Ability of equilibrium and non-equilibrium models to simulate the effects of vermicompost and hydraulic conditions on nitrate and DOC leaching.

ABSTRACTThis study aims to model the effects of saturated-unsaturated flow rates and initial moisture content on nitrate and dissolved organic carbon (DOC) leaching in soils amended and unamended with vermicompost using equilibrium and non-equilibrium models. Flow rates ranging from 0.4 to 5.1 cm3/min were applied to the columns filled with the soils under initial saturated and air-dried conditions. The leaching of nitrate and DOC was simulated using a one-dimensional advection-dispersion model coupled with the equilibrium and non-equilibrium models. The accuracy of equilibrium without distribution coefficient (KD), equilibrium with KD, one-site, two-site and dual porosity models for modelling the nitrate leaching was 21.8, 33.6, 67.5, 82.2 and 83.9%, respectively, indicating the higher accuracy of dual porosity and two-site models compared to the other models. According to the results of the two-site model, the kinetic release was the most dominant process in all leaching experiments due to the fractions of equilibrium soil sites (F) < 0.5. Vermicompost decreased the diffusion coefficient (D0), distribution coefficient (KD), first-order rate constant (ß) and retardation factor (RF). In comparison to the air-dried condition, the initial saturated condition compared to the air-dried condition resulted in less F and D0, higher KD and RF lower ß for nitrate and lower KD and RF and higher ß for DOC. Leaching using a desaturation flow rate of 0.4 cm3/min was more time-dependent, which reduced RF values from 22.6 to 1.09 and 21.5 to 3.68 for nitrate and DOC, respectively. Moreover, the desaturation flow rate reduced D0 and KD and increased ß.

Contribution of outdoor noise-induced health risk in schools located in urbanized arid country.

Ambient noise pollution is deemed as one of the major growing public health issues, especially in developing countries. Therefore, it is crucial to assess the impact of noise pollution on public health. The aim of this study is to investigate the health risk of noise exposure levels in three schools: Kaab Bin Zeyd of Basic Education (school A), Hail Al-Awamour Girls school (school B), and Al-Fikr School (school C) in Muscat, Oman. The study employed a survey of 300 students, dose-response models, and regression models to quantify health risk and to determine the relationship between noise levels and perceived noise annoyance sources. The study found average noise levels (LAeq) of school A (70.03±8.21 dBA), school B (69.54±7.75 dBA), and school C (55.95± 5.67 dBA) to be higher than WHO's outdoor schools environment standard of 55 dBA and European (EN16798-1) classroom's critical limits of 30-34 dBA. Most of the students from schools A (30.9%), B (33.3%), and C (63%) have reported noise produced from traffic as extremely annoyed compared to aircraft of 15.4%, 11.5%, and 27.2%, respectively. Regression analysis shows that perceived traffic noise was strongly correlated with LAeq in school A (R2 =0.481), B (R2 =0.121), and C (R2 = 0.132) when compared with other subjective noise types. The health risk assessment results show that the percentage of highly annoyed (%HA) was higher in school A (15.2%) and school B (14.95%) than in school C (8.18%). The estimated highly sleep disturbed (%HSD) based on mean noise levels were almost the same in schools A (15.62%) and B (15.19%) but far higher compared to school C (6.01%). However, there was an association between the mean noise exposure levels and the risk of developing ischemic heart diseases (IHD) in school A (RR= 1.172, 95% CI: 1.020-1.334), school B (RR=1.167, 95% CI: 1.020-1.325), and school C (RR=1.051, 95% CI: 1.006-1.095). Moreover, attributable risk percentage (AR%) for school A (AR% =14.675, 95% CI: 2.028-25.037), school B (AR% =14.310, 95% CI: 1.960-24.528), and school C (AR% = 4.852, 95% CI:0.596-8.742) have shown that a substantial portion of the population could be prevented from developing IHD. It is expected that findings of the study can be applied in other arid regions with sprawl urbanized built environments.

A critical review of environmental and public health impacts from the activities of evaporation ponds.

Evaporation ponds (EVPs) are among the most cost-effective, and simple wastewater treatment technologies used in many regions/countries with high solar radiation levels. However, its operational limitations, which include the overflow of wastewater, leakages via liners, and large surface area of the EVP that is exposed to atmosphere, creates a negative feedback to the environment. Therefore, the main aim of this review study of more than a hundred works published a little all over the continents is to provide a summary of various contaminations that are associated with EVPs activities through different environmental compartments. In addition, the impacts of EVP on fauna, human health including the current on-site sustainable mitigation strategies were also reviewed. The first conclusion from this study shows that the most commonly contaminants released into surface waters, groundwater, soil and sediments were heavy metals, pesticides, herbicides, selenium, including several major anions and cations. Non-methane hydrocarbons (NMHCs), volatile organic compounds (VOCs), and particulate matters (PMs) were the main air pollutants emitted from the surfaces of an EVP. Limited data is available about the emissions of atmospheric greenhouse gas (GHGs) especially carbon dioxide (CO2) and methane (CH4) from EVP surfaces. Migratory birds and aquatic organisms are the most vulnerable fauna as EVP wastewaters can cause obstruction of movements, affect diversity, and causes mortalities following the exposure to the toxic wastewater. The study revealed limited data about the potential health risk associated with occupational and environmental exposure to radiological hazards and contaminated drinking water from EVP activities. On-site EVP treatment strategies using bioremediation and electrochemical treatment technologies have shown to be a promising sustainable mitigation approach. Knowledge gaps in areas of GHGs monitoring/modeling, pollution exposure estimation and health risk assessments are urgently required to gain deeper understanding about the impact of EVP activities, and incorporate them into future EVP designs.