Spatial and seasonal variations of Hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) in the Arctic atmosphere

Weekly high-volume air samples were collected between 2000 and 2003 at six Arctic sites, i.e., Alert, Kinngait, and Little Fox Lake (LFL) in Canada, Point Barrow in Alaska, Valkarkai in Russia, and Zeppelin in Norway. Hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were quantified in all samples. Comparison showed that alpha-HCH and HCB were homogeneously distributed in the circumpolar atmosphere and uniform throughout the seasons. However, significantly higher atmospheric concentrations of alpha-HCH and HCB and strongertemperature dependence of alpha-HCH and gamma-HCH were found at LFL in Yukon (YK), which is unique among the sites by virtue of its high altitude and low latitude, resulting in higher precipitation rates and summer temperatures. Strong temperature dependence of alpha- and gamma-HCH at this location suggests that secondary emissions, i.e., re-evaporation from surfaces, were more important at this site than others. It is hypothesized that a higher precipitation rate at LFL facilitated the transfer of alpha-HCH from the atmosphere to surface media when technical HCH was still in use worldwide. On the other hand, higher temperature at LFL enhanced reevaporation to the atmosphere after the global ban of technical HCH. In contrast to alpha-HCH and HCB, larger spatial and seasonal differences were seen for gamma-HCH (a currently used pesticide), which likely reflect the influence of different primary contaminant sources on different Arctic locations. Fugacity ratios suggest a net deposition potential of HCB from air to seawater, whereas seawater/air exchange direction of alpha-HCH varies in the circumpolar environment.     

Hexachlorocyclohexanes in the Canadian archipelago. 1. Spatial distribution and pathways of alpha-, beta- and gamma-HCHS in surface water

Hexachlorocyclohexanes (HCHs) in the surface water of the Canadian Archipelago and south Beaufort Sea were measured in summer, 1999. Overall concentrations of HCH isomers were in order of abundance: alpha-HCH (3.5 +/- 1.2 ng L(-1)) > gamma-HCH (0.31 +/- 0.07 ng L(-1)) > beta-HCH (0.10 +/- 0.03 ng L(-1)). Concentrations and ratios of alpha-HCH/gamma-HCH decreased significantly (p < 0.001 to 0.003) from west to east, but there was no significant variation in alpha-HCH/ beta-HCH. The (+) enantiomer of alpha-HCH was preferentially degraded, with enantiomer fractions (EFs) ranging from 0.432-0.463 and increasing significantly (p < 0.001) from west to east. Concentrations also varied latitudinally for alpha-HCH and gamma-HCH (p < 0.002) but not for beta-HCH. Principal component analysis with variables alpha-HCH and gamma-HCH concentrations, EF, latitude, and longitude accounted for 71% (PC 1) and 16% (PC 2) of the variance. Mixing in the eastern Archipelago was modeled by assuming three end members with characteristic concentrations of alpha-HCH and gamma-HCH. The model accounted for the observed concentrations and higher EFs of alpha-HCH at the eastern stations.     

Air-water exchange of anthropogenic and natural organohalogens on International Polar Year (IPY) expeditions in the Canadian Arctic

Shipboard measurements of organohalogen compounds in air and surface seawater were conducted in the Canadian Arctic in 2007-2008. Study areas included the Labrador Sea, Hudson Bay, and the southern Beaufort Sea. High volume air samples were collected at deck level (6 m), while low volume samples were taken at 1 and 15 m above the water or ice surface. Water samples were taken within 7 m. Water concentration ranges (pg L(-1)) were as follows: α-hexachlorocyclohexane (α-HCH) 465-1013, γ-HCH 150-254, hexachlorobenzene (HCB) 4.0-6.4, 2,4-dibromoanisole (DBA) 8.5-38, and 2,4,6-tribromoanisole (TBA) 4.7-163. Air concentration ranges (pg m(-3)) were as follows: α-HCH 7.5-48, γ-HCH 2.1-7.7, HCB 48-71, DBA 4.8-25, and TBA 6.4 - 39. Fugacity gradients predicted net deposition of HCB in all areas, while exchange directions varied for the other chemicals by season and locations. Net evasion of α-HCH from Hudson Bay and the Beaufort Sea during open water conditions was shown by air concentrations that averaged 14% higher at 1 m than 15 m. No significant difference between the two heights was found over ice cover. The α-HCH in air over the Beaufort Sea was racemic in winter (mean enantiomer fraction, EF = 0.504 ± 0.008) and nonracemic in late spring-early summer (mean EF = 0.476 ± 0.010). This decrease in EF was accompanied by a rise in air concentrations due to volatilization of nonracemic α-HCH from surface water (EF = 0.457 ± 0.019). Fluxes of chemicals during the southern Beaufort Sea open water season (i.e., Leg 9) were estimated using the Whitman two-film model, where volatilization fluxes are positive and deposition fluxes are negative. The means ± SD (and ranges) of net fluxes (ng m(-2) d(-1)) were as follows: α-HCH 6.8 ± 3.2 (2.7-13), γ-HCH 0.76 ± 0.40 (0.26-1.4), HCB -9.6 ± 2.7 (-6.1 to -15), DBA 1.2 ± 0.69 (0.04-2.0), and TBA 0.46 ± 1.1 ng m(-2) d(-1) (-1.6 to 2.0).     

Air-water gas exchange of organochlorine pesticides in Taihu Lake, China

Previous research in the Taihu Lake Region (TLR) of China found high levels of atmospheric organochlorine pesticides (OCPs). To understand the sources and the environmental behaviors of these OCPs in the TLR, research on air-water gas exchange was performed in 2004. Hexachlorocyclohexanes (HCHs), DDT related compounds (DDTs), cis-chlordane (CC), trans-chlordane (TC), heptachlor (HEPT), and alpha-endosulfan in both air and water samples were analyzed, and air-water gas exchange fluxes of these compounds were calculated. The net volatilization flux of alpha-HCH was 58 ng m(-2) day(-1), suggesting that the residue of technical HCH in the lake sediment might have been an important source of alpha-HCH to the air of this region after the ban of technical HCH two decades ago. The main components of technical chlordane, TC, CC, and HEPT, each had net volatilization fluxes >230 ng m(-2) day(-1), suggesting that waste discharge from manufacturing plants in the upper region was the main source of chlordane to the lake. Unlike alpha-HCH and chlordane, o,p'-DDT and alpha-endosulfan had net deposition fluxes, suggesting that these compounds were transported through the atmosphere from land sources and then deposited into the lake. The correlation between air concentrations and ambient air temperature indicated that the current sources of o,p'-DDT and alpha-endosulfan were from land; alpha-HCH and chlordane were mainly from the lake.     

Air-water exchange of polychlorinated biphenyls in the Delaware River

The air-water exchange of polychlorinated biphenyls (PCBs) often results in net volatilization, which is thought to be the most important loss process for PCBs in many systems. Previous investigations of the air-water exchange of PCBs have been hampered by difficulties in treatment of the uncertainty in the calculation of air/water fugacity ratios. This work presents a new framework for the treatment of uncertainty, where uncertainty in physical constants is handled differently from random measurement uncertainty associated with random samples, and it further investigates the sorption of PCBs to colloids (dissolved organic carbon). Simultaneous measurements of PCBs in the air and water of five water quality management zones of the Delaware River were taken in 2002 in support of the total maximum daily load (TMDL) process. Gas-phase concentrations of IPCBs ranged from 110 to 1350 pg m(-3), while dissolved water concentrations were between 420 and 1650 pg L(-1). Shallow slopes of log Koc vs. log Kow plots indicated a colloidal contribution to the apparent dissolved-phase concentrations, such that a three-phase partitioning model was applied. Fugacity ratios for individual congeners were calculated under the most conservative assumptions, and their values (log-transformed) were examined via a single-sample T-test to determine whether they were significantly less than 1 at the 95% confidence level. This method demonstrated that air-water exchange resulted in net volatilization in all zones over all cruises for all but seven high molecular weight congeners. Calculated net fluxes ranged from +360 to +3000 ng m(-2) d(-1) for sigma PCBs. The colloidal correction decreased the volatilization flux of sigma PCBs by approximately 30%. The decachlorinated congener (PCB 209), exhibited unusually high concentrations in the suspended solids, especially in the southern portions of the river, indicating that there is a distinct source of PCB 209 in the Delaware River.     

Endosulfan and gamma-HCH in the arctic: an assessment of surface seawater concentrations and air-sea exchange

Arctic seawater concentrations of two currently used pesticides, endosulfan and gama-HCH, were collated from a variety of cruises undertaken throughout the 1990s up to 2000 for different regions of the Arctic Ocean. Surface seawater concentrations for alpha- and beta-endosulfan ranged from <0.1-8.8 (mean 2.3) pg/L and 0.1-7.8 (mean 1.5) pg/L, while gamma-HCH concentrations were approximately 100 fold higher than alpha-endosulfan, ranging between <0.70 and 894 (mean 250) pg/L. Geographical distributions for alpha-endosulfan revealed the highest concentrations in the western Arctic, specifically in the Bering and Chukchi Seas with lowest levels toward the central Arctic Ocean. In contrast, gamma-HCH revealed higher concentrations toward the central Arctic Ocean, with additional high concentrations in the coastal regions near Barrow, Alaska and the White Sea in northwest Russia, respectively. A fugacity approach was employed to assess the net direction of air-water transfer of these two pesticides, using coupled seawater and air concentrations. For alpha-endosulfan, water-air fugacity ratios (FR) were all <1 indicating net deposition to all regions of the Arctic Ocean, with the lowest values (0.1-0.2) evident in the Canadian Archipelago. Given the uncertainty in the temperature-adjusted Henry's Law constant (factor approximately10), it is plausible that equilibrium may have been reached for this compound in the western fringes of the Arctic Ocean where the highest water concentrations were observed. Similarly, FR values for gamma-HCH were generally <1 and in agreement     

Formation of aqueous MgUO2(CO3)3(2-) complex and uranium anion exchange mechanism onto an exchange resin

The formation of and stability constants for aqueous Mg-UO2-CO3 complexes were determined using an anion exchange method. Magnesium concentration was varied (up to 20 mmol/L) at constant ionic strength (I = 0.101, 0.202, 0.304, 0.406, and 0.509 mol/kg NaNO3), pH 8.1, total [U(VI)] = 10.4 micromol/L under equilibrium with atmospheric CO2. The results indicate that only the MgUO2(CO3)3(2-) complex is formed. The cumulative formation constant extrapolated to zero ionic strength is similar regardless of the activity correction convention used: logbeta113(0) = 25.8 +/- 0.5 using the Davies equation and = 25.02 +/- 0.08 using specific ion interaction theory (SIT). Uranium sorption onto the exchange resin decreased in the presence of Mg putatively due to the formation of MgUO2(CO3)3(2-) that had a lower affinity for the resin than UO2(CO3)3(4-). Uranium sorption results are consistent with an equivalent anion exchange reaction between NO3- and UO2(CO3)3(4-) species to retain charge neutrality regardless of Mg concentration. No Mg was associated with the anion exchange resin indicating that the MgUO2(CO3)3(2-) complex did not sorb.     

Air-water exchange and dry deposition of polybrominated diphenyl ethers at a coastal site in Izmir Bay, Turkey

The air-water exchange of polybrominated diphenyl ethers (PBDEs), an emerging class of persistent organic pollutants (POPs), was investigated using paired air-water samples (n = 15) collected in July and December, 2005 from Guzelyali Port in Izmir Bay, Turkey. Total dissolved-phase water concentrations of PBDEs (sigma7PBDEs) were 212 +/- 65 and 87 +/- 57 pg L(-1) (average +/- SD) in summer and winter, respectively. BDE-209 was the most abundant congener in all samples, followed by BDE-99 and -47. Average ambient gas-phase sigma7PBDE concentrations were between 189 +/- 61 (summer) and 76 +/- 65 pg m(-3) (winter). Net air-water exchange fluxes ranged from -0.9 +/- 1.0 (BDE-28) (volatilization) to 11.1 +/- 5.4 (BDE-209) ng m(-2) day(-1) (deposition). The BDE-28 fluxes were mainly volatilization while the other congeners were deposited. Gas- and dissolved-phase concentrations were significantly correlated (P = 0.33-0.55, p < 0.05, except for BDE-209, r = 0.05, p > 0.05) indicating thatthe atmosphere controls the surface water PBDE levels in this coastal environment. Estimated particulate dry deposition fluxes ranged between 2.7 +/- 1.9 (BDE-154) and 116 +/- 84 ng m(-2) day(-1) (BDE-209) indicating that dry deposition is also a significant input to surface waters in the study area.     

Modelling the effect of gas composition on the gas exchange rate in Perforation-Mediated Modified Atmosphere Packaging

Modified Atmosphere Packaging (MAP) relies on modification of the atmosphere inside a package, achieved by the natural interplay between the respiration of the product and the transfer of gases through the package. Polymeric films are the most usual packaging material but because of the increase in the consumption of fresh-cut products with a higher respiration rate and higher tolerance to CO₂, alternative materials are being investigated. The perforation-mediated package is one of those alternatives, where the regulation of the gas exchange is achieved by single or multiple tubes that perforate an otherwise impermeable packaging material. From an engineering point of view, the transport of gases through perforations is a complex phenomenon that involves diffusion gradients together with co-current transport of multiple species, with oxygen entering the package and carbon dioxide leaving it. The influence of one species transport in the other has not been studied so far. The objective of this work was to analyse the effect of initial concentration of CO₂ on the effective mass transfer coefficients of O₂ (K_O2) and CO₂ (K_CO2) in perforation-mediated MAP. K_O2 ranged from (6.99 ± 0.05) × 10⁻⁸ (m³ s⁻¹) to (28.50 ± 0.01) × 10⁻⁸ (m³ s⁻¹) and for K_CO2 from (6.45 ± 0.04) × 10⁻⁸ (m³ s⁻¹) to (28.32 ± 0.01) × 10⁻⁸ (m³ s⁻¹). On average K_O2 decreased by approximately 15% with an increase of CO₂ initial concentration from 25% to 100%. K_CO2 was insensitive to the composition of the gas mix. The permeability ratio (β) varied from 0.73 ± 0.01 to 1.34 ± 0.01. A mathematical model considering the co-current effect of CO₂ flux on the gas exchange rate for O₂ was developed. These results suggest that there is a significant drag effect in the gas exchange process that should be taken into consideration when designing perforation-mediated MAP.     

Di-(2-ethylhexyl) adipate and 20 phthalates in composite food samples from the 2013 Canadian Total Diet Study

A sensitive and selective GC-MS method was developed and used for simultaneous analysis of di-(2-ethylhexyl) adipate (DEHA) and 20 selected phthalates in the food samples from the 2013 Canadian Total Diet Study. At least one of the 21 target chemicals was detected in 141 of the 159 different food composite samples analysed. However, only seven of the 21 target chemicals were detected, with di-(2-ethylhexyl) phthalate (DEHP) and DEHA being detected most frequently, in 111 and 91 different food composite samples, respectively, followed by di-n-butyl phthalate (DBP) (n = 44), n-butyl benzyl phthalate (BBzP) (32), di-iso-butyl phthalate (DiBP) (27), di-ethyl phthalate (DEP) (3), and di-cyclohexyl phthalate (DCHP) (1). Levels of DEP (di-ethyl phthalate), DiBP, DBP, BBzP and DCHP were low, in general, with average concentrations of 9.63, 8.26, 23.2, 12.4 and 64.9 ng g^–1, respectively. Levels of DEHA and DEHP varied widely, ranging from 1.4 to 6010 ng g^–1 and from 14.4 to 714 ng g^–1, respectively. High levels of DEHA were found mainly in the composite samples where the individual food items used to prepare the composite were likely packaged in polyvinyl chloride (PVC) wrapping film, while the highest DEHP levels were found in the vegetable and fruit samples.     

Manufacturing origin of perfluorooctanoate (PFOA) in Atlantic and Canadian Arctic seawater

The extent to which different manufacturing sources and long-range transport pathways contribute to perfluorooctanoate (PFOA) in the world's oceans, particularly in remote locations, is widely debated. Here, the relative contribution of historic (i.e., electrochemically fluorinated) and contemporary (i.e., telomer) manufacturing sources was assessed for PFOA in various seawater samples by an established isomer profiling technique. The ratios of individual branched PFOA isomers were indistinguishable from those in authentic historic standards in 93% of the samples examined, indicating that marine processes had little influence on isomer profiles, and that isomer profiling is a valid source apportionment tool for seawater. Eastern Atlantic PFOA was largely (83-98%) of historic origin, but this decreased to only 33% close to the Eastern U.S. seaboard. Similarly, PFOA in the Norwegian Sea was near exclusively historic, but the relative contribution decreased to ～50% near the Baltic Sea. Such observations of contemporary PFOA in coastal source regions coincided with elevated concentrations, suggesting that the continued production and use of PFOA is currently adding to the marine burden of this contaminant. In the Arctic, a spatial trend was observed whereby PFOA in seawater originating from the Atlantic was predominantly historic (up to 99%), whereas water in the Archipelago (i.e., from the Pacific) was predominantly of contemporary origin (as little as 17% historic). These data help to explain reported temporal and spatial trends from Arctic wildlife biomonitoring, and suggest that the dominant PFOA source(s) to the Pacific and Canadian Arctic Archipelago are either (a) from direct emissions of contemporary PFOA via manufacturing or use in Asia, or (b) from atmospheric transport and oxidation of contemporary PFOA-precursors.     

离子交换非织造布在电去离子技术中的应用

电去离子技术(EDI)是将电渗析与离子交换有机结合形成的一种新型膜分离技术,EDI膜堆的核心技术之一是填充材料的选择与应用。探讨了离子交换非织造布填充方式对膜堆电流、淡水室和浓水室出水电导率以及铜离子去除率等性能的影响。实验结果表明:采用离子交换非织造布缩短了离子的定向扩散和迁移距离,并有利于离子交换树脂的均匀填充,可明显提高离子迁移速率,使淡水室出水电导率大幅下降,浓水室出水电导率大幅上升,铜离子去除率提高;在三淡二浓膜堆结构中,全部填充离子交换非织造布的膜堆与只填充离子交换树脂的膜堆相比,其淡水室出水电导率下降至10%,浓水室出水电导率上升到10倍,淡水室出水的铜离子去除率达100%。填充非织造布的EDI装置在金属离子废水处理方面将具有广阔的应用前景。     

Cesium and strontium ion exchange on the framework titanium silicate M2Ti2O3SiO4.nH2O (M = H, Na)

The ion exchange properties of the titanium silicate, M2Ti2O3SiO4.nH2O (M = H, Na), toward stable and radioactive 137Cs+ and 89Sr2+, have been examined. By studying the cesium and strontium uptake in the presence of NaNO3, CaCl2, NaOH, and HNO3 (in the range of 0.01-6 M) the sodium titanium silicate was found to be an efficient Cs+ ion exchanger in acid, neutral, and alkaline media and an efficient Sr2+ ion exchanger in neutral and alkaline media, which makes it promising for treatment of contaminated environmental media and biological systems.     

The detection of the thiocyanate ion (SCN-) in hen's egg by gas chromatography.

The free thiocyanate ion (SCN^?) content of eggs from five different strains of hen was determined by gas chromatograph as cyanogen bromide after treating the deproteinised liquid whole egg with aqueous bromine solution. Interference by cyanide and residual protein after deproteinisation with phosphotungstic acid was not found to have any noticeable effect on the results. Samples spiked with known concentrations of SCN^? gave recoveries of 95%. The levels of SCN^? detected ranged from 0.54–0.675 mg kg^?1. There was very little variation in the levels detected from one strain of hens over a period of 10 weeks. The amount present presumably originating from the detoxification of cyanide in the liver and kidney would be insufficient to promote bactericidal activity, when incorporated into the lactoperoxidase/thiocyanate/hydrogen peroxide antimicrobial system.     

Evaluation of CO2 absorption and desorption rate in oysters (Cassostrea gigas) using the soluble gas stabilisation method

Soluble gas stabilisation (SGS) is a recently proposed method to extend the shelf life of food. However, no studies have determined the amount of carbon dioxide absorbed in food and particularly in oysters. Thus, the aim of this study was to determine CO₂ absorption and desorption rates in oysters during the solubilisation process. Cooked oysters were placed in the apparatus's chamber, CO₂ was injected into the chamber, and the SGS process started at different pressures, temperatures and gas/product (g/p) ratios. CO₂ absorption and desorption rates were obtained from data of CO₂ concentration in the chamber headspace and calculated by mathematical models. The results showed higher absorption rates under higher pressure, higher g/p ratio and lower temperature (0 °C). The concentration of CO₂ dissolved in the oysters was 21008.45 mg CO₂ kg product^?1. On the other hand, lower desorption rates occurred for the lowest pressure (200 kPa) and lowest gas/product ratio (1:1). For CO₂ desorption from oysters, it was observed that 10 min was enough to desorb a large amount of CO₂ under normal atmosphere.     

Effects of applied water amounts at various fractions of evapotranspiration (ETc) on leaf gas exchange of Thompson Seedless grapevines

Aims: To determine the effects of applied water amounts at various fractions (0.2, 0.6, 1.0 and 1.4) of grapevine evapotranspiration on leaf gas exchange of Thompson Seedless grapevines. Methods and Results: Midday stomatal conductance (g_s) decreased linearly as leaf water potential (Ψ_l) and soil water content decreased. Leaf net CO₂ assimilation rate only decreased once midday Ψ_l values were less than ?1.0 MPa and when ～50% of the soil water content at field capacity had been depleted. The mean seasonal midday A/g_s ratio (intrinsic water use efficiency) was greatest for the 0.2 irrigation treatment and decreased as applied water amounts increased. Diurnal A and g_s for vines irrigated at the 0.6 level or greater reached a maximum prior to midday remained constant thereafter before decreasing late in the afternoon, while those for vines that received less water decreased subsequent to the first measurement of the day. Conclusions: A and g_s responded differently to vine and soil water statuses under the conditions of this study. There was no midday depression in either A or g_s for vines irrigated at full evapotranspiration. Significance of the Study: The values of Ψ_l, A and g_s reported here would serve as criteria to indicate that vines were well watered.