Embedment of Ag(I)-organic frameworks into silica gels for microextraction of polybrominated diphenyl ethers in soils.

Three Ag(I)-organic frameworks, [Ag5(pydc)2(CN)]n, {[Ag4(pydc)2]CH3CN}n, and [Ag(4,4'-bpy)NO3]n, were synthesized and embedded into silica gels to form metal-organic-framework (MOF)-embedded gels for the microextraction of polybrominated diphenyl ethers (PBDEs) in soils. Despite the great differences in the structures of the organic ligands, all three Ag(I)-organic frameworks were found to effectively accumulate and concentrate PBDEs from sample solutions prepared with contaminated soil and purified water, indicating the important roles of Ag centers in PBDE extraction. Under the optimal experimental conditions (MOF mass, water volume, temperature, extraction time, and back-extraction time) for PBDE extraction from sample solutions, the detection limits of seven PBDEs (BDE-28, 47, 99, 100, 153, 154, and 183) ranged from 0.01 to 2.6ngg(-1) for [Ag5(pydc)2(CN)]n, 0.20-0.64ngg(-1) for {[Ag4(pydc)2]CH3CN}n, and 0.60-3.08ngg(-1) for [Ag(4,4'-bpy)NO3]n. The reproducibilities of the three methods were all satisfactory with relative standard deviations (RSDs) in the range of 2.2-9.6%, 5.3-10.4%, and 6.9-9.4% for [Ag5(pydc)2(CN)]n, {[Ag4(pydc)2]CH3CN}n, and [Ag(4,4'-bpy)NO3]n, respectively. The use of Ag(I)-organic frameworks for the microextraction of PBDEs was validated using both certified reference soils and field-contaminated soils, and the proposed methods are recommended as rapid and environmentally friendly alternatives for the extraction and determination of PBDEs in soils.

[Research on the Screening Method of Soil Remediation Technology at Contaminated Sites and Its Application].

Soil remediation technology screening is an important procedure in the supervision of contaminated sites. The efficiency and costs of contaminated site remediation will be directly affected by the applicability of soil remediation technology. The influencing factors include characteristics of contaminants, site conditions, remediation time and costs should be considered to determine the most applicable remediation technology. The remediation technology screening was commonly evaluated by the experienced expert in China, which limited the promotion and application of the decision making method. Based on the supervision requirements of contaminated sites and the research status at home and abroad, the screening method includes preliminary screening and explicit evaluation was suggested in this paper. The screening index system was constructed, and the extension theory was used to divide the technology grade. The extension theory could solve the problem of human interference in the evaluation process and index value assignment. A chromium residue contaminated site in China was selected as the study area, and the applicable remediation technologies were suggested by the screening method. The research results could provide a scientific and technological support for the supervision and management of contaminated sites in China.

Separations of substituted benzenes and polycyclic aromatic hydrocarbons using normal- and reverse-phase high performance liquid chromatography with UiO-66 as the stationary phase.

Metal-organic frameworks (MOFs) have great potential for applications in chromatography due to their highly tailorable porous structures and unique properties. In this work, the stable MOF UiO-66 was evaluated as both a normal-phase (NP-) and a reverse-phase (RP-) stationary phase in the high performance liquid chromatography (HPLC) to separate substituted benzenes (SBs) and polycyclic aromatic hydrocarbons (PAHs). It was found that the mobile phase composition has a significant effect on the HPLC separation. Baseline RP-HPLC separations of xylene isomers; naphthalene and anthracene; naphthalene and chrysene; and naphthalene, fluorene, and chrysene were achieved using MeOH/H2O ratios of 80:20, 75:25, 85:15, and 75:25, respectively, on the UiO-66 column. Similarly, baseline NP-HPLC separations of xylene isomers and ethylbenzene; ethylbenzene, styrene, o-xylene, and m-xylene; and several PAHs were also obtained on the UiO-66 column with different mobile phase compositions. The relative standard deviations (RSDs) of retention time, peak height, peak area, and half peak width for five replicate separations of the tested analytes were within the ranges 0.2-0.4%, 0.2-1.6%, 0.7-3.9%, 0.4-1.1%, respectively. We also evaluated other critical HPLC parameters, including injected sample mass, column temperature, and the thermodynamic characters of both the RP-HPLC and the NP-HPLC separation processes. It was confirmed that the separation of SBs on a UiO-66 column was an exothermic process, controlled by both enthalpy change (ΔH) and entropy change (ΔS). The reverse shape selectivity, size selectivity, stacking effect, and electrostatic force played vital roles in the separations of these analytes. To the best of our knowledge, this method is one of the very few examples of using MOFs as the stationary phase in both NP-HPLC and RP-HPLC. MOF-based stationary phases may thus be applied in the separations and analyses of SBs and PAHs in environmental samples.

[Research of early-warning method for regional groundwater pollution based on risk management].

Groundwater is the main source of water supply in China, and China's overall situation of groundwater pollution is not optimistic at present. Groundwater pollution risk evaluation and early-warning are the effective measures to prevent groundwater pollution. At present, research of groundwater early-warning method at home and abroad is still at the exploratory stage, and the sophisticated technology has not been developed for reference. This paper briefly described the data and technological demand of the early-warning method in different scales, and the main factors influencing the early-warning results of groundwater pollution were classified as protection performance of geological medium, characteristics of pollution sources, groundwater dynamics and groundwater value. Then the main early-warning indexes of groundwater pollution were screened to establish the early-warning model of regional or watershed scale by the index overlay method. At last, the established early-warning model was used in Baotou plain, and the different early-warning grades were zoned by the model. The research results could provide scientific support for the local management department to protect the groundwater resources.

Application of portable gas chromatography-photo ionization detector combined with headspace sampling for field analysis of benzene, toluene, ethylbenzene, and xylene in soils.

A method based on headspace (HS) sampling coupling with portable gas chromatography (GC) with photo ionization detector (PID) was developed for rapid determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in soils. Optimal conditions for HS gas sampling procedure were determined, and the influence of soil organic matter on the recovery of BTEX from soil was investigated using five representative Chinese soils. The results showed that the HS-portable-GC-PID method could be effectively operated at ambient temperature, and the addition of 15 ml of saturated NaCl solution in a 40-ml sampling vial and 60 s of shaking time for sample solution were optimum for the HS gas sampling procedure. The recoveries of each BTEX in soils ranged from 87.2 to 105.1 %, with relative standard deviations varying from 5.3 to 7.8 %. Good linearity was obtained for all BTEX compounds, and the detection limits were in the 0.1 to 0.8 µg kg(-1) range. Soil organic matter was identified as one of the principal elements that affect the HS gas sampling of BTEX in soils. The HS-portable-GC-PID method was successfully applied for field determination of benzene and toluene in soils of a former chemical plant in Jilin City, northeast China. Considering its satisfactory repeatability and reproducibility and particular suitability to be operated in ambient environment, HS sampling coupling with portable GC-PID is, therefore, recommended to be a suitable screening tool for rapid on-site determination of BTEX in soils.

The use of copper(II) isonicotinate-based micro-solid-phase extraction for the analysis of polybrominated diphenyl ethers in soils.

A micro-solid-phase extraction (µ-SPE) device was developed by filling copper(II) isonicotinate coordination polymer (Cu(4-C(5)H(4)N-COO)(2)(H(2)O)(4)) into a porous polypropylene envelope, and the µ-SPE, coupling with gas chromatography (GC) with a micro-cell electron capture detector (µ-ECD), was used for extraction and determination of PBDEs in soils. Variables affecting extraction procedures, including temperature, water volume, extraction time, and desorption time, were investigated in a spiked soil, and the parameters were optimized. Under the optimal experimental conditions, the method detection limits for seven PBDEs (BDE-28, 47, 99, 100, 153, 154, and 183) were in the range of 0.026-0.066 ng g(-1), and the reproducibility was satisfactory with the relative standard deviation in range of 1.3-10.1%. Good linear relationship between PBDEs concentrations and GC signals (defined as peak area) was obtained in the range between 0.1 and 200 ng g(-1). The recovery of the seven PBDEs by µ-SPE varied from 70 to 90%, which was comparable to that determined by accelerated solvent extraction method. Finally, the proposed method was used to determine PBDEs in several field-contaminated soils, and it was suggested that the µ-SPE is a promising alternative microextraction technique for the detection of PBDEs in soils.

[Chemical speciation of rare metals in three natural soils of China].

Soil profile samples of isohumosol, primosol, and ferrosol were obtained in relatively clean areas of China. Concentrations and chemical speciation of rare metals [e.g., Ag (Silver), Bi (Bismuth), In (Indium) and Sn (Tin)] were determined, in which sequential extraction was used to fraction metals. Vertical distributions of elemental enrichment ratios (ERs) were used to study the anthropogenic influence. The mobility of metals was characterized by the sum of exchangeable form and carbonate-bound form. Average concentrations of Ag, Bi, In and Sn in the A horizon were (0.14 +/- 0.01), (0.49 +/- 0.09), (0.050 +/- 0.01), and (2.8 +/- 0.9) mg x kg(-1), respectively. The ERs were close to 1. Average distributions of metal speciation were: Ag, residual (65.8%) > H202-extractable organically bound (H2O2-Org) (25.9%) > Amorphous metal oxide-bound (am-MeOx) (4.2%) > Metal-organic complex-bound (Me-Org) approximately Crystalline Fe oxide-bound (cr-FeOx) (2.0%); Bi, residual (29.2%) > H2O2-Org (27.1%) > cr-FeOx (22.7%) > am-MeOx (18.8%) > Me-Org (1.0%) > carbonate-bound (0.9%) > easily reducible metal oxide-bound (re-MeOx) (0.3%); In, residual (67.8%) > cr-FeOx (17.0%) > am-MeOx (6.8%) > H2O2-Org (6.0%) > carbonate-bound (1.4%) > Me-Org (1.0%); Sn, residual (58.1%) > am-MeOx (23.0%) > cr-FeOx (15.6%) > H2O2-Org (1.8%) > Me-Org (1.1%) > exchangeable approximately carbonate-bound (0.2%). the results indicated that the exogenous elements enrichment was deficiency to minimal, and the concentrations of the rare metals were close to background values of soil in studied areas. Rare metals were stable in soils. The mobility of metals was in the order In > Bi > Sn > Ag.

[Adsorption behavior and speciation transformation of Ag+ in phaeozem and red soil].

The batch equilibration experiments were carried out to study the adsorption characteristics of Ag+ and the effect of pH on the adsorption process in two typical Chinese soils, which the phaeozem from Northeast China and the red soil from Hunan province. The species transformation of Ag+ was investigated in the experiments using the sequential extraction method. The results showed that an adsorption quantity of Ag+ for both soils increased with increasing solutions initial pH. Adsorption quantity of Ag+ in the two soils also increased with increasing of initial Ag+ concentration in the range from 0 to 100 mg x L(-1), specifically, going up quickly in the concentration range of 0-20 mg x L(-1), but increased gently when Ag+ concentration exceeded 20 mg x L(-1). The Ag+ adsorption data of both soils were adequately described by Langmuir isotherm occurred in Ag+ sorption processes, their maximum adsorption quantities were 250 mg x kg(-1) the phaeozem soil and 88.5 mg x kg(-1) in the red soil, indicating a much higher adsorption capacity in northeast phaeozem soil than that of Hunan red soil. The two soils had similar adsorption kinetic characteristics, with respect to quickly reaching equilibrium within 30 minutes, but the adsorption rate of phaeozem soil was significantly greater than that of the red soil. The species analysis of Ag showed that exchangeable Ag and residual Ag increased in red soil, and metal-organic complex-bound Ag, exchangeable Ag, carbonate-bound Ag and residual Ag increased in phaeozem, respectively.

[Distribution of organochlorine pesticides in soils in Haihe River and Haihe Estuary area, China].

Levels and distribution of organochlorine pesticides (OCPs) were investigated in soils along Haihe River and in Haihe Estuary area. 31 surface soil samples were collected on August 2007, and they were extracted using accelerated solvent extraction. The HCHs and DDTs contents in soils were determined by gas chromatography with an electron capture detector (GC-ECD). The results show that the concentrations in soils range from n.d. to 1,728 microg x kg(-1) with a mean value of 93.9 microg x kg(-1) for HCH congeners, and from n.d. to 288 microg x kg(-1) with a mean value of 34.4 microg x kg(-1) for the sum of p,p'-DDT, o,p'-DDT, DDE, and DDD, respectively. The HCHs is dominant, accounting for 72 percent of total OCPs content. The working hypothesis is that OCPs levels and distribution in the area are dependent on the degree of anthropogenic intervention. Higher concentrations of total OCPs are found in the chemical industrial region, and ones from Haihe River area are higher than Haihe Estuary area, due to impact from chemical industrial emissions. According to the isomers of HCHs and metabolites of DDTs, HCHs and DDTs in soils in this area may be derived from the use of pesticide in agricultural and industrial emissions in history, though having recent inputs of OCPs at a few sites. Compared with those in other national or international regions, the concentrations of HCHs and DDTs in soils from Haihe River area are higher. It can be concluded that soil OCPs levels are relatively high in this area.

Exploration of coordination polymer as sorbent for flow injection solid-phase extraction on-line coupled with high-performance liquid chromatography for determination of polycyclic aromatic hydrocarbons in environmental materials.

The copper(II) isonicotinate (Cu(4-C5H4N-COO)2(H2O)4) coordination polymer was prepared, characterized and explored as sorbent for flow injection solid-phase extraction on-line coupled with high-performance liquid chromatography (HPLC) for determination of trace polycyclic aromatic hydrocarbons (PAHs) in environmental matrices. Naphthalene, phenanthrene, anthracene, fluoranthene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene and benzo(ghi)perylene with various shape, size and hydrophobicity were used as model analytes. The porosity of the coordination polymer allows these guest PAHs molecules to diffuse into the buck structure, and the shape and size of the pores lead to shape- and size-selectivity over the guests. The precolumn packed with the coordination polymer was shown to be promising for solid-phase extraction of PAHs in environmental samples with subsequent HPLC separation and UV detection. With extraction of 50 ml of sample solution, the enhancement factors for the PAHs studied ranged from 200 to 2337, depending on the shape, size and hydrophobic property of the PAHs. The detection limits (S/N = 3) of 2-14 ng l(-1) and the sample throughput of 3 samples h(-1) were obtained. The developed method was applied to the determination of trace PAHs in a certified reference material (coal fly ash) and local water samples.

Evaluation of expanded graphite as on-line solid-phase extraction sorbent for high performance liquid chromatographic determination of trace levels of DDTs in water samples.

Dichlorodiphenyltrichloroethane (DDT) and its metabolites are a typical kind of persistent organic pollutants (POPs). Development of a simple, cost-effective and sensitive methodology to monitor DDTs concentrations in water environment is of particular significance for understanding the fate and behavior of these pollutants. In this paper, a method on the basis of solid-phase extraction (SPE) using expanded graphite (EG) as sorbent coupled on-line with high performance liquid chromatography (HPLC) was developed for the determination of trace levels of p,p'-DDD (2,2-bis(4-chlorophenyl)-1,1-dichloroethane), p,p'-DDT, o,p'-DDT and p,p'-DDE (2,2-bis(4-chlorophenyl)-1,1-dichloroethene) in water. The analytes in water were preconcentrated onto the SPE column packed with expanded graphite, and subsequently eluted with methanol-water (90:10) mixed solvent. HPLC with a photodiode array detector was used for their separation and detection. The developed on-line solid-phase extraction protocol for HPLC permits the current HPLC separation and the next preconcentration proceeded in parallel, and thus allows one determination within 8min. The precision (R.S.D.) for 10 replicate injections of a mixture of 1mugl(-1) of each analyte was 3.2-6.2% for the peak area measurement. The detection limits (S/N=3) for preconcentrating 50ml of sample solution ranged from 10 to 25ngl(-1) at a sample throughput of 7.5samplesh(-1). The enhancement factors were about 700. The method was applied to the determination of trace p,p'-DDD, p,p'-DDT, o,p'-DDT and p,p'-DDE in local lake, river and tap water samples.