Health condition assessment for vegetation exposed to heavy metal pollution through airborne hyperspectral data.

Recent advancements in hyperspectral remote sensing technology now provide improved diagnostic capabilities to assess vegetation health conditions. This paper uses a set of 13 vegetation health indices related to chlorophyll, xanthophyll, blue/green/red ratio and structure from airborne hyperspectral reflectance data collected around a derelict mining area in Yerranderie, New South Wales, Australia. The studied area has ten historic mine shafts with a legacy of heavy metals and acidic contamination in a pristine ecosystem now recognised as Great Blue Mountain World Heritage Area. The forest is predominantly comprised of different species of Eucalyptus trees. In addition to the airborne survey, ground-based spectra of the tree leaves were collected along the two accessible heavy metal contaminated pathways. The stream networks in the area were classified and the geospatial patterns of vegetation health were analysed along the Tonalli River, a major water tributary flowing through the National Park. Despite the inflow of contaminated water from the near-mine streams, the measured vegetation health indices along Tonalli River were found to remain unchanged. The responses of the vegetation health indices between the near-mine and away-mine streams were found similar. Based on the along-stream and inter-stream analysis of the spectral indices of vegetation health, no significant impact of the heavy metal pollution could be noticed. The results indicate the possibility of the vegetation having developed immunity towards the high levels of heavy metal pollution over a century of exposure.

Dynamics of carbon sequestration in vegetation affected by large-scale surface coal mining and subsequent restoration.

Surface coal development activities include mining and ecological restoration, which significantly impact regional carbon sinks. Quantifying the dynamic impacts on carbon sequestration in vegetation (VCS) during coal development activities has been challenging. Here, we provided a novel approach to assess the dynamics of VCS affected by large-scale surface coal mining and subsequent restoration. This approach effectively overcomes the limitations imposed by the lack of finer scale and long-time series data through scale transformation. We found that mining activities directly decreased VCS by 384.63 Gg CO2, while restoration activities directly increased 192.51 Gg CO2 between 2001 and 2022. As of 2022, the deficit in VCS at the mining areas still had 1966.7 Gg CO2. The study highlights that complete restoration requires compensating not only for the loss in the year of destruction but also for the ongoing accumulation of losses throughout the mining lifecycle. The findings deepen insights into the intricate relationship between coal resource development and ecological environmental protection.

Effect of crop cultivation on the soil carbon stock in mine dumps of the Loess Plateau, China.

In the ecological restoration of mine dumps, soil carbon stock (SCS) improvement is an important issue. The type of land use and management approach taken can have a great influence on this issue. On the Loess Plateau, different crops have been cultivated on reclaimed land; however, the effect of long-term crop cultivation on SCS is poorly understood. To address this issue, a field investigation of mine dumps was performed at the Kee Open Pit Mine in Shanxi Province, China. Four sites utilizing different land management methods were analyzed: no reclamation (NR), reclamation with no crop cultivation (NC), and reclamation followed by 11 or 27 years crop cultivation (RC-11 and RC-27, respectively). SCS, associated soil properties (total nitrogen (TN), total phosphorus (TP), total potassium (TK), moisture content (MoiC), and pH), plant community (species composition, plant diversity, and traits), and microbial community operational taxonomic units (OTUs) of fungi and bacteria were determined by field investigation and laboratory analysis. Redundancy analysis was used to show the relationship between SCS and other environmental variables. Results varied by soil depth. At the depth range of 0-20 cm, the SCS of RC-11 was significantly greater compared to that in NR and NC, by 14.64- and 2.25-fold, respectively; whereas compared to RC-27, it was higher by 52.78%. At the depth of 20-40 cm, NC has the largest SCS; the SCS of RC-27 was the lowest, which was less compared to that in NC by 43.64%. Redundancy analysis showed a positive relationship between the SCS and TN, TP, MoiC, as well as average plant coverage, while the bacterial OTUs were negatively related with the SCS. This research suggests the potential of mine dumps for crop cultivation, which could improve the SCS of the mining area on the Loess Plateau.

Acid mine drainage formation and arsenic mobility under strongly acidic conditions: Importance of soluble phases, iron oxyhydroxides/oxides and nature of oxidation layer on pyrite.

Acid mine drainage (AMD) formation and toxic arsenic (As) pollution are serious environmental problems encountered worldwide. In this study, we investigated the crucial roles played by common secondary mineral phases formed during the natural weathering of pyrite-bearing wastes-soluble salts (melanterite, FeSO4·7H2O) and metal oxides (hematite, Fe2O3)-on AMD formation and As mobility under acidic conditions (pH 1.5-4) prevalent in historic tailings storage facilities, pyrite-bearing rock dumps and AMD-contaminated soils and sediments. Our results using a pyrite-rich natural geological material containing arsenopyrite (FeAsS) showed that melanterite and hematite both directly-by supplying H+ and/or oxidants (Fe3+)-and indirectly-via changes in the nature of oxidation layer formed on pyrite-influenced pyrite oxidation dynamics. Based on SEM-EDS, DRIFT spectroscopy and XPS results, the oxidation layer on pyrite was mainly composed of ferric arsenate and K-Jarosite when melanterite was abundant with/without hematite but changed to Fe-oxyhydroxide/oxide and scorodite when melanterite was low and hematite was present. This study also observed the formation of a mechanically 'strong' coating on pyrite that suppressed the mineral's oxidation. Finally, As mobility under acidic conditions was limited by its precipitation as ferric arsenate, scorodite, or a Fe/Al arsenate phase, including its strong adsorption to Fe-oxyhydroxides/oxides.