| 1. |
- Islam, M. Shahidul, et al.
(författare)
-
Coprostanol adsorption behavior in agricultural soil, riverbed sediment, and sand
- 2023
-
Ingår i: Journal of Environmental Chemical Engineering. - 2213-3437. ; 11:3
-
Tidskriftsartikel (refereegranskat)abstract
- The occurrence of coprostanol in soil, surface, and groundwater has recently been reported in several studies. Coprostanol indicates the presence of feces from mammals. For this reason, it is important to establish adsorption behavior in different kinds of geologic media. To our knowledge, we present for the first-time adsorption behavior of coprostanol in soil, sediment, and sand and an estimation of its potential bioavailability, fate, and transport behavior. Adsorption experiments were conducted in agricultural soil, riverbed sediment, and sandy soil samples. The Henry model fitted experimental adsorption curves best for soil and sediment samples. Henry adsorption coefficients (KD) were 193.7 L kg−1 for soil, 120.8 L kg−1 for sediment, and 94.8 L kg−1 for sand, which suggests that the adsorption of coprostanol is different in soil (high absorption), sediment (medium), and sand (low). Further, results showed that the Freundlich model fits observed adsorption better as compared to the Langmuir model, indicating that the sorption process is of the multilayer type for the heterogenous surface of soil sample. The Langmuir model fitted best the adsorption in sediment, and sand. This supports the hypothesis that the process here is of a monolayer adsorption type. The mean maximum sorption capacity estimated by the Langmuir model was 345.1 µg g−1 for soil, 133.2 µg g−1 for sediment, and 80.9 µg g−1 for sand. The high adsorption capacity of coprostanol in soil is predominantly controlled by organic matter, high CEC, clay content, possible intermolecular H-bonding, and hydrophobic interaction. The organic carbon content normalized sorption coefficient (KOC) revealed that coprostanol is considered a sub-high adsorbed and slightly mobile compound that has leaching properties and can migrate to groundwater posing potential risks to the groundwater system.
|
|
| 2. |
- Nakagawa, Kei, et al.
(författare)
-
On the use of coprostanol to identify source of nitrate pollution in groundwater
- 2017
-
Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 550, s. 663-668
-
Tidskriftsartikel (refereegranskat)abstract
- Investigation of contaminant sources is indispensable for developing effective countermeasures against nitrate (NO3 −) pollution in groundwater. Known major nitrogen (N) sources are chemical fertilizers, livestock waste, and domestic wastewater. In general, scatter diagrams of δ18O and δ15N from NO3 − can be used to identify these pollution sources. However, this method can be difficult to use for chemical fertilizers and livestock waste sources due to the overlap of δ18O and δ15N ranges. In this study, we propose to use coprostanol as an indicator for the source of pollution. Coprostanol can be used as a fecal contamination indicator because it is a major fecal sterol formed by the conversion of cholesterol by intestinal bacteria in the gut of higher animals. The proposed method was applied to investigate NO3 − pollution sources for groundwater in Shimabara, Nagasaki, Japan. Groundwater samples were collected at 33 locations from March 2013 to November 2015. These data were used to quantify relationships between NO3-N, δ15N-NO3 −, δ18O-NO3 −, and coprostanol. The results show that coprostanol has a potential for source identification of nitrate pollution. For lower coprostanol concentrations (<30 ng L−1) in the nitrate-polluted group, fertilizer is likely to be the predominant source of NO3 −. However, higher concentration coprostanol samples in the nitrate-polluted group can be related to pollution from livestock waste. Thus, when conventional diagrams of isotopic ratios cannot distinguish pollution sources, coprostanol may be a useful tool.
|
|
