Μg Gdw Research Articles

Factors affecting monoterpene emission from Chamaecyparis obtusa

Monoterpenes are major compounds emitted by plants and contribute to the formation of photochemical oxidants and secondary organic aerosols in the troposphere. We measured monoterpene emissions from Chamaecyparis obtusa, a major coniferous tree species in Japan, in both the field and the laboratory. Short-term monoterpene emission from C. obtusa was typically dependent on temperature but barely dependent on light intensity. We calculated the basal emission rate Es assuming β = 0.09 in the G93 model. Three individual trees showed similar, but large seasonal variations in Es; e.g., 0.21‐ 5.42 µg gDW ‐1 h ‐1 for a tree showing the highest emission rate. The emission rate was much higher in winter and autumn. Although Es values averaged over 4 seasons indicated that C. obtusa is an intermediate emitter among coniferous trees, our results suggest that the large seasonal variation in Es should be considered in estimating annual monoterpene emission from this species. Furthermore, we found a significant effect of branch-to-branch touching by vibration on monoterpene emission from this species, suggesting that wind effect should be considered in the future for more precise emission estimation.

Comparison of periphytic biofilm and filter-feeding bivalve metal bioaccumulation (Cd and Zn) to monitor hydrosystem restoration after industrial remediation: a year of biomonitoring

Despite a significant decrease in the metallic waste emissions from an industrial site and a remediation process initiated in 2007, the Riou-Mort watershed (southwest France) still exhibits high Cd and Zn concentrations. Metal wastes have long been proven to significantly disturb aquatic communities. In this study, bioaccumulation capacities and responses to the chemical improvement of the hydrosystem were assessed for a year along the contamination gradient through the comparison of two biological models: Corbicula fluminea and periphytic biofilms, both considered as good bioindicators. Bioaccumulation results confirmed the persistence of water contamination in Corbicula fluminea and biofilms with, respectively, maximum Cd concentrations reaching 80.6 and 861.2 μg gDW(-1), and Zn concentrations 2.0 and 21.3 mg gDW(-1). Biofilms exhibited bioaccumulation in close correlation with water contamination, while Corbicula fluminea presented Cd bioaccumulation clearly regulated by water temperature and metal concentrations, affecting the ventilatory activity, as revealed by condition indices measurements. Also, a linear regression using Cd bioaccumulation and temperature () showed that below approximately 6 °C Corbicula fluminea did not appear to accumulate metals. Bioconcentration factors (BCFs) were higher in biofilms in comparison with Corbicula fluminea and showed the great accumulation capacity of suspended particulate matter in biofilms. However, bioaccumulation capacities are known to be influenced by many factors other than metal concentrations, such as temperature, water oxygenation or plankton and nutrient concentrations. Thus, this study demonstrates the power of a combined assessment using both Corbicula fluminea and biofilms as bioindicators to give a more integrated view of water quality assessment. Finally, when comparing our results with previous studies, the start of hydrosystem restoration could be shown by decreasing bioaccumulation in organisms.

Lead Concentrations in Zooplankton, Water, and Particulate Matter of a Southwestern Atlantic Temperate Estuary (Argentina)

This study presents for the first time valuable results of lead (Pb) accumulation in zooplankton from a southwestern Atlantic temperate estuary, the Bahía Blanca estuary, one of the most important and industrialized coastal environments of Argentina. It considers Pb concentrations in zooplankton organisms as well as in the dissolved and particulate phases. These fractions were analyzed on account of their important role in the biogeochemical cycles of trace elements in estuarine environments. In addition, the major physicochemical variables, i.e., nutrients, and pigment concentrations, and zooplankton composition and abundance, were also considered to understand Pb levels in the above-mentioned fractions. Samplings were performed from March to December 2005 with a bimonthly frequency and comprised a study area with stations located near industrial settlements and other stations a few kilometers far from these points. The results of the physicochemical variables and nutrients and pigments agreed with historic values for the estuary and did not present any evidence of abnormalities. Dissolved Pb presented a mean concentration of 2.15±0.46μgL(-1), whereas particulate Pb presented a mean concentration of 13.52±3.07μgg(-1) dry weight (dw). In the mesozooplankton, represented by copepods, the mean concentration was similar to the particulate fraction (13.38±4.41μgg(-1) dw), whereas in the macrozooplankton, represented by mysids, it was lower (9.81±1.89μgg(-1) dw). Thus, Pb concentrations were relatively high in the dissolved and particulate phases. Moreover, zooplankton accumulated important concentrations of this metal, which was mainly incorporated through suspended particulate matter (SPM). The source of Pb in all of these fractions is related to the industry discharges as well domestic sewage located near the sampling stations. Finally, through these results, it was possible to show the importance of zooplankton and SPM in the biogeochemical cycle of Pb as well as the interaction between these fractions in an estuarine and anthropogenic environment, such as the Bahía Blanca estuary.

The Extent of Arsenic and of Metal Uptake by Aboveground Tissues of Pteris vittata and Cyperus involucratus Growing in Copper- and Cobalt-Rich Tailings of the Zambian Copperbelt

The extent of arsenic (As) and metal accumulation in fronds of the As hyperaccumulator Pteris vittata (Chinese brake fern) and in leaves of Cyperus involucratus, which grow on the surface of an old flotation tailings pond in the Zambian Copperbelt province, was studied. The tailings consist of two types of material with distinct chemical composition: (1) reddish-brown tailings rich in As, iron (Fe), and other metals, and (2) grey-green tailings with a lower content of As, Fe, and other metals, apart from manganese (Mn). P. vittata accumulates from 2350 to 5018μgg(-1) As (total dry weight [dw]) in its fronds regardless of different total and plant-available As concentrations in both types of tailings. Concentrations of As in C. involucratus leaves are much lower (0.24-30.3μgg(-1) dw). Contents of copper (Cu) and cobalt (Co) in fronds of P. vittata (151-237 and 18-38μgg(-1) dw, respectively) and in leaves of C. involucratus (96-151 and 9-14μgg(-1) dw, respectively) are high, whereas concentrations of other metals (Fe, Mn, and zinc [Zn]) are low and comparable with contents of the given metals in common plants. Despite great differences in metal concentrations in the two types of deposited materials, concentrations of most metals in plant tissues are very similar. This indicates an exclusion or avoidance mechanism operating when concentrations of the metals in substrate are particularly high. The results of the investigation show that Chinese brake fern is not only a hyperaccumulator of As but has adapted itself to high concentrations of Cu and Co in flotation tailings of the Zambian Copperbelt.

Sulfide Inhibition of Nitrate Removal in Coastal Sediments

Microbial nitrate (NO3−) removal via denitrification (DNF) at high sulfide (H2S) concentrations was compared in sediment from a coastal freshwater pond in a developed area that receives salt-water influx during storm events, and a saline pond proximal to an undeveloped estuary. Sediments were incubated with added SO42− (1,000 µg per gram dry weight basis (gdw)) to determine whether acid volatile sulfides (AVS) were formed. DNF in the sediments was measured with NO3–N (300 µg gdw−1) alone, and with NO3–N and H2S (1,000 µg S2− gdw−1). SO42− addition to the freshwater sediments resulted in AVS formation (970 ± 307 µg S gdw−1) similar to the wetland with no added SO42− (986 ± 156 µg S gdw−1). DNF rates measured with no added H2S were greater in the freshwater than the wetland site (10.6 ± 0.6 vs. 6.4 ± 0.1 µg N2O–N gdw−1 h−1, respectively). High H2S concentrations retained NH4–N in the undeveloped wetland and retained NO3–N in the developed freshwater site, suggesting that potential salt-water influx may reduce the ability of the freshwater sediments to remove NO3–N.

Oceanic loading of wildfire‐derived organic compounds from a small mountainous river

Small mountainous rivers (SMRs) export substantial amounts of sediment into the world's oceans. The concomitant yield of organic carbon (OC) associated with this class of rivers has also been shown to be significant and compositionally unique. We report here excessively high loadings of polycyclic aromatic hydrocarbons (PAHs), lignin, and levoglucosan, discharged from the Santa Clara River into the Santa Barbara Channel. The abundance of PAHs, levoglucosan, and lignin in Santa Barbara Channel sediments ranged from 201.7 to 1232.3 ng gdw−1, 1.3 to 6.9 μg gdw−1, and 0.3 to 2.2 mg per 100 mg of the sedimentary OC, respectively. Assuming a constant rate of sediment accumulation, the annual fluxes of PAHs, levoglucosan, and lignin, to the Santa Barbara Channel were respectively, 885.5 ± 170.2 ng cm−2 a−1, 3.5 ± 1.9 μg cm−2 a−1 and 1.4 ± 0.3 mg per 100 mg OC cm−2 a−1, over ∼30 years. The close agreement between PAHs, levoglucosan, and lignin abundance suggests that the depositional flux of these compounds is largely biomass combustion‐derived. To that end, use of the Santa Clara River as a model for SMRs suggests this class of rivers may be one of the largest contributors of pyrolyzed carbon to coastal systems and the open ocean. Wildfire associated carbon discharged from other high yield fluvial systems, when considered collectively, may be a significant source of lignin, pyrolytic PAHs, and other pyrogenic compounds to the ocean. Extrapolating these methods over geologic time may offer useful historical information about carbon sequestration and burial in coastal sediments and affect coastal carbon budgets.

Microcystin accumulation in liver and muscle of tilapia in two large Brazilian hydroelectric reservoirs

The objective of this study was to measure levels of the toxin microcystin in different tissues of fish known to feed on cyanobacteria during toxic bloom events. Wild Nile and redbreast tilapia ( Oreochromis niloticus and Tilapia rendalli) were sampled from the catch of artisanal fishermen at eutrophic stations of Funil and Furnas reservoirs in southeastern Brazil. Phytoplankton communities in the two reservoirs were quite different taxonomically, but not dissimilar in microcystin content (200 μg g dry weight (DW) seston −1 at Funil, 800 μg gDW seston −1 at Furnas). All of the 27 fish sampled contained microcystin, ranging from 0.8 to 32.1 μg g liver −1 and from 0.9 to 12.0 ng g muscle −1. Most microcystin variants found in seston were also found in fish liver . T. rendalli had the lowest concentration in both tissues when compared to O. niloticus. In both reservoirs, one of every four fish sampled, always O. niloticus, had a level of microcystins beyond the World Health Organization tolerable daily intake (8 ng g tissue −1) and represented a risk for consumers. It is possible that closer study of inter-species variability in toxin burden in cyanobacteria-impacted water bodies will permit the development of guidelines for fish consumption that will better protect public health.

Monoterpene emissions from rubber trees (Hevea brasiliensis) in a changing landscape and climate: chemical speciation and environmental control

AbstractEmissions of biogenic volatile organic compounds (VOCs) have important roles in ecophysiology and atmospheric chemistry at a wide range of spatial and temporal scales. Tropical regions are a major global source of VOC emissions and magnitude and chemical speciation of VOC emissions are highly plant‐species specific. Therefore it is important to study emissions from dominant species in tropical regions undergoing large‐scale land‐use change, for example, rubber plantations in South East Asia. Rubber trees (Hevea brasiliensis) are strong emitters of light‐dependent monoterpenes. Measurements of emissions from leaves were made in the dry season in February 2003 and at the beginning of the wet season in May 2005. Major emitted compounds were sabinene, α‐pinene and β‐pinene, but β‐ocimene and linalool also contributed significantly at low temperature and light. Cis‐ocimene was emitted with a circadian course independent of photosynthetic active radiation (PAR) and temperature changes with a maximum in the middle of the day. Total isoprenoid VOC emission potential at the beginning of the wet season (94 μg gdw−1 h−1) was almost two orders of magnitude higher than measured in the dry season (2 μg g dw−1 h−1). Composition of total emissions changed with increasing temperature or PAR ramps imposed throughout a day. As well as light and temperature, there was evidence that assimilation rate was also a factor contributing to seasonal regulating emission potential of monoterpenes from rubber trees. Results presented here contribute to a better understanding of an important source of biogenic VOC associated with land‐use change in tropical South East Asia.

Hydrocarbon fluxes above a Scots pine forest canopy: measurements and modeling

Abstract. We measured the fluxes of several hydrocarbon species above a Scots pine (Pinus sylvestris) stand using disjunct eddy covariance technique with proton transfer reaction – mass spectrometry. The measurements were conducted during four days in July at SMEAR II research station in Hyytiälä, Finland. Compounds which showed significant emission fluxes were methanol, acetaldehyde, acetone, and monoterpenes. A stochastic Lagrangian transport model with simple chemical degradation was applied to assess the sensitivity of the above canopy fluxes to chemistry. According to the model, the chemical degradation had a minor effect on the fluxes measured in this study but may have a major effect on the vertical flux profiles of more reactive compounds, such as sesquiterpenes. The monoterpene fluxes derived using M81 and M137 had a systematic difference with the latter one being higher. These fluxes followed the traditional exponential temperature dependent emission algorithm but were considerably higher than the fluxes measured before at the same site. The normalized monoterpene emission potentials at 30°C, obtained using the temperature dependence coefficient of 0.09°C−1, were 2.0 μg gdw−1 h−1 and 2.5 μg gdw−1 h−1, for fluxes derived using M81 and M137.

Diurnal and seasonal emissions of volatile organic compounds from cork oak () trees

Abstract The emissions of volatile organic compounds from Quercus suber (cork oak) were investigated at two rural sites in Portugal using a branch enclosure method with subsequent analysis by gas chromatography/flame ionization detection. Q. suber leaves released important amounts of monoterpenes, mainly in the form of limonene, α-pinene, β-pinene and sabinene. However, significant temporal and intraspecific variations in the relative abundance of the dominant compounds were found during this survey. Emissions from Q. suber were strongly dependent on light and temperature, showing a similar behaviour to that of plant species known to be isoprene producers. But, this work also revealed that, although at lower rates, emissions of monoterpenes continued in the dark for several hours. Emission rates were quite well predicted by algorithms based on the Guenther and Tingey equations; correlations of measurements with modelled data were, on average, r 2 = 0.80 . A pronounced seasonal variation was recorded for the emissions of monoterpenes. During the 1-yr study period, standard emission rates ranged between a minimum of 0.2 μg gdw−1 h−1, in winter, and a maximum of 20–30 μg gdw−1 h−1, in summer.

Field monoterpene emission of Mediterranean oak (Quercus ilex) in the central Iberian Peninsula measured by enclosure and micrometeorological techniques: Observation of drought stress effect

An experimental characterization of biogenic emission from Quercus ilex ssp. rotundifolia in a forest near Madrid, Spain, was carried out in the early autumn of the years 2000–2003. A dynamic branch enclosure technique was implemented to determine the monoterpene emission rates of this evergreen oak species during the 2000 and 2001 campaigns. Major compounds emitted during both measurement periods were limonene, α‐pinene, β‐pinene, sabinene, and myrcene. In the 2000 field campaign the light‐ and temperature‐dependent model of Guenther et al. [1993] did not fit the data due to drastic reductions of emission rates (and leaf gas exchange related parameters) observed at high air temperature and low air humidity (high water vapor pressure deficit). This plant physiological activity depletion and the subsequent emission reduction were attributed to severe water soil deficit conditions, as precipitation was very scarce during the growing season. In contrast, during the 2001 field campaign, neither emission nor physiological activity showed strong decreases in hot days. A good fit of experimental data to Guenther model was achieved in this field campaign (r2 = 0.90), and linear regression gave a standard emission factor (ES) of 14.0 μg gdw−1 h−1 (gdw is grams dry weight). Soil moisture was presumably higher than during the 2000 campaign due to recent rain events. With the purpose of documenting the drought stress effect at canopy level, monoterpene oak fluxes were measured by the modified Bowen ratio micrometeorological technique throughout the 2001 field campaign and in the late summer of 2002 and 2003. The measured emission by both techniques showed a reasonably good correlation, although micrometeorological fluxes were, in general, lower than upscaled branch emission rates. According to Guenther's parameterization, standard emission fluxes (FS) of 0.30 μg m−2 s−1 (r2 = 0.61) and 0.28 μg m−2 s−1 (r2 = 0.67) were derived for the 2001 and 2002 field campaigns, respectively. However, measured fluxes in September 2003 at high ambient temperature were much lower than those of the previous years. Moreover, from the CLCT range in which emission in this field campaign could be fitted to a linear behavior, the FS value obtained was 50% lower than the 2001 and 2002 values. Water xylem potential measurements indicated the existence of drought conditions during the 2003 campaign and unstressed water conditions during the 2002 campaign.

Relating spatial and temporal variability in sediment chlorophylla and carbohydrate distribution with erodibility of a tidal flat

Trends in the spatial distribution of chlorophylla (chla) and colloidal and total carbohydrates on the Molenplaat tidal flat in the Westerschelde estuary, Netherlands, reflected spatial differences in physical properties of the sediment. Results from a Spearman Rank Order Correlation indicated that many of the physical and biological measures covaried. Multiple regression analyses describing the relationship between colloidal carbohydrates and sediment properties resulted in several highly significant equations, although in all cases chla was able to predict colloidal carbohydrate content. Relationships between sediment surface chla and colloidal carbohydrate, and sediment erodibility (i.e., critical erosion threshold, Ucrit, and mass of sediment eroded at a velocity of 30 cm s−1) determined in annular flume experiments were examined. Overall sediment erodibility was lowest (i.e., high thresholds, low mass eroded) for the siltiest sediments in June 1996 when chla and colloidal carbohydrates were high (56.9 μg gDW−1 and 320.6 μg gluc.equ. gDW−1, respectively), and greatest (i.e., low thresholds, high mass eroded) at the sandier sediments in September 1996, when chla and colloidal carbohydrates were low (1.0 μg gDW−1 and 5.7 μg gluc.equ. gDW−1, respectively). When sediments were grouped according to relative silt content, the most significant relationships were found in muddy sand with a finegrained fraction (<63 μm) of 25–50%. Thresholds of erosion increased, while mass of sediment eroded decreased, with increasing chla and colloidal carbohydrate. A similar trend was observed for the sand-muddy sand (63 μm 10–25%). In the sand (63 μm 0–10%), there were no relationships for Ucrit, whereas mass eroded appeared to increase with increasing chla and colloidal carbohydrate. The increased carbohydrate may stick sand grains together, altering the nature of erosion from rolling grains to clumps of resuspension.

Eddy covariance measurements of oxygenated volatile organic compound fluxes from crop harvesting using a redesigned proton‐transfer‐reaction mass spectrometer

A redesigned proton‐transfer‐reaction mass spectrometer was deployed in the field to measure atmospheric fluxes of volatile organic compounds (VOCs) released following the cutting and drying of hay. The instrument has a fast response, around 0.1 s, allowing use of the eddy covariance technique. Measurements were done over a 3‐day period in a hay field in the eastern part of Tirol, Austria, in the early growing season and are compared to earlier results obtained using a slower‐response instrument in the late growing season [Karl et al., 2000]. Peak upward fluxes of the order of 9.9 × 10−6g m−2 s−1 for methanol, 1.5 × 10−6g m−2 s−1 for acetaldehyde, and 1.5 × 10−6g m−2 s−1 for the sum of hexenals, hexenols, hexanal, pentenols, 3‐methylbutanal, and butanone were observed during and after harvesting. Time‐integrated values for the first day were of the order of 65±20 mg m−2 (130±40 μg per gram dry weight(gdw)−1) for methanol and 13±4 mg m−2 (26±8 μg gdw−1) for acetaldehyde. VOC fluxes measured in this study were generally higher than in August 1999, which can be explained by higher temperatures and higher photosynthetic productivity. Good agreement with another means for estimating VOC fluxes, the surface gradient method, was achieved. This paper presents measurements of eddy covariance for a wide variety of oxygenated VOCs and shows that hay harvesting can influence the local air quality in many regions in the Alps on a short‐term basis.