Acid Sulfate Soils Research Articles

Classification of acid sulfate soils and soil materials in Finland and Sweden: Re-introduction of para-acid sulfate soils

Established international soil classification systems have not properly accommodated acid sulfate soils (ASS) and soil materials in Finland and Sweden because: (1) in these soils some diagnostic ASS properties are too deep to meet the depth requirements, and (2) there is a lack of defined diagnostic soil classification criteria for acidic and potentially acidic soil materials that do not completely fulfill the diagnostic pH-criterion of pH < 4.0. In this paper, two new ASS materials are introduced with the prefix “para” for parasulfuric material (oxidized material) and parahypersulfidic material (reduced material). These materials have diagnostic pH-criteria of pH 4.0–4.5 and 3.0–3.5 (field-pH for parasulfuric material and incubation-pH for parahypersulfidic material) for mineral and organic soil materials (here defined as > 20% organic matter; peat and gyttja), respectively. The term “para-acid sulfate soil (para-ASS) material” is introduced for soil materials which may have a considerable environmental impact due to mobilization of acidity and dissolved metals. Because organic acids may lower pH to values below the established pH-value of < 4.0 for ASS materials, a pH of < 3.0 is used in the Finnish-Swedish ASS classification for organic soil materials. These changes and new additions to existing diagnostic ASS materials have consequently also led to a slight modification of the required field-pH values of the existing terms “hypersulfidic material” and “sulfuric material”. The Finnish-Swedish ASS classification further includes a systematic way for classification of the entire soil profile and no depth requirements for diagnostic ASS materials are present; what matters is the current or potential environmental impact that the soil has or may have. It is proposed that the Finnish-Swedish ASS classification may serve as a framework for establishing a unified ASS classification globally and that the new diagnostic ASS materials are included in relevant international soil classification systems.

Fluoride and acid enrichment in coal fire sponges in the Wuda coalfield, Inner Mongolia, Northern China

Coal fire sponges (CFSs) are a type of sponge-like contaminated soil bulge common in coal fire areas. However, the impacts of CFSs on the local environment are not yet understood. Thus, this study investigated soil samples from CFSs in the Wuda coalfield, Inner Mongolia, China, focusing on the acidity, sulfate, and fluorine content. The results showed that the CFSs were highly acidic, with an average pH of 0.76, and contained high levels of SO42− (257.29 × 103 μg/g), total fluorine (TF, 2011.6 μg/g), and water-soluble fluorine (WF, 118.94 μg/g), significantly exceeding those in the regional background soil and indicating that CFSs are a point source of heavy pollution. Soils in the 8000 m2 reclamation zone showed elevated acidity and high SO42− (129.6 × 103 μg/g), TF (1237.8 μg/g), and WF (43.05 μg/g) levels, which was likely the result of the weathering and dissemination of CFS. The CFS samples were rich in hydrogen fluoride, releasing 202.05 ppb of it when heated to 40 °C. Correlation analysis indicated that the acid sulfate soils in CFSs are likely caused by HSO4−/SO42−. Time-of-flight secondary ion mass spectrometry detected four characteristic ions (F−, H3O+, H2SO4+, and HSO4−) in all micro-domains of each sample, indicating that ionic fluorine compounds and sulfuric acid hydrate were found in the CFS samples. Sulfate minerals detected in CFSs included CaSO4, Fe2(SO4)3, CdSO4, NH4HSO4, and Na2SO4. Thus, the results identified CFSs as a transmission channel for contamination, with erosional surface soils as the carrier, for the first time. CFSs pose a serious threat of contamination, albeit over limited areas.

Soil taxonomical classification and organic carbon sequestration potential of coastal acid sulfate soils: Kari and Kayal ecosystems of Kerala, India

Soil taxonomical classification and organic carbon sequestration potential of coastal acid sulfate soils: Kari and Kayal ecosystems of Kerala, India

Hybrid pathways of denitrification drive N2O but not N2 emissions from an acid-sulphate sugarcane soil

AbstractAcid-sulphate sugarcane soils in the subtropics are known hot-spots for nitrous oxide (N2O) emissions, yet the reduction of reactive N2O to non-reactive dinitrogen (N2) via specific pathways remains a major uncertainty for nitrogen (N) cycling and loss from these soils. This study investigated the magnitude and the N2O:N2 partitioning of N2O and N2 losses from a subtropical acid-sulphate soil under sugarcane production using the 15N gas flux method, establishing the contribution of hybrid (co- and chemo-denitrification) and heterotrophic denitrification to N2O and N2 losses. Soils were fertilised with potassium nitrate, equivalent to 25 and 50 kg N ha−1, watered close to saturation then incubated over 30 days. An innovative, fully automated incubation system coupled to an isotope-ratio mass-spectrometer enabled real time analysis of 15N2O and 15N2 at sub-diel resolution. Peak losses of N2O and N2 reached 6.5 kg N ha−1 day−1, totalling > 50 kg of N2O+N2-N ha−1. Emissions were dominated by N2, accounting for more than 57% of N2O+N2 losses, demonstrating that the reduction of N2O to N2 proceeded even under highly acidic conditions. Over 40% of N2O, but only 2% of N2 emissions, were produced via hybrid pathways. These findings demonstrate hybrid pathways are generally limited to N2O production, likely driven by high organic matter content and low soil pH, promoting both biotic, and abiotic nitrosation. Regardless of the underlying process, the magnitude of the N2O emissions demonstrates the environmental, but also the potential agronomic significance, of hybrid pathways of N2O formation for N loss from fertilised acid-sulphate soils.

Effects of Organic Substrate Amendments on Selected Organic Fractions and Biochemical Parameters under Different Soils.

The application of organic substrates can affect soil respiration, dehydrogenase (DH-ase) activity, dissolved organic carbon (DOC), and humic acid (HA) fractions. This study aimed to evaluate the effects of five organic substrates in the organic fractions of degraded alluvial soil, acid sulfate soil, and sandy soils and the physicochemical properties of the soil. Soil samples were amended at a rate of 5 tons ha-1 with (1) water hyacinth compost, (2) sugarcane filter cake compost, (3) biogas sludge-rice straw compost, (4) vermicompost, and (5) sludge. The results showed that soil respiration and DH-ase activity increased rapidly within the first 5 days of incubation, while the concentrations of DOC and HA decreased throughout the incubation period. The highest respiration and DH-ase activity occurred after the application of vermicompost. DOC was found to be the highest in soils amended with sugarcane. The highest concentration of HA was observed with the application of sugarcane residues, regardless of the type of soil. The application of water hyacinth and biogas sludge stimulated cumulative HA only in the acid sulfate soil, while vermicompost improved HA only in the degraded soil. The largest stimulation in respiration and DH-ase activity was observed in degraded and sandy soils, regardless of the type of amendment. In the acid sulfate soil (3.7 mg·C·g-1), larger amounts of DOC and HA were observed than in both degraded (1.7 mg·C·g-1) and sandy soils (1 mg·C·g-1). However, DH-ase activity was the lowest in acid sulfate soil.

Regional variation in Swedish acid sulfate soil microbial communities is influenced by temperature and geochemistry

AbstractAcid sulfate soils are frequently described as the nastiest soils on Earth, and they pose environmental risks associated with their strong acidity and consequential mobilization of toxic metals present in the soils. Within Sweden, acid sulfate soils have been extensively studied around the northern Baltic coastline and have now been found to occur throughout the area below the maximum Holocene marine limit that stretches for some 2000 km from North to South. This study investigated 20 active acid sulfate soils (field tested pH < 4.0) collected throughout this area that were tested for microbial community composition using 16S rRNA gene amplicons, representing a novel study of microbial communities in ripening zones across a broad regional scale. The microbial community compositions exhibited a north (boreal zone) to south (hemiboreal zone) regional divide, primarily within the oxidized zone (pH < 4.0), to a lesser degree in the transition zone (steep pH gradient), while little differences were observed in the reduced zone (near‐neutral pH). For instance, a higher relative abundance of Ktedonobacteraceae was identified in the northern boreal and Gallionellaceae in the southern hemiboreal oxidized zones. In addition, microbial taxa associated with iron and sulfur oxidation and reduction were identified, such as Acidobacteriaceae, Gallionellaceae and Koribacteraceae that have been previously identified in other acid sulfate soils and acid mine drainage settings. The predominant controls of the microbial community differences were the north–south divide indicative of a strong soil‐temperature effect followed by soil zones suggesting an influence of the soils' pH and/or redox conditions.

The dynamic of pH and EC in the Katingan tidal irrigation system, under influences of acid water, brackish water, and tidal movement

The Katingan tidal irrigation area frequently experiences high salinity due to its coastal position and acidity due to the acid sulphate soil type and water discharge from the neighboring peat forests. This study aims to investigate the dynamic of pH and Electrical Conductivity (EC) caused by the interaction of peat water and brackish water, which is impacted by tides in an acid sulphate soil environment. Field measurements were conducted to collect data on water level, pH, and EC in both channels and fields. The dynamic of acid water from peat forests and acid sulphate soils with brackish water in the irrigation network was investigated using HEC-RAS simulations. The simulation incorporates water level, EC, and pH recorded at the Katingan River from December 22, 2022, to January 5, 2023. The results of simulations are calibrated with observed data at the main channel. The influence of brackish water on increasing pH and EC (pH = 5–7, EC = 0∼5.94 dS/m) is more significant in hydrotopography Type A, but it is less significant (pH = 4∼5.5, EC = 0∼2.25 dS/m) in hydrotopography Type B, which is less affected by brackish water. The water pH is more acidic in hydrotopography Type C, which is not impacted by tides. These simulation results may serve as a foundation for developing and operating sluice gates to improve water quality by allowing or preventing the entry of water into the irrigation network.

Humate-Silica as an ameliorant to decrease Fe toxicity and increase rice yields on acid sulfate soils

Iron toxicity is a major problem in increasing rice production in acid-sulfate soils. Humate materials and Silica ions can interact with Fe ions to form chelates so that they can decrease Fe toxicity and increase rice yields. This research aimed to study the effect of humate-silica soil on decreasing Fe toxicity and increasing rice yields in acid-sulfate soils. The research employed a simple randomized block design incorporating treatments F0=100% lime, F1=30% humate manufacturer+30% rice husk ash+40% lime, F2=30% water hyacinth humate+30% rice husk ash+40% lime, F3=30% water hyacinth humate+30% rice husk biochar + 40% lime, F4=30% humate manufacturer+30% rice husk biochar+40% lime, and control=without ameliorant. Each treatment was repeated 4 times. Observations of soil characteristics were carried out at the end vegetative stage including pH and Fe, while at the end of the research, observed including panicle length, 100g weight, and grain weight per pot. The findings indicated that F1 was able to increase pH and decrease Fe2+ concentration and wasn’t significantly different from F3. Ameliorant F3 was able to decrease Fe toxicity and increase rice yields. The application of this formula resulted in a decrease in the usage of agricultural lime while enhancing rice productivity in tidal soil.

The Leaching Process of Acid Sulphate Soil by One-and Two-Way Flow Systems in the Katingan Swamp Irrigation Area

The Katingan Swamp Irrigation Area, established in 1980, has an important role in supporting food security in Indonesia. It needs to be reclaimed to increase agricultural production, especially for leaching acid sulphate soil. The swamp irrigation area was expanded and rehabilitated so that the two-way flow became a one-way flow system to support the leaching process. This study aims to assess the discharge and water quality alterations in the Katingan main channel after the change of flow system. The aim is achieved by comparing the outcomes obtained from one-way and two-way flow simulations. The simulation used a mathematical model based on water level, water quality, and land topography data collected in the field. According to the findings, the two-way system demonstrates that fresh water from the river has not been able to improve water quality (pH) at the end of the primary channel, thereby leading to extreme acidity in those regions. Meanwhile, a one-way flow facilitates efficient circulation and delivers fresh water to the farthest service regions. Effective water circulation is important to enhance water quality in agricultural areas that have recently expanded. The current study focuses on mid-irrigation. Future research may cover the entire irrigation network for in-depth analysis.

Identifying Issues in the Katingan I Swamp Irrigation Area Through Field Survey and Monitoring Approaches

The Katingan irrigation area is a swamp area that has undergone agricultural development. The optimization of yields necessitates the adaptation of management strategies in response to the challenges encountered within the swamp irrigation area. The objective of this study is to discern the issues in the Katingan I swamp irrigation area by conducting field surveys and monitoring. The field survey was conducted from December 2022 to March 2023. The primary data collected are water level, quality, agricultural products, and field documentation. Secondary data such as rainfall, irrigation network schemes, and institutions were also acquired. The survey result found water acidity issues due to water coming from peat forests and acid sulphate soils. The acidity of the water rises during low tide and when rain carries acidic water. There is a problem with high salinity, particularly during high tide in dry seasons. Optimal water management is achievable through continuous monitoring of water level and quality. Another issue is a lack of human resources to cultivate the land, especially because the irrigation service area has recently been expanded. The results of this study hopefully provide valuable insights for developing future management strategies in Katingan.

Effect of lime application on phosphorus adsorption and desorption in post-active acid sulfate soil, Thailand

The application of lime is the general method of improving acid sulfate soils. However, if a lot of lime is applied, it can reduce the bioavailability of nutrients in the soil, especially phosphorus. The objective of this study was to investigate the effects of liming at different rates on the availability, adsorption, and desorption of phosphorus in two post-active acid sulfate soils (Ay and Se). The experiment was performed in the laboratory. The experiment was laid out in a completely randomized design (CRD) with four treatments and three replicates, i.e., the application of lime at a rate of 0 (control), 0.5, 1.0, and 2.0 times the lime requirement (LR). The lime requirements of the soils in the Ay and Se were 5,690 and 12,250 kg CaCO3/ha, respectively. The finding revealed that increasing the amount of lime could increase soil pH, available phosphorus, and the phosphorus activation coefficient. Application of lime at a dosage of 1.0-2.0 LR resulted in the highest phosphorus adsorption maximum (Qm) (380 mg/kg), while 0.5 LR resulted in the lowest Qm (353 mg/kg) in Se soil only. As lime dosage increased, phosphorus desorption maximum (Dm) and phosphorus desorption ratio (Dr) increased, with 2.0 LR yielding the highest values (124 mg/kg and 23.6 percent for Ay soil, and 77.3 mg/kg and 20.3 percent for Se soil, respectively). The results suggested that applying lime according to the lime requirement test, especially 2.0 LR, is the best option to promote the release of phosphorus in post-active acid sulfate soils.

Effect of brackish water inundation on temperate coastal acid sulfate soils under different vegetation types

AbstractCoastal 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.

The effect of biochar from plant materials on agricultural acid sulfate soil: a laboratory incubation

The effect of biochar from plant materials on agricultural acid sulfate soil: a laboratory incubation

Applying industrial side streams in the neutralization of acid generating sulfide-rich sediments – The impact on pH and leaching of harmful elements

Acid sulfate soils can cause severe environmental harm due to a low pH and mobilization of harmful elements. Acid sulfate soil material is formed when oxidation of sulfide minerals causes a drop in pH to <4.0 for mineral oil materials and <3.0 for organic soil materials or when the soil materials contain enough sulfide to potentially do so.Two dredged, acid sulfate soil materials from Finland were used in this laboratory study. Chemical analyses were performed to determine the pre-incubation characteristics of both fresh dredged sediment samples and oxidized samples after 23 weeks of incubation. Total element concentrations were determined after digestion in aqua regia by ICP-MS or ICP-OES. The leachable concentration of elements was determined by using the two-stage shaking test (method SFS-EN 12457-3). The leaching of harmful elements (Cd, Co, Ni, Mn, and Zn) was high in the acidified dredged spoil samples. Also, the leaching of S was high. The soluble concentration was dependent on total concentration, pH, and the mobility of the elements.During a 23-week oxidation period, the impact of various amounts of industrial side streams (alkaline ashes, industrial lime residues) as neutralizing agents on the acid-generating dredged sediments was investigated in the laboratory. Calcite was used as a reference material. pH measurements were carried out during the incubation period. The leaching of elements was determined with a modified method based on the SFS-EN 12457-2 standard before and after oxidation.The untreated dredged spoils and the samples treated with too low amounts of neutralizing agents, acidified to pH < 4 during the oxidation period. Thus, harmful elements were leached out. However, the 100 % theoretical calculated neutralization need was suitable to prevent acidification and thus the leaching of harmful substances from the neutralized acid-generating dredged spoils. However, the leaching of Mo increased at neutral pH values. The results showed that industrial side streams can be applicable for the neutralization of acid sulfate soil materials. However, the legislation must also be considered.

Micro-remediation Experiments of Acid Sulphate Soils

Micro-remediation Experiments of Acid Sulphate Soils

The Use of Rice Harvest Residue as Soil Amendment for Growth and Yield of Rice (Oryza sativa L.) on Acid Sulfate Soil

The area of rice fields in Indonesia decreased every year. Acid sulfate soil, which was sub-marginal land, had the potential to be converted into rice fields, but it needed improvement, one of which was by using organic materials as ameliorants. This research aimed to obtain the best composition of applying rice harvest residue as an ameliorant on acid sulfate soil in improving the growth and yield of rice. The research was conducted at the greenhouse of Panca Bhakti University Pontianak from January to April 2022. This study used a Completely Randomized Design (CRD). The treatments consisted of: p0: Control, p1: Rice straw = 40 gr/polybag, p2: Rice husk = 40 gr/polybag, p3: Rice husk charcoal = 40 gr/polybag, p4: Rice husk ash = 40 gr/polybag, p5: Rice straw + rice husk, p6: Rice straw + rice husk charcoal, p7: Rice straw + rice husk ash, p8: Rice husk + rice husk charcoal, p9: Rice husk + rice husk ash, p10: Rice husk charcoal + rice husk ash, with each material weighing 20 gr/polybag. The observation variables were plant height, number of tillers, number of productive tillers, dry weight of grains per hill, and 100-grain weight. Analysis of variance used F-test and continued with Least Significant Difference (LSD) test at the 5% level. The application of rice harvest residue had a better effect on the growth and yield of rice than the treatment without the application of rice harvest residue. Treatment p6 had the best effect on the dry weight of grains per hill, which was 65.67 grams. Keywords: Acidic Sulfate Soils, Ameliorant, Rice, Rice husk charcoal, Straw

Assessment of agricultural water protection strategies at a catchment scale: case of Finland

For decades, water quality monitoring programmes, agri-environment schemes and environmental permits for animal farms have targeted a decrease in agricultural loads. These have been supplemented with more recent policies related to nutrient recycling and a circular economy. However, eutrophication of surface water bodies remains a widespread problem. In this paper, we focus on the nutrient loading and recycling in the catchment of Eurajoki River, Finland. We statistically examine the generation of nutrient loading and its variation on a sub-catchment scale. We extend this examination to the factors behind the loading and estimate the impact of nutrient recycling on it. Our analysis reveals shortcomings in the availability and collection of data on the agricultural nutrient loadings and the parcel-specific data on the presence and application of manure and fertilisers. Nine sub-catchments were responsible for roughly half of the TP loading from the 46 sub-catchments studied. To reveal such hot spots and to better target agricultural water protection measures, we recommend short-term water quality sampling campaigns. Judging from our data, the rate of manure recycling is not high enough to reduce the regional P surplus to manageable levels. Therefore, we suggest facilitated collaboration between animal and crop farms to decrease the nutrient surplus. We also propose setting up a national database containing parcel-specific information, for example, on soil P content, manure and fertiliser application, agricultural practices and the presence of acid sulphate soils. We also suggest an independent soil fertility sampling to provide valid baseline soil P data for field parcels.

Manganese cycling and transport in boreal estuaries impacted by acidic Mn-rich drainage

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-termwaterchemistrydata 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.

Formation of Acid Sulfate Soils under the Influence of Acid Mine Waste in the Taiga Zone

Formation of Acid Sulfate Soils under the Influence of Acid Mine Waste in the Taiga Zone

Development of facile field-test paper for rapid determination of iron contamination in natural water of acid sulfate soils

Abstract 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.