Trace element content in alluvial soils landscape of the flood plains of the Iput river

The results of research on the content and distribution of trace elements in alluvial soils of various elements of the floodplain landscape, and their relationship with fertility indicators are presented. It has been found that the maximum concentrations of most trace elements (Ni, Zn, Mn, Cr, Co, Mo, As) are characteristic of the alluvial overhanging-marsh heavy-coal pristine subsystem of the floodplain landscape. In the riverine and perish subsystems of the floodplain landscape in individual layers of the corresponding soils, an excess of clark was found: in the alluvial sour acid layered primitive shortened sandy loam Cu by 1.5; Zn in 1.1; Cd 9.2 times, in alluvial chilli-marsh heavy-coal Cu 1.05; Zn in 1.4; Mn in 1.01; Cr in 1,2; Cd 3.2 times. For the riverine and perch subsystems, the excess of Cu, Mn and Cr was observed in the soil layer 0-5 cm, the remaining exceedances are characteristic of deeper layers. Decreasing rows of trace elements in alluvial soils have a similar structure. The microelements in question, in the soils of the floodplain landscape of the Iput River, in terms of clark concentration, belong to the group of dispersing. There is no significant correlation between micronutrient content and fertility of the alluvial soils under consideration.

Sediment-Peridotite Reaction Controls Fore-Arc Metasomatism and Arc Magma Geochemical Signatures

Subduction of oceanic crust buries an average thickness of 300–500 m of sediment that eventually dehydrates or partially melts. Progressive release of fluid/melt metasomatizes the fore-arc mantle, forming serpentinite at low temperatures and phlogopite-bearing pyroxenite where slab surface reaches 700–900 °C. This is sufficiently high to partially melt subducted sediments before they approach the depths where arc magmas are formed. Here, we present experiments on reactions between melts of subducted sediments and peridotite at 2–6 GPa/750–1100 °C, which correspond to the surface of a subducting slab. The reaction of volatile-bearing partial melts derived from sediments with depleted peridotite leads to separation of elements and a layered arrangement of metasomatic phases, with layers consisting of orthopyroxene, mica-pyroxenite, and clinopyroxenite. The selective incorporation of elements in these metasomatic layers closely resembles chemical patterns found in K-rich magmas. Trace elements were imaged using LA-ICP-TOFMS, which is applied here to investigate the distribution of trace elements within the metasomatic layers. Experiments of different duration enabled estimates of the growth of the metasomatic front, which ranges from 1–5 m/ky. These experiments explain the low contents of high-field strength elements in arc magmas as being due to their loss during melting of sedimentary materials in the fore-arc.

Spatial distribution of trace elements in surface sediments of Hooghly (Ganges) river estuary in West Bengal, India

The spatial distribution of trace elements in surface sediments of the Hooghly estuary was studied over the monsoons in 2014–2017. As, Cd, Ni, Pb and U were two- to sixteen-fold the crust means with increasing levels toward the estuary, with Ni peak during the post-monsoon. Pearson’s correlation matrix, cluster analysis, enrichment factors and pollution index revealed the anthropic source and association of trace elements with Fe, Mn and Al and of Pb with U. Geoaccumulation index revealed for Ni an extremely contaminated situation at the estuary water during monsoon and for Cd a heavily contaminated situation at freshwater location. The potential contamination index was >6; thus, sediments were very severely contaminated by As, Cd and Ni with worst situation for As and Cd at fresh and brackish water and during post-monsoon. The overall ecological risk was severe, 300≤RI<600 at all sites and seasons, especially after the monsoon, at fluvial and brackish locations.