Biochar (BC) and activated carbon (AC) were both produced from corn straw. Biochar-supported zerovalent iron (BC-ZVI) and activated carbon-supported zerovalent iron (AC-ZVI) were synthesized and applied for Se(IV)/Se(VI) removal. The sorption capacity of BC-ZVI for Se(IV) and Se(VI) was reported at 62.52 and 35.39 mg g?1, higher than that of AC-ZVI (56.02 and 33.24 mg g?1), respectively, due to its higher iron content and more positive charges. The spectroscopic analyses showed that Se(IV)/Se(VI) were reduced to Se(0)/Se(-II) of less toxicity and solubility. The effects of various factors such as pH, ionic strength, co-existing cations and anions, and natural organic matter (NOM) were also investigated. Ionic strength showed no significant effect on Se(IV)/Se(VI) removal, but pH was critical. The presence of NO3? and SO42? did not cause obvious inhibition to the removal, while PO43? inhibited the sorption capacity of BC-ZVI and AC-ZVI for Se(IV)/Se(VI) significantly. Common cations (K+, Ca2+, and Mg2+) were found to slightly enhance the removal, while NOM significantly decreased the sorption capacity of BC-ZVI and AC-ZVI for Se(IV)/Se(VI). Besides, NOM showed stronger inhibition effect on AC-ZVI than that on BC-ZVI. These results indicated that BC-ZVI, compared with AC-ZVI, could be a promising sorbent to remove Se(IV)/Se(VI) due to its low cost and high efficiency.
The aim of this study was to explore the association between NP exposure and parity and their effect on neonatal birth weight.
Methods
A cohort of pregnant women was established in a medical center in North Taiwan. Urinary NP concentration was determined by high-performance liquid chromatography coupled with fluorescent detection and adjusted using creatinine. A multivariable regression model was fit to determine the association between the maternal NP level in each trimester and neonatal birth weight. The odds ratios (ORs) of infant birth weight below the 10th, 25th, and 50th percentiles, comparing pregnant women with the different NP exposure levels, was estimated using a logistic regression.
Results
Of the 162 pregnant women in the study, 99 were multiparas and 63 were primiparas. After adjusting for other covariates, the NP level in the second trimester had a significant association with birth weight in the primiparas (β = −182.49 g, p value = 0.02). The OR of low infant birth weight, comparing pregnant women with different NP levels, was increased by decreasing the cutoff percentile for birth weight (OR = 1.18 for the 50th percentile, 2.12 for the 25th percentile, and 7.81 for the 10th percentile). The odds of primiparas with high NP level having a low neonatal birth weight increased to 3.87, 11.77, and 9.40 for the three different percentiles (p value < 0.05).
Conclusion
Maternal NP exposure level is associated with an increased risk of low neonatal weight. Primiparas are especially at risk, and the second trimester of pregnancy may be the critical stage of exposure. 相似文献