Evaluation of SWAT Impoundment Modeling Methods in Water and Sediment Simulations

Worldwide studies show 80%–90% of all sediments eroded from watersheds is trapped within river networks such as reservoirs, ponds, and wetlands. To represent the impact of impoundments on sediment routing in watershed modeling, Soil and Water Assessment Tool (SWAT) developers recommend to model reservoirs, ponds, and wetlands using impoundment tools (ITs). This study evaluates performance of SWAT ITs in the modeling of a small, agricultural watershed dominated by lakes and wetlands. The study demonstrates how to incorporate impoundments into the SWAT model, and discusses and evaluates involved parameters. The study then recommends an appropriate calibration sequence, i.e., landscape parameters calibration, followed by pond/wetlands calibration, then channel parameter calibrations, and lastly, reservoir parameter calibration. Results of this study demonstrate not following SWAT recommendation regarding modeling water land use as an impoundment depreciates SWAT performance, and may lead to misplaced calibration efforts and model over‐calibration. Further, the chosen method to model impoundments’ outflow significantly impacts sediment loads in the watershed, while streamflow simulation is not very sensitive. This study also allowed calculation of mass accumulation rates in modeled impoundments where the annual mass accumulation rate in wetlands (2.3 T/ha/yr) was 39% higher than mass accumulation rate in reservoirs (1.4 T/ha/yr).     

对硝基苯胺的光化学降解研究

系统研究了氙灯和高压汞灯照射下对硝基苯胺(PNA)在蒸馏水、人工海水和天然海水中的光化学降解情况.结果表明,PNA光降解速率会受到光源、溶液介质、温度、起始浓度、重金属离子、甲醇及过氧化氢浓度的影响.随着光源强度的增强、起始浓度的增大、温度的增高和过氧化氢量的增加,PNA在海水中光降解速率相应加快;然而甲醇的加入可有效...     

火焰原子吸收测定中的背景吸收和基体干扰

为了探讨火焰原子吸收法测定成分复杂样品时干扰的影响,采用扣除背景的方法来排除背景吸收,采用标准加入法来消除基体干扰的影响。通过对上述方法的对比实验,绘制相应的工作曲线图,能直观、准确地反映出背景吸收和基体干扰对样品测定的影响程度。扣背景和采用标准加入法两者结合使用能达到使样品测定结果准确可靠的目的。     

A CALIBRATION PROCEDURE USING TOPMODEL TO DETERMINE SUITABILITY FOR EVALUATING POTENTIAL CLIMATE CHANGE EFFECTS ON WATER YIELD1

ABSTRACT: An evaluation was conducted on three forested upland watersheds in the northeastern U.S. to test the suitability of TOPMODEL for predicting water yield over a wide range of climatic scenarios. The analysis provides insight of the usefulness of TOPMODEL as a predictive tool for future assessments of potential long-term changes in water yield as a result of changes in global climate. The evaluation was conducted by developing a calibration procedure to simulate a range of climatic extremes using historical temperature, precipitation, and streamfiow records for years having wet, average, and dry precipitation amounts from the Leading Ridge (Pennsylvania), Fernow (West Virginia), and Hubbard Brook (New Hampshire) Experimental Watersheds. This strategy was chosen to determine whether the model could be successfully calibrated over a broad range of soil moisture conditions with the assumption that this would be representative of the sensitivity necessary to predict changes in streamfiow under a variety of climate change scenarios. The model calibration was limited to a daily time step, yet performed reasonably well for each watershed. Model efficiency, a least squares measure of how well a model performs, averaged between 0.64 and 0.78. A simple test of the model whereby daily temperatures were increased by 1.7°C, resulted in annual water yield decreases of 4 to 15 percent on the three watersheds. Although these results makes the assumption that the model components adequately describe the system, this version of TOPMODEL is capable to predict water yield impacts given subtle changes in the temperature regime. This suggests that adequate representations of the effects of climate change on water yield for regional assessment purposes can be expected using the TOPMODEL concept.     

非饱和土壤轻油污染多相流研究进展

轻油泄漏到地下后 ,在非饱和土壤中水、气、油三相相互作用、相互影响 ,共同构成多相流体系统。在简要分析轻油污染问题的产生、危害以及轻油泄漏在地表以下运移方式的基础上 ,介绍并总结了近些年来国内外土壤轻油污染有关的多相流研究方面的进展 ,包括国外的模型研究成果、国内外试验研究方法和研究成果 ,并指出目前研究中存在的问题和需要进一步探讨的方向     

声发射检测灵敏度校准声源实验分析

在声发射技术的应用中,传感器的工作频率和灵敏度对AE检测的结果具有决定性的作用,传感器的校准是AE定量研究的基础,也是声发射检测技术研究中的重要课题。根据二级校准的相关要求设计了三个不同声源的实验:落球、断铅和压断毛细玻璃管法。通过重复性实验,测量了不同大小的钢球从不同高度下落;不同粗细、硬度以及不同长度的铅芯的断裂;不同粗细的毛细玻璃管被压断产生的脉冲声源,分别比较以上三个实验在不同状态条件下产生的脉冲声源信号,分析其实时特征和频谱特征(峰值,上升时间),通过计算确定其不确定度和稳定度,总结优化操作方法,同时分析了实验误差。在此基础上得出最适合做声发射传感器灵敏度校准的脉冲声源,为声发射传感器校准中的参考声源提供性能评判的依据。     

荸荠对铜绿微囊藻的化感抑制作用研究

采取植物种植水培养、植物浸提液培养及植物共培养3种培养方式研究了荸荠对铜绿微囊藻生长的影响.结果发现:荸荠植株种植水、荸荠浸提液以及荸荠与铜绿微囊藻共培养均对铜绿微囊藻的生长产生了化感抑制作用.100%浓度的荸荠浸提液对铜绿微囊藻生长抑制率达到91.40%,而荸荠与铜绿微囊藻共培养时对铜绿微囊藻生长的抑制率为86.83%.这两者之间的差异并不显著,直接验证了荸荠能够通过不断地向水体中释放化感物质来长久、有效地抑制铜绿微囊藻的生长.     

Standard purity and response factors of perfluorinated compounds

It has been reported that the relative response factors of isotopically labeled standards and unlabeled standards of the same perfluorinated compounds could be different. Individual (100 ng mL^?1) solutions of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were analyzed using high-performance liquid chromatography tandem mass-spectrometry under negative-ion electrospray to detect any impurities present down to 0.5%–0.1% relative to the major component. Purity of the standards ranged from approximately 86% to ≥ 97%. Standard solutions of unlabeled and isotopically labeled materials were analyzed to compare the response factors of isotopically labeled analytes versus their nonlabeled counterparts in three different matrices at equivalent concentrations: organic solvent (methanol), serum extract, and water present individually and concurrently. Not all labeled analytes have the same response factor as their nonlabeled complement, and in at least one case the matrix in which the standard is present may cause significant suppression of response. Standard solutions of electrochemical fluorination produced PFOA and PFOS were quantified under multiple reaction monitoring mode, using calibration curves prepared from standards consisting primarily of linear standards only. The use of linear only standards may cause under-prediction of concentrations, and that the working range of these standards may be limited.     

桉树叶水浸出液对2种海洋微藻生长和叶绿素荧光特性的影响

运用水样叶绿素荧光仪(Water-PAM)研究了桉树叶水浸出液胁迫下湛江叉鞭金藻(Dicrateria zhanjiangensis)和纤细角毛藻(Chaetoceros gracilis)2种海洋微藻叶绿素荧光特性〔包括PS(光系统)Ⅱ的F_v/F₀(潜在活性)、F_v/F_m(最大光能转化效率)、Yield(实际光能转化效率)、ETR(电子传递效率),其中F_m和F₀分别为最大荧光和基础荧光〕的变化,同时监测微藻的生长情况,以研究桉树叶水浸出液对海洋微藻的影响,从而为探讨华南沿海大量种植桉树所造成潜在的海洋生态问题提供一些依据. 结果表明:①低浓度(以φ计,0.4、0.8、1.2mL/L)胁迫在96h内对湛江叉鞭金藻的上述4项荧光参数均无显著影响(P>0.05);高浓度(2.0mL/L)胁迫下,24h时湛江叉鞭金藻的4项荧光参数都处于最低值,48h时处于次低值. 表明高浓度在胁迫早期(48h内)对湛江叉鞭金藻4项荧光参数有抑制作用,而后期(72、96h)这4项荧光参数又恢复到正常水平,抑制作用解除. ②低浓度(0.4、0.8mL/L)胁迫下纤细角毛藻的4项荧光参数在24、48h内均得到促进,而高浓度(2.0mL/L)胁迫下F_v/F_m在24h时为最小值,表现抑制作用;另外3项荧光参数则未受显著影响. 在胁迫后期(72、96h),纤细角毛藻的4项荧光参数均随着胁迫浓度的增大而增加,表现为促进作用. ③就生长情况而言,随着胁迫浓度的增大,2种海洋微藻细胞密度的增长明显变缓. 表明桉树叶水浸出液对2种海洋微藻的生长以及叶绿素荧光特性都有影响,从而将会对整个海洋生态系统产生影响.      

Local calibration of coliforms parameters of water quality problem at Igapó I Lake, Londrina, Paraná, Brazil

This article presents results concerning the local calibration of the transport parameters (longitudinal and transversal diffusions and decay coefficient) for a two-dimensional problem of water quality at Igapó I Lake, located in Londrina, Paraná, Brazil, using fecal coliforms as an indicator of water quality. The simulation of fecal coliforms concentrations all over the water body is conducted by means of a structured discretization of the geometry of Igapó I Lake, together with the finite difference and finite element methods. By using the velocity field, modeled by the Navier-Stokes and Poisson equations, the flow of fecal coliforms is described by means of a transport model, which considers advective and diffusive processes, as well as a process of fecal coliforms decay. In the checkpoint, the longitudinal and transversal diffusion coefficients and the coliforms decay coefficient that best fitted the value of the fecal coliforms concentration were D_x = D_y = 0.001 m²/h and k = 0.5 d⁻¹ = 0.02083 h⁻¹. A qualitative and quantitative analysis of the numerical simulations conducted in function of the diffusion coefficients and of the coliforms decay parameter provided a better understanding of the local water quality at Igapó I Lake.