International audience | From 1899 to 2002, sandy Luvisol in the Paris region has been intensively irrigated with raw wastewater, resulting in major soil pollution by metallic trace elements (MTE). To identify the soil phases implicated in retaining these metals, sequential extractions were performed on a solum irrigated with untreated wastewater and another reference solum. The endogenous and exogenous fractions of MTE in the contaminated soil were discriminated using correlations between MTE and major elements defined from unpolluted soils of the area. In the contaminated soil no exogenous lead and chromium are present below the surface horizon, whereas exogenous zinc and copper are found down to the base of the solum. The endogenous MTE are mainly found in the residual fraction. Exogenous MTE appear to be associated with organic matter in the surface horizon, and exogenous zinc seems to be readsorbed on iron and manganese oxyhydroxides in the underlying horizons. After 100 years of intensive irrigation with wastewater, no exogenous Pb and Cr are found in the subsoil, while exogenous Zn and Cu are found down to the base of the solum, mostly readsorbed.

The distributions and biogeochemical cycles of arsenic in the aquatic environment have captured the interest of geochemists due to arsenic's multiple chemical forms, the toxicity of certain arsenic species and large anthropogenic input. Seasonal variations in the dissolved inorganic arsenic concentration and speciation in Jiaozhou Bay, which is located on the west coast of the Yellow Sea in northern China, are presented here. Three cruises were carried out in Jiaozhou Bay under varying tidal regimes, one at neap tide and one at spring tide in August and one at spring tide in October of 2001. In addition to the transect surveys, the main sources of dissolved inorganic arsenate and arsenite in Jiaozhou Bay, including riverine input from five major tributary rivers, atmospheric dry and wet depositions, and groundwater and wastewater input, were collected in different seasons to estimate arsenic transport through different sources. The mean concentrations of total dissolved inorganic arsenic (TDIAs, As (V+III)) in Jiaozhou Bay were statistically comparable between summer and autumn, with higher concentrations at the northwest and northeast parts of the bay, reflecting human activities. The As (III)/TDIAs ratio ranged between 0.045 and 0.68, with an average of 0.16, implying that arsenate was the dominating species in Jiaozhou Bay. A preliminary box model was established to estimate the water-mass balance and arsenic budgets for Jiaozhou Bay, which demonstrated that river inputs and atmospheric depositions were the main sources of arsenic into Jiaozhou Bay. The concentrations of dissolved inorganic arsenic in Jiaozhou Bay have decreased in the last two decades. Compared with other areas in the world, the concentration of arsenic in Jiaozhou Bay remains at the natural level and this region can be characterized as a less disturbed area.