Soil Parent Research Articles

Neonicotinoid insecticide residues in soil dust and associated parent soil in fields with a history of seed treatment use on crops in southwestern Ontario.

Using neonicotinoid insecticides as seed treatments is a common practice in field crop production. Exposure of nontarget organisms to neonicotinoids present in various environmental matrices is debated. In the present study, concentrations of neonicotinoid residues were measured in the top 5 cm of soil and overlying soil surface dust before planting in 25 commercial fields with a history of neonicotinoid seed treatment use in southwestern Ontario in 2013 and 2014 using liquid chromatography-electrospray ionization tandem mass spectrometry. The mean total concentrations were 3.05 ng/g and 47.84 ng/g in 2013 and 5.59 ng/g and 71.17 ng/g in 2014 for parent soil and soil surface dust, respectively. When surface and parent soil residues were compared the mean concentration in surface dust was 15.6-fold and 12.7-fold higher than that in parent soil in 2013 and 2014, respectively. Pooled over years, the surface dust to parent soil ratio was 13.7, with mean concentrations of 4.36 ng/g and 59.86 ng/g for parent soil and surface dust, respectively. The present study's results will contribute important knowledge about the role these residues may play in the overall risk assessment currently under way for the source, transport, and impact of neonicotinoid insecticide residues in a maize ecosystem.

Hydropedology and soil evolution in explaining the hydrological properties of recharge dams in arid zone environments

The effects of anthropogenic activities on soil evolution due to siltation and the impact on hydraulic properties of the vadose zone on the augmentation of the aquifer recharge are investigated for the Al-Khoud dam in Oman. Inside the dam reservoir and in areas adjacent to the embankment, downstream, 33 pedons (of depths between 1.5 and 2 m) were excavated and studied during 2011 and 2012. Soil analysis revealed that the subsoil’s physiochemical properties of the study area are continuously changing due to damming, i.e., alteration of the natural runoff, intensified sedimentation, and infiltration. Variation of hydropedological properties caused by the geotechnical construction is evident in a distinct vertical stratification of texture of accrued sediments and almost an order of magnitude drop in saturated hydraulic conductivity (K s ) of the dam bed. Correspondingly, spilling of ponded water over the dam crest occurs more frequent and therefore increases the potential hazards of flooding of the downstream recharge area. Some fine particles of the suspended load carried to the reservoir by the feeding wadi migrate vertically downward, driven by seepage, into the originally coarse matrix of the parent soil and cause clogging of large pores (with time, hard pans in the subsurface are developing) even without visible cake formation on the soil surface. Development of hard pans was also discovered in pedons at depths close to 1 m. This is attributed to presence of a pedogenic carbonate derived from the parent rock and formed by precipitation of dissolved salts due to a vertical upward moisture evaporation to a hot and dry bed surface during prevailing dry bed periods of dam operation. K s measured downstream of the dam was relatively high (6 m/day) and was three times higher than the average value inside the reservoir (2.1 m/day), ranging there between 0.01 and 3.96 m/day, but less than at the upstream site outside the reservoir.

Effect of Nano-SiO2 on the Geotechnical Properties of Cohesive Soil

With the reduction of available land resources, the construction of civil engineering structures is carried out on soft soil, which leads to the development of ground improvement techniques such as soil stabilization. This research is intended to study the effect of adding nano-SiO2 on soil engineering properties, especially the shear strength and the unconfined compression strength and maximum dry unit weight, using clayey soil with low liquid limit (CL). Nano-SiO2 was mixed with soil in three different percentages (i.e. 0.5, 0.7, 1.0 % by weight of the parent soil). The shear strength, unconfined compression strength and maximum dry unit weight of treated specimens were measured by direct shear test, unconfined compression test and compaction test. It was found that increase in nano-SiO2 content resulted in increase in the angle of internal friction, the cohesion, the unconfined compression strength and maximum dry unit weight of the clayey soil. Based on the obtained results, in order to reach the maximum increase in strength parameters, the optimum nano-SiO2 content occurs at 0.7 %.

Development of a Turbidity Prediction Methodology for Runoff–Erosion Models

Surface water bodies can be impaired by turbidity and excessive sediment loading due to urban development, construction activities, and agricultural practices. Turbidity has been considered as a proxy for evaluating water quality, aquatic habitat, and aesthetic impairments in surface waters. The US Environment Protection Agency (USEPA) has listed turbidity and sediment as major pollutants for construction site effluent. Recently proposed USEPA regulations for construction site runoff led to increased interest in methods to predict turbidity in runoff based on parameters that are more commonly predicted in runoff–erosion models. In this study, a turbidity prediction methodology that can be easily incorporated into existing runoff–erosion models has been developed using fractions of sand, silt, and clay plus suspended sediment concentration of eight parent soils from locations in Oklahoma and South Carolina, USA.

Predicting the mineral composition of dust aerosols – Part 1: Representing key processes

Abstract. Soil dust aerosols created by wind erosion are typically assigned globally uniform physical and chemical properties within Earth system models, despite known regional variations in the mineral content of the parent soil. Mineral composition of the aerosol particles is important to their interaction with climate, including shortwave absorption and radiative forcing, nucleation of cloud droplets and ice crystals, heterogeneous formation of sulfates and nitrates, and atmospheric processing of iron into bioavailable forms that increase the productivity of marine phytoplankton. Here, aerosol mineral composition is derived by extending a method that provides the composition of a wet-sieved soil. The extension accounts for measurements showing significant differences between the mineral fractions of the wet-sieved soil and the emitted aerosol concentration. For example, some phyllosilicate aerosols are more prevalent at silt sizes, even though they are nearly absent at these diameters in a soil whose aggregates are dispersed by wet sieving. We calculate the emitted mass of each mineral with respect to size by accounting for the disintegration of soil aggregates during wet sieving. These aggregates are emitted during mobilization and fragmentation of the original undispersed soil that is subject to wind erosion. The emitted aggregates are carried far downwind from their parent soil. The soil mineral fractions used to calculate the aggregates also include larger particles that are suspended only in the vicinity of the source. We calculate the emitted size distribution of these particles using a normalized distribution derived from aerosol measurements. In addition, a method is proposed for mixing minerals with small impurities composed of iron oxides. These mixtures are important for transporting iron far from the dust source, because pure iron oxides are more dense and vulnerable to gravitational removal than most minerals comprising dust aerosols. A limited comparison to measurements from North Africa shows that the model extensions result in better agreement, consistent with a more extensive comparison to global observations as well as measurements of elemental composition downwind of the Sahara, as described in companion articles.

Predicting the mineral composition of dust aerosols – Part 2: Model evaluation and identification of key processes with observations

Abstract. A global compilation of nearly sixty measurement studies is used to evaluate two methods of simulating the mineral composition of dust aerosols in an Earth system model. Both methods are based upon a Mean Mineralogical Table (MMT) that relates the soil mineral fractions to a global atlas of arid soil type. The Soil Mineral Fraction (SMF) method assumes that the aerosol mineral fractions match the fractions of the soil. The MMT is based upon soil measurements after wet sieving, a process that destroys aggregates of soil particles that would have been emitted from the original, undisturbed soil. The second method approximately reconstructs the emitted aggregates. This model is referred to as the Aerosol Mineral Fraction (AMF) method because the mineral fractions of the aerosols differ from those of the wet-sieved parent soil, partly due to reaggregation. The AMF method remedies some of the deficiencies of the SMF method in comparison to observations. Only the AMF method exhibits phyllosilicate mass at silt sizes, where they are abundant according to observations. In addition, the AMF quartz fraction of silt particles is in better agreement with measured values, in contrast to the overestimated SMF fraction. Measurements at distinct clay and silt particle sizes are shown to be more useful for evaluation of the models, in contrast to the sum over all particles sizes that is susceptible to compensating errors, as illustrated by the SMF experiment. Model errors suggest that allocation of the emitted silt fraction of each mineral into the corresponding transported size categories is an important remaining source of uncertainty. Evaluation of both models and the MMT is hindered by the limited number of size-resolved measurements of mineral content that sparsely sample aerosols from the major dust sources. The importance of climate processes dependent upon aerosol mineral composition shows the need for global and routine mineral measurements.

Water-Quality Assessment and Environmental Impact Minimization for Highway Construction in a Miningimpacted Watershed: The Beaver Creek Drainage

Beaver Creek, a tributary of the Blackwater River just north of Canaan Valley in northeastern West Virginia, runs parallel to the proposed alignment of a major four-lane highway called Appalachian Corridor H. Beaver Creek and many of its major tributaries are characterized by low pH, little alkalinity, and high levels of dissolved metals due to the geochemical characteristics of the soil's parent material and continuing impacts from past coal mining. During the planning phase of this road project, we identified two major environmental concerns: (1) our ability to predict and manage water-quality impairments that will likely result from the cuts and fills of new material, and (2) the legacy effects of mine refuse from historic coal mines. In the latter case, although many refuse sites are located outside the proposed highway's alignment, drainage from these sites will be intercepted by the highway's water-control structures. We (West Virginia University [WVU]) have collaborated with the West Virginia Division of Highways (WVDOH) to minimize construction-related impacts to Beaver Creek's water quality. More specifically, we have evaluated strategies by which water collection and conveyance structures can be integrated with passive water-remediation processes during the highway's design and construction. In March 2000, we began monitoring water quality in the Beaver Creek drainage. We measured physical, chemical, and biological indicators of water quality and present these data here to serve as a baseline for future comparisons. In general, the water in Beaver Creek was acidic with an average pH of 5.1 in its headwaters and 6.1 above its confluence with the Blackwater River. The water also carried little or no alkalinity. The untreated water seeping from mine-waste piles was highly acidic, with an average pH of 3.0, carried high levels of dissolved sulfate and iron, and featured excess acid-production capacity. After we identified the main sources of water-quality impairment—the locations of mine-waste piles and acidic seeps—we formulated preliminary recommendations for minimizing the impacts of highway construction on the Creek's water quality. For example, we recommended the implementation of acid-base accounting on the overburden that would be disturbed during construction. We also suggested special material-handling procedures. Based on our preliminary water-quality data, we recommended a series of passive treatment processes that could be incorporated into the road's design, construction, and operation. Future treatment decisions will be informed by our growing dataset. Further, because many sources of water-quality impairment are located within the basin but beyond the road's proposed alignment, efforts must be made to engage diverse stakeholders to leverage support for protecting and restoring the Beaver Creek watershed.

Barium in landscape components of the western Transbaikal region

Barium concentrations in parent materials, soils, and plants of the forest-steppe, steppe, and dry steppe landscapes of the Transbaikal region have been studied. The average concentration of this element in rocks and soils of this region exceeds its clarke by 1.8–2.1 times. A positive correlation between the contents of Ba in soils, soil-forming rocks, and plants has been found. The concentration of Ba in soils does not correlate with the soil pH and humus content. Distribution patterns of Ba in the soil profiles have been characterized. With respect to the coefficient of the biological uptake by plants, Ba is assigned to the group of low accumulation (0.55–0.65) for mineral soils and of strong accumulation (6.0) for alluvial bog soils. Average concentrations of Ba in the steppe, meadow, and cultivated vegetation of the region are 1.9–2.3 times higher in comparison with the average concentration of this element in plants of the continents. The biological migration of Ba is most active in meadow landscapes, whereas steppe landscapes are characterized by the least active biological migration of this element.

Influence of soil type on the properties of termite mound nests in Southern India

Termite mounds are conspicuous features in many tropical ecosystems. Their shape and soil physicochemical properties have been suggested to result from the termites ecological need to control the temperature and humidity within their nests and protect themselves from predators. This study aimed to determine the influence of the parent soil properties on the shape and soil physical and chemical properties of termite mounds. Termite mounds built by the fungus-growing termite species Odontotermes obesus were compared in two forests with different soil properties (Ferralsol or Luvisol) in Southern India. Our findings confirm that soil properties influence the physicochemical characteristics of mound material and may affect the shape, but these impacts are mostly independent of the size of the mounds (i.e., the age of the colonies). Mound walls were more enriched in clay and impoverished in C and N in the Luvisol than the Ferralsol. However, their shape was more complex in the Ferralsol than the Luvisol, suggesting a possible link between the clay content in soil and the shape of termite mounds. The results also suggest that clay becomes enriched in O. obesus mound walls through a more passive process rather than solely by particle selection, and that termite mound shape results from the soil properties rather than the ecological needs of termites. In conclusion, although ecologists have mainly focused upon the influence of termite ecological needs on their nest properties, this study highlights the need for a better understanding about the role of the soil pedological properties and, as a consequence, how these properties drive the establishment and survival of termites in tropical ecosystems.

A new method to constrain soil development time using both OSL and radiocarbon dating

The time over which a soil has developed since the parent materials were deposited and subaerially exposed, referred to here as soil development time, is of considerable interest to pedologists, geomorphologists, geologists, archeologist, and paleoclimatologists. Soil development time has been estimated both indirectly, based on the degree of soil development, and directly, by radiocarbon dating of soil organic matter, optically stimulated luminescence (OSL) dating of parent material deposition, and through exposure dating using cosmogenic nuclides. Here we propose a new model for estimating the soil development time by subtracting the low molecular weight (LMW) or pyrolysis-volatile 14C age of the uppermost A horizon of a soil from the OSL age of the C horizon of the parent material [soil time=OSL age(parent C horizon)−14C age(LMW fraction of uppermost A horizon)]. The LMW organic compound fraction represents the most mobile carbon compounds in the soil organic carbon pool, and is least resistant to physical, chemical, and biodegradation in the soil environment, potentially yielding the youngest 14C age. OSL dating of the C horizon provides an estimate of the time since deposition of unconsolidated parent material. Thus, the difference in the two ages can be used to estimate the time that has elapsed for pedogenic alteration from deposition of the parent material to the most recent additions of soil organic carbon. We applied this new approach in four scenarios: (1) in a modern soil that developed downward in loess; (2) in a buried soil developed in aggrading loess (a cumulative soil which grows upward); (3) in a buried soil formed in dune sand; and (4) in a counterexample showing that simple subtraction is not always appropriate because of changes in soil's parent materials from loess to sand. These case studies reveal that this approach constrains soil development time more reasonably than can be commonly done with either OSL or radiocarbon dating alone. The difference in 14C ages between the uppermost and lowermost sola of a soil profile almost certainly underestimates the time of soil development, and the difference in OSL ages taken from sediment units overlying and underlying a buried soil most likely overestimates it. A combination of OSL and radiocarbon dating better constrains soil development time, broadening the applications of these two dating methods beyond their use for cross-checking the accuracy of the other dating method.

Nitrogen loss from windblown agricultural soils in the Columbia Plateau

Abstract Wind erosion of agricultural soils can degrade both air quality and soil productivity in the Columbia Plateau of the Pacific Northwest United States. Soils in the region contain fine particles that, when suspended, are highly susceptible to long range transport in the atmosphere. Nitrogen (N) associated with off-site transport of windblown particulate matter depletes the parent soil of nutrients important in sustaining the biological activity of soils. The objective of this study was to quantify the loss of N from eroding agricultural fields during high wind events. Soil eroded from fields subject to conventional tillage in winter wheat–summer fallow rotations in eastern Washington was trapped in creep and Big Spring Number Eight (BSNE) samplers installed on the leeward side of fields at heights of 0–1.5 m above the surface. The location of field sites varied over the 8 years of this study, but all sites were characterized by soils with a silt loam texture and annual precipitation of ⩽305 mm. Nitrogen content of the parent soil ranged from 0.063% to 0.090% while N content of sediment trapped by the samplers during high winds ranged from 0.053% to 0.101%. Enrichment ratios (ERs) for N ranged from 0.8 to 1.3, indicating the sediment was not highly enriched in N as compared with the parent soil. Nitrogen loss was estimated to range from 0.1 to 1.9 kg ha−1 during a high wind event. Nitrogen loss may be reduced by using conservation practices that have been proven effective in controlling wind erosion.

The influence of termites on soil sheeting properties varies depending on the materials on which they feed

Fungus-growing termites are involved in many ecological processes and play a central role in influencing soil dynamics in the tropics. The physical and chemical properties of their nest structures have been largely described; however less information is available concerning the relatively temporary structures made above-ground to access food items and protect the foraging space (the soil ‘sheetings’). This study investigated whether the soil physical and chemical properties of these constructions are constant or if they vary depending on the type of food they cover. Soil samples and soil sheetings were collected in a forest in India, from leaves on the ground (LEAF), fallen branches (WOOD), and vertical soil sheetings covering the bark of trees (TREE). In this environment, termite diversity was dominated by Odontotermes species, and especially Odontotermes feae and Odontotermes obesus. However, there was no clear niche differentiation and, for example, O. feae termites were found on all the materials. Compared with the putative parent soil (control), TREE sheetings showed the greatest (and most significant) differences (higher clay content and smaller clay particle sizes, lower C and N content and smaller δ13C and δ15N), while LEAF sheetings were the least modified, though still significantly different than the control soil. We suggest that the termite diversity is a less important driver of potential soil modification than sheeting diversity. Further, there is evidence that construction properties are adapted to their prospective life-span, with relatively long-lasting structures being most different from the parent soil.

Earthworm Cast Biomass Under Three Managed Ecosystems: Implication for Soil Fertility

The study was conducted to determine earthworm cast biomass under three managed ecosystems, Gmelina, Cashew and Banana plantations at Federal University of Agriculture, Abeokuta and its impact on the soil physicochemical parameters. Seven, five and four plots of 3 m2 each were sampled in Gmelina, Cashew and Banana plantations respectively. Each plot was laid out in form of a grid and seven quadrats of 44 cm x 44 cm each were sampled in each plot. On-field Cast weights were determined to the nearest gram using a top loading mechanical balance and the cast biomass was calculated from these. The nutrient and mineral properties of both earthworm casts and parent soils were determined using standard methods of AOAC. The % OC (4.61), %OM (7.96), sulphate (38.37), pH (7.78), total nitrogen (0.27), Mn (0.47) and Fe (7.23) were significantly higher (p<0.05) in the earthworm casts under Gmelina plantation compared with the cashew and banana plantations. Cu and Fe concentrations in the parent soil under Gmelina plantation were significantly higher (p<0.05) than under cashew and banana plantations while Mg and Mn concentrations showed no significant difference. Compared with the parent soil, %OC, %OM, Mn and Fe obtained from earthworm casts were significantly higher (p<0.05) under all three plantations. Earthworm cast biomass under the Gmelina plantation (15483.63g/m2) was significantly (p<0.05) higher than that obtained under the cashew (13270.83g/m2) and banana (8828.13) plantations. The present results showed that earthworm activity is better supported under Gmelina than cashew and banana plantations In addition, the higher cast biomass and nutrient level in the parent soil under Gmelina plantation signifies a significantly higher nutrient level which, expectedly means that the Gmelina plantation soil will be more fertile than the soil in cashew and banana plantations.Key Words: Earthworm cast, Gmelina, Cashew, Banana, physicochemical

Biogeochemistry of dust sources in Southern Africa

In Southern Africa, the Makgadikgadi Pan in Botswana and the Etosha Pan in Namibia are two of the major dust sources in the Southern Hemisphere. Dust from Southern Africa could play an important role in sustaining the productivity of the surrounding terrestrial and marine ecosystems. However, very little is known about the biogeochemical properties of dust from this region. In this study, we analyze sediments from the Makgadikgadi and Etosha salt pans and the Kalahari dunes and compare the total nitrogen, total phosphorous, soluble iron and common anions between the soil fine fraction (<45 μm) and parent soil. Our results show that in the pans, the fine fractions are richer in total nitrogen and total phosphorous than the parent material whereas the parent material is richer in soluble iron than the fine fraction. In the Kalahari sands, the fine fraction is richer in total nitrogen whereas the parent material has higher total phosphorous and soluble iron than the fine fraction. This study quantifies the amount of biogeochemically important nutrients that can be emitted by Southern African sources which could be incorporated into models of dust emission and transport to assess the impact of dust in regional and marine ecosystems.

Carbon dioxide concentration in temperate climate caves and parent soils over an altitudinal gradient and its influence on speleothem growth and fabrics

AbstractCarbon dioxide (CO2) concentrations in caves and parent soils in the Italian Alps have been studied along a 2100 m altitudinal range – corresponding to a mean annual temperature (MAT) range of 12°C – in order to investigate the relationship between MAT, soil pCO2 and cave air pCO2, and to test the influence of soil pCO2 on speleothem growth and fabric to ultimately gain insight into their palaeoclimatic significance in temperate climate settings.Our findings indicate that soil CO2 is linearly correlated to MAT and its mean annual concentration is described by the equation: soil CO2 (ppmv) = 1112 + 460 MAT. Soil pCO2 can also be exponentially correlated to actual evapotranspiration. The pCO2 in the aquifer is linearly correlated to MAT at the infiltration site and is more influenced by summer soil pCO2. Cave air CO2 in the innermost part of the caves exhibits a similar seasonal pattern, and commonly reaches concentrations of about 15% to 35%, with respect to the corresponding soil values, and is exponentially correlated to the MAT at the infiltration site.The combination of these parameters (soil pCO2, dripwater pCO2 and cave air pCO2) results in speleothem growth and controls their fabrics which are typical of four MAT/elevation belts broadly corresponding to the present‐day vegetation zones. In the lower montane zone [100–800 m above sea level (a.s.l.)] speleothems mostly consist of columnar fabric, in the upper montane zone (800–1600 m a.s.l.) both columnar and dendritic fabrics are common, the Subalpine zone (1600–2200 m a.s.l.) is characterized mostly by moonmilk deposits, whereas in the Alpine zone (above 2200 m a.s.l.) no speleothems are forming today. Therefore, fabric changes in fossil speleothem can potentially be used to reconstruct MAT changes in temperate climate karst areas. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Fractionation of lead-acid battery soil amended with Biochar

Mobile (bio)available metal concentration in contaminated soils can be minimized through biological immobilization and stabilization methods using a range of organic compounds, such as “biochar.” Biochar has a high surface area, highly porous, variable – charge organic material that has the potential to increase soil water holding capacity, surface sorption and base saturation when added to soil. The soil was characterized before and after amending by standard method. The parent soil used for this study was collected from lead–acid battery chargers’ workshop. The physico-chemical properties of the soil are: pH=5.0, 0.24% organic carbon, 32.5 cmol.kg-l CEC, 1.02, 23.0, 17.36, 10.05, 7.25 and 9.74 mg.kg-l, for N, Na, P, Zn, Cu and Pb respectively. The pH, organic carbon and CEC of the biochar were 8.59, 78.70% and 82.27cmol.kg-l respectively, while the concentration of heavy metals in the biochar ranged; 0.10 –1.20mg.kg-l. There is a gradual decrease in the concentration of the heavy metals as the concentration of biochar increases from 5 – 20%. Fractionation result shows that the heavy metals (Zn,Cr,Cd,Cu and Pb) were mainly associated with the residual fraction, the mobility factor for the heavy metals was calculated and found to be higher for all metals in the parent soil than the Biochar amended soil. Contamination levels were moderate for Cd and Cr, considerably for Pb, Cu and Zn. The results indicated that long term discharge of these battery chargers’ wastes into the environment will cause accumulation of some toxic metals in soils which may lead to elevated levels of these metals in plants.Keywords: Biochar, Lead–acid Battery, Fractionation and Heavy metals.

Soil-borne pathogens restrict the recruitment of a subtropical tree: a distance-dependent effect.

The Janzen-Connell hypothesis suggests that density- and/or distance-dependent juvenile mortality driven by host-specific natural enemies can explain high species diversity in tropical forests. However, such density and distance effects may not occur simultaneously and may not be driven by the same mechanism. Also, reports of attempts to identify and quantify the differences between these processes in tropical forests are scarce. In a primary subtropical forest in China, we (1) experimentally examined the relative influence of the distance to parent trees vs. conspecific seedling density on mortality patterns in Engelhardia fenzelii, (2) tested the role of soil-borne pathogens in driving density- or distance-dependent processes that cause seedling mortality, and (3) inspected the susceptibilities of different tree species to soil biota of E. fenzelii and the effects of soil biota from different tree species on E. fenzelii. The results from these field experiments showed that distance- rather than density-dependent processes driven by soil pathogens strongly affect the seedling survival of this species in its first year. We also observed increased survival of a fungicide treatment for E. fenzelii seedlings in the parent soil but not for the seedlings of the other three species in the E. fenzelii parent soil, or for E. fenzelii seedlings in the parent soil of three other species. This study illustrates how the distance-dependent pattern of seedling recruitment for this species is driven by soil pathogens, a mechanism that likely restricts the dominance of this abundant species.

Soil gas radon assessment and development of a radon risk map in Bolsena, Central Italy.

Vulsini Volcanic district in Northern Latium (Central Italy) is characterized by high natural radiation background resulting from the high concentrations of uranium, thorium and potassium in the volcanic products. In order to estimate the radon radiation risk, a series of soil gas radon measurements were carried out in Bolsena, the principal urban settlement in this area NE of Rome. Soil gas radon concentration ranges between 7 and 176 kBq/m3 indicating a large degree of variability in the NORM content and behavior of the parent soil material related in particular to the occurrence of two different lithologies. Soil gas radon mapping confirmed the existence of two different areas: one along the shoreline of the Bolsena lake, characterized by low soil radon level, due to a prevailing alluvial lithology; another close to the Bolsena village with high soil radon level due to the presence of the high radioactive volcanic rocks of the Vulsini volcanic district. Radon risk assessment, based on soil gas radon and permeability data, results in a map where the alluvial area is characterized by a probability to be an area with high Radon Index lower than 20 %, while probabilities higher than 30 % and also above 50 % are found close to the Bolsena village.

Laboratory chamber measurements of the longwave extinction spectra and complex refractive indices of African and Asian mineral dusts

AbstractIn this study we present the first results from laboratory chamber experiments newly designed to investigate the longwave optical properties of mineral dust. Extinction spectra in the 2–16 µm range have been measured in situ (T = 293 K, RH &lt; 2%) for polydispersed pure dust aerosols generated from natural parent soils from Tunisia, Niger, and the Gobi desert. Data are used in combination with particle size distributions to estimate the complex refractive index of each dust sample. Our results show that the magnitude and spectral dependence of the dust extinction and refractive indices differ according to particle mineralogy, suggesting the necessity for regionally resolved optical properties for modeling dust radiative effects in the longwave. The magnitude of extinction is controlled by the particle size distribution and remains significant down to low coarse particle concentrations, indicating that the longwave effect of mineral dust persists throughout long‐range transport and is thus relevant at the global scale.

Variation with height of aeolian mass flux density and grain size distribution over natural surface covered with coarse grains: A mobile wind tunnel study

Abstract The vertical distributions of aeolian mass flux density and grain size with height over the natural surface covered with coarse grains were investigated using a mobile wind tunnel in the Yardang Geological Park, Dunhuang, China. Results reveal that the mass flux density of mix-sized sediments decays exponentially with increasing height. However, the mass flux density profiles of separate grain-size groups depend on size grading: those of coarse sand groups (0.8–2.0 mm) can be described by exponential decay functions while those of fine sand groups (0.063–0.8 mm) can be expressed by Gaussian distribution functions. Therefore, the mass flux density profile of mix-sized saltating particles is a superposition of many different profiles. In addition, results of grain-size analysis show that the size distribution of eroded sediments close to the ground reflects that of the loose material in the parent soil. The mean grain size first deceases remarkably with increasing height in the near-surface region, this trend is reversed at heights of 60–80 or 120–140 mm above the bed and then there is a coarsening trend of mean size with height. Sorting only improves with height in the region above 80 or 100 mm, but it declines in the near-bed region. These experimental data are significant for studies of heterogeneous saltation and numerical modeling of grain trajectories.