Themed collection Geochemistry

Prior to the 1960s, knowledge of biological transformations of highly halogenated aliphatic compounds was limited, except in mammalian organisms where enzymatic transformations occurred to rid the body of ingested harmful chemicals.

The distribution of trace elements (TEs) in the bituminous sands is dichotomous: V, Ni, Mo, Se and Re are found predominantly in the bitumen fraction, and all other TEs in the mineral fraction.

Fluorescence spectroscopy is very useful for the characterisation of organic matter in natural water samples. The importance of protein-like fluorescence might be enhanced by several events induced by warming in natural waters such as lake water.

A review that highlights the utility of multi-element compound-specific isotope analysis (CSIA) in halogenated hydrocarbon remediation.

Light-induced reduction of Fe(III) delivers Fe(II) as nutrient or substrate for growth of planktonic or sedimentary organisms. Biological uptake, as well as chemical or microbial oxidation of Fe(II) close this photochemically driven iron cycle.

Electrochemically active microorganisms (EAMs) play an important role in the fields of environment and energy.

This paper summarizes the atmospheric release of Hg, distribution of air Hg concentration, human exposure to MeHg and health impacts caused by Hg pollution in China.

The review presents a way of comparing environmental geochemistry between thioantimony and thioarsenic, summarizing the latest knowledge about their formation, structure and transformation.

Photophysical models for dissolved organic matter optical properties and photochemistry are critically reviewed.

Environmental change is continuing to affect the flow of nutrients, material and organisms across ecosystem boundaries. In this review, we synthesize current knowledge of cross-ecosystem nutrient subsidies between Arctic and alpine lakes and their surrounding terrain, cryosphere, and atmosphere.

A bibliometric analysis of published papers with the key words “positive matrix factorization” and “source apportionment” in ‘Web of Science’, reveals that more than 1000 papers are associated with this research and that approximately 50% of these were produced in Asia.

Dimethyl sulfide (DMS) production in the northern Arctic Ocean has been considered to be minimal because of high sea ice concentration and extremely low productivity.

The uptake of total gaseous mercury (TGM) by Korean forest foliage is mainly affected by local wind speed, boosting its passage and absorption. Mercury levels and isotopic signatures in litter and topsoil fluctuate, particularly in areas with high wind speed, temperature, and low elevation.

To study the geogenic processes of naturally occurring radioactive materials' distribution, a transboundary Himalayan river (Punarbhaba) is chosen due to its trivial anthropogenic impacts.

In aquatic systems, dissolved organic matter (DOM) has important ecological and biogeochemical functions, where the molecular composition of DOM has larger-scale implications for climate change and global carbon cycles.

This study indicates that in alkaline media, carbonate slightly inhibits ferrihydrite transformation and suppresses goethite formation, but promotes hematite formation, which has important implications for elemental biogeochemical cycles.

Despite the importance of structural control on metal stable isotope fractionation in inorganic and abiotic systems, the link between metal structural changes and related isotopic fractionation during reactions with organic surfaces and live cells remains poorly established.

Coccolithophores are biogeochemically and ecologically important phytoplankton that produce calcium carbonate scales, or coccoliths. Here, we show that one species of coccolithophore grows coccoliths with uneven distribution of Sr, in contrast to current fractionation model theory.

We showed that oligotrophic coastal marine areas are susceptible to the deposition of pollen and aerosols from open-fire biomass burning, which alter Cu-binding organic ligands in the sea surface microlayer.

We studied the transformation of ⁵⁷Fe-labelled ferrihydrite and lepidocrocite mixed with a flooded paddy soil by using ⁵⁷Fe-Mössbauer spectroscopy.

The protonation state of dissolved organic matter (DOM) impacts its structure and function in natural and engineered environmental systems, including DOM's ability to absorb light and form photochemically produced reactive intermediates (PPRI).

The soil environment in regions with a high arsenic geological background may have enabled microbial adaptation, through co-selection mechanisms, to withstand the introduction of exogenous antibiotics.

Prehistoric and modern records of Hg in peats from the lower Amur River basin, eastern Asia, were investigated.

Addition of microplastics (MP) to soil has the potential to increase soil water repellency. Absorption of soil abundant substances on MP surfaces has the potential to overcome MP inherent hydrophobicity.

Methylmercury formed in anoxic reservoirs associates with organic-rich particles and is exported downstream.

This study investigates ecological consequences from the combined provenance (natural and manmade) of fifteen metal(oid)s (Na, Al, K, Ti, Cr, Mn, Co, Zn, As, Rb, Sb, Cs, Ba, Th, and U) from a major Indo-Bangla transboundary river (Teesta).

The formation and dynamic partitioning of As species in the water column of a large oligo-mesotrophic lake is driven by biological processes.

The over-use of synthetic nitrogen (N) fertilisers for crop production can cause environmental pollution through leaching and gaseous losses, resulting in low N use efficiency (NUE).

Under global warming, invasive cyanobacteria, can migrate northward and colonize lakes in permafrost-affected territories. This study tests the potential growth of M. aeruginosa onto various organic-rich solutions of those regions.

At mercury (Hg)-contaminated sites, streambank erosion can act as a main mobilizer of Hg into nearby waterbodies.

Cr(III) oxidation and Cr(VI) occurrence corresponds to regions of cation-exchange induced Mn-carbonate dissolution.

Batch sorption–desorption of Zn, Cu, Fe, Mn, B and S onto phyto-biochars prepared from lantana, pine needles and wheat straw by pyrolysis at 300 °C and 450 °C were studied in a multi-ionic system.

Photochemical production of hydrogen peroxide (H₂O₂) may not the dominant source of H₂O₂ in Lake Erie, where toxin-forming harmful algal blooms follow high concentrations of H₂O₂.

The rate and pathway of ferrihydrite transformation in soil depends on the properties of the soil pore water and diffusion processes.

Marine chromophoric dissolved organic matter (m-CDOM) mediates many vital photochemical processes in the surface ocean.

Heteroaggregation of microplastic and ferrihydrite leads to sedimentation and therefore removal of microplastic from the water column.

Beaver ponds act as biological "hotspots" with unique geochemistry and microbiomes in fire-impacted systems.

Microbial processes can be involved in the remobilization of uranium (U) from reduced sediments under O₂ reoxidation events such as water table fluctuations.

Aluminum in schwertmannite structure increases the proportion of covalent bonding with adsorbed arsenates.

Biogeochemical cycling of S, Fe, and C in the hyporheic zone is influenced by dynamic hydrologic conditions.

We studied the extent and mode of thallium adsorption onto several phyllosilicate minerals. Thallium, in analogy to cesium, strongly adsorbs onto micaceous phyllosilicates in soils and sediments via complexation in siloxane cavities.

Porewater geochemistry in a lanthanum-remediated lake reveal that phosphorus mobility depends on the interplay between carbon and iron.

Australian anthropogenic emissions of mercury have decreased by a factor of two since 2000, with implications for atmospheric mercury concentrations and deposition to the Australian continent.

Marine heatwave conditions diminished (micro)macronutrient vertical transport, reducing (micro)macronutrient inventories and net community production when external nutrient sources were absent.

Halogens in soil are closely linked to abiotic processes, biota and pedogenesis, and thus to the availability of water; vertical halogen depth patterns become less pronounced with increasing dryness.

The low molecular weight fraction of peat porewater is enriched in DOC, anions, oxyanions, alkalis and some trace metals. An increase in the active layer depth can liberate a large amount of labile metals and nutrients from the peat.

The distribution and chemical speciation of micronutrient selenium is reported for the first time in twenty alpine lakes (Pyrenees, France–Spain).

A holistic multi-analyses (led by Hg stable isotope analysis), multi-media, multi-site approach to improving contaminated site Hg geochemistry, particularly process tracing.

Including concentration-dependent microbial activity may improve model description of mercury methylation and methylmercury demethylation kinetics.

HA promotes enzymatic hydrolysis of phytate as shown by the increase in nucleation of P_i-bearing particles, which is achieved by conformation change to stabilize a catalytic domain resulting from noncovalent phytase–HA interaction.

Surface precipitation has been shown to occur on rapid time scales in clay and metal oxide mineral systems.

This study shows a feasible cultivation-independent method by MMI coupled with high-throughput sequencing to identify in situ microbes actively, various microbes were recognized for the first time, the OPH genes were involved in CPF metabolism.

DIC generation in carbonate dissolution in acidic granitic-soil is promoted by H₂SO₄, perturbed by HNO₃, little affected by organic acids.

We compared how FTICR-MS characterization of riverine dissolved organic matter varied across four sample pre-treatment and instrument ionization methods to provide guidelines for future researchers utilizing FTICR-MS in environmental analyses.

Schematic showing how voltammetric microelectrodes were used to profile arctic lake sediments, where different locations contained different distributions of redox-active species.

Lake morphometric, chemical, and watershed land-use attributes control lake phosphorus concentration. Lake depth, sediment chemical makeup, DOC, and watershed agricultural extent are the most important controlling variables.

Dissolved organic matter (DOM) can facilitate the transformation of contaminants through the production of reactive intermediates, such as singlet oxygen (¹O₂), and hydroxylating species (˙OH and other intermediates of similar reaction chemistry).

Forest fires are important sources of polycyclic aromatic hydrocarbons (PAHs) in soils.

Nitrogen speciation (NO₃⁻ and NH₄⁺) method from lichen material, using 0.05 g lichen, 3 mL of 3% KCl and 6 hours extraction.

The inorganic components in Bio-CaCO₃ catalyze the deoxygenation of biochar and increase the degree of aromatization of the carbon matrix. The stable pyridinic-N structures are doped into the carbon skeleton, which further improves the stability of biochar.

The origin of groundwater salinity and major hydrogeochemical processes in the LKB aquifer were investigated using hydrogeochemical and HCA methods. The results indicate that evaporitic lacustrine deposits are the major source of salinity in the aquifer.

CH₄ and CO₂ fluxes from Toolik Lake obtained for the first time with eddy covariance during ice-free periods 2010–2015.

Microbial genetic potential for the biotransformation of xenobiotics and antibiotic resistance increases with depth during biofiltration.

Divergent soil biogeochemical conditions will determine the fate and pathways of labile carbon released during permafrost thaw, thereby influencing the production of greenhouse gas mixtures and radiative forcing of tundra soils.

Under anoxic conditions, clay minerals sorb dissolved Mn(II) predominantly by forming surface precipitates, which increase Cd sorption.

Phosphorus cycling in the environment.

Yedoma permafrost soils are especially susceptible to abrupt thaw due to their exceptional thickness and high ice content.

Iron accumulation in shallow tundra soils promotes adsorption of phosphate from soil solution, sequestering high concentrations of potentially bioavailable phosphorus.

Under anoxic conditions, clay minerals sorb dissolved Fe(II) predominantly by forming surface precipitates, which transform into Fe(III)-phases upon aeration.

Isotope tracer experiments reveal that rates of dissolved organic matter partial photochemical oxidation are considerably underestimated in arctic surface waters.