Methane fluxes from tundra soils and snowpack in the maritime Antarctic

Methane fluxes were measured from three exposed tundra sites and four snowpack sites on the Fildes Peninsula in the maritime Antarctic in the summertime of 2002. The average fluxes at two normal tundra sites were −15.3 μg m⁻² h⁻¹ and −14.3 μg m⁻² h⁻¹, respectively. The fluxes from tundra site with fresh penguin dropping addition showed positive values with the average of 36.1 μg m⁻² h⁻¹, suggesting that the deposition of fresh droppings greatly enhanced CH₄ emissions from the poor Antarctic tundra during penguin breeding periods. The summertime variation in CH₄ flux was correlated with surface ground temperature and the precipitation. The correlation between the flux and PT₀, which is the product of the precipitation and surface ground temperature, was quite strong. The diurnal cycle of CH₄ flux from the tundra soils was not obtained due to local fluky weather conditions. The fluxes through four snowpack sites were also obtained by the vertical CH₄ concentration gradient and their average fluxes were −46.5 μg m⁻² h⁻¹, −28.2 μg m⁻² h⁻¹, −46.4 μg m⁻² h⁻¹ and −17.9 μg m⁻² h⁻¹, respectively, indicating that tundra soils under snowpack also consume atmospheric CH₄ in the maritime Antarctic; therefore these fluxes could constitute an important part of the annual CH₄ budget for Antarctic tundra ecosystem.     

Cold season CH4, CO2 and N2O fluxes from freshwater marshes in northeast China

Cold season (winter and thaw) CH₄, CO₂ and N₂O fluxes from freshwater marshes (47°35′N, 133°31′E, Northeast China) were measured, using the static chamber method. The mean CH₄ and CO₂ fluxes from Carex lasiocarpa (Cl) were 0.5 ± 0.19 and 6.23 ± 1.36 mg C m⁻² h⁻¹, respectively, and those from Deyeuxia angustifoli (Da) were 0.18 ± 0.15 and 5.22 ± 2.48 mg C m⁻² h⁻¹, respectively in winter. There was no significant difference between Cl and Da (p > 0.05). The contributions of winter CH₄ fluxes were about 5.5% and 3% in the Cl and Da, respectively. Marshes are an important potential N₂O sink in winter season in northeast China. During thaw, the CH₄ and CO₂ emissions rapidly increased, 4.5–6 times of winter emissions. Wetland became a source of N₂O. Cold season gases flux from northern wetlands play an important role in the seasonal gas exchange.     

Release flux of mercury from different environmental surfaces in Chongqing, China

An investigation was conducted to estimate mercury emission to the atmosphere from different environmental surfaces and to assess its contribution to the local mercury budget in Chongqing, China. Mercury flux was measured using dynamic flux chamber (DFC) at six soil sites of three different areas (mercury polluted area, farmland and woodland) and four water surfaces from August 2003 to April 2004. The mercury emission fluxes were 3.5 ± 1.2–8.4 ± 2.5 ng m⁻² h⁻¹ for three shaded forest sites, 85.8 ± 32.4 ng m⁻² h⁻¹ for farming field, 12.3 ± 9.8–733.8 ± 255 ng m⁻² h⁻¹ for grassland sites, and 5.9 ± 12.6–618.6 ± 339 ng m⁻² h⁻¹ for water surfaces. Mercury exchange fluxes were generally higher from air/water surfaces than from air/soil surfaces. The mercury negative fluxes were found in tow soil sites at overcast days (mean = −6.4 ± 1.5 ng m⁻² h⁻¹). The diurnal and seasonal variations of mercury flux were observed in all sites. The mercury emission responded positively to the solar radiation, but negatively to the relative humidity. The mercury flux from air/soil surfaces was significantly correlated with soil temperature, which was well described by an Arrhenius-type expression with activation energy of 31.1 kcal mol⁻¹. The annual mercury emission to the atmosphere from land surface is about 1.787 t of mercury in Chongqing.     

Isoprene emission from tropical trees in Okinawa Island, Japan

This study surveyed isoprene emission from 42 indigenous and exotic tropical trees in subtropic Okinawa, Japan. Of the 42 trees studied, 4 emitted isoprene at a rate in excess of 20 μg g⁻¹ h⁻¹, and 28 showed the rates of 1–10 μg g⁻¹ h⁻¹. The remainder emitted less than 1 μg g⁻¹ h⁻¹. The majority of trees in this study may therefore fall within the lower emitting species. However, species in Moraceae that is indigenous in Okinawa emitted isoprene at relatively higher rates with an average of 14.2 μg g⁻¹ h⁻¹. The highest emission rate of 107.1 μg g⁻¹ h⁻¹ for Ficus virgata yielded the area basis rate of 47.4 nmol m⁻² s⁻¹, which is almost equivalent to the rate of high emitting species. Furthermore, a linear relationship between light intensity and isoprene emission was noted with Ficus virgata up to 1700 μmol m⁻² s⁻¹. These findings may show the potential importance of subtropical areas as sources of isoprene to the atmosphere.     

Direct measurement of denitrification activity in a Gulf coast freshwater marsh receiving diverted Mississippi River water

Wetland loss along the Louisiana Gulf coast and excessive nitrate loading into the Gulf of Mexico are interrelated environmental problems. Nitrate removal by soil denitrification activity was studied in a ponded freshwater marsh receiving diverted Mississippi River water for the purpose of reversing or slowing wetland loss. Labeled ¹⁵N-nitrate was applied at 3.8 g N m⁻² into four replicate study plots after removing above ground vegetation. Nitrogen gas (N₂) and nitrous oxide (N₂O) emissions from the plots were determined by isotope ratio mass spectrometry (IRMS). Nitrous oxide emissions were also compared with the results determined by gas chromatograph (GC). Results showed that it took 2 weeks to remove the added nitrate with N₂O emission occurring over a period of 4 d. The apparent denitrification dynamics were assumed to follow the Michaelis–Menten equation. The maximum denitrification rate and K_m value were determined as 12.6 mg N m ⁻² h⁻¹, and 6.5 mg N l⁻¹, respectively. Therefore the maximum capacity for nitrate removal by the marsh soil would be equivalent to 110 g N m⁻² yr⁻¹, with more than 30% of nitrogen gas evolved as N₂O. For typical nitrate concentrations in Mississippi River water of about 1 mg N l⁻¹, nitrate would be removed at a rate of 14.7 g N m⁻² yr⁻¹ with N₂O emission about 1.5%. A denitrification dynamic model showed that the efficiency of nitrate removal would largely depend on the water discharge rate into the ponded wetland. Higher discharge rate will result in less retention time for the water in the marsh where nitrate is denitrified.     

Mercury deposition through litterfall in an Atlantic forest at Ilha Grande, Southeast Brazil

Atmospheric Hg transfer to the forest soil through litterfall was investigated in a primary rainforest at Ilha Grande (Southeast Brazil) from January to December 1997. Litter mass deposition reached 10.0 t ha⁻¹ y⁻¹, with leaves composing 50–84% of the total litter mass. Concentrations of Hg in the total fallen litter varied from 20 to 244 ng g⁻¹, with higher concentrations during the dry season, between June and August (225 ± 17 ng g⁻¹), and lower concentrations during the rainy season (99 ± 54 ng g⁻¹). This seasonal variability was reflected in the Hg flux through litterfall, which corresponded to a Hg input to the forest floor of 122 μg m⁻² y⁻¹, with average Hg deposition of 16.5 ± 1.5 μg m⁻² month⁻¹ during and just after the dry season (June–September) and 7.0 ± 3.6 μg m⁻² month⁻¹ in the rest of the year. The variability in meteorological conditions (determining atmospheric Hg availability to foliar scavenging) may explain the pulsed pattern of Hg deposition, since litterfall temporal variability was generally unrelated with such deposition, except by a peak in litterfall production in September. Comparisons with regional data on Hg atmospheric deposition show that litterfall promotes Hg deposition at Ilha Grande two to three orders of magnitude higher than open rainfall deposition in non-industrialized areas and approximately two times higher than open rainfall deposition in industrialized areas in Rio de Janeiro State. The observed input suggests that atmospheric Hg transfer through litterfall may explain a larger fraction of the total Hg input to forest soils in Southeast Brazil than those recorded at higher latitudes.     

Monoterpene emissions and carbonyl compound air concentrations during the blooming period of rape (Brassica napus)

An increasing percentage of agricultural land in Germany is used for oil seed plants. Hence, rape has become an important agricultural plant (in Saxony 1998: 12% of the farmland) in the recent years. During flowering of rape along with intensive radiation and high temperatures, a higher production and emission of biogenic VOC was observed. The emissions of terpenes were determined and more importantly, high concentrations of organic carbonyl compounds were observed during this field experiment. All measurements of interest have been carried out during two selected days with optimal weather conditions. It is found that the origin or the mechanism of formation of different group of compounds had strong influence on the day to day variation of their concentrations. The emission flux of terpenes from flowering rape plants was determined to be 16–32 μg h⁻¹ m⁻² (30–60 ng h⁻¹ per g dry plant––540–1080 ng h⁻¹ per plant), in total. Limonene, -thujene and sabinene were the most important compounds (about 60% of total terpenes). For limonene and sabinene reference emission rates (M_S) and temperature coefficients were determined: β_limonene=0.108 K⁻¹ and M_S=14.57 μg h⁻¹ m⁻²; β_sabinene=0.095 K⁻¹ and M_S=5.39 μg h⁻¹ m⁻².

The detected carbonyl compound concentrations were unexpectedly high (maximum formaldehyde concentration was 18.1 ppbv and 3.4 ppbv for butyraldehyde) for an open field. Possible reasons for these concentrations are the combination of primary emission from the plants induced by high temperature and high ozone stress, the secondary formation from biogenically and advected anthropogenically emitted VOC at high radiation intensities and furthered by the low wind speeds at this time.     

Nitrogen trace gas emissions from a riparian ecosystem in southern Appalachia

In this paper, we present two years of seasonal nitric oxide (NO), ammonia (NH₃), and nitrous oxide (N₂O) trace gas fluxes measured in a recovering riparian zone with cattle excluded and adjacent riparian zone grazed by cattle. In the recovering riparian zone, average NO, NH₃, and N₂O fluxes were 5.8, 2.0, and 76.7 ng N m⁻² s⁻¹ (1.83, 0.63, and 24.19 kg N ha⁻¹ y⁻¹), respectively. Fluxes in the grazed riparian zone were larger, especially for NO and NH₃, measuring 9.1, 4.3, and 77.6 ng N m⁻² s⁻¹ (2.87, 1.35, and 24.50 kg N ha⁻¹ y⁻¹) for NO, NH₃, and N₂O, respectively. On average, N₂O accounted for greater than 85% of total trace gas flux in both the recovering and grazed riparian zones, though N₂O fluxes were highly variable temporally. In the recovering riparian zone, variability in seasonal average fluxes was explained by variability in soil nitrogen (N) concentrations. Nitric oxide flux was positively correlated with soil ammonium (NH₄⁺) concentration, while N₂O flux was positively correlated with soil nitrate (NO₃⁻) concentration. Ammonia flux was positively correlated with the ratio of NH₄⁺ to NO₃⁻. In the grazed riparian zone, average NH₃ and N₂O fluxes were not correlated with soil temperature, N concentrations, or moisture. This was likely due to high variability in soil microsite conditions related to cattle effects such as compaction and N input. Nitric oxide flux in the grazed riparian zone was positively correlated with soil temperature and NO₃⁻ concentration. Restoration appeared to significantly affect NO flux, which increased ≈600% during the first year following restoration and decreased during the second year to levels encountered at the onset of restoration. By comparing the ratio of total trace gas flux to soil N concentration, we show that the restored riparian zone is likely more efficient than the grazed riparian zone at diverting upper-soil N from the receiving stream to the atmosphere. This is likely due to the recovery of microbiological communities following changes in soil physical characteristics.     

Effects of different quinoid redox mediators on the removal of sulphide and nitrate via denitrification

The impact of different quinoid redox mediators on the simultaneous conversion of sulphide and nitrate in a denitrifying culture was evaluated. All quinones evaluated, including anthraquinone-2,6-disulphonate (AQDS), 2-hydroxy-1,4-naphthoquinone and 1,2-naphthoquinone-4-sulphonate (NQS) were reduced by sulphide under abiotic conditions. NQS showed the highest reduction rate by sulphide (132 μmol h⁻¹) and promoted the maximum rate of sulphide oxidation (87 μmol h⁻¹) by denitrifying sludge, which represents an increase of 44% compared to the control lacking quinones. The reduced form of AQDS (AH₂QDS) served as an electron donor for the microbial reduction of nitrite and N₂O, which represents the first demonstration of hydroquinones supporting the microbial reduction of denitrifying intermediates. The results taken as a whole suggest that some quinones may significantly increase the rate of removal of S and N under denitrifying conditions.     

Biogeochemical distinction of methane releases from two Amazon hydroreservoirs

Biogeochemical distinction of methane emissions to the atmosphere may essentially rely on the surface area and morphometry of Amazon hydroreservoirs. Tucuruí (deep) and Samuel (shallow) reservoirs released in average 13.82 ± 22.94 and 71.19 ± 107.4 mg CH₄ m⁻² d⁻¹, respectively. δ¹³C–CH₄ values from the sediments to the atmosphere indicate that the deep reservoir has extended methanotrophic layer, oxidizing large quantities of light isotope methane coming from the sediments, while sediment-generated methane can easily evade the shallow reservoir.     

Distribution of pesticides and heavy metals in trophic chain

Determination of triazines herbicides (atrazine and simazine) by high performance liquid chromatography (HPLC) in samples of trophic chain were worked out. Determination limits of 0.5 μg g⁻¹ for atrazine, 0.8 μg g⁻¹ for simazine with pesticides recovery of 70–77% in trophic chain samples were obtained. The content of simazine in soils was in range 1.72–57.89 μg g⁻¹, in grass 5–88 μg g⁻¹, in milk 2.32–15.29 μg g⁻¹, in cereals 10.98–387 μg g⁻¹, in eggs 30.14–59.48 μg g⁻¹, for fruits: 2.45–6.19 μg g⁻¹. The content of atrazine in soils was in range 0.69–19.59 μg g⁻¹, in grass 7.85–23.85 μg g⁻¹, in cereals 1.88–43.08 μg g⁻¹. Cadmium, lead and zinc were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) in the same samples as atrazine and simazine. Determination limits for cadmium 5 × 10⁻³ μg g⁻¹, for lead 1 × 10⁻² μg g⁻¹, and for zinc 0.2 × 10⁻³ μg g⁻¹, were obtained. The content of cadmium in soil was in range 0.13–5.89 μg g⁻¹, in grass 114–627.72 × 10⁻³ μg g⁻¹, in milk 8.88–61.88 × 10⁻³ μg g⁻¹, in cereals 0.20–0.31 μg g⁻¹, in eggs 0.11–0.15 μg g⁻¹, in fruits 0.23–0.59 μg g⁻¹. The content of lead in soils was in range 0.57–151.50 μg g⁻¹, in grass 0.16–136.57 μg g⁻¹, in milk 1.16–3.74 μg g⁻¹, in cereals 1.05–5.47 μg g⁻¹, in eggs 5.79–55.87 μg g⁻¹, in fruits 21.00–87.36 μg g⁻¹. Zinc content in soil was in range 9.15–424.5 μg g⁻¹, in grass 35.20–55.87 μg g⁻¹, in milk 20.00–34.38 μg g⁻¹, in cereals 14.94–28.78 μg g⁻¹, in eggs 15.67–32.01 μg g⁻¹, in fruits 14.94–18.88 μg g⁻¹.

Described below extraction and mineralization methods for particular trophic chains allowed to determine of atrazine, simazine, cadmium, lead and zinc with good repeatability and precision. Emphasis was focused on liquid–liquid extraction and solid-phase extraction of atrazine and simazine from analysed materials, as well as, on monitoring the content of herbicides and metals in soil and along trophic chain. Higher concentration of pesticides in samples from west region of Poland in comparison to that of east region is likely related to common applying them in Western Europe in relation to East Europe. The content of metals strongly depends on samples origin (industry area, vicinity of motorways).     

An inventory of N(2)O emissions from agriculture in China using precipitation-rectified emission factor and background emission

Fertilized agricultural soils are a major anthropogenic source of atmospheric N₂O. A credible national inventory of agricultural N₂O emission would benefit its global strength estimate. We compiled a worldwide database of N₂O emissions from fertilized fields that were consecutively measured for more than or close to one year. Both nitrogen input (N) and precipitation (P) were found to be largely responsible for temporal and spatial variabilities in annual N₂O fluxes (N₂O–N). Thus, we established an empirical model (N₂O–N = 1.49 P + 0.0186 P · N), in which both emission factor and background emission for N₂O were rectified by precipitation. In this model, annual N₂O emission consists of a background emission of 1.49 P and a fertilizer-induced emission of 0.0186 P · N. We used this model to develop a spatial inventory at the 10 × 10 km scale of direct N₂O emissions from agriculture in China. N₂O emissions from rice paddies were separately quantified using a cropping-specific emission factor. Annual fertilizer-induced N₂O emissions amounted to 198.89 Gg N₂O–N in 1997, consisting of 18.50 Gg N₂O–N from rice paddies and 180.39 Gg N₂O–N from fertilized uplands. Annual background emissions and total emissions of N₂O from agriculture were estimated to be 92.78 Gg N₂O–N and 291.67 Gg N₂O–N, respectively. The annual direct N₂O emission accounted for 0.92% of the applied N with an uncertainty of 29%. The highest N₂O fluxes occurred in East China as compared with the least fluxes in West China.     

Relationship between the loading rate of inorganic mercury to aquatic ecosystems and dissolved gaseous mercury production and evasion

The purpose of our study was to test the hypothesis that dissolved gaseous mercury (DGM) production and evasion is directly proportional to the loading rate of inorganic mercury [Hg(II)] to aquatic ecosystems. We simulated different rates of atmospheric mercury deposition in 10-m diameter mesocosms in a boreal lake by adding multiple additions of Hg(II) enriched with a stable mercury isotope (²⁰²Hg). We measured DGM concentrations in surface waters and estimated evasion rates using the thin-film gas exchange model and mass transfer coefficients derived from sulfur hexafluoride (SF₆) additions. The additions of Hg(II) stimulated DGM production, indicating that newly added Hg(II) was highly reactive. Concentrations of DGM derived from the experimental Hg(II) additions (“spike DGM”) were directly proportional to the rate of Hg(II) loading to the mesocosms. Spike DGM concentrations averaged 0.15, 0.48 and 0.94 ng l⁻¹ in mesocosms loaded at 7.1, 14.2, and 35.5 μg Hg m⁻² yr⁻¹, respectively. The evasion rates of spike DGM from these mesocosms averaged 4.2, 17.2, and 22.3 ng m⁻² h⁻¹, respectively. The percentage of Hg(II) added to the mesocosms that was lost to the atmosphere was substantial (33–59% over 8 weeks) and was unrelated to the rate of Hg(II) loading. We conclude that changes in atmospheric mercury deposition to aquatic ecosystems will not change the relative proportion of mercury recycled to the atmosphere.     

Trace elements in atmospheric particulate matter over a coal burning power production area of western Macedonia, Greece

Total suspended particle (TSP) concentrations were determined in the Eordea basin (western Macedonia, Greece), an area with intensive lignite burning for power generation. The study was conducted over a one-year period (November 2000–November 2001) at 10 sites located at variable distances from the power plants. Ambient TSP samples were analyzed for 27 major, minor and trace elements. Annual means of TSP concentrations ranged between 47 ± 33 μg m⁻³ and 110 ± 50 μg m⁻³ at 9 out of the 10 sites. Only the site closest to the power stations and the lignite conveyor belts exhibited annual TSP levels (210 ± 97 μg m⁻³) exceeding the European standard (150 μg m⁻³, 80/779/EEC). Concentrations of TSP and almost all elemental components exhibited significant spatial variations; however, the elemental profiles of TSP were quite similar among all sites suggesting that they are affected by similar source types. At all sites, statistical analysis indicated insignificant (P < 0.05) seasonal variation for TSP concentrations. Some elements (Cl, As, Pb, Br, Se, S, Cd) exhibited significantly higher concentrations at certain sites during the cold period suggesting more intense emissions from traffic, domestic heating and other combustion sources. On the contrary, concentrations significantly higher in the warm period were found at other sites mainly for crustal elements (Ti, Mn, K, P, Cr, etc.) suggesting stronger influence from soil resuspension and/or fly ash in the warm months. The most enriched elements against local soil or road dust were S, Cl, Cu, As, Se, Br, Cd and Pb, whereas negligible enrichment was found for Ti, Mn, Mg, Al, Si, P, Cr. At most sites, highest concentrations of TSP and elemental components were associated with low- to moderate-speed winds favoring accumulation of emissions from local sources. Influences from the power generation were likely at those sites located closest to the power plants and mining activities.     

A chemical and toxicological profile of Dutch North Sea surface sediments

Chemical and toxicological profiles were assessed in surface sediments (fraction <63 μm) from the southern North Sea. In extracts of freeze-dried samples, polybrominated biphenyl (PBB), Irgarol 1051 and phthalate concentrations were below the respective detection limits (except di(2-ethylhexyl)phthalate, which was between 170 and 3300 μg kg⁻¹ dry weight (dw)). Hexabromocyclododecane (HBCD) concentrations were between 0.8 and 6.9 μg kg⁻¹ dw, with highest concentrations at river mouths. Polybrominated diphenylethers (PBDE) concentrations were 0.4–0.6 μg kg⁻¹ dw, decabromodiphenylether (BDE209) 1–32 μg kg⁻¹ dw. The ratio BDE209/PCB153 was used as a tracer for recent emissions, and pointed towards a BDE209 source in the Western Scheldt’s upper estuary. PCBs and PAHs were between 0.19–4.7 and 2.6–200 μg kg⁻¹ dw respectively and generally had highest concentrations at near-shore locations and river mouths.

Responses in the Microtox broad-spectrum and the Mutatox genotoxicity assays were generally low, with near-shore locations giving higher responses. The umu-C genotoxicity and the ER-CALUX assay for estrogenicity showed no response, with the exception of one near-shore location (IJmuiden outer harbour, ER-CALUX).

Highest dioxin-like toxicity (DR-CALUX) was found at near-shore locations, in the outflow of the Rhine/Meuse estuary including a dumping site of harbour sludge. At the Oyster Grounds, DR-CALUX responses appeared to be linked to the occurrence of larger PAHs (4–6 rings). A new, non-destructive clean up procedure resulted in significantly higher DR-CALUX responses than the current protocol. The Dutch legislation on disposal of harbour sludge at sea, dictates the use of the conventional clean up procedure. Our results therefore indicate that probably more dioxin-like toxicity associated with harbour sludge is disposed off at sea than assumed.     

Mercury in air in an area impacted by strong industrial activities

The concentrations of total gaseous mercury (TGM) and its relevant environmental parameters were measured at a highly industrialized area in the Ban Wall industrial complex (BWIC) in An San city, Korea from March to May 2005. The mean concentrations of Hg measured during the entire study period were computed to be 6.32 ± 8.56 ng m⁻³ (range of 2.32–181 ng m⁻³; N = 1160). Due to the effects of strong man-made activities, the significantly high Hg concentration levels (e.g., at or above 10 ng m⁻³) comprised about 7.5% of all data with the mean of 21.8 ± 26.3 ng m⁻³ (N = 87). By separating the data into daytime and nighttime periods, the Hg values exhibited a notable daytime enhancement possibly due to strong man-made activities during working hours. The results of the correlation analysis indicated the possible relationship between the Hg concentration and the temperature as well as several pollutant species (e.g., NO₂ and NO_x). Evaluation of the Hg data in relation with the air mass transport pattern confirms that the Hg concentration levels in this industrial area are affected most eminently by local, rather than distant, pollution sources.     

Decomposition of chlorinated dioxins, odourous compounds and NOx from MSW incineraton plant by oxidizing catalyst

An experiment was carried out to decompose chlorinated dioxins (PCDDs, PCDFs) Chlorobenzenes, NOx and odourous compounds (H₂S, CH₄S, C₂H₆S₂, C₈H₈, C₂H₆S, C₂H₄O, NH₃) simultaneously using a catalyst in the MSW incineration plant. The experiments were conducted at temperatures from 200°C to 400°C and from 3000h⁻¹ to 6000h⁻¹ at space velocity. A catalyst containing V₂O₅ and WO₃ on the basis of TiO₂ is used, an oxidizing catalyst of the honeycomb type. The average decomposition efficiencis were 95%, 98%, 92% for PCDDs(48CDDs), PCDFs(48CDFs) and Chlorobenzenes(36CLBs) at a reaction temperature of 350°C and a space velocity of 3000h⁻¹, more than 90% for NOx at a reactiont temperature of 300°C and more than 80% for odourous compounds at the reaction temperature of 300°C and a space velocity of 6000h⁻¹. All those compounds were decomposed successfully with increasing contact time and surface. The rate-determing step was the chemical reaction of catalyst surface.     

Utilization and degradation of imazaquin by a naturally occurring isolate of Arthrobacter crystallopoietes

A species of bacteria that is capable of utilizing imazaquin as the sole carbon source was isolated from soil with repeated imazaquin applications, and was identified as Arthrobacter crystallopoietes (designated as strain “WWX-1”). This isolate degrades imazaquin as high as 200 μg ml⁻¹, and the estimated dissipation half-lives increased from 1.51 d for the treatment at 50 μg ml⁻¹ to 4.75 d for 200 μg ml⁻¹. Optimal growth of WWX-1 in mineral salt medium with 50 μg ml⁻¹ imazaquin was obtained at 35 °C and a pH of 5.0. Growth of WWX-1 was also observed in mineral salt medium with the addition of other imidazolinone herbicides such as imazethapyr and imazapyr, but not with different classes of herbicides such as metsulfuron-methyl. Two imazaquin metabolites were detected, and spectral analysis with HPLC–MS, ¹H NMR, and IR revealed one metabolite with a molecular weight (MW) of 199 as quinoline-2,3-dicarboxylic anhydride. We propose that A. crystallopoietes (WWX-1) could serve as an efficient biodegradation system for remediation of water and soils that are heavily contaminated with imazaquin or other structurally similar chemicals.     

Bioaccumulation of anthropogenic contaminants by detritivorous fish in the Río de la Plata estuary: 1-aliphatic hydrocarbons

The temporal variability and bioaccumulation dynamics of C_12–25 n-alkanes, isoprenoids and unresolved aliphatic hydrocarbons (UCM) were studied in a detritivorous fish (Sábalo: Prochilodus lineatus) collected from 1999 to 2005 in the sewage impacted Buenos Aires coastal area. Fish muscles contain huge amounts of n-C_12–25 (165 ± 93, 70 ± 48 or 280 ± 134 μg g⁻¹, dry, fresh and lipid weight, respectively) and UCM (931 ± 560, 399 ± 288 and 1567 ± 802 μg g⁻¹) reflecting the chronic bioaccumulation of fossil fuels from sewage particulates. On a temporal basis, lipid normalized aliphatic concentrations peaked by the end of 2001–2002 during the rainiest period over the last four decades (1750 vs. 1083 ± 4.6 mm in 1999, 2004 and 2005), reflecting an enhanced exposition due to massive anthropogenic fluxes from Metropolitan Buenos Aires in wet years. The hydrocarbon composition in fish muscles is enriched in n-C_15–17 and isoprenoids relative to a fresh crude oil and settling particulates, with fresher signatures during the 2001–2002 maxima. Fish/settling material bioaccumulation factors (BAFs: 0.4–6.4 dry weight or 0.07–0.94 lipid-organic carbon) plotted against K_ow showed a parabolic pattern maximizing at n-C_14–18 and isoprenoids. The optimal bioaccumulation window corresponds to highly hydrophobic (log K_ow: 7.2–9.9), intermediate-size C_14–18 n-alkanes and C_15–20 isoprenoids (MW: 198–282; length: 17.9 to 25.4 Å) with melting points ranging from −19.8 to 28 °C. The uptake efficiency is inversely correlated to melting points and increased from 75% for n-C₂₅ to above 90% for n-C_14–15 and isoprenoids.     

Fate of cancerostatic platinum compounds in biological wastewater treatment of hospital effluents

The present work focuses on the fate of two cancerostatic platinum compounds (CPC), cisplatin and carboplatin, as well as of two inorganic platinum compounds, [PtCl₄]²⁻ and [PtCl₆]²⁻ in biological wastewater treatment. Laboratory experiments modelling adsorption of these compounds onto activated sludge showed promising specific adsorption coefficients K_D and K_OC and Freundlich adsorption isotherms. However, the adsorption properties of the investigated substances were differing significantly. Adsorption decreased following the order cisplatin > [PtCl₆]²⁻ > [PtCl₄]²⁻ > carboplatin. Log K_D-values were ranging from 2.5 to 4.3 , log K_OC from 3.0 to 4.7.

A pilot membrane bioreactor system (MBR) was installed in a hospital in Vienna and fed with wastewater from the oncologic in-patient treatment ward to investigate CPC-adsorption in a sewage treatment plant. During three monitoring periods Pt-concentrations were measured in the influent (3–250 μg l⁻¹ Pt) and the effluent (2–150 μg l⁻¹ Pt) of the treatment plant using ICP-MS. The monitoring periods (duration 30 d) revealed elimination efficiencies between 51% and 63% based on averaged weekly input–output budgets. The derived log K_D-values and log K_OC-values ranged from 2.4 to 4.8 and from 2.8 to 5.3, respectively. Species analysis using HPLC-ICP-MS proofed that mainly carboplatin was present as intact drug in the influent and – due to low log K_D – in the effluent of the MBR.