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143.
Nitrate in groundwater: an isotopic multi-tracer approach 总被引:12,自引:0,他引:12
Widory D Kloppmann W Chery L Bonnin J Rochdi H Guinamant JL 《Journal of contaminant hydrology》2004,72(1-4):165-188
In spite of increasing efforts to reduce nitrogen inputs into groundwater from intensive agriculture, nitrate (NO3) remains one of the major pollutants of drinking-water resources worldwide. Determining the source(s) of NO3 contamination in groundwater is an important first step for improving groundwater quality by emission control, and it is with this aim that we investigated the viability of an isotopic multi-tracer approach (delta15N, delta11B, 87Sr/86Sr), in addition to conventional hydrogeologic analysis, in two small catchments of the Arguenon watershed (Brittany, France). The main anthropogenic sources (fertilizer, sewage effluent, and hog, cattle and poultry manure) were first characterized by their specific B, N and Sr isotope signatures, and compared to those observed in the ground- and surface waters. Chemical and isotopic evidence shows that both denitrification and mixing within the watershed have the effect of buffering NO3 contamination in the groundwater. Coupled delta11B, delta15N and 87Sr/86Sr results indicate that a large part of the NO3 contamination in the Arguenon watershed originates from the spreading of animal manure, with hog manure being a major contributor. Point sources, such as sewage effluents, contribute to the NO3 budget of the two watersheds. 相似文献
144.
The effect of K deactivation on V_2O_5/WO_3-TiO_2 and Ce-doped V_2O_5/WO_3-TiO_2 catalysts in the selective catalytic reduction(SCR) of NOxby NH_3 was studied.Ce-doped V_2O_5/WO_3-TiO_2 showed significantly higher resistance to K deactivation than V_2O_5/WO_3-TiO_2.Ce-doped V_2O_5/WO_3-TiO_2 with K/V = 4(molar ratio) showed 90% NOxconversion at 350°C,whereas in this case V_2O_5/WO_3-TiO_2 showed no activity.The fresh and K-poisoned V_2O_5/WO_3-TiO_2 and Ce-doped V_2O_5/WO_3-TiO_2 catalysts were investigated by means of in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS),NH_3-temperature progress decomposition(NH_3-TPD),X-ray photoelectron spectroscopy(XPS) and H2-temperature program reduction(H_2-TPR).The effect of Ce doping on the improving resistance to K of V_2O_5/WO_3-TiO_2 were discussed. 相似文献
145.
新型城市污水脱氮除磷工艺的试验研究与优化设计 总被引:2,自引:2,他引:0
提出了一种改进型A2/O脱氮除磷工艺(MAAO),通过工艺试验和活性污泥2D模型对其进行运行和设计优化.结果表明,系统对COD、TN、NH 4-N和TP的平均去除率分别为85.7%、66.8%、97.35%和78.1%;当COD在300mg/L以上时,脱氮除磷效果均较好,可分别达到70%和90%以上.基于试验结果建立的MMAO工艺数学模型仿真效果良好,可对各单元组合进行优化,校核预测不利工况下的工艺运行效果,实现工艺不同工况下的运行参数优化,较好地实现新工艺的机理性优化设计和运行. MMAO稳定运行出水可达到<城镇污水处理厂污染物排放标准>(GB 18918-2002)一级B标准.由于工艺省去内回流,增加厌氧混合液部分超越提供反硝化碳源,使得运行费用明显降低;系统总停留时间比目前传统的以去除有机污染物为主的生物处理工艺略低,该工艺非常适用于对不具有脱氮除磷功能污水厂的改造. 相似文献
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Releases of phosphate fertilizer industry in the surrounding environment:
Investigation on heavy metals and polonium-210 in soil 总被引:1,自引:1,他引:0
Distribution of Cu,Zn,Pb,Cr,Ni,Mn concentrations and the activity of polonium-210 in the surrounding area of a phosphate fertilizer industry located on the eastern coast of the Mediterranean Sea has been determined.Nineteen sampling sites were distributed around the industrial zone on a surface area of about 100,000 m2.Atomic absorption spectroscopy and Alpha spectroscopy were used to quantify the heavy elements and polonium-210,respectively.Investigation on a particle scale was conducted by TEM and SEM coupled to EDX and X-ray cartography to determine the nature of heavy elements carriers and their distribution.Heavy elements were mainly concentrated inside the particle size fraction 50 μm.Their levels decreased with distance increasing from the industry.According to the reference soil,enrichment factors were about 10,15,32 and 100 times for Zn,Pb,Cu,and Cr,respectively inside the particle size fraction 50 μm on the closest sites to the industry.The main contaminant sources were transport and storage of row materials and the free release of phosphogypsum waste.Heavy elements were entrapped inside agglomerates of sulfates,phosphates and iron oxihydroxides in a di used shape.Polonium-210 with an enrichment factor of about 56,showed the same behavior of the spatial distribution of the trace elements. 相似文献
149.
C.R. Rodríguez Pleguezuelo V.H. Durn Zuazo J.L. Muriel Fernndez F.J. Martín Peinado D. Franco Tarifa 《Agriculture, ecosystems & environment》2009,134(1-2):79-88
On the coast of Granada (SE, Spain), an economically important area for subtropical fruit cultivation, the crops are grown on orchard terraces. Also, high amounts of fertilizers, often excessive, are used in this type of intensive agriculture. However, each year significant fractions of nutrients taken up by the trees return to the soil by fallen leaves. Using a litter-bag technique, we assessed the decomposition rates and N-release in various types of litter. Our main purpose was to compare two different agroecosystem scenarios: (1) an unaltered slope consisting mainly of a mixture of herbaceous plants (Papaver rhoeas, Convolvulus sp., Malva sylvestris, Reseda phyteuma, Anacyclus sp., Sinapis arvensis, Medicago sp.) among spontaneous perennial woody shrubs (Genista umbellata, Olea europaea, Lavandula officinalis, Phlomis purpurea, Retama sphaerocarpa), and (2) an altered slope cultivated with subtropical trees on terraces: loquat (Eriobotrya japonica), mango (Mangifera indica), avocado (Persea americana), and cherimoya (Annona cherimola), with groundcover plantings of aromatic, medicinal, and melliferous plants (AMMPs) on the taluses of the terraces, which are usually used for erosion control: Lavandula dentata, Thymus mastichina, Satureja obovata, Rosmarinus officinalis, Anthyllis cytisoides. In the leaves from the subtropical crops, we found the highest decomposition rates in cherimoya and the lowest in mango (1.30 and 0.64 years−1, respectively). Leaves from mango and loquat registered initial peaks of N immobilization and later N-release, which was highest in cherimoya and avocado leaves (71.2 and 56.8% of the initial remaining N). In the spontaneous woody shrubs, O. europaea and G. umbellata were the slowest in decomposing (1.18 and 1.01 years−1, respectively) contrary to L. officinalis, which decomposed fastest (2.22 years−1). Only L. officinalis and P. purpurea registered a net N-release at the end of the study. The AMMPs showed different decomposition patterns: L. dentata registered the highest decomposition rates and Rosmarinus the lowest (1.9 and 1.1 years−1, respectively). T. mastichina, L. dentata, and S. obovata had the highest N-release, whereas R. officinalis and A. cytisoides showed N immobilization (183 and 122% of the initial N). Knowledge of the dynamics of nutrient release and litter decomposition will be useful for predicting nutrient availability and nutrient cycles in these types of agroecosystems where subtropical orchards are grown on terraces. 相似文献
150.
Simulated dynamics of carbon stocks driven by changes in land use, management and climate in a tropical moist ecosystem of Ghana 总被引:1,自引:0,他引:1
Zhengxi Tan Shuguang Liu Larry L. Tieszen Emmanuel Tachie-Obeng 《Agriculture, ecosystems & environment》2009,130(3-4):171-176
Sub-Saharan Africa is large and diverse with regions of food insecurity and high vulnerability to climate change. This project quantifies carbon stocks and fluxes in the humid forest zone of Ghana, as a part of an assessment in West Africa. The General Ensemble biogeochemical Modeling System (GEMS) was used to simulate the responses of natural and managed systems to projected scenarios of changes in climate, land use and cover, and nitrogen fertilization in the Assin district of Ghana. Model inputs included historical land use and cover data, historical climate records and projected climate changes, and national management inventories. Our results show that deforestation for crop production led to a loss of soil organic carbon (SOC) by 33% from 1900 to 2000. The results also show that the trend of carbon emissions from cropland in the 20th century will continue through the 21st century and will be increased under the projected warming and drying scenarios. Nitrogen (N) fertilization in agricultural systems could offset SOC loss by 6% with 30 kg N ha−1 year−1 and by 11% with 60 kg N ha−1 year−1. To increase N fertilizer input would be one of the vital adaptive measures to ensure food security and maintain agricultural sustainability through the 21st century. 相似文献