Comparison of Morphodynamic Models for the Lower Yellow River1

Xia, Junqiang, Zhengbing Wang, Yanping Wang, and Xin Yu, 2012. Comparison of Morphodynamic Models for the Lower Yellow River. Journal of the American Water Resources Association (JAWRA) 1‐18. DOI: 10.1111/jawr.12002 Abstract: Significant channel adjustments often occur during flood seasons in the Lower Yellow River (LYR), and it is a challenging work to accurately simulate the morphodynamic processes in the LYR using numerical models. A comparison of two morphodynamic models (Delft3D and 2DLLCDM) for the LYR is presented herein to identify critical improvements for these models. The concepts of these models are first compared with each other. The models were then used to simulate the processes of flood routing, sediment transport, and morphological changes occurring in a braided reach of the LYR. The differences were investigated between the simulated results from these models and corresponding field measurements, and the results indicate that: (1) the hydrodynamic processes calculated by both models agree closely with the measurements if an appropriate Manning’s roughness coefficient is used; (2) the concentrations of suspended load at the downstream boundary calculated by the models agree reasonably with the observed data; and (3) the predicted cross‐sectional profiles obtained from these models do not correspond well with the measurements. Based on these findings, the weak aspects of the models are clarified, and three critical improvements are recommended, including: (1) the development of roughness predictor; (2) the refinement of graded sediment transport capacity formulation; and (3) the consideration of bank erosion module. These improvements need to be implemented in the future.     

A Decade of Geomorphic and Hydraulic Response to the La Valle Dam Project,Baraboo River,Wisconsin

We investigate stream response to the La Valle Dam removal and channel reconstruction by estimating channel hydraulic parameter values and changes in sedimentation within the reservoir. The designed channel reconstruction after the dam removal included placement of a riffle structure at the former dam site. Stream surveys undertaken in 1984 by Federal Emergency Management Agency and in 2001 by Doyle et al. were supplemented with surveys in 2009 and 2011 to study the effects of the instream structure. We created a model in HEC‐RAS IV and surface maps in Surfer© using the 1984, 2009, and 2011 surveys. The HEC‐RAS IV model for 2009 channel conditions indicates that the riffle structure decreases upstream channel shear stress and velocity, causing renewed deposition of sediment within the former reservoir. We estimate by 2009, 61% of former reservoir sediments were removed during dam removal and channel reconstruction. Between 2009 and 2011 renewed sedimentation within the former reservoir represented approximately 7.85% of the original reservoir volume. The HEC‐RAS IV models show the largest impacts of the dam and riffle structure occur at flood magnitudes at or below bankfull. Thus, the riffle and the dam similarly alter channel hydraulics and sediment transport. As such, our models indicate that the La Valle Dam project was a dam replacement rather than a removal. Our results confirm that channel reconstruction method can alter channel hydraulics, geomorphology, and sediment mobility.     

重庆市老龙洞地下河流域硝酸盐来源和生物地球化学过程的识别

为明确城市地区岩溶地下水系统硝酸盐污染来源和生物地球化学过程,于2019年7月至2020年10月期间,采集了重庆市老龙洞地下河流域内的污水、井水和地下河水,测定其水化学和硝酸盐氮氧双同位素值（δ¹⁵ N-NO₃^-和δ¹⁸ O-NO₃^-）.结果表明：①污水的δ¹⁵ N-NO₃^-和δ¹⁸ O-NO₃^-分别介于-3.3‰~14.6‰和-5.2‰~20.6‰之间,说明污水中的硝酸盐主要来源于生活污水排放及化肥渗漏;井水的δ¹⁵ N-NO₃^-和δ¹⁸ O-NO₃^-分别介于3.1‰~12.6‰和2.9‰~8.9‰之间,说明井水中的硝酸盐主要来自于粪肥及土壤有机氮矿化分解;地下河水中的δ¹⁵ N-NO₃^-和δ¹⁸ O-NO₃^-分别介于5.6‰~28.6‰和-2.0‰~15.7‰之间,说明市政污水以及农田中施用的粪肥是地下河水中主要的硝酸盐来源.②基于MixSIAR模型计算得出,粪肥污水是地下河水中硝酸盐的主要贡献源,贡献占比为89.1%,土壤有机氮、化肥和大气降水贡献率分别为4.4%、3.4%和3.1%.③流域内的COD ：ρ（NO₃^-）由低到高依次为：井水（0.14~5.15）、地下河水（0.50~9.36）和污水（4.08~89.50）.仅有50%井水样品的COD ：ρ（NO₃^-）略高于反硝化发生的化学计量比最低限（0.65）,说明COD可能不足以支撑井水中发生反硝化,井水中的硝酸盐氮氧双同位素未发生明显富集,验证了井水中未发生反硝化作用;90%地下河水样品的COD ：ρ（NO₃^-）高于0.65,硝酸盐氮氧双同位素同步富集,δ¹⁵ N ：δ¹⁸ O为1.8,介于反硝化发生时的1.3~2.1,说明地下河水在流动过程中发生了反硝化作用;所有污水样品的COD ：ρ（NO₃^-）远高于0.65,其中25%污水样品的COD ：ρ（NO₃^-）高于发生异化还原为铵（DNRA）的优势化学计量比（29.34）,δ¹⁵ N-NO₃^-和ρ（NH₄⁺）：ρ（NO₃^-）同步升高,表明污水中可能发生了DNRA.     

Holly (Ilex Aquifolium L.) As Zinc and Cadmium Accumulative Indicator in Biogeochemical Prospecting

The results of previous investigations in mineralized and sterile areas of Tuscany (Italy) appeared to point out the special aptitude of holly (Ilex aquifolium L.) in concentrating cadmium and zinc. in the present paper this behaviour has been verified in a mineralized area of Lombardy (Northern Italy).

Samples of leaves, twigs and barks from holly trees were collected, and metal contents (Zn, Cd, and Pb) have been determined by differential pulse anodic stripping voltammetry (DPASV). for comparison, some samples of wood anemone (Anemone nemorosa L.) and soil were also analyzed.

The data obtained confirm a preferential cadmium and zinc accumulation by holly (up to 16 and 1400 μg g^-1 dry weight, respectively) also depending on different vegetal organs and vegetative stages of plants. Highest contents of lead have been recovered in the outer portion of bark.     

Technogenic stress and its effect on deciduous trees (an example from parks in Yaroslavl)

A comparative analysis of several morphological, physiological, and biochemical characteristics of leaves has been performed in birch (Betula pendula Roth), linden (Tilia cordata Mill.), and poplar (Populus nigra L.) trees growing in industrial areas of Yaroslavl with different levels of anthropogenic pollution. The results show that high concentrations of pollutants in the atmosphere suppress the growth of leaves, and the number and severity of necrotic lesions in them increase. Water content in leaves becomes lower, whereas ash content increases. The contents of photosynthetic pigments change as well: the leaves contain smaller amounts of chlorophylls a and b, whereas the accumulation of carotenoids increases. Judging from changes in the test parameters, P. nigra is more resistant to pollution than B. pendula and T. nordata.     

Groundwater Denitrification Capacity of Riparian Zones in Suburban and Agricultural Watersheds1

Watson, Tara K., Dorothy Q. Kellogg, Kelly Addy, Arthur J. Gold, Mark H. Stolt, Sean W. Donohue, and Peter M. Groffman, 2010. Groundwater Denitrification Capacity of Riparian Zones in Suburban and Agricultural Watersheds. Journal of the American Water Resources Association (JAWRA) 46(2):237-245. DOI: 10.1111/j.1752-1688.2010.00418.x Abstract: We evaluated the relationship of dominant watershed land use to the structure and nitrogen (N) sink function of riparian zones. We focused on groundwater denitrification capacity, water table dynamics, and the presence and pattern of organically enriched deposits. We used the push-pull method (measurement of ¹⁵N-enriched denitrification gases derived from an introduced groundwater plume of ¹⁵N-enriched nitrate) to evaluate groundwater denitrification capacity on nine forested wetland riparian sites developed in alluvial or outwash parent materials in southern New England. Three replicate sites were located in each of the three watershed types, those with substantial (1) irrigated agriculture, (2) suburban development, and (3) forest. Soil morphology and water table dynamics were assessed at each site. We found significantly lower mean annual water tables at sites within watersheds with substantial irrigated agriculture or suburban development than forested watersheds. Water table dynamics were more variable at sites within suburban watersheds, especially during the summer. Groundwater denitrification capacity was significantly greater at sites within forested watersheds than in watersheds with substantial irrigated agriculture. Because of the high degree of variability observed in riparian sites within suburban watersheds, groundwater denitrification capacity was not significantly different from either forested or agricultural watersheds. The highly variable patterns of organically enriched deposits and water tables at sites within suburban watersheds suggests that depositional events are irregular, limiting the predictability of groundwater N dynamics in these riparian zones. The variability of riparian N removal in watersheds with extensive suburbia or irrigated agriculture argues for N management strategies emphasizing effective N source controls in these settings.     

POST‐HARVEST RIPARIAN BUFFER RESPONSE: IMPLICATIONS FOR WOOD RECRUITMENT MODELING AND BUFFER DESIGN1

Despite the importance of riparian buffers in providing aquatic functions to forested streams, few studies have sought to capture key differences in ecological and geomorphic processes between buffered sites and forested conditions. This study examines post‐harvest buffer conditions from 20 randomly selected harvest sites within a managed tree farm in the Cascade Mountains of western Washington. Post‐harvest wind derived treefall rates in buffers up to three years post‐harvest averaged 268 trees/km/year, 26 times greater than competition‐induced mortality rate estimates. Treefall rates and stem breakage were strongly tied to tree species and relatively unaffected by stream direction. Observed treefall direction is strongly biased toward the channel, irrespective of channel or buffer orientation. Fall direction bias can deliver significantly more wood recruitment relative to randomly directed treefall, suggesting that models that utilize the random fall assumption will significantly underpredict recruitment. A simple estimate of post‐harvest wood recruitment from buffers can be obtained from species specific treefall and breakage rates, combined with bias corrected recruitment probability as a function of source distance from the channel. Post‐harvest wind effects may reduce the standing density of trees enough to significantly reduce or eliminate competition mortality and thus indirectly alter bank erosion rates, resulting in substantially different wood recruitment dynamics from buffers as compared to unmanaged forests.     

电子加速器辐射处理含氰废水的中试研究

以江苏省某碳纤维生产企业排放的含氰工业废水为研究对象,采用自屏蔽Dynamitron电子加速器(能量0.5~1.0 MeV,束流10~15 mA)开展了处理量为30 m3·d-1的中试实验.通过正交实验设计,研究了不同因素对氰化物降解的影响,优化了操作条件.研究结果表明,加速器辐照能够有效去除废水中的氰化物,当CN-浓度为21.08~117.49 mg·L-1,辐照剂量为1.5 kGy时,CN-的去除率为33.88%~59.25%.臭氧的存在可以显著提高氰化物的去除效率,辐照过程中加入2 mg·L-1的臭氧,在相同辐照剂量下,CN-的去除率可提高到48.19%~82.62%,氰化物的辐射降解可以用准一级反应动力学模型描述.氰化物辐射降解的主要产物为氨氮和氰酸盐.本实验研究是我国第一例运用电子加速器连续辐照处理实际工业废水的中试规模实验,为电离辐射技术在我国废水处理领域中的应用起到了良好的工程示范作用.     

兽用抗生素磺胺二甲嘧啶对稻田N2O排放的影响及其微生物机制

为研究磺胺类兽用抗生素对稻田N_2O排放的影响及其微生物机制,采用田间原位观测试验,对比分析不同浓度磺胺二甲嘧啶(sulfamethazine,SMZ)对稻田N_2O排放及硝化反硝化过程底物和相关功能基因丰度的影响.本试验共设5个处理,分别为:无肥料无抗生素(CK);猪粪为基肥,尿素为追肥,分别添加0、5、15和30 mg·kg~(-1)的SMZ处理(SMZ0、SMZ5、SMZ15和SMZ30),在整个水稻生长季定期采集和分析土壤和气体样品.结果表明,不同浓度SMZ均未改变稻田N_2O排放的季节性规律,整个观测期N_2O排放通量,与SMZ0处理相比,SMZ15有显著差异(P 0. 05),SMZ30和SMZ5无显著差异(P 0. 05).中、高浓度处理SMZ15和SMZ30在均值水平上增加了N_2O累积排放量,分别是SMZ0处理的3. 47和4. 67倍,且增加了土壤NO_3~--N含量.与SMZ0处理相比,中、高浓度处理对土壤总细菌16S rRNA基因丰度、硝化过程中氨氧化古菌AOA amoA和氨氧化细菌AOB amoA基因丰度以及反硝化过程中的nirK、nirS和nosZ基因丰度均有明显的激活作用(P 0. 05),低浓度处理SMZ5对各基因丰度则有轻微抑制作用.具体表现为SMZ30、SMZ15与SMZ0处理的16S rRNA、AOA amoA、AOB amoA以及nirK、nirS、nosZ基因丰度比值的平均值分别为:1. 58、1. 77、2. 15、1. 38、1. 33、1. 42和1. 24、1. 37、1. 08、1. 65、1. 11、1. 64,而SMZ5与SMZ0处理的6个上述基因丰度比值均小于1,仅分别为0. 80、0. 99、0. 92、0. 76、0. 76和0. 77. N_2O排放通量与nir K基因丰度呈极显著正相关(P 0. 01),表明SMZ通过影响反硝化菌活性进而对N_2O排放产生作用.因此,兽用抗生素对农田的污染不可忽视,应从源头上合理控制使用,以减少其环境生态风险.     

N原子杂化石墨烯高效活化过一硫酸盐降解RBk5染料废水

过硫酸盐高级氧化技术使用过程中,活化剂的大量流失与其环境二次危害是影响该技术应用的主要限制因素.针对这一问题本研究采用改进的Hummers法结合水热法制备环境友好型的N原子掺杂石墨烯作为催化剂,活化过一硫酸盐(PMS)产生硫酸根自由基(SO4-·)和羟基自由基(·OH)降解活性黑5(RBk5)染料.利用傅立叶红外光谱,X-射线光电子能谱,拉曼光谱和透射电子显微镜对N原子掺杂石墨烯进行表征.对催化剂催化性能进行研究,考察了初始p H、催化剂投加量和PMS投加量等因素对降解过程的影响.结果表明,N元素掺杂能够有效提升石墨烯材料的PMS催化活性,且活性受N掺杂比例影响较大;废水的初始p H对降解效率无明显影响.催化剂投加量为1. 5 g·L-1,PMS投加量为0. 3 g·L-1的条件下,反应25min后RBk5染料废水的降解率可达到99%以上,反应过程符合一级反应动力学.自由基猝灭实验显示,N掺杂石墨烯/PMS体系降解RBk5为表面反应,SO4-·和·OH为降解RBk5的主要自由基.循环实验证明催化剂稳定性能良好.