Measurements of dissolved methylmercury in natural waters using diffusive gradients in thin film (DGT)

A diffusive gradient in thin films (DGT) technique for measuring methylmercury (MeHg) concentrations in natural waters was developed using 3-mercaptopropyl-functionalized silica gel to preconcentrate the methylmercury. The new resin was characterized and calibrated. Methylmercury is efficiently accumulated at a pH range of 3-9. Basic performance tests of the new DGT device confirmed the applicability of Fick's first law for such DGT measurements. The diffusion coefficient of methylmercury in polyacrylamide gel was 5 x 10(-6) cm(2) s(-1). Methylmercury concentrations determined by DGT deployed for different time periods in the field are statistically not different from results obtained through direct measurements. The DGT technique represents therefore an alternative in situ sampling method for methylmercury. The detection limit of the overall method is 1 pg of MeHg, which correspond to approximately 30 pg L(-1) of MeHg in a water sample, when deploying a typical DGT device for 24 hours. Lower MeHg concentrations are measurable using longer deployment times or thinner diffusive gel layers.     

Estimation of chlorophyll-a concentration using field spectral data: a case study in inland Case-II waters, North China

In the remote sensing of chlorophyll-a (Chla) in inland Case-II waters, the assumption that the optical parameter of Chla specific absorption coefficient a*ph remains constant usually restrains application of many models. In this paper, we presented a newly developed model [Rrs(-1)(lambda1) - Rrs(-1)(lambda2)] x Rrs(lambda3) x a*ph(-1)(lambda1) which was improved on a previous three-band model to isolate interferences from a*ph. In terms of the importance of water optical properties in the model development, spectral and absorption characteristics were analyzed for Shitoukoumen Reservoir and Songhua Lake in Northeast China, as typical examples of inland Case-II waters. Both waters showed overwhelming absorption sum of tripton and chromophoric dissolved organic matter (CDOM) owing to their relatively low Chla contents (1.53 to 19.35 microgl(-1)). According to the optical characteristics of waters studied, optimal positions for lambda (1), lambda (2) and lambda (3) were spectrally tuned to be at 664, 684 and 705 nm, respectively. The model allowed accurate Chla estimation with a determination coefficient (R (2)) close to 0.98 and a root mean square error (RMSE) of 0.87 microgl(-1). Comparison of different models further showed the stability of the improved model, implying its potential use in water color remote sensing. Although the findings underline the rationale behind the improved model, an extensive database containing data in different water conditions and water types is required to generalize its application.     

Effects of marine biofouling on gas sensor membrane materials

The use of underwater gaseous sensors has increased rapidly in the last 10 years. The majority of such sensors employ a thin membrane through which the gas diffuses. These sensors are potentiometric gas-sensing probes and essentially they are ion-selective electrodes. The deployment time of these membranes is curtailed by the formation of biofouling on the membrane leading to erroneous results. The physical properties of a variety of commonly used membranes were investigated using SEM and AFM. This showed that there were differences in topography between the PTFE membranes, such as pore sizes and surface roughness, which may be attributed to the manner in which they are manufactured. The pore size of the PTFE membranes varied greatly, ranging from circular pores with a diameter of 500 nm to elongated pores measuring 1 x 22 microm. The contact angle of each membrane showed that they were all hydrophobic. The amount of fouling on each was also observed and its affect on oxygen diffusion was monitored. Fouling slowed down the response of the instrument and caused reduced diffusion through the membranes. The amount of fouling varied between the membranes with the YSI membrane fouling least. Some of the membranes tested did foul less than others and there could be lifetime advantages of choosing a membrane with a smoother surface and a small pore size.     

SAOZ measurements of NO2 at Aberystwyth

We present in this paper fifteen years' measurements, from March 1991 to September 2005, of stratospheric NO2 vertical columns measured by a SAOZ zenith-sky visible spectrometer. The instrument spent most of its time at Aberystwyth, Wales, with occasional excursions to other locations. The data have been analysed with the WinDOAS analysis program with low-temperature high-resolution NO2 cross-sections and fitting a slit function to each spectrum. Because of a change in detector in May 1998 there is some uncertainty about the relative changes before and after this date, which are partially constrained by the results of an intercomparison exercise. However, the effect of the Mt Pinatubo aerosol cloud is very evident in the data from 1991-94, with a decrease of 10% in NO2 in the summer of 1992 (the SAOZ was located in Lerwick, Scotland during the winter of 1991-92 and observed very low NO2 values but these cannot be directly compared to the Aberystwyth data). To focus more on interannual and long-term variations in NO2, a seasonal variation comprising an annual and semi-annual component was fitted to the morning and evening twilight separately from 1995 to the present. This fit yielded average NO2 columns of 4.08 x 10(15) cm(-2) and 2.68 x 10(15) cm(-2) for the evening and morning twilight, respectively, with a corresponding annual amplitude of +/-2.08 x 10(15) cm(-2) and +/-1.50 x 10(15) cm(-2). Departures from the fitted curve show a trend of 6% per decade, consistent with that reported elsewhere, for the period 1998-2003, but in the past two years a distinct interannual variation of amplitude of approximately 8% has emerged.     

Application of a compact all solid-state laser system to the in situ detection of atmospheric OH,HO2, NO and IO by laser-induced fluorescence

A tuneable, high pulse-repetition-frequency, solid state Nd:YAG pumped titanium sapphire laser capable of generating radiation for the detection of OH, HO2, NO and IO radicals in the atmosphere by laser induced fluorescence (LIF) has been developed. The integration of the laser system operating at 308 nm into a field measurement apparatus for the simultaneous detection of hydroxyl and hydroperoxy radicals is described, with detection limits of 3.1 x 10(5) molecule cm(-3) (0.012 pptv in the boundary layer) and 2.6 x 10(6) molecule cm(-3) (0.09 pptv) achieved for OH and HO2 respectively (30 s signal integration, 30 s background integration, signal-to-noise ratio = 1). The system has been field tested and offers several advantages over copper vapour laser pumped dye laser systems for the detection of atmospheric OH and HO2 radicals by LIF, with benefits of greater tuning range and ease of use coupled with reduced power consumption, instrument footprint and warm-up time. NO has been detected in the atmosphere at approximately 1 ppbv by single photon LIF using the Alpha 2Sigma+ <-- Chi 2Pi1/2 (0,0) transition at 226 nm, with absolute concentrations in good agreement with simultaneous measurements made using a chemiluminescence analyser. With some improvements in performance, particularly with regard to laser power, the theoretical detection limit for NO is projected to be approximately 2 x 10(6) molecule cm(-3) (0.08 pptv). Whilst operating at 445 nm, the laser system has been used to readily detect the IO radical in the laboratory, and although it is difficult to project the sensitivity in the field, an estimate of the detection limit is < 1 x 10(5) molecule cm(-3) (< 0.004 pptv), well below previously measured atmospheric concentrations of IO.     

Depth profiling of Pu, 241Am and 137Cs in soils from southern Belarus measured by ICP-MS and alpha and gamma spectrometry

The depth distribution of plutonium, americium, and 137Cs originating from the 1986 accident at the Chernobyl Nuclear Power Plant (NPP) was investigated in several soil profiles in the vicinity from Belarus. The vertical migration of transuranic elements in soils typical of the 30 km relocation area around Chernobyl NPP was studied using inductively coupled plasma mass spectrometry (ICP-MS), alpha spectrometry, and gamma spectrometry. Transuranic concentrations in upper soil layers ranged from 6 x 10(-12) g g(-1) to 6 x 10(-10) g g(-1) for plutonium and from 1.8 x 10(-13) g g(-1) to 1.6 x 10(-11) g g(-1) for americium. These concentrations correspond to specific activities of (239+240)Pu of 24-2400 Bq kg(-1) and specific activity of 241Am of 23-2000 Bq kg(-1), respectively. Transuranics in turf-podzol soil migrate slowly to the deeper soil layers, thus, 80-95%, of radionuclide inventories were present in the 0-3 cm intervals of turf-podzol soils collected in 1994. In peat-marsh soil migration processes occur more rapidly than in turf-podzol and the maximum concentrations are found beneath the soil surface (down to 3-6 cm). The depth distributions of Pu and Am are essentially identical for a given soil profile. (239+240)Pu/137Cs and 241Am/137Cs activity ratios vary by up to a factor of 5 at some sites while smaller variations in these ratios were observed at a site close to Chernobyl, suggesting that 137Cs is dominantly particle associated close to Chernobyl but volatile species of 137Cs are of relatively greater importance at the distant sites.     

Characterization of Infiltration Rates from Landfills: Supporting Groundwater Modeling Efforts

The purpose of this paper is to review the literature to characterize infiltration rates from landfill liners to support groundwater modeling efforts. The focus of this investigation was on collecting studies that describe the performance of liners 'as installed' or 'as operated'. This document reviews the state of the science and practice on the infiltration rate through compacted clay liner (CCL) for 149 sites and geosynthetic clay liner (GCL) for 1 site. In addition, it reviews the leakage rate through geomembrane (GM) liners and composite liners for 259 sites. For compacted clay liners (CCL), there was limited information on infiltration rates (i.e., only 9 sites reported infiltration rates.), thus, it was difficult to develop a national distribution. The field hydraulic conductivities for natural clay liners range from 1 x 10(-9) cm s(-1) to 1 x 10(-4) cm s(-1), with an average of 6.5 x 10(-8) cm s(-1). There was limited information on geosynthetic clay liner. For composite lined and geomembrane systems, the leak detection system flow rates were utilized. The average monthly flow rate for composite liners ranged from 0-32 lphd for geomembrane and GCL systems to 0 to 1410 lphd for geomembrane and CCL systems. The increased infiltration for the geomembrane and CCL system may be attributed to consolidation water from the clay.     

Determination of irradiated reactor uranium in soil samples in Belarus using 236U as irradiated uranium tracer

This work presents experimental results on the distribution of irradiated reactor uranium from fallout after the accident at Chernobyl Nuclear Power Plant (NPP) in comparison to natural uranium distribution in different soil types. Oxidation processes and vertical migration of irradiated uranium in soils typical of the 30 km relocation area around Chernobyl NPP were studied using 236U as the tracer for irradiated reactor uranium and inductively coupled plasma mass spectrometry as the analytical method for uranium isotope ratio measurements. Measurements of natural uranium yielded significant variations of its concentration in upper soil layers from 2 x 10(-7) g g(-1) to 3.4 x 10(-6) g g(-1). Concentrations of irradiated uranium in the upper 0-10 cm soil layers at the investigated sampling sites varied from 5 x 10(-12) g g(-1) to 2 x 10(-6) g g(-1) depending on the distance from Chernobyl NPP. In the majority of investigated soil profiles 78% to 97% of irradiated "Chernobyl" uranium is still contained in the upper 0-10 cm soil layers. The physical and chemical characteristics of the soil do not have any significant influence on processes of fuel particle destruction. Results obtained using carbonate leaching of 236U confirmed that more than 60% of irradiated "Chernobyl" uranium is still in a tetravalent form, ie. it is included in the fuel matrix (non-oxidized fuel UO2). The average value of the destruction rate of fuel particles determined for the Western radioactive trace (k = 0.030 +/- 0.005 yr(-1)) and for the Northern radioactive trace (k = 0.035 + 0.009 yr(-1)) coincide within experimental errors. Use of leaching of fission products in comparison to leaching of uranium for study of the destruction rate of fuel particles yielded poor coincidence due to the fact that use of fission products does not take into account differences in the chemical properties of fission products and fuel matrix (uranium).     

A highly sensitive spectrophotometric determination of micro amounts of vanadium(V) in environmental and alloy samples by using 3,4-dihydroxybenzaldehydeisonicotinoylhydrazone (3,4-DHBINH)

3, 4-Dihydroxybenzaldehydeisonicotinoylhydrazone was prepared, characterized with spectral analyses and used for developing a new method for the simple, sensitive and rapid spectrophotometric determination of vanadium(V) which gives maximum absorbance at wave length 360 nm. The metal ion gives a yellow colored complex with 3, 4-DHBINH in acetate buffer of pH 5.5 with 1:1 (metal:ligand) composition. The method obeys Beer's law in the range 0.5-5.3 mug mL(-1) of vanadium(V). The molar absorptivity and Sandell's sensitivity were found to be 1.29 x 10(4) L mol(-1) cm(-1) and 0.003949 mug cm(-2) respectively. The correlation co-efficient of the V(V)-3, 4-DHBINH complex was 0.992 which indicated an excellent linearity between the two variables. The repeatability of the method was checked by finding the relative standard deviation (RSD) as 0.424% (n = 5), and its detection limit 0.01677 mug mL(-1) of vanadium(V). The instability constant of the method was calculated by Asmus' method as 4.1666 x 10(-3). The interfering effect of various cations and anions were also studied. The proposed method was successfully applied to the determination of vanadium(V) in environmental samples (water and soil) tobacco leaves and alloy samples. The validity of the method was tested by comparing the results with those obtained using an atomic absorption spectrophotometer.     

Effects of land use on phosphorus loss in the hilly area of the Loess Plateau, China

The hilly area of Loess Plateau has some of the highest soil erosion rates in the world, and serious soil erosion causes great losses of plant nutrients. As the most common land use in Loess Plateau, slope farmland contributed most of the erosion soils. This study was designed to examine the effects of land use and slope angle of farmland on phosphorus (P) loss in the hilly area of loess plateau. Farmland (FR), barrenland (BR), and four forest treantment (seabuckthorn+ poplar (SP), immature seabuckthorn (IS), mature seabuckthorn (MS), immature Chinese pine (ICP)) were the types of land use; 10, 15, 20, 25, 30 degrees were the slope angles of FR that were compared. The results showed a larger proportion of P loss occurred in erosion soil fraction of FR, ICP, ICP, and the five slope treatments of FR; in SP, IS, and MS, P loss was primarily through runoff. FR produced more P loss than SP, IS, ICP, BR, and MS. 20∼30 degrees may be the slope ranges for P loss of FR; FR in this ranges would loss more P with soil erosion. SP, IS, and MS were reasonable land uses for their less runoff, soil loss, and P loss. Farmlands over 15 degrees should be abandoned or reforested for it would produce more runoff, soil loss, and P loss.     

Spatial variability of salinity and alkalinity of a field having salination risk in semi-arid climate in northern Turkey

Spatial variability of salinity and alkalinity is important for site-specific management since they are the most important factors influencing soil quality and agricultural production. The objectives of this study were to analyze spatial variability in salinity and alkalinity and some soil properties affecting salinity and alkalinity, using classical statistics and geostatistical methods, in an irrigated field with low-quality irrigation water diverted from drainage canals. A field of 5 da was divided into 10 m x 10 m grids (5 lines in the east-west direction and 10 lines in the north-south direction). The soil samples were collected from three depths (0-30, 30-60 and 60-90 cm) at each grid corner. The variation coefficients of OM and sand contents were higher than other soil properties. OM had the maximum variability, with a mean of 1.63% at 0-30 cm depth and 0.71% at 30-60 cm depth. Significant correlations occurred between ESP, EC and each of Ca, Mg, K and CaCO(3) contents of the soils (p<0.01). Experimental semivariograms were fitted to spherical and gaussian models. All geostatistical range values were greater than 36 m. The soil properties had spatial variability at small distances at 60-90 cm depth. EC was variable within short distances at 30-60 cm depth. The nugget effect of ESP increased with soil depth. Kriged contour maps revealed that soils had a salinisation and alkalisation tendency at 60-90 cm depth based on spatial variance structure of the EC and ESP values. Spatial variability in EC and ESP can depend on ground water level, quality of irrigation water, and textural differences.     

Dechlorination of pentachlorophenol in supercritical carbon dioxide with zero-valent palladium-magnesium bimetallic mixture

A stream of substrate pentachlorophenol [PCP, 5 mg min(-1) in water-methanol (1 + 4, v/v)] was merged with 1.5 ml min(-1) of supercritical carbon dioxide (scCO2) and delivered to a reactor column (25 cm x 1 cm) of zero-valent palladium-magnesium mixture. The resulting dechlorinations, although very efficient, were not quantitative. For continuous operation at 400 degrees C for 6 h, phenol was the principal product, with lesser quantities of methylated products and only traces of chlorinated products (principally monochlorinated species). PCP deoxygenation was not observed and ring methylation was decreased relative to analogous reactions in hydroxylic organic solvent. With time, the reactor column slowly lost dechlorination activity. Reducing the loading of Pd0 on Mg0 from 2% to 1% (w/w) apparently did not change the course of the reaction; however, the dechlorination capacity was decreased correspondingly. None the less, over 6 h or 5 h of continued operation, the dechlorination efficiency was 0.995 for the 2% (w/w) loading of Pd0 on Mg0 and 0.984 for the 1% (w/w) loading.     

Diffusive uptake in passive and active adsorbent sampling using thermal desorption tubes

Low flow active sampling techniques collecting vapors and gases using thermally desorbable adsorbents are now feasible and desirable in many applications as they permit long integration times, the potential for miniaturized sampling configurations, and other advantages. At very low air flow rates (< 1 ml min(-1)), diffusive uptake on adsorbents in conventional sorbent tubes may equal or exceed the active (pumped) uptake rate, and even at low flow rates (1-4 ml min(-1)), diffusive uptake may significantly bias measurements. Thus, corrections to account for the diffusive flux or means to limit the diffusive uptake are needed in low flow applications. This paper presents (1) a theoretical analysis of the role of diffusive and advective uptake for several sampling geometries of tube-type samplers; (2) experimental confirmation using both laboratory and field studies; (3) estimates of the tortuosity and porosity of the glass wool packing used to retain the adsorbent, parameters needed to estimate diffusive fluxes in passive and active sampling; (4) a demonstration that orifice-equipped low flow active samplers can reduce diffusive uptake and improve precision, and (5) a model predicting the saturated adsorbent layer that helps to account for the gradual decline in uptake rates seen in passive sampling. Diffusive uptake will depend on the tube configuration and diffusion coefficient of the substance of interest, but for conventional sampling tubes (0.4-0.5 cm id, 1.5 cm air gap), sample flow rates should be maintained above 1 to 4 ml min(-1) to keep errors below 5%. Laboratory experiments showed close agreement with theoretical calculations, and the field study using 1 to 4 d sampling periods and 0.3 ml min(-1) flows demonstrated that the orifice-equipped samplers essentially eliminated diffusive uptake. No significant practical difficulties are encountered using orifices, e.g., pressure drop is minimal. Experimental estimates of tortuosity (0.79 +/- 0.02) and porosity (0.92 +/- 0.10) of the glass wool packing (0.3 cm length) represent relatively little resistance to diffusion; however, variation in the packing and adsorbent placement can degrade the precision achievable by passive samplers. Diffusion barriers, consisting most simply of an orifice, may be used to lower the diffusive uptake. A needle-type orifice permits flows below 0.1 ml min(-1) and is suitable for sampling periods as long as several weeks, and it provided greater precision than conventional open-ended sampling tubes (8% compared to 13%). Finally, the gradual decrease in diffusive fluxes often seen in passive sampling is attributed to additional resistance posed by a saturated adsorbent layer, in agreement with a simple model based on total VOCs and specific adsorptivity of the adsorbent.     

The effects of land use changes on some soil properties in İndağı Mountain Pass – Çankırı, Turkey

Understanding spatial variability of dynamic soil attributes provides information for suitably using land and avoiding environmental degradation. In this paper, we examined five neighboring land use types in Indagi Mountain Pass - Cankiri, Turkey to spatially predict variability of the soil organic carbon (SOC), bulk density (BD), textural composition, and soil reaction (pH) as affected by land use changes. Plantation, recreational land, and cropland were the lands converted from the woodland and grassland which were original lands in the study area. Total of 578 disturbed and undisturbed soil samples were taken with irregular intervals from five sites and represented the depths of 0-10 and 10-20 cm. Soil pH and BD had the lower coefficient of variations (CV) while SOC had the highest value for topsoil. Clay content showed greater CV than silt and sand contents. The geostatistics indicated that the soil properties examined were spatially dependent to the different degrees and interpolations using kriging showed the dynamic relationships between soil properties and land use types. The topsoil spatial distribution of SOC highly reflected the changes in the land use types, and kriging anticipated significant decreases of SOC in the recreational land and cropland. Accordingly, BD varied depending on the land use types, and also, the topsoil spatial distribution of BD differed significantly from that of the subsoil. Generally, BD greatly decreased in places where the SOC was relatively higher except in the grassland where overgrazing was the more important factor than SOC to determine BD. The topsoil spatial distributions of clay, silt, and sand contents were rather similar to those of the subsoil. The cropland and grassland were located on the very fine textured soils whereas the woodland and plantation were on the coarse textured soils. Although it was observed a clear pattern for the spatial distributions of the clay and sand changing with land uses, this was not the case for the silt content, which was attributed to the differences of dynamic erosional processes in the area. The spatial distribution of the soil pH agreed with that of the clay content. Soils of the cropland and grassland with higher amounts of clay characteristically binding more cations and having higher buffering capacities had the greater pH values when compared to the soils of other land uses with higher amounts of sand naturally inclined to be washed from the base cations by the rainwater.     

Enhanced uptake of heavy metals in municipal solid waste compost by turfgrass following the application of EDTA

Enhancement of multiple heavy metal uptake from municipal solid waste (MSW) compost by Lolium perenne L. in a field experiment was investigated with application of EDTA. EDTA was added in solution at six rates (0–30 mmol kg^???1) after 50 days of plant growth. Two weeks later, plants were harvested for the first crop and then all the turfgrasses were mowed. After another 30 days of growth, EDTA was added again at above six rates to the corresponding sites and the second crop was harvested 2 weeks later. The results showed that EDTA significantly increased heavy metal accumulation in both crops of L. perenne. For the first crop, the concentrations of Mn, Ni, Cd, and Pb in the shoots increased remarkably with increasing EDTA supply, peaked at 25 mmol kg^???1 EDTA, and shoots of 0–5 cm height (shoots from medium surface to 5 cm height) had higher metal concentrations than 5–10 cm and >10 cm shoots. The highest concentration of Mn, Ni, Cd, and Pb was 2.3-, 2.3-, 2.6-, and 3.2-fold, respectively, in 0–5 cm shoots higher than control. For the second crop, the concentrations of Mn, Cu, and Pb in shoots were, in general, less than those in the first crop. However, the second crop was significantly higher (P?< 0.05) than the first crop in dry biomass, so the total amount of metals removed by the second crop was more than the first crop. In addition, EDTA significantly increased the translocation ratios of most heavy metals from roots to shoots. For the first crop, 38% of the total Zn, 51% of Cd, 49% of Pb, 60% Mn, 55% Ni, and 45% Cu taken up by the plant was translocated in the shoots of 0–5 cm height. Turfgrass would have potential for use in remediation of heavy metals in MSW compost or contaminated soils.     

Analysis of hypoxia in the western interior parts of the Ariake Sea, Japan, using a box model

To clarify the mechanism of hypoxia in the western interior parts of the Ariake Sea (WIAS), field observation data collected in the period of 1972-2004 were analyzed using a two-layer box model. Monthly averages of advection velocity, vertical diffusion coefficient (K(z)), and biochemical oxygen consumption rate (R) in WIAS were evaluated quantitatively during the above period. The estimated advection velocity comparatively corresponded to the observed residual flow pattern of bay head in summer and winter. The estimated K(z) was relatively high (0.6-5.3 cm(2) s(?-1)) from September to March but lower (0.2-0.4 cm(2) s(?-1)) from April to August. The estimated R ranged from 0.30 to 0.46 mg L(?-1) day(?-1) during May to August. In summer, the temporal variation of dissolved oxygen (DO) concentration in the lower layer was controlled largely by K ( z ) and R. Monthly variations of K(z), R, and degree of density stratification (P) in the 1970s, the 1980s, and the 1990s-early 2000s were analyzed. P, K ( z ), and R were not significantly different among the calculated periods (p = 0.93, 0.23, and 0.49). However, the variations of R in summer between the 1970s and the other calculated periods changed. DO consumption period was longer in the 1980s and the 1990s-early 2000s than in the 1970s. R in the 1980s was highest among the calculated periods. The increase in R in the 1980s was caused by the increase in organic matter load originating from red tide phytoplankton due to a decrease in the suspension feeders.     

Risk Analysis of Invasive Species Introduction in the Port of Arzew,by Calculation of Biofouling Surface on Ships’ Hulls

Historically, the biofouling of ships’ hulls has always been considered amongst the oldest mechanisms causing the introduction of marine invasive species. However, in the last few decades, studies have been oriented mainly towards the introduction of non-indigenous species via ballast water, at the expense of biofouling. In this study, an alternative approach that deals with this latter parameter as the main factor of the introduction of marine organisms is proposed. The biofouling surface area of all vessels which have made call at Arzew port in Algeria is calculated over a period of one year (2014). This parameter indicates the importance of the pressure of propagule that corresponds to the successful introduction effort of a species, since it is this submerged surface of the ship that hosts organisms and spreads them all over the world. We associate to each calculated biofouling surface a bioregion of origin, as well as other parameters such as the number of vessels, their maritime routes and the environmental similarity of Arzew port’s seawater and the other different bioregions. We highlight according to the bioregion, the surfaces that constitute a critical risk of the species introduction and those that constitute a minor risk The study showed that over a period of 1 year, 1313 ships from 28 different bioregions that have made call at Arzew port have accumulated a total wet surface corresponding to about nine million square meters. It is worth to mention that this field of research requires special attention from academics as it may lead to more effective methods to prevent future exotic species introductions.     

Capillary microextraction for simultaneous analysis of multi-residual semivolatile organic compounds in water

Capillary microextractor (CME) in combination with a gas chromatograph-mass spectrometer (GC-MS) was employed for the determination of trace priority hazardous substances in water. Three groups of semivolatile organic compounds (SVOCs), i.e., chlorinated hydrocarbons, pesticides and polycyclic aromatic hydrocarbons (PAHs), were simultaneously determined. SVOCs were extracted from 7 mL of water samples on a 100 cm commercial gas chromatographic column (0.32 mm id x film thickness 0.25 microm, HP-5 capillary column) and eluted with only 3 microL of acetonitrile. The extractant was analyzed by GC-MS in the selected ion monitoring mode. The method showed good linearity over the concentration range 10 ng L(-1) to 3.0 mg L(-1) with correlation coefficients (r) greater than 0.99 and low limits of detection ranged from 10 ng L(-1) to 1.0 mg L(-1). High recovery (more than 80%) was obtained with relative standard deviation less than 10%. The method was successfully applied for trace level analyses of SVOCs in water samples.     

Detection of Lead in Vegetables with New Chromogenic Reagent by Spectrophotometry

A new simple, rapid selective and highly sensitive chromogenic reagent dibromo-p-methyl-carboxyazo (DBMCA) was synthesized and studied in detail for the spectrophotometric detection of lead. In 0.25 M phosphoric acid medium, which greatly increases the selectivity, Lead reacts with DBMCA to form a 1:2 blue complex having a sensitivity absorption peak at 646 nm. Under optimal conditions, Beer's Law is obeyed over the range from 0.09 to 0.8 microg mL(-1) Pb (II) and the apparent molar absorptivity is 1.03 x 10(5) mL(-1) cm(-1). The detection limit and the variation coefficient were found to be 2.12 microg mL(-1) and 1.0% respectively. It is found that, except for Ca (II) and Ba (II) all foreign ions studied do not interfere with detection. The interference caused by Ca (II) and Ba (II) can be easily eliminated by prior extraction with potassiumiodide-methylisobutylketone. The proposed method has been applied successfully for to the detection of Lead in vegetable leaves with good results.     

The hygroscopic behaviour of individual aerosol particles in nickel refineries as investigated by environmental scanning electron microscopy

The hygroscopic properties of individual aerosol particles (1-35 microm equivalent projected area diameter) from the Roasting, Anode Casting and Electrorefining Departments of two Ni refineries were studied by environmental scanning electron microscopy (ESEM) and energy-dispersive X-ray microanalysis (EDX) at a relative humidity of 96-98% (at a temperature of 5 degrees C). In the Roasting and Anode Casting Departments, most particles (60-85% by number) showed no visible change in size or surface morphology when exposed to high relative humidity. Approximately 15-30% of the particles developed a thin water film (growth factors between 1.006 and 1.06) indicating the presence of thin surface coatings of sulfates. About 10% of the particles in the Roasting Department formed droplets (growth factors between 1.1 and 2.6) which always contained a large portion of insoluble material. In the Electrorefining Department, most particles (approximately 60%) were residues from the electrolysis bath solution. At a relative humidity of 96-98% these particles formed a solution which contained only small insoluble inclusions. About 30% of the particles in the Electrorefining Department developed thin water films. As only a small fraction of the particles increased substantially in size when exposed to high relative humidity, the deposition pattern of the total aerosol mass fraction will not be changed substantially by hygroscopic growth. The frequent occurrence of thin surface coatings of soluble material on insoluble Ni compounds has to be considered for health assessment purposes.