Stochastic Assessment of Groundwater Contamination Risks From Onshore Gas Development Using Computationally Efficient Analytical and Numerical Transport Models

Regulators require the gas industry to assess the risks of unintentional release of chemicals to the environment and implement measures to mitigate it. Industry standard models for contaminant transport in aquifers do not explicitly model processes in the unsaturated zone and groundwater models often require long run times to complete simulation of complex processes. We propose a stochastic numerical-analytical hybrid model to overcome these two shortcomings and demonstrate its application to assess the risks associated with onshore gas drilling in the Otway Basin, South Australia. The novel approach couples HYDRUS-1D to an analytical solution to model contaminant transport in the aquifer. Groundwater velocities and chemical trajectories were derived from a particle tracking analysis. The most influential parameters controlling solute delivery to the aquifer were the soil chemical degradation constant and the hydraulic conductivity of a throttle soil horizon. Only 18% of the flow paths intercepted environmental receptors within a 1-km radius from the source, 87% of which had concentrations of <1% of the source. The proposed methodology assesses the risk to environmental assets and informs regulators to implement measures that mitigate risk down to an acceptable level.

Deep soil ploughing for afforestation: a review of potential impacts on soil and vegetation

Deep ploughing—which inverts, covers, or mixes soil organic layer (forest floor) and surface mineral A horizon into the mineral subsoil, burying the upper soil horizon in deeper layers, and disrupting pedogenic processes—is a debatable topic in forest plantation management. Overall, this review article aimed to identify the impacts of deep ploughing on the properties of forest plantations, adapting experiences from the agricultural sector. This paper examines the main impacts of deep ploughing technology on soil physical, chemical, and biological properties, ground vegetation, and tree aboveground and belowground biomass in afforested former agricultural land. Analysis of the published literature shows that deep ploughing can be used under different climatic and soil conditions, but it induces site-specific changes in soil properties and vegetation. Mechanical site preparation during afforestation and reforestation should follow the requirements of sustainable soil management, in order to avoid negative effects on the environment and biodiversity. Based on this analysis, we suggest key indicators that may be specific to deep ploughing responses in afforested sites and can contribute to risk assessment, aimed at achieving sustainable forest management. To date, most studies on mechanical site preparation for forest plantation have been performed using a few conifer tree species; therefore, it is important to expand empirical studies.

The Use of Artificial Neural Network and Advanced Statistics to Model Sediment Yield on a Large Scale: Example of Morocco

Morocco ranks among countries with the greatest achievements in the field of dams in Africa but is affected by the sedimentation phenomenon due to soil erosion in upstreams. The assessment of Sediment Yield (SY) and Suspended Sediment Yield (SSY) remains a challenging global issue, especially in Morocco, characterized by a great diversity of morphological, climatic, and vegetation cover. The main objective of this paper was to perform advanced statistics and artificial neural networks (ANN) in order to understand the spatial distribution of sediment yield and the factors most controlling it, including factors of the RUSLE model (Revised Universal Soil Loss Equation). In order to produce a model able to assess SY, we collected and analyzed extensive data of most variables that can be affecting SY using 42 catchments of the biggest and important dams of Morocco. Statistical analysis of the studied watersheds shows that SY is mainly related to the watershed area and the length of the drainage network. On the other hand, the SSY is higher in watersheds where gully erosion is abundant and lower in areas with no soil horizon. The SSY is mainly related to the altitude, aridity index, sand fraction, and drainage network length. In front of the complexity of preserving this phenomenon, the ANN was applied and gave very good satisfactory results in predicting the SSY (NSE=0.93, R2=0.93).

CONTRIBUTION TO KNOWLEDGE ON THE VARIABILITY OF AROLLA PINE WOODLANDS OF THE NORTH-EASTERN TATRA MOUNTAINS

Knowledge of the overall syntaxonomic and habitat variability of forest communities with Arolla pine (Pinus cembra) within the Tatra Mountains (Western Carpathians) is still insufficient as field research was hindered by their hardly accessible localities and deforestation for high mountain grazing. Arolla pine woodlands were traditionally classified within the association Pino cembrae-Piceetum Myczkowski et Lesinski 1974, but recent surveys recognize more numerous units. Hitherto unpublished releves from the north-eastern part of the Tatra Mountains document the occurrence of several floristically and ecologically distinct Arolla pine communities: (1) acid woodland of Homogyno alpinae-Pinetum cembrae on nutrient-poor habitats over quartzitic bedrock, and (2) calcareous woodlands of species-poor Pyrolo rotundifoliae-Pinetum cembrae of sites with a well-developed, tangled humus soil horizon, Cystopterido montanae-Pinetum cembrae on habitats influenced by both limestones and quartzites, Primulo elatioris-Pinetum cembrae bound to sites with the most favourable humidity, and Seslerio tatrae-Pinetum cembrae with the most pronounced calcareous character.

Effect of agrochemicals on spatio-temporal changes in soil agrochemical properties and yield of broccoli

The aim of the study. The aim of the study was to examine the effect of agrochemicals (mineral and organo-mineral fertilizers, plant growth regulators and ameliorants) on the spatio-temporal changes in the properties of agro-gray soil and broccoli yield using a cartographic approach. Methodology. The field experiment was conducted in 2016 at the site located near the Bykovo village in the south-east of West Siberia (54°58 '02.8" N; 83°5'21.45" E, Novosibirsk region). The objects of the study were the agro-gray soil (Luvic Retic Greyzemic Phaeozem (Siltic, Aric)) and the medium-ripe broccoli cabbage variety "Linda". The experiment scheme included the following treatments: (1) Control (without fertilizers), (2) Background (N100P60K160), (3) Background + succinic acid, (4) Background + dolomite, (5) Background + mulch, (6) Organo- mineral fertilizer "Criall". Soil samples were analyzed for the content of organic carbon, nitrates, total, mineral and organic phosphorus, as well as its mobile form; exchangeable potassium, calcium and magnesium, and pH. The dried samples of broccoli inflorescences were analyzed forthe total content of nitrogen, phosphorus, potassium, calcium and magnesium.Main results. After applying agrochemicals and harvesting broccoli, the variation coefficients of рН, mobile phosphorus, potassium and calcium increased by two or more times. The use of agrochemicals increased the yield and improved the nutritional value of broccoli inflorescences. The treatments with mineral fertilization(2, 3, 4 and 5) the treatment 2 (Background N100P60K160) provided the greatest return. The application of the studied agrochemicals resulted in the negative (acidification, binding of phosphorus, calcium and magnesium) and positive (increase in the content of elements) effects. The immobilization of nutrients (phosphorus, calcium, magnesium) in poorly soluble soil compounds and the respective decrease in the content of the elements’ mobile forms did not have a negative effect on the elemental composition of broccoli inflorescences. Thus, chemical immobilization, leading to the fixation of nutrients in the upper soil horizon, prevents their leaching by melt- and rainwater into the lower horizons.

Dynamics of carbon loss from an arenosol by a forest/vineyard land use change on a centennial scale

Few studies have focused on arenosols with regard to soil carbon dynamics despite the fact that they represent 8 % of the world's soils and are present in key areas where food security is a major issue (e.g. in Sahelian regions). As for other soil types, land use changes (from forest or grassland to cropland) lead to a loss of substantial soil organic carbon (SOC) stocks and have a lasting impact on the SOC turnover. Here we quantified long-term variations in carbon stocks and their dynamics in a 80 cm deep Mediterranean Arenosol that had undergone a land use change from forest to vineyard over more than 100 years ago. Paired-sites of adjacent plots combined with carbon and nitrogen quantification and natural radiocarbon (14C) abundance analyses revealed a stock of 50 GtC ha−1 in the 0–30 cm forest soil horizon, which was reduced to 3 GtC ha−1 after long-term grape cultivation. TOC in vineyard was dramatically low, with around 1 gC kg−1 and no vertical gradient as a function of depth. 14C showed that deep ploughing (50 cm) in vineyard plot redistributed the remaining carbon both vertically and horizontally. This remaining carbon was old carbon (compared to that of the forest), which had a C : N ratio characteristic of microbial OM and was probably stabilized within organomineral associations. Despite the drastic degradation of the OM pool in this Arenosol, this soil would have a high carbon storage potential if agricultural practices, such as grassing or organic amendment applications, were to be implemented within the framework of the 4 per 1000 Initiative.

Environmental properties of Phaeozems humus horizons of the Voronezh upland oak forest (Russia)

Within Voronezh city there is a green zone, the core of which are forest clusters of natural origin. The study sites are located in the recreational area of an upland oak forest. In such conditions, the forest litter and the upper soil horizon first experience transformation. All results were processed by StatSoft STATISTICA for Windows 10.0. In this study we found that low-thickness forest litter was formed in the Voronezh oak forest, in which the average content of macronutrients was (%): C – 2.91, N – 1.11, K – 0.32, and P – 0.18. These elements can be arranged in a variation series C > N > K > P. It is established that the edaphotope of oak forests of the forest-steppe has a favorable regime for the destruction of organic substances and the accumulation of decomposition products. The content of macronutrients in the forest litter and the upper part of the humus horizon is arranged in the same row N > K > P, which indicates their genetic relationship. The obtained data on the ecological state of the forest litter and the humus horizon of the gray forest soils of the oak forests of the megalopolis are important for understanding the biological cycle under conditions of technogenic and recreational loads.