Dicofol application resulted in high DDTs residue in cotton fields from northern Jiangsu province, China

Dicofol with high impurity of DDT compounds is still widely used in agricultural practice such as cotton cultivation and becomes an important source of DDT pollution in China. In this study, investigations on the DDT residues in cotton fields from northern Jiangsu province, China were conducted. The results showed that DDTs in cotton soil were much higher than other mode of land use. The DDTs levels ranged from 4.2 to 678.6 ngg(-1), with a mean concentration of 190.4 ngg(-1), of which the most abundant compounds were p,p'-DDE (mean of 129.38 ngg(-1)), p,p'-DDT (mean of 26.57 ngg(-1)) and o,p'-DDT (mean of 16.92 ngg(-1)). The concentrations of o,p'-DDT and o,p'-DDE were significantly higher (p<0.05) in topsoil (0-10 cm) than in subsoil (10-20 cm), while other DDT compounds were not. Source apportionment showed that dicofol-type DDT accounted for up to 80% of the DDTs residue. All the results indicated that dicofol applications resulted in serious DDT pollution in cotton fields. Our work provided implications for reasons why there was no apparent decrease of DDT level in China.  

Effect of low-molecular-weight organic acids on the adsorption of norfloxacin in typical variable charge soils of China

Batch equilibrium experiments were used to study the adsorption of norfloxacin (NOR) onto three kinds of variable charge soils in China, namely Rho-Udic Ferralisols collected from Yunnan, Ali-Perudic Ferrisols collected from Jiangxi and Typ-Hap-Udic Ferralisols collected from Guangdong. Results show that NOR is strongly adsorbed by the soils, with lg Kd-values (linear model) of 4.41+/-0.01, 4.50+/-0.02, 4.44+/-0.01 and lg Kf-values (Freundlich model) of 4.32, 4.45, 3.08 for the three tested soils, respectively. Both curves of the Freundlich equation and Langmuir equation for the three soils were in excellent linear correlation. Low-molecular-weight (LMW) organic acids, including citric acid, malic acid and salicylic acid were added in the presence of acetate buffer (pH 4.5) to test their effects on NOR adsorption. It was observed that the addition of LMW organic acids inhibited the NOR adsorption process. It was assumed that several effects, including soil pH, solid surface charge and competitive adsorption of co-existing cations, dominated the NOR sorption processes onto variable charge soils. Further studies should be performed to reveal the mechanism of the adsorption.  

Solid/solution partitioning and speciation of heavy metals in the contaminated agricultural soils around a copper mine in eastern Nanjing city, China

Solid/solution partition coefficient (Kd) and speciation of soil heavy metals can be used for predicting their environmental risks. The Kd values and solution speciation of soil Cu, Cd and Zn were analyzed in 40 samples of contaminated agricultural soils around Jiuhua copper mine in eastern Nanjing city, China. The Kd ranges (and mean values) for soil Cu, Cd and Zn are 703-7418 (3453), 37.3-3963 (940) and 319-17965 (7244) L kg-1, respectively, showing a large variability both for metals and soils. The results of differential pulse anodic stripping voltammetry (DPASV) indicates that 95.6% solution Cu is bound to dissolved organic ligands. About half of the dissolved Zn is DPASV-labile at pH<6, while 92.1% solution Zn is in the form of organic complexes at pH>6. DPASV-labile Cd is ranged from 22.6 to 98.7% with the mean value of 56.3%. Multiple linear regressions indicate that Kd, the dissolved and DPASV-labile concentrations of Cd and Zn are mostly influenced by the soil solution pH with R2 of 0.50, 0.59 and 0.63, respectively for Cd, and 0.58, 0.72 and 0.64, respectively for Zn. Considering the second parameter of corresponding soil metal, the linear relationships of Kd with pH were improved with R2 of 0.70 and 0.73 for Cd and Zn, respectively. However, the solubility of soil Cu was insensitive to pH. Only SOC shows a weak relationship to the dissolved Cu with R2 of 0.21. As for its Kd, total soil Cu is the most significant factor. But for DPASV-labile Cu, no soil parameters were found to be good predictors.  

Reductive dechlorination of hexachlorobenzene by Cu/Fe bimetal in the presence of nonionic surfactant

This study investigated the enhancement of nonionic surfactant (TritonX-100, TX-100) on the reductive dechlorination of hexachlorobenzene (HCB) by microscale Cu/Fe bimetal. HCB reduction by Cu/Fe without TX-100, in aqueous TX-100, adsorbed with TX-100 and prepared with TX-100 was compared. Results showed that HCB reduction by Cu/Fe in aqueous TX-100 increased with increasing TX-100 concentration, reached a maximum of 98.6% when aqueous TX-100 concentration attained its critical micelle concentration (CMC), and decreased with the further increase in TX-100 concentration. The mechanism was suggested as the increased HCB mass transport at low TX-100 concentration below CMC and the coverage of reactive sites at high TX-100 concentration above CMC. The greatest reduction was achieved by Cu/Fe in the presence of 0.2 mM TX-100, followed by Cu/Fe adsorbed and prepared with 0.2 mM TX-100. Pentachlorobenzene and tetrachlorobenzene were found as the main dechlorination intermediates. Successive reduction by Cu/Fe in aqueous TX-100 solution could be maintained above 98% for four cycles. It is an alternative to use nonionic surfactants to enhance the reductive dechlorination of hydrophobic polychlorinated aromatic hydrocarbons (PCAH) by Cu/Fe bimetal.  

C-S-H凝胶的制备与性能研究

利用水热合成法制备了C-S-H凝胶,重点研究了不同的制备工艺、原材料与钙硅比对C-S-H凝胶结构的影响。经过详尽的X衍射(XRD)与核磁共振(NMR)分析表明,制备的样品都具备C-S-H凝胶的峰型特征;活性反应法相对于沉淀反应法制备的C-S-H凝胶层间距小、聚合度低;证实了C-S-H凝胶的层状结构,且层间距随钙硅比的增大而减小;Q~2/Q~2值与直链平均长度随钙硅比的增大而减小。  

Characteristics and accumulation of heavy metals in sediments originated from an electroplating plant

Heavy metals in river water and sediments originated from an electroplating plant in Jiangsu Province of China were studied and analyzed for their environmental impact. The results indicated that the wastewater from the plant degraded the quality of the aquatic environment downstream from the plant. In surface water, considerable concentrations of Cu, Ni, Zn, Mn and Cr were present at the sites near the plant. Unsafe levels of Cu were observed at all sites, and unsafe levels of Ni, Zn, and Cr were present at some sites. Significant accumulation of Ni, Cu, Zn and Cr was identified, and heavy metal longitudinal distribution in sediments was similar to that in water. The contents of Ni, Cu and Cr at all sites and Zn at some sites were likely to result in harmful effects on the environment. The risks posed by Ni, Cu, Zn and Cr in water and sediments decreased with increasing downstream distance. Moreover, a modified sequential extraction procedure was employed to determine exchangeable, carbonate-bound, iron-manganese oxide bound, organic matter bound and residual fractions of metals in sediments. The results showed that Ni was distributed in every fraction except for iron-manganese oxide bound, significant Mn exhibited in exchangeable fractions, and high percentage of Cu was in the organic matter and residual fractions. Residual fraction was the dominant fractions for Pb and Zn. According to RACs, Ni and Mn posed a high risk to the environment, Zn exhibited medium to high risk, Cu had low to high risk, and Pb possessed a low to medium risk.  

Effects of low-molecular-weight organic acids on Cu(II) adsorption onto hydroxyapatite nanoparticles

Adsorption kinetics and adsorption isotherms of Cu(II) onto a nanosized hydroxyapatite (HAP) in the absence and presence of different low-molecular-weight organic acids are studied in batch experiments. The results show that the adsorption kinetics of Cu(II) onto the HAP are best described by pseudo-second-order model, and the adsorption isotherms of Cu(II) onto the HAP fit Dubinin-Radushkevich model very well with high correlation coefficient (R(2)=0.97-0.99). The amount adsorbed of Cu(II) onto the HAP at pH 5.5 was much higher than that at pH 4.5. The presence of organic acids significantly decreased the adsorption quantity of Cu(II), clarifying the lower sorption affinities of Cu(II)-organic acid complexes onto the HAP rather than Cu(II) ion. The decreased maximal adsorption quantity of Cu(II) onto the HAP increased with the increasing logarithm of cumulative formation constants of Cu(II) and organic acids. The stronger coordination of organic acid with Cu(II), the more decreased Cu(II) adsorption quantity onto the HAP.  

Zinc adsorption on goethite as affected by glyphosate

Cosorption of metals with herbicides on minerals affects their mobility and their environmental effect. Batch experiments were conducted to evaluate the interaction between Zn and glyphosate [N-(phosphonomethyl)glycine (GPS; H3L)] with regard to the effect of GPS on Zn adsorption on goethite. The herbicide GPS markedly affected Zn adsorption on goethite when they coexisted in a goethite suspension. When solution pH was not intentionally adjusted, addition of GPS decreased Zn adsorption on goethite, since the equilibrium solution pH was significantly decreased in the presence of GPS and correspondingly the negative surface charges of goethite decreased. Zinc adsorption on goethite in the presence and absence of GPS at different pH of the equilibrium solution was studied in order to know if pH was the only variable for Zn adsorption with coexisting GPS. At lower pH (pH<5), the presence of GPS increased the adsorption of Zn, because Zn adsorbed on the sites of goethite via GPS bridge. However, at higher pH (pH>5), the presence of GPS decreased the adsorption of Zn on goethite, because GPS reacted with solution Zn to form water-soluble complexes that had lower affinity to the goethite surface in comparison with Zn itself. Zeta potential of goethite significantly decreased after adsorption of GPS, suggesting a chemical bond occurred between GPS and the mineral. FTIRs also show that GPS adsorbs on goethite by coordinating through caboxylate group.  

Characterization of soils using photoacoustic mid-infrared spectroscopy

This study investigates the use of photoacoustic spectroscopy (PAS) for rapid soil analysis. Photoacoustic spectroscopy requires very minimal sample preparation (air-drying), which is a major advantage compared to the more traditional transmittance technique, which requires time-consuming preparation of pellets. The amount of information contained in the PAS spectra appears to be similar to that contained in transmittance spectra, and the PAS spectra exhibit a large number of bands that can be associated with various soil constituents such as quartz, calcium carbonate, and various types of clay. Comparison with attenuated total reflection (ATR) spectra of saturated soil pastes shows that the PAS spectra provide much more information than the ATR spectra due to the strong water bands present in the latter. PAS quantitative analysis of clay, calcium carbonate, and organic matter is presented, with respective determination errors of approximately 12% clay, approximately 5% CaCO(3), and approximately 0.2% organic matter.  

Effects of sodium hypochlorite and high pH buffer solution in electrokinetic soil treatment on soil chromium removal and the functional diversity of soil microbial community

Effects of sodium hypochlorite (NaClO), applied as an oxidant in catholyte, and high pH buffer solution on soil Cr removal and the functional diversity of soil microbial community during enhanced electrokinetic treatments of a chromium (Cr) contaminated red soil are evaluated. Using pH control system to maintain high alkalinity of soil together with the use of NaClO increased the electrical conductivities of soil pore liquid and electroosmotic flux compared with the control (Exp-01). The pH control and NaClO improved the removal of Cr(VI) and total Cr from the soil. The highest removal percentages of soil Cr(VI) and total Cr were 96 and 72%, respectively, in Exp-04 when the pH value of the anolyte was controlled at 10 and NaClO was added in the catholyte. The alkaline soil environment and introduction of NaClO in the soil enhanced the desorption of Cr(VI) from the soil and promoted Cr(III) oxidation to mobile Cr(VI), respectively. However, the elevated pH and introduction of NaClO in the soil, which are necessary for improving the removal efficiency of soil Cr, resulted in a significantly adverse impact on the functional diversity of soil microbial community. It suggests that to assess the negative impact of extreme conditions for enhancing the extraction efficiencies of Cr on the soil properties and function is necessary.