[Mixing behavior of arsenic in the Daliaohe Estuary].

Mixing behavior of arsenic in the Daliaohe Estuary was studied. Twenty samples were collected from the Daliaohe Estuary during April, July and November, 2010 and arsenic was determined by HG-AFS. The concentrations of arsenic varied from 2.98-44.1, 1.19-14.6, 1.27-12.4 microg x L(-1) in April, July and November. The seasonal variation of arsenic content was significant. In July, the concentration of arsenic was lower than that in April, and higher than that in November. The data indicated that arsenic did not behave conservatively in April and November, but behaved conservatively in July. An important mobilization of dissolved arsenic was observed from the river up to halfway in the estuary in April and November, 2010. Both input flux (from river to estuary) and output flux (from estuary to coastal zone) of dissolved arsenic were calculated from statistical interpretations of the salinity profiles. Concentration of arsenic in the Daliaohe Estuary is higher than large systems, like the Changjiang Estuary and Zhujiang Estuary.

[Distributions of arsenic and selenium in the Yangtze estuary and its adjacent areas].

One cruise of "Haijian 47" was carried out in September 2004, to understand the behaviors of selenium and arsenic in the Yangtze Estuary and its adjacent areas. Selenium and arsenic species are determined by HG-AAS. Concentrations rang from 13.5 nmol x L(-1) to 25.2 nmol x L(-1) for arsenic, under detection to 5.22 nmol x L(-1) for As(III), 1.50 nmol x L(-1) to 5.70 nmol x L(-1) for selenium, with average of 17.9 nmol x L(-1), 1.76 nmol x L(-1) and 3.35 nmo x L(-1), respectively. Concentrations of arsenic and selenium decrease gradually from Yangtze Estuary to the East China Sea. The high concentration of arsenic appears mainly in the Yangtze diluted water area and the coastal water area of Jiangsu and Zhejiang, and the low values is present at the southeast part of study area showing the influence of the Kuroshio water. The data indicates that selenium did not behave conservatively in the estuary, but arsenic behaves conservatively. An important mobilization of selenium is observed from the river up to halfway in the estuary. Concentrations in the sediment range from 3.87 mg kg(-1) to 13.1 mg x kg(-1) for arsenic, 0.067 mg x kg(-1) to 0.23 mg x kg(-1) for selenium. Yangtze input is the main source of arsenic and selenium in the sediment.

[Effect of the first water-sediment regulation on the variations of dissolved inorganic nutrients' concentrations and fluxes in the lower main channel of the Yellow River].

The variations and fluxes of dissolved inorganic nutrients were studied, based on continuously monitored data in the lower main channel of Yellow River (Lijin) during the period of water-sediment regulation in July 2002. Concentrations rang from 169.3 to 273.2 micromol x dm(-3) for NO3- -N, 0.08 to 0.84 micromol x dm(-3) for NO2- -N, 1.39 to 5.04 micromol x dm(-3) for NH4+ -N, with average of 218.6, 0.16, 2.27 micromol x dm(-3), respectively. Concentrations rang from 0.36 to 0.56 micromol x dm(-3) for PO4(3-) -P, 161.4 to 195.8 micromol x dm(-3) for SiO3(2-) -Si, with average of 0.48, 166.7 micromol x dm(-3), respectively. No significant relationship was found between nitrate, phosphate and water discharge during the period of water-sediment regulation, while silicate correlated well with suspended sediment discharge. Water-sediment regulation has no significant effect on the variation of dissolved inorganic nutrients concentrations during 2002 to 2003. But the fluxes proportion of dissolved inorganic nutrients during water-sediment regulation to the whole year is about 50%.

Hydrochemical processes controlling arsenic and selenium in the Changjiang River (Yangtze River) system.

The hydrochemistry of arsenic and selenium in the Changjiang (Yangtze River) was studied, based on continuously monitored data at Nantong station (i.e. 180 km inland from river mouth), the main Changjiang channel and 10 major tributaries. The dissolved inorganic arsenic (DIAs) and selenium (DISe) concentrations of the Changjiang are related to water discharge, rock type of drain basin, anthropogenic influences etc. The DIAs and DISe levels vary over an order of magnitude throughout the basin (i.e. 6.95-68.9 nmol/L for DIAs, 1.16-9.92 nmol/L for DISe). Source rock composition is the primary control on the concentrations of DIAs and DISe in the Changjiang. Several tributaries (e.g. Xiangjiang River, Minjiang River and Tuojiang River) are contaminated by human activities. Flux calculations from hydrographic data at Datong (the most downstream main channel station without tidal influence) indicate that the Changjiang transports 234.8 x 10(5) mol/yr of DIAs and 49.6 x 10(5) mol/yr of DISe to the East China Sea.