Acid sulfate soils impact surrounding ecosystems with pronounced environmental damage via leaching of strong acidity along with the concurrent mobilization of toxic metals present in the soils and, in consequence, they are often described as the nastiest soils on Earth. Within Sweden, acid sulfate soils are distributed mainly under the maximum Holocene marine limit that stretches the length of the country, some 2000 km north to south. Despite only minor geographical differences in the geochemical composition of the Swedish acid sulfate soils, their field oxidation zone microbial community compositions differ along a north-south regional divide. This study compared the 16S rRNA gene amplicon-based microbial community compositions of field oxidation zones (field tested pH 6.5) collected from the same field sites throughout Sweden that had acidified (final pH = 20 degrees C) greater than what was experienced by the field oxidation zone samples when sampled (similar to 2 degrees C-9 degrees C). These data suggested that in the absence of significant geochemical differences, temperature was the predominant driver of microbial community composition in Swedish acid sulfate soil materials.

Because pineapple is an important crop in Vietnam, it is crucial to assess the nutrition status of the pineapple. Although the diagnosis and recommendation integrated system (DRIS) is a reliable approach, finding the right leaf position to diagnose is vital. Therefore, the aim of the current study is to determine suitable leaf positions for creating DRIS norms for macro- and micronutrients in pineapple leaf. Healthy pineapple leaves without pest or disease damages were sampled from 60 pineapple farms and analyzed for N, P, K, Na, Ca, Mg, Cu, Fe, Zn, and Mn concentrations. The results revealed that the critical yield was 13.3 t ha-1 among the 60 farms, dividing into 23 farms as the high-yielding group (>= 13.3 t ha(-1)) and 37 farms as the low-yielding group (< 13.3 t ha(-1)). The concentrations of mineral nutrients (N, P, K, Ca, Mg, Cu and Zn) and pineapple fruit yields in the high-yielding group were greater than those in the low-yielding one. On the other hand, the Na, Fe, and Mn concentrations showed the opposite pattern. Selected leaf positions must possess significantly different nutrient ratios and have more than 14 nutrient ratio pairs between the two yield groups. Therefore, leaf positions from +15 to +19 were selected to create DRIS norms. Nine sets of DRIS norms have been created at leaf +1, +3, +7, +9, +16, +18, +21, +22, and +29 for plant pineapples.

Soil serves as a primary construction material for roads. Chemical properties of soil, including acidity, and salinity, have the potential to erode concrete, steel structures, road furnishings, and cause land degradation in a vicinity of roads. Acid sulphate soils (ASS) are naturally found in soil sediments and contain iron sulfides, primarily in the form of pyrite. Such soils are typically located in low-lying coastal areas of Australia. Under anerobic conditions, acid sulfate soils do not pose a significant environmental risk. However, when these soils are disturbed by construction activities such as excavation, and temporary or permanent dewatering there is a possibility for the iron sulfides present in the soil to react with oxygen, leading to the generation of sulfuric acid. This acidification process can affect the landscape by lowering its pH and results in releasing of contaminants, including iron, aluminum, and other metals in harmful concentrations. These contaminants have the potential to be transported to waterways, wetlands, and groundwater. Contrary to alkaline soils, acidic soils pose a significant risk to infrastructure, particularly steel or metallic structures. There is a risk of sustained damage to infrastructure over time due to the corrosive effects of acidic water on metallic and concrete structures. Presence of acidic soil can cause decay or absence of roadside vegetation resulting in accelerated soil erosion, leading to substantial and lasting damage to the road structure.

Imbalanced datasets are one of the main challenges in digital soil mapping. For these datasets, machine learning techniques commonly overestimate the majority classes and underestimate the minority ones. In general, this generates maps with poor precision and unrealistic results. Considering these maps for land use decisionmaking can have dire consequences. This is the case of acid sulfate (AS) soils, a type of harmful soil that can generate serious environmental damage when drained in agricultural or forestry activities. Therefore, it is necessary to create high-precision maps to avoid environmental damage. Although most soil class datasets in nature are imbalanced, this problem has hardly been studied. One of the main objectives of this work is the evaluation of different techniques to address the problem of imbalanced datasets. The methods considered to balance the dataset are an undersampling technique, the addition of more samples, and the combination of both. For increasing the number of samples from the minority class, we develop a new technique by creating artificial samples from the quaternary geological map. The method used for the modeling is Random Forest, one of the best methods for the classification of AS soils. Balancing the dataset improves the performance of the model in all the studied cases, where the values of the metrics for both classes are above 80%. The consideration of artificial non-AS soil samples improves the prediction of the model for the AS soils. Furthermore, we create AS soil probability maps for the four balanced datasets and the imbalanced dataset. The modeled AS soil probability maps created from the balanced datasets have high precision. A detailed comparison between the maps is made. The predictions of some of these maps match between 75%-80% of the study area. In addition, the extent of the AS soils obtained in all the cases is compared with the extent of the AS soils in the conventionally produced occurrence map. The good results of this study confirm the importance of balancing the dataset to improve the prediction and classification of AS soils.

This study offers an analytical solution for radial consolidation that captures the biogeochemical clogging effect in acid sulfate soils. Field sites and personal communication with industry practitioners have provided evidence of piezometers exhibiting retarded pore pressure readings that do not follow conventional soil consolidation and seepage principles when installed in coastal acidic floodplains. This retarded response together with a variation in pH, ion concentrations, and piezometric heads provided evidence of clogging at and around the piezometers. This paper uses the proposed biogeochemical clogging model, which is an analytically derived system of equations to estimate the excess pore water pressure dissipation of piezometers installed in clogging-prone acid sulfate soils. The inclusion of the total porosity reduction attributed to biological and geochemical clogging improves the predictions of the retarded dissipation of excess pore pressure, especially after about 1 year. This method is validated for two previously identified acidic field sites in coastal Australia, where piezometers measured a very slow rate of dissipation. It is concluded that this model has potential to accurately monitor the performance of critical infrastructure, such as dams and embankment foundations built on acidic terrain.

Coastal wetland soils are frequently underlain by sulfidic materials. Sea level fluctuations can lead to oxidation of sulfidic materials in acid sulfate soils (ASS) and increased acidity which mobilises trace metals when water levels are low, and inundation of coastal wetland soils and reformation of sulfidic materials when water levels are high. We measured the effect of surface water level fluctuations in soils from coastal wetland sites under four different vegetation types: Apium gravedens (AG), Leptospermum lanigerum (LL), Phragmites australis (PA) and Paspalum distichum (PD) on an estuarine floodplain in southern Australia. We assessed effects of fluctuating water levels on reduced inorganic sulfur (RIS) in terms of acid volatile sulfide (AVS), chromium reducible sulfur (CRS) and trace metals (Fe, Al, Mn, Zn, Ni). Intact soil cores were incubated under dry, flooded and wet-dry cycle treatments of 14 days for a total of 56 days. The flooded treatment increased RIS concentrations in most depths in the AG, PA and PD sites. Lower CRS concentrations occurred in all sites in the dry treatment due to oxidation of sulfidic materials when the surface layer was exposed to lower water levels. CRS was positively correlated with SOC in all treatments. The highest net acidity occurred in the dry treatment and lowest occurred in the flooded treatment in most sites. Inundation with seawater caused SO42- reduction and decreased soluble Fe in the PA and PD sites. General decreases in Al, Zn and Ni concentrations in flooded treatments may have been due to adsorption onto colloids or co-precipitation with slight increases in pH. SO42- concentrations decreased in the LL, PA and PD sites in the flooded treatment due to reformation of pyrite. In general, accumulation of RIS in soils under different vegetation types following brackish water inundation varied according to vegetation type, which may be linked to differences in organic material input and particle size distribution. Geochemical characteristics reflected whether oxidation or reduction processes dominated at each site in the wet-dry cycle treatments, with oxidation dominating in the LL and PA sites and reduction dominating in the AG and PD sites. This is likely due to more readily decomposable organic matter forming sulfidic materials during short periods of inundation.