Anthropogenic Soil Research Articles

Enhancement of the Aroma Compound 2-Acetyl-1-pyrroline in Thai Jasmine Rice (Oryza sativa) by Rhizobacteria under Salt Stress.

Simple SummaryThe major aroma compound (2-acetyl-1-pyrroline) of the world-famous Thai jasmine rice, variety KDML105, has declined due to high soil salinity and agrochemical input. In this work, the rhizobacteria from rice were investigated for the aroma compound’s production, as well as their potential for increasing the compound content in Thai jasmine rice seedlings under saline conditions. Our results provide evidence that the addition of aroma compound-producing rhizobacteria increases the aroma content in the rice seedlings under salt stress. Sinomonas sp. strain ORF15-23 which colonize the rice roots, is a promising rhizobacteria in promoting the aroma level of the Thai jasmine rice grown under salt stress and could be developed as a bioinoculant for Thai jasmine rice cultivation in a salt-affected area.Thai jasmine rice (Oryza sativa L. KDML105), particularly from inland salt-affected areas in Thailand, is both domestically and globally valued for its unique aroma and high grain quality. The key aroma compound, 2-acetyl-1-pyrroline (2AP), has undergone a gradual degradation due to anthropogenic soil salinization driven by excessive chemical input and climate change. Here, we propose a cheaper and an ecofriendly solution to improve the 2AP levels, based on the application of plant growth-promoting rhizobacteria (PGPR). In the present study, nine PGPR isolates from rice rhizosphere were investigated for the 2AP production in liquid culture and the promotion potential for 2AP content in KDML105 rice seedlings under four NaCl concentrations (0, 50, 100, and 150 mM NaCl). The inoculation of 2AP-producing rhizobacteria resulted in an increase in 2AP content in rice seedling leaves with the maximum enhancement from Sinomonas sp. ORF15-23 at 50 mM NaCl (19.6 µg·kg−1), corresponding to a 90.2% increase as compared to the control. Scanning electron microscopy confirmed the colonization of Sinomonas sp. ORF15-23 in the roots of salinity-stressed KDML105 seedlings. Our results provide evidence that Sinomonas sp. ORF15-23 could be a promising PGPR isolate in promoting aroma level of Thai jasmine rice KDML105 under salt stress.

Times are changing: A new chronology for Holocene volcanic events and hydro-sedimentary history recorded in the Sarliève marsh (central France)

This paper presents the first well-dated palaeoenvironmental study from the Sarliève marsh, a unique sedimentary record in the Limagne plain of central France, where all previous studies suffered from unreliable chronologies. We developed an accurate radiocarbon-based age-depth model and performed high-resolution multi-proxy sedimentological and geochemical analysis on a new sediment core from the heart of the sedimentary basin, improving the chronology and Holocene palaeoenvironmental interpretations. We found six potential (crypto)tephra fallouts (c. 9750, 8500, 7500, 7400, 6300, and 5800 cal yr BP) that enrich the Holocene tephrostratigraphy in Limagne, five of which were not previously documented in the sediments of the marsh. We also detected, for the first time, an array of volcanic phenomena such as degassing episodes (c. 6950 and 6050 cal yr BP), ash leaching phases (10250–9750, 8500–7400, and 5800–5100 cal yr BP), and earthquakes (c. 6800, 6600, 6050, 6100, and 1600 cal yr BP), suggesting a hitherto unsuspected period of high volcanic activity in the area between 7500 and 5800 cal yr BP. This increased activity appears to have caused a massive forcing of hydrosedimentary dynamics in the catchment in the Middle Holocene, by supplying significant volumes of fine volcanic ash to the palustrine basin, and thereby questioning the current Holocene morpho-sedimentary narrative for Limagne. The basin became a permanent freshwater lake after the Mid-Holocene climatic shift, and detrital influxes likely due to anthropogenic soil erosion appeared c. 5500 cal yr BP and grew steadily after 5000 cal yr BP, with a marked lull between 3600 and 3000 cal yr BP, perhaps because of a phase of settlement abandonments during the middle and early-late Bronze age. A series of lacustrine low-stands (c. 4750–4600, 3750–3600, 3350–3200 and 2950–2800 cal yr BP) that correlate strongly with western alpine lake records do not seem to have caused significant changes in the anthropogenic impact on soils modifying the sedimentary supply. Our results suggest that this lake could have been artificially drained c. 2550 cal yr BP, several centuries earlier than previously estimated, allowing us to hypothesize that Early Iron age societies already had substantial capacity to modify the hydraulic environment. Hydromorphic conditions developed thereafter, including complex short-lived marshy phases in late Roman times.

Geotechnical and Environmental Assessment of Blast Furnace Slag for Engineering Applications.

The increasing demand for building materials in the road industry creates interest for a new source of high-quality aggregates. In order to conserve natural resources, more attention is focused on anthropogenic soils and industrial solid wastes. For the successful application of these types of soil, a series of geotechnical and environmental tests have to be conducted. A potential hazard in the reuse of wastes from thermal degradation in the construction industry, particularly in reinforced concrete (RC) construction, is the migration of heavy metals into the groundwater environment. In this article, a geotechnical assessment of blast furnace slag (BFS) properties is presented. We conducted a series of CBR, and oedometric tests to evaluate the feasibility of BFS application in earth construction. The oedometric test results show acceptable compression characteristics which are in the range of natural aggregates. The CBR shows that this material may be used as a pavement subbase. We also noticed the preconsolidation pressure phenomenon in both Proctor and vibro-compacted soil during the oedometric test. The compression index and recompression index value show that the compression characteristics are close to those of dense sand. Based on the results described in the article, blast furnace slag is a candidate for technological application and can become one of the elements of sustainable development by contributing to a reduction in the negative environmental impact of production and use of building materials.

Features of soils and soil formation of natural monument «Park «Sergievka»» (Saint Petersburg, Russia)

Parks maintain crucial ecological functions and provide different benefits for city dwellers. These facts made studying of park ecosystems important task. Soil cover and patterns of its formation were studied in natural monument “Park “Sergievka” (Saint Petersburg). The structure and composition of the soil cover of the park depend mainly on relief, groundwater level and features of soil-forming materials. The soil cover of the park “Sergievka” is characterized by taxonomic diversity, complexity and heterogeneity. Natural soils occupy 75% of the park area. Gleysols and Fluvisols dominated on the modern marine terrace, Umbric and Histic Gleysols are typical for the first terrace, and Retisols are the most abundant soils of the second terrace. Urbic Technosols were found near buildings, ponds and along the highway. Terric Anthrosols occur on the Lower Meadow in front of the Palace. Despite the presence of artefacts and higher humus content, anthropogenic soils have acidic reaction and redoximorphic features typical for native soils of the park territory. The results of the study indicate the dominance of natural soil formation processes in the park due to absence of measures aimed at maintaining the effect of earlier work on soil drainage and cultivation.

Assessment and forecast of changes in the soil cover of anthropogenically transformed landscapes

Changes in the soil and soil cover under various types of anthropogenic impact are described. Trends of the development of anthropogenically transformed and anthropogenic soil cover patterns that occur in the Northwest of Russia have been studied. Transforming soils, intercomponent links, and natural factors of soil cover differentiation, humans either change their characteristics while maintaining the major trend or open a new branch of the land cover evolution.

Оценка масштабов ландшафтных пожаров 2020 года на территории России

Landscape fires are one of the main factors of anthropogenic vegetation and soil transformation, as well as anthropogenic climate change. Despite this, until now there have been no detailed estimates of the scale of all types of landscape fires throughout Russia for a full calendar year. This work was aimed at providing such an assessment for landscape fires in 2020, as well as creating a publicly available map of these fires. The fires were mapped by experts and specially trained volunteers on the basis of Sentinel-2 MSI medium spatial resolution satellite images (20 m/pixel) for two periods — from January 1 to May 15, and from May 16 to December 31 inclusive. The total area of identified landscape fires was 25.84 million hectares. The division of the identified fires into presumably controlled (prescribed burning) and uncontrolled (actually fires) was not carried out within the framework of this work. However, the burned areas, corresponding to the area criterion established for single prescribed burnings (up to 10 hectares), account for only 0.96% of the total area of detected fires. The final map of landscape fires, compiled as a result of this work, is available in the public domain at https://maps.greenpeace.org/maps/gpru/fires_2020.

Ancient anthropogenic soils and activity areas of the Colombian Andean region: A geoarchaeological approach

AbstractThe Monte Azul archaeological site is located in the inter‐Andean Aburrá Valley of the upper Medellín River in Colombia and it is dated from the Middle Ceramic period to the Republican period. In this study area, it is common to find evidence of disturbed soils that is related to ancient use and erosion. In Monte Azul, the pedogenesis is associated with the presence of fast‐weathering eolian volcanic ash deposits, extreme acidity, low base saturation, strong leaching, high precipitation, and high temperature; hence, some of these tropical conditions are responsible for the low conservation of the archaeological record. Consequently, we used a geoarchaeological approach with paleoenvironmental, sedimentary, geochemical, and soil micromorphological proxies as integral units of analysis to understand site formation processes. Micromorphological and paleobotanical records indicate soil use dynamics and changes in paleoenvironmental conditions from humid conditions to small and persistent clearings around a domestic unit. This approach sheds light on the development of possible pre‐Hispanic activity areas and cultivation techniques related to the ancient use of the Ferrería pottery style in the Central Mountain Range of Colombia.

Role of arbuscular mycorrhizal symbiosis in remediation of anthropogenic soil pollution

Agricultural and industrial activity generates high concentrations of organic and inorganic pollutants, many of which are incorporated into the trophic chain, affecting ecosystems. There are several strategies for the remediation of polluted areas; we discuss one of them in the present review that shows the successful evidence of the use of arbuscular mycorrhizal symbiosis in phytoextraction (the removal of contaminants from soil and water sources with mycorrhizal plants), and in the process of phytostabilization (the reduction of the mobility of heavy metals in soil by mycorrhizal roots, absorption onto roots, or precipitation within the root zone). Mechanisms of action of arbuscular mycorrhizal fungi (AMF) including, altered uptake and distribution of heavy metals, improvement in the mineral nutrition and water availability, protection against oxidative stress and increment in the physical stability of the soil by producing glomalin has been discussed with reference to heavy metals (HMs) and persistent oxidative pollutants (POPs). We report plant species associated with species of mycorrhizal fungi as strategy for phytostabilizing heavy metals and reducing biotranslocation to the aerial parts of plants.

Soils of Ancient Agricultural Terraces of the Eastern Caucasus

The morphological and chemical properties and biological activity of soils on ancient agricultural terraces in the middle-high mountains of the Eastern Caucasus are considered. The studied terraces were constructed on sandstone, limestone, clay shale, and colluvium of clay and sandstone. The properties of soils formed on these terraces are determined by the properties of soil-forming rocks, as well as by the duration and intensity of human activity. The more favorable for agricultural development the initial soils, the longer and stronger their anthropogenic transformation. Diagnostic features inherent to all lithological varieties of mountainous anthropogenic soils of the Eastern Caucasus and features characteristic of soils developed on the particular types of soil-forming rocks have been identified. The most important diagnostic feature of the soil cover on agricultural terraces is the regular replacement of agrolithozems in the rear parts of the terraces with dark-humus stratozems in their front parts, near the terrace brows. Also, a common diagnostic feature for all soils of terraces is the presence of gravels (up to 3–5 cm in size) evenly distributed throughout the arable layer. Additions to the classification system of Russian soils have been proposed. The soils of human-made agricultural terraces should be classified as a new subtype in the type of stratozems. The proposed subtype name—agristratified soil (or Terrasozem)—reflects the mechanism of the development of stratified soil thickness, i.e., the long-term agricultural impact (agristratified soil, ast). The results of our study can be used in the assessment of the potential for agricultural use of soils in the Eastern Caucasus.

The influence of ancient herders on soil development at Luxmanda, Mbulu Plateau, Tanzania

In eastern Africa, ecologists have found that when mobile pastoralists abandon their temporary encampments, the accumulation of burned animal dung, wood, and other organic waste enriches the concentration of nutrients (e.g., calcium, phosphorous, magnesium) essential to soil health, in comparison to other soils without prior human habitation. These nutrient-enriched soils promote glade development and greater biodiversity. Geoarchaeological research on the time depth of this anthropogenic “nutrient hotspot” phenomenon has demonstrated that soils at several archaeological sites in southern Kenya still remain enriched in these soil macro- and micro- nutrients after several thousand years. However, soil scientists and geoarchaeologists do not yet understand how these anthropogenic soils vary over the extensive geographic conditions of eastern Africa. The discovery of a Pastoral Neolithic site (ca. 3000 BP) at Luxmanda on the Mbulu Plateau, Tanzania, provides an opportunity to examine if similar patterns of nutrient enrichment can be detected in a different geological and climatic zone.In this paper, we use geochemical and sedimentary analyses to determine how archaeological soils at Luxmanda differ from adjacent off-site soils and known archaeological soils in Kenya, as well as from computationally derived soil nutrient models for eastern Africa. Our results indicate that soils derived from anthropogenic sediments and ashy dung are 4 to 16-fold more abundant in soil macro nutrients relative to off-site or modeled values. This pattern fits previous studies’ observations thatelevated macro- and micro-nutrients in soils are strongly correlated with ancient pastoralist habitation sites. We conclude that anthropogenic soils found at Pastoral Neolithic archaeological sites may be a valuable, but unappreciated, soil resource in eastern Africa.

Alaskan plants and their assembled rhizosphere communities vary in their responses to soil antimony

Arctic and subarctic soils are undergoing rapid changes that influence vegetation, bacteria, and their interactions with each other and the environment. Our objective was to understand how rhizosphere bacterial communities from diverse Alaskan boreal and tundra habitats and common Alaskan plant species interact with an anthropogenic soil stressor. A variety of soil types associated with plant communities from Interior and Arctic Alaska were selected. Soils were seeded with a forb, grass, or tree, spiked with antimony (Sb) or kept as a control, and grown for 60 days under warm conditions. Plant growth and Sb uptake, rhizosphere prokaryote composition, and mycorrhizal colonization data were collected. Antimony altered rhizosphere bacterial community richness, diversity, and composition, dependent on soil type and plant identity. Of 20 rhizosphere bacterial orders, Burkholderiales proved most responsive to Sb, but the responses varied by plant species. Plant species' uptake of Sb were strongly influenced by soil biological, chemical, and physical properties. Picea glauca (white spruce) accumulated hyperaccumulator-level Sb concentrations in its roots in 2 of 6 soils. Future biotechnology applications to mitigate land degradation in this environment must acknowledge the complex interactions between vegetation, soils, microbes, and climate for successful utilization.

Anthropogenic erosion-induced small-scale soil heterogeneity in South African rangelands

Land-use-induced soil erosion in semi-arid drylands induced by land-use changes creates patchworks of soils and vegetation different from those of natural conditions. Knowledge of the highly dynamic spatial heterogeneity in soil properties, not depicted in conventional soil maps, is important for managing land uses sustainably, and for understanding soil-climate interactions. This analysis of soil redistribution in a degraded rangeland in South Africa assessed the significance of anthropogenic soil heterogeneity within a small catchment with a silted reservoir. This study carries out analysis of soil redistribution in a degraded rangeland in South Africa, to assess the significance of anthropogenic soil heterogeneity within a small catchment with a silted-up reservoir. Surface soil (N = 51) and soil profile (N = 29) samples were collected from areas of various degrees of degradation and analysed for texture, pH, total nitrogen (TN), total organic carbon (TOC), available phosphorus (P), and potassium (K). Diverse vegetation cover is reflected in a high soil heterogeneity, showing differences in soil texture. Average surface soil nutrient content was significantly higher in vegetated areas (grassland: TOC 1.08 %, TN 0.10 %, P 20.12 mg kg −1 , mixed vegetation: TOC 0.93 %, TN 0.08 %, P 13.54 mg kg −1 , depositional: TOC 1.68 %, TN 0.18 %, P 34.67 mg kg −1 ) than at degraded sites (TOC 0.47 %, TN 0.06 %, P 7.52 mg kg −1 ). K content was low to moderate but did not show any significant difference between landscape units. Potential exists for the formation of distinct young anthropogenic soils on the silted-up reservoir where deposited sediments differed in TOC, TN, P, and profile depth from the shallow natural soils. Consequently, azonal soils on dam-deposits are different from those occurring naturally, and not depicted on conventional soil maps. Their different water and nutrient cycling may affect vegetation and biogeochemical fluxes. Land-use management should consider such soils, as they play an important role in rangeland ecology.

Geoarchaeological signatures of anthropogenic soils in southeastern Uruguay: Approaches to formation processes and spatial–temporal variability

AbstractThis contribution focuses on the interpretation of earthen mound formation processes in the lowlands of the Pampa biome, southeastern Uruguay, through the integrated analysis of sedimentological and archaeological data. The three analyzed mounds from the La Tapera site have different heights and radiocarbon chronologies, indicating different construction periods across the last 4000 years. In addition, soils from surrounding plains were analyzed to provide a comparative basis for geoarchaeological characterization. From granulometric, compositional, and geochemical results, we identified different soil classes and several anthropogenic layers inside the earthen structures. Mound soils stood out from the rest due to higher levels of P, soil organic matter (SOM), and micro‐artifact content, leading to their classification as hortic Anthroportic Udorthent soils or hortic‐cultural cumulic archaeo‐anthrosols. Geoarchaeological differences between mounds are inferred as variations in the formation processes and/or construction technologies, possibly related to the functionality and height of the structures. Evidence from this contribution demonstrated the existence of ancient ways to produce nutrient‐rich long‐lasting anthropogenic soils that left persistent geoarchaeological signatures on the landscape. These findings highlight the need to broaden the discussion, culturally and geographically, about the genesis and development of management practices and associated indigenous knowledge to include the lowlands of southeastern South America.

Seeing copiapósols: anthropogenic soils, strategic unknowing, and emergent taxonomies in northern Chile

In recent decades, anthropogenic soils have become so ubiquitous that for some authors they should be taken as the “golden spike” signaling the start of the Anthropocene. Despite their prominence, leading soil taxonomies have resisted calls to recognize them as a proper kind of soil. Such omission has importantly limited the ways in which soil practitioners can account and deal with the sociopolitical aspects embedded in soil formation. Approaching the issue from a sociomaterial perspective, this paper studies the effects of such omission on the work of soil scientists working in northern Chile. By contrasting their usage of the USDA/NRCS soil typology with the realities found in the field, the work of strategic unknowing that such typologies achieve becomes evident. To challenge such situation, the paper concludes exploring the notion of emergent taxonomies, classifications that are sensitive to local configurations of materials, living beings and power out which soils emerge.

Hydrochar from sugarcane industry by-products: assessment of its potential use as a soil conditioner by germination and growth of maize

BackgroundHydrothermal carbonization (HTC) is a thermochemical process to convert biomass in carbon-rich materials (hydrochar). The use of sugarcane industry by-products in HTC has been evaluated, generating a hydrochar rich in nutrients, which could be used as a soil conditioner. We raised the hypothesis that the application of hydrochar in soil can improve its nutrient characteristics, bringing a better environment and favouring plant growth, expecting a development similar to that one observed in anthropogenic soils.ResultsGermination studies were performed expecting a species-dependent response, using maize and tomato seeds, whose development was assessed in two soluble fractions obtained from hydrochar aiming to evaluate different rhizosphere conditions. The results showed a better development of maize, especially in the aqueous soluble fraction, whose nutrient concentration was lower than that of the acid soluble fraction, as well as the organic composition. Maize growth in soils showed a better initial development in ultisol compared to oxisol, this being inferred by root:shoot biomass ratio and by scanning electron microscopy (SEM) images. However, the development of maize was better in anthropogenic soil compared to soils that received hydrochar.ConclusionThe maize growth, compared with that carried out in anthropogenic soil, suggests that during the period evaluated the addition of hydrochar in soil did not have a negative effect upon maize development in its initial phase, and could have even favoured rooting in ultisol.

Land-use change and its impact on physical and mechanical properties of Archaeological Black Earth in the Amazon rainforest

The intense pressure of anthropic actions to change the use and management can promote the degradation of anthropogenic soils with high natural fertility and high content of organic matter such as the Archaeological Black Earths of the Brazilian Amazon. Therefore, this study aimed to quantify the impact of land use and occupation in the Amazon biome on the physical and mechanical properties of Archaeological Black Earth. The research was carried out in the municipality of Novo Aripuanã, in the south of Amazonas State (Brazil), in a Chromic, Pretic, Acrisol with native forest, pasture, and pigeon pea. The soil properties of bulk density, mean weighted diameter, soil resistance to penetration, macroporosity, microporosity, particle size distribution (sand, silt, and clay), water-dispersible clay, flocculation index, total organic carbon, and preconsolidation pressure were assessed in the 0.0–0.1 and 0.1–0.2 m soil layers. Archaeological black earth under native forest showed better soil structural properties such as greater macroporosity and lower bulk density and resistance to penetration. The conversion to other uses promotes soil compaction and increases the resistance to compression. However, the greatest negative impacts on soil properties occurred when the land-use change was for pasture than for pigeon pea. The pigeon pea crop promoted the increase of soil total organic carbon in the 0.0–0.1 m layer. The soil mechanical behavior showed a greater load-bearing capacity in the native forest area for the surface layer than the subsurface layer. The preconsolidation pressure allowed to determine that the pasture land-use has a greater occurrence of compaction and might suffer additional compaction if the applied pressures on the soil during grazing are larger than the higher limit of the confidence interval of load-bearing capacity models when compared to the pigeon pea land-use.

Soil Disturbance Affects Plant Productivity via Soil Microbial Community Shifts.

Recent advances in climate research have discovered that permafrost is particularly vulnerable to the changes occurring in the atmosphere and climate, especially in Alaska where 85% of the land is underlain by mostly discontinuous permafrost. As permafrost thaws, research has shown that natural and anthropogenic soil disturbance causes microbial communities to undergo shifts in membership composition and biomass, as well as in functional diversity. Boreal forests are home to many plants that are integral to the subsistence diets of many Alaska Native communities. Yet, it is unclear how the observed shifts in soil microbes can affect above ground plant communities that are relied on as a major source of food. In this study, we tested the hypothesis that microbial communities associated with permafrost thaw affect plant productivity by growing five plant species found in Boreal forests and Tundra ecosystems, including low-bush cranberry and bog blueberry, with microbial communities from the active layer soils of a permafrost thaw gradient. We found that plant productivity was significantly affected by the microbial soil inoculants. Plants inoculated with communities from above thawing permafrost showed decreased productivity compared to plants inoculated with microbes from undisturbed soils. We used metagenomic sequencing to determine that microbial communities from disturbed soils above thawing permafrost differ in taxonomy from microbial communities in undisturbed soils above intact permafrost. The combination of these results indicates that a decrease in plant productivity can be linked to soil disturbance driven changes in microbial community membership and abundance. These data contribute to an understanding of how microbial communities can be affected by soil disturbance and climate change, and how those community shifts can further influence plant productivity in Boreal forests and more broadly, ecosystem health.

Processos de formação e processos antrópicos no abrigo de Itapeva/SP

O estudo da micromorfologia do solo é uma ferramenta útil para detectar materiais arqueológicos que os arqueólogos não conseguem avistar nas escavações. O objetivo deste artigo é revelar vestígios de ocupação humana a partir de uma análise micromorfológica. Os resultados são derivados da produção de seções delgadas que descrevem materiais de duas áreas diferentes do sitio, denominadas unidades de escavação D18 e G6, referentes às áreas norte e sul, e apontam para a existência de um solo antropogênico com formação de fogueiras. Conclui-se que o sedimento formado é uma mistura de areia, cinza, madeira e argila, que foi depositado em longos períodos e é derivado da ocupação humana e da deposição natural.

Arsenic speciation in titanium dioxide (TiO2) waste produced via drinking water filtration: Potential environmental implications for soils, sediments, and human health

Arsenic (As) contamination in soil and water is a global human health and environmental problem due to its common occurrence and high toxicity. At least four million people in Latin America have long-term exposure to As in drinking water. In northwestern Costa Rica, As has been measured in drinking water at concentrations ranging from 20 to over 80 µg As L−1. Arsenic contaminated drinking water can be treated using filter technologies; titanium dioxide (TiO2)-based drinking water filters decrease As concentration and help mitigate As exposure. However, this process creates an As-enriched TiO2 solid-phase waste product. An objective of this study is to determine the chemical forms of As in this waste product, which is commonly distributed on soil surfaces and throughout urban and rural areas adjacent to drinking water treatment facilities in the sample area. An additional objective is to determine biogeochemical changes in As speciation in filter waste and affected soils which may be induced through earthworm ingestion, which also occurs in the sample area. Arsenic concentrations in the solid-phase filter waste were measured to be up to 600 mg kg−1. There was a strong correlation between As and Ti (R2 > 0.90) indicating As accumulates within or on the surface of the TiO2 mineral. Earthworm castings enriched in TiO2 contained up to 530 mg As kg−1, which provided direct evidence soil macroorganisms ingest filter waste. X-ray diffraction (XRD) confirmed Ti is predominantly anatase with minor amounts of quartz and feldspar. These results are novel and innovative because they identify and characterize a previously unexplored problem of anthropogenic soil and sediment As contamination and redistribution in urban and rural environments. Additionally, dry windy seasons in the region increase potential risk of As and TiO2 exposure through dust inhalation. Earthworm consumption did not decrease As concentrations in earthworm castings. Synchrotron-based X-ray absorption spectroscopy (XAS), specifically X-ray absorption near edge structure (XANES) spectroscopy, indicated the dominant species of As in soil and sediment samples was arsenate [As(V)], which is similar to the chemical form of As in the groundwaters of this region. No evidence of arsenite [As(III)] was identified in any of the solid-phase samples, including earthworm castings.

Soils in ancient irrigated agricultural terraces in the Atacama Desert, Chile

AbstractThe Atacama Desert is among the driest places on Earth, yet ancient agricultural systems are present in the region. Here, we present a study of terraced agricultural soils in the high‐altitude eastern margin of the Atacama Desert in northern Chile, mainly dating to the Late Intermediate Period (ca. 950–1400 AD) and Inka period (ca. 1400–1536 AD). Terraced fields were compartmentalized to distribute limited irrigation water originating mainly from springs. Natural soils used for agriculture are mostly Aridisols developed on Pleistocene alluvial fan terraces and hillslopes underlain by volcanic bedrock. One research objective is to evaluate long‐term soil change from agriculture. In this hyperarid climate, agriculture is only possible with irrigation, so natural soils on the same geomorphic surface adjacent to irrigated soils provide baseline data for assessing anthropogenic soil change. Data from soil profiles and surface transects indicate intentional soil change through terracing, removal of soil rock fragments, and probable fertilization. Agricultural soils have anthropogenic horizons ranging from 16 to 54 cm thick. Most agricultural soils have higher phosphorus levels, suggesting enrichment from fertilization. Changes in soil organic carbon and nitrogen are also evident. Unintentional anthropogenic soil change resulted from CaCO3 input through irrigation with calcareous spring water. Initial studies suggest that agriculture here was sustainable in the sense of conserving soils, and maintaining and possibly improving soil productivity over centuries.