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41.
Assessment of spatial variability in some soil properties as related to soil salinity and alkalinity in Bafra plain in northern Turkey 总被引:4,自引:0,他引:4
Cemek B Güler M Kiliç K Demir Y Arslan H 《Environmental monitoring and assessment》2007,124(1-3):223-234
The objectives of this study were to assess the variability in soil properties affecting salinity and alkalinity, and to analyze
spatial distribution patterns of salinity (EC) and alkalinity (ESP) in the plain, which was used irrigation agriculture with
low quality waters. Soil samples were collected from 0–30cm, 30–60cm, 60–90cm and 90–120cm soil depths at 60 sampling sites.
Soil pH had the minimum variability, and hydraulic conductivity (Ks) had the maximum variability at all depths. The mean values
of pH, EC, ESP and Ks increased while the mean values of CEC decreased with soil depth. Values pH, EC and ESP were generally
high in the east and northeastern sides. Soil properties indicated moderate to strong spatial dependence. ESP and pH were
moderately spatially dependent for three of the four depths, EC exhibited moderate spatial dependence for one of the four
depths, CEC had a moderate spatial dependence at all depths, and Ks exhibited a strong spatial dependence. EC, CEC, and ESP
were considerably variable in small distances. The spatial variability in small distances of EC, CEC, pH and ESP generally
increased with depth. All geostatistical range values were greater than 1230m. It was inferred that the strong spatial dependency
of soil properties would be resulted in extrinsic factors such as ground water level, drainage, irrigation systems and microtopography. 相似文献
42.
43.
In this study, we investigated the levels of vitamins A, E, and C in serum and liver, and malondialdehyde (MDA) were followed by long-term administration of some nitrosamines. Sprague-Dawley rats were divided into four groups. N-Nitrosodiethylamine (NDEA), 1-Nitrosopiperidine (NPip), and N-Nitrosopyrrolidine (NPyr) were administered 200 ppb, orally with water for 30 consecutive days to experimental groups. Animals were decapitated at 3rd, 7th, 15th, and 30th days of the administrations. Significant increases were observed in MDA levels treated with nitrosamines at all times. Serum MDA levels were found to be significantly higher in NDEA-treated animals than in control and other groups at 30th day. Liver MDA levels were highly increased in NPyr-treated group. Significant decreases were observed in the levels of vitamins A, E, and C in rats treated with nitrosamines at all times. There were also significantly negative correlations at present changes among the serum or liver MDA levels and vitamin A, E, and C levels in all nitrosamines-treated groups. These findings demonstrate that exposure at low levels of nitrosamines decreased vitamin A, E, and C levels while it attributed lipid peroxidation. Therefore, maintaining an adequate level of antioxidant vitamins in serum and liver may be necessary for the prevention or protection of long-term nitrosamine exposures. 相似文献
44.
Ünal Akkemik Hulya Caner Grace A. Conyers Matthew J. Dillon Nurgül Karlioğlu 《国际发展与全球生态学杂志》2013,20(5):395-405
The Rough Cilicia Archaeological Survey Project investigates landscape transformation as a component to its regional survey of ancient Rough Cilicia (south coastal Turkey opposite Cyprus). Rough Cilicia was celebrated during antiquity for pristine cedar forests that stood between 1500 and 1800 m in altitude along the slopes of the Taurus Mountains. Today along the front range of the Taurus Mountains this forest is completely denuded or otherwise replanted with recent growth in the past 80 years. We employ paleoenvironmental analysis of relic cedar forests in the Taurus Mountains to construct a timeline of anthropogenic disturbances associated with population growth over time and thereby assess the sustainability of ancient forestry practices. To obtain these data, the team recovers pollen and carbon samples from geomorphologic trenches excavated in the cedar zone, tree ring data from dendrochronological survey of the existing forest, and archaeological data from remains of ancient highland settlements. Preliminary results indicate that current perspectives about the timing of deforestation in this region are flawed and that the initial deforestation coincided with regional site abandonment and population decline at the end of antiquity. 相似文献
45.
46.
Sinking rates of natural copepod fecal pellets 总被引:4,自引:0,他引:4
Many pure samples of natural fecal pellets have been collected from mixed small copepods and from the pontellid copepod Anomalocera patersoni in the Ligurian Sea, using a specially designed pellet collection device. Sinking rates of fresh pellets and pellets aged up to 33 days have been determined at 14°C, the mean temperature of the essentially isothermal water column in the Ligurian Sea. Sinking rates of pellets collected during calm sea states increased with increasing pellet volume, but sinking rates of pellets collected during rough sea (Beaufort scale 6) showed little correlation with pellet size. Much of the variability in the sinking rate-pellet size relationships was the result of different pellet composition and compaction, but not pellet age. Pellets produced from laboratory diets of phytoplankton and phytoplankton-sediment mixes showed the expected wide variability in sinking rates, with sediment-ballasted pellets sinking much faster than pellets produced from pure algal diets; thus determination of vertical material fluxes in the sea using laboratory-derived fecal pellet sinking rates is unwarranted. Natural pellet sinking data for small copepods and A. patersoni have been combined with similar data for euphausiids, to yield sinking rates of roughly two orders of magnitude over three orders of magnitude in pellet volume. Pellets from small copepods sank at speeds too slow to be of much consequence to rapid material flux to the deep sea, but they undoubtedly help determine upper water distribution of materials. Recalculation of fecal pellet mass flux estimates from the literature, using our sinking rate data for natural small copepod pellets, yielded estimates about half those of previously published values. Earlier studies had concluded that small fecal pellets were of lesser significance to total material flux than fecal matter; our recalculation strengthens that conclusion. Pellets from large copepods and euphausiids, however, have the capability to transport materials to great depths, and probably do not substantially recycle materials near the surface. The fact that the majority of pellets which had previously been collected in deep traps by other workers were of a size comparable to pellets from our large copepods supports the contention that these larger pellets are the main ones involved in vertical flux. 相似文献
47.
Berberoglu S 《Environmental management》2003,31(3):0442-0451
The objective of this article is to propose a program for the integrated coastal zone management that is required to stimulate
and guide sustainable development of the Mediterranean coastal zone of Turkey.
Improved data collection, quality control, analysis, and data management will provide a firm basis for future scientific understanding
of the East Mediterranean coast of Turkey and will support long-term management. Various innovative procedures were proposed
for a promising ecosystem-based approach to manage coastal wetlands in the Mediterranean: remote data acquisition with new
technologies; environmental quality monitoring program that will provide a baseline for monitoring; linking a Geographic Information
System (GIS) with natural resource management decision routines in the context of operational wetlands, fisheries, tourism
management system; environmental sensitivity analysis to ensure that permitted developments are environmentally sustainable;
and use of natural species to restore the wetlands and coastal dunes and sustain the system processes. The proposed management
scheme will benefit the scientific community in the Mediterranean and the management/planning community in Eastern Turkey. 相似文献
48.
Estimation of total sediment load concentration obtained by experimental study using artificial neural networks 总被引:1,自引:0,他引:1
Estimation of sediment concentration in rivers is very important for water resources projects planning and managements. The
sediment concentration is generally determined from the direct measurement of sediment concentration of river or from sediment
transport equations. Direct measurement is very expensive and cannot be conducted for all river gauge stations. However, sediment
transport equations do not agree with each other and require many detailed data on the flow and sediment characteristics.
The main purpose of the study is to establish an effective model which includes nonlinear relations between dependent (total
sediment load concentration) and independent (bed slope, flow discharge, and sediment particle size) variables. In the present
study, by performing 60 experiments for various independent data, dependent variables were obtained, because of the complexity
of the phenomena, as a soft computing method artificial neural networks (ANNs) which is the powerful tool for input–output
mapping is used. However, ANN model was compared with total sediment transport equations. The results show that ANN model
is found to be significantly superior to total sediment transport equations. 相似文献
49.
Radiotracer experiments were designed to study the effects of certain environmental and biological factors on arsenic accumulation and elimination processes in the Mediterranean mussel Mytilus galloprovincialis. Arsenic (as arsenate) uptake increased with increasing arsenic concentration in the water; however, the response was not proportional, indicating that accumulation was partially suppressed at higher external arsenic concentrations. In general, approximately 80% of the 74As taken up was associated with the soft parts, with small mussels concentrating 74As to a greater degree than larger individuals. The highest 74As concentrations were recorded in the byssus and the digestive gland. Increased temperature enhanced both arsenic uptake and loss. Mussels in sea water at 19 S accumulated approximately three times more 74As than those held at 38 S. Arsenic loss was much less affected by salinity, with only a tendency for greater arsenic retention noted at lower salinities. Studies carried out in the laboratory and in situ revealed that arsenic turnover was significantly more rapid in actively growing individuals living under natural conditions. Arsenic-74 loss from the in situ group was essentially biphasic, with biological half-times of approximately 3 and 32 days for the fast and slow compartments, respectively. The active secretion of arsenic in the byssal threads contributed to the total elimination of the element from the mussels. 相似文献
50.
Siddiqui Shahida Anusha Wu Yuan Seng Saikia Trideep Ucak İlknur Afreen Maliha Shah Mohd Asif Ayivi Raphael D. 《Environmental Chemistry Letters》2023,21(5):2789-2823
Environmental Chemistry Letters - Issues of climate change, energy demand, and natural resources depletion are calling for circular methods to produce value-added products such as biomass, biofuel,... 相似文献