Gas-geochemical studies of the methane, helium, and hydrogen concentrations in the water of thermal and mineral springs, as well as the subsurface atmosphere, of northern Vietnam showed that the region is in the hypabyssal degassing zone of hydrogen and helium flowing to the surface through a fault system in the Earth’s crust. A joint transit of these gases through the fault structures was established. Distribution pattern of hydrogen and helium concentrations in the Red River Rift area (northern Vietnam) was obtained from the extensive gas and water sample data. Intense linear anomalies are associated with the Red River Rift and the Dien Bien regional rift. Seismic events are associated with the fault, and earthquake epicenters are located in the Dien Bien Province.

Our paper deals with gas-geochemical measurements of CH₄ and CO₂, as well as the first measurements of dissolved H₂ and He in the waters of the eastern shelf of Sakhalin Island, obtained during cruise 68 on the R/V Akademik Oparin (OP68) on 12–18 August 2023. The shallow eastern shelf has high concentrations of dissolved methane and helium in the water. The combined anomalies of methane and helium indicate the presence of an ascending deep fluid. The sources of methane in the studied area are the underlying oil- and gas-bearing rocks extending to the coast of the island. The deep faults of the region and the minor discontinuities that accompany them along the eastern coast of Sakhalin Island create a fluid-permeable geological environment both on the shallow shelf and on the coastal part of the island. East Sakhalin current and counter-current influence gases that migrate from lithospheric sources; these currents form a special hydrological regime that ensures high solubility of the gases released and their transfer under the lower boundary of the seasonal pycnocline to the east, where they are involved in the general circulation of the Sea of Okhotsk.

Within the framework of the expedition research “Complex studies of the Antarctic marine ecosystem in the areas of the transport and interaction of water masses in the Atlantic sector of Antarctica, the Scotia Sea and the Drake Strait” (cruise 87 of the R/V “Academik Mstislav Keldysh”, 7 December 2021–5 April 2022), the distribution of gas-geochemical fields of methane in the Bransfield Strait was studied in detail for the first time. The connection of the methane distribution in water with the complex hydrological regime of the strait has been revealed. Elevated values of methane concentrations brought to the Bransfield Strait in the warm current flow from the Bellingshausen Sea have been established. Low concentrations of methane also mark the cold waters of the Weddell Sea, which carry out the transit of water masses into the Atlantic Ocean. The research was carried out within the framework of the theme FWMM-2022-033 “Integrated environmental studies of the Southern Ocean” AAAA17-117030110035-4 and international obligations of the Russian Federation as a party to the Antarctic Treaty and the Convention on the Conservation of Antarctic Marine Living Resources.

Dissolved methane coming from its various sources is an important component of seawater. Finding these probable sources allows for the determination of potential oil and/or gas deposit areas. From an ecological point of view, methane transport studies can reveal probable pollution areas on the one hand and biological communities, being the lower part of the food chain commercial species, on the other hand. Moreover, the methane transport mechanism can help to obtain a better understanding of the contribution of the World’s oceans to global greenhouse gas emissions. Our research combines gas geochemistry and oceanography. In comparing the research results of both branches, we show the mechanism of methane transport. The features of the dissolved methane on oceanographic sections in the southern part of the Tatar Strait are discussed. The CH₄ intake from the bottom sediment and the transport of dissolved methane by the currents in the Tatar Strait are shown. The absolute maximum concentration of CH₄ (155.6 nM/L) was observed on the western Sakhalin Island shelf at the near-bottom layer at a depth of 65 m. The local maximum, 84.4 nM/L, was found north of the absolute maximum in the jet current under the seasonal pycnocline. A comparison of the simulated surface seawater origin and dissolved methane in the 4 m depth distribution shows methane transport with the currents in the Tatar Strait. Another studied section is along 134° E in the Japan Basin of the Japan (East) Sea. Here, the East Korean Warm Current close to the Yamato Rise slope and a quasi-stationary mesoscale anticyclonic eddy centered at 41° N intersect. The local maximum methane concentration of 8.2 nM/L is also observed under the seasonal pycnocline. In a mesoscale anticyclonic eddy at 134° E in the deep part of the Japan Basin, a local methane maximum of 5.2 nM/L is detected under the seasonal pycnocline as well.

Vietnam is a country with diverse and abundant mineral resources with nearly 5000 mines and ore spots of about 60 different minerals. Mining and processing of mineral resources have contributed about 9.6–10.6% of the country’s GDP since the year of 2000. However, the exploitation and processing of mineral resources have been leading to a certain soil and sediment contamination by heavy metals. Soil and sediment samples around lead-zince mines have been collected and analyzed for Cu, Zn, As, Cd, Hg, Pb and Ni in Cho Don district, Bac Kan province, Vietnam. Single pollution, geoaccumulation and enrichment indices have been used for assessing the sediment quality in terms of heavy metals by comparison with threshold and ecological risk limits. High concentration of Cu and Zn in the sediment is due to extremely high content of the two metals in the ore-surrounding soil in the lead-zinc mines, i.e. high background values. High concentration of As and Cd in the sediment is affected in a greater extent by high content of the two metals in the ore-surrounding soil in the lead-zinc mines, and in a lesser extent by contamination due to geoaccumulation and enrichment. High Pb concentration in sediment is affected in a greater extent by high content of the metal in the ore-surrounding soil in the lead-zinc mines, and in a lesser extent by contamination due to geoaccumulation and enrichment. The pollution sequence based on an average single pollution index is Pb(125.76) > As(55.48) > Zn(26.82 > Cd(14.17) > Cu(5.08) > Ni(1.36) > Hg(0.42), while based on the average geoaccumulation index, the sediment is mostly uncontaminated with the sequence Cd(1.1) > As(0.7) > Cu, Zn, Hg, Pb, Ni( Hg(4.1) > Pb(1.4) > Cu(0.9) > Ni(0.6). The results highlight the need for a comprehensive and detailed study program on heavy metal content in different soil and sediment resources to identify the magnitude and details of the problem associated with heavy metal contamination for development of a remediation plan and more effective pollution preventing measures including technology develop for recovering of useful components.