Predicting the distribution of arsenic in groundwater by machine learning technique in two worst hit districts of Assam, India: a risk to public health

Arsenic (As) is a well-known human carcinogen and a significant chemical contaminant in groundwater. The spatial heterogeneity in the distribution of As in groundwater makes it difficult to predict the location of safe areas for tube well installations for consumption and agricultural use. Geospatial machine learning techniques have been used to predict the location of safe and unsafe areas of groundwater As contaminations. Here we used a similar machine learning approach to determine the risk and extent of As >10 ug/L in groundwater at a finer spatial resolution (250m x 250m) in two worst-hit districts of Assam, India, to advise policymakers for targeted campaigning for mitigation. Random Forest Model was employed in Python environments to predict probabilities of the occurrences of As at concentrations >10 ug/L using several intrinsic and extrinsic predictor variables. The selection of predictor variables was based on their inherent relationship with the occurrence of As in groundwater. The relationships between predictor variables and proportions of As occurrences >10 ug/L follow the well-documented processes leading to As release in groundwater. We identified extensive areas of potential As hotspots based on the probability of 0.7 for As >10 ug/L. These identified areas include areas that were not previously surveyed and extended beyond previously known As hotspots. Twenty-five percent of the land area (1,500 km2) was identified as a high-risk zone with an estimated population of 155,000 potentially consuming As through drinking water or food cooked with water containing As >10 ug/L. The ternary hazard map (i.e., high, moderate, and low risk for As >10 ug/L) could inform the policymakers to target the regions by establishing newer drinking water treatment plants and supplying safe drinking water.

Przekształcenie obszaru wysoczyzny lessowej pod wpływem gospodarczej działalności człowieka w neoholocenie (na wybranych przykładach z okolic Mozgawy, Ponidzie Pińczowskie)

The Mozgawa area, located in the Ponidzie Pińczowskie Region (SE part of the Nida River Basin), is a very good example of response of the natural environment to the progressive human impact. The research conducted there indicates that before the appearance of the first Neolithic farmers, the relief of the area was different to the modern one. Constant and intensive agricultural use of the loess plateau and the adjacent slopes (started in the Neolithic period some 5890±100 BP) led to the filling of the valley bottoms and local depressions with deluvial deposits, the thickness of which reaches up to 12 m. The deposition of these sediments and elevation of the surface level in the subordinate areas resulted in the creation of the Mozgawka River channel since the begining of the Roman Period. Formerly it was impossible (as it was within the depression) and the runoff was only through the karst system. Since that moment it has also started the accumulation of the alluvial fan, the progradation of which leads to the pushing of the Nida River channel towards the East.

DISTRIBUTION OF RESTORATION SUCCESSIONS IN TAIGA AND FOREST-STEPPE LANDSCAPES OF THE PERMSKY PRIKAMYE (ON THE EXAMPLE OF AGRICULTURAL LANDS)

The research of forest cover development on agricultural lands in the Perm Prikamye was carried the example of taiga and forest-steppe types of landscapes. The Babkinsko-Yugovskoy and Irensko-Kungursky landscapes were select for research. Received information about the geosystem condition in different years using remote sensing data. All landscape changes were record during the formed stable snow cover. As a result, was divide into two classes - forested and treeless areas. Established, the main natural factors of land differentiation by an areas and a pace of withdrawal from agricultural use are the small contours of agricultural land and differences in soil fertility. The growth pace of forest geosystems within the forest-steppe landscape was 2.5 times higher than of the taiga. The research of the dynamics of forest cover showed that in the Perm Prikamye in the forest-steppe landscape substitution of anthropogenic geosystems with natural-anthropogenic ("wild") accompanied by the development of forest biogeocenosis, not steppe.

Molecular-mass distribution of humus acids of taiga soils

Purpose of the study: to reveal the influence of hydromorphism and agricultural use on the molecular-mass distribution (MMD) of humic (HAs) and fulvic acids (FAs) isolated from the soils of the European northeast of Russia. To assess the influence of the acidity of the medium on the MWD of FAs. Place and time of the event. The studies were carried out on the territory of the middle taiga (Maksimovsky station of the Institute of Biology of the Federal Research Center of the KSC UB RAS, located 8 km west of the city of Syktyvkar and the field of the Syktyvkar state farm, 5 km south-west of Syktyvkar, on the watershed of the Sysola and Vazhel-yu rivers) and northern taiga (3 km west of the Troitsko-Pechorsk station). The objects of the study were humic substances isolated from typical podzolic (Eutric Albic Retisol (Loamic)), gleypodzolic (Eutric Albic Stagnic Retisol (Loamic)), peaty-podzolic surface-gleyed (Eutric Albic Stagnic Histic) Retisol (Loamic Eutric Albic Retisol (Loamic)) soils. The soil sampling period is from 1 to 30 August 2014. Methodology. Quantitative analysis of the MMD of HA and FA preparations was performed using liquid size exclusion chromatography (gel chromatography) on Sephadex G-25 and G-100 gels with continuous automatic registration of the optical density of the eluate (λ = 280 nm) in a quartz flow cell, K 9 × 60 cm column (Pharmacia, Sweden). Distilled water, 0.05 M NaOH solution, and Tris-HCl buffer with pH = 8.2 were used as the eluent. Main results. Studies of the MMD of humic substances have been carried out. It was found that HAs contain three fractions with different molecular weights: ≥ 150 kDa, 73–80 kDa, and 13–23 kDa; FAs – two fractions: ≥ 5 kDa, 1–2 kDa. The low molecular weight of FAs, together with a large amount of oxygen-containing functional groups, contributes to their better solubility and migration ability in soils. The HAs of automorphic soils are characterized by a high content of low molecular weight fractions, and the proportion of the high molecular weight fraction in the HAs of the litter is 1.5–2.0 times higher than in the HAs of the podzolic horizon, which may be due to the migration of the low molecular weight fraction down the profile. The high proportion of the acidic low molecular weight fraction in the podzolic horizon promotes the decomposition of soil minerals and their leaching into the illuvial horizon. The influence of agricultural use of soils on the fractional composition of humic compounds is estimated. A sharp increase in the share of the high molecular weight fraction in the preparations of HAs of arable podzolic soil by 2–4 times compared with the HAs of virgin podzolic soils was noted, which is due to the cultivation of the arable horizon, the nature of the incoming plant residues and the increased microbiological activity of the developed soils. The effect of acidity of the medium on the character of chromatograms of FA preparations isolated from the main types of soils of the Komi Republic was studied. It has been shown that in the region of high pH values of the eluent 9–13, the absence of fractionation is associated with the association of FAs, a change in their conformation, and the effect of “over-exclusion”. Elution with distilled water (pH = 6.5) allows the separation of FAs into two fractions with molecular weights ≥ 5 kDa and 1–2 kDa.

The effects of silt fields of Bortnytska aeration station on ecological state of land and water in the adjacent areas

The article highlights the results of research on assessing the ecological state of the land near the silt fields №1 and №3 of Bortnytska aeration station in the Zolochiv village community of Boryspil district in Kyiv region. The presence of previously recorded increased content of heavy metals in soils compared to the background content, both in terms of their gross content and the content of mobile forms was confirmed within the certain areas near the silt fields. For the elements-pollutants (Zn, Cu, Cr, Pb) at some points within the agricultural land, exceeding the values ​​of their gross content and the content of mobile forms (Zn, Cu) of the maximum permissible concentrations was recorded at 1.1-6.2 and 1.1 -2.6 times, respectively. The average values ​​of heavy metals content for floodplains (settlement) and agricultural land near silt fields indicate their prevailing values ​​for the latter in almost all elements, as well as exceeding the background values ​​and maximum permissible concentrations for the land where silt deposits were previously applied as fertilizers. Within the surveyed areas, soils are classified as unsalted, but the increased content of exchangeable magnesium may adversely affect soil fertility. Increased mineralization and content of ammonium and nitrates in groundwater are observed near silt fields, which is obviously related to the impact of silt water and can lead to deterioration of groundwater quality in the area of ​​their transit and discharge, in particular within the village Gnidyn. The area of ​​land with an extremely dangerous pollution rate in terms of total heavy metal is about 300 hectares, with a dangerous pollution rate is 260 hectares, and the estimated damage from crop failure may be 1.65 million UAH/year and 0.3 million UAH/year respectively. Within the areas adjacent to the silt fields, the condition of soils, water resources, cultivated products and the health of the population should be constantly monitored, especially when using the polluted land for agricultural use or housing.