Claudio Bravo-Linares

Temporal trends and identification of the sources of volatile organic compounds in coastal seawater

Volatile Organic Compounds (VOCs) in the marine environment are produced by biogenic sources (marine macroalgae, phytoplankton, sediments, etc.) as well from anthropogenic sources. The temporal variation of such VOCs was studied together with their relationship to biological, meteorological and physico-chemical factors. Sixty four different VOCs were quantified including halogenated (<LoD to 906 ng L(-1)), non-methane hydrocarbons (NMHC) (<LoD to 1539 ng L(-1)), mono-aromatics (<LoD to 4232 ng L(-1)), oxygenated (<LoD to 1539 ng L(-1)) and sulfur containing compounds (<LoD to 160 ng L(-1)). The analyses were performed employing solid phase microextraction (SPME) coupled to gas chromatography/mass spectrometry (GC/MS) analysis. Pigments such as chlorophyll a correlated with halogenated compounds (e.g. chloroform and dichloromethane) and dimethylsulfide (DMS) was maximal during the spring bloom. Multivariate statistical analyses demonstrated seasonal changes in the VOC signature (more mono-aromatics and alkanes in the winter and halocarbons in the summer). Principal component analysis (PCA) demonstrated that physico-chemical and meteorological factors such as wind speed and water temperature can influence the detection of VOCs in surface waters as well their productions. Partial least squares (PLS) modelling highlighted the importance of the microalgae signature in spring while macroalgae and sediments dominated at other times. Short term variability in concentrations and fluxes was due to such factors as tidal state, wind speed and seawater temperature. The atmospheric concentrations were significantly less than any regulatory values although no measurements were made in eutrophic conditions.

PRODUCTION OF VOLATILE ORGANIC COMPOUNDS (VOCS) BY TEMPERATE MACROALGAE. THE USE OF SOLID PHASE MICROEXTRACTION (SPME) COUPLED TO GC-MS AS METHOD OF ANALYSIS

Volatile organic compounds (VOCs) are produced by macroalgae in response to environmental stresses. A novel approach using Solid Phase Microextraction (SPME) was used to quantify the production of several VOCs from eight common intertidal algal species from the UK (Ascophyllum nodosum (Linnaeus) Le Jolis, Fucus vesiculosus (Linnaeus), Fucus serratus (Linnaeus), Laminaria digitata (Hudson) Lamouroux, Ulva lactuca (Linnaeus), Ulva intestinalis (Linnaeus), formerly known as Enteromorpha, Palmaria palmata (Linnaeus) Kuntze and Griffithsia flosculosa (J. Ellis) Batters). The volatile compounds included halogenated, sulphur containing, aldehydes, non-methane hydrocarbons (NMHC) and oxygenated species. Overall, the production of VOCs by these algae was not considerably different under illumination or in darkness; this suggests that the VOC production occurs during both algae photosynthesis and in other metabolic processes such as respiration or osmoregulation. Desiccation played an important role in the production of VOCs with greater production by macroalgae after desiccation. This production was related to the alga’s normal position within the intertidal zone; there was a lower production of VOCs for species growing near the high water mark and a greater production for algae taken from the low tide position. There were also species differences in the VOC profiles and quantities released. For example, chlorinated and oxygenated compounds were principally released by the brown alga Ascophyllum nodosum, while green algae such as Ulva lactuca and Ulva intestinalis released greater amounts of brominated, sulphur containing compounds, aldehydes and non-methane hydrocarbons than the other algae tested. The kelps (e.g. Laminaria digitata) had the greatest release of iodinated compounds such as diiodomethane. These processes make significant contributions to the VOCs in seawater and, by transfer to the atmosphere, in the coastal atmosphere.

Source Allocation of Aliphatic and Polycyclic Aromatic Hydrocarbons in Particulate-Phase (PM10) in the City of Valdivia, Chile

The concentration and signature of n-alkanes (n-C10 to n-C33) and 18 PAHs were determined in air filters across a year period (2010) in an urban area of the city of Valdivia, Chile. Filter samples were extracted using sohxlet apparatus and analyzed by GC-MS techniques. Concentrations of total hydrocarbons ranged from 45–352 ng.m−3 and total PAHs ranged from 2.93–78.01 ng.m−3. Concentrations of hydrocarbons during the summer were high (288–352 ng.m-3) and reduced when the autumn began (45–79 ng.m−3) to then increase almost linearly to the next summer. The drop in concentration was attributed in part to the significant reduction of traffic when summer ends as tourists leave the city (about 9–15% of the total cars circulating). Results from the chemometric technique of Polytopic Vector Analysis (PVA) indicated three main sources for the alkanes: biogenic (terrestrial plants), signatures of oil combustion, and an unconfirmed source which is thought to come from non specific organic matter degradation. Total PAHs correlated well with total particulate matter with a R2 = 0.94. Levels of PAHs in the atmosphere were higher during the winter (6.85–78.01 ng.m−3) period than the rest of the year (2.93–36.30 ng.m−3). PVA results indicate three key sources of PAHs and two of those sources derived from oil combustion and biomass burning.

Contributions of dioxins and furans to the urban sediment signature: The role of atmospheric particles

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzo-p-furans (PCDF) are widely distributed in the environment. The diverse production processes that form these compounds lead to a range of chemical signatures although weathering may cause changes to these signature over time and with increasing distance from their origin. Chemical signatures in sediments based on 17 PCDD/Fs were developed in Concepcion, a Chilean city in the middle of a complex hydrological system which contains several small urban freshwater bodies and the River Bio-Bio. The region has numerous industrial and domestic activities that may contribute PCDD/Fs to the environment. Sediments from urban lakes had higher concentrations of dioxins and furans (mean=941ng·kg-1) than either a remote lake (335ng·kg-1) located 32km from the city or marine samples (mean=124ng·kg-1). Up to 85% of the compounds present in all sediment samples could be explained by the chemical signature associated with airborne particulates leaving only 15-30% of the chemical signature potentially arising from other sources. The remote lake had higher proportions of the less-chlorinated compounds compared to the urban samples.

Source Apportionment of PAHs in Airborne Particulates (PM2.5) in Southern Chile

ABSTRACT Airborne particulate matter (PM2.5) are known environmental cotaminants. Nevertheless, it is not only the size of particulate matter that influences human health, but also its chemical composition. The chemical composition of the PAH suite in PM2.5 may be indicative of the source materials, typically combustion products. In this study, particulate matter (PM2.5) was collected using portable air samplers during all of 2013 and 2014 at five locations of the Los Rios Region, Valdivia, Chile. The quantity of PM2.5 collected was measured using gravimetric methods. Solvent extracts were analyzed for associated PAHs by means of GC-MS techniques. The concentrations of PM2.5 for all locations ranged from 2.8 to 386 µg/m3 for the autumn/winter periods and from 1.1 to 315 µg/m3 for the spring/summer periods. The mean concentrations of PM2.5 ranged from 11.9 to 112 µg/m3 in summer for all sites. The concentrations of PAHs for all locations ranged from 2.8 to 115 ng/m3 for the autumn/winter periods and from 0.3 to 32 ng/m3 for the spring/summer periods. To determine the possible sources of PM2.5, cross-plots, PCA, and PVA analyses were performed. The results demonstrated that biomass burning was the dominant source of PM2.5 at all locations during autumn/winter periods with PAHs having four to six rings; during the spring/summer periods, PAHs with two to three rings were more abundant and were related to petrogenic sources. The sources of PM2.5 in the different studied areas were similar and were related to season rather than to geography. Analysis of meteorological data for the region demonstrated that the background summer PM2.5 for the years studied was ∼8 µg/m3 while when temperatures decreased below 15°C, there was an exponential increase in the concentration of particles in the air.

PROGRESS OF TOTAL PETROLEUM HYDROCARBONS (TPHs) TREATED WITH BIOSOLVENT IN A SIMULATED OIL SPILL ON SANDY BEACH MICROCOSMS

Experiments with microcosms of sand corresponding to high, mid and low intertidal area were contaminated with crude oil and treated with biosolvent. Two treatments were done. The first (treatment 1) treating the sand 5 days before the event of contamination and the second (treatment 2) treated immediately after the contamination. The degradation of total TPH after 90 days ranged from 44 to 78%. However, the first 10 days were very important in terms of degradation and it slowed down significantly until 90 days. The degradation rate for light fractions in treatment 1 was slightly slower than treatment 2. On the other hand, for heavier fractions the degradation rate of heavier fractions in treatment 1 was at least twice as faster than treatment 2. Implicating that pre-treating the samples with biosolvent some days before the event of contamination may accelerate the degradation process of heavier fraction that are more difficult to degrade. The biosolvent used was degraded in a range from 55 to 100% showing that the biosolvent employed was biodegradable.

A comparison between three unmixing models for source apportionment of PM2.5 using alkanes in air from Southern Chile

ABSTRACT Fine particulate matter in the atmosphere, especially the fraction less than 2.5 µm in diameter (PM2.5), arises from several sources. Assessing the relative contributions from each source may be modeled through a mixing method, where the chemical signatures of known sources are mixed in a variety of proportions to provide the best explanation of the measured data. Alternatively, unmixing models determine what the chemical composition of the end members must have been in order to produce the observations. This study uses three different unmixing models with both a synthetic and a real-life (environmentally measured) alkane dataset from PM2.5 collected in five locations in Chile. Polytopic vector analysis (PVA), positive matrix factorization (PMF), and UNMIX modeling were used with ∼300 samples collected across 18 months. Using the synthetic data, both PVA and PMF were able to satisfactorily reconstruct the initial sources and their contribution to the samples, with PMF marginally more accurate than PVA. UNMIX was unable to complete this task with the synthetic data. With the real-life data, all three models produced numerical solutions that could be ascribed to sources that had similar chemical compositions and might represent diesel fuel, diesel particulate matter from combustion, and terrestrial matter, probably wood. Additionally, PVA and PMF produced a factor that could be ascribed to fuel oil used in domestic heating. Of the three models, PVA was the easiest to use; PMF was robust and readily available from the U.S. EPA but did require significantly more processing time, and UNMIX required considerable manipulation in order to produce solutions that might be related to chemical signatures and contributions.