Assessment of source-oriented health risk associated with the oral ingestion of heavy metals in dust within an iron/steel smelting-affected area of the North China Plain.

Heavy metals (HMs) from iron/steel smelting activities pose notable risks to human health, especially to those living around industrial facilities of North China Plain, the base of China's steel production. In this study, 78 outdoor windowsill dust samples were collected around a large-scale iron/steel smelter with more than 65 years of production history in the western North China Plain. Nine HMs were analysed to comprehensively assess the health risks by integrating Monte Carlo simulation, oral bioaccessibility, and source apportionment. Results showed serious pollution with Cd, Pb, and Zn based on their geo-accumulation index values and concentrations. Four potential sources including industrial sources (49.85%), traffic sources (21.78%), natural sources (20.58%), and coal combustion (7.79%) were quantitatively identified by multivariate statistical analysis. The oral bioaccessibilities of HMs determined by the physiologically based extraction test ranged from 0.02% to 65.16%. Zn, Mn, Cd, and Pb had higher bioaccessibilities than other HMs. After incorporating oral bioavailability adjustments, noncarcinogenic and carcinogenic risks were significantly reduced, especially for adults. The mean hazard index (HI) for children and adults was below the safety threshold (1.0), whereas the mean of the total carcinogenic risk (TCR) based on HM bioaccessibilities in the gastric phase remained above the acceptable level (1.0E-06) (children: 5.20E-06; adults: 1.16E-06). Traffic sources warranted increased concern as it substantially increased TCR. Cd was identified as the priority pollution in iron/steel smelting areas. Assessing source-oriented health risks associated with oral ingestion exposure can guide the management and control of HM contamination within iron/steel smelting-affected areas.

Effects of montmorillonite on the adsorption of Fe(II) by ferrihydrite and its phase transformation at different pH.

Recently, there has been a clear understanding of the mechanism and influencing factors of ferrihydrite (Fh) phase transformation catalyzed by Fe(II); however, these factors mainly belong to environmental conditions and exogenous substances. And there is a lack of research on the effect of soil composition and structure on the phase transformation of Fh. Therefore, this study investigated the effects of montmorillonite (Mt) on the adsorption of Fe(II) and phase transformation of Fh under near-neutral pH. The initial rates ([Formula: see text]) of Elovich equation demonstrated the addition of Mt inhibited the adsorption of Fh but simultaneously accelerated the initial adsorption, thus increasing the adsorption of the system (e.g., 22.09-25.03 mg/g as increased Mt under pH 6.5) due to its high surface charge density. Increased pH enhances the surface charge density by promoting the deprotonation of the surface group (Fe-OH, Al-OH, and Si-OH) and consequently increases adsorption of Fe(II) (e.g., 17.97-22.09 mg/g as increased pH of pure Fh). Based on the previous method of extracting labile Fe(III), we found that pH promotes the initial formation of labile Fe(III) by increasing electron transfer and promoting recrystallization caused by bridging condensation, via increased -OH. Although Mt inhibits the adsorption of Fh, it promotes the formation of labile Fe(III) by increasing the system adsorption and bond with Fh. The results of the analysis of variance showed both pH and solid ratio influence significantly on the maximum adsorption (p = 6.81 × 10-9 and 2.54 × 10-3) and the conversion ratios of labile Fe(III) (p = 3.43 × 10-24 and 9.16 × 10-43).

Study on adsorption of phosphate from aqueous solution by zirconium modified coal gasification coarse slag.

Zr-modified materials have an adsorption affinity for phosphate ions, but because of the cost of carrier materials, they are difficult to apply on a large scale. Herein, coal gasification coarse slag (CGCS) was used as a carrier material and modified with Zr, and its dephosphorization performance was studied. A series of adsorbents with different CGCS/ZrOCl2·8H2O mass ratios were prepared, from which the adsorbent with a CGCS/ZrOCl2·8H2O mass ratio of 5 : 4 (denoted as CGCS-Zr4) was identified as the most promising for phosphate adsorption. The specific surface area of CGCS-Zr4 was much greater than that of raw CGCS (100.12 vs. 12.43 m2 g-1). CGCS-Zr4 showed good adsorption selectivity towards phosphate when competitive anions co-existed, and exhibited good reusability; the adsorption capacity in the fourth adsorption-desorption cycle remained above 11.98 mg g-1. The adsorbent was also suitable for the continuous treatment of up to 830 and 743 bed volumes of synthesised and actual wastewater, respectively. The results of Fourier-transform infrared and X-ray photoelectron spectroscopy indicated that CGCS not only plays the role of a carrier, but also that Ca and Al in CGCS play an important role in phosphate adsorption. Compared with other carrier materials such as biochar and synthetic zeolite, CGCS has the advantages of a large stockpile, low cost, and easy availability. In addition, the preparation of CGCS-Zr4 is simpler and more energy-saving. Zr-modified CGCS is a promising dephosphorization material.

Cysteine enhanced degradation of monochlorobenzene in groundwater by ferrous iron/persulfate process: Impacts of matrix species and toxicity evaluation in ISCO.

Monochlorobenzene (MCB), a solvent and synthetic intermediate, has been widely detected in groundwater at industrial contaminated sites. Cysteine (Cys) enhanced Fe2+/persulfate (Fe2+/Cys/PS) process with high degradation efficiency of organic pollutants has the potential for in-situ chemical oxidation of MCB. In this study, we systematically explored the impacts of common anions (CO32-, HCO3-, SO42-, NO3-, NO2-, PO43-, HPO42-, H2PO4-, Cl-, Br-), cations (NH4+, Mg2+, Al3+, Mn2+, Cu2+) and natural organic matter (NOM) on the degradation kinetics of MCB by the novel Fe2+/Cys/PS process and evaluated the ecotoxicity. The results showed that the removal of MCB in absence of matrices was enhanced by Cys due to its reduction and complexation ability. All of the anions inhibited the MCB degradation through the scavenging of SO4•- and HO•, though the inhibition degree of SO42-and NO3- was slight. Cations such as NH4+, Mg2+ and Al3+ hardly interfered with the reaction. Low concentrations of Cu2+ and NOM promoted the MCB oxidation, but the promotion strength weakened and turned into inhibition with the increased concentration of Cu2+ and NOM. The toxicity assessment of the transformation products (TPs) in the presence of Cl- and Br- based on the quantitative structure-activity relationships model showed the potentially higher toxicity of some TPs than their parent MCB. These results indicate that groundwater matrices may interfere with the MCB oxidation process. To accurately evaluate the effects of groundwater matrices on Fe2+/Cys/PS process for MCB oxidation and its potential toxicity, the field tests should be carried out in the future.