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111.
The effect of nitrogen on biomass production, shoot elongation and relative density of the mosses Pleurozium schreberi, Hylocomium splendens and Dicranum polysetum was studied in a chamber experiment. Monocultures were exposed to 10 N levels ranging from 0.02 to 7.35 g N m−2 during a 90-day period. All the growth responses were unimodal, but the species showed differences in the shape parameters of the curves. Hylocomium and Pleurozium achieved optimum biomass production at a lower N level than Dicranum. Pleurozium had the highest biomass production per tissue N concentration. Tolerance to N was the widest in Dicranum, whereas Hylocomium had the narrowest tolerance. Dicranum retained N less efficiently from precipitation than the other two species, which explained its deviating response. All species translocated some N from parent to new shoots. The results emphasize that the individual responses of bryophytes to N should be known when species are used as bioindicators. 相似文献
112.
Sjöström AE Collins CD Smith SR Shaw G 《Environmental pollution (Barking, Essex : 1987)》2008,156(3):1284-1289
Nonylphenol polyethoxylates (NPEOs) are surfactants found ubiquitously in the environment due to widespread industrial and domestic use. Biodegradation of NPEOs produces nonylphenol (NP), an endocrine disruptor. Sewage sludge application introduces NPEOs and NP into soils, potentially leading to accumulation in soils and crops. We examined degradation of NP and nonylphenol-12-ethoxylate (NP12EO) in four soils. NP12EO degraded rapidly (initial half time 0.3-5 days). Concentrations became undetectable within 70-90 days, with a small increase in NP concentrations after 30 days. NP initially degraded quickly (mean half time 11.5 days), but in three soils a recalcitrant fraction of 26-35% remained: the non-degrading fraction may consist of branched isomers, resistant to biodegradation. Uptake of NP by bean plants was also examined. Mean bioconcentration factors for shoots and seeds were 0.71 and 0.58, respectively. Removal of NP from the soil by plant uptake was negligible (0.01-0.02% of initial NP). Root concentrations were substantially higher than shoot and seed concentrations. 相似文献
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116.
硝酸盐浓度及投加方式对反硝化除磷的影响 总被引:29,自引:0,他引:29
采用SBR反应器,详细研究了硝酸盐浓度及其投加方式对反硝化除磷过程的影响。结果表明,缺氧环境下的反硝化吸磷速率与作为电子受体的硝酸盐浓度有很大的关系,硝酸盐浓度越高.吸磷速率越快。当硝酸盐浓度较低.不足以氧化反硝化聚磷菌细胞内的PHB从而导致体系反硝化除磷效率的下降。相同浓度的硝酸盐,采用流加的方式可以获得比一次性投加更高的反硝化吸磷速率。缺氧环境下,反硝化脱氮量与磷的吸收量成良好的线性关系.借助于反硝化聚磷菌,反硝化脱氮与除磷可在一种环境中完成,有效解决了废水中COD不足的问题.同时达到了节省能源和降低污泥产量的目的。 相似文献
117.
The fate of organic chemicals in the soil-plant-atmosphere environment and the governing processes were studied with a coupled dynamic soil transport and plant compartment model. Scenarios with applications of pesticides on sand and loam soils with chemical uptake in barley and wheat were used in the model calculations. Root uptake and concentrations in the plant compartments stem, leave and fruit were calculated for the pesticides terbuthylazine, isoproturon and carbofuran.
The effectivity of uptake from soils with different soil sorption coefficients had been shown for sand and loam soils. The processes degradation in plant and volatilization from leaves to atmosphere are especially effective for carbofuran and terbuthylazine. Although the concentrations in corn at harvest are lower than the maximum allowed concentrations, the peak concentrations in the course of the vegetation period are significantly higher (factor ≤ 200). 相似文献
118.
天然沸石具有较大的孔隙率和比表面积,对氨氮有较强的选择性离子交换能力.运用天然沸石曝气生物滤池处理城市污水厂二级生化出水,结果表明,曝气生物滤池有良好的去除效果.在气水比为3∶1,水力负荷为1 m/h,温度>20℃情况下,沸石曝气生物滤池对城市污水厂二级生化出水COD去除率为12.7%,NH3-N去除率为96.6%;试验系统沿程微生物活性和微生物量呈现逐渐下降趋势,而单位生物量的生物活性沿程分布则与此相反;曝气生物滤池对水中污染物的去除主要集中在底部进水端部分,当水流达到距进水端上方105 cm时,曝气生物滤池对水中NH3-N的去除率已达86.8%(占氨氮总去除率的90%),COD的去除率为13.3%(占COD总去除率的67%). 相似文献
119.
玉米自交系氮效率基因型差异的比较研究 总被引:20,自引:0,他引:20
采用溶液培养的方法。选用经田间,土壤试验对N反应有典型差异的玉米自交系478,H21,Wu312,Zong31,Baici,在4个供氮水平下(0.04,0.4,2和4nmol/L),研究了不同基因型玉米苗期氮素吸收,利用的差异及其原因,结果表明:极低N胁迫条件下(0.04mmol/L),总干重的基因型差异是由根系,地上部的共同作用的结果,高N下,总干重是由地上部的差异所决定的(表1),极低供N条件下,4578的总干重最大,且有较高的氮效率,Wu312,Zong31相对较低,478相对较高的氮效率主要来源于吸收效率的差异。该基因型在低N下总吸氮量最高,H21居中,Baici,Zong31相对较低,478相对较高的氮效率主要来源于吸收效率的差异。该基因型在低N下总吸氮量最高,H21居中,Baici,Zong31,Wu312相对较低(图1),吸收效率的差异主要是由于根系全N量的不同所致(图3),而根系全N量的差异主要是由于根系大小不同(表1),在极低氮水平下,不同基因型玉米根系全氮量的变幅比地上部高出28.1%,高N下(4mmol/L),全N量的变幅比地上部高出15.4%(图2,图3),在0.04mmol/L下,478与Wu312,Zong31的利用效率不存在显著差异(表2)。 相似文献
120.
Acid hydrolysis of estuarine water samples for the determination of amino acids (AAs) was tested and found to be effective
at high (250 μM) nitrate concentrations when the anti-oxidant, ascorbic acid, was added to the samples. Hydrolysable AA concentrations
were then determined in surface sediments collected from low and high salinity regions of the Tamar Estuary (UK) during winter
2003 and 2004, and in overlying water when simulated resuspension of sediment particles was performed. Concentrations of AAs
in sediment samples comprised <50% of particulate nitrogen, fitting the paradigm that most sedimentary nitrogen is preserved
within an organic matrix. When sediment samples were resuspended in overlying water (salinity 17.5), the rapid, measured increase
in dissolved AA concentrations almost equalled the reported nitrate concentration in the lower estuary, with the subsequent
decrease in the total dissolved AA levels suggested that bacterial uptake was occurring. Our data concur with previous studies
on nitrogen desorption from sediments and suggest that an understanding of organic nitrogen cycling will be an important aspect
of future effective estuarine management. 相似文献