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Neogloboquadrina pachyderma(sinistral), the dominant planktonic foraminiferal species in the mid-to-high latitude oceans, represents a major component of local calcium carbonate (CaCO3) production. However, the predominant factors, governing the calcification of this species and its potential response to the future marine environmental changes, are poorly understood. The present study utilized an improved cleaning method for the size-normalized weight (SNW) measurement to estimate the SNW of N. pachyderma(sin.) in surface sediments from the Amundsen Sea, the Ross Sea, and the Prydz Bay in the Antarctic Zone of the Southern Ocean. It was found that SNW of N. pachyderma(sin.) is not controlled by deep-water carbonate dissolution post-mortem, and can be therefore, used to reflect the degree of calcification. The comparison between N. pachyderma(sin.) SNW and environmental parameters (temperature, salinity, nutrient concentration, and carbonate system) in the calcification depth revealed that N. pachyderma(sin.) SNWs in the size ranges of 200–250, 250–300, and 300–355 µm are significantly and positively correlated with seawater temperature. Moreover, SNW would increase by ∼30% per degree increase in temperature, thereby suggesting that the calcification of N. pachyderma(sin.) in the modern Antarctic Zone of the Southern Ocean is mainly controlled by temperature, rather than by other environmental parameters such as ocean acidification. Importantly, a potential increase in calcification of N. pachyderma(sin.) in the Antarctic Zone to produce CaCO3will release CO2into the atmosphere. In turn, the future ocean warming will weaken the ocean carbon sink, thereby generating positive feedback for global warming.

The injection of circulating fluids (usually water) is the predominant means of heat extraction in an enhanced geothermal system (EGS); however, the additional injection of circulating fluids can cause a water-rock reaction with a dry thermal rock mass, resulting in the generation of a large number of secondary minerals. These secondary minerals cause fracture closure in artificial reservoirs and severely impede the sustainable use of these geothermal systems. Therefore, this study combined laboratory tests with a PHREEQC hydrogeochemical simulation. First, the changes and mechanisms of mineral and aqueous chemical fractions in the artificial reservoir fractures were analyzed after using groundwater from the sandstone aquifer at the Frontier Observatory for Geothermal Energy Research (FORGE) site as a heat transfer fluid in the FORGE project. Second, the dissolution patterns and precipitation of minerals commonly found in artificial fractures were simulated in four different environments with the aid of PHREEQC after completing transconversion. Finally, the effects of different fluids were evaluated for the unblocking of typical minerals. The results show that as a heat transfer fluid, groundwater causes the dissolution of K-feldspar, albite, and illite, partial decomposition of kaolinite and proto-silicate, rapid production of anorthite, decomposition of dolomite, sodization of Ca-montmorillonite, and dolomitization of black mica. Mud acid was more effective in unblocking fissure closures caused by anorthite, chlorite, and kaolinite. NaOH was more effective in unblocking fissure closures caused by illite and Ca-montmorillonite. Groundwater is not suitable as a blockage remover and can easily produce secondary mineral blockages (calcite and aragonite). The effect of ultrapure water is relatively stable; it can be used as a heat exchange fluid or blockage remover, but when used as a remover, it behaves primarily as a physical-mechanical action process.