Isoprene emission from tropical tree species

Foliar emission of isoprene was measured in nine commonly growing tree species of Delhi, India. Dynamic flow enclosure technique was used and gas samples were collected onto Tenax-GC/Carboseive cartridges, which were then attached to the sample injection system in the gas chromatograph (GC). Eluting compounds were analysed using a flame ionisation detector (FID). Out of the nine tree species, isoprene emission was found in six species (Eucalyptus sp., Ficus benghalensis, Ficus religiosa, Mangifera indica, Melia azedarach, and Syzygium jambolanum), whereas, in the remaining three tree species (Alstonia scholaris, Azadirachta indica, and Cassia fistula) no isoprene emission was detected or the levels of emission were negligible or below the detection limit (BDL). Among six tree species, the highest hourly emission (10.2 +/- 6.8 microg g(-1) leaf dry weight, average of five seasons) was observed in Ficus religiosa, while minimum emission was from Melia azedarach (2.2 +/- 4.9 microg g(-1) leaf dry weight, average of five seasons). Isoprene emission (average of six species), over five seasons, was found to vary between 3.9 and 8.5 microg g(-1) leaf dry weight during the rainy season. In addition, significant diurnal variation in isoprene emission was observed in each species. The preliminary estimate made in this study on the annual biogenic VOC emission from India may probably be the first of its kind from this part of the world.     

Seasonal patterns of non-terpenoid C6-C10 VOC emission from seven Mediterranean woody species

The seasonal pattern of non-terpenoid C6-C10 VOC emission by seven Mediterranean woody species (Bupleurum fruticosum, Cistus albidus, Pinus halepensis, Arbutus unedo, Erica arborea, Quercus coccifera, and Q. ilex) was studied under field conditions. Branch chamber samples were sorbed on carbotrap and analyzed by thermal desorption in combination with GC-MS. These non-terpenoid C6-C10 VOC emissions were large, almost of similar magnitude to those of terpenes. Overall, maximum values were recorded in spring and summer (up to 12 microg g(-1) DM h(-1) in Q. ilex) and minimum values in autumn and winter (up to 5 microg g(-1) DM h(-1) in Q. ilex). These C6-C10 VOC emissions represented 2.82% of the photosynthetic C fixation in summer and 0.22% in winter. Some compounds such as 2-ethoxyethyl acetate were emitted by most species, others such as 3-hexen-1-ol, phenol or decanal were significantly emitted only by few species. The greatest diversity of emitted non-terpenoid C6-C10 VOCs was observed in spring and in Q. ilex. Temperature seemed a strong driver of these seasonal changes but other species-specific and seasonal factors seem involved. These results indicate that C6-C10 non-terpenoid VOCs contribute a rather significant fraction of the total biogenic VOC flux from these Mediterranean species, especially in spring and summer, and therefore should be considered in VOC emission inventories and in model predictions of tropospheric chemistry.     

A study on dynamic volatile organic compound emission characterization of water-based paints

Volatile organic compounds (VOCs) emitted from surface coatings have caused growing public concern for air quality. Even the low-emitted VOC impact from water-based paints on indoor air quality in urban areas has caused concern. This paper presents experimental data using a mathematical model to simulate dynamic VOC emissions from water-based paints that is based on mass transfer and molecular diffusion theories. A series of field-analogous experiments were carried out to continuously measure the VOCs emitted from two typical water-based paints using a gas chromatography-flame-ionization detector monitor in an artificial wind tunnel system. In the study cases, the mass flux of VOCs emitted from the water-based paints was up to 50 microg/m2sec. It was found that the time needed to completely emit VOCs from water-based paints is just hundreds of seconds. However, the order of magnitude of the VOC emission rate from water-based paints is not lower than that from some dry building materials and solvent-based paints. The experimental data were used to produce a useful semiempirical correlation to estimate the VOC emission rates for water-based paints. This correlation is valid under appropriate conditions as suggested by this work with a statistical deviation of +/- 7.6%. With this correlation, it seems feasible to predict the dynamic emission rates for VOCs during a painting process. This correlation is applicable for assessing the hazardous air pollutant impact on indoor air quality or for environmental risk assessment. Associated with the dynamic VOC emission characterization, the air-exchange rate effect on the VOC emission rates is also discussed.     

Total and subcellular distribution of trace elements (Cd, Cu and Zn) in the liver and kidney of green turtles (Chelonia mydas) from the Mediterranean Sea

This study investigated the subcellular distribution of Cd, Cu and Zn in liver and kidney of green turtles (Chelonia mydas) stranded along the Italian coast of the South Adriatic Sea (Eastern Mediterranean). Cd and Zn mean concentrations did not differ significantly between liver (4.26microgg(-1) and 34.53microgg(-1), respectively) and kidney (5.06microgg(-1) and 26.39microgg(-1), respectively), whereas the levels of Cu were significantly higher in liver (32.75microgg(-1)) than in kidney (8.20microgg(-1)) (p<0.009). Most of Cd, Cu and Zn was present in hepatic and renal cytosol, and their concentrations increased with total levels in both organs, indicating that cytosol has a crucial role in metal accumulation. Cd and Cu in hepatic and renal cytosol were present mostly in metallothionein fractions (MTs), whereas Zn was fractionated into MTs and high-molecular-weight-substances (HMWS). The comparison with the results of other investigations on individuals of the same species collected in different marine areas shows good agreement relatively to essential metals. For Cd our data are comparable with those encountered in specimens from the Mediterranean Sea (Cyprus) confirming the homogeneity of the area comprising the south-eastern basin of the Mediterranean Sea from an ecological point of view.     

An Estimate of Biogenic Emissions of Volatile Organic Compounds during Summertime in China (7 pp)

Background and Aim An accurate estimation of biogenic emissions of VOC (volatile organic compounds) is necessary for better understanding a series of current environmental problems such as summertime smong and global climate change. However, very limited studies have been reported on such emissions in China. The aim of this paper is to present an estimate of biogenic VOC emissions during summertime in China, and discuss its uncertainties and potential areas for further investigations. Materials and Methods This study was mainly based on field data and related research available so far in China and abroad, including distributions of land use and vegetations, biomass densities and emission potentials. VOC were grouped into isoprene, monoterpenes and other VOC (OVOC). Emission potentials of forests were determined for 22 genera or species, and then assigned to 33 forest ecosystems. The NCEP/NCAR reanalysis database was used as standard environmental conditions. A typical summertime of July 1999 was chosen for detailed calculations. Results and Discussion The biogenic VOC emissions in China in July were estimated to be 2.3×10¹²gC, with 42% as isoprene, 19% as monoterpenes and 39% as OVOC. About 77.3% of the emissions are generated-from forests and woodlands. The averaged emission intensity was 4.11 mgC m⁻² hr⁻¹ for forests and 1.12 mgC m⁻² hr⁻¹ for all types of vegetations in China during the summertime. The uncertainty in the results arose from both the data and the assumptions used in the extrapolations. Generally, uncertainty in the field measurements is relatively small. A large part of the uncertainty mainly comes from the taxonomic method to assign emission potentials to unmeasured species, while the ARGR method serves to estimate leaf biomass and the emission algorithms to describe light and temperature dependence. Conclusions This study describes a picture of the biogenic VOC emissions during summertime in China. Due to the uneven spatial and temporal distributions, biogenic VOC emissions may play an important role in the tropospheric chemistry during summertime. Recommendations and Perspectives Further investigations are needed to reduce uncertainties involved in the related factors such as emission potentials, leaf biomass, species distribution as well as the mechanisms of the emission activities. Besides ground measurements, attention should also be placed on other techniques such as remotesensing and dynamic modeling. These new approaches, combined with ground measurements as basic database for calibration and evaluation, can hopefully provide more comprehensive information in the research of this field. Submission Editor: Prof. Dr. Gerhard Lammel (lammel@recetox.muni.cz)     

Emission characteristics of volatile organic compounds from semiconductor manufacturing

A huge amount of volatile organic compounds (VOCs) is produced and emitted with waste gases from semiconductor manufacturing processes, such as cleaning, etching, and developing. VOC emissions from semiconductor factories located at Science-Based Industrial Park, Hsin-chu, Taiwan, were measured and characterized in this study. A total of nine typical semiconductor fabricators (fabs) were monitored over a 12-month period (October 2000-September 2001). A flame ionization analyzer was employed to measure the VOC emission rate continuously in a real-time fashion. The amount of chemical use was adopted from the data that were reported to the Environmental Protection Bureau in Hsin-chu County as per the regulation of the Taiwan Environmental Protection Administration. The VOC emission factor, defined as the emission rate (kg/month) divided by the amount of chemical use (L/month), was determined to be 0.038 +/- 0.016 kg/L. A linear regression equation is proposed to fit the data with the correlation coefficient (R2)=0.863. The emission profiles of VOCs, which were drawn using the gas chromatograph/mass spectrometer analysis method, show that isopropyl alcohol is the dominant compound in most of the fabs.     

Near surface soil vapor clusters for monitoring emissions of volatile organic compounds from soils

The overall objective of this research was to develop and test a method of determining emission rates of volatile organic compounds (VOCs) and other gases from soil surfaces. Soil vapor clusters (SVCs) were designed as a low dead volume, robust sampling system to obtain vertically resolved profiles of soil gas contaminant concentrations in the near surface zone. The concentration profiles, when combined with a mathematical model of porous media mass transport, were used to calculate the contaminant flux from the soil surface. Initial experiments were conducted using a mesoscale soil remediation system under a range of experimental conditions. Helium was used as a tracer and trichloroethene was used as a model VOC. Flux estimations using the SVCs were within 25% of independent surface flux estimates and were comparable to measurements made using a surface isolation flux chamber (SIFC). In addition, method detection limits for the SVC were an order of magnitude lower than detection limits with the SIFC. Field trials, conducted with the SVCs at a bioventing site, indicated that the SVC method could be easily used in the field to estimate fugitive VOC emission rates. Major advantages of the SVC method were its low detection limits, lack of required auxiliary equipment, and ability to obtain real-time estimates of fugitive VOC emission rates.     

Determination of volatile organic profiles and photochemical potentials from chemical manufacture process vents

The main objective of this study was to monitor the volatile organic compounds (VOCs) in the stack gas released from organic chemical industrial plants to determine emission factors. Samples from 52 stacks, with or without air pollution control devices (APCDs), from seven industrial processes were taken and VOCs measured using U.S. Environmental Protection Agency (EPA) Method 18. These 7 processes, including 26 plants, were the manufacturers of acrylonitrile-butadiene-styrene (ABS), polyvinyl chloride (PVC), polystyrene (PS), acrylic resin (ACR), vinyl chloride (VC), para-terephthalic acid (PTA), and synthetic fiber (SYF). The results clearly indicate significant variations of emission factors among the various industrial processes, particularly emission factors for those without APCDs. As expected, those with APCDs yield much less emission factors. Regardless of those with or without APCDs, the order of manufacturing processes with regard to VOC emission factors is SYF > ABS > PS >ACR > PTA > PVC > VC. The emission factors for some processes also differ from those in EPA-42 data file. The VOC profiles further indicate that some VOCs are not listed in the U.S. VOC/Particulate Matter Speciation Data System (SPECIATE). The potential O3 formation is determined from the total amount of VOC emitted for each of seven processes. The resultant O3 yield varied from 0.22 (ACR) to 2.33 g O3 g(-1) VOC (PTA). The significance of this O3 yield is discussed.     

Photochemical smog modeling for assessment of potential impacts of different management strategies on air quality of the Bangkok Metropolitan Region, Thailand

A photochemical smog model system, the Variable-Grid Urban Airshed Model/Systems Applications International Mesoscale Model (UAM-V/SAIMM), was used to investigate photochemical pollution in the Bangkok Metropolitan Region (BMR). The model system was first applied to simulate a historical photochemical smog episode of two days (January 13-14, 1997) using the 1997 anthropogenic emission database available at the Pollution Control Department and an estimated biogenic emission. The output 1-hr ozone (O3) for BMR, however, did not meet the U.S. Environmental Protection Agency suggested performance criteria. The simulated minimum and maximum O3 values in the domain were much higher than the observations. Multiple model runs with different precursor emission reduction scenarios showed that the best model performance with the simulated 1-hr O3 meeting all the criteria was obtained when the volatile organic compound (VOC) and oxides of nitrogen (NOx) emission from mobile source reduced by 50% and carbon monoxide by 20% from the original database. Various combinations of anthropogenic and biogenic emissions in Bangkok and surrounding provinces were simulated to assess the contribution of different sources to O3 pollution in the city. O3 formation in Bangkok was found to be more VOC-sensitive than NOx-sensitive. To attain the Thailand ambient air quality standard for 1-hr O3 of 100 ppb, VOC emission in BMR should be reduced by 50-60%. Management strategies considered in the scenario study consist of Stage I, Stage II vapor control, replacement of two-stroke by four-stroke motorcycles, 100% compressed natural gas bus, 100% natural gas-fired power plants, and replacement of methyltertiarybutylether by ethanol as an additive for gasoline.     

Non-aromatic hydrocarbons in surface sediments near the Pearl River estuary in the South China Sea

Surface sediment samples at 4 sites along an offshore transect from outer continental shelf off the Pearl River estuary to the shelf slope region of the northern South China Sea, have been analyzed for total organic carbon (TOC), total nitrogen (TN), solvent extractable organic matter (EOM) and non-aromatic hydrocarbons. TOC, TN and EOM show distinct spatial variations. Their highest values are all recorded at the shelf slope region. EOM varies from 18.70-38.58 microgg(-1) dry sediment and accounts for 0.20-0.72% of the TOC contents. The non-aromatic hydrocarbons are an important fraction of EOM. Their contents range from 3.43-7.06 microgg(-1) dry sediment. n-Alkanes with carbon number ranging from 15-38 are identified. They derive from both biogenic and petrogenic sources in different proportions. Results of isoprenoid hydrocarbons, hopanes and steranes also suggest possible petroleum contamination.     

Wastewater analysis for volatile organic sulfides using purge-and-trap with gas chromatography/mass spectrometry.

This paper presented a modified method for the analysis of volatile organic sulfides (VOS) simultaneously with volatile organic compounds (VOC) in wastewater using purge-and-trap with gas chromatography/ mass spectrometry. Calibration standards were prepared using filtered and nitrogen-purged VOS-free wastewater, acidified to pH 1.4. Samples were also acidified to pH 1.4. This approach minimized the oxidation of methanethiol to dimethyl disulfide (DMDS), which hampered the liquid-phase analysis of VOS. Compounds were concentrated from the liquid phase, and automated analyses were performed without additional equipment, other than that required for routine wastewater VOC analysis. The linear range was 5 to 500 microg/L, with r2 > or = 0.99. The average recovery from replicate analyses of spiked samples was 81 +/- 0.5% for methanethiol, 100 +/- 1.5% fordimethyl sulfide (DMS), and 92 +/- 1.5% for DMDS. Method detection limits were 4.8, 2.8, and 1.2 microg/L for methanethiol, DMS, and DMDS, respectively. The relative percent differences were between 0 and 8%.     

Oxidative stress in duckweed (Lemna minor L.) caused by short-term cadmium exposure

The mechanisms of plant defence against cadmium toxicity have been studied by short-term exposure of Lemna minor L. (common duckweed) to concentrations of CdCl2 ranging from 0 to 500microM. High accumulation of cadmium was observed (12,320+/-2155microgg(-1) at 500microM CdCl2), which caused a gradual decrease of plant growth, increased lipid peroxidation, and weakened the entire antioxidative defence. Total glutathione concentration decreased significantly; however, the concentration of oxidized glutathione remained stable. The responses of four antioxidant enzymes showed that catalase was the most inhibited after CdCl2 exposure, ascorbate peroxidase and guaiacol peroxidase moderately, and glutathione reductase least. The total antioxidative potential revealed an induced antioxidative network at 0.1microM CdCl2 (137+/-13.2% of the control) and its reduction to only 47.4+/-4.0% of the control at higher cadmium concentrations. The possible application of the examined biomarkers in ecotoxicological research is discussed.     

The Role of Viscosity in Fabric Filtration

Abstract

An approach for measuring point-source emissions of volatile organic compounds (VOCs), acidic vapors, and other species is presented. The amount emitted is determined by directly measuring the actual weight gain of an adsorbent bed over a period of time, which is a cumulative rather than a grabbed sample. As a result, wide fluctuations of concentration and erratic flow behavior during sampling are accommodated with no apparent effect on the accuracy of the measured emission rate. The emission rate is determined by a mass balance including the mass change of the sorbent, as well as the influent and effluent humidities.

Validation tests used a known mass flow rate of vapor in a carrier gas, which was compared with the amount measured. The vapor was a single VOC, a mixture of VOCs, or a mixture of a VOC with water. Conditions studied were the compound or mixture of compounds, concentration, carrier gas, flow rate, and adsorbent. In some tests the VOC was admitted intermittently. The VOCs included n-hexane, acetone, toluene, vinyl acetate, and 1,1,1 trichloroethane. For 105 tests, the average absolute discrepancy of the delivered and measured emission rates was 6.8% and the standard deviation was 3.4%.     

Source profiles of volatile organic compounds associated with solvent use in Beijing,China

Compositions of volatile organic compound (VOC) emissions from painting applications and printing processes were sampled and measured by gas chromatography–mass spectrometry/flame ionization detection (GC–MS/FID) in Beijing. Toluene and C8 aromatics were the most abundant species, accounting for 76% of the total VOCs emitted from paint applications. The major species in printing emissions included heavier alkanes and aromatics, such as n-nonane, n-decane, n-undecane, toluene, and m/p-xylene. Measurements of VOCs obtained from furniture paint emissions in 2003 and 2007 suggest a quick decline in benzene levels associated with formulation changes in furniture paints during these years. A comparison of VOC source profiles for painting and printing between Beijing and other parts of the world showed significant region-specific discrepancies, probably because of different market demands and environmental standards. We conducted the evaluation of the source reactivities for various VOC emission sources. The ozone formation potential (OFP) for unit mass of VOCs source emissions is the highest for paint applications. Substituting solvent-based paints by water-based in Beijing will lead to an OFP reduction of 152,000 tons per year, which is more than 1/4 of the OFPs for VOCs emissions from vehicle exhaust in the city.     

On-line solid-phase extraction and fluorescence detection of selected endocrine disrupting chemicals in water by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed to analyse selected endocrine disrupting chemicals in water by using automated on-line solid-phase extraction with a fluorescence detector. The excitation and emission wavelengths of the fluorescence detector were 230 nm and 290 nm, respectively. The selected endocrine disrupting chemicals include hormone steroids such as estradiol (E2), estriol (E3), ethynylestradiol (EE2), and ethynylestradiol 3-methyl ether (MeEE2) as well as nonylphenols (NP), octylphenols (OP), POE(1-2) nonyl phenol (NPE) and bisphenol A (BP). Three types of on-line cartridges (C18, PLRP-s and PRP-1) were tested to pre-concentrate the endocrine disruptors in deionised water. It was found that the recoveries of these chemicals at 1 microg/L were close to 100% except for 4-octyl phenol and 4-n-nonyl phenol, which had recoveries of about 40% to 80%. The two polymer cartridges (PLRP-s and PRP-1) gave higher recoveries than the C18 cartridges. The addition of methanol at 5% to 10% in water significantly improved the recovery of 4-octyl phenol and 4-n-nonyl phenol. The addition of methanol also led to an improvement in the recovery with C18 cartridges. With the addition of methanol in water samples, these three types of cartridges gave similar recoveries for the chemicals. The detection limits of this method ranged from 20 ng/L to 50 ng/L. A river water sample spiked with these chemicals was analysed using the above method and we found no interference with the peaks of the selected endocrine disrupting chemicals. The recoveries for these chemicals were more than 92% except for 4-NP with a recovery of 61%. This relatively simple method is useful for laboratory studies on the environmental fate of these endocrine disrupting chemicals in water.     

A proton transfer reaction mass spectrometry based system for determining plant uptake of volatile organic compounds

In order to evaluate the contribution that higher plants make to the removal of volatile organic compounds from the atmosphere, a measurement system consisting of a proton transfer reaction mass spectrometer (PTR-MS), CO₂ analyzer, diffusion devise and leaf enclosure was established. The uptake of VOCs by Golden Pothos (Epipremnum aureum) was investigated. The overall relative error associated with measurements made using this system was <2.2% when a Golden Pothos leaf was exposed to 75–750 ppbv of methyl isobutyl ketone (MIBK). Even at the lowest MIBK concentration, more than 2.2% of the inflowing VOC was lost to the leaf, representing a detectable and positive MIBK uptake rate by the plant. The results of the investigation were compared with a measurement system based on gas chromatography analysis and it was shown that the use of a PTR-MS based system can significantly increase the certainties in determining the rate of VOC uptake by plants.     

Moving Bed Adsorption System for Control of VOCs from an Aircraft Painting Facility

An activated carbon moving bed system (10 to 100 acf m air flow) was tested for controlling VOC emissions from a commercial aircraft painting facility. The cross-flow moving adsorbent bed showed a VOC collection efficiency in the 77.1 to 99.6 percent range over a superficial gas velocity range of 27 to 185 ft/min (0.14-0.94 m/sec). The collection efficiencies were neither affected by a change in carbon flow rates from 5 to 8 Ib/hr (2.3 to 3.6 kg/hr) nor by a change in the gas superficial velocity from 27 to 185 ft/min. The VOC concentration in the emission stream from the painting hangar was found to vary by at least a factor of 20 (from 0.18 to 15 ppm) both over the five month period (during which the 15 system tests of about three hours each were conducted) and within a single eight hour work shift.     

Source location and characterization of volatile organic compound emissions at a petrochemical plant in Kaohsiung, Taiwan

This paper elucidated a novel approach to locating volatile organic compound (VOC) emission sources and characterizing their VOCs by database and contour plotting. The target of this survey was a petrochemical plant in Linyan, Kaohsiung County, Taiwan. Samples were taken with canisters from 25 sites inside this plant, twice per season, and analyzed by gas chromatography-mass spectrometry. The survey covered 1 whole year. By consolidated into a database, the data could be readily retrieved, statistically analyzed, and clearly presented in both table and graph forms. It followed from the cross-analysis of the database that the abundant types of VOCs were alkanes, alkenes/dienes, and aromatics, all of which accounted for 99% of total VOCs. By contour plotting, the emission sources for alkanes, aromatics, and alkenes/ dienes were successfully located. Through statistical analysis, the database could provide the range and 90% confidence interval of each species from each emission source. Both alkanes and alkene/dienes came from tank farm and naphtha cracking units and were mainly composed of C3-C5 members. Regarding aromatics, benzene, toluene, and xylenes were the primary species; they were emitted from tank farm, aromatic units, and xylene units.     

Total and inorganic arsenic in Antarctic macroalgae

The Antarctic region offers unparalleled possibilities of investigating the natural distribution of metals and metalloids, such as arsenic. Total and inorganic As were analysed in nine species of Antarctic macroalgae collected during the 2002 summer season in the Potter Cove area at Jubany-Dallmann Station (South Shetland Islands, Argentinian Base). Total As was determined by inductively coupled plasma-optical emission spectrometry after microwave-assisted acid digestion. Inorganic As was determined by acid digestion, solvent extraction, flow injection-hydride generation-atomic absorption spectrometry. Total As ranged from 5.8 microg g(-1) dry weight (dw) (Myriogramme sp.) to 152 microg g(-1)dw (Himantothallus grandifolius). Total As concentrations were higher in Phaeophytes (mean+/-SD: 71+/-44 microg g(-1)dw) than in Rhodophytes (mean+/-SD: 15+/-11 microg g(-1)dw). Inorganic As ranged from 0.12 microg g(-1) (Myriogramme sp.) to 0.84 microg g(-1)dw (Phaeurus antarcticus). The percentage of inorganic As with respect to total As was 0.7 for Phaeophytes, but almost 4 times higher for Rhodophytes (2.6). The work discusses possible causes for the presence of As in marine organisms in that pristine environment.     

Arsenic speciation in plants growing in arsenic-contaminated sites

Concentrations of total arsenic and of arsenic species were determined by ICPMS and HPLC-ICPMS in terrestrial plant samples. The arsenic concentration in plant samples from the contaminated sites ranged from 1.14 to 98.5 mg kg(-1) (dry mass). However, a very high value, exceeding largely this range was found in a moss sample growing in the contaminated area (1750 mg kg(-1)). Plants growing in a non-contaminated area with similar geological characteristics contained 0.06-0.58 mg As kg(-1). Plant samples from different species were selected and extracted with water, water/methanol (9+1, v/v), and water/methanol (1+1, v/v). Water/methanol (9+1, v/v) was selected as extractant for the speciation analysis for all the plant samples. The extraction efficiencies ranged from 3.0% to 41.4%, with good agreement between samples from the same plant species. Arsenite and/or arsenate were found in all the plant samples. Additionally, methylarsonate (MA), dimethylarsinate (DMA), trimethylarsine oxide (TMAO) and tetramethylarsonium ion (TETRA) were also identified in several plants, and in some cases MA and DMA were the main species found. TMAO, which is usually found as a trace constituent in organisms, was also a significant arsenical in one of the studied samples, where it constituted 24% of the extracted arsenic. In the present study, the patterns of arsenic species varied with the plant species and much higher proportion of organoarsenicals was found in plants from the more contaminated sites.