Erosion susceptibility mapping in the Central-Eastern Region of São Paulo in the last few decades.

Soil degradation has become a critical global environmental challenge as a result of rapid population growth, intensified erosion, and increased global warming. Depletion of nutrients, decreased infiltration, availability of water in the subsoil, silting, and eutrophication of surface water resources are directly associated with soil degradation. Water erosion is one of the primary causes of erosion. The principal objective of this study was to understand how climate change and land use have affected susceptibility to erosion in the central-eastern region of the state of São Paulo, Brazil, over the past few decades. Using the technique of multicriteria decision analysis and comparison of thematic layers in pairs, different factors that contribute to soil erosion were integrated in a GIS environment to map erosion hotspots. The results indicated increasing very high, high, and medium erosion susceptibility class percentage. Slope and soil types were the most sensitive factors; however, changes in land use, in particular, increased land cultivation and expanded areas highly susceptible to erosion in late 2019. The results of this study will assist in implementing soil conservation practices in such areas, reducing soil degradation, and increasing productivity.

Analysis of Susceptibility to Degradation of Water Ecosystem Services as a Tool for Land Use Planning: a Case Study in a Small Brazilian Watershed.

Mapping priority areas for environmental conservation and restoration is essential to informing policy formulation and decision-making. This study proposes a methodology based on multicriteria analysis and on-site assessment to develop environmental zoning that enhances the provision of water ecosystem services (WES) from Brazil's Água Quente River Basin. Integrated analysis of multiple criteria enabled identification of degrees of susceptibility to degradation, assessment of effects of land-use changes between 1990 and 2020, and validation of the study's methodology via field protocol. The results indicated that the spatial and temporal patterns of WES susceptibility to degradation varied little within the study area with the most critical levels occurring primarily in the Agua Quente's floodplain, where there are sandy textured soils and coverage with a low degree of soil protection. Zoning analysis designates 40% of the basin`s area as consolidated use, 28% for environmental conservation, 19% as anthropic use, and 13% for environmental restoration. Field analysis indicates that the occurrence of degraded areas and pollution by solid waste and urban effluents are relevant factors that affect the basin's water resources. Linear regression analysis indicated a good fit between the data modeled by the multicriteria analysis and those observed on-site (R² = 0.6 p < 0.05). The study's method is effective and its structure can be used in other river basins, as its approach is simple and flexible and can be readily adjusted to fit the characteristics of the study site.

Direct determination of Cu, Cr, and Ni in river sediments using double pulse laser-induced breakdown spectroscopy: Ecological risk and pollution level assessment.

Double pulse laser-induced breakdown spectroscopy (DP LIBS) has attracted much attention for analyzing trace elements due to its higher sensitivity when compared to single pulse laser-induced breakdown spectroscopy (SP LIBS). However, the development of quantitative methods in LIBS for the analysis of complex samples, such as sediments, is a great challenge due to the matrix effects that are very accentuated in this technique. In this study, different spectral treatments and calibration strategies were investigated to obtain calibration models that allow determinations with satisfactory accuracy and precision of Cr, Cu, and Ni in river sediments from different hydrographic basins. The best model developed for Cr was using MMC without spectral normalization and for Cu and Ni it was using MMC with spectral normalization, and using inverse regression, an increase in the accuracy of the determinations of all analytes was obtained. These models showed limit of quantification (LOQ) of 7.87 mg kg-1, 1.62 mg kg-1, and 2.21 mg kg-1 and root mean square error of prediction (RMSEP) of 7.54 mg kg-1, 14.53 mg kg-1, and 8.29 mg kg-1 for Cr, Cu, and Ni, respectively. Therefore, the models have adequate sensitivity and precision for the quantification of the potentially toxic elements (PTEs) evaluated, since, according to Brazilian legislation, the lower concentration of threshold effect level (TEL) for Cr, Cu, and Ni is <37.3 mg kg-1, <35.7 mg kg-1, and <18 mg kg-1, respectively. The concentrations of Cr, Cu, and Ni determined by DP LIBS allowed to obtain a partial ecological risk assessment of the studied sediments. Also, the chemometric tool Kohonen self-organizing map (KSOM) were used for data interpretation.

A computational tool for hydrosedimentological and statistical calculations / Ferramenta computacional para cálculos hidrossedimentológicos e estatísticos

ABSTRACT This paper presents a new computational tool called NH SEDIMENT AND STATISTIC which performs hydrosedimentological and statistical calculations using Visual Basic. This computational tool was developed for studies related to calculations of sediment transport in rivers. The tool includes hydrosedimentological methods for calculating suspension loads, bed loads, and total solid discharge. In addition, it provides the user with the possibility of performing statistical tests such as the Kolmogorov-Smirnov normality test, F test and χ2 test of variance, Student's t-test, non-parametric Wilcoxon test, and statistical parameter calculations. The NH SEDIMENT AND STATISTIC automatically calculates and provides the main results for each of the methods, allowing the user to draw their own conclusions. This proposed computational tool supports hydrosedimentological studies, and is reliable and easy to use, contributing to the reduction of sediment-related problems in the areas of hydraulic engineering, geology, and soil and water conservation. Furthermore, this tool may be used in transdisciplinary scientific areas for complete planning and management of water resources.

RESUMO Este artigo apresenta uma nova ferramenta computacional chamada NH SEDIMENT AND STATISTIC, que realiza cálculos hidrossedimentológicos e estatísticos usando o Visual Basic. Essa ferramenta computacional foi desenvolvida para estudos relacionados a cálculos de transporte de sedimentos em rios. A ferramenta inclui métodos hidrossedimentológicos para calcular cargas de suspensão, cargas de leito e descarga total de sólidos. Além disso, fornece ao usuário a possibilidade de realizar testes estatísticos, como o teste de normalidade Kolmogorov-Smirnov, teste F e teste de variância do χ2, teste T de Student, teste não paramétrico de Wilcoxon e cálculos estatísticos de parâmetros. O NH SEDIMENT AND STATISTIC calcula e fornece automaticamente os principais resultados para cada um dos métodos, permitindo que o usuário tire suas próprias conclusões. Essa ferramenta computacional proposta suporta estudos hidrossedimentológicos e é confiável e fácil de usar, contribuindo para a redução de problemas relacionados a sedimentos nas áreas de engenharia hidráulica, geologia, conservação de solo e água. Além disso, essa ferramenta pode ser usada em áreas científicas transdisciplinares para um planejamento e gerenciamento completos dos recursos hídricos.

Integrated empirical models to assess nutrient concentration in water resources: case study of a small basin in southeastern Brazil.

A significant contributor to water pollution is increased nutrient concentration that results in eutrophication. Modeling approaches are crucial to understanding the dynamics of nutrients in river basins. This study integrates empirical models into Geographic Information Systems to quantify total nitrogen and phosphorus (TN and TP) load and concentration in watercourses of Brazil's Lobo Stream Hydrographic Basin (LSHB). Land use, topographic, demographic, and hydrological data were used to simulate the load and concentration of nutrients generated by point and nonpoint pollution sources. The results indicate that the simulated TN and TP load is primarily generated by nonpoint sources, 81% and 76%, respectively. The Itaqueri River subbasin is the most critical, yielding more than half of the basin's TN and TP load. About 90% of annual LSHB point pollution load is generated in the Itaqueri River subbasin, principally from the Água Branca Stream. The linear regression between simulated and observed concentration indicates significant relationships (TN, r2 = 0.73 (p < 0.05), TP, r2 = 0.78 (p < 0.05)). The method used was able to simulate TN and TP concentration in watercourses, but was inconsistent for point pollution, indicating it represents the dynamics of nutrients in rural basins more effectively than in urban ones. The study shows that its methodology, despite limitations, enables scientists and managers to understand and predict spatial distribution of nutrient concentration in LSHB watercourses.

Total phosphorus determination in eutrophic tropical river sediments by laser-induced breakdown spectroscopy techniques.

Total phosphorus (TP) in sediments is an important chemical variable in the study of the extent of eutrophication in water bodies. Two methods, based on single pulse (SP) and double pulse (DP) laser-induced breakdown spectroscopy (LIBS), were developed for determining TP in the sediment cores of Brazilian rivers upstream from the Barra Bonita reservoir. TP concentration in the sediments was determined by inductively coupled plasma optical emission spectrometry (ICP OES) on digested samples. Besides, a LIBS system operating in SP and DP modes was used to develop methods for TP quantification in sediment pellets. In LIBS, the most appropriate wavelength to measure P was 214.91 nm. The calibration curves showed correlation coefficients of 0.93 and 0.92 and limits of detection of 709 mg kg-1 and 349 mg kg-1 for SP and DP LIBS, respectively. The two proposed methods were validated and the average percentage errors were 14% and 10% for SP and DP LIBS, respectively. The ICP OES and SP and DP LIBS data showed that the most superficial layers of the Piracicaba River, all the sedimentary layers of the Tietê River, and the confluence region present a high concentration of TP, according to the Brazilian sediment quality criterion. In conclusion, SP and DP LIBS were confirmed as promising alternative tools to traditional analytical methods for monitoring the TP content in the sediments that come from different hydrographic units. The proposed method using DP LIBS proved more sensitive than SP LIBS, but the SP LIBS method demonstrated enough precision for determining TP in eutrophic river sediments.

Evaluation of the impacts of climate change on streamflow through hydrological simulation and under downscaling scenarios: case study in a watershed in southeastern Brazil.

Among the problems related to water security, the effects of climate change on water availability stand out. Researchers have used hydrological models integrated with climate models in order to predict the streamflow behaviour in different hydrographic basins. This work aimed to analyse future climate scenarios for the Ribeirão do Lobo River Basin, located in the state of São Paulo, Brazil. The stochastic generator PGECLIMA_R was used in the simulation of climate data, which were used as input data in the hydrological model SMAP, after it was calibrated and validated for the study site. In all, five future scenarios were generated, with scenarios A, B, C and D projected based on the 5th report of the IPCC and scenario E based on the trend of climate data in the region. Among the scenarios generated, scenario D, which considers an increase of 4.8 °C in air temperature and a reduction of 10% in rainfall, is responsible for the worst water condition in the basin and can reduce up to 72.41% of the average flow and up to 55.50%, 54.18% and 38.17% of the low flow parameters Q90%, Q95% and Q7,10, respectively, until the end of the twenty-first century. However, the E scenario also becomes a matter of concern, since it was responsible for greater increases in temperature and greater reductions in rainfall and, consequently, more drastic monthly reductions in streamflow, which may negatively impact water resources and affect the various uses of water in the Ribeirão do Lobo River Basin.

A Method for Chlorophyll-a and Suspended Solids Prediction through Remote Sensing and Machine Learning.

Total Suspended Solids (TSS) and chlorophyll-a concentration are two critical parameters to monitor water quality. Since directly collecting samples for laboratory analysis can be expensive, this paper presents a methodology to estimate this information through remote sensing and Machine Learning (ML) techniques. TSS and chlorophyll-a are optically active components, therefore enabling measurement by remote sensing. Two study cases in distinct water bodies are performed, and those cases use different spatial resolution data from Sentinel-2 spectral images and unmanned aerial vehicles together with laboratory analysis data. In consonance with the methodology, supervised ML algorithms are trained to predict the concentration of TSS and chlorophyll-a. The predictions are evaluated separately in both study areas, where both TSS and chlorophyll-a models achieved R-squared values above 0.8.

Estimativa da erosão em carreadores de cana-de-açúcar através da Equação Universal de Perdas de Solo / Estimation of erosion in earth roads of sugar cane using Universal Soil Loss Equation

RESUMO A erosão do solo em carreadores de cana-de-açúcar é um problema que não pode ser desprezado, dado o aumento de área plantada com essa cultura no território brasileiro. No presente artigo, são estimadas as perdas de solo, através do emprego da Equação Universal de Perdas de Solo (EUPS), de quatro trechos de carreadores de cana de uma fazenda no município de Itirapina (SP). Os resultados mostraram estimativas de perdas que variaram de 60,6 a 90,1 t.ha-1 para o tipo de solo Neossolo Quartzarênico.

ABSTRACT Soil erosion in earth roads of sugar cane is a problem that cannot be ignored, given the increase in planted area to this crop in Brazil. In this article soil losses are estimated using the Universal Soil Loss Equation (USLE), at four stretches of sugar cane earth roads of a farm at Itirapina (São Paulo State). Results showed that loss estimates ranged from 60.6 to 90.1 t.ha-1 for typic Quartzipsamment soil.

The environmental quality of sediments of rivers near prospection areas of semiprecious rocks.

Mineral exploration areas are recognized for negatively affecting site environmental quality. The recent contaminations in the cities of Brumadinho, Mariana, Santo Antônio do Grama (Minas Gerais), and Barcarena (Pará) point to the seriousness of this issue in Brazil. However, studies on the influence of mining tailings from the extraction of semiprecious rocks on the quality of the sediments of water systems are rare. The aim of this study is to evaluate the influence of mining activities (amethyst, quartz, agate, calcite, and gypsum) on the quality of the sediments of Rio de Várzea, southern Brazil, the biggest region of amethyst rock extraction in the world. The concentrations of the chemical species Al2O3, SiO2, P2O5, K2O, CaO, TiO2, Fe2O3, Cr, Mn, Co, Cu, Zn, Zr, Ba, Cd, and Pb were determined by the technique energy-dispersive X-ray emission spectrometry (EDXRF). In the study, moderate contamination of the sediments of the Várzea River was demonstrated by means of background strategies (contamination factor, enrichment factor, and geoaccumulation index). Statistical analysis with the use of ANOVA, Tukey test, and principal component analysis revealed significant differences of concentrations of the chemical species of the sediments at the exit of the mining zone in relation to the other study areas.

Entropia na determinação da concentração de sedimentos em suspensão em reservatório / Entropy for determining the concentration of sediment in suspension in reservoir

RESUMO O sedimento encontrado na seção transversal de rios ou reservatórios é resultado das interações ocorridas em uma bacia hidrográfica, sejam elas decorrentes de fatores naturais ou antrópicos. Apesar da quantidade de sedimentos no rio ser o resultado dos processos que acontecem dentro da bacia, os métodos de estimativa de sedimentos baseados nessas características, ou seja, métodos determinísticos, apresentam grandes variações devido ao grande número de variáveis interferentes. Aqui foi aplicada a teoria da entropia, método não determinístico, para estimar o perfil da concentração de sedimentos a montante, a jusante e no interior de um reservatório, propondo a relação entre dois parâmetros com a finalidade de facilitar a estimativa. Foi verificado que é possível utilizar a teoria da entropia para simular o perfil de concentração de sedimentos em reservatórios. A utilização da relação entre os parâmetros facilita os cálculos, reduz o número de parâmetros modelados e, consequentemente, o tempo computacional, além de representar melhor as variações da concentração de sedimentos ao longo do perfil.

ABSTRACT The sediment found in the cross section of a river or a reservoir is the result of interactions that occur in a watershed, whether from natural or anthropogenic factors. There are still changes in the riverbed conditions depending on the type of sediment, flow velocity, changes in slope and human interventions such as hydraulic works. Although the amount of sediment in the river is the result of processes that occur within the basin, the estimation methods of sediment based on these characteristics, that is, deterministic methods, vary widely due to the large number of interfering variables. This paper deals with the application of the entropy theory, a non-deterministic method to estimate the profile of sediment concentration upstream, downstream and within a reservoir. A relationship between two parameters in order to facilitate the estimation was proposed. It can be observed that it is possible to apply entropy theory to simulate the sediment concentration profile in reservoirs. The use of the relationship between parameters facilitates calculations, reduces the number of modeled parameters and consequently the computational effort and better represents the variation of sediment concentration along the profile.