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BACKGROUND The contamination of arsenic and mercury in intertidal sediments will lead to excessive levels of arsenic and mercury in the flora and fauna of the region, which will seriously affect the ecological environment of local vegetation and further affect the survival and safety of human beings. Therefore, it is of great practical significance to study the changes in the contents and spatial distribution of arsenic and mercury in intertidal sediments. OBJECTIVES To investigate the contents of arsenic and mercury in sediments, so as to provide basic information on the pollution of arsenic and mercury in intertidal sediments. METHODS The contents of arsenic and mercury in the sediments of the study area were determined by atomic fluorescence spectrometry (AFS), and iron was selected as the normalized element to establish the environmental background values of arsenic and mercury elements in different intertidal sediments. The geoaccumulation index method and potential ecological hazard index method were used to evaluate the pollution status of arsenic and mercury in the study area. RESULTS Background value of arsenic content: Minjiang Estuary (2.90mg/kg) < Daliao Estuary (6.42mg/kg) < Yancheng Shoal in northern Jiangsu (11.02mg/kg) < Pearl River Estuary (19.19mg/kg). Background value of mercury content: maximum in Pearl River Estuary (0.08mg/kg), less in Daliao Estuary, Yancheng shoal and Minjiang Estuary (0.02mg/kg, 0.02mg/kg, 0.03mg/kg, respectively). The maximum values of background values of arsenic and mercury were both found in the Pearl River Estuary, and the minimum values were located in the Minjiang Estuary. The maximum values of arsenic and mercury of sediments were both found in the Pearl River Estuary, which were 42.90mg/kg and 0.287mg/kg, respectively, and were greater than the first class of Marine Sediment Quality Standard (arsenic: 20.0mg/kg; mercury: 0.2mg/kg). Arsenic belonged to no pollution and slight potential ecological hazards in the four intertidal sediments. Mercury was a medium potential ecological hazard in the Pearl River Estuary, and slight pollution or no pollution in the other three intertidal sediments. CONCLUSIONS The distribution of arsenic and mercury in the sediments of the four intertidal zones in the study area is characterized by "high in the south and low in the north". The arsenic and mercury contents in the intertidal sediments of Minjiang and Pearl River estuaries are more influenced by industrial and agricultural activities, thus causing the distribution features. The pollution of arsenic and mercury in the Pearl River Estuary is more serious than other intertidal areas, so it is urgent to strengthen the control of their pollution trends.

Since the Quaternary Period, palaeo-seawater intrusions have been suggested to explain the observed saline groundwater that extends far inland in coastal zones. The Luanhe River Delta (northwest coast of Bohai Sea, China) is characterized by the distribution of saline, brine, brackish and fresh groundwater, from coastline to inland, with a wide range of total dissolved solids (TDS) between 0.38-125.9 g L−1. Meanwhile, previous studies have revealed that this area was significantly affected by Holocene marine transgression. In this study, we used hydrochemical, isotopic, and sedimentological methods to investigate groundwater salinization processes in the Luanhe River Delta and its links to the palaeo-environmental settings. The isotopic results (2H, 18O, 14C) show that deep confined groundwater was recharged during the Late Pleistocene cold period, shallow saline and brine groundwater was recharged during the warm Holocene period, and shallow brackish and fresh groundwater was mainly recharged by surface water. The results of hydro-geochemical modeling (PHREEQC) suggest that the salty sources of salinization are seawater and concentrated saline water (formed after evaporation of seawater). The 18O-Cl relationship diagram shows that saline and brine groundwater are formed by three end-member mixings (seawater, concentrated saline water and, fresh groundwater). In contrast, brackish groundwater is formed after the wash-out of saline groundwater by surface water. Using palaeo-environmental data from sediments, we found that palaeo-seawater intrusion during the Holocene marine transgression was the primary cause of groundwater salinization in the study region. Seawater was found to evaporate in the lagoon area during the progradation of the Luanhe River Delta; the resulting concentrated saline water infiltrated into the aquifer, eventually forming brine groundwater due to salinity accumulation. Surface water recharge and irrigation, on the other side, would gradually flush the delta plain's saline groundwater. This study provides a better understanding of saline groundwater evolution in other similar coastal zones. [ABSTRACT FROM AUTHOR]

Abstract: Six new binuclear organoaluminum complexes (1)2Al2Me2 (7), {(2)AlMe}2 (8), {(3)AlMe}2 (9), {(4)AlMe}2 (10), {(5)AlMe}2 (11) and {(6)AlMe}2 (12) have been prepared in good yields by alkane elimination from AlMe3 and chiral biaryl-based N2O ligands, (S)-2-(pyrrol-2-methyleneamino)-2′-hydroxy-1,1′-binaphthyl (1H2), (S)-5,5′,6,6′,7,7′,8,8′-octahydro-2-(pyrrol-2-methyleneamino)-2′-hydroxy-1,1′-binaphthyl (2H2), (S)-2-(pyrrol-2-methyleneamino)-2′-hydroxy-6,6′-dimethyl-1,1′-biphenyl (3H2), (S)-2-(pyridine-2-ylmethylamino)-2′-hydroxy-1,1′-binaphthyl (4H2), (S)-5,5′,6,6′,7,7′,8,8′-octahydro-2-(pyridine-2-ylmethylamino)-2′-hydroxy-1,1′-binaphthyl (5H2), and (S)-2-(pyridine-2-ylmethylamino)-2′-hydroxy-6,6′-dimethyl-1,1′-biphenyl (6H2), which are derived from (S)-2-amino-2′-hydroxy-1,1′-binaphthyl or (S)-2-amino-2′-hydroxy-6,6′-dimethyl-1,1′-biphenyl, respectively. Complexes 7–12 have been characterized by various spectroscopic techniques, elemental analyses, and X-ray diffraction analyses. Complex 7 derived from 1H2, has a C 2v quasi-symmetric N4AlO2AlMe2 core structure, while complexes 8 and 10 derived from 2H2 or 4H2, adopt a C 2 quasi-symmetric MeN2AlO2AlN2Me core structure, indicating that the steric effect of the ligand plays an important role in the complex formation. Complexes 7–12 are active catalysts for the polymerization of rac-lactide in the presence of isopropanol, leading to the heterotactic-rich polylactides. [Copyright &y& Elsevier]

A Rh-catalyzed highly chemo- and enantioselective hydrogenation of 2-CF 3 -chromen/thiochromen-4-ones was successfully established achieving excellent selectivity and high turnover numbers. Under mild conditions, a series of 2-CF 3 -chromen-4-ones were hydrogenated to provide the corresponding chiral 2-CF 3 -chroman-4-ones with excellent enantioselectivities (up to 99.9% ee) and achieve high turnover numbers (TON of up to 11,800). Moreover, the obtained hydrogenation products were also successfully transformed into other derivatives including the important intermediate of plasmepsin inhibitors with maintained enantiopurity.

A highly regioselective asymmetric hydroboration of 2 H-chromenes catalyzed by the complex of CuCl and diphosphine ligand ( S, R)-DuanPhos has been realized under mild conditions to produce 3-boryl chromans, achieving good yields and excellent enantioselectivities up to 96% ee. This work provides an efficient approach to the synthesis of chiral 3-boryl chromans and derivatives.

A highly efficient enantioselective hydrogenation of 1,2-dicyanoalkenes catalyzed by the complex of rhodium and f-spiroPhos has been developed. A series of 1,2-dicyanoalkenes were successfully hydrogenated to the corresponding chiral 1,2-dicyanoalkanes under mild conditions with excellent enantioselectivities (up to 98% ee). This methodology provides efficient access to the asymmetric synthesis of chiral diamines.

The TunePhos/diamine-Ru(II) complex combined with t-BuOK in 2-propanol effectively catalyzes enantioselective hydrogenation of a wide range of simple ketones including aromatic, heteroaromatic, alpha,beta-unsaturated, and cyclopropyl ketones, affording high reactivity (up to 1,000,000 TON) and excellent enantioselectivities (>99% ee for 13 examples).