A Comparison of DEM‐Based Indexes for Targeting the Placement of Vegetative Buffers in Agricultural Watersheds

Targeted placement of vegetative buffers may increase their effectiveness for improving water quality in agricultural watersheds. The use of digital elevation models (DEMs) enables precise mapping of runoff pathways for identifying where greater runoff loads can be intercepted and treated with buffers. Five different DEM‐based targeting indexes were compared and contrasted for the degree to which they identify similar locations in watersheds: Flow Accumulation [S.K. Jenson and J.O. Domingue (1988). Photogrammetric Engineering and Remote Sensing 54:1593], Wetness Index [I.D. Moore, R.B. Grayson, and A.R. Ladson (1991). Hydrological Processes 5:3], Topographic Index [M.T. Walter, T.S. Steenhuis, V.K. Mehta, D. Thongs, M. Zion, and E. Schneiderman (2002). Hydrological Processes 16:2041], and the Water Inflow and Sediment Retention Indexes [M.G. Dosskey, Z. Qiu, M.J. Helmers, and D.E. Eisenhauer (2011b). Journal of Soil and Water Conservation 66:362]. The indexes were applied in two different watersheds, one in New Jersey and one in Missouri. Results showed that they all tend to target similar locations in both watersheds which traces to the importance of larger contributing area to the rankings by each index. Disagreement among indexes traces to other variables which enable more accurate targeting under particular hydrologic circumstances. Effective use of these indexes poses special challenges, including selecting an index that better describes the hydrologic circumstances in a watershed and is simple enough to use, ensuring the accuracy of the DEM, and determining a maximum index value for the appropriateness of vegetative buffers. When properly applied, each index can provide a standardized basis and effective spatial resolution for targeting buffer placement in watersheds.     

土壤理化性质对Fe~0还原硝基苯的影响

采用零价铁（Fe0）还原降解土壤中的硝基苯,考察土壤理化性质对还原效果的影响。结果显示,当2 g土壤中NB含量约为2.5×10-6mol/g,铁粉用量为50 mg,土壤含水量为75%时,控温25℃条件下反应1 h,硝基苯在松砂土和中壤土中的还原率分别可达到82.9%和91.1%。硝基苯在2种土壤中的还原率表现出中壤土〉松砂土的规律;土壤微生物和土壤有机质含量升高有利于反应进行;粒径偏小的中壤土中硝基苯还原较彻底。NB在土壤中的老化时间对Fe0还原效果影响较小。     

Range of ecological impact of highway construction in the Longitudinal Range-Gorge Region,China

The major features of different road sections were identified. Methods quantitatively determining the ecological impact of highway construction were discussed, and a demonstration was presented. The Dabao highway (from Dali to Baoshan) and the Sixiao highway (from Simao to Xiaomengyang) passing through the Longitudinal Range-Gorge Region were used as examples in this paper. For the normal road sections having no important species to protect, a method of ecosystem health assessment was introduced to calculate the overall range of the ecological impact of highway construction. For the road sections having plants or soils of interest, indexes were selected and the range of impact was determined using mathematical methods such as regression analysis and variance analysis. The range of impact on animal populations was also discussed in terms of the minimum living areas required by animal populations and the fragmentation caused by highway construction. The results indicate that the zones impacted by highway construction were composed of both regular and anomalous figures, the range of impacts for different landforms of the two sample highways were substantially different; highway construction had dramatic effects on roadside ecosystem health; the impact on soil factors of farmland was greater than 200 m, and the distance may exceed 1000 m when important large animals were considered.     

Poultry litter-based activated carbon for removing heavy metal ions in water

Utilization of poultry litter as a precursor material to manufacture activated carbon for treating heavy metal-contaminated water is a value-added strategy for recycling the organic waste. Batch adsorption experiments were conducted to investigate kinetics, isotherms, and capacity of poultry litter-based activated carbon for removing heavy metal ions in water. It was revealed that poultry litter-based activated carbon possessed significantly higher adsorption affinity and capacity for heavy metals than commercial activated carbons derived from bituminous coal and coconut shell. Adsorption of metal ions onto poultry litter-based carbon was rapid and followed Sigmoidal Chapman patterns as a function of contact time. Adsorption isotherms could be described by different models such as Langmuir and Freundlich equations, depending on the metal species and the coexistence of other metal ions. Potentially 404 mmol of Cu²⁺, 945 mmol of Pb²⁺, 236 mmol of Zn²⁺, and 250–300 mmol of Cd²⁺ would be adsorbed per kg of poultry litter-derived activated carbon. Releases of nutrients and metal ions from litter-derived carbon did not pose secondary water contamination risks. The study suggests that poultry litter can be utilized as a precursor material for economically manufacturing granular activated carbon that is to be used in wastewater treatment for removing heavy metals.     

Characterizing spatiotemporal non-stationarity in vegetation dynamics in China using MODIS EVI dataset

This paper evaluated the spatiotemporal non-stationarity in the vegetation dynamic based on 1-km resolution 16-day composite Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) datasets in China during 2001–2011 through a wavelet transform method. First, it revealed from selected pixels that agricultural crops, natural forests, and meadows were characterized by their distinct intra-annual temporal variation patterns in different climate regions. The amplitude of intra-annual variability generally increased with latitude. Second, parameters calculated using a per-pixel strategy indicated that the natural forests had the strongest variation pattern from seasonal to semiannual scales, and the multiple-cropping croplands typically showed almost equal variances distributed at monthly, seasonal, and semiannual scales. Third, spatiotemporal non-stationarity induced from cloud cover was also evaluated. It revealed that the EVI temporal profiles were significantly distorted with regular summer cloud cover in tropical and subtropical regions. Nevertheless, no significant differences were observed from those statistical parameters related to the interannual and interannual components between the de-clouded and the original MODIS EVI datasets across the whole country. Finally, 12 vegetation zones were proposed based on spatiotemporal variability, as indicated by the magnitude of interannual and intra-annual dynamic components, normalized wavelet variances of detailed components from monthly to semiannual scale, and proportion of cloud cover in summer. This paper provides insightful solutions for addressing spatiotemporal non-stationarity by evaluating the magnitude and frequency of vegetation variability using monthly, seasonal, semiannual to interannual scales across the whole study area.     

Synergistic cytotoxicity of binary combinations of inorganic and organic disinfection byproducts assessed by real-time cell analysis

Chlorine, chlorine dioxide, and ozone are widely used as disinfectants in drinking water treatments. However, the combined use of different disinfectants can result in the formation of various organic and inorganic disinfection byproducts (DBPs). The toxic interactions, including synergism, addition, and antagonism, among the complex DBPs are still unclear. In this study, we established and verified a real-time cell analysis (RTCA) method for cytotoxicity measurement on Chinese hamster ovary (CHO) cell. Using this convenient and accurate method, we assessed the cytotoxicity of a series of binary combinations consisting of one of the 3 inorganic DBPs (chlorite, chlorate, and bromate) and one of the 32 regulated and emerging organic DBPs. The combination index (CI) of each combination was calculated and evaluated by isobolographic analysis to reflect the toxic interactions. The results confirmed the synergistic effect on cytotoxicity in the binary combinations consisting of chlorite and one of the 5 organic DBPs (2 iodinated DBPs (I-DBPs) and 3 brominated DBPs (Br-DBPs)), chlorate and one of the 4 organic DBPs (3 aromatic DBPs and dibromoacetonitrile), and bromate and one of the 3 organic DBPs (2 I-DBPs and dibromoacetic acid). The possible synergism mechanism of organic DBPs on the inorganic ones may be attributed to the influence of organic DBPs on cell membrane and cell antioxidant system. This study revealed the toxic interactions among organic and inorganic DBPs, and emphasized the latent adverse outcomes in the combined use of different disinfectants.     

N-doped CoAl oxides from hydrotalcites with enhanced oxygen vacancies for excellent low-temperature propane oxidation

A series of nitrogen-doped CoAlO (N-CoAlO) were constructed by a hydrothermal route combined with a controllable NH₃ treatment strategy. The effects of NH₃ treatment on the physico-chemical properties and oxidation activities of N-CoAlO catalysts were investigated. In comparison to CoAlO, a smallest content decrease in surface Co³⁺ (serving as active sites) while a largest increased amount of surface Co²⁺ (contributing to oxygen species) are obtained over N-CoAlO/4h among the N-CoAlO catalysts. Meanwhile, a maximum N doping is found over N-CoAlO/4h. As a result, N-CoAlO/4h (under NH₃ treatment at 400°C for 4 hr) with rich oxygen vacancies shows optimal catalytic activity, with a T₉₀ (the temperature required to reach a 90% conversion of propane) at 266°C. The more oxygen vacancies are caused by the co-operative effects of N doping and suitable reduction of Co³⁺ for N-CoAlO/4h, leading to an enhanced oxygen mobility, which in turn promotes C₃H₈ total oxidation activity dominated by Langmuir-Hinshelwood mechanism. Moreover, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) analysis shows that N doping facilities the decomposition of intermediate species (propylene and formate) into CO₂ over the catalyst surface of N-CoAlO/4h more easily. Our reported design in this work will provide a promising way to develop abundant oxygen vacancies of Co-based catalysts derived from hydrotalcites by a simple NH₃ treatment.     

水肥管理对热带地区双季稻田CH4和N2O排放的影响

水稻土被广泛认为是甲烷（CH₄）和氧化亚氮（N₂O）主要排放源,深入研究不同水肥管理条件下热带地区双季稻田CH₄和N₂O的排放特征,对补充我国双季稻田温室气体排放研究的不足意义重大.本研究设置8个处理：常规灌溉-施磷钾肥（D-PK）、常规灌溉-施氮磷钾肥（D-NPK）、常规灌溉-施氮磷钾+有机肥（D-NPK+M）、常规灌溉-施有机肥（D-M）、长期淹水-施磷钾肥（F-PK）、长期淹水-施氮磷钾肥（F-NPK）、长期淹水-施氮磷钾+有机肥（F-NPK+M）和长期淹水-施有机肥（F-M）.采用密闭静态箱-气相色谱法测定双季稻田CH₄和N₂O排放量,测定水稻产量和估算全球增温潜势（GWP）及温室气体排放强度（GHGI）.结果表明：①早稻季和晚稻季CH₄累积排放量分别为10.3~78.9 kg·hm^-2和84.6~185.5 kg·hm^-2.与F-PK和F-NPK处理相比,早稻季F-NPK+M和F-M处理显著增加CH₄累积排放量.同一施肥条件下,长期淹水处理CH₄累积排放量高于常规灌溉处理.灌溉和施肥极显著影响早稻季CH₄累积排放量.②早稻季和晚稻季N₂O累积排放量分别为0.18~0.76 kg·hm^-2和0.15~0.58 kg·hm^-2.与F-PK处理相比,早稻季F-NPK处理N₂O累积排放量显著增加;与D-PK相比,D-NPK、D-NPK+M和D-M处理显著增加N₂O累积排放量.与F-PK相比,晚稻季长期淹水其它处理N₂O累积排放量显著增加;与D-PK处理相比,D-NPK和D-M处理N₂O累积排放量显著增加.施肥极显著影响早稻季N₂O排放;灌溉和施肥极显著影响晚稻季N₂O排放.③早稻和晚稻产量分别为7310.7~9402.4 kg·hm^-2和3902.8~7354.6 kg·hm^-2,且F-NPK和F-M处理下早稻产量显著高于F-PK和D-NPK、D-PK和D-NPK处理.与PK处理相比,同一灌溉条件下其余3种施肥处理均显著增加晚稻产量.早稻季GWP和GHGI分别为580.8~2818.5kg·hm^-2和0.08~0.30 kg·kg^-1.与F-PK处理相比,常规灌溉条件下早稻季各施肥处理间GWP无显著性差异;但长期淹水条件下F-NPK+M和F-M处理GWP均显著增加.早稻季F-NPK+M和F-M处理GHGI显著高于其它处理.晚稻季GWP和GHGI分别为3091.6~6334.2 kg·hm^-2和0.50~1.23 kg·kg^-1.灌溉显著影响早稻和晚稻季GWP和GHGI,施肥对晚稻季GWP和GHGI的影响不显著.④土壤NH₄⁺-N含量和5 cm土温均与CH₄排放呈极显著负相关,pH与CH₄排放呈极显著正相关,但与N₂O排放呈显著负相关.土壤NH₄⁺-N和NO₃^--N含量与N₂O排放呈极显著负相关.综合作物产量、GWP和GHGI考虑,D-NPK+M可推荐为当地最优的减排稳产的水肥管理模式.     

生命周期评价在我国固体废物环境管理中的应用

生命周期评价是评价产品、工艺或活动（服务）整个生命周期阶段有关环境负荷,进而辨识和评价减少环境影响机会的一种非常有用的工具。将生命周期评价应用于固体废物环境管理,无疑对于我国建立科学化的固体废物环境管理模式具有十分重要的作用。本文对生命周期评价的定义、主要阶段、应用工具、特点进行了阐述,并对生命周期评价如何应用于我国固体废物环境管理进行了探讨。