Supramolecular Copolymerization Strategy for Realizing the Broadband White Light Luminescence Based on N-Deficient Porous Graphitic Carbon Nitride (g-C3N4).

The N-deficient porous g-C3N4 with broadband white light emission was constructed by supramolecular copolymerization design, which combined organic copolymers cyanuric acid and 2,4,6-triaminopyrimidine with melamine upon the mixture gas environment of (95%)N2/(5%)H2. Herein, we achieved great breakthrough in narrowing the band gap of g-C3N4 from 2.64 to 1.39 eV. Furthermore, in contrast to pristine g-C3N4, we demonstrated that the emission wavelengths of N-deficient porous g-C3N4 can be tuned from narrow blue to broadband white range, where the optimal white light coordinate position is (0.297, 0.345). The prepared N-deficient porous g-C3N4 overcomes the limitation of the narrow adjusting range of optical properties while using conventional g-C3N4 and makes it more promising for applications in solid-state displays.

[Variation characteristics and potential ecological risk assessment of heavy metals in the surface sediments of Bohai Bay].

The geochemical characteristics of eight heavy metals (Cd, Co, Cr, Cu, Ni, Pb, V and Zn) in two sediment cores from Bohai Bay, North China, were studied. Sediment samples were collected from 27 stations in spring 2008. A sequential extractions, procedure was used to gain their fractionation information. Five operationally defined fractions were obtained by this protocol, i. e. exchangeable (L1), bound to carbonates (L2), bound to Fe/Mn-oxides (L3), bound to organic matter and sulphides (LA), and residual fraction (R5). Combined with ecological risk in total contents and fraction, a series of results and viewpoints with regard to distribution characteristics of heavy metals were presented, as well as ecological risk and controlling factors. Heavy metals in sediments were mainly concentrated in the middle region with fine particle. The distributions of V, Ni, Cu, Pb, Co, Cd were mainly controlled by nature source, while Zn and Cr can be easily impacted by environment or human input. Coming from atmospheric deposition and riverine, Pb was different with other heavy metals. Sequential extractions suggested that V, Zn, Cr were mainly composed with residual fractions, while Co, Ni, Cu were dominated by labile fractions. The percentage of labile Co increased from inner to outside, labile Ni reached maximum at station A3, labile Cu and Pb concentrated in the middle of Bohai Bay, while Cu achieved maximum at station D1 near Yellow River. Labile heavy metals were enriched near the estuary of Haihe River. The order of enrichment factors (EF) of heavy metals was Pb > Cd > Zn > Cr > V > Co > Cu > Ni. And the EF of Pb, Cd and Zn were above 1, suggesting that they could be polluted by exterior input, while the sediment quality was relatively good in general. The ratios of labile and residual fraction showed that V and Cr were clean, Zn was partly in slightly polluted, Co was mostly slightly polluted, Cu was from clean to moderately polluted, Ni was polluted from slightly to heavy, and Pb was polluted heaviest in all heavy metal. In conclusion, V, Cr and Co were clean, Cu and Zn may be polluted, while Pb was polluted heaviest.

Fraction characteristics of rare earth elements in the surface sediment of Bohai Bay, North China.

Surface sediment samples were collected at 27 stations of Bohai Bay, North China. Sequential extractions were carried out in this study. REE were leached out from four labile fractions: Exchangeable (L1), bound to carbonates (L2), bound to Fe-Mn oxides (L3), bound to organic matter (L4), and the remainder was residual (R5). The total contents of REE fluctuate slightly in Bohai Bay, and are mainly concentrated in the middle region, showing relatively higher levels in the north than that in the south of Bohai Bay. Percentages of L1, L2, L3, L4, and R5 for REE suggest that the residual fraction accounts for the major component of REE, whereas Fe-Mn oxides also play important roles in combining labile REE. As the REE complex is not stabilized, the competition of complex could induce dissociation of the complex and redistribution of the REE in various environments. According to REE patterns and Y/Ho ratios of samples, REE are not anthropogenic or oceanic sources but riverine input, whereas suitable environment varieties can slightly affect the patterns and fractionations of REE. As powerful tracers for the variable of environment, higher anomaly of Eu and Ce in southern regions indicates a greater reduction in the condition of surface sediment in the south than that in the north of Bohai Bay.

Thallium concentrations and sources in the surface sediments of Bohai Bay.

The Tl concentrations and chemical speciation were determined in the surface sediments of Bohai Bay to evaluate its biogeochemical characteristics. The total Tl concentrations were in the range of 0.506-0.770 µg/g and correlated significantly with clay and total organic carbon (TOC) contents, suggesting that the grain size and TOC were major factors controlling Tl distribution. The sequential extraction performed to indicate Tl speciation and availability in Bohai Bay sediments suggested that Tl occurred mainly in the residual fraction and Tl came mainly from natural input. In the non-residual fractions, Fe-Mn oxide and organic matter fractions accounted for the main portions, suggesting that the labile Tl adsorption was dominated by Fe-Mn oxides and organic matter. In addition, according to our estimate, about 2.7 t/yr and 0.16 t/yr of Tl reached Bohai Bay via rivers and atmosphere, respectively.

The distribution, enrichment and source of potential harmful elements in surface sediments of Bohai Bay, North China.

A geochemical study of Bohai Bay surface sediments was carried out to analyze the potential harmful element (PHE: Ge, Mo, In, Sn, Sb, Te, Tl, Bi and V) concentrations, transportation and deposition, enrichment factors and sources. Germanium, Mo, In, Sn, Sb, Te, Tl, Bi and V concentrations in the surface sediments were: 1.43-1.71, 0.52-1.43, 0.04-0.12, 2.77-4.14, 1.14-2.29, 0.027-0.085, 0.506-0.770, 0.27-0.63 and 70.35-115.90 µg/g, respectively. The distributions of total PHE concentrations, together with sequential extraction analyses, showed that the PHEs were mainly due to natural inputs from the continental weathering delivered to the bay by rivers and atmospheric transportation and deposition. However, high Mo, Sb, Te, Bi and V occurred in non-residual fractions, suggesting some anthropogenic inputs in addition to the natural inputs. Besides sources, the distributions of PHEs were influenced by the coupling of physical, chemical and biological processes. Enrichment factor (EF) was computed for each site for each element in order to assess the polluting elements and the degree of pollution at each site. Results revealed that the EFs were generally lower than 1.0, particularly for Ge, Mo, In, Sn, Tl and V; however, the EFs were higher (>1.5), particularly for Sb, Te and Bi, revealing moderate contamination.

Environmental geochemistry reflected by rare earth elements in Bohai Bay (North China) core sediments.

In Bohai Bay sediment, two cores were collected to estimate the source of sediments, and assess the environmental changes. Sequential extractions were carried out in this study. Rare earth elements (REE) were leached out from four labile fractions: Exchangeable (L1), Bound to carbonates (L2), Bound to Fe-Mn oxides (L3), Bound to organic matter (L4), and the remainder was Residual (R5). The percentages of REE in different fractions follow the order: R5 > L3 > L2 > L4 > L1. With heavy REE depletion and no pronounced REE fractionation, NASC-normalized REE patterns of Bohai Bay sediments are quite consistent with that of Haihe River sediment, which is the key river of Bohai Bay. Y/Ho ratios of total contents are all much lower than the average value of continental crust, while Y/Ho ratios of L2 are higher than those of other fractions. Based on the patterns of REE and Y/Ho ratios of samples, sediments of Bohai Bay mainly come from terrigenous matters, which are mainly brought by Haihe River. And REE combined with carbonates may be partly inherited from anthropogenic matter. Moreover, environmental changes exert significant influences on the patterns and fractionations of REE, and they can be deduced from the characteristics of REE. Our results on the patterns and burial fluxes of REE reflect two environmental changes: Bohai Bay has been shifting towards more reducing conditions in the last one hundred years, and there was a large flood in 1939.

Concentrations of cadmium and zinc in seawater of Bohai Bay and their effects on biomarker responses in the bivalve Chlamys farreri.

Both in-field chemical investigation and in the laboratory toxic tests were carried out to systematically understand the pollution status of cadmium (Cd) and zinc (Zn) in Bohai Bay. Samples collected from surface seawater were determined to describe the distributions of Cd and Zn in Bohai Bay. The average values in our study of Cd and Zn were 0.15 microg/L and 19.68 microg/L, respectively. Both of them were lower than the first class limit of seawater quality standard in China. In the laboratory, antioxidant enzymes [SOD (Cu/Zn-SOD, Mn-SOD), CAT], lipid peroxidation (MDA), phase I and phase II enzymes (CYP4501A and GST) were investigated in the bivalves Chlamys farreri exposed to Cd and Zn at the concentration levels of Bohai Bay seawater, which were obtained from our in-field investigation. The reduced SOD, CAT, and EROD (7-ethoxyresorufin-O-deethylase) activities (with the inhibitory rate of 16.8%, 31.5%, and 51.6%, respectively) in Cd treatment were observed and resulted in obvious lipid peroxidation damage. However, treatment of Zn showed elevations in SOD and GST by 13.3% and 29.9%, respectively, and with no influence on lipid peroxidation. In summary, seawater quality in Bohai Bay seawater was ranked as good in general, but it seemed that Cd might possess a potential environmental risk by effecting pro-oxidant/antioxidant balance and phase I detoxification in C. farreri.

Biomarker responses in the bivalve (Chlamys farreri) to exposure of the environmentally relevant concentrations of lead, mercury, copper.

Water samples collected from Bohai Bay were determined to describe the distributions of lead, mercury, and copper in this area, indicating that mean values of the three metals were 1.63µg/L, 4.85×10(-2)µg/L, and 2.68µg/L, respectively. Only lead exceeded the first class limit of seawater quality standard in China. Then, antioxidant enzymes, lipid peroxidation, and metabolic enzymes were investigated in bivalves (Chlamys farreri), exposed to three metals at the environmental concentration levels obtained from our investigation. Significantly reduced SOD, CAT and GPx activities, in lead-exposed group were observed and resulted in obvious lipid peroxidation. In contrast, mercury and copper did not show such clear oxidative stresses. In consistent with the oxidative stress variations, exposed only to lead caused a great inhibition on EROD activity. Multi-biomarker responses in bivalve when exposed to lead at the environmentally relevant concentration in Bohai Bay suggested that lead may possess a potential risk in this area.

Variation characteristics and ecological risk of heavy metals in the south Yellow Sea surface sediments.

Eight cruises were conducted on the south Yellow Sea (SYS) from 1998 to 2005. Variations and the potential ecological risk of heavy metals were studied using the survey data collected during October 2003. The metal content (except for As) was high in the central area where the fine grain size sediments were dominant, and low inshore area where more coarse sediments were present. This suggested that grain size was important in determining distributions of heavy metals. In some local areas, other influencing factors, such as organic content, sedimentation rate, burial efficiency and metal's existing form were discussed. The annual averages of metals showed a stable trend with appreciable fluctuations in 8 years. Using potential ecological risk index (E (RI)) to evaluate the integrated pollution effect of heavy metals, 38.7% of the investigated area was in a moderate degree of contamination, while 77.8% was under moderate ecological risk. However, no distinct correlation was found between E (RI) and plankton biomass. In conclusion, the sediment quality of SYS was good, and the ecological risk was low in general.

[Effects of excessive inorganic nitrogen on inorganic carbon system in seawater simulated experiments].

The influence of excessive inorganic nitrogen (NO3-, NH4+, NO2-) on the pH, inorganic carbon system and air-sea CO2 flux was studied in laboratory seawater simulation experiments. The result indicates that the excessive inorganic nitrogen significantly has an important influence on the inorganic carbon system in all conditions. At the NO3- addition groups, HCO3- and p (CO2) increase while pH and CO3(2-) decrease when the concentration of NO3- < or = 37.60 micromol x L(-1). But high concentrations > or = 188 micromol x L(-1) is just the reverse. The seawater changes from carbon source to carbon sink of atmospheric CO2 with NO3- addition increased. At the NH4+ addition groups, HCO3- and p (CO2) decrease while pH and CO3(2-) increase when the concentration of NH4+ < or = 25.20 micromol x L(-1). However, when the concentration of NH4+ > or = 126 micromol x L(-1), the concentrations of HCO3- and p (CO2) increase with NH4+ addition and the seawater changes from carbon sink to carbon source of atmospheric CO2 and the intensity of carbon source has a positive relationship with the concentration of NH4+. At the NO2- addition groups, the concentrations of HCO3- and p (CO2) decrease while pH and CO3(2-) increase with time scale and the seawater acts as a strong carbon sink with NO2- addition of 7.90 micromol x L(-1). While at the other NO2- concentration levels, the carbon sink is weak in seawater. The Chl-a concentration of nutrient addition groups compared with control (delta Chl-a) shows a significant negative correlation with delta p (CO2) (r = -0.87, p < 0.000 1, n = 16). The main controlling factor to the variation of inorganic carbon system is the adaptation of phytoplankton to different form and concentration of nitrogen.

[Variation characteristics and controlling factors of heavy metals in the South Yellow Sea surface seawaters].

Based on the 8 cruises data of surface seawater heavy metals and other related environmental factors from 1997 to 2004 of the South Yellow Sea (SYS), distribution patterns, mechanisms controlling the distributions and pollution levels of heavy metals (As, Cd, Cu, Hg, Pb, Zn) were studied with the data of 2003-10, and 8-year-fluctuation trends of heavy metals were also discussed. The average concentrations of heavy metals in surface seawater were 2.33, 0.078, 1.41, 0.003 6, 0.37, 6.21 microg/L respectively. The average concentrations showed a relatively stable trend in 8 years, except Zn's distinct upward tendency. The distribution patterns corresponded to the distance away from the coastline,that was, the content of heavy metals (except Pb) was low in central area while high inshore. Those were responses of human activity in the marginal sea, however, in some local areas, Pb was controlled by atmospheric deposition, Cd was relative to pH and salinity, Hg was related to organic carbon, Cu and Zn were influenced by runoff and drainage, and the resuspending of sediments played important roles on the content and distribution of As. Compared to the Marine Water Quality Standard of China, heavy metals indicated that SYS was a first class sea, and Ecological Risk Index analysis showed that SYS was a low ecological risk sea. In conclusion, seawater quality of heavy metals in SYS surface seawater is relatively good in general.