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1.
Elias Getahun Laura L. Keefer 《Journal of the American Water Resources Association》2023,59(3):510-522
A nutrient loss reduction strategy is necessary to guide the efforts of improving water quality downstream of an agricultural watershed. In this study, the effectiveness of two winter cover crops, namely cereal rye and annual ryegrass, is explored as a loss reduction strategy in a watershed that ultimately drains into a water supply reservoir. Using a coupled optimization-watershed model, optimal placements of the cover crops were identified that would result in the tradeoffs between nitrate-N losses reduction and adoption levels. Analysis of the 10%, 25%, 50%, and 75% adoption levels extracted from the optimal tradeoffs showed that the cover crop placements would provide annual nitrate-N loss reductions of 3.0%–3.7%, 7.8%–8.8%, 15%–17.5%, and 20.9%–24.3%, respectively. In addition, for the same adoption levels (i.e., 10%–75%), sediment (1.8%–17.7%), and total phosphorus losses (0.8%–8.6%) could be achieved. Results also indicate that implementing each cover crop on all croplands of the watershed could cause annual water yield reduction of at least 4.8%, with greater than 28% in the months of October and November. This could potentially be detrimental to the storage volume of the downstream reservoir, especially in drought years, if cover crops are adopted in most of the reservoir's drainage area. Evaluating water yield impacts, particularly in periods of low flows, is thus critical if cover crops are to be considered as best management practices in water supply watersheds. 相似文献
2.
Babita Thakur Jaswinder Singh Joginder Singh Deachen Angmo Adarsh Pal Vig 《环境质量管理》2023,33(1):173-181
Microplastics have been found in large quantities in agricultural soil and now become a major global issue. Different types of microplastic have adverse effects on agricultural soil. The most widely used method for the extraction of microplastics in agricultural soil is the density floatation method by using saturated NaCl solution. This method includes the pre-digestion of soil samples with H2O2 to remove all the organic matter present in the soil. Different types of microplastic particles were extracted and identified by using ATR-FTIR viz polypropylene, polybutylene tetrapthalate, polyethylene, polystyrene, and polyethylene tetrapthalate. The crystalline nature of extracted microplastic was checked by employing XRD analytical technique. Floatation with higher density saturated sodium chloride (NaCl) solution recovered approximately 80% MPs from soil. Floatation methods were found to be effective for extracting microplastics from soils. 相似文献
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Changes of protists, which were categorized into different functional groups primarily according to their feeding habits, in two full-scale municipal wastewater treatment systems experiencing sludge bulking were investigated over a period of 14 months. Protist biomass represented 3.7% to 5.2% of total biomass on average under normal sludge conditions, and the percentage increased significantly (p < 0.05) under sludge bulking conditions. The biomass of Chilodonella spp., capable of eating filamentous bacteria, tended to decrease in both systems when sludge bulking occurred, showing that the abnormal growth of filamentous bacteria did not lead to a biomass bloom of this group of protists. On the other hand, the bactivorous protists represented more than 96% of total protist biomass, and the biomass of this group, particularly the attached ciliates, increased significantly (p < 0.05) when sludge bulking occurred. The significant increase of the attached ciliates may have possibly facilitated the growth of filamentous bacteria through selectively preying on non-filamentous bacteria and further exacerbated sludge bulking. The redundancy analysis and correlation analysis results showed that the biomass changes of the attached ciliates were primarily related to the sludge volume index and to some extent related to five-day biochemical oxygen demand loading and hydraulic retention time. 相似文献
6.
A novel silica catalyst was synthesized by evaporation-induced self-assembly (EISA) method and tested for the catalytic selective hydrolysis of cellulose to glucose. This silica catalyst exhibited a higher catalytic activity than other oxides prepared by the same method, such as ZrO2, TiO2, and Al2O3. Using silica as a catalyst, cellulose was selectively hydrolyzed into glucose with a glucose yield as high as 50% under hydrothermal conditions without hydrogen gas. The silica catalyst was characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results of temperature-programmed desorption of ammonia (NH3-TPD) and textural properties indicated that the synergistic effect between strong acidity and a suitable pore diameter of the silica catalyst may be responsible for its high activity. In addition, the catalyst was recyclable and showed excellent stability during the recycle catalytic runs. 相似文献
7.
生物质发电是将废弃生物质变成可再生能源得以充分利用,这些工程将减少来自于生物质自然腐烂和无控燃烧产生的温室效应,这不仅节约了煤炭的同时也减少了二氧化碳的排放。本文中以某生物质项目发电为例,根据CDM方法学ACM0006计算了该项目的减排量。结果表明,该项目10年间共减少了二氧化碳排放量2,075,140 t,给我国带来了可观的经济效益和环境效益。 相似文献
8.
Differences in nitrous oxide fluxes from red soil under different land uses in mid-subtropical China 总被引:1,自引:0,他引:1
Shan LinJaved Iqbal Ronggui Hu Leilei RuanJinshui Wu Jinsong ZhaoPengju Wang 《Agriculture, ecosystems & environment》2012,146(1):168-178
Red soil may play an important role in nitrous oxide (N2O) emissions due to its recent land use change pattern. To predict the land use change effect on N2O emissions, we examined the relationship between soil N2O flux and environmental determinants in four different types of land uses in subtropical red soil. During two years of study (January 2005-January 2007), biweekly N2O fluxes were measured from 09:00 to 11:00 a.m. using static closed chamber method. Objectives were to estimate the seasonal and annual N2O flux differences from land use change and, reveal the controlling factors of soil N2O emission by studying the relationship of dissolved organic carbon (DOC), microbial biomass carbon (MBC), water filled pore space (WFPS) and soil temperature with soil N2O flux. Nitrous oxide fluxes were significantly higher in hot-humid season than in the cool-dry season. Significant differences in soil N2O fluxes were observed among four land uses; 2.9, 1.9 and 1.7 times increased N2O emissions were observed after conventional land use conversion from woodland to paddy, orchard and upland, respectively. The mean annual budgets of N2O emission were 0.71-2.21 kg N2O-N ha−1 year−1 from four land use types. The differences were partly attributed to increased fertilizer use in agriculture land uses. In all land uses, N2O fluxes were positively related to soil temperature and DOC accounting for 22-48% and 30-46% of the seasonal N2O flux variability, respectively. Nitrous oxide fluxes did significantly correlate with WFPS in orchard and upland only. Nitrous oxide fluxes responded positively to MBC in all land use types except orchard which had the lowest WFPS. We conclude that (1) land use conversion from woodland to agriculture land uses leads to increased soil N2O fluxes, partly due increased fertilizer use, and (2) irrespective of land use, soil N2O fluxes are under environmental controls, the main variables being soil temperature and DOC, both of which control the supply of nitrification and denitrification substrates. 相似文献
9.
Soh Sugihara Shinya FunakawaMethod Kilasara Takashi Kosaki 《Agriculture, ecosystems & environment》2012,146(1):209-219
In Sub-Saharan Africa, conservation of available soil N during early crop growth, when N loss by leaching generally occurs, is important to improve crop productivity. In a dry tropical cropland in Tanzania, we assessed the potential role of soil microbes as a temporal N sink-source to conserve the available soil N until later crop growth, which generally requires substantial crop N uptake. We evaluated the effect of land management [i.e., no input, plant residue application before planting (P plot) with or without fertilizer application, fertilizer application alone, and non-cultivated plots] on the relationship between soil N pool [microbial biomass N (MBN) and inorganic N] and crop N uptake throughout the ∼120-d crop growth period in two consecutive years. In the P plot, MBN clearly increased (∼14.6-29.6 kg N ha−1) early in the crop growth period in both years because of immobilization of potentially leachable N, and it conserved a larger soil N pool (∼10.5-21.2 kg N ha−1) than in the control plot. Especially in one year in which N leaching was critical, increased MBN maintained a larger soil N pool in the P plot throughout the experimental period, and a delay of increased MB C:N ratio and a substantial decrease in MBN was observed, indicating better soil microbial N supply for crop N uptake during later crop growth. Therefore, plant residue application before planting should enhance the role of soil microbes as a temporal N sink-source, leading to the conservation of potentially leachable N until later phase of crop growth, especially in years in which N leaching is relatively severe. Although further studies are necessary, our results suggest that plant residue application before planting is a promising option to achieve better N synchronization. 相似文献
10.
低温下氨氮对淡水浮游藻生长及群落结构影响的生态模拟研究 总被引:2,自引:1,他引:1
为了探讨春季藻类快速生长的机制,研究较低温度下氨氮对淡水浮游藻类生长及群落结构变化的影响,对南开大学新开湖水体藻类进行了室内生态模拟试验研究.在10℃、125μmol·m·s-1光强条件下,培养液中氨氮最终浓度设置为1.0、1.5、2.0、2.5、3.0mg·L-1和对照组(不添加氨氮),每隔1~2天加入氨氮至初始设定值,培养时间为26d.结果表明,浮游藻类在1.0mg·L-1组生长最好,最大生长密度为1.53×105cells·L-1,高于对照组;浮游藻类在高于2.0mg·L-1处理组中生长明显受到抑制,抑制作用随着氨氮浓度的增大而增大,其中3.0mg·L-1处理组的最大生物量仅为5.4×104cells·L-1.随着培养时间的进行硅藻逐渐取代绿藻而成为绝对优势藻,随着藻类的生长,粗刺四刺藻(Treubaria crassispina)在所有处理组中由优势种而逐渐消失,近缘针杆藻(Saffinis affinis)和新月藻(Closterium lunula)在培养后期逐渐成为优势种,但在不同氨氮浓度下表现出不同生长密度.除1.0mg·L-1处理组外,其它处理组中的物种多样性指数差异不显著(p>0.05).氨氮影响浮游藻类的生长,影响优势种的变化,并且对浮游藻类的群落结构变化有一定的影响. 相似文献