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Purpose: The current study aimed to figure out the types and dosages of biocomposts supplied with cellulose-degrading Trichoderma strains for ameliorating soil properties, and the growth and yield of pineapple. Method: The experiment with two factors followed a completely randomized block design, including 20 treatments (4 replications). The first factor (A) was the types of biocomposts inoculated with different Trichoderma spp., which were (i) the biocompost supplied with the commercial Trichoderma (the Trichoderma of Can Tho University) as the positive control treatment, and the biocompost supplied with Trichoderma strains of (ii) TC1 (TC1 biocompost), (iii) TC2 (TC2 biocompost), (iv) TC3 (TC3 biocompost), and (v) TC1, TC2, and TC3 (TC123 biocompost). The second factor (B) was rates of bio-compost used (t ha-1) as follows: (i) 1, (ii) 2, (iii) 3, and (iv) 4. Results: The application of TC123 bio-compost at 4 t ha-1 contributed to the greatest available N, soluble P, concentrations, and N, P, and K uptake values. The treatments with the TC123 biocompost correspondingly increased plant height, leaf number, D-leaf length, peduncle height, fruit length, and fruit width by 1.9, 31.8, 16.7, 5.4, 7.8, and 12.1%, in comparison with the treatments with the positive control. The TC123 biocompost fertilization increased fruit size, resulting in enhanced pineapple yield by 9.80% in comparison with the commercial biocompost fertilization. Conclusion: The TC123 biocompost surpassed the commercial one in enhancing the characteristics of pineapples (Ananas comosus (L.) Merr). At 4 t.ha-1, this biocompost performed the greatest.

Purpose: The current study aimed to figure out the types and dosages of bio-composts supplied with cellulose degrading Trichoderma strains for ameliorating soil properties, and the growth and yield of pineapple. Method: The experiment with two factors followed a completely randomized block design, including 20 treatments (4 replications). The first factor (A) was the types of bio-composts inoculated with different Trichoderma spp., which were (i) the bio-compost supplied with the commercial Trichoderma (the Trichoderma of Can Tho University) as the positive control treatment, and the bio-compost supplied with Trichoderma strains of (ii) TC1 (TC1 bio-compost), (iii) TC2 (TC2 bio-compost), (iv) TC3 (TC3 bio-compost), and (v) TC1, TC2, and TC3 (TC123 bio-compost). The second factor (B) was rates of bio-compost used (t ha-1) as follows: (i) 1, (ii) 2, (iii) 3, and (iv) 4. Results: The application of TC123 bio-compost at 4 t ha-1 contributed to the greatest available N, soluble P, concentrations, and N, P, and K uptake values. The treatments with the TC123 bio-compost correspondingly increased plant height, leaf number, D-leaf length, peduncle height, fruit length, and fruit width by 1.9, 31.8, 16.7, 5.4, 7.8, and 12.1%, in comparison with the treatments with the positive control. The TC123 bio-compost fertilization increased fruit size, resulting in enhanced pineapple yield by 9.80% in comparison with the commercial bio-compost fertilization. Conclusion: The TC123 bio-compost surpassed the commercial one in enhancing the characteristics of pineapples (Ananas comosus (L.) Merr). At 4 t.ha-1, this bio-compost performed the greatest. [ABSTRACT FROM AUTHOR]

The study was aimed to assess the potency of nitrogen (N)-fixing purple non-sulfur bacteria (NF-PNSB) on ameliorating soil quality, N uptake, and yield of pineapple in acid sulfate soil. The experiment, following a completely randomized block design, had two factors: (i) supplementation of biofertilizers containing the NF-PNSB (No applied bacteria, Rhodobacter sphaeroides W15, W39, and a mixture of both W15 and W39) and (ii) levels of N fertilizer [0, 50, 75, and 100% N of recommended fertilizer formula (RFF)]. Results demonstrated that supplying biofertilizers containing the mixture of both W15 and W39 increased the values of pHH2O and NH4+, and decreased the values of EC, Al3+, and Fe2+ at a soil depth of 0-20 cm, in comparison with the no supplied biofertilizers, by 15.8, 39.9, 26.9, 17.8, and 52.9%, respectively. Applying biofertilizers enhanced the total N uptake by 28.9%, resulting in greater growth and a 22.9% increase in pineapple yield, in comparison with the no biofertilizers supplied treatments. Supplying the two strains W15 and W39 not only contributed to reducing 25% N of RFF but also preserved the pineapple yield, compared to the fertilizing 100% N of RFF. Both W15 and W39 are potent for use as crop yield enhancers. [ABSTRACT FROM AUTHOR]

The iron concentration in natural water of acid sulfate soils is usually determined by complicated methods of SMEWW 3111B:2017 or ISO 6332: 1988 E in the laboratory for acidified water samples at pH ∼2–3. Therefore, the rapid field determination of iron content in natural water is a very useful method because it limits the error and reduces the experimental time for analysis. In this study, we proposed, developed, and tested a rapid colorimetric analysis method based on the chemical reaction of ferric and anion thiocyanate (SCN−) ions for an iron concentration range of 0–100 mg/L with a linear equation of ΔE = 0.5955x + 2.0909 and high correlation coefficient (R2) of 0.9864. The results from 10 water samples by this method were very close to those by flame absorption spectroscopy with a difference of less than 5%. Besides the biggest advantage of rapid site testing, this method also gives quite high accuracy compared to the molecular absorption method of ISO 6332:1988 E. In addition, this new method can quantify Fe3+, Fe2+, and total iron in water, suggesting a very useful and potential method for determining the iron content of natural water from acid sulfate soils. HIGHLIGHTS A color chart was developed to determine iron in water using indicator paper.; A linearity of the iron content was obtained with a concentration below 100 mg/L.; The method gives relatively fast and accurate results of Fe2+, Fe3+, and total iron.; The tested results show high accuracy and sensitivity in natural iron alum water.;

As critical transition zones between the land and the sea, estuaries are not only hotspots of hydrogeochemical and microbial processes/reactions, but also play a vital role in processing and transferring terrestrial fluxes of metals and nutrients to the sea. This study focused on three estuaries in the Gulf of Bothnia. All of them experience frequent inputs of acidic and Mn/metal-rich creek waters due to flushing of acid sulfate soils that are widespread in the creekś catchments. Analyzing existing long-term water chemistry data revealed a strong seasonal variation of Mn loads, with the highest values in spring (after snow melt) and autumn (after heavy rains). We sampled surface waters, suspended particulate matter (SPM), and sediments from the estuarine mixing zones and determined the loads and solid-phase speciation of Mn as well as the composition and metabolic potentials of microbial communities. The results showed that the removal, cycling, and lateral transport of Mn were governed by similar phases and processes in the three estuaries. Manganese X-ray absorption spectroscopy data of the SPM suggested that the removal of Mn was regulated by silicates (e.g., biotite), organically complexed Mn(II), and MnOx (dominated by groutite and phyllomanganates). While the fractional amounts of silicate-bound Mn(II) were overall low and constant throughout the estuaries, MnOx was strongly correlated with the Mn loadings of the SPM and thus the main vector for the removal of Mn in the central and outer parts of the estuaries, along with organically complexed Mn(II). Down estuary, both the fractional amounts and average Mn oxidation state of the MnOx phases increased with (i) the total Mn loads on the SPM samples and (ii) the relative abundances of several potential Mn-oxidizing bacteria (Flavobacterium, Caulobacter, Mycobacterium, and Pedobacter) in the surface waters. These features collectively suggested that the oxidation of Mn, probably mediated by the potential Mn-oxidizing microorganisms, became more extensive and complete towards the central and outer parts of the estuaries. At two sites in the central parts of one estuary, abundant phyllomanganates occurred in the surface sediments, but were converted to surface-sorbed Mn(II) phases at deeper layers (>3–4 cm). The occurrence of phyllomanganates may have suppressed the reduction of sulfate in the surface sediments, pushing down the methane sulfate transition zone that is typically shallow in estuarine sediments. At the outermost site in the estuary, deposited MnOx were reduced immediately at the water–sediment interface and converted most likely to Mn carbonate. The mobile Mn species produced by the Mn reduction processes (e.g., aqueous Mn(II) and ligand complexed Mn(III)) could partly diffuse into the overlying waters and, together with the estuarine Mn loads carried by the surface waters, transfer large amounts of reactive Mn into open coastal areas and subsequently contribute to Mn shuttling and inter-linked biogeochemical processes over the seafloor. Given the widespread occurrence of acid sulfate soils and other sulfidic geological materials on many coastal plains worldwide, the identified Mn attenuation and transport mechanisms are relevant for many estuaries globally. [ABSTRACT FROM AUTHOR]

Acid sulfate soils are limiting the productivity of pineapples (Ananas comosus (L.) Merr. var. comosus) by lacking available P content. This study aims to evaluate the potency of P-solubilizing bacterial endophytes, Burkholderia silvatlantica L-VT09 and N-VT06, on acid sulfate soil properties and features of pineapples grown in that soil. The two-factor experiment was arranged according to a completely randomized block design. One factor was P fertilizer levels: 25% P, 50% P, 75% P, and 100% P; the other was supplementations of P-solubilizing bacterial endophytes: No supplementations, individual supplementation of L-VT09, individual supplementation of N-VT06, and mixed supplementation of both L-VT09 and NVT06. The result revealed that supplying the mixture of B. silvatlantica L-VT09 and N-VT06 did improve the soil fertility as increasing available P content and bacterial density (12.6 mg P kg-1 and 3.82 most probable number g-1 dry soil weight, respectively), P uptake (19.2 kg ha-1), growth as boosting plant height (8.30 cm), leaves number per plant (6.60 leaves plant-1), D-leaf length and width (2.80 and 0.32 cm, correspondingly), stem size (3.40 cm in length and 0.44 cm in diameter), yield components as enhancing fruit length and fruit diameter (3.50 and 1.46 cm, sequentially), yield (11.5 t ha-1), and pineapple fruit quality as ameliorating sugar content (1.71 °Brix) and water content (166.4 mL), in comparison with the no bacteria supplied case. Supplying the mixture of B. silvatlantica L-VT09 and N-VT06 altered 75% P but still maintained pineapple yield. [ABSTRACT FROM AUTHOR]

The study aimed to assess the variation of surface water quality in the Phu My Species-Habitat conservation area (conservation area) in 2019–2022. Fourteen water quality indicators including pH, electrical conductivity (EC), turbidity (Turb), salinity (Sal), total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), oxygen demand chemical (COD), ammonium NH4+-N), nitrate (NO3--N), orthophosphate (PO43--P), total phosphorus (TP), iron (Fe2+) and aluminum (Al3+) were analyzed. Correlation Pearson and cluster analysis (CA) were performed to find the correlation between surface water environmental parameters and locations with similar physical and chemical characteristics of water. The results showed that the surface water in the Phu My conservation area was acidic, with low pH and high concentrations of Fe2+and Al3+. The amounts of organic substances (except COD) and nutrients (NH4+-N, NO3--N, and PO43--P) in the study area were relatively low. Surface water quality is being well managed to develop key species in the Phu My Species-Habitat conservation area, Lepironia and Eleocharis species. The correlation analysis result indicates that organic matter and nutrients have a positive linear correlation, having the same origin formed from the degradation of organic matter from dying flora and fauna and agricultural activities in the study area. The CA analysis results show that the monitoring system was relatively suitable and could be applied in the future. [ABSTRACT FROM AUTHOR]

This study was conducted to (i) establish the diagnosis and recommendation integrated system (DRIS) for the macronutrient and micronutrient status of pineapple at the preflowering stage and (ii) verify the reliability of the established norms for macronutrients. We collected 86 pineapple leaves at sites +1 and +3 from 86 fields of pineapples grown in acid sulfate soil (ASS) and analyzed their nutrient content. Findings revealed the establishment of 12 and 20 nutrient ratios for DRIS norms at pineapple leaf sites +1 and +3. Based on omission fertilization of N, P, K, Ca, and Mg at the first crop, the DRIS index of N, P, K, and Mg was inadequate in treatments lacking the corresponding nutrients, whereas the DRIS index in the treatment fully fertilized with N, P, K, Ca, and Mg was negative and lower at the +3 leaf position. In the second crop, the DRIS norms were highly reliable via the negative DRIS index when fertilizing without N, P, K, Ca, and Mg. By contrast, when fertilizing with N, P, K, Ca, and Mg, the DRIS index was positive or less negative. The DRIS norms established that position +3 is robust and suitable for evaluating the pineapple macronutrient status. [ABSTRACT FROM AUTHOR]

Indonesia, soybean (Glycine max (L.) Merr.) is the second most important staple food with low production compared to the demand. This problem can be overcome by using marginal land such as acid sulfate soil of tidal swampland, however, the optimal application of fertilizer in such soil is minimal. Therefore, this study aims to examine the application of fertilizer in acid sulfate soil in South Kalimantan, Indonesia. It was conducted using a split-plot design with three replicates and the main plot was biofertilizer, which consisted of no-biofertilizer (P1); biofertilizer consortium of fungi, P-solubilizing bacteria, N-fixing bacteria (P2), and biofertilizer consortium of N-fixing bacteria symbiotic and nonsymbiotic, P-solubilizing bacteria and phytohormone-producing bacteria (P3). Meanwhile, the subplot was NPK fertilizer dosage, consisting of nofertilizer (A1), dose of 150% (A2), dose of 100% (A3), and dose of 50% (A4) of the recommendation. The results showed that the biofertilizer and NPK fertilization dose did not show an interaction with soil pH and Al3+. The highest N and K nutrient uptake was in P2 at 50% NPK fertilizer dosage, while P in P3 at 150% NPK fertilization dose. The highest soybean yields were obtained in the application of biofertilizer P3 with 150% NPK, i.e., 1.6 t ha-1, followed by the 1.5 t ha-1 in the application of P2 + 50% NPK. This showed that the use of P2 biofertilizer can reduce NPK fertilizer application to 50% in soybean plants in acid soil tidal lands. Furthermore, the application of biofertilizers can increase soybean productivity in acid sulfate soil in Indonesia. [ABSTRACT FROM AUTHOR]

Rhizosphere microbes are important for plant tolerance to various soil stresses. Rice is the most aluminum (Al)-tolerant small grain cereal crop species, but the link between rice Al tolerance and rhizosphere microbiota remains unclear. This study aimed to investigate the microbial community structure of aluminum-sensitive and Al-tolerant rice varieties in acid sulfate soil under liming and non-liming conditions. We analyzed the rice biomass and mineral element contents of rice plants as well as the chemical properties and microbial (archaea, bacteria, and fungi) communities of rhizosphere and bulk soil samples. The results showed that the Al-tolerant rice genotype grew better and was able to take up more phosphorus from the acid sulfate soil than the Al-sensitive genotype. Liming was the main factor altering the microbial diversity and community structure, followed by rhizosphere effects. In the absence of liming effects, the rice genotypes shifted the community structure of bacteria and fungi, which accounted for the observed variation in the rice biomass. The Al-tolerant rice genotype recruited specific bacterial and fungal taxa (Bacillus , Pseudomonas , Aspergillus , and Rhizopus) associated with phosphorus solubilization and plant growth promotion. The soil microbial co-occurrence network of the Al-tolerant rice genotype was more complex than that of the Al-sensitive rice genotype. In conclusion, the bacterial and fungal community in the rhizosphere has genotype-dependent effects on rice Al tolerance. Aluminum-tolerant rice genotypes recruit specific microbial taxa, especially phosphorus-solubilizing microorganisms, and are associated with complex microbial co-occurrence networks, which may enhance rice growth in acid sulfate soil. [ABSTRACT FROM AUTHOR]

This study explores the reuse of spent coffee-grounds (SCGs) and the use of dissolved humic acid (DHA) to remediate acid sulfate (AS) soil drainage using adsorption and precipitation experiments, with changing pH, weight/volume, and concentrations (mg/L of dissolved organic carbon). In addition, this study aims to extend the usability of the SCGs, after being reacted with AS soil drainage, by identifying the potential recovery of incinerated SCGs from the ash of the SCGs produced incineration. As compared to DHA, the SCGs had greater efficiency in removing metals, such as Al (98%), Ca (96%), Co (94%), Fe (88%), Mn (100%), Ni (93%), and Zn (96%). However, the removal of Fe was significantly reduced when higher weight/volume of SCGs were introduced. In addition, SCGs could not bind sulfur, while DHA had removed up to 25% of S from the solution. This suggests the simultaneous use of SCGs and DHA could restrict the formation of problematic Fe(III) secondary compounds (e.g., schwertmannite/akaganeite) which are problematic in some AS soil settings. The results show that Co (69%), Ni (58%), Mn (60%), Fe (59%), Zn (55%), and Al (34%) had the highest recovery percentage by sequential chemical extraction, respectively. The recovery of metals, as well as the removal of dissolved metals from the drainage water, illustrates the effectiveness of the proposed approach for SCGs reuse.

Rhizosphere microbes are important for plant tolerance to various soil stresses. Rice is the most aluminum (Al)-tolerant small grain cereal crop species, but the link between rice Al tolerance and rhizosphere microbiota remains unclear. This study aimed to investigate the microbial community structure of aluminum-sensitive and Al-tolerant rice varieties in acid sulfate soil under liming and non-liming conditions. We analyzed the rice biomass and mineral element contents of rice plants as well as the chemical properties and microbial (archaea, bacteria, and fungi) communities of rhizosphere and bulk soil samples. The results showed that the Al-tolerant rice genotype grew better and was able to take up more phosphorus from the acid sulfate soil than the Al-sensitive genotype. Liming was the main factor altering the microbial diversity and community structure, followed by rhizosphere effects. In the absence of liming effects, the rice genotypes shifted the community structure of bacteria and fungi, which accounted for the observed variation in the rice biomass. The Al-tolerant rice genotype recruited specific bacterial and fungal taxa (Bacillus, Pseudomonas, Aspergillus, and Rhizopus) associated with phosphorus solubilization and plant growth promotion. The soil microbial co-occurrence network of the Al-tolerant rice genotype was more complex than that of the Al-sensitive rice genotype. In conclusion, the bacterial and fungal community in the rhizosphere has genotype-dependent effects on rice Al tolerance. Aluminum-tolerant rice genotypes recruit specific microbial taxa, especially phosphorus-solubilizing microorganisms, and are associated with complex microbial co-occurrence networks, which may enhance rice growth in acid sulfate soil.

• Burkholderia tropica L-VT08c and Enterobacter cloacae N-VT01 improved soil properties. • B. tropica L-VT08c and E. cloacae N-VT01 increased pineapple growth and yield. • B. tropica L-VT08c and E. cloacae N-VT01 improved degree Brix and vitamin C content. • Mixture of B. tropica L-VT08c and E. cloacae N-VT01 replaced 50% of N fertilization. The study was proposed to assess the efficacy of endophytic nitrogen (N)-fixing bacterial strains of Burkholderia tropica L-VT08c and Enterobacter cloacae N-VT01 on ameliorating soil features, and characteristics of pineapples on the acid sulfate soil in Vi Thanh city, Hau Giang province, Vietnam. The experiment was conducted with two factors. Therein, the first factor was N fertilizer doses: 25% N, 50% N, 75% N and 100% N; the other one was supplementations of endophytic N-fixing bacteria: no application of bacteria, individual application of the L-VT08c strain, individual application of the N-VT01 strain and a combination of both strains. Supplying the mixture of B. tropica L-VT08c and E. cloacae N-VT01 did some improvements in soil properties, including concentrations of NH 4 +, NO 3 − and available phosphorus, and bacterial densities (7.30, 2.20 mg kg−1 and 12.3 mg P kg−1, and 4.01 MPN g−1 DSW), in N uptakes (52.1 kg ha−1), in growth as the plant height (6.80 cm), leaves number per plant (7.80 leaves plant−1), D-leaf size (4.90 long and 0.56 cm wide), and stem size (4.30 long and 0.32 cm wide), in productivity as the fruit size (2.20 long and 0.54 cm wide) and yield (3.70 t ha−1), and in fruit qualities as the degree Brix (0.80%) and vitamin C content (2.80 mg 100 g−1), in comparison with the no bacteria applied group. Supplying the bacteria mixture replaced 50% N as the standardized fertilization without reducing the pineapple yield. [Display omitted] [ABSTRACT FROM AUTHOR]

Study region: Halland county, located on the Swedish west coast, with a special focus on the area around Ramsjö canal (Falkenberg municipality). Study focus: This study contributes to the understanding of the development of active acid sulfate soils and environmental consequences of leaching from these soils in an area without previous investigations. Samples taken from different soil profiles in an agricultural area and water samples from the agricultural drainage system were analysed in pH, electrical conductivity, and metal concentrations. To evaluate the on-site situation, the results of the soils sample analysis were compared to the national soil classification system and the water samples to areas in northern Europe affected by acid sulfate soils. New hydrological insights for the region: The results prove the existence of active acid sulfate soils in a coastal area in Halland. In the study region, acid sulfate soils were discovered in an agricultural area of drained wetland and peatland. Water samples taken from the drainage system and a man-made canal flowing into Kattegat Sea have low pH combined with high electrical conductivity and increased metal concentrations. This is a direct consequence of intensive leaching from the discovered acid sulfate soils in that area. Therefore, this is the first case study proving the existence of acid sulfate soils and highlighting their environmental impact on surface water quality on the Swedish west coast (i.e. outside the Baltic Sea Basin).

The study assesses steel slag fertilizer’s effect on rice yield on acid sulfate soil in Vinh Phuoc village, Tri Ton district, An Giang province. A fi eld experiment with three treatments was established by the randomized block method with three replications. The fertilizer dose applied in individual treatments was: (1) 3 tons/ha lime, (2) 3 tons/ha steel slag fertilizer, and (3) 3 tons/ha compost in the experiment. The farmers’ practice fertilizer rate of 131 kg N + 41 kg P2 O5 + 108 kg K2 O/ha was applied as the based treatment. Using steel slag fertilizer on acid sulfate soil at a dosage of 3 tons/ha in combination with inorganic fertilizers showed a tendency to improve soil chemical properties such as soil pH, EC, soil organic carbon (SOM) content, CEC, total P, available P, and exchangeable cations (K, Na, Mg) content. The slag fertilizer affected the growth of rice plants, thereby helping to increase the yield and yield components of rice compared to other treatments. The steel slag fertilizer has improved soil properties and rice yield, which was statistically signifi cantly different from other treatments. However, total nitrogen and calcium exchange content have not improved considerably. Therefore, applying inorganic fertilizers combined with steel slag fertilizer is an appropriate solution to enhance soil nutrients and increase rice yield. [ABSTRACT FROM AUTHOR]

This paper provides new insights into the geochemical cycling of rare earth elements (REEs) in acid sulfate soils developed on salt marsh sediments of the Huelva estuary (Spain) as a result of sulfide mineral oxidation in abandoned ore stockpiles. The study was aimed at determining the REE abundance, fractionation pattern and mineralogical control of the dispersal and retention of REEs in the soil system. Forty-one samples were collected at 13 core sampling sites along two transects extending across the degraded marshland, and they were subjected to XRD, ESEM-EDS and ICP-MS analyses. Measurements revealed that the soil receiving acid discharges has relatively high concentrations of SREEs (174.77 ± 19.77 mg kg-1) compared to local baseline concentrations. Shale-normalized REE patterns are generally flat, but a slight middle REE (MREE) enrichment is consistently apparent in all soil samples, involving relatively low LaN/GdN ratios (0.83 ± 0.08) and GdN/LuN ratios up to 1.42. The convex-upward REE pattern supports the possibility that iron oxy-hydroxide minerals play an important role in MREE retention through adsorption and co-precipitation mechanisms. Efflorescent sulfate salts left on the topsoil by the evaporation of acid waters show a strong depletion of light REEs (LaN/GdN = 0.16 ± 0.10) and act as a temporary reservoir of labile MREEs and heavy REEs during dry periods. [ABSTRACT FROM AUTHOR]

For the first time, an industrial solid waste (CAS) was used for the rapid oxidation and neutralization of acidic sulfate soil. The waste mainly contained Fe-doped CaCO3 and CaAl-layered double hydroxide (LDH). After treatment, CAS neutralized the acidic soil with the aid of hydrogen peroxide. Compared with other oxidation-accelerating materials, including activated carbon, biochar, and Fe-doped biochar, CAS showed the best oxidation rate acceleration. When the ratio of CAS and sulfur in acidic soil was 1.5:1, the pH of the soil changed to 6.32 and the oxidation rate increased by 50%. The characterization results showed that the main products of CAS were CaMg oxides and Ca-Al LDH. The oxidation product (SO42−) was intercalated into the LDH interlayers. The accelerated oxidation mechanism of CAS was divided into the following stages: accelerated Fenton oxidation; LDH adsorption of oxidized SO42−; and neutralization of sulfuric acid by calcium carbonate. The main results of this work provide a high-value-added utilization method of solid waste for acidic soil remediation. [ABSTRACT FROM AUTHOR]

Acid sulfate land is a land resource that can be optimized to achieve soybean selfsufficiency. Management of irrigation systems and the use of biological fertilizers play an important role in efforts to increase yields. This research aimed to determine the effect of biological fertilizer application and water management systems on soybean yields on tidal swamp land of overflow type B. The research was carried out on potential acid sulphate land of overflow type B using a Split Plot Design with the main plot, namely water management, namely the system management with trenches 20 cm deep and without trenches and subplots is the use of biological fertilizer, namely, Rhizobium sp., Mycorrhiza, Rhizobium sp. specific for acid land, Rhizobium sp. + Mycorrhiza. Management of water level without channels and without the addition of biological fertilizer for cultivating soybean plants in the dry season on type B tidal land is effective in maintaining soil pH that can be tolerated by soybean plants. There was no interaction and no significant effect of regulating the water level with ditches and adding biological fertilizer on the productivity of soybean plants due to rising water levels.

In a boreal acidic sulfate-rich subsoil (pH 3-4) developing on sulfidic and organic-rich sediments over the past 70 years, extensive brownish-to-yellowish layers have formed on macropores. Our data reveal that these layers ("macropore surfaces") are strongly enriched in 1 M HCl-extractable reactive iron (2-7% dry weight), largely bound to schwertmannite and 2-line ferrihydrite. These reactive iron phases trap large pools of labile organic matter (OM) and HCl-extractable phosphorus, possibly derived from the cultivated layer. Within soil aggregates, the OM is of a different nature from that on the macropore surfaces but similar to that in the underlying sulfidic sediments (C-horizon). This provides evidence that the sedimentary OM in the bulk subsoil has been largely preserved without significant decomposition and/or fractionation, likely due to physiochemical stabilization by the reactive iron phases that also existed abundantly within the aggregates. These findings not only highlight the important yet underappreciated roles of iron oxyhydroxysulfates in OM/nutrient storage and distribution in acidic sulfate-rich and other similar environments but also suggest that boreal acidic sulfate-rich subsoils and other similar soil systems (existing widely on coastal plains worldwide and being increasingly formed in thawing permafrost) may act as global sinks for OM and nutrients in the short run.

Besides causing acidification, acid sulfate (AS) soils contain large nitrogen (N) stocks and are a potential source of N loading to waters and nitrous oxide (N2O) emissions. We quantified the stocks and flows of N, including crop yields, N leaching, and N2O emissions, in a cultivated AS soil in western Finland. We also investigated whether controlled drainage (CD) and sub-irrigation (CDI) to keep the sulfidic horizons inundated can alleviate N losses. Total N stock at 0–100 cm (19.5 Mg ha−1) was smaller than at 100–200 cm (26.6 Mg ha−1), and the mineral N stock was largest below 170 cm. Annual N leaching (31–91 kg N ha−1) plus N in harvested grain (74–122 kg N ha−1) was 148% (range 118–189%) of N applied in fertilizers (90–125 kg N ha−1) in 2011–2017, suggesting substantial N supply from soil reserves. Annual emissions of N2O measured during 2 years were 8–28 kg N ha−1. The most probable reasons for high N2O emission rates in AS soils are concomitant large mineral N pools with fluctuating redox conditions and low pH in the oxidized subsoil, all favoring formation of N2O in nitrification and denitrification. Although the groundwater level was higher in CD and CDI than in conventional drainage, N load and crop offtake did not differ between the drainage methods, but there were differences in emissions. Nitrogen flows to the atmosphere and drainage water were clearly larger than those in non-AS mineral soils indicating that AS soils are potential hotspots of environmental impacts. [ABSTRACT FROM AUTHOR]

Purpose: Acid soils often have low P availability limiting plant growth, which is addressed by application of inorganic fertilizers and neutralizing agents. However, little is known about the effect of addition of inorganic P and neutralizing agents on P pools in acid sulfate soils under submerged or moist conditions. Materials and methods: Sulfuric acid sulfate soil (pH < 4) was amended with two neutralizing agents (NaOH or Ca(OH)2) to achieve soil pH 4 or 5.5, without or with addition of inorganic P equivalent to 20 kg ha−1. Soils were incubated at 25 °C in either submerged or moist conditions (100% of maximum water holding capacity). After 2 weeks, soil P pools (labile P, moderately labile P, non-labile P and residual P) and Fe and Al oxides were determined. Results and discussion: Adjustment of pH had little effect on the measured parameters. Labile, moderately labile and non-labile P pools were higher with P addition than without P addition. With P addition, labile and non-labile P pools were up to twofold higher in submerged incubation than in moist incubation. Labile P, non-labile P and residual P represented 70%, 15% and 15% in submerged incubation and 40%, 40% and 30% in moist incubation, respectively. In submerged incubation, Fe oxides were higher in soils amended with neutralizing agents than in the original soil which can be explained by the higher pH. Conclusions: A high proportion of added P was available after 2 weeks of application particularly in submerged incubation. The pH increase had little effect on P availability. [ABSTRACT FROM AUTHOR]

Southern Vietnam is known as one of the most vulnerable areas to climate change in the world due to its low elevation and flat topography, heavy groundwater use, and dense population. This paper introduces hydrogeological conditions and critically reviews groundwater issues that southern Vietnam faces by summarizing previous literatures. Issues that this paper covers include groundwater use and associated phenomenon, acid sulfate soils, the occurrence of saline groundwaters, seawater intrusion, land subsidence, groundwater acidification, and groundwater contamination by nitrate, ammonium, and trace metals such as As, Fe, Mn, Al, Cd, and Pb. This paper shows that most of these issues are inter-related and essentially linked with the unique hydrogeological setting of the study area. However, many of these problems have also been triggered or aggravated by human activities that use water resources and land. Issues such as those of As contamination and groundwater acidification are connected with the aquifer characteristics that are generally confined and rich in organics and pyrite. However, groundwater salinization, acidification, groundwater level declining, land subsidence, and high heavy metal concentrations are in large part caused by human activities such as well installation and heavy groundwater abstraction. While previous studies have proposed artificial recharge as a promising means of mitigating groundwater issues in the study area, the development of techniques that help minimizing aquifer disturbances is also likely required. [ABSTRACT FROM AUTHOR]

Over 24 million hectares of the world's coastal floodplains are underlain by acid sulfate soils (ASS). Drainage of these sediments has led to widespread environmental degradation, raising serious health concerns. To date, onsite rehabilitation has been complicated by differing stakeholder priorities, with resources often allocated to sites with more vocal proponents rather than those exposed to more significant environmental impacts. To address this issue, this paper introduces the Coastal Floodplain Prioritisation (CFP) Method ; a novel, data driven and spatially explicit multi-criteria assessment that ranks floodplain catchment areas according to their risk of transferring acidic drainage waters to an estuary. Results can be used to prioritise where remediation actions are likely to have the greatest benefit. The method was applied across six different estuaries in south-east Australia, with major field campaigns undertaken at each site. Within each estuary, the largest acid fluxes and impacts are identified with relevant mitigation measures provided. On a catchment scale, the results reflect the broader hydrogeomorphic characteristics of each estuary, including the historic acid formation conditions and recent anthropogenic drainage activities. Low-lying backswamps were identified as the highest risk zones within each estuary. These areas are also the most vulnerable to sea level rise. Reinstatement of tidal inundation to these backswamps effectively remediates acid sulfate soil discharges and provides a nature-based solution for adaptation to sea level rise with a range of co-benefits to encourage further investment. [Display omitted] • A novel method to objectively rank estuarine catchments by acid sulfate soil risk. • Mechanisms that generate, mobilise and transfer acid drainage waters are quantified. • High risk areas present distinct hydrogeomorphic characteristics. • Critical risk factors help identify preferred remediation strategies. • Tidal restoration has co-benefits for ecosystem resilience and climate adaptation. [ABSTRACT FROM AUTHOR]

This paper provides new insights into the geochemical cycling of rare earth elements (REEs) in acid sulfate soils developed on salt marsh sediments of the Huelva estuary (Spain) as a result of sulfide mineral oxidation in abandoned ore stockpiles. The study was aimed at determining the REE abundance, fractionation pattern and mineralogical control of the dispersal and retention of REEs in the soil system. Forty-one samples were collected at 13 core sampling sites along two transects extending across the degraded marshland, and they were subjected to XRD, ESEM-EDS and ICP-MS analyses. Measurements revealed that the soil receiving acid discharges has relatively high concentrations of ΣREEs (174.77 ± 19.77 mg kg−1) compared to local baseline concentrations. Shale-normalized REE patterns are generally flat, but a slight middle REE (MREE) enrichment is consistently apparent in all soil samples, involving relatively low LaN/GdN ratios (0.83 ± 0.08) and GdN/LuN ratios up to 1.42. The convex-upward REE pattern supports the possibility that iron oxy-hydroxide minerals play an important role in MREE retention through adsorption and co-precipitation mechanisms. Efflorescent sulfate salts left on the topsoil by the evaporation of acid waters show a strong depletion of light REEs (LaN/GdN = 0.16 ± 0.10) and act as a temporary reservoir of labile MREEs and heavy REEs during dry periods.

This study evaluated metal concentrations in Caulerpa spp. cultured in ‘traditional’ coastal ponds in South Sulawesi and consumed locally as food. Although Caulerpa spp. are a rich source of supplemental dietary nutrients, like many macroalgal species they are also capable of bioaccumulating potentially toxic metals. We measured the metal concentrations of Caulerpa spp. from several locations in South Sulawesi to determine (1) whether cultivated Caulerpa spp. posed a potential risk to consumers, (2) whether Caulerpa spp. from cultivated ponds had different metal content that varied between localities and (3) whether there was any evidence for increased concentrations of heavy metals in Caulerpa spp. cultivated in ponds with known acid sulfate soils (ASS). Of the metals studied only As (0.7 mg kg−1) and Pb (0.35 mg kg−1) were recorded at concentrations approaching the national food safety (BSN) limits of Indonesia (1.0 and 0.5 mg kg−1 respectively). Locality differences were observed between samples that could be explained by the background geography of sites. There was some indication that ASS conditions could lead to elevated levels of heavy metals. Consequently, we propose that the potential acidity of pond soil is considered when cultivating Caulerpa.

Saturated acid sulfate soils with hypersulfidic material are productive wetland soils, but when they dry, they generate large amounts of sulfuric acid due to oxidation of pyrite to form sulfuric material (pH <4) and consequently sulfuric soils. After re-saturation of sulfuric soils and thus the re-establishment of reduced conditions, activity of sulfate reducing bacteria (SRB) can lead to a renewed formation of Fe sulfides and pH increase. Many SRB are heterotrophic and require sufficient available organic matter; however, little is known about OC consumption and changes of the composition of organic substrates during the amelioration process. To investigate remediation of a sandy, OC-poor sulfuric soil (initial pH = 2.5), short-term anoxic incubation experiments over a period of approx. 10 weeks were conducted after re-submerging under controlled laboratory conditions. We tested different organic matter quantities between 10% up to 200% of the native soil OC content. Besides wheat straw, we used lactate additions to test if this selectively promotes the activity of SRB, and thus, accelerates sulfate reduction and pH neutralization. The results showed that OC additions of ≥50% of native soil OC content and pre-adjustment of pH to values ≥5.0 were necessary to subsequently enable microbial reduction reactions to occur, which increased the pH to values ≥5.5. OC additions of ≥100% instead of 50% of native soil OC as wheat straw led to quicker changes of redox and pH values, to slightly higher microbial activity as indicated by CO 2 release, and to higher proportions of newly-formed mineral-associated OC. The addition of OC as lactate solution to promote specifically SRB was only successful in combination with wheat straw addition. Here, the presence of lactate led to the quickest changes of pH and redox values and resulted in pH ≥7 and redox values ≤ −300 mV due to an active microbial population. Our results indicate that a diverse microbial community is more important for successful remediation than a selective promotion of SRB. • Wheat straw-lactate mixtures promote pH increase of re-saturated sulfuric soil • Lactate addition alone is less effective than wheat straw-lactate additions • Lactate addition does not promote the abundance of sulfate reducing bacteria • Organo-mineral associations form after straw addition on anoxic conditions [ABSTRACT FROM AUTHOR]

Production of acid mine drainage (AMD) and acid sulfate soils is one of the most concerning environmental consequences associated with mining activities. Implementation of appropriate post-mining AMD management practices is very important to minimize environmental impacts such as high soil acidity, soil erosion, and metal leachability. The objective of this study was to develop a cost-effective and environment-friendly "green" technology for the treatment of AMD-impacted soils. This study utilized the metal-binding and acid-neutralizing capacity of an industrial by-product, namely drinking water treatment residuals (WTRs), and the extensive root system of a metal hyper-accumulating, fast-growing, non-invasive, high-biomass perennial grass, vetiver (Chrysopogon zizanioides L.) to prevent soil erosion. Aluminum (Al)-based and calcium (Ca)-based WTRs were used to treat AMD-impacted soil collected from the Tab-Simco coal mine in Carbondale, IL. Tab-Simco is an abandoned coal mine, with very acidic soil containing a number of metals and metalloids such as Fe, Ni, Zn, Pb, and As at high concentrations. A 4-month-long greenhouse column study was performed using 5% and 10% w/w WTR application rates. Vetiver grass was grown on the soil-WTR mixed media. Turbidity and total suspended solid (TSS) analysis of leachates showed that soil erosion decreased in the soil-WTR-vetiver treatments. Difference in pH of leachate samples collected from control (3.06) and treatment (6.71) columns at day 120 indicated acidity removal potential of this technology. A scaled-up simulated field study was performed using 5% WTR application rate and vetiver. Soil pH increased from 2.69 to 7.2, and soil erosion indicators such as turbidity (99%) and TSS (95%) in leachates were significantly reduced. Results from the study showed that this "green" reclamation technique has the potential to effectively treat AMD-impacted soils. [ABSTRACT FROM AUTHOR]

Abstract Acidic groundwaters enriched with heavy metals are frequently observed in the coastal plain aquifers. The acidic pHs are observed even in the deep confined aquifers in southern Vietnam. This study geochemically explores the causes of these acidic groundwaters by investigating 41 groundwater samples, 4 soil samples and a 54 m long sediment core and the long-term monitoring data (4189 observations) obtained from 178 wells of the National Groundwater Monitoring Network for the South of Vietnam (NGMNS). The groundwater data show elevated Fe, Mn, Al, Pb, and Zn concentrations as the pH becomes acidic and suggest pyrite oxidation be the major cause for the groundwater acidification. This is further confirmed by pyrite framboids observed in the sediment or soil samples taken from the sites where strongly acidic groundwaters were observed. Results of leaching experiments using sediment and soil samples indicate that high metal concentrations in the acidic pH are associated with the increased metal solubility and mineral dissolution kinetics. The acidification of deep groundwaters is revealed to be associated with well installation, indicating the importance of proper well-installation techniques to protect water quality of deep confined aquifers. Graphical abstract Unlabelled Image Highlights • Metal-rich, acidic groundwaters are commonly observed in Mekong Delta area. • Pyrite oxidation is the major reason for groundwater acidification in the area. • The pyrite oxidation in deep confined aquifer was induced by well installation. • Well installation techniques minimizing aquifer disturbance are required. [ABSTRACT FROM AUTHOR]

Acid sulfate soils can form when pyrite-rich marshes are drained or tidal influence decreases, naturally or anthropogenically. Often they are vegetated by mangroves, serve as important aquatic bird habitats, and harbor unique microbial biodiversity. They limit coastal development potential. The current best map of Australian acid sulfate soils is based on expert interpretation of soil surveys, most at 1:100,000 scale. In the current study, we attempted the first predictive spatial modeling to map acid sulfate soils and soil sulfur concentration on a 90-m grid. We use 34 national environmental 90-m grids and 614 observations on the presence/absence of acid sulfate soils to train a machine learning algorithm, random forests, to predict the location of acid sulfate soils across three regions of Northern Australia. We use the same environmental data and 1315 measurements of total elemental sulfur at 60-80 cm depth across Australia to train another random forest model to predict the spatial pattern of sulfur concentrations in the three regions. The model for acid sulfate soils is better than that for sulfur but both related maps showed that high sulfur concentrations generally coincide with the predicted presence of acid sulfate soils. This coincidence between the predicted occurrence of acid sulfate soils and sulfur concentrations confirms the modeling approach presented here was reliable and could be applied to map acid sulfate soils at high resolution globally. [ABSTRACT FROM AUTHOR]

[Display omitted] • A long-term development of oxidation of sulfides in an AS soil field was simulated. • CEC had an important role in reproducing the soil pH profile observed in the field. • The simulated oxidation of mackinawite was three times faster than that of pyrite. Land drainage lowers the soil water table, which triggers enhanced oxidation of iron sulfide minerals in acid sulfate soils, causing acidification of fields and posing environmental hazards to aquatic ecosystems. The objective of this study was to develop a model for investigating the effects of oxidation of iron sulfide minerals and the cation exchange capacity (CEC) on the long-term evolution of pH, redox potential and solute concentrations in soil water and drain discharge. Two electron acceptors (oxygen and ferric iron) were included in the model. The model was implemented in the HP1 modeling platform (coupled HYDRUS-1D and PHREEQC-3) and applied to an acid sulfate soil profile of an agricultural field in Finland. The geochemical part of the model was tested against field observations. A comparison of different model versions showed that CEC had an essential role in mimicking the observed pH profile of soil. The drain discharge water quality was similar in the model versions both with and without CEC, but the buffering effect of CEC could be seen as lower iron concentrations. The oxidation of metastable iron sulfide minerals was three times faster than the oxidation of pyrite. Descriptions for the oxidation of both two minerals and for CEC were required to conduct long-term simulations that reproduce the observed geochemical state of a drained agricultural field. The HP1 modeling platform facilitated the testing of alternative chemical transformation processes of an AS soil profile in response to increased drainage efficiency after subsurface drainage installation. [ABSTRACT FROM AUTHOR]

Thionic Fluvisols soil in Southern Vietnam is like typical acid sulfate soil in the tropics and is severely polluted due to human activities. Salinity intrusion and industrial wastewater contamination are the main cause of environmental degradation in soil ecosystem. This research was aimed to determine a link between biochemical soil properties and land use types to provide suitable solutions for afforestation and soil restoration. Soil sampling was conducted in five different land use types at four soil layers (O, AB, Bj and Cp). The five land use types were sugarcane crop; Melaleuca plantation; 2-year Acacia plantation; 5-year Acacia plantation; and control (grass-covered land). The results showed that soil in those five land use types were very acidic (pH ≤ 4) having poor-nutrient condition with  range of  orthophosphate  content of 378 - 640 mg/kg, N-NH4  of 586 - 999 mg/kg and N-NO3 of 830 - 1,112 mg/kg. Concentration of toxic ions was very high with large variation among land use types and soil depths i.e. 1,799 – 12,403 mg SO42-/kg; 22 - 1,645 mg exchangeable Fe/kg and 34 - 88 mg Al3+/kg soil. The lowest concentration of exchangeable Fe3+ and SO42- ions were found in sugarcane and Melaleuca plantations, respectively. Twenty-three sulfur-oxidizing bacteria and two iron-oxidizing bacteria were identified. All these bacteria were initially identified as Thiobacillus sp. Sugarcane and Melaleuca plantations exhibited the most diverse Thiobacillus species which linked to reduction of exchangeable Fe and SO42- concentrations in these two land use types. This study indicated that Thiobacillus sp. could grow well in the Thionic Fluvisols. It is proposed that Melaleuca and sugarcane species could reduce iron and sulfur contents in Thionic Fluvisols in the tropics.

Land disposal of dredged sulfide-rich coastal sediments generates secondary coastal acid sulfate soils (CASS), as previously reduced sulfide minerals oxidise to produce acidic drainage rich in Fe, SO 4 2− and rare-earth elements (REEs). Few studies investigate both the source and the sink of REEs in the context of interpreting their mobilisation and potential use in tracing anthropogenic activity. Here we investigate REE signatures in estuarine sediments (and overlying surface waters) that have received acute, long-term (>15 years) acidic drainage from legacy sulfuric dredge spoils. It was found that the dredge spoil continues to act as a source of acidity (pH 3.5–5.5), Fe and REEs during development of CASS, and contains negligible acid volatile sulfide (AVS, a proxy for FeS) and relatively low concentrations of ΣREE (mean 44.5 mg/kg, range 4.1–362 mg/kg). In the receiving sediments, high AVS concentrations (mean 92.2 μmol/g, range 0.38–278 μmol/g) reflect elevated FeS content, likely due to high inputs of Fe and SO 4 2− from the acidic drainage, and correspond with a high concentration of total S (mean 852 μmol/g, range 105–2209 μmol/g) and an accumulation of ΣREE (mean 670 mg/kg, range 19.9–1819 mg/kg). Importantly, where drain sediments that were previously enriched in highly reactive sulfidic minerals and trace elements and have become exposed to the atmosphere (e.g. Site 3) and partially oxidised, they provide a further source of acidification, remobilising the REEs to the downstream sediments. Interestingly, we also found a clear positive correlation between phosphorous and REEs both in the dredge spoil and sediment, suggesting phosphate minerals may act as a sink for REEs in CASS influenced drain sediments. This is further supported by strong positive gadolinium anomalies (1.1–1.6) and high calculated anthropogenic Gd values (12–38%), which may reflect the influence of phosphate fertiliser on this eutrophic system. [ABSTRACT FROM AUTHOR]