Stable carbon isotope ratio in atmospheric CO2 collected by new diffusive devices

In this paper, stable carbon isotope ratios (δ ¹³C) were determined in the atmosphere by using a Ca-based sorbent, CaO/Ca₁₂Al₁₄O₃₃ 75:25 w/w, for passively collecting atmospheric CO₂, in both field and laboratory experiments. Field measurements were conducted in three environments characterized by different carbon dioxide sources. In particular, the environments under consideration were a rather heavily trafficked road, where the source of CO₂ is mostly vehicle exhaust, a rural unpolluted area, and a private kitchen where the major source of CO₂ was gas combustion. Samplers were exposed to the free atmosphere for 3 days in order to allow collection of sufficient CO₂ for δ¹³C analysis, then the collected CO₂ was desorbed from the adsorbent with acid treatment, and directly analyzed by nondispersive infrared (NDIR) instrument. δ ¹³C results confirmed that the samplers collected representative CO₂ samples and no fractionation occurred during passive trapping, as also confirmed by an appositely designed experiment conducted in the laboratory. Passive sampling using CaO/Ca₁₂Al₁₄O₃₃ 75:25 w/w proved to be an easy and reliable method to collect atmospheric carbon dioxide for δ ¹³C analysis in both indoor and outdoor places.     

Carbon isotope signature of dissolved inorganic carbon (DIC) in precipitation and atmospheric CO2

This paper describes results of chemical and isotopic analysis of inorganic carbon species in the atmosphere and precipitation for the calendar year 2008 in Wroc?aw (SW Poland). Atmospheric air samples (collected weekly) and rainwater samples (collected after rain episodes) were analysed for CO₂ and dissolved inorganic carbon (DIC) concentrations and for δ¹³C composition. The values obtained varied in the ranges: atmospheric CO₂: 337-448 ppm; δ¹³C_CO2 from −14.4 to −8.4‰; DIC in precipitation: 0.6-5.5 mg dm⁻³; δ¹³C_DIC from −22.2 to +0.2‰. No statistical correlation was observed between the concentration and δ¹³C value of atmospheric CO₂ and DIC in precipitation. These observations contradict the commonly held assumption that atmospheric CO₂ controls the DIC in precipitation. We infer that DIC is generated in ambient air temperatures, but from other sources than the measured atmospheric CO₂. The calculated isotopic composition of a hypothetical CO₂ source for DIC forming ranges from −31.4 to −11.0‰, showing significant seasonal variations accordingly to changing anthropogenic impact and atmospheric mixing processes.     

Decadal changes in atmospheric CO2 concentration and δ13C over two seas and two oceans: Italy to New Zealand

Continuous measurements of the CO₂ concentration were repeatedly carried out from 1996 to 2007 between Italy and New Zealand by means of a Siemens Ultramat 5E analyzer assembled for shipboard use. Along the ship routes discrete air samples were collected from 1998 to 2005 using four-litre Pyrex flasks. The δ¹³C of the CO₂ from the flask air samples was measured according to well-established techniques. The decadal changes of these two variables can now be evaluated from these results. Large variations of the CO₂ concentration were normally recorded in the Mediterranean and the Red Sea. Completely different trends of the CO₂ concentration were observed in the Red Sea (30° N to about 13° N) between 2007 (a marked southward decrease) and 2005 and 2003 when a marked southward increase is apparent, at least between 23° and 13° N. A further difference among different expeditions is related to the decrease or increase of the CO₂ concentration in the Gulf of Aden. The backward trajectories of the air masses help to explain, at least partially, these differences. In the Indian Ocean and Southern Ocean a decrease of a few ppmv of the CO₂ concentration takes place from Cape Guardafui (Northern Somaliland) to southern New Zealand, particularly during 2005 and 2007. The yearly rate of increase of the CO₂ concentration between 1996 and 2007 for the Indian Ocean is of about 1.9 ppmv yr^?1, in excellent agreement with the NOAA/CMDL measurements carried out during the same period at Mahé Isld. (Indian Ocean) and Cape Grim (Tasmania). The δ¹³C results obtained from the CO₂ of flask samples collected in the Mediterranean show the effect of anthropogenic emissions, though this is considerably smaller than expected. This inconsistency may be related to the large terrestrial biospheric sink of CO₂ in the Northern Hemisphere. The results obtained from the Red Sea are quite variable through time and space, particularly in its southern section; their interpretation is not easy. The Indian Ocean and the Southern Ocean show rather homogeneous δ¹³C results even though a variable carbon isotope shift can be calculated from period/cruise to period/cruise. In the case of the Indian Ocean the mean δ¹³C value from the flask air samples collected in 2005 is ?8.29‰ and the calculated rate of the carbon isotope shift between 1998 and 2005 is ?0.034‰ yr^?1, considerably larger than that calculated at the closest NOAA station (Mahé Isld.) of ?0.026‰ yr^?1. This discrepancy may be, at least partially, caused by the small number of measurements carried out at sea. However, the atmosphere over the Indian Ocean is less affected by anthropogenic emissions than in other areas.     

Using variances in hydrocarbon concentration and carbon stable isotope to determine the important influence of irrigated water on petroleum accumulation in surface soil

Hunpu is a wastewater-irrigated area southwest of Shenyang. To evaluate petroleum contamination and identify its sources at the area, the aliphatic hydrocarbons and compound-specific carbon stable isotopes of n-alkanes in the soil, irrigation water, and atmospheric deposition were analyzed. The analyses of hydrocarbon concentrations and geochemical characteristics reveal that the water is moderately contaminated by degraded heavy oil. According to the isotope analysis, inputs of modern C3 plants and degraded petroleum are present in the water, air, and soil. The similarities and dissimilarities among the water, air, and soil samples were determined by concentration, isotope, and multivariate statistical analyses. Hydrocarbons from various sources, as well as the water/atmospheric deposition samples, are more effectively differentiated through principal component analysis of carbon stable isotope ratios (δ¹³C) relative to hydrocarbon concentrations. Redundancy analysis indicates that 57.1 % of the variance in the δ¹³C of the soil can be explained by the δ¹³C of both the water and air, and 35.5 % of the variance in the hydrocarbon concentrations of the soil can be explained by hydrocarbon concentrations of both the water and the air. The δ¹³C in the atmospheric deposition accounts for 28.2 % of the δ¹³C variance in the soil, which is considerably higher than the variance in hydrocarbon concentrations of the soil explained by hydrocarbon concentrations of the atmospheric deposition (7.7 %). In contrast to δ¹³C analysis, the analysis of hydrocarbon concentrations underestimates the effect of petroleum contamination in the irrigated water and air on the surface soil. Overall, the irrigated water exerts a larger effect on the surface soil than does the atmospheric deposition.     

Degradation of telone II in contaminated and noncontaminated soils

Abstract

Degradation of the nematicide Telone II (cis‐ and trans‐1,3‐dichloropropene comprise the active ingredients) in soil was studied using ¹⁴C‐l,3‐dichloropropene (DCP) along with soil samples collected from a field test site near Quincy, Florida. A mixed bacterial culture isolated from the soil in the presence of a second carbon source, glucose or yeast extract, completely degraded ¹⁴C‐DCP to ¹⁴CO₂, water‐soluble products, and microbial mass. ¹⁴C‐DCP in soil was also degraded to ¹⁴CO₂. After 28 days of incubation, the labeled chemical was completely degraded to ¹⁴CO₂, water‐soluble metabolites, bound‐residues, and possibly some microbial mass. Little or no difference was observed in the degradation of ¹⁴C‐DCP in soil samples collected one week prior to field application of Telone II, or two weeks and two years after application.     

Below-ground carbon allocation in mature beech and spruce trees following long-term, experimentally enhanced O3 exposure in Southern Germany

Canopies of adult European beech (Fagus sylvatica) and Norway spruce (Picea abies) were labeled with CO₂ depleted in ¹³C to evaluate carbon allocation belowground. One-half the trees were exposed to elevated O₃ for 6 yrs prior to and during the experiment. Soil-gas sampling wells were placed at 8 and 15 cm and soil CO₂ was sampled during labeling in mid-late August, 2006. In beech, δ¹³CO₂ at both depths decreased approximately 50 h after labeling, reflecting rapid translocation of fixed C to roots and release through respiration. In spruce, label was detected in fine-root tissue, but there was no evidence of label in δ¹³CO₂. The results show that C fixed in the canopy rapidly reaches respiratory pools in beech roots, and suggest that spruce may allocate very little of recently-fixed carbon into root respiration during late summer. A change in carbon allocation belowground due to long-term O₃ exposure was not observed.     

Quantification of airborne fossil and biomass carbonylic carbon by combined radiocarbon and liquid chromatography mass spectrometry

Airborne carbonyl compounds have been sampled at three European semi-remote to semi-urban test sites for radiocarbon (¹⁴C) analysis. The used methodology included collection on 2,4-dinitrophenylhydrazine coated silica gel cartridges, chromatographic isolation of the formed hydrazones, combustion into CO₂, reduction into graphite followed by accelerator mass spectrometry. In combination with this, liquid chromatography coupled to atmospheric pressure chemical ionisation mass spectrometry was used for chemical speciation of the collected carbonyls.At all sites the carbonyls were found to be of a mixed biogenic/anthropogenic origin. The determining factor for the proportion of fossil (anthropogenic) carbon in the samples was the vicinity of urban sources for carbonyls and their photochemical precursors. At meteorological conditions, which gave the test sites semi-rural/semi-remote characteristics the samples contained an average of 24% (range: 10–34%) of fossil carbonylic carbon. When air masses were transported from urban areas to the test-sites significantly higher proportions of fossil carbonylic carbon were determined with a maximum of 61%. Principal component analysis on this limited data set indicated that a low fossil proportion of carbonylic carbon is associated with high proportions of acetaldehyde, acetone, pentanone and acrolein. Until further radicarbon studies are carried out the conclusion remains that for the carbonyl compounds measured European background levels are of a predominant biogenic origin.     

δ13C variations in tree rings as an indication of severe changes in the urban air quality

Annual growth rings sampled from three free-standing trees (Platanus hybrida sp.), grew in the metropolitan area of Palermo (Italy) and covering a 118 years time span (1880–1998), have been studied for their ¹³C/¹²C carbon isotope ratios. It has been found that the ¹³C/¹²C tree ring record, during the study time interval, decreased of −3.6‰, from −26.4‰ in 1880 to −30‰ in 1998. Such a progressive depletion has been attributed to the addition of anthropogenic ¹³C depleted carbon dioxide to the local atmosphere. The observed ¹³C/¹²C decrease has been used to infer some possible pathways of atmospheric CO₂ change in the study urban area.     

Organic and inorganic components of aerosols over the central Himalayas: winter and summer variations in stable carbon and nitrogen isotopic composition

The aerosol samples were collected from a high elevation mountain site, Nainital, in India (1958 m asl) during September 2006 to June 2007 and were analyzed for water-soluble inorganic species, total carbon, nitrogen, and their isotopic composition (δ¹³C and δ¹⁵N, respectively). The chemical and isotopic composition of aerosols revealed significant anthropogenic influence over this remote free-troposphere site. The amount of total carbon and nitrogen and their isotopic composition suggest a considerable contribution of biomass burning to the aerosols during winter. On the other hand, fossil fuel combustion sources are found to be dominant during summer. The carbon aerosol in winter is characterized by greater isotope ratios (av. ?24.0?‰), mostly originated from biomass burning of C₄ plants. On the contrary, the aerosols in summer showed smaller δ¹³C values (?26.0?‰), indicating that they are originated from vascular plants (mostly of C₃ plants). The secondary ions (i.e., SO₄ ^2?, NH₄ ⁺, and NO₃ ^?) were abundant due to the atmospheric reactions during long-range transport in both seasons. The water-soluble organic and inorganic compositions revealed that they are aged in winter but comparatively fresh in summer. This study validates that the pollutants generated from far distant sources could reach high altitudes over the Himalayan region under favorable meteorological conditions.     

δC variations in tree rings as an indication of severe changes in the urban air quality

Annual growth rings sampled from three free-standing trees (Platanus hybrida sp.), grew in the metropolitan area of Palermo (Italy) and covering a 118 years time span (1880–1998), have been studied for their ¹³C/¹²C carbon isotope ratios. It has been found that the ¹³C/¹²C tree ring record, during the study time interval, decreased of −3.6‰, from −26.4‰ in 1880 to −30‰ in 1998. Such a progressive depletion has been attributed to the addition of anthropogenic ¹³C depleted carbon dioxide to the local atmosphere. The observed ¹³C/¹²C decrease has been used to infer some possible pathways of atmospheric CO₂ change in the study urban area.     

Microbial metabolism of N-Phenyl-1-naphthylamine in soil, soil suspensions, and aquatic ecosystems

N-Phenyl-1-naphthylamine (PNA) was degraded and mineralized in nonsterile aquatic and terrestrial samples. Degradation in unsupplemented sewage and lake water was detected in 3 to 6 days with half-lives of 5 and 10 days, respectively. In sewage and lake water supplemented with a readily degradable carbon source, degradation began in 1 and 5 days with half-lives of 2 and 8 days, respectively. Sewage samples converted between 20 and 30% of labeled [¹⁴C]-PNA to ¹⁴CO₂ in 35 days while lake water samples reached 10% conversion to ¹⁴CO₂ in 12 days. Soil samples and soil suspensions converted from 15 to 35% of [¹⁴C]-PnA to ¹⁴CO₂ in 11 days. PNA was microbiologically converted in lake water to two products that were tentatively identified by gas-liquid chromatography and mass spectroscopy as dihydroxy and N-acetyl derivatives.     

Biomineralization rates of 14C-labelled organic chemicals in aerobic and anaerobic suspended soil

The formation of ¹⁴CO₂ from 13 ¹⁴C-labelled organic chemicals in aerobic and anaerobic suspended soil was determined. After 5 days at 35°C, ¹⁴CO₂ was between 70.1% (urea, anaerobic) and < 0.1% (2,6-dichlorobenzonitrile and hexachlorobenzene, aerobic and anaerobic) of the ¹⁴C initially applied.     

Response of stable carbon isotope in epilithic mosses to atmospheric nitrogen deposition

Epilithic mosses are characterized by insulation from substratum N and hence meet their N demand only by deposited N. This study investigated tissue C, total Chl and δ¹³C of epilithic mosses along 2 transects across Guiyang urban (SW China), aiming at testing their responses to N deposition. Tissue C and total Chl decreased from the urban to rural, but δ¹³C_moss became less negative. With measurements of atmospheric CO₂ and δ¹³CO₂, elevated N deposition was inferred as a primary factor for changes in moss C and isotopic signatures. Correlations between total Chl, tissue C and N signals indicated a nutritional effect on C fixation of epilithic mosses, but the response of δ¹³C_moss to N deposition could not be clearly differentiated from effects of other factors. Collective evidences suggest that C signals of epilithic mosses are useful proxies for N deposition but further works on physiological mechanisms are still needed.     

Oxygen and carbon isotopic signatures reveal a long-term effect of free-air ozone enrichment on leaf conductance in semi-natural grassland

The effect of ozone on leaf gas diffusion was investigated by analyzing the stable oxygen isotopic signatures (δ¹⁸O) in leaves of Holcus lanatus L., Plantago lanceolata L., Ranunculus friesianus (Jord.), and Trifolium pratense L. grown in temperate, semi-natural grassland. Dried material from plants exposed to ambient or elevated ozone levels in a long-term free-air experiment was sampled in 2002 and 2003. A general increase in δ¹⁸O in elevated ozone indicated increased limitation to gas diffusion, which was strongest during the driest and warmest period in 2003. In three out of four species, the increase in δ¹⁸O paralleled an increase in δ¹³C measured earlier in the same samples, meaning that the dominant effect of ozone was on gas diffusion and not on CO₂ fixation. Only in R. friesianus, ozone affected both processes simultaneously. It is concluded that elevated ozone not only affects productivity, but also the water status of important component species of grassland communities.     

Effect of ozonation on the biodegradability of atrazine in GAC columns

Abstract

The biodegradation of atrazine as influenced by preozonation was studied in biological GAC columns. Metabolism of isopropyl‐¹⁴C atrazine produced more ¹⁴CO₂ than ring‐UL‐¹⁴C atrazine, indicating dealkylation was more rapid than ring cleavage. Preozonation increased mineralization of ring‐UL‐¹⁴C atrazine and, consequently, enhanced the performance of the GAC columns. Sixty‐two percent of the influent atrazine was converted to ¹⁴CO₂ in columns that received ozonated atrazine and ozonated surface water, while 50% of the influent atrazine was converted to ¹⁴CO₂ in columns that received untreated atrazine and ozonated surface water, and only 38% of the influent atrazine was converted to ¹⁴CO₂ in columns with untreated influent.     

Elevated nitrogen isotope ratios of tropical Indian aerosols from Chennai: Implication for the origins of aerosol nitrogen in South and Southeast Asia

To better understand the origins of aerosol nitrogen, we measured concentrations of total nitrogen (TN) and its isotope ratios (δ¹⁵N) in tropical Indian aerosols (PM₁₀) collected from Chennai (13.04°N; 80.17°E) on day- and night-time basis in winter and summer 2007. We found high δ¹⁵N values (+15.7 to +31.2‰) of aerosol N (0.3–3.8 μg m^?3), in which NH₄⁺ is the major species (78%) with lesser contribution from NO₃^? (6%). Based on the comparison of δ¹⁵N in Chennai aerosols with those reported for atmospheric aerosols from mid-latitudes and for the particles emitted from point sources (including a laboratory study), as well as the δ¹⁵N ratios of cow-dung samples (this study), we found that the atmospheric aerosol N in Chennai has two major sources; animal excreta and bio-fuel/biomass burning from South and Southeast Asia. We demonstrate that a gas-to-particle conversion of NH₃ to NH₄HSO₄ and (NH₄)₂SO₄ and the subsequent exchange reaction between NH₃ and NH₄⁺ are responsible for the isotopic enrichment of ¹⁵N in aerosol nitrogen.     

硅烷化改性MCM-41负载戊二酸锌催化CO2与环氧丙烷共聚制备可降解材料

以三甲基氯硅烷(TMCS)为硅烷化试剂,对MCM-41分子筛进行表面改性处理,并以此为载体制备负载型戊二酸锌催化剂(ZnGA/TMCS-MCM-41);采用红外光谱、氮气吸附-脱附和X射线衍射等分析手段对催化剂进行表征,结果表明:三甲基氯硅烷基团被成功接枝到MCM-41分子筛表面,形成比表面积略低的硅烷化MCM-41载体,但其骨架未被破坏,负载活性物质过程中,戊二酸锌能以更小的粒径均匀分散到载体的表面;聚合反应实验表明,与单纯戊二锌催化剂相比,ZnGA/TMCS-MCM-41催化剂对CO2与环氧丙烷(PO)的共聚反应显示出更高的催化效率和更快的反应速度,在反应34 h后催化效率达到86.3 g聚合物/g ZnGA;红外光谱和核磁分析表明所得共聚产物中碳酸酯结构含量大于95.8%。     

Degradation of chlorpyrifos and its hydrolysis product, 3,5,6‐trichloro‐2‐pyridinol,in soil

Abstract

The degradation of ¹⁴C‐chlorpyrifos and its hydrolysis product, 3,5,6‐trichloro‐2‐pyridinol (TCP), was investigated in soil in laboratory experiments. Between 12 and 57% of the applied chlorpyrifos persisted in a variety of agricultural soils after a 4‐week incubation. Concentrations of TCP present in these soils ranged from 1 to 34% of the applied dose. Two patterns of persistence were observed. In some soils, significant quantities of TCP and soil‐bound residues were produced, but little ¹⁴CO₂. In other soils, neither TCP nor soil‐bound residues accumulated, but large quantities of ¹⁴CO₂ were evolved. Direct treatment of fresh samples of each of these soils with ¹⁴C‐TCP resulted in rapid mineralization of TCP to ¹⁴CO₂ only in those soils in which TCP had not accumulated after chlorpyrifos treatment. The rapid mineralization of TCP in these soils was microbially mediated, but populations of soil microorganisms capable of using TCP as a sole carbon‐energy source were not detected.     

Reconstructing historical trends of polycyclic aromatic hydrocarbon deposition in a remote area of Spain using herbarium moss material

Herbarium mosses from 1879–1881, 1973–1975 and 2006–2007 were used to investigate the historical changes of atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) at a remote site in Northern Spain. Natural abundance of nitrogen and carbon isotopes was also measured in order to assess the evolution of emissions from anthropogenic sources. Nitrogen and PAH concentrations as well as δ¹³C and δ¹⁵N ratios were significantly higher in 19th century samples compared to present century samples. Moreover, PAH distribution varied over the centuries, with the trend towards enrichment in light PAHs. The carbon, nitrogen and PAH concentrations measured in the mosses tally with the historical evolution of anthropogenic emissions in the area, mainly influenced by changes in economic activities, domestic heating and road traffic density. Mosses provided by herbaria seem to offer the possibility of studying long-term temporal evolution of atmospheric PAH deposition.     

Stable carbon isotope analysis (δ13C values) of polybrominated diphenyl ethers and their UV-transformation products

Polybrominated diphenyl ethers (PBDEs) are frequently detected in food and environmental samples. We used compound specific isotope analysis to determine the δ¹³C values of individual PBDEs in two technical mixtures. Within the same technical product (DE-71 or DE-79), BDE congeners were the more depleted in ¹³C the higher brominated they were. In contrast, the products of light-induced hydrodebromination of BDE 47 and technical DE-79 were more enriched in ¹³C because of more stable bonds between ¹³C and bromine. As a result, the δ¹³C values of the irradiated solution progressed diametrically compared to those of the technical synthesis. The ratio of the δ¹³C values of BDE 47 to BDE 99 and of BDE 99 to BDE 153 are thus suggested as indicators to distinguish native technical products from transformation products. Ratios <1 are typical for native congeners (e.g. in DE-71) while the reversed ratio (>1) is typical of transformation products.