrast, DMSP only accounted for 7% in S. pistillata, with glycine betaine and stachydrine collectively accounting for 88% of all target zwitterions in this species. The abundance of DMSP in the six Acropora species examined points to Acropora coral being an important source for the biogeochemical cycling of sulfur throughout the GBR, since this reef-building branching coral dominates the coral cover of the GBR. Graphical Abstract HILIC-MS extracted ion chromatogram showing zwitterionic metabolites from the branching coral Acropora isopora.

Quantification of dimethylsulfoniopropionate (DMSP) in Acropora spp. of reef-building coral using mass spectrometry with deuterated internal standard.

Dimethylsulfoniopropionate (DMSP) in scleractinian coral is usually analysed indirectly as dimethylsulfide (DMS) using gas chromatography (GC) with a sulfur-specific detector. We developed a headspace GC method for mass spectral analysis of DMSP in branching coral where hexa-deuterated DMSP (d 6 -DMSP) was added to samples and standards to optimise the analytical precision and quantitative accuracy. Using this indirect HS-GC-MS method, we show that common coral sample handling techniques did not alter DMSP concentrations in Acropora aspera and that endogenous DMS was insignificant compared to the store of DMSP in A. aspera. Field application of the indirect HS-GC-MS method in all seasons over a 5-year period at Heron Island in the southern Great Barrier Reef indicated that healthy colonies of A. aspera ordinarily seasonally conserve their branch tip store of DMSP; however, this store increased to a higher concentration under extended thermal stress conditions driven by a strong El Niño Southern Oscillation event. A liquid chromatography mass spectral method (LC-MS) was subsequently developed for direct analysis of DMSP in branching coral, also utilising the d 6 -DMSP internal standard. The quantitative comparison of DMSP in four species of Acropora coral by indirect HS-GC-MS and direct LC-MS analyses gave equivalent concentrations in A. aspera only; in the other three species, HS-GC-MS gave consistently higher concentrations, indicating that indirect analysis of DMSP may lead to artificially high values for some coral species. Graphical Abstract Dimethylsulfoniopropionate (DMSP) was quantified in Acropora spp. of branching coral using deuterated stable isotope dilution mass spectrometry.

The development of an efficient mass balance approach for the purity assignment of organic calibration standards.

The purity determination of organic calibration standards using the traditional mass balance approach is described. Demonstrated examples highlight the potential for bias in each measurement and the need to implement an approach that provides a cross-check for each result, affording fit for purpose purity values in a timely and cost-effective manner. Chromatographic techniques such as gas chromatography with flame ionisation detection (GC-FID) and high-performance liquid chromatography with UV detection (HPLC-UV), combined with mass and NMR spectroscopy, provide a detailed impurity profile allowing an efficient conversion of chromatographic peak areas into relative mass fractions, generally avoiding the need to calibrate each impurity present. For samples analysed by GC-FID, a conservative measurement uncertainty budget is described, including a component to cover potential variations in the response of each unidentified impurity. An alternative approach is also detailed in which extensive purification eliminates the detector response factor issue, facilitating the certification of a super-pure calibration standard which can be used to quantify the main component in less-pure candidate materials. This latter approach is particularly useful when applying HPLC analysis with UV detection. Key to the success of this approach is the application of both qualitative and quantitative (1)H NMR spectroscopy.

Changes in manganese and lead in the environment and young children associated with the introduction of methylcyclopentadienyl manganese tricarbonyl in gasoline--preliminary results.

A 4-year longitudinal study is being conducted to evaluate potential changes to the environment and exposure of young children associated with the introduction of methylcyclopentadienyl manganese tricarbonyl (MMT) into Australia in 2001. The cohort consists of 57 females and 56 males, with an age range of 0.29-3.9 years. Samples are collected every 6 months from children in residences located at varying distances from major traffic thoroughfares in Sydney. Environmental samples include air, house, and daycare center dustfall, soil, dust sweepings, and gasoline; samples from the children include blood, urine, handwipes prior to and after playing outdoors, and a 6-day duplicate diet. All samples are analyzed for a suite of 20 elements using inductively coupled plasma methods. Results are presented for the first three 6-month sampling periods for lead (Pb) and manganese (Mn). For dustfall accumulation, expressed as metal concentration/m2/30 days, there was no significant difference between homes and daycare centers for either Pb or Mn, no significant change over the three sampling periods (time) for Pb or Mn, and a positive relationship between "traffic exposure" (traffic volume and proximity to the road) and Pb but not Mn. Lead concentrations in soil was a significant predictor for Pb in the house dustfall. For handwipes, the concentrations of Pb and Mn in wipes taken from children after playing outdoors was usually significantly greater than those for wipes taken prior to playing. There was no significant association between the concentrations of either Pb or Mn in handwipes and traffic exposure, and there was no significant association between Pb concentrations in the handwipes and gender, although the latter showed a marginally significant association for Mn (P = 0.053). Age was related to Pb level in the handwipes, with older subjects having higher Pb levels, and there were significant decreases in Pb and Mn concentrations over time. Dustfall accumulation was a significant predictor for Pb in the handwipes, and dust sweepings were a significant predictor of Mn in handwipes. Blood lead (PbB) concentrations ranged from 0.6 to 19 microg/dL (GM 2.6) (n = 269), and manganese in blood (MnB) ranged from 1.8 to 45 microg/L (GM 11.6) (n = 254). There was no significant difference between females and males for either mean PbB or MnB; over time there was a significant decline in PbB but no significant change in MnB. The only significant predictor for PbB was dustfall accumulation, although dietary intake may also be important, and the only significant predictor for MnB was Mn in handwipes prior to playing. At this early stage of the investigation we have not been able to detect any increases in Mn in these environmental samples or blood samples potentially associated with the use of MMT; in fact the Mn levels in handwipes declined over time.

DMS photochemistry during the Asian dust-storm period in the Spring of 2001: model simulations vs. field observations.

This study examines the local/regional DMS oxidation chemistry on Jeju Island (33.17 degrees N, 126.10 degrees E) during the Asian dust-storm (ADS) period of April 2001. Three ADS events were observed during the periods of April 10-12, 13-14, and 25-26, respectively. For comparative purposes, a non-Asian-dust-storm (NADS) period was also considered in this study, which represents the entire measurement periods in April except the ADS events. The atmospheric concentrations of DMS and SO2 were measured at a ground station on Jeju Island, Korea, as part of the ACE-Asia intensive operation. DMS (means of 34-52 pptv) and SO2 (means of 0.96-1.14 ppbv) levels measured during the ADS period were higher than those (mean of 0.45 ppbv) during the NADS period. The enhanced DMS levels during the ADS period were likely due to the increase in DMS flux under reduced oxidant levels (OH and NO3). SO2 levels between the two contrasting periods were affected sensitively by some factors such as air mass origins. The diurnal variation patterns of DMS observed during the two periods were largely different from those seen in the background environment (e.g., the marine boundary layer (MBL)). In contrast to the MBL, the maximum DMS value during the ADS period was seen in the late afternoon at about sunset; this reversed pattern appears to be regulated by certain factors (e.g., enhanced NO3 oxidation). The sea-to-air fluxes of DMS between the ADS and NADS periods were calculated based on the mass-balance photochemical-modeling approach; their results were clearly distinguished with the values of 4.4 and 2.4 micromole m(-2) day(-1), respectively. This study confirmed that the contribution of DMS oxidation to observed SO2 levels on Jeju Island was not significant during our study period regardless of ADS or NADS periods.

Monitoring of reduced sulfur compounds in the atmosphere of Gosan, Jeju Island during the Spring of 2001.

The atmospheric concentrations of dimethylsulfide (DMS) and carbon disulfide (CS2) were measured concurrently with relevant environmental parameters at Gosan, Jeju Island, Korea during 5-26 April 2001. The mean concentrations for these two compounds were 18.7+/-17.9 and 6.4+/-9.9 pptv, respectively. Results of our analysis indicated that relative temporal variations between DMS and CS2 can be best described by dividing the whole data set into three different periods which reflect the variable transport patterns of air masses into the study area. (Periods I, II, and III denote: 5-10, 10-18, and 19-26 April.) The environmental conditions during those three periods varied greatly. The effects of continental and/or oceanic processes were evident for certain periods, yielding diverse relationships between DMS and CS2 in both absolute and relative terms. Most observed variations were best explained in terms of an interplay between source/sink processes and air mass transport patterns. The sea-to-air flux of DMS, when estimated using our measurement data during this study period, was approximately 4 micromole m(-2)d(-1).