Topsoil Level Research Articles

Assessment of the Railroad Transport Impact on Physical and Chemical Soil Properties: The Case Study from Zduńska Wola Karsznice Railway Junction, Central Poland

Contamination of the soil and water environment with harmful substances can be associated with many activities carried out on the railway. The problem is particularly relevant to liquid fuel loading and refueling facilities as well as to increased traffic at railway junctions. Studies were conducted in the area of railway junction Zduńska Wola Karsznice in central Poland (Łódź Voivodeship). Soil samples were collected from specific research points: from the inter-railway (A), 5 m from the main track (B), from the embankment—10 m from the main track (C), and from the side track (D), at the depth of 0–5 cm (1) and 20 cm (2). The following analyses were made: granulometric composition, pH in H2O, and percent content of carbonates (CaCO3). PHEs were determined in the fractions: 0.25 ≤ 0.5 mm, 0.1 ≤ 0.25 mm, and 0.05 ≤ 0.1 mm: Pb, Cd, Cr, Co, Cu, Ni, Zn, Sr by inductively coupled plasma mass spectrometry technique (ICP-MS/TOF OPTIMass 9500). The objectives of the study were (1) to assess PHEs (potentially harmful elements) contamination of the topsoil level of railway area, (2) to determine the correlation between the concentration of PHEs and the size of the fraction, and (3) to identify the areas (places) where the highest concentrations of PHEs were recorded. Based on the studied parameters, significant differentiation in soil properties of the areas in Zduńska Wola Karsznice was found. The analyses carried out showed that the accumulation of potentially harmful elements was as follows: Cu > Zn > Sr > Pb > Ni > Cr > Co > Cd. The average concentrations of Cu, Zn, Sr, Pb, Ni, Cr, Co and Cd were 216.0; 152.1; 97.8; 64.6; 15.2; 14.4; 3.1 and 0.2 mg·kg−1 d.w., respectively. These contaminations occur in the topsoil layer of the railway embankment, which suggests a railway transport origin. The highest concentrations of PHEs were recorded in samples collected from close to the rails (inter-railway, side track), and in the embankment (10 m from the track) in the very fine sand fraction (0.05 ≤ 0.1 mm). The high accumulation index of copper, cadmium and lead in the surface layer of soil indicate their anthropogenic origin. The results presented in the paper can be used in local planning and spatial development of this area, taking into account all future decisions about ensuring environmental protection, including groundwater and soils.

Cadmium (Cd) and Lead (Pb) topsoil levels and incidence of childhood leukemias

There are few well-established risk factors for childhood leukemias. While the frequency of childhood leukemias might be partially attributable to some diseases (accounting for a small fraction of cases) or ionizing radiation, the role of heavy metals has not been assessed. The objective of our study was to assess the potential association between levels of cadmium (Cd) and lead (PB) in soil and childhood leukemias incidence. We conducted a population-based case-control study of childhood leukaemia in Spain, covering 2897 incident cases gathered from the Spanish Registry of Childhood Tumours and including 14 Spanish Regions with a total population of 5,307,433 children (period 1996-2015). Cd and Pb bioavailable levels at every children's home address were estimated using data from the Geochemical Atlas of Spain. We used logistic regression to estimate odds ratios (ORs) and their 95% confidence intervals (95%CIs); we included as covariates: sex, rurality, employment rate and socioeconomic status. Metal levels were analysed according to two definitions: as continuous variable assuming linearity and as categorical variables to explore a potentially nonlinear association (quantiles). Increases in both Cd and Pb topsoil levels were associated with increased probability of childhood leukemias incidence. The results for the models with the continuous variables showed that a unit increase on the topsoil level was associated with an OR of 1.11 for Cd (95%CI 1.00-1.24) and an OR of 1.10 for Pb (95%CI 0.99-1.21). Our study may point towards a possible link between residential Cd and Pb topsoil levels and the probability of childhood leukemias incidence. Residing in a location with the highest concentrations of these heavy metals compared to those locations with the lowest could increase the risk around a 20%, for both Cd and Pb.

Distribution of Primary Nutrients (NPK) to Crop Production in Profiles of Soils Derived from Coastal Plain Sand in Ikot Ekpo, Calabar, Cross River State, Nigeria

This study was conducted to evaluate the distribution of primary nutrients (NPK) in profiles of the coastal plain soils of Ikot Ekpo, Calabar, as well as evaluate other soil properties critical to agricultural productivity, in a bid to generate data that will serve as a guide to effective land use and management of the soils for arable crop production. Three (3) Profile pits were dug on the crest, middle slope and valley bottom, and soil samples were collected from their pedogenetic horizons for analysis. Analytical results showed the three profiles of coastal plain soils studied had predominantly sandy particle sizes (ranged from 770 - 910 gkg-1 sand across the three profiles) and mostly loamy sand in texture; especially at the topsoil level. The soils were also acidic (pH 4.7 to 5.1) and low in organic matter (1.0 mg kg-1 to 16.0 mg kg-1) as expected. Generally, the soils were found to be low in total nitrogen content (0.1 to 1.3 mg kg-1) and exchangeable potassium (0.08 to 0.10 cmolc kg-1); however, they were high in available phosphorus (17.20 to 29.75 mg kg-1). NPK distribution charts showed that N and P decreased consecutively with increasing depth for the crest profile. The middle-slope and valley bottom profile showed no definite pattern of distribution. However, the concentration of NPK was highest at topsoil level across most profiles. N had the shallowest intra-profile distribution with significantly higher levels of topsoil concentration indicated by the high percentages of intra-profile CV (94%, 85% & 97% for CUF, MUF & VUF respectively). P showed a shallow intra-profile distribution across the three profiles but did not vary significantly from the intra-profile mean (12.5%, 12.0% & 2.6% for CUF, MUF & VUF respectively). On the other hand K was more evenly distributed within all three profiles ( CV of 9.4%, 5.3% & 8.6% for CUF, MUF & VUF respective) compared to N and P. Inter-profile distribution of NPK showed that N and P had higher concentrations at crest level, with P showing consecutive decrease in concentration down the slope. This study therefore recommends adoption of different NPK fertilizer recommendations for different soil depths and topographic locations for optimal productivity.

Agricultural soil organic carbon stocks in the north-eastern Iberian Peninsula: Drivers and spatial variability

Estimating soil organic carbon (SOC) stocks under agriculture, assessing the importance of their drivers and understanding the spatial distribution of SOC stocks are crucial to predicting possible future SOC stocks scenarios under climate change conditions and to designing appropriate mitigation and adaptation strategies. This study characterized and modelled SOC stocks at two soil depth intervals, topsoil (0–30 cm) and subsoil (30–100 cm), based on both legacy and recent data from 7245 agricultural soil profiles and using environmental drivers (climate, agricultural practices and soil properties) for agricultural soils in Catalonia (NE Spain). Generalized Least Square (GLS) and Geographical Weighted Regression (GWR) were used as modelling approaches to: (i) assess the main SOC stock drivers and their effects on SOC stocks; (ii) analyse spatial variability of SOC stocks and their relationships with the main drivers; and (iii) predict and map SOC stocks at the regional scale. While topsoil variation of SOC stocks depended mainly on climate, soil texture and agricultural variables, subsoil SOC stocks changes depended mainly on soil attributes such us soil texture, clay content, soil type or depth to bedrock. The GWR model revealed that the relationship between SOC stocks and drivers varied spatially. Finally, the study was only able to predict and map topsoil SOC stocks at the regional scale, because controlling factors of SOC stocks at the subsoil level were largely unavailable for digital mapping. According to the resulting map, the mean SOC stock value for Catalan agriculture at the topsoil level was 4.88 ± 0.89 kg/m2 and the total magnitude of the carbon pool in agricultural soils of Catalonia up to 30 cm reached 47.9 Tg. The present study findings are useful for defining carbon sequestration strategies at the regional scale related with agricultural land use changes and agricultural management practices in a context of climate change.

Diversity of Soil Arthropods in Different Soil Stratification Layers, The National Park of Gede Pangrango Mountain, Cisarua Resort, West Java, Indonesia

Soil arthropods has an important role for guarding food web sustainability, so its diversity value usually exert a strong influence on the ecosystem balance. Understanding arthropods soil diversity become important in maintaining soil quality. This research aims to analyze arthropods diversity in different top soil level around mount Pangrango National Park, Cisarua Resort Bogor, West Java. Sample were collected by monolith (25cm x 25cm x10cm). Devided into 3 layers (A: 10-20 cm, B: 20-30 cm, and C: 30-40 cm) and collected from agriculture field, riverside area, primary forest, and secondery forest. A total 143 individualswere found consisting of 8 order and 19 family (Staphylinidae, Carabidae, Scarabaedae, Alycidae, Formicidae, Polydesmidae, Parasitidae, tenebrionidae, Scolytidae, Curculionidae, Ptiliidae, Scydmaenidae, Alycidae, Miridae, Antrodiaetidae, Arachnidae and Drosipilidae), Formicidae and Staphylinidae are dominant with respectively 58,7% and 18,9%. Various result in diversity, richness, eveness and dominance were showed in different vertical soil level. The highest Arthropods diversity index (1,49) found at riverside in the soil layer A. Diversity index on top soil level A (0-10 cm) all showed moderate level, B level (10-20 cm) showed two moderate and two low, C level (20-30 cm) showed one moderate and 3 low. Therefore, increasing soil depth showed increasing low level of arthropods diversity index

Connectivity assessment in Mediterranean vineyards using improved stock unearthing method, LiDAR and soil erosion field surveys

AbstractThe interaction between processes and landforms is accelerated in vineyards due to bare tilled soils that enhance splash, runoff, and erosion. Traditionally, in order to assess these processes, the stock unearthing method (SUM) is considered a useful methodology that uses the graft union of the vine plant as passive bio‐indicator of the topsoil level changes. However, SUM assumes that the topography between the rows is planar when development of a model of the current micro‐topography is performed. Thus, we consider that there is a need to develop a new methodology (ISUM: improved SUM) that, by adding new measurements in the inter‐row areas (at least 3), allows inclusion of the absent micro‐topographical information of SUM. In this way, the main aim of this research was to estimate the micro‐topographical changes and soil transport at three different slope positions (upper, middle and lower parts) in a 25‐years‐old vineyard in eastern Spain. LiDAR data were used to compare the connectivity processes at the catchment with the pedon scale. We obtained maps that showed topsoil level changes and detected soil depletion and accumulation signals. We estimated soil displacement rates of –1.6 Mg ha yr‐1 (depletion), +2.8 Mg ha yr‐1 and +13.3 Mg ha yr‐1 (accumulation) at upper, middle and lower slope positions, respectively. The total average soil erosion rates in the inter‐rows were –5.7 Mg ha‐1 yr‐1. In the row areas, deposition of +10.5 Mg ha yr‐1 was measured. Field erosion marks surveyed after each rainfall event gave insights to the connectivity at the inter‐row and the slope scale. It was found that at the row scale there were sinks of sediments underneath the vines and sources in the inter‐row parts, although they are the highest and lowest local topographical terrain, respectively. This is due to tillage erosion that redistributed the sediments. At the slope scale, the lower part of the slope collected sediments from the upper slope positions, which were transported along the middle part of the slope, as the measurement of ISUM and the field survey after intense rainfall events demonstrated. Connectivity of the flows along the whole slope were rare (twice), and along individual slope parts connectivity was found eight times, and 19 at the inter‐row scale after 8 years of field observations. Copyright © 2018 John Wiley & Sons, Ltd.

Soil erosion in sloping vineyards assessed by using botanical indicators and sediment collectors in the Ruwer-Mosel valley

Steep slopes, erodible soils, rill and ephemeral gullies, compaction due to wheel traffic and human trampling are common features in vineyards around the world and result in high soil erosion rates. However, little is known about seasonal and spatial variations of soil erosion rates due to factors such as the impact of the vine plantation, harvest, and tillage on the soil redistribution over the long-term temporal scale. The goal of this study is to assess long-term soil erosion rates and the impact of management on sediment and runoff yield by means of Gerlach troughs and a topographical approach based on botanic benchmarks in two paired vineyards with different ages (3 and 35 years) located on the hillslope of the Ruwer-Mosel Valley (Germany). We studied: i) soil profiles and properties at different hillslope locations and ii) soil redistribution and erosion by means of topsoil level maps applying botanic benchmarks using the Stock Unearthing Method (SUM), RUSLE (Revised Unviersal Soil Loss Equation) and Gerlach troughs. The SUM showed that the old vineyard’s erosion rates ranged from 3.3 to 3.8 Mgha−1yr−1, which was similar to the Gerlach trough measurements, and we demonstrated that the soil erosion rates depended on rainfall characteristics and human disturbances due to tillage, harvest trampling, and compaction by heavy machinery. Data from the SUM in the young vineyard showed 62.5 Mgha−1yr−1 of soil loss, which is a consequence of severe soil disturbance during the planting of the new vineyard. Finally, to prove the reliability data, RUSLE showed higher soil loss in the young vineyards (19.46 Mgha−1yr−1) than in the old ones (11.28 Mgha−1yr−1).

Impact of Normal and Shear Stresses Due to Wheel Slip on Hydrological Properties of an Agricultural Clay Loam: Experimental and New Computerized Approach

The main purpose of this study was to evaluate the effect that mechanical stresses acting under the slipping driving wheels of agricultural equipment have on the soil’s pore system and water flow process (surface runoff generation during extreme event). The field experiment simulated low slip (1%) and high slip (27%) on a clay loam. The stress on the soil surface and changes in the amounts of water flowing from macropores were simulated using the Tires/tracks And Soil Compaction (TASC) tool and the MACRO model, respectively. Taking a 65 kW tractor on a clay loam as a reference, results showed that an increase in slip of the rear wheels from 1% to 27% caused normal stress to increase from 90.6 kPa to 104.4 kPa at the topsoil level, and the maximum shear contact stress to rise drastically from 6.0 kPa to 61.6 kPa. At 27% slip, topsoil was sheared and displaced over a distance of 0.35 m. Excessive normal and shear stress values with high slip caused severe reductions of the soil’s macroporosity, saturated hydraulic conductivity, and water quantities flowing from topsoil macropores. Assuming that, under conditions of intense rainfall on sloping land, a loss in vertical water flow would mean an increase in surface runoff, we calculated that a rainfall intensity of 100 mm h-1 and a rainfall duration of 1 h would increase the runoff coefficient to 0.79 at low slip and to 1.00 at high slip, indicating that 100% of rainwater would be transformed into surface runoff at high slip. We expect that these effects have a significant impact on soil erosion and floods in steeper terrain (slope > 15°) and across larger surface areas (> 16 m2) than those included in our study.

Structural sustainability of cambisol under different land use system

Incongruous management techniques have been associated with some significant loss of agricultural land to degradation in many parts of the world. Land degradation results in the alteration of physical, chemical and biological properties of the soil, thereby posing a serious threat to sustainable agricultural development. In this study, our objective is to evaluate the changes in a Cambisol structure under six land use systems using the load bearing capacity model. Sampling was conducted in Amazonas Region, Brazil, in the following land use: a) young secondary forest; b) old secondary forest; c) forest; d) pasture; e) cropping, and f) agroforestry. To obtain the load bearing capacity models the undisturbed soil samples were collected in those land use systems and subjected to the uniaxial compression test. These models were used to evaluate which land use system preserved or degraded the Cambisol structure. The results of the bulk density and total porosity of the soil samples were not adequate to quantify structural degradation in Cambisol. Using the forest topsoil level (0-0.03 m) as a reference, it was observed that pasture land use system was most severe in the degradation of the soil structure while the structure were most preserved under old secondary forest, cropping system and forest. At the subsoil level (0.10-0.13 m depth), the soil structure was most degraded in the cropping land use system while it was most preserved in young secondary forest and pasture. At the 0.20-0.23 m depth, soil structure degradation was most severe in the old secondary forest system and well preserved in young secondary forest, cropping and agroforestry.

Agricultural traffic: Motion resistance and soil compaction in relation to tractor design and different soil conditions

Farmers may desire a high cone index soil for tractive purposes or a low cone index (CI) soil for root penetration and seedling emergence. The function of any agricultural tractor is to provide mobility for itself and to power an implement. The aim of this paper was to (a) assess the impact of two tractors with different tyre sizes and axle loads on motion resistance (MR) and on the CI for three different soil mechanic conditions and (b) determine the existing relationships between MR and ground pressure parameters and tyre sinkage. Traffic was simulated with one pass on clay soil for a front-wheel assist tractor (FWA, load=77.7kN) and a four-wheel drive tractor (4WD, load=98.01kN) on three soil conditions: direct sowing systems, ploughed and seedbed. The outlined hypotheses were as follows: (1) there is a direct relationship between the subsoil compaction and the MR force of the FWA and 4WD tractors, and (2) the power loss produced by the MR depends on the soil mechanics. The experiment was conducted in the eastern section of the Rolling Pampa region of Argentina at 34°36′S, 58°40′W. MR, rut depth (RD) and CI were measured. The MR mean values of the 4WD were 9.30, 6.59 and 2.31kN for ploughed, seedbed and direct sowing soil, respectively, whereas the values for the FWA were 10.41, 7.91 and 4.67kN, respectively. For the three soil conditions, no significant differences were found in the RD between the 4WD and FWA. For the topsoil level (0–150mm), one FWA pass caused mean values in the CI of 2150, 1835 and 1780kPa for direct sowing, seedbed and ploughed soil, respectively, whereas for 4WD the values were 1890, 1640 and 1587kPa, respectively. For the subsoil (150–600mm), 4WD caused higher CI values than the FWA. The CI mean values of the 4WD were 2477, 2240 and 1890kPa for direct sowing, seedbed and ploughed soil, respectively, whereas the values for the FWA were 2240, 1870 and 1770kPa, respectively. For the different soil conditions, the subsoil compaction increased as the total axle load increased, independently from the ground pressure. Moreover, for both tractors, a greater MR force was observed in the soil with the lowest bearing capacity. The smallest power loss ratio due to MR and engine power was found with the 4WD.

Munkahelyteremtés és agroenergetika-vizsgálatok az Észak-Alföldön

Both the European both the Hungarian agribusiness faced new challenges when the ris-ing world price of the crude oil brought the bio-energy products, produced on arable lands into focus. This new branch of agriculture should be paid significant attention because it is not only appropriate for the utilization of the unfavourable areas (extreme water manage-ment, shallow topsoil level) but with good technology it could generate significant labour demand which is the most important question in rural development. During the examina-tion of spreading of SRF it is necessary to examine the appropriate structural requirements (economic aspects, logistics, time and spatial dimensions) for the sake of satisfying the above mentioned complex functions and avoiding to create SRFs only because of fashion, or because of the utilization of subsidies. The aim of the author is to analyse the manage-ment aspects of SRF systems in the research, focusing on rural employment possibilities.

Soil compaction produced by tractor with radial and cross-ply tyres in two tillage regimes

The aim of this paper was to quantify soil compaction induced by tractor traffic on two tillage regimes: conventional tillage and direct drilling. Traffic was simulated with one pass of a conventional 2WD tractor, using four configurations of cross-ply rear tyres: 18.4–34, 23.1–30, 18.4–38 and 24.5–32, and four configurations of radial tyres 18.4R34, 23.1R 30, 18.4R 38 and 24.5R 32, with two ballast conditions used in each configuration. The experiment was conducted in the east of the Rolling Pampa region, Buenos Aires State, Argentina at 34°25′S, 59°15′W; altitude 22 m above sea level. Rut depth after traffic and soil bulk density and cone index in a 0–450-mm profile were measured before and after traffic. Considering topsoil level, in two tillage regimes, all treatments induced significant values of soil compaction as compared to the control plot without traffic. Subsoil compaction increased as total axle load increased and was independent of ground pressure. For the same tyre configuration, radial tyre caused less soil compaction than the cross-ply.

TRACE METALS IN SOILS AND PLANTS FROM FADAMA FARMS IN EKITI STATE, NIGERIA

Levels of zinc, manganese, cobalt, selenium, copper, molybdenum, chromium, iron, aluminium, lead and cadmium were determined in plant organs (buds, flowers, fruits, seeds, leaves, stems, roots, cobs, styles, shaft, grains and efflorescences) and underlying soils of three Fadama farms located in Ifaki-Ekiti, Ado-Ekiti and Ikere-Ekiti of Ekiti State, Nigeria at 0–15 cm topsoil level. The pH levels were alkaline (7.0±0.3 – 8.1±0.7) while the soil texture ranged between loamy sand and sandy loam. There was similarity in Zn trend as was observed in Mn, Fe and Cu but they were of lower levels than Zn. Only Zn and Fe were mostly concentrated in the plant organs with Mn in very few plants. The index of bioaccumulation (ratio in plant/soil) were recorded for only Zn and Fe with the degree of accumulation ranging from medium to intensive (0.87–1.34) in Fe but only intensive (1.41–4.42) in Zn. KEY WORDS : Trace metals, Soils, Plant organs, Bioaccumulation Bull. Chem. Soc. Ethiop. 2005, 19(1), 23-34.

Factors Affecting Fluctuations of the Aquatic Warbler Acrocephalus paludicola Population of Byelarussian Mires

Data on the density of Aquatic Warbler and plant associations in the marshes of the Sporovskiy reserve (Byelarus') were collected between 1996 and 2003. The species density changed between years from 135 to even 0 males per km². The density and numbers of these birds are governed mainly by changes in the groundwater table caused by floods, droughts or fires. Aquatic Warblers breed successfully when the groundwater table coincides with the topsoil level; the optimal water table lies in the range from 12 cm above the soil to 5 cm below it. Between 1981 and 2002 successful first-clutch breeding occurred 11 times (47.8%); in only 4 years was second-clutch breeding successful (17.3%). First and second clutches both failed in 9 years (39%). The pattern of changes in the population size and data on the recovery of the population size following such unfavourable years indicates that the key factors governing the overall population size are not migration or wintering conditions, but rather the state of the breeding biotopes. Active management of fenland still in its natural state is therefore of paramount importance.

Detection of nitrate leaching through bypass flow using pan lysimeter, suction cup, and resin capsule

We compared the use of mixed-bed ion exchange resin capsules (RC), suction cups (SC), pan lysimeters (PL), and subsurface drainage (DR) for the detection of nitrate movement through a clayey soil where onion (Allium cepa L.) had been cultivated over a period of seven months. At the topsoil level, solutions collected with SC showed higher concentrations of NO3 − than the PL-collected samples. At 80-cm depth, however, the concentrations of NO3 − were higher for the DR and PL samples than for the SC samples, suggesting that bypass or macropore flow was the primary mechanism of NO3 − transport to subsurface drainage or groundwater, while solutions collected by SC mostly represented solutions inside soil aggregates. The use of the resin capsule method resulted in higher values of NO3 − at 15- than at 50-cm depth initially but the trend was reversed after sufficient leaching and plant uptake. High and significant correlations were obtained between the amount of NO3 − adsorbed on RC at 15-cm depth and the mean concentration of NO3 − in the DR samples during the RC installation period and between the NO3 − adsorbed on RC at 50-cm depth and the mean NO3 − concentration of PL samples at 80-cm depth. Such results indicate that the RC method which enables the detection of nitrate transport via macropore flow is a promising technique for nitrate leaching measurements.

Soils of flood plains of west Africa: General fertility status

As a part of efforts to effectively utilize the wetlands of the West Africa sub-region for the production of rice and other crops, in order to alleviate the persistent food shortage while also protecting and conserving the environment for sustainability, the general fertility status of flood plain soils were assessed. The whole sub-region was found to be deficient in available phosphorus. Available P (Bray No.2) was deficient for both the humid Equatorial forest (EF) and sub-humid Guinea savanna (GS), as well as the drier northern sector of Sudan savanna (SuS) and Sahel savanna (SaS) zones. Mean available P levels in the topsoil (0-15 cm) were 9.84, 8.01, 7.25, and 7.31 mg kg-1 for the EF, GS, SuS, and SaS zones respectively. Effective cation exchange capacity (eCEC) and levels of exchangeable K, Ca, and Mg were higher for the SaS and SUS than for the GS and EF zones. The level of exchangeable K was, however, very low within the EF zone. The soils were slightly acidic to neutral but with isolated areas of high salinity. Mean topsoil (0-15 cm) pH for West Africa was 5.4. Mean soil pH varied from 5.7 in the drier SaS, through 5.4 for the SUS and GS zones to 5.2 in the EF zone. Mean topsoil levels of total carbon for the EF (humid) and GS (sub-humid) zones were 14.4 and 16.3 g kg-1 while the dry SuS and SaS zones showed topsoil means of 8.3 and 6.2 g kg-1 respectively. Total nitrogen levels, however, were low throughout the sub-region particularly within the SaS and SuS zones which showed respective topsoil means of 0.71 and 0.88 g kg-1. Mean topsoil level of total nitrogen for West Africa flood plains was 0.98 g kg-1. C/N ratios ranged from 8–13 except for the EF which showed quite higher, 18–20, ratios.