Estimating the Effects of the Conservation Reserve Program on Water Quality of Agricultural Watersheds in the US

55 pagesExcessive anthropogenic inputs of nitrogen (N) and phosphorus (P) to agricultural watersheds of the contiguous US have a detrimental impact on national water quality. In this paper, we develop a panel fixed effects model to examine the water quality response to the Conservation Reserve Program (CRP), a federal program that reimburses farmland owners to convert their land from agricultural production and restore it to natural habitats. We find that both N and P respond negatively to CRP enrollment, while the responsiveness of the nutrients differentiates between CRP contract types. In addition, we find the N response to continuous CRP enrollment to be more elastic than P. Our results have important implications for the causal inference procedures in the evaluation of conservation programs such as the CRP, while incorporating the effects from other explanatory variables that may preserve strong spatial variability

Key Factors, Planning Strategy and Policy for Low-Carbon Transport Development in Developing Cities of China

Exploring key impact factors and their effects on urban residents’ transport carbon dioxide (CO2) emissions is significant for effective low-carbon transport planning. Researchers face the model uncertainty problem to seek a rational and better explanatory model and the key variables in the model set containing various factors after they are arranged and combined. This paper uses the Bayesian Model Averaging method to solve the above problem, explore the key variables, and determine their relative significance and averaging effects. Beijing, Xi’an, and Wuhan are selected as three case cities for their representation of developing Chinese cities. We found that the initial key factor increasing transport emissions is the high dependence on cars, and the second is the geographical location factor that much more suburban residents suffer longer commuting. Developing satellite city rank first for reducing transport emissions due to more local trips with an average short distance, the second is the metro accessibility, and the third is polycentric form. Key planning strategies and policies are proposed: (i) combining policies of car restriction based on vehicle plate number, encouraging clean fuel cars, a carbon tax on oil uses, and rewarding public transit passengers; (ii) fostering subcenters’ strong industries to develop self-contained polycentric structures and satellite cities, and forming employment and life circle within 5 km radius; and (iii) integrating bus and rail transit services in the peripheral areas and suburbs and increasing the integration level of muti-modes transferring in transport hubs. The findings will offer empirical evidence and reference value in developing cities globally

Inhibiting Mercury Re-emission and Enhancing Magnesia Recovery by Cobalt-Loaded Carbon Nanotubes in a Novel Magnesia Desulfurization Process

Mercury re-emission, because of the reduction of Hg²⁺ to form Hg⁰ by sulfite, has become a great concern in the desulfurization process. Lowering the concentrations of Hg²⁺ and sulfite in the desulfurization slurry can retard the Hg⁰ formation and, thus, mitigate mercury re-emission. To that end, cobalt-based carbon nanotubes (Co-CNTs) were developed for the simultaneous Hg²⁺ removal and sulfite oxidation in this work. Furthermore, the thermodynamics and kinetics of the Hg²⁺ adsorption and effect of Hg²⁺ adsorption on catalytic activity of Co-CNTs were investigated. Experimental results revealed that the Co-CNTs not only accelerated sulfite oxidation to enable the recovery of desulfurization by-products but also acted as an effective adsorbent of Hg²⁺ removal. The Hg²⁺ adsorption rate mainly depended on the structure of the adsorption material regardless of the cobalt loading and morphological distribution. The catalytic activity of the Co-CNTs for sulfite oxidation was not significantly affected due to the Hg²⁺ adsorption. Additionally, the isothermal adsorption behavior was well-fitted to the Langmuir model with an adsorption capacity of 166.7 mg/g. The mercury mass balance analysis revealed that the Hg⁰ re-emission was decreased by 156% by adding 2.0 g/L of Co-CNTs. These results can be used as a reference for the simultaneous removal of multiple pollutants in the wet-desulfurization process

MOF-Derived Robust and Synergetic Acid Sites Inducing C–N Bond Disruption for Energy-Efficient CO₂ Desorption

Amine-based scrubbing technique is recognized as a promising method of capturing CO2 to alleviate climate change. However, the less stability and poor acidity of solid acid catalysts (SACs) limit their potential to further improve amine regeneration activity and reduce the energy penalty. To address these challenges, here, we introduce two-dimensional (2D) cobalt–nitrogen-doped carbon nanoflakes (Co–N–C NSs) driven by a layered metal–organic framework that work as SACs. The designed 2D Co–N–C SACs can exhibit promising stability, superhydrophilic surface, and acidity. Such 2D structure also contains well-confined Co–N4 Lewis acid sites and −OH Brønsted acid sites to have a synergetic effect on C–N bond disruption and significantly increase CO2 desorption rate by 281% and reduce the reaction temperatures to 88 °C, minimizing water evaporation by 20.3% and subsequent regeneration energy penalty by 71.7% compared to the noncatalysis