Identification of iron and sulfate release processes during riverbank filtration using chemical mass balance modeling

Abstract. This study compares geochemical and physical methods of estimating baseflow in the upper reaches of the Barwon River, southeast Australia. Estimates of baseflow from physical techniques such as local minima and recursive digital filters are higher than those based on chemical mass balance using continuous electrical conductivity (EC). Between 2001 and 2011 the baseflow flux calculated using chemical mass balance is between 1.8 × 103 and 1.5 × 104 ML yr−1 (15 to 25% of the total discharge in any one year) whereas recursive digital filters yield baseflow fluxes of 3.6 × 103 to 3.8 × 104 ML yr−1 (19 to 52% of discharge) and the local minimum method yields baseflow fluxes of 3.2 × 103 to 2.5 × 104 ML yr−1 (13 to 44% of discharge). These differences most probably reflect how the different techniques characterise baseflow. Physical methods probably aggregate much of the water from delayed sources as baseflow. However, as many delayed transient water stores (such as bank return flow or floodplain storage) are likely to be geochemically similar to surface runoff, chemical mass balance calculations aggregate them with the surface runoff component. The mismatch between geochemical and physical estimates is greatest following periods of high discharge in winter, implying that these transient stores of water feed the river for several weeks to months. Consistent with these interpretations, modelling of bank storage indicates that bank return flows provide water to the river for several weeks after flood events. EC vs. discharge variations during individual flow events also imply that an inflow of low EC water stored within the banks or on the floodplain occurs as discharge falls. The joint use of physical and geochemical techniques allows a better understanding of the different components of water that contribute to river flow, which is important for the management and protection of water resources.

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Emission of PM2.5-Bound Polycyclic Aromatic Hydrocarbons from Biomass and Coal Combustion in China

Atmosphere ◽

10.3390/atmos12091129 ◽

2021 ◽

Vol 12 (9) ◽

pp. 1129

Author(s):

Xinghua Li ◽

Zihao Wang ◽

Tailun Guo

Keyword(s):

Polycyclic Aromatic Hydrocarbons ◽

Mass Balance ◽

Aromatic Hydrocarbons ◽

Coal Combustion ◽

Emission Factors ◽

Chemical Mass Balance ◽

Open Burning ◽

Coal Burning ◽

Receptor Modelling ◽

Polycyclic Aromatic

Field measured PAH emissions from diverse sources in China are limited or even not available. In this study, the PM2.5-bound PAH emission factors (EFs) for typical biomass and coal combustion in China were determined on-site. The measured total PAH EFs were 24.5 mg/kg for household coal burning, 10.5–13.9 mg/kg for household biofuel burning, 8.1–8.6 mg/kg for biomass open burning, and 0.021–0.31 mg/kg for coal-fired boilers, respectively. These EF values were compared with previous studies. The sources profiles of PAHs for four sources were developed to use in chemical mass balance receptor modelling. BaP equivalent EFs (EFBaPeq) were calculated to evaluate PAH emission toxicity among different combustion sources, and were 6.81, 2.94–4.22, 1.59–3.62, and 0.0006–0.042 mg/kg for those four types of sources, respectively.

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