Structures constructed on collapsible soil are prone to failure under flooding. Agro-waste like rice husk ash (RHA) and its geopolymer (LGR), consisting of lime (L), RHA, water glass (Na2SiO3), and caustic soda (NaOH), present a potential solution to address this issue. RHA and LGR were mixed up to 16% to improve the collapsible soil. Samples were remolded at optimal water content and maximum dry density for strength and collapsible potential tests. Unconfined compressive strength, deformation modulus, and soaked California bearing ratio exhibit exponential improvement with the inclusion of LGR. Additionally, for comparison of microstructural characteristics, analyses involving energy-dispersive X-ray spectroscopy (EDAX) and scanning electron microscope (SEM) were conducted on both virgin and treated specimens. LGR resulted in the emergence of new peaks of sodium silicates and calcium silicates, as indicated by EDAX. The formation of H-C-A-S gel and H-N-A-S gel observed in SEM suggests the development of bonds among soil particles attributed to geopolymerization. SEM reveals the transformation of the inherent collapsible soil from a dispersed and silt-dominated structure to a reticulated structure devoid of micro-pores following the incorporation of LGR. A numerical model was constructed to forecast the performance of both virgin and stabilized collapsible soils under pre- and post-flooding conditions. The outcomes indicate an enhancement in the soil's bearing capacity upon stabilization with 12% LGR. The implementation of 12% LGR significantly resulted in a lower embodied energy-tostrength ratio, emissions-to-strength ratio, and relatively lower cost-to-strength ratio compared to the soil treated with 16% cement kiln dust (CKD). (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/

Reducing agricultural carbon emissions (ACEs) is critical to achieving green agriculture in China. Chinese agriculture has long faced the dilemma of large numbers of people and small landholdings, well as low-quality arable land. As a result, agricultural production relies heavily on inputs of agricultural chemicals to boost yields, damaging the rural environment. In this study, we use provincial panel data from China and a spatial difference-in-differences model to explore the influence of rural land consolidation policy (RLCP) on ACEs and their spatial spillover effects. The results show that the global Moran's of ACEs reflected a downward trend, the spatial correlation gradually weakened, and ACEs developed from a state of polarization to one of balance. RLCP has had a significant reduction and a negative spatial spillover effect on ACEs. Our analysis of the mechanism shows that rural land consolidation promoted the reduction of ACEs by improving the quality of farmland soil and the utilization rate of water resources. Under different geographical conditions, the construction of rural land consolidation has had a significant ACE reduction effect on both the south and the north, although RLCP in southern China has had a negative spatial spillover effect.

Recycled concrete aggregate (RCA) is a voluminous solid waste material derived from the construction sector and is typically stockpiled in landfills. In recent years, the ground improvement industry has grappled with challenges stemming from the depletion of natural quarry materials, resulting in a skyrocketing of their prices and increased project costs. This research investigated the feasibility of using RCA stabilized by one-part geopolymers to produce an innovative semi-rigid inclusion column system for ground improvement of soft soils. Na2SiO3anhydrous was used as a sole solid activator for the activation of fly ash (FA), slag (S) or a binary precursor (FA+S) in the stabilization of RCA. The unconfined compressive strength (UCS) and microstructure of the stabilized mixtures have been examined with respect to different binder formulations and curing conditions. The permanent deformation characteristics of mixtures under cyclic loading were evaluated through repeated load triaxial (RLT) tests to replicate the moving wheel loads imposed on the semi-rigid inclusion columns. In addition, the cost and environmental impacts of the optimum mixtures suggested in this research were studied. The test results indicated that stabilizing RCA with as low as 5% one-part alkali-activated FA, S or (FA+S) met the minimum strength requirement (1.034 MPa) for ground improvement work. Compared with standalone FA and S geopolymer stabilized RCA mixtures, (FA+S) geopolymer stabilized RCA mixtures were identified as preferred industrial formulations due to their prolonged setting time for ease of mixing and handling when used in stone column applications. It was found that curing temperature and duration played a pivotal role in the strength gain of the mixtures. The RLT test results demonstrated that implementing the optimum RCA + 5%(FA+S) mixture as identified in this study for semi-rigid inclusion columns, led to a reduction in permanent strain values by approximately 90% compared to conventional unbound stone columns. The comparison between the optimum mixture highlighted in this study with other stabilization methods showed that the semi-rigid inclusion columns had great potential to enable large-scale production, cost and emission reduction in future ground improvement projects.

Purpose Warming-induced permafrost degradation is anticipated to change the global carbon cycle. We attempted to determine the effect of permafrost degradation on carbon emissions and carbon sequestration of seven wetlands in three zones of Northeast China, aiming to investigate the responses of carbon sources/sinks to permafrost degradation. Methods Three zones (permafrost zone, PZ; discontinuous permafrost zone, DPZ; and permafrost degradation zone, PDZ) were selected to represent permafrost degradation stages. In each zone, we selected seven wetlands along the moisture gradient, namely, marsh (M), thicket swamp (TS), forested swamps (alder swamp, FAS; birch swamp, FBS; and larch swamp, FLS), forested fen (larch fen, FLF), and forested bog (larch bog, FLB). We determined the annual carbon emissions of soil heterotrophic respiration from seven wetlands and the annual net carbon sequestration of vegetation, evaluated the net carbon balance by calculating the difference between annual net carbon sequestration and annual carbon emissions, and then determined the magnitude and direction of carbon-climate feedback. Results and discussion With permafrost degradation, most forested wetlands (excluding FAS in PDZ) still acted as carbon sinks in DPZ (0.30 - 1.88 t ha(-1) year(-1)) and PDZ (0.31 - 1.76 t ha(-1) year(-1)) in comparison to PZ (0.46 - 2.43 t ha(-1) year(-1)). In contrast, M and TS acted as carbon sources in DPZ (-1.72 and -0.82 t ha(-1) year(-1)) and PDZ (-2.66 and -0.98 t ha(-1) year(-1)) in comparison to PZ (-0.86 and 0.03 t ha(-1) year(-1)), this result could be attributed to the increased CO2 emissions (promoted by warmer soil temperatures) and CH4 emissions (promoted by warmer soil temperatures, higher water tables and greater thaw depths), the two significantly increased the annual carbon emissions (increased by 8.8 - 14.4% in DPZ and by 35.0 - 46.0% in PDZ), and the annual carbon emissions > the annual net carbon sequestration. Furthermore, in terms of net radiative forcing, five forested wetlands still showed negative net radiative forcing in DPZ (-6.90 to -1.10 t CO2-eq ha(-1) year(-1)) in comparison to PZ (-8.91 to -1.62 t CO2-eq ha(-1) year(-1)). In contrast, in PDZ, only FLB showed negative net radiative forcing (-6.29 t CO2-eq ha(-1) year(-1)) and significantly increased by 288.3% compared to PZ (P < 0.05), indicating an ever-increasing net cooling impact, while the other four forested wetlands all turned into positive net radiative forcing (0.84 - 53.56 t CO2-eq ha(-1) year(-1)) because of higher CH4 (CO2-eq) emissions, indicating net warming impacts. Conclusions Our results indicated that permafrost degradation affected the carbon sources/sinks of seven wetlands via different mechanisms. M and TS acted as carbon sources in both DPZ and PDZ, while permafrost degradation did not change the overall direction of the net carbon balance of five forested wetlands. Most forested wetlands (excluding FAS in PDZ) still acted as carbon sinks in both DPZ and PDZ, although there were fluctuations in carbon sink values. Moreover, despite being carbon sinks, most forested wetlands (excluding FLB) in PDZ showed positive net radiative forcing compared to DPZ and PZ (negative net radiative forcing) when using the methodology of CO2 equivalent, indicating climatic warming impacts, while FLB showed negative net radiative forcing, indicating a climatic cooling impact. Therefore, FLB should be protected as a priority in the subsequent carbon sink management practices in permafrost zones.

Permafrost peatlands, as large soil carbon pools, are sensitive to global warming. However, the effects of temperature, moisture, and their interactions on carbon emissions in the permafrost peatlands remain unclear, when considering the availability of soil matrixes. The permafrost peatland (0-50 cm soil) in the Great Xing'an Mountains was selected to explore the deficiency. The cumulative carbon dioxide (CO2) and methane (CH4) emissions from soil were measured under different temperatures (5 C, 10 C, and 15 C) and moisture content (130%, 100%, and 70%) treatments by the indoor incubation. The results showed that the soil carbon and nitrogen matrix determined soil carbon emissions. Warming affected the availability of soil carbon and nitrogen substrates, thus stimulating microbial activity and increasing soil carbon emissions. With soil temperature increasing by 10 C, soil CO2 and CH4 emission rates increased by 5.1-9.4 and 3.8-6.4 times respectively. Warming promoted soil carbon emissions, and the decrease of moisture content promoted CO2 emissions but inhibited CH4 emissions in the permafrost peatland. Soil moisture and the carbon and nitrogen matrix determined the intensity of CO2 and CH4 emissions. The results were important to assess soil carbon emissions from permafrost peatlands under the impact of future climate warming and to formulate carbon emission reduction policies.

Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008. We find that this hiatus in warming coincides with a period of little increase in the sum of anthropogenic and natural forcings. Declining solar insolation as part of a normal eleven-year cycle, and a cyclical change from an El Nino to a La Nina dominate our measure of anthropogenic effects because rapid growth in short-lived sulfur emissions partially offsets rising greenhouse gas concentrations. As such, we find that recent global temperature records are consistent with the existing understanding of the relationship among global surface temperature, internal variability, and radiative forcing, which includes anthropogenic factors with well known warming and cooling effects.

Agricultural open burning, that is, the practice of burning crop residue in harvested fields to prepare land for sowing a new crop, is well recognized as a significant contributor to CO2 and black-carbon emissions, and long-term climate change. Low-soiltillage practices using an agricultural machine called the Happy Seeder, which can sow the new seed without removing the previous crop residue, have emerged as the most effective alternative to open burning. However, given the limited supply of Happy Seeders from the government, and the fact that farmers incur a significant yield loss if they delay sowing the new crop, farmers are often unwilling to wait to be processed by the Happy Seeder and, instead, burn their crop residue. We study how the government can use effective information-disclosure policies in the operation of Happy Seeders to minimize open burning. A Happy Seeder is assigned to process a group of farms. The government knows, but does not necessarily disclose, the Happy Seeder's schedule at the start of the sowing season. We propose a class of information-disclosure policies, called dilatory policies, that provide no information to the farmers about the schedule until a prespecified switch period and then reveal the entire schedule afterward. We show that an optimal dilatory policy can significantly lower the number of farms burnt compared with that under the full-disclosure and the no-disclosure policies. Using data from the rice-wheat crop system in northwestern India, we demonstrate that the optimal dilatory policy can reduce CO2 and black-carbon emissions by 17% on average. We also examine the impact of the government's policy on the trade-off between environmental damage and farmers' welfare.