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51.
Kusum Komal Karati G. Vineetha N. V. Madhu P. Anil M. Dayana B. K. Shihab A. I. Muhsin C. Riyas T. V. Raveendran 《Environmental monitoring and assessment》2017,189(12):653
El Niño, an interannual climate event characterized by elevated oceanic temperature, is a prime threat for coral reef ecosystems worldwide, owing to their thermal threshold sensitivity. Phytoplankton plays a crucial role in the sustenance of reef trophodynamics. The cell size of the phytoplankton forms the “master morphological trait” with implications for growth, resource acquisition, and adaptability to nutrients. In the context of a strong El Niño prediction for 2015–2016, the present study was undertaken to evaluate the variations in the size-structured phytoplankton of Kavaratti reef waters, a major coral atoll along the southeast coast of India. The present study witnessed a remarkable change in the physicochemical environment of the reef water and massive coral bleaching with the progression of El Niño 2015–2016 from its peak to waning phase. The fluctuations observed in sea surface temperature, pH, and nutrient concentration of the reef water with the El Niño progression resulted in a remarkable shift in phytoplankton size structure, abundance, and community composition of the reef waters. Though low nutrient concentration of the waning phase resulted in lower phytoplankton biomass and abundance, the diazotroph Trichodesmium erythraeum predominated the reef waters, owing to its capability of the atmospheric nitrogen fixation and dissolved organic phosphate utilization. 相似文献
52.
This study develops a depth-averaged two-dimensional (2D) numerical model using a finite difference method (FDM) on a staggered grid. The governing equations were solved using the Marker and Cell method that was developed at the Los Alamos laboratories by Harlow and Welch in 1965. In the paper, an explicit FDM was used to solve the governing equations. A first-order approximation was used for the temporal derivative. Second-order central difference approximations were used for space discretization. The time step is limited by the Courant–Friedrichs–Lewy (CFL) condition. The time step used in this study depends on the grid spacing and velocity components in the x- and y-directions. The study is divided into two steps: the first step is to develop a depth-averaged 2D numerical model to simulate the flow process. The second constructs a module to calculate the bed load transport and simulate the river morphology in the areas that have steep slopes, torrents, and mountain rivers. Developed model was applied to the artificial channel and a flood event in the Asungjun River section of the mountainous Yangyang Namdae River (South Korea). General simulation results showed that the developed model was in good agreement with the observed data. 相似文献
53.
Manuela Carneiro Bruno Colaço Ricardo Brandão Carla Ferreira Nuno Santos Vanessa Soeiro Aura Colaço Maria João Pires Paula A. Oliveira Santiago Lavín 《Environmental monitoring and assessment》2014,186(11):7011-7021
The accumulation of heavy metals in the environment may have a wide range of health effects on animals and humans. Thus, in this study, the concentrations of arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) in the blood and tissues (liver and kidney) of Portuguese common buzzards (Buteo buteo) were determined by inductively coupled plasma-mass spectrometer (ICP-MS) in order to monitor environmental pollution to these elements. In general, Hg and As were the elements which appeared in the highest and lowest concentrations, respectively. A highest percentage of non-detected concentration was found for blood Cd (94.6 %) but, in turn, it was the only metal that was detected in all kidney samples. The kidney was the analyzed sample which showed the highest concentrations of each element evaluated. Statistically, significant differences among blood, liver, and kidney samples were observed for As and Cd (P?0.05). Cd concentrations in kidney and liver varied significantly with age: Adults showed higher hepatic and renal Cd concentrations than juveniles. Blood Pb concentration seems to show an association with the hunting season. Although raptors are at the top of the food chain and are thus potentially exposed to any biomagnification processes that may occur in a food web, the individuals evaluated in this study generally had low levels of heavy metals in blood and tissues. However, chronic exposure to these metals was verified. The results presented here lend weight to arguments in favor of continuous biomonitoring of metals and metalloids, since heavy metals may accumulate to levels that will pose a risk to both human health and the environment. 相似文献
54.
The main objective of this work was to assess the potential use of goose barnacle Pollicipes pollicipes as biomonitor of metal contamination in northwest (NW) coast of Portugal. The concentrations of Cd, Cr, Cu, Fe, Mn, Ni and Zn were determined in coastal seawaters and tissues of P. pollicipes, which allowed establishing correlations between metals in coastal seawaters and P. pollicipes and calculating metal bioaccumulation factors (BAFs). The results of this study showed that P. pollicipes soft tissues can be used for monitoring metal contamination in these coastal seawaters: (1) there were significant correlations (p?0.05) between metals in soft tissues and their concentrations in seawaters, except for Zn (p?>?0.05); (2) soft tissues were sensitive to spatial variations of metal bioavailabilities and their concentrations ranged 0.70-2.22?mg?Cd?kg(-1), 0.49-1.40?mg?Cr?kg(-1), 1.37-2.07?mg?Ni?kg(-1), 2.4-3.3?mg?Cu?kg(-1), 5-59?mg?Mn?kg(-1), 134-578?mg?Fe?kg(-1)and 728-1,854?mg?Zn?kg(-1); (3) mean logarithmic bioaccumulation factors (log BAF) of Fe, Cd and Zn were higher, 5.57, 5.47 and 4.41, respectively, than mean log BAFs of Cr, Mn, Cu and Ni, 4.18, 4.14, 3.98 and 3.51, respectively. In contrary, P. pollicipes shell plates were not considered ideal material to monitor metal bioavailabilities in these coastal seawaters. Regarding the very high concentrations of Zn obtained in the coastal seawaters and P. pollicipes soft tissues, the NW coast of Portugal should be classified as "Class III/IV - Remarkably/Highly Polluted". 相似文献
55.
Fish scales as indicators of wastewater toxicity from an international water channel Tung Dhab drain
The effect of wastewater exposure on scales and chromatophores of freshwater fish Channa punctatus was studied using wastewater dilutions (60–100%) from an international water channel Tung Dhab drain at an interval of 15
and 30 days. The exposed fish showed significant alterations such as uprooted and damaged lepidonts and dispersal of chromatophores.
These observations strongly suggest that fish scales can be successfully employed as indicators of wastewater pollution. 相似文献
56.
In 1998, the Agrio and Guadiamar rivers underwent an enormous environmental disaster caused by the rupture of the Aznalcóllar
tailings dam and the release of 6 hm3 of pyrite sludge and acidic water. Both rivers run over recent alluvial materials which form a small-sized aquifer which
is however important because underground water feeds the flow of the rivers. This work analyzes the state of groundwater 10 years
after the spill. Before the dam failure, this aquifer was already contaminated in the zone nearest to the mine, to which the
impact of the spill was added. Contamination levels in the alluvial aquifer of the Agrio River have decreased remarkably.
However, they are still important, with acidic pH values and high concentrations of toxic elements (maximum values of 16 mg/L
of Zn and 15 mg/L of Al). There are also important levels of contamination in the Guadiamar alluvial area closest to the mine,
as well as in specific zones located further south. The concentration of toxic elements is mainly controlled by pH. The evolution
of contaminant levels show a sharp decrease after the first years following the spill, followed by a subsequent stabilization.
It is necessary to take measures for the recovery of the aquifer because, otherwise, groundwater will continue contributing
contaminants into the Agrio and Guadiamar rivers. 相似文献
57.
Ghumman AR Ahmad MM Hashmi HN Kamal MA 《Environmental monitoring and assessment》2012,184(5):3153-3163
Hill torrents cause a lot of environmental and property damage in Pakistan every year. Proper assessment of direct runoff in the form of hill torrents is essential for protection of environment, property, and human life. In this paper, direct surface runoff hydrograph (DSRH) was derived for a large catchment using the geomorphologic instantaneous unit hydrograph concept. The catchment with hill torrent flows in semi-arid region of Pakistan was selected for this study. It was divided into series of linear cascades and hydrologic parameters required for Nash's conceptual model, and were estimated using geomorphology of the basin. Geomorphologic parameters were derived from satellite images of the basin and ERDAS and ArcGIS were used for data processing. Computer program was developed to systematically estimate the dynamic velocity, its related parameters by optimization and thereby to simulate the DSRH. The data regarding rainfall-runoff and satellite images were collected from Punjab Irrigation and Power Department, Pakistan. Model calibration and validation was made for 15 rainfall-runoff events. Ten events were used for calibration and five for validation. Model efficiency was found to be more than 90% and root mean square error to be about 5%. Impact of variation in model parameters (shape parameter and storage coefficient) on DSRH was investigated. For shape parameter, the number of linear cascades varied from 1 to 3 and it was found that the shaper parameter value of 3 produced the best DSRH. Various values of storage coefficient were used and it was observed that the value determined from geomorphology and the dynamic velocity produced the best results. 相似文献
58.
The Environmental Protection Agency (EPA) has made available on the worldwide web a systematic stream stressor identification
procedure, the “Causal Analysis/Diagnosis Decision Information System” or CADDIS. We report here the results of a survey of
regulators and scientists in 11 states who use CADDIS or another stressor identification procedure in their work. The 13 survey
questions address guidelines as to what impairment scenarios to approach with stressor identification, what information is
needed to perform stressor identification, and what the stakeholder role is in performing stressor identification. At the
time of this survey (the summer of 2009), the EPA CADDIS website was less commonly used among the state regulators surveyed
than the published EPA stressor identification document on which it is based. The respondents generally find the EPA stressor
identification procedure useful and capable of being adapted to their individual needs. Survey respondents all use stressor
identification in their Total Maximum Daily Load work, but also in a wide variety of other applications. All the “types of
evidence” included in the CADDIS stressor identification procedure are used by the practitioners surveyed with the exception
of the results of ecological simulation models. While the CADDIS documentation encourages the involvement of stakeholders
in stressor identification, most respondents do not assemble stakeholder teams of local officials and citizens to participate
in stressor analyses. 相似文献
59.
60.
Maria das Graças Lins Brandão Gustavo Pereira Cosenza Flávia Liparini Pereira Ariela Silva Vasconcelos Christopher William Fagg 《Environmental monitoring and assessment》2013,185(8):7013-7023
Plants continue to be an important source of new bioactive substances. Brazil is one of the world’s mega-diverse countries, with 20 % of the world’s flora. However, the accelerated destruction of botanically rich ecosystems has contributed to a gradual loss of native medicinal species. In previous study, we have observed a fast and intensive change in trade of medicinal plants in an area of Amazon, where human occupation took place. In this study, we surveyed 15 public markets in different parts of Brazil in search of samples of 40 plants used in traditional medicine and present in first edition of Brazilian Official Pharmacopoeia (FBRAS), published in 1926. Samples of plants commercialized as the same vernacular name as in Pharmacopoeia were acquired and submitted to analysis for authentication. A total of 252 plant samples were purchased, but the laboratory analyses showed that only one-half of the samples (126, 50.2 %) were confirmed as the same plant species so named in FBRAS. The high number of unauthenticated samples demonstrates a loss of knowledge of the original native species. The proximity of the market from areas in which the plant occurs does not guarantee that trade of false samples occurs. The impact of the commerce of the substitute species on their conservation and in public health is worrying. Strategies are necessary to promote the better use and conservation of this rich heritage offered by Brazilian biodiversity. 相似文献