石油烃对水产品质量安全影响及风险评估

随着工农业的迅猛发展,近海遭到不同程度的污染,特别是石油工业和海上交通运输业的发展,使得石油成为近海中最主要的污染物。石油烃主要是由碳和氢元素组成的烃类物质,包括烷烃、环烷烃、芳香烃三类。水域中石油类污染物通过呼吸和皮肤渗透容易在水生生物体中蓄积,不仅能使鱼、虾、贝类海产品变味,严重时能产生毒性效应,进而影响水产品的食用安全。本文从石油烃的特性、污染现状、国内外限量标准、石油烃污染的感官评定等方面进行了综述,并对人体健康的影响进行了评价,以期为水产品的质量安全监管提供依据。     

Hydrogen isotopic composition of individual n-alkanes as an intrinsic tracer for bioremediation and source identification of petroleum contamination

The isotopic signatures of crude oil hydrocarbons are potentially powerful intrinsic tracers to their origins and the processes by which the oils are modified in the environment. Stable carbon isotopic data are of limited use for studying petroleum contaminants because of the relatively small amount of isotopic fractionation that occurs during natural processes. Hydrogen isotopes, in contrast, are commonly fractionated to a much greater extent and as a result display larger variations in delta values. We studied the effect of in vitro aerobic biodegradation on the hydrogen isotopic composition of individual n-alkanes from crude oil. The isotopic analysis was conducted using gas chromatography-thermal conversion-isotope ratio mass spectrometry. In general, biodegradation rates decreased with increasing hydrocarbon chain length, consistent with previous studies. More importantly the n-alkanes that were degraded at the fastest rates (n-C15 to n-C18) also showed the largest overall isotopic fractionation (approximately 12-25 per thousand deuterium enrichment), suggesting that the lower molecular weight n-alkanes can be used to monitor in-situ bioremediation of crude oil contamination. The hydrogen isotopic compositions of the longer chain alkanes (n-C19 to n-C27) were relatively stable during biodegradation (<5%o overall deuterium enrichment), indicating that these compounds are effective tracers for oil-source identification studies.     

Isotopic constraints on the fate of petroleum residues sequestered in salt marsh sediments

To provide a new perspective on the fate of petroleum in the marine environment, we utilized variations in the natural abundance of radiocarbon (14C) to detect and quantify petroleum residues that have persisted in Wild Harbor sediments, West Falmouth, MA, for more than 30 years. The 5730-yr half-life of 14C makes this isotope ideal for the detection of fossil-fuel-derived contaminants (14C free) within different fractions of natural organic matter (modern 14C content) in environmental matrixes. Samples of both contaminated and uncontaminated sediments were sequentially treated, first by solvent extraction, followed by saponification, and then acid hydrolysis. Radiocarbon analysis of the sediment residues and select extracts was performed to probe for the presence of fossil fuel contaminants and/or their metabolites in different pools of sedimentary organic matter. Our results indicate that the majority of fossil carbon is solvent-extractable and has not been incorporated in the insoluble organic matter in sediment. Unextracted sediments contaminated with petroleum contain significantly less 14C than extracted sediments, and isotope mass balance calculations suggest that up to approximately 9% of the total organic carbon (TOC) in the petroleum contaminated sediment horizons is derived from solvent-extractable petroleum. These estimates are similar to values calculated when the total quantities of oil (measured by gas chromatography with flame ionization detector (GC-FID)) are compared to TOC content (determined by elemental analysis). These results pave the way for applications of this isotopic approach to more complex environmental systems where the fate of contaminants is less certain.     

Determination of microbial carbon sources in petroleum contaminated sediments using molecular 14C analysis

Understanding microbial carbon sources is fundamental to elucidating the role of microbial communities in carbon cycling and in the biodegradation of organic contaminants. Because the majority of anthropogenic contaminants are either directly or indirectly derived from fossil fuels that are devoid of 14C, radiocarbon can be used as a natural inverse tracer of contaminant carbon in the contemporary environment. Here, 14C analysis of individual microbial phospholipid fatty acids (PLFA) was used to characterize the carbon sources utilized bythe active microbial community in salt marsh sediments contaminated by the Florida oil spill of 1969 in Wild Harbor, West Falmouth, MA. A specific goal was to determine whether this community is actively degrading petroleum residues that persist in these sediments. The delta14C values of microbial PLFA in all sediment horizons (contaminated and noncontaminated) matched the delta14C of the total sedimentary organic carbon after petroleum removal, indicating that no measurable metabolism of petroleum residues was occurring. This result agrees with ancillary data such as the delta13C content and distribution of PLFA, and the residual hydrocarbon composition determined by comprehensive two-dimensional gas chromatography (GCxGC) analysis. We hypothesize that microbes have chosen to respire the natural organic matter rather than the residual petroleum hydrocarbons because the former is more labile. Future efforts directed at determining indices of microbial degradation of petroleum hydrocarbons should consider competition with natural organic matter.     

菲律宾蛤仔(Ruditapes philippinarum)养殖水体中石油烃安全限量的研究

石油烃污染是影响双壳贝类食用安全的重要因素。文中以菲律宾蛤仔(Ruditapes philippinarum)为研究对象,采用半静态动力学富集实验探讨了双壳贝类对养殖水体中石油烃的富集规律。结果表明,经过4 d,石油烃在贝体和水环境之间达到稳态平衡;生物富集系数(BCF)为545;石油烃浓度为0.068 mg/L的水体组,富集平衡后贝体内的石油烃含量高于菲律宾蛤仔的石油烃异味阈值(25~30 mg/kg),其它水体组则相反。参考USEP-A、GB18421-2001等关于双壳贝类中石油烃安全限量的规定,经讨论贝体内石油多环芳烃的毒力代谢机理后,判定菲律宾蛤仔养殖水体中石油烃的安全限量定为0.05 mg/L较为合理。     

Humic substances and crude oil induce cytochrome P450 1A expression in the Amazonian fish species Colossoma macropomum (Tambaqui)

Cytochrome P450 1A (CYP1A) induction is used widely as a biomarker of exposure to pollutants, such as petroleum hydrocarbons, yet CYP1A inducibility has been characterized in few tropical fish. Using Western blot analysis, catalytic assay, and immunohistochemistry, we evaluated CYP1A induction in an Amazonian fish (tambaqui; Colossoma macropomum) acclimated to humic substances (HS) and acutely exposed to crude oil. HS are ubiquitous in Amazonian waters, and they are known to affect the bioavailability of pollutants. CYP1A activity was also measured in fish exposed for 10 days to a range of concentrations of HS from both natural and commercial sources. Crude oil induced CYP1A expression in tambaqui, as expected. Exposure to both HS and crude oil resulted in greater levels of CYP1A expression relative to that in fish exposed to petroleum alone. Interestingly, CYP1A induction was also observed in fish exposed to HS alone. Induction by HS was concentration-dependent, and activity was higher in fish exposed to HS from the commercial source than in fish exposed to the HS from the natural source. The use of CYP1A as a biomarker of exposure to pollutants such as petroleum hydrocarbons in fish living in environments rich in humic substances should be considered with caution given that HS themselves induce CYP1A expression. Our results suggest that there may be as yet unknown CYP1A inducing components (aryl hydrocarbon receptor agonists) in humic substances.     

Using the biotic ligand model for predicting the acute sensitivity of cladoceran dominated communities to copper in natural surface waters

In this study, the acute copper sensitivity of field-collected cladoceran species was determined using their natural surface waters and a standard reconstituted test water as test medium. A total of 43 species were collected on two occasions from six different sites, representing different water types and chemistries in Europe. The collected species belonged to four different families (Daphniidae, Bosminidae, Macrothricidae, Chydoridae) and 11 different genera (Daphnia, Ctenodaphnia, Ceriodaphnia, Simocephalus, Scapholeberis, Alona, Acroperus, Chydorus, Eurycercus, Disparalona, Pleuroxus). In acute experiments with immobilization as end point, the 48-h median effective concentrations (48-h EC50) for the cladoceran species ranged from 5.30 to 70.6 microg of Cu L(-1) in standard test water and from 9.60 to 853 microg of Cu L(-1) in natural waters. The mean site sensitivity (the geometric mean of 48-h EC50 values of species within a community) ranged from 10.1 to 27.4 microg of Cu L(-1) in standard water and from 16.4 to 281 microg of Cu L(-1) in natural water. This indicates that bioavailability is more importantthan inter-community (species composition) differences in determining the variability of copper toxicity across different aquatic systems. For the four surface waters that had a pH within the range for which the acute Daphnia magna biotic ligand model (BLM) has previously been successfully validated, the BLM predicted 48-h EC50 values for 27 of the 28 tested cladoceran species within factor of 2 of the observed values. For the same sites, all community sensitivities were predicted within a factor of 2.3. The BLM was clearly over-protective for the two acidic surface waters tested. Hence, the BLM can be considered a valuable tool for estimating the potentially harmful effects of copperto natural cladoceran communities, but more research will be needed for acidic surface waters.     

Calibration and field verification of semipermeable membrane devices for measuring polycyclic aromatic hydrocarbons in water

The use of semipermeable membrane devices (SPMDs) has become common in environmental sampling of nonpolar organic contaminants, yet few data exist for the uptake or sampling rates of polycyclic aromatic hydrocarbons (PAH). Two separate laboratory calibration experiments were conducted to determine the sampling rates of 28 individual PAH and 19 homologues. PAH with a log Kow > 4.5 remained in the linear uptake phase for 30 days, but PAH with a log Kow < 4.5 began to approach steady state within 15 days. Sampling rates, corrected for dissolved organic carbon, ranged from 2.11 to 6.06 L d(-1). Shear flow across the membrane had no statistically significant effect on rates over the range of 0.01-0.50 cm s(-1). Field verification of these sampling rates yielded agreement within about a factor of 2 for most PAH and a factor of 4 for all PAH. The worst agreement was for the most hydrophobic PAH, where partitioning into dissolved and particulate organic carbon pools are more important and less certain. These SPMD sampling rate data will allow quantitative estimations of freely dissolved concentrations of 47 compounds that are commonly used for PAH and petroleum product source identification and allocation.     

A sensory system at the interface between urban stormwater runoff and salmon survival

Motor vehicles are a major source of toxic contaminants such as copper, a metal that originates from vehicle exhaust and brake pad wear. Copper and other pollutants are deposited on roads and other impervious surfaces and then transported to aquatic habitats via stormwater runoff. In the western United States, exposure to non-point source pollutants such as copper is an emerging concern for many populations of threatened and endangered Pacific salmon (Oncorhynchus spp.) that spawn and rear in coastal watersheds and estuaries. To address this concern, we used conventional neurophysiological recordings to investigate the impact of ecologically relevant copper exposures (0-20 microg/L for 3 h) on the olfactory system of juvenile coho salmon (O. kisutch). These recordings were combined with computer-assisted video analyses of behavior to evaluate the sensitivity and responsiveness of copper-exposed coho to a chemical predation cue (conspecific alarm pheromone). The sensory physiology and predator avoidance behaviors of juvenile coho were both significantly impaired by copper at concentrations as low as 2 microg/L. Therefore, copper-containing stormwater runoff from urban landscapes has the potential to cause chemosensory deprivation and increased predation mortality in exposed salmon.     

Photooxidation of Hg(0) in artificial and natural waters

The oxidation of volatile aqueous Hg(0) in aquatic systems may be important in reducing fluxes of Hg out of aquatic systems. Here we report the results of laboratory and field experiments designed to identify the parameters that control the photooxidation of Hg(0)(aq) and to assess the possible importance of this process in aquatic systems. The concentrations of elemental and total Hg were measured as a function of time in both artificial and natural waters irradiated with a UV-B lamp. No change in Hg speciation was observed in dark controls, while a significant decrease in Hg(0) was observed in UV-B irradiated artificial solutions containing both chloride ions and benzoquinone. Significant photooxidation rates were also measured in natural samples spiked with Hg(0)(aq); the photooxidation of Hg(0) then follows pseudo first-order kinetics (k = 0.6 h(-1)). These results indicate that the previously observed Hg(II) photoreduction rates in natural waters could represent a net balance between Hg(0) photoreduction and Hg(0) photooxidation. As calculated from Hg(0) photooxidation rates, the dominant Hg(0) sink is likely to be photooxidation rather than volatilization from the water column during summer days.     

Impact of surface water conditions on preservative leaching and aquatic toxicity from treated wood products

New alternative wood preservatives contain higher levels of copper (Cu) which can promote aquatic toxicity in natural water systems. Earlier work focused on evaluating toxicity using laboratory generated leaching solutions. In this study, the impact on preservative leaching and aquatic toxicity from treated wood products was evaluated using natural surface waters including waters from two rivers, three lakes, two wetlands, and one seawater, in addition to synthetic moderate hard water and deionized water. Blocks of wood treated with Cu based alternatives such as alkaline copper quaternary (ACQ) and copper boron azole (CBA), along with chromated copper arsenate (CCA)-treated wood, were leached under quiescent conditions, and total Cu, labile Cu, and heavy metal toxicity were measured. Results show that ACQ- and CBA-treated wood leach approximately 10 and 20 times more total Cu relative to CCA-treated wood and that the presence of organic and inorganic ligands in natural waters lowered the labile fraction of Cu relative to that from laboratory generated leaching solutions. Aquatic toxicity was found to correlate with the labile Cu fraction, and hence, the aquatic toxicity of the treated wood leachates was lower in natural waters in comparison to laboratory leaching solutions. The results of the present study suggest that studies designed to evaluate the impacts of treated wood should therefore consider the role of complexation in reducing the labile Cu fraction and its potential role in decreasing toxicity.     

Sea breeze modulated volatilization of polycyclic aromatic hydrocarbons from the Masnou Harbor (NW Mediterranean Sea)

Harbors, marinas, and coastal environments are impacted by important pollutant loadings, particularly of polycyclic aromatic hydrocarbons (PAHs). Air-water exchange is an important process driving the environmental fate of organic pollutants in aquatic environments. However, its relevance as a factor affecting the environmental fate of pollutants from harbor sediments and waters has not been properly assessed, so far, except for few coastal environments. The objective of this study is to quantify the importance of volatilization losses of PAHs from harbor sediments and waters and to study the potential role of sea breeze as a modulator of air-water exchange in coastal environments. The results show that volatilization fluxes from a medium size marina located in the NW Mediterranean sea are relatively high in comparison to those observed in other aquatic systems, particularly for the low molecular weight (MW) compounds. This is consistent with PAHs profiles observed in harbor sediments, which are depleted by the lower MW hydrocarbons. Therefore, volatilization is an important loss of low MW PAHs such as phenanthrene, methyl phenanthrene, dibenzothiophene, etc. Indeed, these PAHs have a residence time of few days in the harbor waters and sediments. Finally, the diurnal trends in volatilization fluxes mimics that of the sea breeze influenced wind speed. These results show the important role that the diurnal sea breeze exerts on the environmental fate of pollutants such as PAHs in coastal environments as a modulator of air-water exchange and as a potential driver of transport of pollutants between adjacent coastal and terrestrial environments.     

Fate of tetracycline resistance genes in aquatic systems: migration from the water column to peripheral biofilms

Antibiotic resistance genes (ARGs) are emerging contaminants that are being found at elevated levels in sediments and other aquatic compartments in areas of intensive agricultural and urban activity. However, little quantitative data exist on the migration and attenuation of ARGs in natural ecosystems, which is central to predicting their fate after release into receiving waters. Here we examined the fate of tetracycline-resistance genes in bacterial hosts released in cattle feedlot wastewater using field-scale mesocosms to quantify ARG attenuation rate in the water column and also the migration of ARGs into peripheral biofilms. Feedlot wastewater was added to fifteen cylindrical 11.3-m3 mesocosms (some of which had artificial substrates) simulating five different receiving water conditions (in triplicate), and the abundance of six resistance genes (tet(O), tet(W), tet(M), tet(Q), tet(B), and tet(L)) and 16S-rRNA genes was monitored for 14 days. Mesocosm treatments were varied according to light supply, microbial supplements (via river water additions), and oxytetracycline (OTC) level. First-order water column disappearance coefficients (kd) for the sum of the six genes (tetR) were always higher in sunlight than in the dark (-0.72 d(-1) and -0.51 d(-1), respectively). However, water column kd varied among genes (tet(O) < tet(W) < tet(M) < tet(Q); tet(B) and tet(L) were below detection) and some genes, particularly tet(W), readily migrated into biofilms, suggesting that different genes be considered separately and peripheral compartments be included in future fate models. This work provides the first quantitative field data for modeling ARG fate in aquatic systems.     

Hydrogen isotopic enrichment: an indicator of biodegradation at a petroleum hydrocarbon contaminated field site

Compound-specific carbon and hydrogen isotope analysis was used to investigate biodegradation of benzene and ethylbenzene in contaminated groundwater at Dow Benelux BV industrial site. delta13C values for dissolved benzene and ethylbenzene in downgradient samples were enriched by up to 2+/-0.5 per thousand, in 13C, compared to the delta13C value of the source area samples. delta2H values for dissolved benzene and ethylbenzene in downgradient samples exhibited larger isotopic enrichments of up to 27+/-5 per thousand for benzene and up to 50+/-5 per thousand for ethylbenzene relative to the source area. The observed carbon and hydrogen isotopic fractionation in downgradient samples provides evidence of biodegradation of both benzene and ethylbenzene within the study area at Dow Benelux BV. The estimated extents of biodegradation of benzene derived from carbon and hydrogen isotopic compositions for each sample are in agreement, supporting the conclusion that biodegradation is the primary control on the observed differences in carbon and hydrogen isotope values. Combined carbon and hydrogen isotope analyses provides the ability to compare biodegradation in the field based on two different parameters, and hence provides a stronger basis for assessment of biodegradation of petroleum hydrocarbon contaminants.     

Stable carbon isotope evidence for intrinsic bioremediation of tetrachloroethene and trichloroethene at area 6, Dover Air Force Base

Area 6 at Dover Air Force Base (Dover, DE) has been the location of an in-depth study by the RTDF (Remediation Technologies Development Forum Bioremediation of Chlorinated Solvents Action Team) to evaluate the effectiveness of natural attenuation of chlorinated ethene contamination in groundwater. Compound-specific stable carbon isotope measurements for dissolved PCE and TCE in wells distributed throughout the anaerobic portion of the plume confirm that stable carbon isotope values are isotopically enriched in 13C consistent with the effects of intrinsic biodegradation. During anaerobic microbial reductive dechlorination of chlorinated hydrocarbons, the light (12C) versus heavy isotope (13C) bonds are preferentially degraded, resulting in isotopic enrichment of the residual contaminant in 13C. To our knowledge, this study is the first to provide definitive evidence for reductive dechlorination of chlorinated hydrocarbons at a field site based on the delta13C values of the primary contaminants spilled at the site, PCE and TCE. For TCE, downgradient wells show delta13C values as enriched as -18.0/1000 as compared to delta13C values for TCE in the source zone of -25.0 to -26.0/1000. The most enriched delta13C value on the site was observed at well 236, which also contains the highest concentrations of cis-DCE, VC, and ethene, the daughter products of reductive dechlorination. Stable carbon isotope signatures are used to quantify the relative extent of biodegradation between zones of the contaminant plume. On the basis of this approach, it is estimated that TCE in downgradient well 236 is more than 40% biodegraded relative to TCE in the proposed source area.     

Quantifying the degradation and dilution contribution to natural attenuation of contaminants by means of an open system rayleigh equation

Quantifying the share of destructive and nondestructive processes to natural attenuation (NA) of groundwater pollution plumes is of high importance to the evaluation and acceptance of NA as remediation strategy. Dilution as consequence of hydrodynamic dispersion may contribute considerably to NA, however, without reducing the mass of pollution. Unfortunately, tracers to quantify dilution are usually lacking. Degradation though of low-molecular-weight organic chemicals such as BTEX, chlorinated ethenes, and MTBE is uniquely associated with increases in isotope ratios for steady-state plumes. Compound-specific isotope analysis (CSIA) data are commonly interpreted by means of the Rayleigh equation, originally developed for closed systems, to calculate the extent of degradation under open system field conditions. For that reason, the validity of this approach has been questioned. The Rayleigh equation was accordingly modified to account for dilution, and showed that dilution contributed several to many times more to NA than biodegradation at a groundwater benzene plume. Derived equations also (i) underlined that field-derived isotopic enrichment factors underestimate actual values operative as a consequence of dilution, and (ii) provided a check on the lower limit of isotopic fractionation, thereby resulting in more reliable predictions on the extent of degradation.     

Naphthenic acids in athabasca oil sands tailings waters are less biodegradable than commercial naphthenic acids

Naphthenic acids (NAs) are natural constituents in many petroleum sources, including bitumen in the oil sands of Northern Alberta, Canada. Bitumen extraction processes produce tailings waters that cannot be discharged to the environment because NAs are acutely toxic to aquatic species. However, aerobic biodegradation reduces the toxic character of NAs. In this study, four commercial NAs and the NAs in two oil sands tailings waters were characterized by gas chromatography-mass spectrometry. These NAs were also incubated with microorganisms in the tailings waters under aerobic, laboratory conditions. The NAs in the commercial preparations had lower molecular masses than the NAs in the tailings waters. The commercial NAs were biodegraded within 14 days, but only about 25% of the NAs native to the tailings waters were removed after 40-49 days. These results show that low molecular mass NAs (C < or =17) are more readily biodegraded than high molecular mass NAs (C > or =18). Moreover, the results indicate that biodegradation studies using commercial NAs alone will not accurately reflect the potential biodegradability of NAs in the oil sands tailings waters.     

Geochemical and strontium isotope characterization of produced waters from Marcellus Shale natural gas extraction

Extraction of natural gas by hydraulic fracturing of the Middle Devonian Marcellus Shale, a major gas-bearing unit in the Appalachian Basin, results in significant quantities of produced water containing high total dissolved solids (TDS). We carried out a strontium (Sr) isotope investigation to determine the utility of Sr isotopes in identifying and quantifying the interaction of Marcellus Formation produced waters with other waters in the Appalachian Basin in the event of an accidental release, and to provide information about the source of the dissolved solids. Strontium isotopic ratios of Marcellus produced waters collected over a geographic range of ~375 km from southwestern to northeastern Pennsylvania define a relatively narrow set of values (ε(Sr)(SW) = +13.8 to +41.6, where ε(Sr) (SW) is the deviation of the (87)Sr/(86)Sr ratio from that of seawater in parts per 10(4)); this isotopic range falls above that of Middle Devonian seawater, and is distinct from most western Pennsylvania acid mine drainage and Upper Devonian Venango Group oil and gas brines. The uniformity of the isotope ratios suggests a basin-wide source of dissolved solids with a component that is more radiogenic than seawater. Mixing models indicate that Sr isotope ratios can be used to sensitively differentiate between Marcellus Formation produced water and other potential sources of TDS into ground or surface waters.     

红外光谱法测定水产品中石油烃残留

目的 建立微波消解前处理结合红外光谱法测定水产品中石油烃残留量的分析方法。方法 试样经微波消解后,用四氯乙烯液-液萃取,萃取液经活化硅酸镁和无水硫酸钠去除干扰后,氮气吹至近干,四氯乙烯定容,经红外光谱检测,记录2930 cm-1、2960 cm-1、3030 cm-1处的吸光度值,计算出石油烃在生物体内的含量。结果 石油烃质量浓度在0.4~100 mg/L范围内呈良好的线性关系（R2＞0.998）,当使用含水率6%活化度的硅酸镁,填充高度为60 mm时为最佳吸附条件,在此条件下测试的方法检出限（limit of detection,LOD）为0.18 mg/kg,定量限（limit of quantitation,LOQ）为0.57 mg/kg,精密度（relative standard deviations, RSDs）在1.99%～6.36%之间,加标回收率在91.5%～110.5%之间（n=5）。结论 该方法具有检测范围宽、稳定性好、准确度高的优点,能满足水产品中石油烃残留量检测需要。