Environ Sci Pollut Res DOI 10.1007/s11356-014-2701-6
RESEARCH ARTICLE
Hydroxypropyl-β-cyclodextrin extractability and bioavailability of phenanthrene in humin and humic acid fractions from different soils and sediments Huipeng Gao & Jing Ma & Li Xu & Lingyun Jia
Received: 13 December 2013 / Accepted: 24 February 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Organic matter (OM) plays a vital role in controlling polycyclic aromatic hydrocarbon (PAH) bioavailability in soils and sediments. In this study, both a hydroxypropyl-βcyclodextrin (HPCD) extraction test and a biodegradation test were performed to evaluate the bioavailability of phenanthrene in seven different bulk soil/sediment samples and two OM components (humin fractions and humic acid (HA) fractions) separated from these soils/sediments. Results showed that both the extent of HPCD-extractable phenanthrene and the extent of biodegradable phenanthrene in humin fraction were lower than those in the respective HA fraction and source soil/sediment, demonstrating the limited bioavailability of phenanthrene in the humin fraction. For the source soils/ sediments and the humin fractions, significant inverse relationships were observed between the sorption capacities for phenanthrene and the amounts of HPCD-extractable or biodegradable phenanthrene (p96 %, high-performance liquid chromatography (HPLC) grade) was purchased from Alfa Aesar. HPCD (purity >99 %) were purchased from Aladdin (China). Methanol, n-hexane, and acetone were of HPLC grade, and all other chemicals were of analytical grade. Milli-Q® water (Millipore, France) was used for the preparation of test solutions and reagents. Soil preparation and fractionation of HS A total of seven samples which contained varying levels of organic carbon (1.12–8.80 %) were collected and used for this study. Soil samples 1 and 2 were collected from the farmland in Jilin (China), soil 3 was collected from the farmland in Heilongjiang (China), and soil 4 was collected from the grassland in the campus of Dalian University of Technology. Sediment samples 1–3 were collected from Qing River, Liu River, and Chai River in Liaoning (China), respectively. The soil/sediment samples used in the study have not been polluted by PAHs. Each of the samples was passed through a 10mm sieve and air-dried. These were then passed through a 2mm sieve to remove roots and other vascular materials. The physical and chemical properties of the samples are listed in Table 1. The samples were then fractionated into FA, HA, and humin fractions using the classical base extraction procedure (Salloum et al. 2001). First, each sample was mixed with 0.1 M NaOH solution at a sample to NaOH ratio of 1:10 under nitrogen. The mixture was allowed to react at 25± 2 °C with shaking at 180 rpm for approximately 20 h. Next, the mixture was centrifuged at 4,000×g for 30 min to separate the solid material from the liquid. The solid material was again mixed with 0.1 M NaOH and extracted as described. This
Environ Sci Pollut Res Table 1 Physicochemical properties of soils/sediments Soil/sediment
Soil 1 Soil 2 Soil 3 Soil 4 Sediment 1 Sediment 2 Sediment 3 a
Organic carbon analyses
pH
foc (%)a
FHA (%)b
Fhumin (%)c
2.57 8.80 3.66 2.71 1.12 1.35 4.02
25.08 17.99 25.07 27.16 19.04 8.87 27.08
30.56 15.32 49.72 34.55 43.40 48.18 60.31
5.37 5.23 5.86 6.39 6.19 7.33 4.65
Particle size (%) Sand
Silt
Clay
14.6 18.6 21.5 35.3 12.4 10.7 36.0
52.0 48.9 58.7 44.4 78.7 80.0 60.0
33.4 32.6 19.7 20.3 8.9 9.3 4.0
The total organic carbon content of soil/sediment
b
Percentage of organic carbon content of HA to the total organic carbon
c
Percentage of organic carbon content of humin to the total organic carbon
extraction was repeated until no more organic material could be removed from the solid material. The precipitated solid was considered as humin fraction. All the supernatants obtained from the extraction with NaOH extraction were pooled and acidified with 6 M HCl to a pH0.9138). The sorption isotherms of phenanthrene to the bulk soils/sediments and the humin and HA fractions were nonlinear (N
RESEARCH ARTICLE
Hydroxypropyl-β-cyclodextrin extractability and bioavailability of phenanthrene in humin and humic acid fractions from different soils and sediments Huipeng Gao & Jing Ma & Li Xu & Lingyun Jia
Received: 13 December 2013 / Accepted: 24 February 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Organic matter (OM) plays a vital role in controlling polycyclic aromatic hydrocarbon (PAH) bioavailability in soils and sediments. In this study, both a hydroxypropyl-βcyclodextrin (HPCD) extraction test and a biodegradation test were performed to evaluate the bioavailability of phenanthrene in seven different bulk soil/sediment samples and two OM components (humin fractions and humic acid (HA) fractions) separated from these soils/sediments. Results showed that both the extent of HPCD-extractable phenanthrene and the extent of biodegradable phenanthrene in humin fraction were lower than those in the respective HA fraction and source soil/sediment, demonstrating the limited bioavailability of phenanthrene in the humin fraction. For the source soils/ sediments and the humin fractions, significant inverse relationships were observed between the sorption capacities for phenanthrene and the amounts of HPCD-extractable or biodegradable phenanthrene (p96 %, high-performance liquid chromatography (HPLC) grade) was purchased from Alfa Aesar. HPCD (purity >99 %) were purchased from Aladdin (China). Methanol, n-hexane, and acetone were of HPLC grade, and all other chemicals were of analytical grade. Milli-Q® water (Millipore, France) was used for the preparation of test solutions and reagents. Soil preparation and fractionation of HS A total of seven samples which contained varying levels of organic carbon (1.12–8.80 %) were collected and used for this study. Soil samples 1 and 2 were collected from the farmland in Jilin (China), soil 3 was collected from the farmland in Heilongjiang (China), and soil 4 was collected from the grassland in the campus of Dalian University of Technology. Sediment samples 1–3 were collected from Qing River, Liu River, and Chai River in Liaoning (China), respectively. The soil/sediment samples used in the study have not been polluted by PAHs. Each of the samples was passed through a 10mm sieve and air-dried. These were then passed through a 2mm sieve to remove roots and other vascular materials. The physical and chemical properties of the samples are listed in Table 1. The samples were then fractionated into FA, HA, and humin fractions using the classical base extraction procedure (Salloum et al. 2001). First, each sample was mixed with 0.1 M NaOH solution at a sample to NaOH ratio of 1:10 under nitrogen. The mixture was allowed to react at 25± 2 °C with shaking at 180 rpm for approximately 20 h. Next, the mixture was centrifuged at 4,000×g for 30 min to separate the solid material from the liquid. The solid material was again mixed with 0.1 M NaOH and extracted as described. This
Environ Sci Pollut Res Table 1 Physicochemical properties of soils/sediments Soil/sediment
Soil 1 Soil 2 Soil 3 Soil 4 Sediment 1 Sediment 2 Sediment 3 a
Organic carbon analyses
pH
foc (%)a
FHA (%)b
Fhumin (%)c
2.57 8.80 3.66 2.71 1.12 1.35 4.02
25.08 17.99 25.07 27.16 19.04 8.87 27.08
30.56 15.32 49.72 34.55 43.40 48.18 60.31
5.37 5.23 5.86 6.39 6.19 7.33 4.65
Particle size (%) Sand
Silt
Clay
14.6 18.6 21.5 35.3 12.4 10.7 36.0
52.0 48.9 58.7 44.4 78.7 80.0 60.0
33.4 32.6 19.7 20.3 8.9 9.3 4.0
The total organic carbon content of soil/sediment
b
Percentage of organic carbon content of HA to the total organic carbon
c
Percentage of organic carbon content of humin to the total organic carbon
extraction was repeated until no more organic material could be removed from the solid material. The precipitated solid was considered as humin fraction. All the supernatants obtained from the extraction with NaOH extraction were pooled and acidified with 6 M HCl to a pH0.9138). The sorption isotherms of phenanthrene to the bulk soils/sediments and the humin and HA fractions were nonlinear (N
