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太湖地区侧渗水稻土稻田磷素动态特征及其潜在环境效应的田间测试结果表明,水稻地上部收获带走的磷量平均为47.5kg·hm-2;土壤表层0—10cm富集的磷、整个稻季径流流失的溶解态磷、颗粒态磷和总磷与施磷量呈线性相关关系。水稻生长季由径流损失的总磷量约在1.3~5.1kg·hm-2,损失量随施磷量的增加而增加。过量施肥会增加磷素径流流失风险,在当地施磷量30kg·hm-2条件下,水田磷素流失量相对很小。太湖地区侧渗水稻土稻季建议施磷量为50kg·hm-2。 相似文献
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Because low concentration of nitrite could be toxic to biological systems and high amounts of nitrite have been observed in a river of northern China since 1990, nitrite from agricultural soil sources should be investigated. In this paper, effects of levels of ammonium-N (NH4+-N), soil pH and nitrification inhibitors on NO2- accumulation, and duration of nitrite in soils were studied. Application of 11.2 mg of nitrapyrin kg(-1) soil or 11.2 mg of sodium azide kg(-1) soil dramatically suppressed nitrite occurrence. Within all incubation times and at all levels of ammonium-N input, we did not detect any measurable NO2-N accumulation in samples of Yellow-brown earth (pH 5.67), but observed huge accumulation in the 2 alkaline soils, Fluvo-aquic loam (pH 7.89) and Fluvo-aquic sand (pH 8.20). The concentrations of nitrite in both alkaline soils were related to ammonium-N levels. The effect of pH on nitrite accumulation was demonstrated by using slurries of Fluvo-aquic sand under continuous aeration and buffers of different pH. Data showed that nitrite concentration increased with the elevated pH, yet that ammonia oxidizers from the original soil (pH 8.2) could adapt to the new medium of low pH (pH 5.35). Dynamic changes of nitrite in soils amended with different rates of nitrite-N were also measured in 6 days. Thereby, we concluded that nitrite was unstable in acid soils, but durable in alkaline soils. The authors suggested that NO2- accumulation in field soils and its subsequent environmental impact should receive more attention. 相似文献
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Fractionation and composition of colloidal and suspended particulate materials in rivers 总被引:7,自引:0,他引:7
The association of pollutants (nutrients, heavy metals and organic compounds) with colloidal and suspended particle matter (SPM) plays a dominant role in determining their transport, fate, biogeochemistry, bioavailability and toxicity in natural waters. A scheme for the fractionation and composition of colloidal and SPM from river waters has been tested. All four separation methods, i.e. sieving, continuous flow centrifugation, tangential flow filtration, sedimentation field-flow fractionation, were for the first time used to separate five size particulate fractions from river. Significant (gram) amounts of colloidal material (<1 microm) in three size ranges, nominally 1-0.2, 0.2-0.006 and 0.006-0.003 microm were obtained. The separation scheme was able to process large samples (100 l), within reasonable times (1 day) and the apparatus was portable. The aquatic colloid size was also characterized with high resolution by using sedimentation field-flow fractionation technique. The mass-based particle size distribution for the water sample showed a broad size distribution between 0.05 and 0.4 microm with the maximum around 0.14 microm. There was a systematic increase in the content of organic carbon (estimated by loss on ignition), Mg, Ca, Na, Cu and Zn with decreasing particle size, highlighting the importance of the colloidal (<1 microm) fraction. It was concluded that the colloidal Cu and Zn concentrations in rivers might be much higher than those reported before. 相似文献
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基于物质流分析基本框架,构建了镁产业生态系统的物质流分析模型,定量分析了2015年我国宏观层次镁金属材料在其生命周期各个阶段的物质流与价值流,并核算了以皮江法工艺炼镁产生的生态包袱,同时结合e!Sankeypro 4.5.3绘图软件进行可视化表达与分析。结果表明:①原镁生产过程中资源消耗量较大,皮江法工艺每生产1t原镁的非生物资源输入量和资源直接输入量分别达到59.3t和16.4t,而生态包袱约为资源直接输入量的3.6倍,物质输入端优化的关键在于提高白云石与燃料的利用效率。② 2006-2015年镁产业生态包袱整体呈现上升趋势,清洁生产与循环经济是新时代镁产业生态化发展的对策。③皮江法炼镁的资源物质投入类别中硅铁与煤的价格居高,影响了价值产出率;废镁潜在利用价值较大。④受国内与国际市场需求的影响,迫切需要调整镁产品生产结构以应对未来发展挑战。最后,从资源利用效率、节能减排、回收利用体系、优化产品结构等方面提出了环境管理措施,以期为我国金属镁等矿产资源的循环利用以及绿色发展提供决策依据。 相似文献
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