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51.
The interaction effects of different applied ratios of a hydrophilic polymer (Superab A200) (0, 0.2, 0.6% w/w) under various soil salinity levels (initial salinity, 4 and 8 ms/cm) were evaluated on available water content (AWC), biomass, and water use efficiency for corn grown in loamy sand and sandy clay loam soils. The results showed that the highest AWC was measured at the lowest soil salinity. The application of 0.6% w/w of the polymer at the lowest salinity level increased the AWC by 2.2 and 1.2 times greater than those of control in the loamy sand and sandy clay loam soils, respectively. The analysis of variance of data showed that the effect of salinity was significant on biomass and water use efficiency of corn in the loamy sand and sandy clay loam soils. The highest amounts of these traits were measured in soils with the lowest salinity level. Application of polymer at the rate of 0.6% in the loamy sand soil and at the rate of 0.2% in the sandy clay loam soil resulted in the highest aerial and root biomass and water use efficiency for corn. At these polymer rates the amounts of water use efficiency for corn were 2.6 and 1.7 times greater than those of control in the loamy sand and sandy clay loam soils, respectively. Thus, the use of hydrophilic polymer in soils especially in the sandy soils increases soil water holding capacity, yield, and water use efficiency of plant. On the other hand, decreases the negative effect of soil salinity on plant and helps for irrigation projects to succeed in arid and semi‐arid areas. 相似文献
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Native arbuscular mycorrhizal fungi (AMF) from saline areas could be a critical issue for success in recovering areas affected by salinity, either in natural environments or in agricultural lands. Despite its important role, there is little information on the distribution and abundance of the different mycorrhizal associations in saline environments in European Mediterranean areas. In the present study the community of AMF is investigated in the rhizosphere of a representative plant species adapted to saline Mediterranean areas, Asteriscus maritimus. Samples of the rhizosphere of twenty plants were taken from the most arid region in Europe, Cabo de Gata Natural Park, in two different areas: a dune and a salt marsh. A total of 30 AMF species belonging to three classes, five orders, nine families and 13 genera within the phylum Glomeromycota were found from both sites. In the rhizosphere of the salt marsh spore densities were six times higher than in the dunes, although the diversity was similar in both systems. One new AMF species has been described in the dune and four species could not be unequivocally identified, suggesting possible new species. 相似文献
54.
Wataru Nishijima Yoichi Nakano Satoshi Nakai Tetsuji Okuda Tsuyoshi Imai Mitsumasa Okada 《Marine pollution bulletin》2013
We investigated the effects of river floods on the macrobenthic community of the intertidal flat in the Ohta River Estuary, Japan, from 2005 to 2010. Sediment erosion by flood events ranged from about 2–3 cm to 12 cm, and the salinity dropped to 0‰ even during low-intensity flood events. Cluster analysis of the macrobenthic population showed that the community structure was controlled by the physical disturbance, decreased salinity, or both. The opportunistic polychaete Capitella sp. was the most dominant species in all clusters, and populations of the long-lived polychaete Ceratonereis erythraeensis increased in years with stable flow and almost disappeared in years with intense flooding. The bivalve Musculista senhousia was also an important opportunistic species that formed mats in summer of the stable years and influenced the structure of the macrobenthic community. Our results demonstrate the substantial effects of flood events on the macrobenthic community structure. 相似文献
55.
A three dimensional rectangular grid model is applied to resolve the temperature–salinity dynamics of Ruwais, a segment of the UAE coast which is well known as dense water formation zone. The model employs a heat flux module and a turbulence closure scheme that facilitate realistic calculation of temperature–salinity dynamics. A field survey campaign is carried out to support the modeling study, involving measurements of tide, currents, temperature, and salinity. Investigation is done for two meteorologically extreme conditions, i.e. summer and winter. The model study showed that the western flux develops an anticlockwise circulation in the study area. The water industrial discharges elevated the temperature and salinity of the water near the southeastern shoreline. This water mass propagated towards north under the influence of gravity. 相似文献
56.
新的2010年海水热力学方程TEOS-10采用1990年国际温标以及考虑世界大洋海水组成空间差异的绝对盐度,与旧的1980年海水状态方程EOS-80相比,具有更高的准确度和更广的适用范围,能够直接计算包括熵、焓、热容量在内的旧方程无法计算的热力学变量,将给海洋学研究带来重要的影响。借助气候态平均数据计算的结果表明,新旧方程计算的密度之差,在全球大多数海域可超过10-2kg/m3。在赤道以北的太平洋和印度洋海域,包括中国东海和南海的深海区域,该差别尤为显著,在精度要求较高的研究中必须予以考虑。新方程对密度计算的这一修正主要归因于其首次提出的绝对盐度,考虑了包括中性溶质在内的所有溶质的作用,弥补了实用盐标的缺陷。新旧方程计算冰点等其他物理量也有相应的修正。应尽快推广应用TEOS-10以及绝对盐度,充分发挥其对海洋学发展的推动作用。 相似文献
57.
The reduction and the smoothened amplitudes of the chloride concentrations since 2000 have resulted in a gradual positive development of the aquatic fauna in the River Werra. In the salinized section of the river increasing species numbers have been determined along the salinity gradient, which shows maximum chloride concentrations of about 2500 mg/l, maximum potash concentrations at approximately 200 mg/l, and magnesia concentrations peaked at 320 mg/l. As an immediate consequence of the reduction in salt concentration the immigration of various caddis fly species into the lower River Werra was observed. The Number of taxa per sample rose from 5 to more than 30 in the lower Werra region. Changes in species-richness could be seen more frequently in river sections where chloride concentrations fluctuated around 1500 mg/l. 相似文献
58.
This work presents results from a nearly two-year monitoring of the hydrologic dynamics of the largest submarine spring system in Florida, Spring Creek Springs. During the summer of 2007 this spring system was observed to have significantly reduced flow due to persistent drought conditions. Our examination of the springs revealed that the salinity of the springs' waters had increased significantly, from 4 in 2004 to 33 in July 2007 with anomalous high radon (222Rn, t1/2=3.8 days) in surface water concentrations indicating substantial saltwater intrusion into the local aquifer. During our investigation from August 2007 to May 2009 we deployed on an almost monthly basis a continuous radon-in-water measurement system and monitored the salinity fluctuations in the discharge area. To evaluate the springs' freshwater flux we developed three different models: two of them are based on water velocity measurements and either salinity or 222Rn in the associated surface waters as groundwater tracers. The third approach used only salinity changes within the spring area. The three models showed good agreement and the results confirmed that the hydrologic regime of the system is strongly correlated to local precipitation and water table fluctuations with higher discharges after major rain events and very low, even reverse flow during prolong droughts. High flow spring conditions were observed twice during our study, in the early spring and mid-late summer of 2008. However the freshwater spring flux during our observation period never reached that reported from a 1970s value of 4.9×106 m3/day. The maximum spring flow was estimated at about 3.0×106 m3/day after heavy precipitation in February-March 2008. As a result of this storm (total of 173 mm) the salinity in the spring area dropped from about 27 to 2 in only two days. The radon-in-water concentrations dramatically increased in parallel, from about 330 Bq/m3 to about 6600 Bq/m3. Such a rapid response suggests a direct connection between the deep and the surficial aquifers. 相似文献
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