Noise Exposure Assessment at a Secondary School in a City of Pulau Pinang, Malaysia

Schools are considered sensitive areas to noise pollution. The objective of this study is to ascertain the sound level in schools with respect to different sampling time sessions and sampling points. Five sampling points, consisting of two classrooms (Classroom A and Classroom B), a canteen, a staffroom and a field, were chosen to obtain an overview of the noise level within the whole school in three different time sessions (morning, afternoon and evening), as well as 8-h continuous sampling in both classrooms and the staffroom. The average noise level (L_Aeq,10min) obtained in this school was found to be in the range of 48.8 dBA to 83.7 dBA, where most of the values exceeded the permissible maximum sound pressure level set by the Malaysian Department of Environment (DOE). Classroom B recorded the highest average noise level (L_Aeq,8h) of 77.9 dBA, which exceeded the maximum value set by the Department of Environment.

Earthworms as plug flow reactors: a first-order kinetic study on the gut of the vermicomposting earthworm Eudrilus eugeniae

Earthworms are commonly referred as environmental engineers and their guts are often compared with chemical reactors. However, modeling experiments to substantiate it are lacking. The aim of this study was to use established reactor models, particularly PFR, on the gut of the vermicomposting earthworm Eudrilus eugeniae to understand more on its digestion. To achieve the objective, a mathematical model based on first-order kinetics was framed and used to determine the pattern of digestion rates of nutrient indicators, namely total carbon (%), total nitrogen (%), C/N ratio, ¹³C (‰), and ¹⁵N (‰) at five intersections (pre-intestine, foregut, midgut A, midgut B, and hindgut) along the gut of E. eugeniae. The experimental results revealed that the concentrations of TC, TN, ¹³C, and ¹⁵N decreased during gut transit, whereas C/N ratio increased. The first-order model demonstrated that all the nutrients exhibit a linear pattern of digestion during gut transit, which supports the PFR model. On this basis, the present study concludes that the gut of E. eugeniae functions as PFR.