Study on Spatial Distribution and Seasonal Variations of Trace Metal Contamination in Sediments from the Three Adjacent Areas of the Yellow River Using HR-ICP-MS.

Spatial distribution, seasonal variations and pollution conditions of 6 heavy metals (Cr, Pb, Cd, Cu, Zn and Ni) in sediments in three different seasons (wet, dry and normal) from Gansu province, Ningxia and Inner Mongolia Autonomous Regions of the Yellow River were studied using high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS), geo-accumulation index (Igeo), respectively. The results indicated that content of heavy metals in all three seasons of Inner Mongolia sediment samples were higher compared to Ningxia and Gansu sections, and except Cd, the other metals concentrations in wet season are relatively higher, and they are lower and approximated in dry and normal seasons. Igeo showed that high Igeo values of Cd, Cu and Cr were found in Inner Mongolia region in wet and dry seasons, and the low Igeo values of the three metals were obtained in Gansu region. For season, the Igeo values of all study metals were higher in wet season than dry season, and they were decreased in normal season except Cd, while ICdgeo were high in all sampling sites in normal season indicating the strong anthropogenic sources there. Igeo values of metals including Pb, Zn and Ni were below 0 in wet season of Gansu, in dry season of Gansu, Ningxia regions and in normal season of all study regions, respectively, indicating a safer level. The results of spatial distribution and Igeo of study heavy metals suggested that higher total metal concentrations and potential risks were found in Inner Mongolia reaches of the Yellow River, and Cr, Cd and Cu were being more significant with the strong anthropogenic sources among all study metals. Considering the three different seasons, except normal season, the higher metal concentrations and potential risks for metals in sediments were observed in wet season than dry season, since the higher pH values of the sedimentary samples in wet season can help to promote adsorption and precipitation of heavy metal in sediments, meanwhile, the higher total organic carbon (TOC) values in sediments in wet season were also beneficial to the adsorption of heavy metals since the affinity between TOC and metal cations. Besides, the coast sediments with variety pollutants were brought into the river by rainfall in summer, which may also contribute to the rapid enrichment of heavy metals in sediments in wet season than dry season. The correlation among heavy metals and other variables and potential sources for heavy metals were evaluated by correlation coefficient analysis (CCA). The results of CCA revealed that Pb, Cu, Zn and Ni showed a significant correlation with each other, and they would be easily influenced by pH and TOC. Furthermore, Cr showed a correlation with Cd and TOC and reflected a strong anthropogenic source. The present work could provide new information on the metals behavior in surface sediments and reflect the sediment geochemistry in the regions in the three seasons, whilst the study of element interrelationships, including pH and TOC gave the available information on their possible origins.

Characterization of the Interaction between Acetylisovaleryltylosin Tartrat and Bovine Serum Albumin without or with Zn2+ and Cu2+ by Spectroscopic Analysis.

Acetylisovaleryltylosin tartrate (ATLL) is a new macrolide veterinary antibiotic, it is necessary to study the binding of ATLL to protein, which will directly correlate with the efficiency in vivo. Bovine serum albumin (BSA) is structure homologous with human serum albumin (HSA), and is commonly chosen as a model to investigate drug-protein interaction.There are many metal ions in plasma, as yet, the studies on mainly focus on single metal ion. In this study, the multiple systems formed by ATLL and BSA without or with Zn2+ and Cu2+ have been studied by mult-spectroscopy. The results showed that, the fluorescence of BSA was quenched by ATLL through a static quenching mechanism. The effective quenching constant (Ka) of ATLL to BSA decreased with Zn2+ and increased with Cu2+. Thermodynamic parameters revealed that hydrogen bonds and hydrophobic forces played significant roles in the binding of ATLL to BSA. The polarity of tryptophan and tyrosine residues changed when adding ATLL with or without Zn2+ and Cu2+. FT-IR spectra showed that ATLL changed α-helix and ß-sheet of BSA into ß-turn and random structure. The UV-Vis spectra indicated that the effects of Zn2+ on ATLL binding to BSA may cause by a competition binding, and Cu2+ possibly formed Cu2+-ATLL complex via metal ion bridge. All the knowledge obtained in this work will be helpful to understand the transport mechanism of ATLL with BSA and the effect of metal ions on the interaction of drug-protein in vivo.

Diversity, Abundance, and Distribution of nirS-Harboring Denitrifiers in Intertidal Sediments of the Yangtze Estuary.

Denitrification plays a critical role in nitrogen removal in estuarine and coastal ecosystems. In this study, the community composition, diversity, abundance, and distribution of cytochrome cd1-type nitrite reductase gene (nirS)-harboring denitrifiers in intertidal sediments of the Yangtze Estuary were analyzed using polymerase chain reaction (PCR)-based clone libraries and quantitative PCR techniques. Clone library analysis showed that the nirS-encoding bacterial biodiversity was significantly higher at the lower salinity sites than at the higher salinity sites. However, there was no significant seasonal difference in the nirS gene diversity between summer and winter. Phylogenetic analysis revealed that the nirS-harboring denitrifier communities at the study area had distinctive spatial heterogeneity along the estuary. At the lower salinity sites, the nirS-harboring bacterial community was co-dominated by clusters III and VII; while at the higher salinity sites, it was dominated by cluster I. Canonical correspondence analysis indicated that the community compositions of nirS-type denitrifiers were significantly correlated with salinity, ammonium, and nitrate. Quantitative PCR results showed that the nirS gene abundance was in the range of 1.01 × 10(6) to 9.00 × 10(7) copies per gram dry sediment, without significant seasonal variation. Among all the environmental factors, the nirS gene abundance was only significantly related to the change of salinity. These results can extend our current knowledge about the composition and dynamics of denitrification microbial community in the estuarine ecosystem.

[Research on the Content Characteristics and Pollution Evaluation of Heavy Metals in Filtered Water and Suspended Particles from Gansu, Ningxia and Inner Mongolia Sections of the Yellow River in Wet Season Using HR-ICP-MS].

The content characteristics, pollution evaluation and source identification of 6 heavy Metals (Cd, Pb, Cr, As, Cu and Zn) in filtered water and 9 heavy Metals (Cd, Pb, Cr, Ni, Cu, V, Co, Zn and Mn) in suspended particles from 10 sampling sites such as Zhaojunfuqiao (S1) and Baotoufuqiao (S2), etc. from Gansu, Ningxia and Inner Mongolia sections of the Yellow River in 2012 Wet Season were studied to understand the condition of the heavy metal pollution in Gansu, Ningxia and Inner Mongolia Sections of the Yellow River by using high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS). Multivariate geochemical approaches and statistical analysis were also exploited for assessing the level of heavy metals in filtered water and suspended particles from studied area. The results showed that in filtering water, only the concentrations of Cr exceeded the standard value of Environmental Quality Standard for Surface Water (GB3838-2002) and were the highest (74.8-94.7 µg x L(-1)) among all elements in 10 sampling sites; Single factor pollution index (I(i)) results suggested that the water quality in all sampling sites were contaminated by both Cr and total nitrogen (TN), with the exception of TN in Baotoufuqiao (S2); Integrated Nemerow pollution index (I) indicated that the I values in all sampling sites were between 1-2 (light pollution), which implied that the water quality in Gansu, Ningxia and Inner Mongolia sections, especially downstream sections (S1-S6) of the Yellow River wasn't an ideal source for drinking and using in aquaculture any more. In suspended particles, concentrations of heavy metals were relatively higher than their soil background values in 10 sampling sites, except Ni in S10 (34.7 µg x L(-1)). Index of geo-accumulation (I(geo)) indicated that the I(geo) values of Pb, Cr, Ni, Cu, V, Co, Zn and Mn in all sampling sites were less than 1 (unpolluted or unpolluted-moderately polluted), respectively, while I(geo)Cd were the highest in 10 sampling sites among all heavy metals and with the moderately to strong contamination in Zhaojunfuqiao (S1), Baotoufuqiao (S2), Wuhai (S5) and Dongdagouruhuanghekou (S8). The results of this paper would help to supply reliable experimental data for researching of distribution, migration and effective protection of heavy metals in study area.

Heavy Metals Contents and Speciation in Surface Sediments from Gansu, Ningxia and Inner Mongolia Sections of the Yellow River of China.

So far, many investigations had been made on the concentration and species distribution of heavy metals in aquatic environments. However, there are only a few studies on heavy metals in upper reaches of the Yellow River, especially in Gansu, Ningxia and Inner Mongolia sections. We have literatures related to the Yellow River, in this work, we remarkably discussed about the contents, speciation and potential risks of Cd, Pb, Cr, V, Co, Ni, Cu, and Zn in surface sediments from 12 sampling sites in Gansu, Ningxia, and Inner Mongolia sections of the Yellow River of China in 2011 year wet season by high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) and sequential extraction procedure of BCR method. The results indicated that the metals contents were arranged as Cr > V > Zn > Cu > Ni > Pb > Co > Cd in all sites. Comparing with the background value of soil in local section, Cd showed the highest level at S5 (1.30 µg x g(-1)), which was almost 13 times higher than the background value (0.103 µg x g(-1)). Pollution assessment indicated that Cd presented a strong polluted status with the geo-accumulation index (I(geo)) value of 3.08 at S5, moderately to strong polluted status with the I(geo) ranged from 2.02 to 2.90 in Inner Mongolia section (S1-S4). Moreover, enrichment factor (EF) showed that all heavy metals in these sediments have been influenced by anthropogenic activities. According to potential ecological risk index (RI), S5 and S3 demonstrated high ecologic risk of heavy metals, while other sampling sites showed moderately ecological risk. The results of BCR exhibited that Cd was the most available metal, followed by Co and Ni, while V and Cr were unavailable in the sediments. Risk assessment code (RAC) exhibited high risk for Cd at S1-S4 and very high risk at S5, while medium risk for Ni and Co at all sites. The results and conclusions may be important information and therefore of interest to the relevant departments of the governments.

[Mn2+-cTMAB-sensitized fluorescent microscopic determination of tosufloxacin tosylate based on a self-ordered ring].

With the development of antimicrobial drugs, drug residue in animal products has a serious potential hazards for the environment and public health, it is urgent to set up drug residue detection method with low detection limit and good selectivity. In our paper, with poly (vinyl alcohol)-124 (PVA-124) and NH3-NH4Cl (pH 10.50) as the medium, Mn2+ and cetyltrimethyl ammonium bromide (CTMAB) as sensitizer, tosufloxacin tosylate (TSFX) formed a self-ordered ring (SOR) on a hydrophobic glass slide support. When the droplet volume is 0.20 microL, the TSFX can be detected in the range of 4.05 x 10(-14) approximately 4.28 x 10(-13) mol x ring(-1) (2.02 x 10(-7) approximately 2.14 x 10(-6) mol x L(-1)), and the limit of detection (LOD) can reach 4.1 x 10(-15) mol x ring(-1) (2.0 x 10(-8) mol x L(-1)). The established method had been applied satisfactorily to determine the content of TSFX in tablet, which close to the marked value of 0.15 g x piece(-1)) found value: 0.144 g x piece(-1)) and the results of TSFX concentrations in rabbit serum at different time after dosing with the recoveries of 90.0% - 105.0% and RSDs 1.9% - 3.3% were satisfactory. Xilinguole of Inner Mongolia is the national important livestock products ground, whose lamb is the main suppling source for Beijing-Tianjin-Tangshan region. It is very urgent to detect residue of antibacterial drug in its sheep tissue samples (meat, liver, kidney). In this paper, when acetonitrile was used as extraction agent in pretreatment of sheep tissue samples in six rangelands including Sonid Right Banner, Xiwuzhumuqin Banner, Xilinhot City, Duolun County, The white Flag Town and The Blue Flag Town, the extract can be directly determined with SOR technology without filtering process, the sample standard addition recovery of sheep tissues were 92.0%-101.0% and RSDs were less than 2.7%. The results indicated that the SOR technique can be successfully applied to pharmaceuticals and biological samples, which broaden the applied range of SOR technique. The assay would provide reliable experimental data and theoretical basis for the relevant departments.

Analysis of the vibrational characteristics of diamane nanosheet based on the Kirchhoff plate model and atomistic simulations.

Single layer diamond-diamane, has been reported with excellent mechanical properties. In this work, molecular dynamics (MD) simulation and Kirchhoff plate model are utilized to investigate the vibrational characteristics of diamane sheets. The mechanical parameters of diamane sheets, including bending stiffness, Young's modulus, Poisson's ratio and coefficient of thermal expansion, are calibrated by using MD simulations. The natural frequencies and corresponding modal shapes of the diamane sheets predicted by the Kirchhoff plate model agree well with that obtained from the MD simulations. It is found that the edges exert marginal effect on the modal shapes when free boundary conditions are applied. Additionally, the Kirchhoff plate model considering the thermal expansion provides reasonable prediction for the natural frequencies of the diamane sheets with all boundary clamped under varying temperatures. This study offers valuable insights into the vibrational properties of diamane sheets, from both a simulation and theoretical standpoint. The findings would be beneficial for the design of nanoscale mechanical resonators utilizing these novel carbon materials.

Gross Nitrogen Mineralization in Surface Sediments of the Yangtze Estuary.

Nitrogen mineralization is a key biogeochemical process transforming organic nitrogen to inorganic nitrogen in estuarine and coastal sediments. Although sedimentary nitrogen mineralization is an important internal driver for aquatic eutrophication, few studies have investigated sedimentary nitrogen mineralization in these environments. Sediment-slurry incubation experiments combined with 15N isotope dilution technique were conducted to quantify the potential rates of nitrogen mineralization in surface sediments of the Yangtze Estuary. The gross nitrogen mineralization (GNM) rates ranged from 0.02 to 5.13 mg N kg(-1) d(-1) in surface sediments of the study area. The GNM rates were generally higher in summer than in winter, and the relative high rates were detected mainly at sites near the north branch and frontal edge of this estuary. The spatial and temporal distributions of GNM rates were observed to depend largely on temperature, salinity, sedimentary organic carbon and nitrogen contents, and extracellular enzyme (urease and L-glutaminase) activities. The total mineralized nitrogen in the sediments of the Yangtze Estuary was estimated to be about 6.17 × 10(5) t N yr(-1), and approximately 37% of it was retained in the estuary. Assuming the retained mineralized nitrogen is totally released from the sediments into the water column, which contributed 12-15% of total dissolved inorganic nitrogen (DIN) sources in this study area. This result indicated that the mineralization process is a significant internal nitrogen source for the overlying water of the Yangtze Estuary, and thus may contribute to the estuarine and coastal eutrophication.

Anaerobic ammonium oxidation and its contribution to nitrogen removal in China's coastal wetlands.

Over the past several decades, human activities have caused substantial enrichment of reactive nitrogen in China's coastal wetlands. Although anaerobic ammonium oxidation (anammox), the process of oxidizing ammonium into dinitrogen gas through the reduction of nitrite, is identified as an important process for removing reactive nitrogen, little is known about the dynamics of anammox and its contribution to nitrogen removal in nitrogen-enriched environments. Here, we examine potential rates of anammox and associate them with bacterial diversity and abundance across the coastal wetlands of China using molecular and isotope tracing techniques. High anammox bacterial diversity was detected in China's coastal wetlands and included Candidatus Scalindua, Kuenenia, Brocadia, and Jettenia. Potential anammox rates were more closely associated with the abundance of anammox bacteria than to their diversity. Among all measured environmental variables, temperature was a key environmental factor, causing a latitudinal distribution of the anammox bacterial community composition, biodiversity and activity along the coastal wetlands of China. Based on nitrogen isotope tracing experiments, anammox was estimated to account for approximately 3.8-10.7% of the total reactive nitrogen removal in the study area. Combined with denitrification, anammox can remove 20.7% of the total external terrigenous inorganic nitrogen annually transported into China's coastal wetland ecosystems.

Characterization of the interaction between nitrofurazone and human serum albumin by spectroscopic and molecular modeling methods.

The interaction of nitrofurazone (NF) and human serum albumin (HSA) has been studied by fluorescence spectroscopy, FT-IR spectroscopy and molecular modeling methods. The results showed that the fluorescence of HSA was quenched by NF in a static quenching mechanism. Thermodynamic parameters revealed that hydrogen bonds and van der Waals force played the major role during the interaction. The calculated binding distance (r) indicated that the non-radioactive energy transfer came into being in the interaction between NF and HSA. HSA had a single class of binding site at Sudlow' site I in subdomain IIA for NF, which was verified by the displacement experiment. The molecular modeling study further confirmed the specific binding sites of NF on HSA, such as the interaction between N11 and N14 of NF with Lue 283 and Ser 287 predominately through hydrogen bonds. Three-dimensional fluorescence spectra indicated that the polarity around the tryptophan residues decreased and the conformation of HSA changed after adding NF. FT-IR spectra showed that NF could induce the polypeptides of HSA unfolding because it changed α-helix and ß-sheet into ß-turn and random structure of HSA.