Photo-oxidative behaviour of crude oils relative to sea pollution: Part I. Comparative study of various crude oils and model systems

The photo-oxidation of three crude oils from Algeria, the Middle East and Venezuela, respectively, is studied under conditions simulating natural ageing (λ > 300 nm, temperatures between 16 and 38°C) of oil films on the sea surface. The kinetic behaviour differs noticeably from one to another; this could be essentially due to the presence or absence of sulphur compounds. Powerful photosensitizers or photophysical stabilizers have no influence on the course of oxidation, whereas a radical trap (hindered amine) lowers the reaction rate noticeably. The study of model systems such as distillates or a synthetic mixture show the importance of polynuclear aromatics in photo-initiation and of alkyl branched aromatics in the radical propagation of oxidation chains.     

Sensitivity of three microalgae to crude oils and fuel oils

Four crude oils and five fuel oils have been tested for toxicity with three microalgae—a blue-green, a green and a diatom. The oils were absorbed on filter paper pads and the pads submerged in the growth medium. The crude oils were less inhibitory than equal amounts of fuel oils. Despite initial growth lags, the crude oils allowed growth at 30 μl/20 ml of culture medium (10⁵ cells/ml) while fuel oils were lethal at 10 μl/20 ml. The toxicity patterns of two of the whole fuel oils were different from that seen with their water soluble fractions (WSF); for example, the Baton Rouge fuel oil sample was very toxic to growth of the three test organisms whereas its WSF was relatively innocuous. Photosynthesis of a sensitive organism Chlorella autotrophica, strain 580 (10⁷ cells/ml), was only temporarily depressed by the crude oils (30 μl/20 ml). Four of the fuel oils inhibited photosynthesis, O₂ output decreasing to zero without recovery. When the fuel oils were heated in a stream of helium they were detoxified. Chemical analyses of two of the toxic fuel oils before and after heating were compared with analyses of the Montana sample, a largely non-toxic fuel oil, in an effort to determine what types of compounds might be involved. Classes of aromatic compounds which were not accountable for the toxicity observed here include naphthalene, methylnaphthalenes, dibenzothiophenes, phenanthrenes and compounds with volatilities greater than methylnaphthalenes. Paraffinic and asphaltic fractions of fuel oil were also non-toxic. The accumulated chemical data suggest that the toxicity of whole fuel oils is due to the less water soluble types of compounds in the higher boiling aromatic fraction.     

Differential gene expression in oyster exposed to sewage

In order to investigate the influence of domestic sewage on the gene expression of Pacific oysters Crassostrea gigas, suppression subtractive hybridization (SSH) method was employed. Oysters were sampled at a farming area and, after 10 days of acclimation in the laboratory, were exposed to untreated domestic sewage diluted 33% for 48 h. Gills of male oysters were excised for total RNA extraction. mRNA was purified and the differential gene expression was analyzed by SSH. We obtained 61 cDNA sequences but only 15 were identified, which includes fatty acid binding protein, multidrug resistance protein, omega glutathione S-transferase, cytochrome P450 isoform CYP356A1, among others. The identified genes are associated with different metabolic functions like biotransformation, membrane transport, aerobic metabolism and translational machinery, evidencing the potential toxic effects elicited by these effluents.     

Metal uptake in zebrafish embryo-larvae exposed to metal-contaminated sediments

Heavy metal contamination in coastal and estuarine regions of inner Tolo Harbour, as well as some river and nullah areas, is one of the major water-pollution issues in Hong Kong. Zebrafish (Danio rerio) embryo-larvae was used to study metal uptake from coastal sediments collected from Fo Tan River (industrial area, Sha Tin), Tai Po River (residential area, Tai Po) and Wu Kai Sa (rural area, Tolo Harbour). Exposure experiments (7-days) were carried out using different concentrations (0.1%, 0.5%, 1% and 0% as control) of sediments that were added to aquaria containing fertilized zebrafish eggs until they hatched to become larvae. Uptake of heavy metals (Cd, Cu, Pb and Zn) was determined in whole embryo-larvae following exposure. Significant levels of Cd, Cu, Pb and Zn were detected in the embryo-larvae exposed to sediments from Tai Po River. However, significant levels of only Cd and Cu were found in embryo-larvae exposed to sediments from Fo Tan River.     

Reproductive endocrine function in female atlantic croaker exposed to pollutants

To examine whether xenobiotics impair teleost reproduction by altering reproductive endocrine function, steroid hormone secretion and ovarian growth were investigated in female Atlantic croaker (Micropogonias undulatus) after chronic oral administration with sublethal doses of three classes of reproductive toxins (lead, benzo[a]pyrene and Aroclor 1254). All the sublethal treatments significantly impaired ovarian growth as assessed by the gonadosomatic index. Reduced ovarian growth was accompanied by a significant decline in circulating 17β-estradiol levels in fish exposed to lead and benzo[a]pyrene. All three toxicants significantly decreased plasma testosterone levels. However, the steroidogenic capacity of ovarian tissue in vitro was not altered by xenobiotic exposure. The data suggest that the decreased ovarian growth in croaker after pollutant exposure may be a consequence of the decline in plasma 17β-estradiol levels. Further, this decrease in circulating levels of gonadal steroids does not appear to be caused by a direct effect of the chemicals on ovarian steroid synthesis.     

DNA adducts in mussels and fish exposed to bulky genotoxic compounds

Biological and procedural factors can influence DNA adduct detection in aquatic organisms. Among them, functional structure and metabolic traits represent major biological determinants for adducts formed by lipophilic pro-mutagenic contaminants. In detecting DNA adducts through the 32P-postlabelling assay, efficiency in DNA purification, digestion, labelling, as well as adduct enrichment and quantification may explain differences between independent studies. Reference DNA adducts have been used to verify some 32P-postlabelling aspects. Data obtained for mussels and fish treated with benzo[a]pyrene (B[a]P) and environmentally exposed to genotoxins confirm the above assertions. Although the 32P-postlabelling assay cannot be proposed for routine biomonitoring it appears a reliable and very sensitive index of exposure to genotoxic pollutants in both fish and mollusks.     

Impaired growth in the polychaete Armandia brevis exposed to tributyltin in sediment

Juveniles of the opheliid polychaete, Armandia brevis, were exposed to sediment-associated tributyltin (TBT) for 42 days to evaluate toxicity and bioaccumulation. Growth in this species was inhibited in a dose-response fashion by increasing concentrations of TBT. Even though the biota-sediment accumulation factor (BSAF) for TBT declined for the higher sediment concentrations, the total butyltins in tissue increased over all sediment concentrations. At the highest sediment concentrations, polychaetes bioaccumulated less TBT than expected, which was most likely due to reduced uptake and continued metabolism of the parent compound. The less than expected BSAF values exhibited by animals at the exposure concentrations causing severe effects are an important finding for assessing responses in the field. It appears that severe biological effects can occur in long-term experiments without the expected high tissue concentrations; an observation likely explained by altered toxicokinetics. Analysis of variance determined the lowest observed effect concentration for growth to be 191 ng/g sediment dry wt. for 21 days of exposure and 101 ng/g sediment dry wt. at day 42, indicating that 21 days was insufficient for delineating the steady-state toxicity response. When based on regression analysis, the sediment concentration causing a 25% inhibition in growth at 42 days exposure was 93 ng/g dry wt. (total organic carbon = 0.58%). A dose-response association was also determined for polychaete net weight and TBT in tissue. The tissue residue associated with a 25% reduction in growth was 2834 ng/g dry wt. at day 42. A comparison of these results with previous work indicates that juveniles are approximately three times more sensitive than adults to TBT exposure. The sediment concentrations affecting growth in this species are commonly found in urban waterways indicating potentially severe impacts for this and other sensitive species.     

Disruption of neuroendocrine function in atlantic croaker exposed to Aroclor 1254

To investigate the effects of a polychlorinated biphenyl (PCB) mixture (Aroclor 1254) on reproductive neuroendocrine function, male Atlantic croaker (Micropogonias undulatus) were exposed to the PCB mixture in the diet (0.1 mg/100. g body wt/day) for 30 days during gonadal recrudescence. Concentrations of the monoamines (5-hydroxytryptamine (5-HT), dopamine (DA) and norepinephrine (NE)) and their major metabolites (5-hydroxyindolacetic acid, dihydroxyphenylacetic acid and 3-methoxytyramine) were measured in the preoptic-anterior hypothalamus (POAH) and medial and posterior hypothalamus (MPH) using HPLC with electrochemical detection. There was a significant decline in 5-HT and DA concentrations and an increase in their metabolite to parent amine ratios in both the POAH and MPH of Aroclor 1254-exposed fish. In addition, Aroclor 1254 exposure resulted in the loss of the in vitro gonadotropin (GtH) response to stimulation by a luteinizing hormone-releasing hormone analog (LHRHa). The reduced availability of 5-HT in the nerve terminals may be responsible for the loss of pituitary GtH response to stimulation by LHRHa. These results support the hypothesis that Aroclor 1254-induced alterations in pituitary gonadotropin release may be mediated, at least partially, by altered hypothalamic serotonergic activity.     

Temperature-dependent physiological response of Carcinus maenas exposed to copper

The effect of temperature on the heart rate (fH) of Carcinus maenas exposed to a sublethal nominal concentration (0.5 mg l(-1)) of copper is reported. Adult, intermoult males (4 cm carapace width) were collected from Stavanger Fjord (Norway) in August (seawater TEMPERATURE=17 degrees C) and maintained in the laboratory (fed ad libitum) at 5, 15 and 25 degrees C for 7 days. Following this holding period, crabs were exposed to waterborne copper at the same temperature. After 3 days of exposure, individual fH was measured using the non-invasive Computer Aided Physiological MONitoring system (CAPMON) method. Copper-exposed individuals demonstrated significantly increased fH compared with controls at 5 and 25 degrees C (P<0.01). It is inferred that physiological function in C. maenas may be more vulnerable to copper contamination at seasonal temperature extremes (5 and 25 degrees C) than at the 'standard' test temperature (15 degrees C). Additionally, cardiac arrest observed at 5 degrees C is interpreted as a physiological response to limit copper uptake while the erratic fH in the 25 degrees C group reflected enhanced copper toxicity.     

Metabolic effects and hydrocarbon fate in arctic bivalves exposed to dispersed petroleum

A number of experiments were carried out in the Canadian Arctic on Baffin Island with the purpose of defining the short- and long-term effects of exposure to dispersed crude oil on marine benthic invertebrates. The study reported here assessed metabolic responses by physiological and biochemical indices, and evaluated these in relation to exposure concentration. The overall objective of the study was to evaluate the potential for long-term survival of benthic communities in the Arctic following an oil spill. This objective was consistent with the goals of the larger Baffin Island Oil Spill (BIOS) program, which was implemented to evaluate the relative mitigating effectiveness of chemical dispersants, as compared to conventional oil spill counter-measures.     

Histopathological changes in grass shrimp exposed to chromium, pentachlorophenol and dithiocarbamates

This report deals with the histopathological/ultrastructural changes in various tissues of grass shrimp (Palaemonetes pugio) exposed to hexavalent chromium, pentachlorophenol (PCP) and two dithiocarbamate formulations: Aquatreat DNM-30® (15 % sodium dimethyl dithiocarbamate plus 15 % disodium ethylene bis-dithiocarbamate) and Busan-85® (50 % potassium dimethyl dithiocarbamate). The pathological alterations induced by dithiocarbamates and PCP were most severe and first evident in the gills. Of the biocides tested, the dithiocarbamates caused the most extensive branchial damage—the so-called black gill syndrome, involving early melanization and eventual lamellar truncation. Hexavalent chromium, on the other hand, did not induce marked changes in the gills, but it caused invasive melanized cuticular lesions (particularly at the articulations of the pereiopods, pleopods and abdominal segments). Additionally, chromium caused apparent labyrinth hypoactivity in the antennal glands, whereas the dithiocarbamates seemed to induce labyrinth hyperactivity. Hepatopancreatic histopathology was more severe in shrimp exposed to chromium and PCP than in dithiocarbamate-exposed shrimp. The apparent mitotic activity in the hepatopancreas was increased in Aquatreat-exposed shrimp and suppressed in chromium-exposed shrimp; many mitotic figures in the latter case were abnormal. All four compounds caused varying degrees of midgut epithelial hypertrophy, cytoplasmic vacuolization and diminution of basal tubular endoplasmic reticulum, but only PCP caused widespread rupture of midgut epithelial cell apices. Additional notable ultrastructural anomalies included: mitochondrial compartmentalization in PCP-exposed shrimp; mitochondrial fusion in dithiocarbamate-exposed shrimp; and unusual intranuclear inclusions in different tissues of chromium-exposed shrimp. These pathological changes point to differences in the mechanisms of pollutant toxicity and indicate their potential use in the biological monitoring of aquatic pollutants.     

Comet assays to assess DNA damage and repair in grass shrimp embryos exposed to phototoxicants

Exposure of grass shrimp (Palaemonetes pugio) embryos to four compounds (anthracene, pyrene, alpha-terthienyl, methylene blue) along with solar exposure resulted in extensive DNA strand damage using the comet assay. DNA tail moments of embryos exposed to these chemicals in the dark ranged from 1.8 to 4.3, while exposure to chemicals and solar resulted in tail moments of 14.3-15.3. Reduction of DNA tail moments when solar exposed embryos were transferred to the dark, suggested DNA repair systems were active. The comet assay can be used to follow both DNA damage and repair following exposure to phototoxic chemicals.     

Gradients in coral reef communities exposed to muddy river discharge in Pohnpei,Micronesia

This study analyzed how coral communities change along a gradient of increasing exposure to a mud-discharging river in the Enipein Catchment, Pohnpei, Micronesia. Using video transects, we quantified benthic communities at five sites along a gradient moving away from the river mouth towards the barrier reef. The most river-impacted site was characterized by a high accumulation of mud, low coral cover and low coral diversity. Although coral cover leveled off at ∼400 m from the river mouth to values found at the outer-most sites, coral diversity continued to increase with increasing distance, suggesting that the most distant site was still impacted by the river discharges. Fungiidae, Pavona, Acropora, Pachyseris and Porites rus all significantly increased in cover with distance from the river, while Turbinaria decreased. The combined presence and abundance of these six species groups, together with coral species richness, may help to indicate the effects of terrestrial runoff in similar runoff-exposed settings around Micronesia, whereas coral cover is not a sensitive indicator for river impact. Coral reefs are important resources for the people of Pohnpei. To prevent further degradation of this important resource, an integrated watershed approach is needed to control terrestrial activities.     

海洋环境中混凝土结构服役寿命预测

通过参数定义对Fick定律的不合理假定进行修正,推导氯离子在混凝土中扩散的多因素修正模型,综合考虑氯离子扩散系数的时随效应、混凝土的氯离子结合能力和混凝土自身缺陷的影响.根据对大量数据的分析试算,给出模型中参数的取值.利用该扩散模型,进一步推导海洋环境下基于概率性能的混凝土结构服役寿命计算方法,有效解决混凝土结构服役寿命预测中氯离子扩散系数及混凝土保护层厚度的随机特性.最后给出实际工程算例,说明该预测方法的有效性.     

Differential gene expression in Poecilia vivipara exposed to diesel oil water accommodated fraction

Diesel fuel is a potential contaminant of estuarine and mangrove areas, particularly because it is the main fuel used in small boats and larger vessels. The aim of this work was to identify genes differentially expressed in the liver of Poecilia vivipara (Guppy) exposed to 10% diesel fuel water accommodated fraction (WAF), employing the subtractive suppressive hybridization (SSH) method. The results showed 27 differentially expressed gene fragments, 12 up-regulated and 15 down-regulated. Among the up-regulated genes were CYP1A, UDPGT1a, ABCC4, Methyltransferase and Apolipoprotein A1. Down-regulated genes included Vitellogenins, C1 Inhibitor and Complement Component 3c. The identified genes are associated with different metabolic functions like biotransformation, membrane transport and immune system, indicating the susceptibility and/or molecular responses of this organism to the toxic effects elicited by diesel fuel WSF.     

Antioxidant and pro-oxidant challenge of tannic acid in mussel hemocytes exposed to cadmium

The present study investigates the antioxidant and pro-oxidant behavior of tannic acid (TA) in hemocytes of mussel Mytilus galloprovincialis, in the presence or the absence of cadmium (Cd). TA at concentrations up to 20 μM, primarily found to be no toxic (in terms of cell viability, superoxide anions, nitric oxide and lipid peroxidation products currently estimated), significantly diminished the cytotoxic and oxidative effects induced by the metal (50 and/or 100 μM) in all cases. On the other hand, higher concentrations of TA (40 and 60 μM) were toxic, thus enhancing Cd-mediated cytotoxic and oxidative effects. The present study showed TA beneficiary properties in hemocytes of mussels, at least at low concentrations, while TA at concentrations higher than 20 μM could serve as an excellent oxidized substrate, thus enhancing toxic effects either alone or with the presence of micromolar concentrations of non transition metals, such as Cd.     

Metallothioneins and cytosolic metals in Neomysis integer exposed to cadmium at different salinities

In the present study the induction of metallothioneins (MTs) and its relation to cytosolic metal concentrations (Zn, Cu and Cd) in the euryhaline crustacean Neomysis integer exposed to Cd at different salinities was studied. N. integer was exposed to the same free cadmium ion activity of 5.74 x 10(-9) mol l(-1) (i.e. 1/5 of the 96 h LC(50) value expressed as cadmium activity) in hypo-osmotic (5 psu), isosmotic (16 psu) and hyper-osmotic media (25 psu) for 7 days. In this way, the effect of salinity on cadmium speciation was eliminated and therefore the physiological effect of salinity on Cd accumulation and MT induction could be studied. The accumulation of cytosolic Cd in N. integer changed with salinity from 1.11+/-0.05 micromol l(-1) at 5 psu up to 1.43+/-0.17 micromol l(-1) at 25 psu. This could indicate that the physiological response of euryhaline estuarine invertebrates like N. integer to salinity changes can influence the rate of trace metal uptake from solution. While the salinity changes did not cause significant differences in cytosolic Zn concentrations (mean value of all tested salinities: 34.4+/-2.8 micromol l(-1)), an inverse relationship between salinity and cytosolic Cu concentration was observed. The highest concentration of 15.7+/-2.3 micromol Cul(-1) was determined at 5 psu and the lowest 10.9+/-1.4 micromol Cul(-1) at 25 psu. This could point to a possible relationship between the copper concentration and the hemocyanin metabolism in N. integer. This is the first time that differential pulse voltammetry method was applied to MT assays with N. integer. Although the exposure to Cd resulted in a higher Cd cytosolic concentration, no subsequent MT increase was detected. The significant positive correlation between MT levels and cytosolic Cu concentrations (Spearman correlation coefficient r(s)=0.356, p=0.009) implies a strong relationship between MT and Cu in N. integer.     

Stability of submerged rock berms exposed to motion of liquefied soil in waves

The paper describes the results of an experimental study on the behaviour of a submerged rock berm in liquefied backfill soil. The soil is liquefied by waves, and the rock berm is subject to the orbital motion of the liquefied soil. The soil used in the experiments was silt with d₅₀=0.075 mm. Various berm materials were used, stones of size 0.74-2.5 cm, plastic balls of size 3.6 cm, brass of size 2.5 cm and steel of size 1.0 cm. The experiments show that rock berms that are stable under very large waves can be unstable when they are exposed to the motion of liquefied soil. The limited data obtained in the study were plotted as a function of the mobility number versus the Keulegan-Carpenter number for the range of the Reynolds number of the tests. The critical mobility number corresponding to the incipient motion of the berm stones is determined. Recommendations are made as to how the present findings can be implemented in practice.     

Dynamic analysis of a vertical plate exposed to breaking wave impact

From the experimental studies in recent years, it has become known that when a wave breaks directly on a vertical faced coastal structure, high magnitude impact pressures are produced. The theoretical and experimental studies show that the dynamic response of such structures under wave impact loading is closely dependent on the magnitude and duration of the load history. The dynamic analysis and design of a coastal structure can be succeeded provided the design load history for the wave impact is available. Since these types of data are very scarce, it is much more convenient to follow a method which is based on static analysis for the dynamic design procedure. Therefore, to facilitate the dynamic design of a vertical plate that is exposed to breaking wave impact, a multiplication factor called “dynamic magnification factor” is herein presented which is defined as the ratio of the maximum value of the dynamic response to that found by static analysis. The computational results of the present study show that the dynamic magnification factor is a useful ratio to transfer the results of static analysis to the dynamic design of a coastal plate for the maximum impact pressure conditions of p_max/γH₀≤18.