The contribution of moped emissions to ultrafine and fine particle concentrations on bike lanes

Tracking Airborne Pollution with Environmental Magnetism in A Medium-Sized African City

As in other parts of the world, air pollution over West and Central Africa has major health and meteorological impacts. Air quality assessment and its possible sanitary impact have become essential even in medium-sized towns, therefore amplifying the need for easy-to-implement monitoring methods with low environmental impact. We present here the potential of magnetic methods to monitor air quality at street level in the medium-sized city of Maroua (northern Cameroon) affected by dust-laden desert winds. More than five hundred (544) samples of bark and leaves taken from Neem trees in Maroua were analyzed. Magnetic susceptibility, saturation remanence, and S-ratio were found to determine the concentration and nature of magnetic particles. They are dominated by magnetite-like particle signals as a part of particulate emissions due to urban activities, including both traffic, composed of a substantial proportion of motorcycles, and wood burning for food preparation. We show that both bark and leaves from Neem trees are adequate passive bio-recorders. The use of both enables different times and heights to be sampled, allowing for the high-resolution monitoring, in terms of spatialization, of various urban environments. Particle emissions require assessment and screening that could be carried out rapidly and efficiently by magnetic methods on bio-recorders, even in cities impacted by dust-laden wind.

Trade-off between environmental benefits and time costs for public bicycles: An empirical analysis using streaming data in China

In recent years, bicycle sharing has become more popular in cities and towns around the world. Public bicycles are one of the important forms of bicycle sharing. The use of public bicycles instead of motor vehicles has brought about changes in environmental benefits for the society, and at the same time, it has also changed the travel time of residents. Because these changes are potential and cannot be measured directly, we put forward the calculation methods of environmental benefits and time costs of public bicycles according to the concept of opportunity cost. Taking Hohhot, the capital city of Inner Mongolia, as an example, according to the streaming data of 9.76×10⁶ valid orders of public bicycle trips in 2016, we found that the use of public bicycles could reduce consumption of standard coal by as much as 5,796.11 tons (accounting 0.16‱ of the total coal consumption in Inner Mongolia) and carbon emissions were reduced by 4,381.28 tons (accounting 0.30‱ of the total carbon emissions in Inner Mongolia). However, the promotion of public bicycles is not without disadvantages. The use of public bicycles has increased the average travel time of residents by 0.06 hours, which is neglected in previous studies. The contribution of public bicycles to saving 1kg standard coal corresponds to 0.10 hours of travel time waste. Thus, reducing 1kg of carbon emissions is corresponding to a waste of 0.14 hours of travel time. The use of public bicycles varies among different income groups, which is caused by the value of travel time. Low-income groups use more frequently than high-income groups. Generally speaking, low-income groups bring more environmental benefits to society through the use of public bicycles, but bear more time costs. Therefore, we propose a carbon tax on high-carbon transportation modes to encourage green travel and balance the environmental benefits and time costs of public bicycles.