Weathered Soils Research Articles

The Mineral Characteristic of Tropical Residual Soil using X-Ray Diffraction (XRD) and Scan Electron Microscopy (SEM)

Volcanic residual soil has unique characteristics due to weather and morphological influences. High temperatures and large amounts of rainfall made the rock weathering intense. Landslide events in volcanic residual soil of West Java are quite serious, more than 100 incidents in total a year. Landslides that occur due to unsaturated conditions on the top of the slope become saturated, so it is very important to conduct research on these tropical residual soil weathering zones to define its mineral characterization using Scan Electron Microscopy (SEM) and X-Ray Diffraction (XRD). From the research it was found that the dominant mineral types and contents were Halloysite and Kaolinite minerals. A typical mineral profile is found that is Goethite and Hematite minerals at the soil surface, Carbonate and Chlorite minerals in deeper soils and large amounts of Feldspar minerals in more deep layers. Because there are unique minerals at each depth of soil weathering, zone classification can be done easily starting from the Initial Leaching Zone at the deepest part where there is Feldspar, the Mineral Washing Zone there is Carbonate and Chlorite and the Oxidation Zone on the surface (there are Oxide and Hydroxide minerals). So that it can form a Residual Tropical Volcanic Weathering Profile.

Temporal changes in soil profile chemical properties in an 18‐year grassland restoration in the US Mid‐Atlantic Coastal Plain

AbstractMany grassland restorations have been established in the United States over the past few decades, as native tallgrass prairies have often been converted to agriculture. However, only a few of the restorations have been initiated on the east coast of the United States. The objective of this field study was to evaluate the short‐ (∼3.5 years) and long‐term (∼15 years) changes in soil chemical properties among soil depths in a grassland restoration initiated in 1999 on previously cultivated, highly weathered soils of the Mid‐Atlantic Coastal Plain. Soil was collected in 2006 and 2018 to a depth of 20 cm and sectioned into 2.5 or 5 cm depth intervals and compared to pre‐burn conditions from 2003. Soil pH was 0.2 to 0.3 pH units lower in the 2.5–20 cm depth interval in 2018 compared to 2003. Extractable soil calcium was 25% lower and magnesium was 35% lower in the 2.5–5.0 and 2.5–20 cm depth intervals, respectively, in 2018 compared to 2003. Total carbon (TC) and total nitrogen (TN) were greater in the 2.5–5.0 and 2.5–10‐cm depths, respectively, in 2018 compared to 2003. Measured soil carbon (C) and nitrogen sequestration rates were 82 g TC m−2 year−1 and 0.27 g TN m−2 year−1 in the top 20 cm of soil. Grassland restorations contribute ecosystem services, including soil C sequestration; however, land managers may need to consider adding lime to grassland restorations on nutrient‐poor soils that are naturally acidic or have become acidified over time if the land is returned to agricultural production.

Soil chronosequence derived from landslides on the upper reach of Minjiang River, western China

Soil chronosequences derived from landslides with certain time series are the great avenue to elevate our understanding on the processes of pedogenesis, nutrient dynamics, and ecosystem evolution. However, the construction of reliable soil chronosequence from historical landslides remains intricate. Here, we presented a 22,000-year soil chronosequence from multiple landslides on the upper reach of Minjiang River, western China. The variation in a variety of pedogenesis indices and soil nutrients verified the reliability of the chronosequence. The silica-alumina ratio and silica sesquioxide ratio decreased significantly with soil age. This reflected the enrichment of Al/Fe/Ti oxides but the depletion of Si oxides with the soil development. Meanwhile, the values of the Chemical Index of Weathering and the Chemical Index of Alteration increased significantly with soil age, especially from 5 to 89 years. These variations were attributed to the soil weathering, which led to the destruction of soil minerals with the rapid loss of most of cations (e.g., K, Na, Ca, and Mg) during the soil development. The concentrations of carbon and nitrogen in topsoil increased with soil age, and the carbon accumulation rate slowed significantly from 5,500 to 22,000 years. The total phosphorus concentrations decreased with soil age, suggesting the gradual loss of soil phosphorus with soil development. The results indicate that the landslide chronosequence established on the upper reach of Minjiang River is reliable and delineates a long-term soil development process, which will provide a great platform for further improvement of biogeochemical theories and understanding sustainable vegetation restoration.

Chemical imaging reveals environmental risk of minor tungsten and lead shotgun pellet constituents during weathering in soil

Tungsten (W)-based shots are considered more environmentally safe than lead (Pb)-based shots, but knowledge about the W-shot fate in the soil environment is still limited, especially in terms of minor constituents such as iron, copper, and nickel (Ni). Contaminant behaviour in soil strongly depends on pH; in turn, the corrosion of metal composites may affect the pH locally. The aim of this study was to compare Pb- and W-shot weathering dynamics in soil (silt loam, pH 6.3) and reveal the interplay of shot weathering-induced pH-changes on the mobility of elements using in situ chemical imaging (Diffusive gradients in thin films for labile elements, planar optodes for soil pH) and batch incubation experiments over time (16 months). Despite our expectation to find acidification due to W oxidation, we observed a pH increase by 0.2 units in extracted soil solutions and by 0.6 units in the soil around W-shots as Ni dissolved from the binder phase of the shot. After 10 weeks, release of labile Ni was 3-times higher compared to W despite the low Ni content in the shot (7 %, m/m). Pb-shot oxidation increased soil solution pH by 0.5 units which likely supported mobility of Pb-shot-derived antimony (Sb). Steep gradients of labile W and Pb and soil solution concentrations <0.8 μmol L−1 indicated that transfer from shot to soil was low. Contrastingly, labile Ni and Sb were found up to ~4 mm from the shot surface and in higher soil solution concentrations as suggested by the shot constitution, indicating higher mobility of minor as compared to major shot constituents. After 16 months, 36 % of total Ni were dissolved in the soil solution highlighting the environmental relevance of minor shot constituents in Pb-shot alternatives after short term weathering in soil.

Chemical Weathering Rates of Soils Developed on Eocene Marls and Sandstones in a Mediterranean Catchment (Istria, Croatia)

Physical and chemical weathering, together with biological and biochemical processes, form soil from bedrock and strongly influence the chemical composition of natural waters. Erosive processes, primarily through the agents of running water and wind, remove the products of weathering from catchments. The aim was to determine the chemical weathering of minerals because of changes in land-use and natural forestation in two small neighboring catchments of the rivers Argilla and Bazuja. Agricultural land-use practice is very intense in the Argilla catchment, while the Bazuja catchment’s arable land is mostly abandoned, with progressive forestation. Chemical weathering in soils and sediments was evaluated with the aid of bulk chemistry analysis focused on major elements, trace elements, and zirconium. Weathering indices, mass balance, and strain were calculated. The abandonment of arable land and intense forestation in the Bazuja catchment caused increased chemical weathering with the loss of base cations (Ca and Mg) and enrichment of conservative elements (Zr and Ti) in surface horizons. EIC and MTF values are positive (enrichment) in areas with agricultural activities, while forested areas show negative values (loss). A comparison of the oldest and youngest parts of the overbank sediment profiles in the swallow hole zone and stream sediments shows that chemical and mechanical weathering in the Bazuja catchment was similar to present weathering in the Argilla catchment, while agriculture was active in the Bazuja catchment. The integrated knowledge gained in small catchment studies can be broadly applicable to larger systems.

Legacy phosphorus in Alabama Hartsells soil after long-term amendment with broiler litter.

Numerous studies have investigated effects of long-term manure application on total phosphorus (P) and inorganic P (Pi ), but few have evaluated soil organic P (Po ). Little is known about crop management effects on Po in soils with varying minerology. In this study, sequential fractionation was used to characterize specific P forms after 25 years of broiler litter (BL) or ammonium nitrate (Con) applications to an Alabama Hartsells soil. Crops (corn [Zea mays L.], soybean [GlycineWilld.], and corn or soybean with a wheat [Triticum aestivum L.] cover crop) were under conventional tillage (CT) or no-tillage (NT). Regardless of crop, tillage, or fertilizer type, the proportion of extractable Pi was relatively stable at 21%-49% at 0-5cm and 25%-45% at 5-10cm. Extractable Pi ranged from 0.69 to 2.4mg g-1 . BL increased total extractable Pi (p≤0.001) at 0-5cm and 5-10cm. Total extractable P was influenced at 0-5cm (p≤0.006) by both tillage and fertilization type, but not at 5-10cm or at either depth in soybean plots. Long-term BL application increased total extractable soil P at 0-5cm. In corn systems, CT did not reduce P loading to topsoil or result in P leaching to lower soil depths, compared to NT. Soybean and soybean-wheat reduced P loading in BL plots, compared to corn and corn-wheat. Soil Po was classed in the order of monoesters >phytate and polyphosphates, where most was extractable with NaOH. BL increased extractable Po in all fractions. Care should be taken when applying BL to highly weathered soils to avoid legacy Po accumulation. Soybean rotations and cover crops could help remediate P-laden soils after repeated BL application.

Impact of Urea-Intercalated-Biochar on N-Release in Soil and Humified Soil Organic Matter

This research investigated the impact of urea-intercalated-biochar (ICB) on nitrogen release as well as on humified soil organic matter (SOM) distribution in highly weathered soil. Incubation studies were performed with a typical dystrophic red Ultisol and with 10 treatments: soil without amendment (control, CON), soil with three doses of biochar (BC75, BC145, and BC 290), and soil with ICB doses (ICB75, ICB145 and ICB 290). BC and ICB were characterized by 13C Nuclear Magnetic Resonance 13C-NMR CP/MAS spectroscopy and elemental analyses. N-extractable forms were periodically determined by Kjeldahl method and humic substances (HS) distribution was analyzed on the 28th day after incubation begins (DAI). Intercalation of urea in BC increased sample N content from 2.7 to 22 %, whereas that of C decreased from 40 % to 28 %. As a consequence, C: N decreased from 14.9 to 1.3. The 13C NMR spectra of BC and ICB were similar but relative abundance of major organic functional groups differs, for example, ICB presented a greater proportion of C=O groups due to the carbonyl group of urea and a greater proportion of N/O alkyl C, O-alkyl C, and anomeric C groups due to the addition of starch. There was a significant increase in the concentration of extractable N-NH4+ by addition of urea from the onset of incubation down late period and a significant difference (P &amp;gt; 0.05) was obtained between the ICB and BC over time. This could be as a result of the less accessible form of N in the biochar materials due to the pyrolysis process. There was no evidence of extractable N-NO3- ion until 14 DAI, significant difference in N-NH4+ concentrations at 28 DAI between the ICB and control was observed over time and the highest value recorded from ICB treated pots at 145 and 290 kg N ha-1.

Centennial scale sequences of environmental deterioration preceded the end-Permian mass extinction

The exact drivers for the end-Permian mass extinction (EPME) remain controversial. Here we focus on a ~10,000 yr record from the marine type section at Meishan, China, preceding and covering the onset of the EPME. Analyses of polyaromatic hydrocarbons at sampling intervals representing 1.5–6.3 yr reveal recurrent pulses of wildfires in the terrestrial realm. Massive input pulses of soil-derived organic matter and clastic materials into the oceans are indicated by patterns of C2-dibenzofuran, C30 hopane and aluminum. Importantly, in the ~2,000 years preceding the main phase of the EPME, we observe a clearly defined sequence of wildfires, soil weathering, and euxinia provoked by the fertilization of the marine environment with soil-derived nutrients. Euxinia is indicated by sulfur and iron concentrations. Our study suggests that, in South China, centennial scale processes led to a collapse of the terrestrial ecosystem ~300 yr (120–480 yr; ± 2 s.d.) before the onset of the EPME and that this collapse induced euxinic conditions in the ocean, ultimately resulting in the demise of marine ecosystems.

Normative Mineralogy of 1170 Soil Profiles across Canada

Weathering of soil minerals provides base cations that buffer against acidity, and nutrients that support plant growth. In general, direct observations of soil minerals are rare; however, their abundance can be determined indirectly through soil geochemistry using normative-calculation procedures. This study compiled a data set of major oxide content from published and archived soil geochemical observations for 1170 sites across Canada (averaged over the soil profile [A, B, and C horizons], weighted by depth and bulk density to a maximum depth of 50 cm). Quantitative soil mineralogy (wt%) was systematically determined at each site using the normative method, ‘Analysis to Mineralogy’ (A2M); the efficacy of the approach was evaluated by comparison to X-ray Diffraction (XRD) mineralogy available for a subset of the study sites. At these sites, predicted A2M mineralogy was significantly related to estimated XRD, showing a strong linear relationship for plagioclase, quartz, and K-feldspar, and a moderate linear relationship for chlorite and muscovite. Further, the predicted A2M plagioclase content was almost identical to the estimated XRD soil mineralogy, showing no statistical difference. The Canada-wide predicted quantitative soil mineralogy was consistent with the underlying bedrock geology, such as in north-western Saskatchewan and north-eastern Alberta, which had high amounts of quartz due to the Western Canadian Sedimentary Basin. Other soil minerals (plagioclase, potassium feldspar, chlorite, and muscovite) varied greatly in response to changing bedrock geology across Canada. Normative approaches, such as A2M, provide a reliable approach for national-scale determination of quantitative soil mineralogy, which is essential for the assessment of soil weathering rates.

Soil–vegetation–water interactions controlling solute flow and chemical weathering in volcanic ash soils of the high Andes

Abstract. Vegetation plays a key role in the hydrological and biogeochemical cycles. It can influence soil water fluxes and transport, which are critical for chemical weathering and soil development. In this study, we investigated soil water balance and solute fluxes in two soil profiles with different vegetation types (cushion-forming plants vs. tussock grasses) in the high Ecuadorian Andes by measuring soil water content, flux, and solute concentrations and by modeling soil hydrology. We also analyzed the role of soil water balance in soil chemical weathering. The influence of vegetation on soil water balance and solute fluxes is restricted to the A horizon. Evapotranspiration is 1.7 times higher and deep drainage 3 times lower under cushion-forming plants than under tussock grass. Likewise, cushions transmit about 2-fold less water from the A to lower horizons. This is attributed to the higher soil water retention and saturated hydraulic conductivity associated with a shallower and coarser root system. Under cushion-forming plants, dissolved organic carbon (DOC) and metals (Al, Fe) are mobilized in the A horizon. Solute fluxes that can be related to plant nutrient uptake (Mg, Ca, K) decline with depth, as expected from biocycling of plant nutrients. Dissolved silica and bicarbonate are minimally influenced by vegetation and represent the largest contributions of solute fluxes. Soil chemical weathering is higher and constant with depth below tussock grasses but lower and declining with depth under cushion-forming plants. This difference in soil weathering is attributed mainly to the water fluxes. Our findings reveal that vegetation can modify soil properties in the uppermost horizon, altering the water balance, solute fluxes, and chemical weathering throughout the soil profile.

P-dipping improved NERICA 4 rice seedling resilience to water and nutrient stresses under rainfed-like conditions

Drought stress and phosphorus (P) deficiency are major abiotic factors that limit the yields of rice in Sub-Saharan Africa. To improve the available P supply in the highly weathered soils in the region, farmers use several P application methods, one of which is P-dipping, i.e., dipping the root of seedlings into P-enriched slurry before transplanting. In this study, a split-plot pot experiment was conducted to determine how the effect of localized P application via P-dipping (using four P fertilizer levels) on NERICA 4 rice growth interacts with two water regimes (waterlogging and moderately dry). Shoot dry weight and plant height differed significantly under the various P-dipping application levels, with an application of 40 kg P ha−1 providing the highest mean values under both water treatments. While the mean leaf area did not statistically differ among the P-dipping treatment levels under the moderately dry condition, all P-dipping treatments had increased leaf area relative to that observed without P-dipping. Mean root length differed significantly between the water treatments, whereas the mean root dry weight was higher with the P-dipping treatments than without P-dipping under both water conditions (36% and 8% mean increases under the waterlogged and moderately dry treatments, respectively). These findings show that P-dipping improves the ability of NERICA 4 rice seedlings to withstand water and nutrient stresses under rainfed lowland at early growth stages.

Elemental Behavior during Weathering and Pedogenesis of Clay-Rich Red Soils Developed in Different Lithologies in Java–Madura and Sulawesi in Indonesia

Clay-rich red soil profiles developed in different lithologies in Indonesia were assessed using geochemical evidence, the migration coefficient and elemental ratios. Our study aimed to ascertain the source of red soil materials and to investigate the elemental behavior in tropical soils. The results indicate carbonate profiles were derived from in situ weathering, while basalt profiles, even though having close affinity to their bedrock, also showed the contribution of external materials. Elemental behavior was dynamic with carbonate profiles indicating relatively constant depletion and even distribution. Basalt profiles indicated uneven distribution with enrichment and depletion. The variation in elemental behavior was linked to difference in lithologies, age and physiochemical conditions. Our findings support evidence of both residual and multiple source parent materials in red soil formation and provide insights into elemental behavior during weathering, while highlighting the influence of external materials’ contribution in deeply weathered tropical soils.

Pedochemical behaviors of rare earth elements in soil profiles along a lithosequence in eastern Taiwan

The composition and concentration of rare earth elements (REEs) in soil are primarily dependent on the lithology of parent materials. The different association preferences among individual REE and soil solid phases also cause REEs fractionation during pedogenetic processes. However, studies on the interaction between lithology and pedogenesis, affecting the geochemical behaviors of REEs, are lacking. Thus, this study elucidated the influence of parent materials on REEs concentration and distribution during pedogenesis in four pedons along a lithosequence covering schist, andesite, shale, and mafic rocks identified in eastern Taiwan. The highest ΣREEs was observed in the schist pedon (253–319 mg kg−1), followed by the andesite pedon (239–277 mg kg−1), mafic pedon (243–254 mg kg−1), and shale pedon (195–222 mg kg−1). Moreover, REE patterns and ratios of light REEs (LREEs) to heavy REEs (HREEs) indicated that soils derived from felsic rocks (schist and shale) tended to be rich in LREEs; conversely, soils derived from mafic rocks were rich in HREEs. HREEs decreased with an increase of Si, but values of REEs fractionation proxies (LaN/YbN and LaN/SmN) increased with increasing Si. The mass transfer coefficients (τ) of REEs, LREEs, and HREEs exhibited a significant correlation with LaN/SmN. Compared with LREEs, HREEs exhibited a greater depletion and contribution in REEs fractionation in the studied pedons, as evaluated based on τHREEs, w and its correlation with LaN/SmN and GdN/YbN. The relatively high mobility of HREEs, coupled with the clear illuviation, resulted in decreased values of LaN/SmN and GdN/YbN along with the increasing degree of soil weathering. This study elucidated the shift in the factors controlling the REEs fractionation from the lithologic characteristics of parent materials to the pedogenesis, along with the progressed soil development. Additionally, the increasing degree of soil weathering can be quantified using the ratios of LaN/SmN and GdN/YbN.

Phosphorus-Solubilizing Microorganisms: A Key to Sustainable Agriculture

Phosphorus (P) is one of the essential macronutrients for plant growth, being a highly required resource to improve the productive performance of several crops, especially in highly weathered soils. However, a large part of the nutrients applied in the form of fertilizers becomes “inert” in the medium term and cannot be assimilated by plants. Rationalizing the use of phosphorus is a matter of extreme importance for environmental sustainability and socioeconomic development. Therefore, alternatives to the management of this nutrient are needed, and the use of P-solubilizing microorganisms is an option to optimize its use by crops, allowing the exploration of less available fractions of the nutrient in soils and reducing the demand for phosphate fertilizers. The objective of this study is to discuss the importance of phosphorus and how microorganisms can intermediate its sustainable use in agriculture. In this review study, we present several studies about the role of microorganisms as phosphorus mobilizers in the soil. We describe the importance of the nutrient for the plants and the main problems related to the unsustainable exploitation of its natural reserves and the use of chemical fertilizers. Mainly we highlight how microorganisms constitute a fundamental resource for the release of the inert portion of the nutrient, where we describe several mechanisms of solubilization and mineralization. We also discussed the benefits that the inoculation of P-solubilizing microorganisms provides to crops as well as practices of using them as bioinoculants. The use of microorganisms as inoculants is a viable resource for the future of sustainable agriculture, mainly because its application can significantly reduce the application of P and, consequently, reduce the exploitation of phosphorus and its reserves. In addition, new research must be conducted for the development of new technologies, prospecting new biological products, and improvement of management practices that allow for higher efficiency in the use of phosphorus in agriculture.

Fluoride Contamination, Toxicity and its Potential Therapeutic Agents

Fluoride is the thirteenth most abundant element in the earth’s crust. It is highly electronegative and distributed ubiquitously in nature. During weathering of rocks and soil, fluoride can leach out and dissolve in the groundwater. Both plants and animals are exposed to several compounds of fluoride through contaminated soil and water. Fluoride contamination in groundwater is a major global concern as groundwater is frequently used for drinking in various parts of the world, especially in developing countries. Fluoride compounds have been reported to impose acute and chronic health hazards. Millions of global populations are suffering from dental and skeletal fluorosis due to high fluoride intake through drinking water. In green vegetation, fluoride accumulation causes necrosis in the tip and marginal portions of leaves. Diverse detrimental effects of fluoride on health have insisted researchers globally to identify compounds having protective potential against fluoride toxicity. Several plant extracts, vitamins, polyphenols, melatonin, hypophyseal proteins, and lycopene have been demonstrated to enhance the antioxidant status and subvert fluoride-induced health hazards in model organisms. However, more studies are required to forward conclusive opinions in terms of the real-life efficacy of these antioxidants against fluoride toxicity.

Development and application of new transfer functions between climate and soil weathering indices for paleoclimatic reconstructions from Chinese loess-paleosol sections

The degree of weathering and soil formation under similar conditions with respect to parent material, relief position, vegetation, and age mainly depends on the climatic conditions. Therefore, various weathering indices have been used successfully to reconstruct past mean annual temperature (MAT) and mean annual precipitation (MAP) based on the expression of these weathering indices in paleosols. Yet, no specific soil-climate transfer function has been established to reconstruct paleoclimates based on paleosols in Chinese loess profiles. In this study, we analyzed the relationships between several weathering indices and present climatic conditions for 49 soils throughout different climate zones in China (21°42′–47°54′ N), which were all developed in loess or similar Quaternary silty sediments. We aimed to establish soil-climate transfer functions that can be widely applied to paleosol-based paleoenvironmental reconstructions in Chinese loess archives and to apply them to a pedosedimentary record in northeastern China, where paleoclimatic information is still scarce.Overall, MAT showed the strongest relationship with the weathering index ba1 ((K2O + Na2O)/Al2O3), with MAT = –29.887 ba1 + 22.361 (R2 = 0.788), and MAP showed the closest relationship with the Chemical Proxy of Alteration (CPA: Al2O3 × 100/(Al2O3 + Na2O)), with MAP = 0.0843 CPA3 – 20.143 CPA2 + 1630.7 CPA – 44,244 (R2 = 0.898). We applied these two transfer functions to a Late-Pleistocene pedosedimentary record in Shenyang, Liaoning Province, to reconstruct MAT and MAP from the onset of the Last Glacial Period until the Last Glacial Maximum. Our reconstruction yielded a warm-humid climate until the Marine Isotope Stage (MIS) 5/4 transition and a trend towards a cooler and drier climate thereafter, interrupted by a somewhat warmer and more humid period during MIS 3. Despite several limitations, the newly established transfer functions can be applied to paleosols in loess-paleosol sections across the Chinese monsoon region and other regions around the world whose climates and parent materials are within the range covered by this study, because of the large supra-regional distribution of the soils included in this study. Thus, the new functions provide a new valuable tool for obtaining a substantial set of new paleoclimatic proxy data for various loess regions.

The evolution of soil microstructure and micromineralogy along a soil age gradient on the Galápagos Islands (Ecuador)

The islands of the Galápagos archipelago are of different ages due to the combination of a geostationary volcanic hotspot and the eastward movement of the Nazca tectonic plate. Taking advantage of this, a soil chronosequence (1.5–1070 ka) has recently been established covering four of the islands. This was used to investigate the temporal development of soil microstructure and micromineralogy using micromorphological methods in combination with synchrotron-based mineralogical and geochemical microanalyses. Along the chronosequence, the microstructure changed from intergrain microaggregates in the young soils to angular blocky microaggregates in the older soils. In the young soils, a high amount of vitric scoria and weatherable minerals occur, but they quickly disappear with age, and micromass increased fast. The micromorphological studies as well as micro-XRD and micro-XRF revealed increasing heterogeneity of soil microstructure and micromineralogy due to weathering and pedogenic processes until intermediate soil age. In the oldest soils, the microstructure became more uniform again, de-mixing pedofeatures like clay coatings have completely disappeared, and kaolinite, hematite and gibbsite dominate the mineralogical composition. Our study shows that the development of soil microstructure mirrors macroscopic soil profile development showing increasing differentiation until intermediate developmental stages and receding heterogeneity in highly weathered soils.

Determination of Uranium Concentrations and 234U/238U Isotopic Ratios in Plants and the Groundwater Used in Their Cultivation in an Area with High Background Radiation

The weathering of rocks and soil causes uranium to collect in groundwater. In this article, we attempted to assess the activity concentrations of uranium and 234U/238U isotopic ratios in various groundwater samples and plants obtained from the Ha’il region, Saudi Arabia. The results showed that the concentrations of 238U ranged between 0.08 ± 0.04 and 1.11 ± 0.06 Bq L−1, with an average of 0.67 ± 0.05 Bq L−1. Activity concentrations of 234U ranged between 0.12 ± 0.01 and 2.2 ± 0.8 Bq L−1, with an average of 1.26 ± 0.11 Bq L−1. The international permissible limit of uranium in groundwater is 0.372 Bq L−1. The 234U/238U activity ratios in the collected groundwater samples ranged between 1.5 ± 0.09 and 2.49 ± 1.27 Bq L−1, with an average of 1.95 ± 0.52 Bq L−1. In fruit-bearing trees, the 234U/238U activity ratios were 1.57 ± 0.84, 2.58 ± 1.01, and 2.69 ± 0.95 Bq L−1 for lemon, fig, and narenj. In fruit-bearing shrubs, the 234U/238U activity ratios were 2.37± 0.69 and 2.68 ± 0.69 Bq L−1 for green pepper and eggplant. Our goal is to increase the understanding of the factors that govern uranium’s activity and isotopic composition to better understand its prospective utilization as a tracer in groundwater chemistry and hydrology, as well as the possibility of exploiting this area for irrigation. In this investigation area, the groundwater and plants were unfit for human consumption.

Co-Composted Chicken Litter Biochar Increases Soil Nutrient Availability and Yield of Oryza sativa L.

Intensified cultivation of rice has accelerated weathering of most tropical acid soils leading to significant loss of base cations. In most developing countries, rice yield is low and this results in its production being costly because productivity versus labor is low. The objectives of this study were to (i) enhance soil chemical properties, nutrient uptake, and grain yield of rice grown on a mineral tropical acid soil using agro-wastes; (ii) determine the agro-waste (chicken manure, cow dung, forest litter, and Leucaena) that has the potential to significantly increase rice yield; and (iii) determine the residual effects of the organic soil amendments produced from the agro-wastes on soil and rice productivity. The treatments used in this three-cycle field study were (i) soil without amendments (S0); (ii) prevailing recommended rates for fertilizers (NPK-Mg); (iii) biochar–forest litter compost (OSA1); (iv) biochar–chicken litter compost (OSA2); (v) biochar–cow dung compost (OSA3); (vi) biochar–Leucaena compost (OSA4); and (vii) biochar–Leucaena–chicken litter compost (OSA5). Standard procedures were used to determine the plants’ rice growth, grain yield, plant nutrient concentrations and uptake, and selected soil chemical properties. The use of organic soil amendments (OSA1 to OSA5) significantly improved the soil chemical properties, rice plant growth, nutrient uptake, and grain yield compared with the prevailing method of cultivating rice (NPK-Mg). The application of organic soil amendments reduced the use of inorganic N, P, K, MgO, and trace elements fertilizers up to 25%, 100%, 64%, 100%, and 100%, respectively. The organic soil amendments with Leucaena significantly increased rice grain yield of OSA5 at 11.17, 13.11, and 10.06 t ha−1 in the first, second, and third cropping cycles, respectively. The residual effect of the organic soil amendments also improved rice plant growth, nutrient uptake, and rice grain yield although these were slightly reduced as compared to those of the two previous cropping cycles, the afore-stated treatments were superior to the prevailing method of cultivating rice (NPK-Mg). Transforming agro-wastes into organic soil amendments can improve tropical mineral acid soils and rice productivity.

Water quality assessment and pollution source apportionment using multivariate statistical techniques: a case study of the Laixi River Basin, China.

Identifying potential sources of pollution in tributaries and determining their contribution rates are critical to the treatment of water pollution in main streams. In this paper, we conducted a multivariate statistical analysis on the water quality data of 12 parameters for 3years (2018-2020) at six sampling sites in the Laixi River to qualitatively identify potential pollution sources and quantitatively calculate the contribution rates to reveal the tributaries' pollution status. Spatio-temporal cluster analysis (CA) divided 12months into two parts, corresponding to the lightly polluted season (LPS) and highly polluted season (HPS), and six sampling sites were divided into two regions, corresponding to the lightly polluted region (LPR) and highly polluted region (HPR). Principal component analysis (PCA) was used to determine the potential sources of contamination, identifying four and three potential factors in the LPS and HPS, respectively. The absolute principal component score-multiple linear regression (APCS-MLR) receptor model quantitatively analyzed the contribution rates of identified pollution sources, and the importance of the different pollution sources in LPS can be ranked as domestic sewage and industrial wastewater and breeding pollution (33.80%) > soil weathering (29.02%) > agricultural activities (20.95%) > natural influence (13.03%). HPS can be classified as agricultural cultivation (41.23%), domestic sewage and industrial wastewater and animal waste (33.19%), and natural variations (21.43%). Four potential sources were identified in LPR ranked as rural domestic sewage (31.01%) > agricultural pollution (26.82%) > industrial effluents and free-range livestock and poultry pollution (25.13%) > natural influence (14.82%). Three identified latent pollution sources in HPR were municipal sewage and industrial effluents (37.96%) > agricultural nonpoint sources and livestock and poultry wastewater (33.55%) > natural sources (25.23%). Using multivariate statistical tools to identify and quantify potential pollution sources, managers may be able to enhance water quality in tributary watersheds and develop future management plans.