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Surface Water Samples (surface + water_sample)
Selected AbstractsPost-wildfire changes in suspended sediment rating curves: Sabino Canyon, ArizonaHYDROLOGICAL PROCESSES, Issue 11 2007Sharon L. E. Desilets Abstract Wildfire has been shown to increase erosion by several orders of magnitude, but knowledge regarding short-term variations in post-fire sediment transport processes has been lacking. We present a detailed analysis of the immediate post-fire sediment dynamics in a semi-arid basin in the southwestern USA based on suspended sediment rating curves. During June and July 2003, the Aspen Fire in the Coronado National Forest of southern Arizona burned an area of 343 km2. Surface water samples were collected in an affected watershed using an event-based sampling strategy. Sediment rating parameters were determined for individual storm events during the first 18 months after the fire. The highest sediment concentrations were observed immediately after the fire. Through the two subsequent monsoon seasons there was a progressive change in rating parameters related to the preferential removal of fine to coarse sediment. During the corresponding winter seasons, there was a lower supply of sediment from the hillslopes, resulting in a time-invariant set of sediment rating parameters. A sediment mass-balance model corroborated the physical interpretations. The temporal variability in the sediment rating parameters demonstrates the importance of storm-based sampling in areas with intense monsoon activity to characterize post-fire sediment transport accurately. In particular, recovery of rating parameters depends on the number of high-intensity rainstorms. These findings can be used to constrain rapid assessment fire-response models for planning mitigation activities. Copyright © 2006 John Wiley & Sons, Ltd. [source] Variability of UVR Effects on Photosynthesis of Summer Phytoplankton Assemblages from a Tropical Coastal Area of the South China Sea,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Kunshan Gao From June to September 2005, we carried out experiments to determine the ultraviolet radiation (UVR) -induced photoinhibition of summer phytoplankton assemblages from a coastal site of the South China Sea. Variability in taxonomic composition was determined throughout the summer, with a peak chlorophyll a (chl a,20 ,g chl a L,1) dominated by the diatom Skeletonema costatum that was detected early in the study period; the rest of the time samples were characterized by monads and flagellates, with low chl a values (1,5 chl a ,g L,1). Surface water samples were placed in quartz tubes, inoculated with radiocarbon and exposed to solar radiation for 2,3 h to determine photosynthetic rates under three quality radiation treatments (i.e. PAB, 280,700 nm; PA, 320,700 nm and P, 400,700 nm) using different filters and under seven levels of ambient irradiance using neutral density screens (PvsE curves). UVR inhibition of samples exposed to maximum irradiance (i.e. at the surface) varied from ,12.2% to 50%, while the daytime-integrated UVR-related photoinhibition in surface seawater varied from ,62% to 7%. The effects of UVR on the photosynthetic parameters PBmax and Ek were also variable, but UV-B accounted for most of the observed variability. During sunny days, photosynthesis of microplankton (>20 ,m) and piconanoplankton (<20 ,m) were significantly inhibited by UVR (mostly by UV-B). However, during cloudy days, while piconanoplankton cells were still inhibited by UVR, microplankton cells used UVR (mostly UV-A) as the source of energy for photosynthesis, resulting in higher carbon fixation in samples exposed to UVR than the ones exposed only to photosynthetically active radiation (PAR). Our results indicate that size structure and cloudiness clearly condition the overall impact of UVR on phytoplankton photosynthesis in this tropical site of South China. In addition, model predictions for this area considering only PAR for primary production might have underestimated carbon fixation due to UVR contribution. [source] Abundance and diversity of heterotrophic bacterial cells assimilating phosphate in the subtropical North Atlantic OceanENVIRONMENTAL MICROBIOLOGY, Issue 10 2010Krista Longnecker Summary Microorganisms play key roles in the cycles of carbon and nutrients in the ocean, and identifying the extent to which specific taxa contribute to these cycles will establish their ecological function. We examined the use of 33P-phosphate to identify heterotrophic bacteria actively involved in the cycling of phosphate, an essential inorganic nutrient. Seawater from the sub-tropical North Atlantic Ocean was incubated with 33P-phosphate and analysed by microautoradiography to determine the proportion and diversity of the bacterial community-assimilating phosphate. Complementary incubations using 3H-leucine and 3H-thymidine were also conducted. We found that a higher proportion of total heterotrophic bacterial cells in surface water samples assimilated phosphate compared with leucine or thymidine. Bacteria from all of the phylogenetic groups we identified by CARD-FISH were able to assimilate phosphate, although the abundances of cells within each group did not scale directly with the number found to assimilate phosphate. Furthermore, a significantly higher proportion of Alphaproteobacteria, Gammaproteobacteria and Cytophaga -like cells assimilated phosphate compared with leucine or thymidine. Our results suggest that a greater proportion of bacterial cells in surface waters are actively participating in the biogeochemical cycling of phosphorus, and possibly other elements, than is currently estimated through the use of 3H-leucine or 3H-thymidine. [source] Agricultural pesticides and selected degradation products in five tidal regions and the main stem of Chesapeake Bay, USAENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2007Laura L. McConnell Abstract Nutrients, sediment, and toxics from water sources and the surrounding airshed are major problems contributing to poor water quality in many regions of the Chesapeake Bay, an important estuary located in the mid-Atlantic region of the United States. During the early spring of 2000, surface water samples were collected for pesticide analysis from 18 stations spanning the Chesapeake Bay. In a separate effort from July to September of 2004, 61 stations within several tidal regions were characterized with respect to 21 pesticides and 11 of their degradation products. Three regions were located on the agricultural Delmarva Peninsula: The Chester, Nanticoke, and Pocomoke Rivers. Two regions were located on the more urban western shore: The Rhode and South Rivers and the Lower Mobjack Bay, including the Back and Poquoson Rivers. In both studies, herbicides and their degradation products were the most frequently detected chemicals. In 2000, atrazine and metolachlor were found at all 18 stations. In 2004, the highest parent herbicide concentrations were found in the upstream region of Chester River. The highest concentration for any analyte in these studies was for the ethane sulfonic acid of metolachlor (MESA) at 2,900 ng/L in the Nanticoke River. The degradation product MESA also had the greatest concentration of any analyte in the Pocomoke River (2,100 ng/L) and in the Chester River (1,200 ng/L). In the agricultural tributaries, herbicide degradation product concentrations were more strongly correlated with salinity than the parent herbicides. In the two nonagricultural watersheds on the western shore, no gradient in herbicide concentrations was observed, indicating the pesticide source to these areas was water from the Bay main stem. [source] Perchlorate assessment of the Nakdong and Yeongsan watersheds, Republic of KoreaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2007Oscar Quiñones Abstract The objective of the present study was to conduct a preliminary assessment for perchlorate in surface water, drinking water, and wastewater treatment plant effluent samples obtained from the Nakdong and Yeongsan watersheds in the Republic of Korea. Samples were analyzed for perchlorate using ion chromatography with suppressed conductivity detection (IC-CD) and/or liquid chromatography with tandem mass spectrometry detection (LC-MS/MS). Method reporting limits were 5.0 ,g/L for IC-CD and 0.05 ,g/L for LC-MS/MS analysis. At perchlorate levels above 5.0 ,g/L, IC-CD and LC-MS/MS provided comparable results. The levels of perchlorate detected in the samples procured from the Yeongsan watershed were <5.0 ,g/L in each case. However, Nakdong watershed samples contained perchlorate at levels up to 60 ,g/L. The highest concentrations of perchlorate were found in surface water samples, although drinking water contained perchlorate at concentrations up to 35 ,g/L. In a subset of samples analyzed by LC-MS/MS, chlorate and bromate also were detected at concentrations ranging from <0.10 to 44 ,g/L and <0.10 to 2.6 ,g/L, respectively. To the best of the authors' knowledge, this is the first perchlorate assessment reported for water sources in the Republic of Korea. [source] Pesticide residues in the aquatic environment of banana plantation areas in the North Atlantic Zone of Costa RicaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2000Luisa E. Castillo Abstract A study of pesticide residues in surface waters and sediments was undertaken in the Suerte River Basin, Costa Rica, that drains into the Tortuguero conservation area. Samples were collected in streams, packing plants, and the Suerte River. The most frequently measured compounds in surface water samples were the fungicides thiabendazole, propiconazole, and imazalil; the nematicides terbufos and cadusafos; and the insecticide chlorpyrifos. At the conservation area, propiconazole was detected in 43% of the samples at concentrations ranging from 0.05 to 1.0 ,g/L. In 25% of the samples collected at this site, a nematicide (cadusafos, carbofuran, or ethoprophos) was detected (0.06,6.2 ,g/L). According to this study, most of the insecticide-nematicides analyzed pose a risk for acute or chronic toxicity to aquatic organisms based on the exposure levels and toxicity values from the literature. Ametryn, imazalil, and thiabendazole also exceeded the calculated chronic risk ratio. The most frequently detected compounds in sediments were thiabendazole, chlorpyrifos, imazalil, and propiconazole. The occurrence was higher in the packing plants and streams. Pesticides in waters and sediments of Tortuguero conservation area could pose a threat to this wetland and an additional stress to the endangered species that inhabit this area. More information is needed regarding the distribution and stability of pesticides in the lagoon system as well as of the effects of mixtures of low levels of pesticides and their degradation products on representative species of the Tortuguero ecosystem. Meanwhile, all measures to reduce the emissions of pesticides from the banana plantations and the packing plants should be taken. [source] Characterization of Aeromonas and Vibrio species isolated from a drinking water reservoirJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2001E.P. Ivanova E.P. IVANOVA, N.V. ZHUKOVA, N.M. GORSHKOVA AND E.L. CHAIKINA. 2001. Aims: To study the phenotypic and chemotaxonomic (i.e. phospholipid and cellular fatty acid composition) characteristics of environmental Aeromonas spp. and Vibrio spp. isolated from a drinking water reservoir near Vladivostok City, and the application of some chemotaxonomic markers for discrimination of the two genera and species. Methods and Results: Presumptive Aeromonas species were dominant in surface water samples (up to 25% of the total number of bacteria recovered). These strains were consistent with respect to the cultural and biochemical properties used to define the species Aeromonas sobria (seven strains) and Aer. popoffii (three strains). Vibrio mimicus (two strains) and Vibrio metschnikovii (one strain) were identified according to phenotypic features and cellular fatty acid composition. Conclusions: Environmental Aer. sobria isolates were atypical in their ability to grow at 42°C, and were haemolytic, proteolytic and cytotoxic. Although it was present in a high proportion in the water samples, atypical Aer. sobria is not an indicator of polluted water. Significance and Impact of the Study: The incidence of Aeromonas in the drinking water reservoirs in the Far East of Russia is reported for the first time. [source] Investigating the presence of pesticide transformation products in water by using liquid chromatography-mass spectrometry with different mass analyzers,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2008Félix Hernández Abstract Many pesticide transformation products (TPs) can reach environmental waters as a consequence of their normally having a higher polarity than their parent pesticides. This makes the development of analytical methodology for reliable identification and subsequent quantification at the sub-microgram per liter levels necessary, as required under current legislation. In this paper we report the photodegradation of several pesticides frequently detected in environmental waters from the Spanish Mediterranean region using the high-resolution and exact-mass capabilities of hybrid quadrupole time-of-flight mass spectrometry (QTOF MS) hyphenated to liquid chromatography (LC). Once the main photodegradation/hydrolysis products formed in aqueous media were identified, analytical methodology for their simultaneous quantification and reliable identification in real water samples was developed using on-line solid-phase extraction (SPE)-LC-tandem MS with a triple-quadrupole (QqQ) analyzer. The methodology was validated in both ground and surface water samples spiked at the limit of quantification (LOQ) and 10 × LOQ levels, i.e. 50 and 500 ng/l, obtaining satisfactory recoveries and precision for all compounds. Subsequent analysis of ground and surface water samples resulted in the detection of a number of TPs higher than parent pesticides. Additionally, several soil-interstitial water samples collected from the unsaturated zone were analyzed to explore the degradation/transformation of some pesticides in the field using experimental plots equipped with lisimeters. Several TPs were found in these samples, with most of them having also been detected in ground and surface water from the same area. This paper illustrates the extraordinary potential of LC-MS(/MS) with QTOF and QqQ analyzers for qualitative/structural and quantitative analysis, respectively, offering analytical chemists one of the most powerful tools available at present to investigate the presence of pesticide TPs in water. Copyright © 2007 John Wiley & Sons, Ltd. [source] Determination of nonsteroidal antiinflammatory drugs in water samples using liquid chromatography coupled with diode-array detector and mass spectrometryJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2005Jolanta Debska Abstract An analytical method for the determination of trace levels of six different nonsteroidal antiinflammatory drugs (NSAIDs) in water samples has been developed and validated. Environmentally relevant pharmaceuticals were chosen according to human consumption in Poland. Final analysis of the target compounds was performed by RP LC,diode-array detection,MS, whereas sample preparation included an SPE step. For this SPE step, a number of packing materials, such as LiChrolut RP-18, calixarene, Strata-X, BAKERBOND Narc-2, BAKERBOND Polar Plus, BAKERBOND styrene divinylbenzene-1, and Discovery DSC-18, were used, and their respective advantages and disadvantages in this study were discussed. The RP-18 phase was found to be the most retentive for all analytes. The detection limits for compounds in surface waters were varied from 0.005 for diflunisal to 0.095 ,g/L for ibuprofen. The average recoveries of NSAIDs from the surface water samples ranged from 80 up to 103%. RSD value is relatively low (from 4% for fenoprofen up to 8% for ibuprofen). The performance of the method was tested with several environmental water samples. [source] WATER QUALITY IN AGRICULTURAL, URBAN, AND MIXED LAND USE WATERSHEDS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2004Chris B. Coulter ABSTRACT: Water quality and nonpoint source (NPS) pollution are important issues in many areas of the world, including the Inner Bluegrass Region of Kentucky where urban development is changing formerly rural watersheds into urban and mixed use watersheds. In watersheds where land use is mixed, the relative contributions of NPS pollution from rural and urban land uses can be difficult to separate. To better understand NPS pollution sources in mixed use watersheds, surface water samples were taken at three sites that varied in land use to examine the effect of land use on water quality. Within the group of three watersheds, one was predominately agriculture (Agricultural), one was predominately urban (Urban), and a third had relatively equal representation of both types of land uses (Mixed). Nitrogen (N), phosphorus (P), total suspended solids (TSS), turbidity, pH, temperature, and streamflow were measured for one year. Comparisons are made among watersheds for concentration and fluxes of water quality parameters. Nitrate and orthophosphate concentrations were found to be significantly higher in the Agricultural watershed. Total suspended solids, turbidity, temperature, and pH, were found to be generally higher in the Urban and Mixed watersheds. No differences were found for streamflow (per unit area), total phosphorus, and ammonium concentrations among watersheds. Fluxes of orthophosphate were greater in the Agricultural watershed that in the Urban watershed while fluxes of TSS were greater in the Mixed watershed when compared to the Agricultural watershed. Fluxes of nitrate, ammonium, and total phosphorus did not vary among watersheds. It is apparent from the data that Agricultural land uses are generally a greater source of nutrients than the Urban land uses while Urban land uses are generally a greater source of suspended sediment. [source] Determination of atrazine, deethylatrazine and simazine in water at parts-per-trillion levels using solid-phase extraction and gas chromatography/ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2003W. T. Ma Methods for trace analysis of atrazine and simazine in water have been developed by using stable-isotope dilution with detection by gas chromatography/mass spectrometry. D5 -Atrazine was used as the internal standard for the determination of atrazine and deethylatrazine, while 13C3 -simazine was used for simazine analysis. Water samples were fortified with known amounts of the internal standards and submitted to solid-phase extraction with a C18 bonded-silica cartridge. A gas chromatograph coupled with an ion-trap mass spectrometer was used to analyze the water sample extracts. Method detection limits were 38 parts-per-trillion (ppt) for atrazine and deethylatrazine and 75 ppt for simazine. The accuracy of the method, represented by relative analytical errors, was less than 15%, and the method precision was less than 5% (relative standard deviation, n,=,9). The method was successfully applied to analyze surface water samples collected from a reservoir and a river at ppt levels. Copyright © 2003 John Wiley & Sons, Ltd. [source] THE IMPACT OF SOLUBLE SALTS ON THE DETERIORATION OF PHARAONIC AND COPTIC WALL PAINTINGS AT AL QURNA, EGYPT: MINERALOGY AND CHEMISTRY*ARCHAEOMETRY, Issue 2 2009A. M. A. MOUSSA The wall paintings of Al Qurna in Egypt were studied by means of XRD and ICP,AES in order to determine their mineralogical and chemical composition, and to evaluate the impact of soluble salts on their deterioration, including the identification of the building materials and pigments used. Soluble salts analysis showed that NaCl is the most common soluble salt in the bedrock, ground water and surface water samples. The building materials are affected by the ground water, while the wall paintings in the area are affected by the Upper Egypt climatic conditions, which were studied in order to detect their role in the deterioration cycle in the area. [source] | ||||||||||||||||