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991.
Mayra Avelar Blanca Bonilla-Heredia Martín Merino-Ibarra Jorge A. Herrera-Silveira Javier Ramirez Humberto Rosas Job Valdespino Juan P. Carricart-Ganivet Ana Martínez 《Environmental monitoring and assessment》2013,185(9):7591-7603
The management of protected areas in karstic regions is a challenge because flooded cave systems form there and provide underground hydrological conducts that may link different zones. As a consequence, affectations to the protected areas can possibly occur as a consequence of human activities in remote areas and may therefore pass undetected. Thus, the monitoring of possible contaminants in these regions is becoming imperative. In this work, we analyze the concentration of essential (iron) and non-essential metals (cadmium and chromium) in the seagrass Thalassia testudinum that grows in Yalahau Lagoon, located in a near-to-pristine protected area of the Yucatán Peninsula, close to the rapidly developing touristic belt of the Mexican Caribbean. Salinity and silicate patterns show that Yalahau is an evaporation lagoon, where groundwater discharge is important. High iron (>400 μg/g), cadmium (>4 μg/g), and chromium (≈1 μg/g) concentrations were found in the area of highest groundwater input of the lagoon. High levels (5.1 μg/g) were also found near the town dump. In the rest of the sampling sites, metal concentrations remained near to background levels as estimated from other works. Temporal changes of concentrations in the seagrass tissues show also a local input and an input from the groundwater that could provoke an environmental problem in the Yalahau Lagoon in the near future. 相似文献
992.
M. Z. Chaudhary N. Ahmad A. Mashiatullah N. Ahmad A. Ghaffar 《Environmental monitoring and assessment》2013,185(8):6677-6691
Sediment core from Korangi Creek, one of the polluted coastal locations along the Karachi Coast Pakistan, was collected to trace the history of marine pollution and to determine the impact of industrial activity in the area. Down core variation of metals such as Ca, K, Mg, Al, S, Ti, V, Cr, Mn, Fe, Ni, Cu and Zn was studied in the 72.0 cm core. Nuclear analytical techniques, proton induced X-rays emission (PIXE), was employed to ascertain the chemical composition in sediment core. Grain size analysis and sediment composition of cored samples indicated that Korangi creek sediments are clayey in nature. Correlation matrix revealed a strong association of Ni, Cu, Cr and Zn with Fe and Mn. To infer anthropogenic input, enrichment factor (EF), degree of contamination and pollution load index were calculated. EF showed severe enrichment in surface sediment for Ni, Cu, Cr and Zn, indicating increased industrial effluents discharge in recent years. The study suggests that heavy metal discharge in the area should be regulated. If the present trend of enrichment is allowed to continue unabated, it is most likely that the local food web complexes in the creek might be at highest risk. 相似文献
993.
R. Maurício C. J. Dias N. Jubilado F. Santana 《Environmental monitoring and assessment》2013,185(10):8125-8133
In this report, the development of an online, noninvasive, measurement method of the biofilm thickness in a liquid phase is presented. The method is based in the analysis of the ultrasound wave pulse-echo behavior in a liquid phase reproducing the real reactor conditions. It does not imply the removal of the biomass from the support or any kind of intervention in the support (pipes) to detect and perform the measurements (non-invasiveness). The developed method allows for its sensor to be easily and quickly mounted and unmounted in any location along a pipe or reactor wall. Finally, this method is an important innovation because it allows the thickness measurement of a biofilm, in liquid phase conditions that can be used in monitoring programs, to help in scheduling cleaning actions to remove the unwanted biofilm, in several application areas, namely in potable water supply pipes. 相似文献
994.
Sónia R. Q. Serra Ana Raquel Calapez Amaia Pérez-Bilbao Maria João Feio 《Environmental monitoring and assessment》2015,187(1):1-13
Bioassessment tools should distinguish between the effects of anthropogenic degradation in communities and natural temporal changes. The present study tests the influence of natural seasonal variability on macroinvertebrate stream communities assessed by a predictive model (PORTRIV) and a multimetric index (IPtI) calibrated for spring. The scores of PORTRIV decreased significantly between spring and autumn, and between spring and winter (ca. 37 to 53 %, respectively), while those of IPtI did not change significantly between seasons. For non-reference samples, the results of the predictive model also indicate no significant differences. A correction factor (CF) was calculated to adjust the existing differences in the model assessments between seasons, based on the percentage of variation of reference site scores from spring to autumn and winter. After the application of the CF to the OE50 scores of spring reference samples, the differences were no longer significant. Independent reference validation sites confirmed this tendency. This method has the advantage of avoiding large efforts required for the construction of databases from other seasons and the development of new models to allow the assessment of streams in seasons other than spring. Further tests with models developed in regions with more marked seasonal changes should be done to confirm its wider applicability. 相似文献
995.
Montes AM González-Farias FA Botello AV 《Environmental monitoring and assessment》2012,184(3):1359-1369
The lagoon system of Navachiste-Macapule is located in northern Mexico, in the state of Sinaloa, with an area of 24,000 ha.
The main economic activity in the area is agriculture, and the lagoon lies next to the irrigation district ID-063 which covers
116,615 ha. The purpose of this study is to evaluate the levels of pollution generated by organochlorine pesticides (OC) in
the surface sediments of the lagoon and in the agricultural drains of the ID-063 that are supposedly transported into the
system as a result of agricultural activities and runoff from adjacent land. For this, between 2006 and 2007, 45 surface sediment
samples were collected (warm dry, rainy and cold dry) from 15 sampling sites, during the three climatic seasons. Of these,
eight were located inside the lagoon in marine conditions (salinity >31 PSU) and seven in the agricultural drains of the ID-063
in freshwater conditions (salinity <5 PSU). The average concentration of the OC in the sediments was 44.75 ng g − 1, among which the group of the alicyclic compounds presented the greatest concentrations. The average value of the total organic
carbon (TOC) in the sediments of the system was 0.90%. The sediments collected inside the lagoon had an average OC concentration
of 18.97 ng g − 1, and the predominant type of sediment was fine to very fine sand. The average OC concentration in the sediments collected
in the agricultural drains was 75.69 ng g − 1, where fine sediments (silt) were predominant. The presence of methoxychlor, endrin and heptachlor suggested that these compounds
were continuously used in the system, even though their use is forbidden in Mexico. 相似文献
996.
de Figueiredo DR Ferreira RV Cerqueira M de Melo TC Pereira MJ Castro BB Correia A 《Environmental monitoring and assessment》2012,184(1):471-485
The information on bacterial community composition (BCC) in Portuguese water bodies is very scarce. Cértima River (central
western Portugal) is known to have high levels of pollution, namely organic. In the present work, the BCC from a set of 16
water samples collected from Cértima River Basin and its main tributaries was characterized using 16S rDNA–denaturing gradient
gel electrophoresis, a culture-independent molecular approach. Molecular data were related to environmental parameters through
multivariate analysis to investigate potential impact of water pollution along the river. Principal component analysis using
environmental data showed a water quality gradient from more pristine waters (at the mountain tributaries) to waters with
increasingly eutrophic potential (such as Fermentelos Lake). This gradient was mainly defined by factors such as organic and
inorganic nutrient sources, electrical conductivity, hydrogen carbonate concentration, and pH. Molecular results showed variations
in BCC along Cértima River Basin but in the main river section, a Bacteroidetes phylotype (Flavobacterium sp.) proved to be dominant throughout the river course. Multivariate analysis suggests that spatial variation of BCC along
the Cértima River Basin depended mainly on parameters such as Chl a, total suspended solid (TSS), total organic carbon, electrical conductivity, and HCO
_boxclose^-_{3}^{-} levels. Bacteroidetes phylotypes were all related to higher electrical conductivity and HCO3-_{3}^{-} levels although some of these were also correlated with high SO42-_{4}^{2-} and others with high soluble reactive phosphorus, nitrate, TN, and Kjeld-N levels. The Gammaproteobacteria occurrence was correlated with high SO42-_{4}^{2-} levels. One of the Betaproteobacteria phylotypes showed to correlate with low redox potential (Eh) and high temperature, pH, TSS, and Chl a levels while another one showed a negative correlation with Chl a values. 相似文献
997.
Fernandes CE Das A Nath BN Faria DG Loka Bharathi PA 《Environmental monitoring and assessment》2012,184(5):2677-2689
We investigated the influence on bacterial community and biochemical variables through mechanical disturbance of sediment-akin
to small-scale mining in Kalbadevi beach, Ratnagiri, a placer-rich beach ecosystem which is a potential mining site. Changes
were investigated by comparing three periods, namely phase I before disturbance, phase II just after disturbance, and phase
III 24 h after disturbance as the bacterial generation time is ≤7 h. Cores from dune, berm, high-, mid-, and low-tide were
examined for changes in distribution of total bacterial abundance, total direct viability (counts under aerobic and anaerobic
conditions), culturability and biochemical parameters up to 40 cm depth. Results showed that bacterial abundance decreased
by an order from 106 cells g − 1 sediment, while, viability reduced marginally. Culturability on different-strength nutrient broth increased by 155% during
phase II. Changes in sedimentary proteins, carbohydrates, and lipids were marked at berm and dune and masked at other levels
by tidal influence. Sedimentary ATP reduced drastically. During phase III, Pearson’s correlation between these variables evolved
from non-significant to significant level. Thus, simulated disturbance had a mixed effect on bacterial and biochemical variables
of the sediments. It had a negative impact on bacterial abundance, viability and ATP but positive impact on culturability.
Viability, culturability, and ATP could act as important indicators reflecting the disturbance in the system at short time
intervals. Culturability, which improved by an order, could perhaps be a fraction that contributes to restoration of the system
at bacterial level. This baseline information about the potential mining site could help in developing rational approach towards
sustainable harnessing of resources with minimum damage to the ecosystem. 相似文献
998.
Assessment of drinking water quality using ICP-MS and microbiological methods in the Bholakpur area,Hyderabad, India 总被引:1,自引:0,他引:1
Abdul RM Mutnuri L Dattatreya PJ Mohan DA 《Environmental monitoring and assessment》2012,184(3):1581-1592
A total of 16 people died and over 500 people were hospitalized due to diarrhoeal illness in the Bholakpur area of Hyderabad,
India on 6th May 2009. A study was conducted with immediate effect to evaluate the quality of municipal tap water of the Bholakpur
locality. The study consists of the determination of physico-chemical properties, trace metals, heavy metals, rare earth elements
and microbiological quality of drinking water. The data showed the variation of the investigated parameters in samples as
follows: pH 7.14 to 8.72, EC 455 to 769 μS/cm, TDS 303.51 to 515.23 ppm and DO 1.01 to 6.83 mg/L which are within WHO guidelines
for drinking water quality. The water samples were analyzed for 27 elements (Li, Be, B, Na, Mg, Al, Si, K, Ca, V, Cr, Mn,
Fe, Ni, Co, Cu, Zn, As, Se, Rb, Sr, Mo, Ag, Cd, Sb, Ba and Pb) using inductively coupled plasma-mass spectrometry (ICP-MS).
The concentrations of Fe (0.12 to 1.13 mg/L), Pb (0.01 to 0.07 mg/L), Cu (0.01 to 0.19 mg/L), Ni (0.01 to 0.15 mg/L), Al (0.16
to 0.49 mg/L), and Na (38.36 to 68.69 mg/L) were obtained, which exceed the permissible limits of the World Health Organization
(WHO) for drinking water quality guidelines. The remaining elements were within the permissible limits. The microbiological
quality of water was tested using standard plate count, membrane filtration technique, thermotolerant coliform (TTC), and
most probable number (MPN) methods. The total heterotrophic bacteria ranged from 1.0 × 105 to 18 × 107 cfu/ml. Total viable bacteria in all the water samples were found to be too numerable to count and total number of coliform
bacteria in all water samples were found to be of order of 1,100 to >2,400 MPN index/100 ml. TTC tested positive for coliform
bacteria at 44.2°C. All the water samples of the study area exceeded the permissible counts of WHO and that (zero and minimal
counts) of the control site (National Geophysical Research Institute) water samples. Excessively high colony numbers indicate
that the water is highly contaminated with microorganisms and is hazardous for drinking purposes. Bacteriological pollution
of drinking water supplies caused diarrhoeal illness in Bholakpur, which is due to the infiltration of contaminated water
(sewage) through cross connection, leakage points, and back siphoning. 相似文献
999.
Maria P. Papadopoulou Emmanouil A. Varouchakis George P. Karatzas 《Environmental Modeling and Assessment》2010,15(5):319-328
Karst aquifers are characterized by spatial heterogeneity due to the presence of highly permeable channels and conduits in
low-permeable fractured rocks (matrix block). Recent studies have reported a close relationship between surface and subsurface
water in karstic regions due to the water flow through a complicated network of paths formed by fracture intersections. Subsurface
flow in karstified aquifers ranges between conduit flow, in large passages with relatively high flow velocities, and diffuse
flow, in the matrix block where Darcy’s law is still valid. In this paper, we present the simulation of a complex karstified
aquifer system in Crete, Greece, where the presence of main faults drastically affects the regional flow. A discrete fracture
approach in conjunction with an equivalent porous medium approach was adopted to simulate the mixed flow in the area of interest.
The simulation results have shown that the length and the orientation of the dominant faults, primarily during the rainy season,
affect the flow field. 相似文献
1000.
In the event of a natural or anthropogenic disturbance, environmental resource managers require a reliable tool to quickly
assess the spatial extent of potential damage to the seagrass resource. The temporal availability of the Landsat 5 Thematic
Mapper (TM) imagery provided a suitable option to detect and assess damage of the submerged aquatic vegetation (SAV). This
study examined Landsat TM imagery classification techniques to create two-class (SAV presence/absence) and three-class (SAV
estimated coverage) SAV maps of the seagrass resource. The Mahalanobis Distance method achieved the highest overall accuracy
(86%) and validation accuracy (68%) for delineating the seagrass resource (two-class SAV map). The Maximum Likelihood method
achieved the highest overall accuracy (74%) and validation accuracy (70%) for delineating the seagrass resource three-class
SAV map. The Landsat 5 TM imagery classification provided a seagrass resource map product with similar accuracy to the aerial
photointerpretation maps (validation accuracy 71%). The results support the application of remote sensing methods to analyze
the spatial extent of the seagrass resource. 相似文献