Comparative Study on the Elucidation of Sedimentary Phosphorus Species Using Two Methods, the SMT and SEDEX Methods.

Sedimentary phosphorus (P) forms are important representatives of P sources and their bioavailability as well as the potential of sediments to release P in water. In this study, surface sediments along a transect of the Changjiang Estuary and two transects along the Andong salt marsh in the southwest of Hangzhou Bay were subjected to the elucidation of sedimentary P species using the standards, measurements, and testing (SMT) and sequential extraction (SEDEX) methods. The results showed that the mean sedimentary P forms elucidated by the SMT method were as follows: organic P (OP; ∼11-14 mg/kg; ∼30-45% of total P; TP) > apatite P (∼5-15 mg/kg; ∼21-36% TP) > Fe/Al-P (∼8-14 mg/kg; ∼31-34% TP), with inorganic P (IP) composing 54-70% of TP. The mean sedimentary P forms elucidated by the SEDEX method were as follows: authigenic P (∼54-68 mg/kg; ∼41-46% TP) > extractable P (Ex-P; ∼36-53 mg/kg; ∼28-34%) > Fe-P (∼21-27 mg/kg; ∼13-19%) > OP (∼8.7-13 mg/kg; ∼5-8%) > detrital P (De-P; ∼2 mg/kg; ∼1-2% TP), with IP composed of ∼91-94% TP. These results showed that the SEDEX method elucidated higher concentrations of sedimentary P forms as well as the TP from these coastal sediments although the SMT method had the advantage of being more economic and faster. The results of both the SMT and SEDEX methods showed that the Andong salt marsh and Changjiang Estuary sediments had much bioavailable P. The mean percentages of bioavailable P from the SMT and SEDEX methods were ∼64-74% and 52-56% of TP, respectively, indicating that these sediments were prone to release P to the coastal areas.

[Simultaneous remediation of Cr (VI) and p-NCB by nanosacle iron].

Nanoscale Fe and Ni/Fe, which were prepared by chemical deposition, were utilized as catalyst for remediation of Cr(VI) and pNCB in contaminated water. The interactions between Cr( VI) and p-NCB in contaminated water during the simultaneous remediation process were analyzed. It is demonstrated from the experiment that p-NCB can be degradated into p-CAN by nanoscale iron, but cannot exhibit the effect of dechlorination, and that there is a competitive relationship between Cr( VI) and p-NCB in the remediation process. The nanoscale Nil Fe bimetals could be applied in simultaneous remediation of p-NCB with Cr( VI) and give rise to a good remediation efficiency, where the products are only Cr(III) and p-CAN without any intermediate products. It was found that the conditions of higher Ni(II) concentration can promote the degradation rate of p-NCB. The optimum Ni/Fe ratio is 1:50. Whereas, the higher concentrations of Cr(VI) and p-NCB will lead to the lower degradation rate. Under the condition that concentration of Cr (VI) was 20 mg/L, the corresponding maximum dechlorination of p-NCB was 43.0%; under the condition that concentration of p-NCB was 40 mg/L, the corresponding maximum removal efficiency of Cr(VI) was 71.4%.

[Water environmental simulation of main contaminations in the Qiantang River at low water period].

Technical framework for water environment simulation of contaminations is established based on visualization and a spatial environmental model is built. The main two contaminations, namely NH: -N and TP, are simulated on the platform of MapInfo and Delft3D in the Qiantang River at the low water period, to analyze its space-time diversity. For NH4+ -N, the measured values are 0.19 mg/L and 0.66 mg/L larger than simulated values at the Lanjiang River mouth and the Yanlingwu, 0.16 mg/L, 0.54 mg/L and 0.49 mg/L smaller at the Zhaixi, the Yushan and the Yuanpu. For TP, the measured values are 0.13 mg/L and 0.14 mg/L higher than simulated values at the Meicheng Water facility and Yanlingwu. However, the measure values are slightly lower than simulated ones at Zhaixi, Yushan, Puyang River mouth and Yuanpu, the trend of which accords with actual situation. The results indicate that the contaminations of the Qiantang Reach mostly come from the Lanjiang River, the Fuchun River and the Puyang River on the upstream, among which the Lanjiang River and the Puyang River have a very high concentration of polluted materials, which means bad water quality, and influence the water downstream. The Lanjiang River becomes the chief contaminative source in the Fuchun River. When the discharge from the Xin'an River Dam is small, the recirculation region may be formed and makes part of the Xin'an Reach contaminated. Otherwise, when the discharge is large, the water quality in the Fuchun River is apparently improved. And the Puyang River, which brings the contaminations from the upstream, along with the polluted water let into it from the industries along the reach, has significant impacts on the water quality in Qiantang Reach.

Structure relationship of nitrochlorobenzene catalytic degradation process in water over palladium-iron bimetallic catalyst.

Two isomers of nitrochlorobenzene (o-, and p-NCB) were treated by a Pd/Fe catalyst in aqueous solutions through catalytic amination and dechlorination. Nitrochlorobenzenes are rapidly converted to form chloroanilines (CAN) first through an amination process, and then rapidly dechlorinated to become aniline (AN) and Cl(-), without the involvement of any other intermediate reaction products. The amination and dechlorination reaction are believed to take place predominantly on the surface site of the Pd/Fe catalysts. The dechlorination rate of the reductive degradation of the two isomers of nitrochlorobenzene (o-, and p-NCB) in the presence of Pd/Fe as a catalyst was measured experimentally. In all cases, the reaction rate constants were found to increase with the decrease in the Gibbs free energy (correlation with the activation energy) of NCBs formation; the activation energy of each dechlorination reaction was measured to be 95.83 and 77.05 kJ/mol, respectively for o- and p-NCB. The results demonstrated that p-NCBs were reduced more easily than o-NCBs.

Removal of hexavalent chromium from aqueous solution by iron nanoparticles.

Groundwater remediation by nanoparticles has received increasing interest in recent years. This report presents a thorough evaluation of hexavalent chromium removal in aqueous solutions using iron (Fe(0)) nanoparticles. Cr(VI) is a major pollutant of groundwater. Zero-valent iron, an important natural reductant of Cr(VI), is an option in the remediation of contaminated sites, transforming Cr(VI) to essentially nontoxic Cr(III). At a dose of 0.4 g/L, 100% of Cr(VI) (20 mg/L) was degraded. The Cr(VI) removal efficiency decreased significantly with increasing initial pH. Different Fe(0) type was compared in the same conditions. The reactivity was in the order starch-stabilized Fe(0) nanoparticles>Fe(0) nanoparticles>Fe(0) powder>Fe(0) filings. Electrochemical analysis of the reaction process led to the conclusion that Cr(OH)(3) should be the final product of Cr(VI). Iron nanoparticles are good choice for the remediation of heavy metals in groundwater.