Atmospheric Chloride Deposition Research Articles

Interpretable data-driven prediction methods for atmospheric chloride deposition rate

Precise estimation of atmospheric chloride deposition is crucial in environmental science, providing valuable insights into atmospheric pollution, metal corrosion, and the hydrologic cycle. The distribution of atmospheric chloride deposition involves multiple processes of production, transportation, and deposition, making it a problem with well-defined physical mechanisms. Although numerous parametric models have been proposed for atmospheric chloride distribution prediction, they present challenges in terms of generalizability and prediction accuracy due to simplifications of the holistic process. In contrast, non-parametric machine learning algorithms can analyze complex issues and have good prediction performance, but they are used less often in atmospheric chloride deposition modeling. Therefore, we develop a genetic algorithm optimized quantile regression forest (GA-QRF) model, incorporating environmental variables associated with the holistic deposition process to predict the distribution of atmospheric chloride deposition. QRF is an ensemble learning method known for delivering precise and interpretable predictions, coupled with effective uncertainty estimation. The proposed model results achieved an R2 value of 0.935 for median prediction and 98.2% coverage of the intervals for uncertainty quantification on a dataset collected from six countries. In addition, in order to verify the consistency of the black-box machine learning model with the domain knowledge, several interpretation methods are used to deconstruct the proposed model. Considering the spatial variability of atmospheric chloride deposition, the proposed model was further used to create deposition distribution maps.

Spatio‐temporal distribution of atmospheric chloride deposition over a small island

AbstractEstimating chloride deposition rates is important for several applications. The conservative nature of chloride makes it a widely used natural tracer for hydrological investigations, such as groundwater recharge estimations and catchment salt balances. Additionally, chloride deposition is used to identify the sources and pathways of air pollutants as well as predict the likelihood of corrosion in infrastructures. The variability of atmospheric chloride (Cl−) deposition is a crucial consideration in hydrological investigations, particularly in coastal areas where it can fluctuate greatly. On small islands, spatial variations of chloride deposition have been found to be particularly strong, which may lead to large estimation errors when assuming point measurements are representative of larger areas. This paper aims to improve knowledge of the factors affecting chloride deposition's spatial and temporal variability in small islands using Norfolk Island (South Pacific) as a case study. A monitoring network consisting of 15 open‐site rainwater collectors was installed, from which 275 rainwater samples were collected for the period September 2020–July 2022. Total deposition rates for this period varied from 22.7 to 36.7 mg m−2 d−1 for sites located more than 400 meters from the coast. A higher variation is observed closer to the coast, with values varying from 50.9 to 1022.7 mg m−2 d−1 for sites located between 50 and 200 m from the coast. Statistical analysis shows that distance from the nearest point on the coast and elevation above sea level are significant factors contributing to spatial variability of chloride deposition, whereas period‐total rainfall depth and period‐average maximum daily wind gust speed significantly affect the temporal variability. This study contributes to knowledge on chloride deposition variability as well as the understanding of factors contributing to this variability in small islands. Additionally, a double exponential model for spatial distribution of chloride deposition in small islands is proposed.

Estimation of Groundwater Recharge in Makutupora Basin Located in a Semi-arid Region in Central Tanzania using Soil Moisture Balance (SMB) and Chloride Mass Balance (CMB) Techniques

ABSTRACT The objective of this study is to assess the groundwater recharge in the Makutupora basin, Central Tanzania using the soil moisture balance (SMB) and chloride mass balance (CMB) methods. The SMB method considered the estimation of both evapotranspiration in CROPWAT 8.0 software and surface runoff by the curve number (CN) method. The CN of the basin was determined based on hydrological soil group (HSG), antecedent moisture condition (AMC) and land use type using Arc GIS 10.2. Distributed land-use maps, slope and soil texture maps, daily climatological data (e.g., precipitation, temperature, wind speed, etc.), chloride concentration in rainfall and groundwater are the basic data used in this study. Input data were prepared in the form of digital maps using GIS and remote sensing tools and finally excel models were created to compute recharge using a set of given conditions. The results indicate that the average chloride concentration measured in the groundwater samples of the study area is 282.88 mg/L; much higher than the average concentration in rainwater samples which is 3.47mg/L while the average potential evapotranspiration is 2280 mm/year with an average rainfall of 680mm/year. Runoff computed using the CN method is ranging from 7.6-246mm/year or 0.68-22%. The final recharge from SMB is ranging from 0.025-117.86mm/year or 0.006-10% of annual rainfall equivalent to an average annual volume of 41.58Mm3 while recharge from CMB ranges from 2.57-44.6mm/year or 0.38-6.56% of annual rainfall equivalent to an average annual volume of 23.85Mm3. The results show that CMB underestimated the recharge compared to the SMB method. The reason for this is thought to be caused by the high chloride concentration analysed in groundwater compared to rainfall samples which may be caused by increased chloride concentration as water passes through the rock formations (unsaturated zone) to the saturated zone. Further lack of atmospheric chloride deposition data may be another contributing factor.

Estimation of atmospheric chloride deposition using new model based on the theory of perfect gases

Estimation of atmospheric chloride deposition using new model based on the theory of perfect gases

Atmospheric chloride deposition in field concrete at coastal region

A field research is carried out at atmospheric marine zones for evaluating the chloride deposition behavior of concrete structures under multiple geographic and environmental factors. Geographic factors of offshore distance, elevation, concrete surface orientation and building barrier, and environmental factors of temperature variation and rainfall on chloride deposition of concrete surface layer are evaluated. Our investigation demonstrates that chloride deposition content is significantly affected by offshore distance, elevation, and building barrier. Effect of concrete surface orientation on chloride deposition depends on the presence of building barrier. Besides, the large temperature variation and rainfall facilitate the chloride deposition.

Groundwater recharge assessment in an upland sandstone aquifer of southern California

The Chloride Mass Balance (CMB) method was used to obtain long-term recharge values for the Santa Susana Field Laboratory (SSFL) site, which features a groundwater flow system beneath an upland ridge formed of sandstone and shale beds in the Simi Hills, Ventura County, southern California. This application relied on the availability of on-site measurements of bulk atmospheric chloride deposition comprised of dry fallout and wet concentration, a large number of groundwater samples (∼1490) collected over three decades from 206 wells spanning a depth range from 10 to 360m, and measurements of chloride in surface runoff during rain events. The use of the CMB method is suited to the assessment of recharge for the study area because the mean chloride values in groundwater show minimal spatial trends, indicating no sources other than atmospheric. In addition, the Cl/Br ratio was used to exclude wells with possible anthropogenic chloride. The site-wide average recharge ranges between 1.8 and 9.5% of the mean annual precipitation (455mm) with a mean value of 4.2%. The measured surface runoff varies from 2.3 to 10.2% with mean value of 6.1% (28 mm) and, therefore, the volume of water lost to evapotranspiration is between 95.9 and 80.3% with a mean value of 89.6% (408mm). The long-term recharge calculated using the CMB method is consistent with tritium distribution based on a subset of groundwater monitoring wells and with an analysis of steady flow in the groundwater mound beneath the SSFL. Furthermore, the recharge value matches those in the literature for sandstone aquifers in arid and semi-arid climates. This recharge estimate has important relevance for site characterization in terms of constraining the volumetric groundwater flow rates and water balance and understanding the mechanisms of transport towards the water table. Moreover, this is the first application of the CMB in an upland area of California. Hence, the method is demonstrated to be robust and applicable to many upland bedrock areas in southern California and similar regions around the world, and can be used to quantify groundwater flow rates and supplies relevant to water resource management.

Estimación de la escorrentía superficial para el cálculo de la recarga a los acuíferos del macizo kárstico de los Ports de Beseit (Tarragona, España) combinando balance de agua en el suelo y análisis de hidrogramas de caudales

For the right estimation of aquifer recharge by precipitation surface taking into account runoff is particularly relevant. Non considering it in the estimation of the groundwater resources can overestimate them. In the Baix Ebre aquifer system, in southern Catalonia, the surface and vadose zone runoff produced in the karstified carbonate formations in the Ports de Beseit massif has to be evaluated in order to achieve a better estimation of the resources transferred from this massif to the Plana de La Galera plain. Starting from the conceptual hydrogeological model, the average annual runoff is estimated. It includes the discharge from temporal perched aquifers in the Ports de Beseit massif, in the Matarrana river basin, and in the SE watershed to the Plana de La Galera plain. This is performed by analyzing the river and tributaries hydrographs, the filling and emptying hydrographs of the Ulldecona reservoir, and the soil water balance using the Visual Balan code applied to obtain the runoff in the Ulldecona reservoir watershed. The runoff has been estimated about 105±20 mm·yr −1 , which represents 20–30% of average annual recharge in the Ports, estimated with soil water balance and atmospheric chloride deposition balance, about 350–500 mm·yr −1 , which is mostly transferred laterally to the Plana de La Galera plain.

Spatial variability of chloride deposition in a vegetated coastal area: Implications for groundwater recharge estimation

Summary Knowledge of atmospheric chloride deposition is a prerequisite for applying the chloride mass balance (CMB) method for groundwater recharge estimation. Compared to bare areas, vegetated areas can significantly enhance chloride deposition rates as the vegetation canopy provides a large surface onto which water droplets and aerosols settle. Although generally acknowledged, this effect has often been ignored in practical applications of the CMB method. This paper studies the variability of chloride deposition in a coastal basin characterised by a heterogeneous vegetation cover, and the implications of this variability for groundwater recharge estimation using observation wells in the saturated zone. The study area is located on the Eyre Peninsula in South Australia. The theory of the CMB method for groundwater recharge estimation is revised in the context of highly spatially variable chloride deposition. A GIS-based approach is developed for mapping the chloride deposition accounting for distance from the coast, distribution of vegetation and edge effects; the latter implying a lower chloride deposition inside a vegetation stand than at the edge. In order to quantify the significance of one or several of these effects for recharge estimation, different chloride deposition maps and corresponding recharge estimates are derived. Compared with the reference scenario that accounts for all effects, neglecting the coastal effect results in a 33–36% higher average recharge estimate, whereas neglecting the vegetation effect results in a 17–22% lower average recharge estimate. The latter numbers are likely to represent a lower bound of the impact of neglecting the vegetation effect. A critical factor for accurate determination of the influence of vegetation appears to be the edge effect, albeit its importance is subject to significant uncertainty that warrants further monitoring.

Evaluation of the atmospheric chloride deposition in the Danube hydrological zone of Bulgaria

Estimation of the long-term groundwater recharge based on the chloride mass balance method is easy for practical applications. This method is reliable only if the atmospheric chloride deposition is known. The direct measuring of this deposition is difficult and time consuming. In this study, the chloride deposition at the catchment scale is assessed based on the export of chloride with river waters (including baseflow), as the net groundwater recharge in the studied catchments is usually low, and its contribution to the exports of salts is insignificant. For the purpose of this study, a 25-year-long time series of discharge and chloride content (from 1951 to 1975) is processed, as the quality of river waters for this period is considered natural and unaffected by human activity in the studied catchments. The obtained value of the atmospheric chloride deposition for North Bulgaria is in the range of 2.5–2.8 g/m2/a based on representative stations. This is the first estimate of the atmospheric chloride deposition in the country, which may be used for assessment of the long-term groundwater recharge in North Bulgaria.

Atmospheric Corrosion of Reinforced Concrete Steel in Tropical Coastal Regions

The influence of atmospheric parameters and chloride deposition rate on concrete using an atmospheric corrosion approach is rarely found in literature. Seven exposure sites were selected in Havana, Cuba and two at Yucatan Peninsula, Mexico, to expose reinforced concrete samples. Two significantly different atmospheric corrosivity levels have been observed after two years of exposure in Havana depending on atmospheric chloride deposition and the w/c ratio of the concretes. Changes in corrosion current are in accordance with changes in chloride penetration and atmospheric chloride deposition. The influence of sulphur compounds deposition should be considered to study atmospheric corrosion of reinforced steel in concretes either in Havana.

Corrosion of steel reinforced concrete in the tropical coastal atmosphere of Havana City, Cuba

The influence of chloride deposition rate on concrete using an atmospheric corrosion approach is rarely studied in the literature. Seven exposure sites were selected in Havana City, Cuba, for exposure of reinforced concrete samples. Two significantly different atmospheric corrosivity levels with respect to corrosion of steel reinforced concrete were observed after two years of exposure depending on atmospheric chloride deposition and w/c ratio of the concrete. Changes in corrosion current are related to changes in chloride penetration and chloride atmospheric deposition. The influence of sulphur compound deposition could also be a parameter to consider in atmospheric corrosion of steel reinforced concrete.

Estimation of aquifer recharge by means of atmospheric chloride deposition balance

The measurement of the atmospheric chloride deposition on land allows the estimation of long-term average aquifer recharge when the average chloride content in the recharge water is known. This is a well-established, simple method, although not exempt from theoretical and practical difficulties. In spite of its potential, it is seldom applied. Under favorable circumstances, the results are reliable and the associated uncertainty can be determined. The chloride content of recharge water can be obtained from sampling the top of the water table. The method and its improvements have been the subject of extensive research and it has been applied to several aquifers throughout Spain, in the context of applied research projects and in doctoral thesis studies, by the Groundwater Hydrology Group of the Geoengineering Department of the Technical University of Catalonia (UPC). For aquifers discharging into springs or developed by means of deep wells, the vertical mixing of groundwater recharged at different altitudes is important. Thus, the chloride content may overestimate aquifer recharge and corrections are needed. In the present study the method has been developed and improved. It compares favorably to other methods, although it yields diverse recharge estimations that have to be referred to the appropriated site and time.

Estimation of aquifer recharge by means of atmospheric chloride deposition balance in the soil

En estat estacionari, la deposicio de clorur atmosferic sobre el terreny permet estimar la recarrega mitjana en els aquifers a llarg termini quan el contingut mitja de clorurs de l'aigua de recarrega es conegut. Es un metode senzill, ben conegut, pero no sense dificultats teoriques i practiques, malgrat que el seu potencial, sovint, no s'aplica. En circumstancies favora- bles els resultats obtinguts son fiables i permeten estimar-ne la incertesa. El contingut en clorurs de la recarrega es pot deduir del mostreig de la part superior del nivell freatic. El metode i la seva millora han estat l'objectiu de recerca i d'aplicacio en diversos aquifers i en tot el territori espanyol, com a part de projectes de recerca aplicada i de tesis doctorals lligades al Grup d'Hidrologia Subterrania del Departament d'Enginyeria del Terreny, Cartografica i Geofisica, de la Universitat Politecnica de Catalunya (UPC). En el cas d'aquifers que descarreguen en brolladors o son explotats mitjancant pous profunds, la mescla vertical de l'aigua recarregada a diverses altures es important, de manera que la recarrega estimada a partir del balanc de clorurs pot ser notablement sobrevalorada i cal fer-hi correccions. El metode es pot comparar favorablement amb els altres metodes per a avaluar la recarrega, encara que cadascun proporciona estimacions de la recarrega diferents, que s'han de considerar en el context apropiat de lloc i temps.

Atmospheric chloride deposition in continental Spain

AbstractThe atmospheric bulk deposition rate of chloride in continental Spain was studied to get basic information in order to help in the evaluation of diffuse recharge to aquifers through an environmental chemical balance. Both new, recent data and bibliographic data have been used. Most sampling records are less than 5 years long and often only 1 year long. This means that the calculated mean yearly bulk deposition rate of chloride is quite uncertain by 30% on average, and larger than the values derived form records up to 15 years long. A map of atmospheric bulk deposition of chloride has been drawn using ordinary kriging. The mean bulk deposition rate of chloride varies from 1 to 30 g m−2 year−1 in coastal areas, with strong negative landward gradients between 0·1 and 1 g m−2 year−1 km−1. In the centre of the Iberian Peninsula, chloride deposition rates vary from 0·2 to 0·5 g m−2 year−1, with gradients around or less than 5 × 10−3 g m−2 year−1 km−1. The coefficient of variation of the mean bulk atmospheric deposition rate of chloride, for any place, ranges from 0·1 to 1. Values larger than ∼0·5 are not a good indicator of natural uncertainty for this series of data that has a skewed distribution. The map of bulk deposition rate and its error is one of the terms needed for aquifer recharge estimation by means of the chloride ion balance. Copyright © 2008 John Wiley & Sons, Ltd.