Gypsum Amendment Research Articles

Gypsum amendment influences soil and plant chemical composition temporarily

Field application of gypsum (CaSO4 × 2H2O) is a tool to decrease phosphorus (P) load to watercourses. Effects of gypsum application (4 tons ha-1) on soil and crop composition were monitored up to four years after the treatment in the Savijoki catchment, southwestern Finland. Eleven amended fields and 17 control fields were analyzed for easily soluble P, Ca, Mg, K, S, pH(H2O), electrical conductivity (EC) and loss-on-ignition. Plant samples were analyzed for most nutrients and Se. Downward S transport was monitored in two fields. In the first spring after gypsum application, but not later, S concentrations and EC were substantially but not harmfully elevated in the plough layer, with no other significant effects on soil composition. Sulfur leached out slightly less rapidly from clay than from the coarse mineral soil. Plant S concentration increased for the first and the second year. In conclusion, gypsum application did not have adverse effects on soil or crop chemical composition in this survey of predominantly clay soils.

Response of soil microbial Communities, inorganic and organic soil carbon pools in arid saline soils to alternative land use practices

Soil organic and inorganic carbon (SOC & SIC) and microbial community structure are key indicators of soil quality and productivity in arid-saline soils. Salinity stress and diminishing availability of freshwater (FW) for irrigation are major constraints for productivity and improving soil quality indicators. Using treated wastewater (TW) and implementing climate-smart cropping systems are promising alternatives to replace freshwater usage in intensive cropping systems, however, impacts on the microbial community and net-carbon sequestration potential are not clearly understood. This field study was conducted in an arid saline-soil to investigate soil microbial community structure and soil carbon contents under a combination of treatments comparing bioenergy sorghum (So) and switchgrass (Sg), two irrigation water sources (FW & TW), and gypsum amendment (GA), to a native-soil control. After three years of implementing these treatments, soil samples were collected and analyzed for total carbon (TC), SOC, SIC, microbial biomass-carbon (MBC) and microbial community structure. Results showed that TW increased microbial diversity and shifted the community structure towards copiotroph-dominated prokaryotes. Several predominant and responsive taxa were associated with divergent trends of SOC, SIC and salinity parameters. Both SOC and SIC pools were sensitive to treatments and demonstrated divergent trends, as contents of TC and SOC were higher in TW-treatments, but of SIC were significantly lower in several So_TW treatments. Treatment TW_So_GA assembled a distinctive microbial community structure, accumulated the highest content of SOC (7.66 g kg−1) but recorded the lowest content of SIC (6.63 g kg−1). The lowest content of SOC was observed in native soil (4.58 g kg−1) but contained the highest SIC (8.15 g kg−1). The study results revealed the agronomic systems with higher potential for increasing TC and SOC content in arid-saline soils. Surface soil SIC was responsive to agronomic management, and several treatments produced disparate impacts on SOC and SIC stocks, which warrant for considering TC as the key indicator for assessing carbon sequestration in arid lands.

Microbial biomass activity of a sodic Lixisol reclaimed with gypsum and clean water irrigation in urban vegetable systems of Burkina Faso

AbstractBackgroundLittle is known about the effects of gypsum application to remediate saline–sodic soils in the tropics and the role of microbial indicators in soil reclamation.AimsOur study aimed at (1) remediating a highly weathered, irrigated sodic Lixisol under prolonged urban crop production by clean water and gypsum application and (2) to determine the remediation effects on soil microbial indices.MethodsA three‐factorial on‐farm experiment with maize (Zea mays L.) was used to study effects on soil microbial biomass of (1) soil degradation at two levels of salinity, (2) irrigation with clean water and wastewater, and (3) the impact of added gypsum during a typical growing season.ResultsAt the high‐degradation site, the 0.5 M K2SO4 extractable carbon (C) content was 40% higher than at the low‐degradation site. In addition, microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were 20% lower than at the low‐degradation site, while fungal ergosterol was even 40% lower, leading to a 33% lower ergosterol/MBC ratio. Wastewater irrigation increased MBN but decreased ergosterol content at the low‐degradation site while having no effect at the high‐degradation site. Gypsum amendment led to higher MBN at the low‐degradation site but to lower MBN at the high‐degradation site. Gypsum amendment always increased the ergosterol content whereby this increase was stronger at the low‐degradation site, especially in combination with wastewater irrigation.ConclusionsFrom a microbial perspective, high soil degradation levels should be avoided by treatment of a saline–sodic wastewater prior to its use for irrigation rather than relying on future remediation strategies of affected field sites.

Influence of Flue Gas Desulfurization Gypsum on Phosphorus Loss in Pine Bark Substrates

Flue-gas desulfurization (FGD) gypsum, a byproduct of coal-fired electrical utility plants, has been shown to effectively reduce phosphorus (P) leaching in many agricultural systems. However, its applications in horticultural production systems have been insufficiently researched resulting in limited industry adoption. To evaluate the efficacy of FGD gypsum to reduce P leaching in horticultural media, pine bark substrates were amended with FGD gypsum at 2.5, 5, and 10% (v/v). In accordance with industry practice, controlled release fertilizer (19N-3P-10K) was amply incorporated into all potting media treatments to support primary nutrient sufficiency of transplanted stock. The greatest P leaching occurred in the control substrates containing only pine bark and fertilizer. The standard pine bark substrate treatment, containing lime and micronutrients, reduced total P leaching by 35% and should be considered a best management practice. The addition of FGD gypsum at 2.5, 5, and 10% (v/v) reduced the total P collected in leachate by 47, 59, and 70%, respectively. Gypsum amendments increased potassium leachate concentrations but elevated potassium levels normalized after ~20 days. With little to no effect on substrate physical properties or pH, pine bark substrates can be amended with FGD gypsum to effectively reduce P leaching in short-term crops.

Enhanced attenuation of arsenic by Quaternary agricultural soils of Eastern Punjab, India upon anionic clays and gypsum amendment

ABSTRACT Agricultural soil of the Sutlej River basin was evaluated for its natural attenuation efficacy for arsenic (As) under the field variables of pH, competitive anions, contact time and varied As contents. The role of layered double hydroxides (HTLDH) and gypsum on uptake efficiency and long-term stability of entrapped As demonstrates rapid As uptake by both geosorbents without mineral structure altering. Arsenic retention by gypsum is poorer than that by HTLDH and greater uptake (∼100% within 2 h) was achieved in the co-precipitation process than adsorption on HTLDH. Freundlich isotherm and pseudo-second-order kinetic model fits of the data demonstrate the multilayer rate-limiting sorption process. NO3 – and PO4 3– hardly affected As retention capacity of HTLDH and gypsum with greater retention at pH 6 and high sorbate concentrations. Studied soil shows a strong potential for As (0.68 g kg−1) which enhanced upon adding HTLDH, while gypsum lowered As retention efficiency of soil except at pH 6.0. Gypsum exhibited relatively greater desorption than HTLDH where almost no As was desorbed in the latter case within seven days of exposure, but ∼30% sorbed As gets desorbed from gypsum which was further enhanced by NO3 –+PO4 3− and soil mixing. Identical behaviour was observed from the soil and HTLDH/gypsum mixture at variable ratios as well. This study shows that MgFe-based HTLDH can efficiently retard arsenic mobilization from the soil with competitive anions and wide pH ultimately limiting As bioavailability in the environment and can be successfully used as a potential scavenger for As remediation purposes.

Greenhouse Gas Emissions from Salt-Affected Soils: Mechanistic Understanding of Interplay Factors and Reclamation Approaches

Salt-affected soils contain high levels of soluble salts (saline soil) and exchangeable sodium (alkali soil). Globally, about 932 million ha (Mha), including 831 Mha of agricultural land, is salt-affected. Salinity and sodicity adversely affect soil microbial diversity and enzymatic activities, and thereby carbon and nitrogen dynamics and greenhouse gas (GHG) emissions from soils. In this review article, we synthesize published information to understand the impact of salinity and sodicity on GHG production and emissions from salt-affected soils, and how various reclamation amendments (gypsum, phosphogypsum, organic manure, biochar, etc.) affect GHG emissions from reclaimed soils. Nitrous oxide (N2O) and methane (CH4) emissions are of greater concern due to their 298 and 28 times higher global warming potential, respectively, compared to carbon dioxide (CO2), on a 100-year time scale. Therefore, CO2 emissions are given negligible/smaller significance compared to the other two. Generally, nitrous oxide (N2O) emissions are higher at lower salinity and reduced at higher salinity mainly due to: (a) higher ammonification and lower nitrification resulting in a reduced substrate for denitrification; (b) reduced diversity of denitrifying bacteria lowered down microbial-mediated denitrification process; and (c) dissimilatory nitrate reduction to ammonium (DNRA), and denitrification processes compete with each other for common substrate/nitrate. Overall, methane (CH4) emissions from normal soils are higher than those of salt-affected soils. High salinity suppresses the activity of both methanogens (CH4 production) and methanotrophs (CH4 consumption). However, it imposes more inhibitory effects on methanogens than methanotrophs, resulting in lower CH4 production and subsequent emissions from these soils. Therefore, reclamation of these soils may enhance N2O and CH4 emissions. However, gypsum is the best reclamation agent, which significantly mitigates CH4 emissions from paddy cultivation in both sodic and non-sodic soils, and mitigation is higher at the higher rate of its application. Gypsum amendment increases sulfate ion concentrations and reduces CH4 emissions mainly due to the inhibition of the methanogenesis by the sulfate reductase bacteria and the enhancement of soil redox potential. Biochar is also good among the organic amendments mitigating both CH4 and N2O emission from salt-affected soils. The application of fresh organic matter and FYM enhance GHG emissions for these soils. This review suggests the need for systematic investigations for studying the impacts of various amendments and reclamation technologies on GHG emissions in order to develop low carbon emission technologies for salt-affected soil reclamation that can enhance the carbon sequestration potential of these soils.

Enhancing salt leaching efficiency of saline-sodic coastal soil by rice straw and gypsum amendments in Jiangsu coastal area

High salinity-sodicity affects large areas of newly-reclaimed land in many coastal regions that need proper leaching before they become productive. However, poor soil properties make salt-leaching process ineffective. In this study, leaching experiments were used to assess the effectiveness of adding gypsum and rice straw in improving salt-leaching efficiency. Four treatments, control, rice-straw, gypsum, and gypsum and rice-straw, with two replicates, each were tested to find the optimal combination. After soils were leached, property changes were measured, such as main dissolved cations, conductivity, and pH. Gypsum and rice straw treatment turned out to be the best, where EC e , sodium adsorption ratio, and exchangeable sodium percentage dropped to 3.61%, 5.04%, and 8.14%, respectively. These values reached the safe limit of salinity-sodicity (EC e ≤ 4dS m −1 , ESP ≤ 15%). In addition, the incorporation of rice-straw with gypsum affects the ability to increase the removal of sodium and thus enhance salt-leaching efficiency.

Photosynthetic Pigments, Symbiotic Traits, Yield Attributes and Nutrient Uptake of Soybean Crop as Influenced by Soil Amendments on Degraded Vertisol of Chambal Tablelands

Background: Gypsum and organic amendments are potential ameliorants for reclamation of saline and/or sodic soil conditions to improve crop productivity and soil fertility. Application of gypsum at higher dose ( greater than 1 t ha-1) with organic amendments such as FYM, crop residue on soybean crop is largely unknown for salt affected soils. Impact of these soil amendments on soybean chlorophyll pigments, symbiotic traits, nutrient uptake, nutrient harvest index, carbohydrate equivalent yield, crop productivity and economic returns is not being addressed properly. This is particularly true for oilseed crop grown under saline conditions. Methods: A field experiment was conducted for two years (2017 and 2018) to assess the impact of amendments like gypsum, crop residue (CR), farm yard manure (FYM) with recommended dose of nitrogen-phosphorus-potassium (RNPK) fertilizer dose on soybean crop in degraded vertisol with eight treatments and three replications laid in randomized block design. Result: Results revealed that among treatments, phenological traits such as total chlorophyll (1.561 and 1.593mg g-1), carotenoid (0.156 and 0.154 mg g-1) at 30DAS (days after sowing), nodulation traits (33.6 and 32.4 nodules plant-1) and dry matter accumulation (26.2 and 23.9 g plant-1 at harvest) improved significantly in RNPK+Gypsum+CR+FYM and RNPK+Gypsum+FYM treatments respectively. Combined application of fertilizers with organic and gypsum amendments increased soybean yield by the magnitude of 49-53% compared to only fertilizer applied treatments. Higher biological yield (4169-4339 kg ha-1), carbohydrate equivalent yield (258.8-266.5 kg ha-1) and nutrient uptake (118: 8:47:11 -140: 9: 57: 12 kg ha-1N:P:K:S) were observed in RNPK+Gypsum+CR±FYM treatments. Economic analysis showed higher net returns and benefit-cost ratio in RNPK+Gypsum+CR (Rs 15247 and 1.48) and RNPK+Gypsum (Rs 14499 and 1.59) treatments.

Gypsum amendment influences performance and mineral absorption in wheat cultivars grown in normal and saline‐sodic soils

AbstractIn arid and semi‐arid regions, soil salinity and sodicity are the most common constraints to agriculture production, in particular in North Africa. The effect of gypsum application has been widely studied in saline‐sodic soils. However, the gypsum amendment's influence on the performance, productivity and mineral absorption of salt‐sensitive and tolerant wheat cultivars in both saline‐sodic and normal soils under field conditions has not yet been investigated. A two‐season (2016–17 and 2017–18) field experiment was undertaken to investigate the impact of gypsum on wheat growth, yield and minerals uptake for salt‐tolerant and sensitive cultivars grown in normal (EC = 1.3 dS m−1, pH = 8.4 and ESP = 7.1–8.0%) and saline‐sodic soils (EC = 5.8–6.2 dS m−1, pH = 8.8 and ESP = 19.3–22.4%) in the western Nile delta, Egypt. The gypsum requirement was applied to decrease the initial ESP from 19.3–22.4 to 10.0% was calculated for 0.3 m soil depth. Gypsum application (6.0 and 4.7 ton ha1, for the first and second season, respectively) reduced soil pH, EC and ESP of saline‐sodic soil by 31.6, 7.3 and 39.0%, respectively (two‐season mean). Furthermore, gypsum application increased Ca2+, Mg2+ and K+ in the flag leaf by 54.7, 24.5 and 45.7%, respectively (2‐season mean) under saline‐sodic soil. While, in the normal soil, gypsum application increased Ca2+, Mg2+ and K+ by 67.3, 32.7 and 78.7%, respectively. In contrast, gypsum applications decreased Na+ and Cl− content by 17.2 and 15.0% and by 40.0 and 35.5%, respectively, in the saline‐sodic and normal soil, respectively. Under saline‐sodic and normal soils, gypsum application significantly increased the K/Na ratio by 90.0 and 175.2%, respectively (2‐season mean). Interestingly, across cultivars, gypsum amendment increased grain yield by 20.7% (6.9 to 8.3 t ha−1) for normal soil and by 8.0% (5.8 to 6.3 t ha−1) for saline‐sodic soil. The positive impact of gypsum was more pronounced under the normal soil and for the salt‐sensitive cultivars than in saline‐sodic soil and for salt‐tolerant cultivars. Growers can cultivate salt‐tolerant cultivars and use gypsum as a precaution to reduce saline‐sodicity build‐up and to increase nutrient absorption.

Alum and Gypsum Amendments Decrease Phosphorus Losses from Soil Monoliths to Overlying Floodwater under Simulated Snowmelt Flooding

Phosphorus (P) loss from soils poses a threat of eutrophication to downstream waterbodies. Alum (Al2(SO4)3·18H2O) and gypsum (CaSO4·2H2O) are effective in reducing P loss from soils; however, knowledge on their effectiveness under cold temperatures is limited. This study examined the reduction of P loss from soils with alum and gypsum amendment under simulated snowmelt flooding. Intact soil monoliths (15 cm depth) collected from eight agricultural fields in flood-prone areas of Manitoba, Canada, were surface amended with alum or gypsum, pre-incubated for 2 weeks, then flooded and incubated at 4 °C for 8 weeks. Porewater and floodwater samples collected weekly were analyzed for dissolved reactive P (DRP), dominant cations and anions. An enhanced P release with flooding time was observed in all soils whether amended or unamended; however, alum/gypsum amendment reduced DRP concentrations in porewater and floodwater in general, with alum showing a more consistent effect across soils. The reduction in floodwater DRP concentrations (maximum DRP concentration during flooding) with alum and gypsum ranged from 34–90% and 1–66%, respectively. Based on Visual MINTEQ thermodynamic model predictions, precipitation of P and formation of P-sorbing mineral species with alum and gypsum amendment reduced DRP concentrations at latter stages of flooding.

Evaluation of groundwater quality for irrigation water supply using multi-criteria decision-making techniques and GIS in an agroeconomic tract of Lower Ganga basin, India

Groundwater irrigation has evolved the monocropping cultivation pattern to multi-cropping, especially in many arid/semi-arid tracts globally. Irrigation practices with the groundwater of poor quality can limit the selection of the crop, reduce crop yields and degrade the soil quality. The present study has been undertaken to identify the hydrogeochemical phenomena of groundwater systems in the south-western Birbhum district, India and to analyze groundwater suitability for irrigation during the pre-and post-monsoon cycles by adopting the Irrigation Water Quality Index (IWQI) using Multivariate Factor Analysis along with some traditional methods viz. sodium adsorption ratio, sodium percentage, magnesium hazards, residual sodium bicarbonate (RSBC) and carbonate (RSC), Wilcox's and USSL diagrams, permeability index and Kelly's index. The hydrogeochemical analysis revealed that chemical weathering and evaporation are predominant in the aquifer systems. Groundwater quality reflected soil salinity, sodicity and magnesium hazards risks and water toxicity to the sensitive plants at 0–46.4% of the post-monsoon samples and 0–38.4% of the pre-monsoon samples based on the individual traditional methods whereas about 97.73–98.88% of the total area was classified as moderate to severely unsuitable for irrigation during both seasons when integrated multiple parameters using the IWQI method. Prolonged use of such groundwater for irrigation is susceptible to causing moderate to severe infiltration problems at a greater extent of the study area. The study recommends adaptation of salinity, sodicity and RSC/RSBC reduction procedures (e.g., the use of acid and gypsum amendments in the irrigation lands and through water blending) and advanced irrigation practices (viz. drips, sprinklers and micro irrigations) to prevent soil degradation and increase crops productivity. Adopting Managed Aquifer Recharge procedures as well as rainwater harvesting in the areas bearing unsuitable water quality can dilute the ionic concentrations of the groundwater facies which in turn will improve the groundwater quality for irrigation.

Flooding-induced inorganic phosphorus transformations in two soils, with and without gypsum amendment.

Anaerobic conditions developed during flooding can increase phosphorus (P) losses from soils to waterways. Soil amendment with gypsum (CaSO4 ·2H2 O) can effectively reduce flooding-induced P release, but its effectiveness is soil dependent, and the reasons are poorly understood. The objectives of this study were to reveal the possible inorganic P transformations during flooding of two soils (acidic-Neuenberg sandy loam [NBG-SL] and alkaline-Fyala clay [FYL-Cl]), with and without gypsum amendment prior to flooding. Porewater samples collected at 0, 35, and 70 d after flooding (DAF) from soils incubated in vessels were analyzed for dissolved reactive P (DRP); pH; and concentrations of calcium (Ca), magnesium, iron (Fe), manganese, chloride, nitrate, sulfate, and fluoride. Thermodynamic modeling using Visual MINTEQ software and chemical fractionation of soil P were used to infer P transformations. Soil redox potential (Eh) decreased with flooding and favored reductive dissolution of Fe-associated P increasing porewater DRP concentrations. Greater solubility of Ca-P under acidic pH maintained a higher DRP concentration in NBG-SL during early stages of flooding. A subsequent increase in pH with flooding and higher Ca concentration with added gypsum enhanced the stability of Ca-P (β-tricalcium phosphate and octacalcium phosphate), reducing the DRP concentration in gypsum-amended NBG-SL. Stability of Ca-P was less affected with flooding and gypsum amendment in FYL-Cl soil because it had an alkaline pH and inherently higher Ca concentration. The FYL-Cl, with a more rapid decrease in Eh than NBG-SL, became severely reduced, releasing more P and Fe by 70 DAF. These conditions favored vivianite formation in FYL-Cl but not in NBG-SL.

Efficacy of sulphuric acid and gypsum amendments on sodic soil reclamation under various water regimes

Efficacy of sulphuric acid and gypsum amendments on sodic soil reclamation under various water regimes

Risk Assessment of Gypsum Amendment on Agricultural Fields: Effects of Sulfate on Riverine Biota.

Gypsum (CaSO4∙2H2O) amendment is a promising way of decreasing the phosphorus loading of arable lands, and thus preventing aquatic eutrophication. However, in freshwaters with low sulfate concentrations, gypsum‐released sulfate may pose a threat to the biota. To assess such risks, we performed a series of sulfate toxicity tests in the laboratory and conducted field surveys. These field surveys were associated with a large‐scale pilot exercise involving spreading gypsum on agricultural fields covering 18% of the Savijoki River (Finland) catchment area. The gypsum amendment in such fields resulted in approximately a four‐fold increase in the mean sulfate concentration for a 2‐month period, and a transient, early peak reaching approximately 220 mg/L. The sulfate concentration gradually decreased almost to the pregypsum level after 3 years. Laboratory experiments with Unio crassus mussels and gypsum‐spiked river water showed significant effects on foot movement activity, which was more intense with the highest sulfate concentration (1100 mg/L) than with the control. Survival of the glochidia after 24 and 48 h of exposure was not significantly affected by sulfate concentrations up to 1000 mg/L, nor was the length growth of the moss Fontinalis antipyretica affected. The field studies on benthic algal biomass accrual, mussel and fish density, and Salmo trutta embryo survival did not show gypsum amendment effects. Gypsum treatment did not raise the sulfate concentrations even to a level just close to critical for the biota studied. However, because the effects of sulfate are dependent on both the spatial and the temporal contexts, we advocate water quality and biota monitoring with proper temporal and spatial control in rivers within gypsum treatment areas. Environ Toxicol Chem 2022;41:108–121. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effect of Irrigation with Industrial Wastewater and Gypsum Amendments on Heavy Metal in Soil and Black Cumin (Nigella sativa L.) Seed

ABSTRACT Irrigation with wastewater is possible in many arid and semi-arid countries that suffering from water shortage. Furthermore, addition of gypsum (CaSO4. 2H2O) to soil may be reduce effluent problems. This research targeted the consequences of gypsum and wastewater on soil properties, yield components, and element content in soils and Black cumin (Nigella sativa L.) seeds. Factorial and completely randomized designs were conducted at the research station of Avicenna herb garden. The results showed that gypsum (0, 3.48, 4.34, and 5.21 g kg–1) and treated wastewater (0, 25, 50, 75, 100%), significantly affected soil heavy metal content. The highest concentrations of heavy metals found in the soil were iron (Fe), and the lowest copper (Cu) but, their values were below the critical level. The highest concentration of heavy metal in black cumin was iron found in the roots and stems, and the lowest was copper in the same plant parts. Generally, gypsum at the rate of 5.21 gkg−1 and the irrigation with 75% concentration of effluent, increased significantly the plant yield components and heavy metals concentration in different black cumin organs. Still, the concentrations of all heavy metals studied were found within the standard limits.

Integrating column leaching experiments and geochemical modelling to predict the long-term alkaline stability during erosion process for gypsum amended bauxite residue

Gypsum amendment is widely used to resolve alkalinity issues and implement sustainable management for bauxite residue disposal areas (BRDAs). Amended BRDAs under natural conditions suffer from long-term erosion processes. Nevertheless, the effect of erosion on amendment efficacy is rarely assessed. In this study, by integrating the geochemical modelling of PHREEQC and column leaching experiments, the dissolution of alkaline solids in bauxite residue (BR) and gypsum amendment, as well as their environmental behaviors, were determined through a 1-year simulated rainfall leaching experiment. The PHREEQC simulation results demonstrated that Na+ ion strength, CO2 partial pressure and rainfall, all affected the saturation index (SI) of calcite significantly and accelerated its corrosion, leading to the dissolution of gypsum and calcite in a relatively stable state. However, Na+ ion strength and rainfall significantly acted on the SI of gypsum, which lead to loss of Ca2+ and reduction of alkaline stability. In addition to the effects of Na+ and Ca2+ on the saturation concentration of gypsum and calcite solution, Na+ and Ca2+ also exhibited significant effects on the equilibrium of chemical species reactions. The column results confirmed that stability of gypsum and calcite was consistent with the simulation results of PHREEQC in the BRDAs environment. Furthermore, multiple linear regressions revealed differences in combined contributions of rainwater and atmospheric CO2 on the stability of calcite and gypsum. The PHREEQC simulation provides a new approach to predict long-term alkaline stability of BR as well as to establish sustainable remediation on BRDAs during erosion process.

Remediating Agricultural Legacy Nutrient Loads in the Baltic Sea Region

The Baltic Sea is considered the marine water body most severely affected by eutrophication within Europe. Due to its limited water exchange nutrients have a particularly long residence time in the sea. While several studies have analysed the costs of reducing current nutrient emissions, the costs for remediating legacy nutrient loads of past emissions remain unknown. Although the Baltic Sea is a comparatively well-monitored region, current data and knowledge is insufficient to provide a sound quantification of legacy nutrient loads and much less their abatement costs. A first rough estimation of agricultural legacy nutrient loads yields an accumulation of 0.5–4.0 Mt N and 0.3–1.2 Mt P in the Baltic Sea and 0.4–0.5 Mt P in agricultural soils within the catchment. The costs for removing or immobilising this amount of nutrients via deep water oxygenation, mussel farming and soil gypsum amendment are in the range of few tens to over 100 billion €. These preliminary results are meant as a basis for future studies and show that while requiring serious commitment to funding and implementation, remediating agricultural legacy loads is not infeasible and may even provide economic benefits to local communities in the long run.

Gypsum amendment and seasonal variability: effect on soil quality, fruit characteristics and toxicological responses of Cucumber (Cucumis sativus l.) in the Ahafo-Kenyasi Mining Area of Ghana

Gypsum amendment and seasonal variability: effect on soil quality, fruit characteristics and toxicological responses of Cucumber (Cucumis sativus l.) in the Ahafo-Kenyasi Mining Area of Ghana

Gypsum amendment and seasonal variability: effect on soil quality, fruit characteristics and toxicological responses of Cucumber (Cucumis sativus l.) in the Ahafo-Kenyasi Mining Area of Ghana

Depending on soil, climate and crop characteristics exposed subsoils can be amended with gypsum for agricultural activities when topsoil is inadequate as a result of natural and geophysical activities. To determine how exposed subsoil amendment with gypsum interact with weather patterns to influence soil chemical properties, cucumber growth, fruit characteristics and heavy metal concentration, a two-seasonal experiment was conducted in the major and minor rainy season of 2020 in the Ahafo-Kenyasi Mining Area in Ghana. The experiment was laid out as a 6x2 factorial arranged in randomized complete block design, consisting of 6 gypsum application rates (20 ton/ha, 40 ton/ha, 60 ton/ha, 80 ton/ha, 0 ton/ha (subsoil control) and 0 ton/ha (topsoil control)) in two rainy seasons and replicated three times. The results show that gypsum application and rainy seasons interact to significantly influence soil chemical properties, cucumber growth and fruit characteristics. Increasing gypsum application resulted in decreased organic carbon, increased calcium, increased available P, increased exchangeable magnesium (Mg), increased pH during both major and minor rainy seasons. Vine length, number of leaves, number of fruits per plant and fruit weight of cucumber were increased with increasing gypsum application during the minor rainy season. In spite of exceeding permissible limits in soils and crops, arsenic (As), cadmium (Cd) and mercury (Hg) showed similar concentrations (below 2 mg/kg) in cucumber during the minor and major rainy seasons across gypsum treatments. Lead (Pb) concentration in cucumber was significantly higher in the major season across treatments. There was no difference in lead (Pb) concentration for treated vs untreated, and no increase across the amendment range. Further studies on how heavy metals in soil and plants interact with plant phytochemicals in ecosystems and living tissues are recommended.

Gypsum Amendment Induced Rapid Pyritization in Fe-Rich Mine Tailings from Doce River Estuary after the Fundão Dam Collapse

Mine tailings containing trace metals arrived at the Doce River estuary, after the world’s largest mine tailings disaster (the Mariana disaster) dumped approximately 50 million m3 of Fe-rich tailings into the Doce River Basin. The metals in the tailings are of concern because they present a bioavailability risk in the estuary as well as chronic exposure hazards. Trace metal immobilization into sulfidic minerals, such as, pyrite, plays a key role in estuarine soils; however, this process is limited in the Doce River estuarine soil due to low sulfate inputs. Thus, to assess the use of gypsum amendment to induce pyritization in deposited tailings, a mesocosm experiment was performed for 35 days, with vinasse added as carbon source and doses of gypsum (as a sulfate source). Chemical and morphological evidence of Fe sulfide mineral precipitation was observed. For instance, the addition of 439 mg of S led to the formation of gray and black spots, an Fe2+ increase and decrease in sulfides in the solution, an increase in pyritic Fe, and a greater Pb immobilization by pyrite at the end of the experiment. The results show that induced pyritization may be a strategy for remediating metal contamination at the Doce River estuary.