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排序方式: 共有2399条查询结果,搜索用时 31 毫秒
991.
金鱼藻与铜绿微囊藻共生情况下的化感作用 总被引:17,自引:2,他引:15
研究了金鱼藻(Ceratophfllum demersum)和铜绿微囊藻(Microcystis aeruginosa)共生时二者之间的相互作用.通过追踪测定铜绿微囊藻的藻细胞密度、叶绿素a浓度、藻胆蛋白含量、超氧化物歧化酶(SOD)活性以及丙二醛(MDA)含量,研究了金鱼藻对铜绿微囊藻的化感作用机制,以及铜绿微囊藻对金鱼藻生长的胁迫.结果表明,金鱼藻对铜绿微囊藻有明显的抑制作用,作用96 h后藻细胞完全死亡;排除营养和光的竞争影响,认为抑制作用主要是由化感作用引起的.培养过程中,铜绿微囊藻叶绿索a和藻胆蛋白(包括藻蓝蛋白、别藻蓝蛋白和藻红蛋白)都有不同程度的损伤;作用末期,藻蓝蛋白的损伤程度最大,叶绿素a次之.藻细胞SOD活性以及MDA含量均呈先升高后降低的趋势.铜绿微囊藻对金鱼藻也有一定胁迫作用,使其生长量减少,叶绿素a、类胡萝卜素含量降低. 相似文献
992.
Degradation of chlorpyrifos alone and in combination with chlorothalonil and
their effects on soil microbial populations 总被引:1,自引:0,他引:1
CHU Xiaoqiang FANG Hu PAN Xuedong WANG Xiao SHAN Min FENG Bo YU Yunlong 《环境科学学报(英文版)》2008,20(4):464-469
In practice, pesticides are usually applied simultaneously or one after another for crop protection, and this type of pesticide application often leads to a combined contamination of pesticide residues in the soil environment. A laboratory study was conducted to investigate the influence of chlorothalonil on chlorpyrifos degradation and its effects on soil bacterial, fungal, and actinomycete populations. Under the experimental conditions here, the half-lives of chlorpyrifos alone, and in combination with chlorothalonil, at the recommended and double dosages, were measured to be 3.24, 2.77, and 2.63 d, respectively. Chlorpyrifos degradation was not significantly altered by its combination with chlorothalonil. However, the inhibitory effect of chlorpyrifos on soil microorganisms was increased by its combination with chlorothalonil, and the increase was related to the levels of chlorothalonil added. Compared to those in the controls, the populations of bacteria, fungi, and actinomycetes were significantly reduced by 44.1%, 61.1%, and 72.8%, respectively, on the first day after treatment (DAT) by chlorpyrifos alone. With the addition of chlorothalonil, the inhibition was increased to 55.2%, 79.3%, and 85.8% at the recommended dosage, and 86.0%, 94.1%, and 90.8% at the double dosage, at one DAT, respectively. The results suggested that combined effects should be taken into account to assess the actual impacts of pesticide applications. 相似文献
993.
Organic carbon stratification and size distribution of three typical paddy soils
from Taihu Lake region, China 总被引:6,自引:0,他引:6
PAN Genxing WU Laosheng LI Lianqing ZHANG Xuhui GONG Wei WOOD Yvonne 《环境科学学报(英文版)》2008,20(4):456-463
Developing realistic soil carbon (C) sequestration strategies for China’s sustainable agriculture relies on accurate estimates of the
amount, retention and turnover rates of C stored in paddy soils. Available C estimates to date are predominantly for the tilled and
flood-irrigated surface topsoil (ca. 30 cm). Such estimates cannot be used to extrapolate to soil depths of 100 cm since soil organic
carbon (SOC) generally shows a sharp decrease with depth. In this research, composite soil samples were collected at several depths
to 100 cm from three representative paddy soils in the Taihu Lake region, China. Soil organic carbon distribution in the profiles and in
aggregate-size fractions was determined. Results showed that while SOC decreased exponentially with depth to 100 cm, a substantial
proportion of the total SOC (30%–40%) is stored below the 30 cm depth. In the carbon-enriched paddy topsoils, SOC was found to
accumulate preferentially in the 2–0.25 and 0.25–0.02 mm aggregate size fractions. σ13C analysis of the coarse micro-aggregate fraction
showed that the high degree of C stratification in the paddy topsoil was in agreement with the occurrence of lighter @1313C in the upper
30 cm depth. These results suggest that SOC stratification within profiles varies with di erent pedogenetical types of paddy soils with
regards to clay and iron oxyhydrates distributions. Sand-sized fractions of aggregates in paddy soil systems may play a very important
role in carbon sequestration and turnover, dissimilar to other studied agricultural systems. 相似文献
994.
放射性污染植物修复中超富集植物的数值评价 总被引:4,自引:0,他引:4
目前超富集植物在放射性污染植物修复评价体系中还没有明确的核素富集量限定值,借鉴辐射环境评价方式,明确放射性污染低剂量概念,推算达干预水准时的植物富集系数,结合放射性废物管理规定,计算富集系数应达到的水平,提出了重要核素的超富集植物评价的新的量值概念;建立修复年限模式,讨论了一定生物量和生物富集系数对修复年限的影响。结果表明,根据上述因素导出的各重要核素的超富集植物最低富集系数略有不同,分别是Cs-137:0.70、Sr-90:0.86、Co-60:2.89、Pu-239:0.26、Am-241:0.21、Cm-244:0.12、U-235:0.18、U-238:0.052。良好的超富集植物,其富集系数应再提高一个数量级。 相似文献
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改性玉米秸秆对水中磷酸根的吸附动力学研究 总被引:17,自引:5,他引:12
将化学改性后的玉米秸秆制备阴离子交换剂,重点研究了改性玉米秸秆对磷酸根的吸附动力学特性.通过静态实验,考察了在不同pH、温度、磷酸根初始浓度条件下,改性玉米秸秆对磷酸根吸附效果的影响,并分别用伪一级动力学方程、伪二级动力学方程、修正伪一级动力学方程和颗粒内扩散方程进行拟合,计算出相应的速率常数.结果表明,Langmuir等温模式能更好地描述改性玉米秸秆对磷酸根的吸附效果,并且随着温度的升高,改性玉米秸秆对磷酸根的最大吸附量逐渐减小.改性玉米秸秆对磷酸根的吸附是一个快速吸附过程,30 min内即可达到吸附平衡,该吸附过程符合伪二级动力学方程和颗粒内扩散方程,吸附速率主要受颗粒内扩散控制.随着初始浓度的增大,伪二级吸附速率常数逐渐减小,颗粒内扩散速率常数逐渐增大.通过改性玉米秸秆对磷酸根的吸附动力学研究,可以为反应器的设计和污水处理装置的运行提供基础信息,对于去除水溶液中磷酸根的技术应用具有重要实际意义. 相似文献