Evaluation of anthropogenic contamination using sterol markers in a tropical estuarine system of northeast Brazil

Relationship between nitrate, heavy metal, and sterols contents in Japanese agricultural soils with risk of groundwater pollution

In Japanese agricultural lands, nitrate-nitrogen contamination of soil and groundwater often occurs due to the application of livestock excrements and compost. Therefore, rural soils in Japan were sampled and analyzed for nitrate-nitrogen leaching, heavy metal content, and sterols associated with livestock excrement and compost to calculate contamination risk indicators. The results were analyzed using self-organizing maps and cluster analysis. Nitrate-nitrogen content using water extraction was detected in most of the sampled soils. In addition, many samples from areas that were already severely contaminated with nitrate-nitrogen showed particularly high concentrations. Coprostanol, an indicator of fecal contamination, was detected in more than half of the samples. The main source of nitrate-nitrogen contamination in these areas is livestock excrement and compost. Self-organization maps showed that areas with high nitrate-nitrogen contamination also corresponded to areas with high copper and zinc soil contents. The self-organization maps and cluster analysis resulted in five clusters: a nitrate-contaminated group mainly originating from livestock excrement and compost, a heavy metal-contaminated group, a general group, a nitrate-contaminated group mainly originating from chemical fertilizers, and a contaminated group with potentially hazardous substances requiring attention. Authorities and decision-makers can use the results to prioritize areas requiring remediation.

Correlation between caffeine and coprostanol in contrasting Amazonian water bodies

The evaluation of contamination by domestic sewage is relevant in the Amazon region; however, it has neither been well-developed nor accompanied by research or monitoring programs. In this study, caffeine and coprostanol as indicators of sewage were investigated in water samples from Amazonian water bodies that crisscross the city of Manaus (Amazonas state, Brazil) and cover regions with distinct main land uses such as high-density residential, low-density residential, commercial, industrial, and environmental protection areas. Thirty-one water samples were studied based on their dissolved and particulate organic matter (DOM and POM) fractions. Quantitative determination of both caffeine and coprostanol was carried out using LC-MS/MS with APCI in the positive ionization mode. The streams of the urban area of Manaus had the highest concentrations of caffeine (1.47-69.65 μg L^-1) and coprostanol (2.88-46.92 μg L^-1). Samples from the peri-urban Tarumã-Açu stream and from the streams in the Adolpho Ducke Forest Reserve showed much lower concentrations of caffeine (20.20-165.78 ng L^-1) and coprostanol (31.49-120.44 ng L^-1). Samples from the Negro River showed a wider range of concentrations of caffeine (20.59-873.59 ng L^-1) and coprostanol (31.72-706.46 ng L^-1), with the highest values found in the outfalls of the urban streams. Levels of caffeine and coprostanol were significantly positively correlated in the different organic matter fractions. The coprostanol/(coprostanol + cholestanol) ratio proved to be a more suitable parameter than the coprostanol/cholesterol one in low-density residential areas. Proximity to densely populated areas and the flow of water bodies appear to influence the caffeine and coprostanol concentrations, which was observed in their clustering in the multivariate analysis. The results indicate that caffeine and coprostanol can be detected even in water bodies that receive very low domestic sewage input. Therefore, this study revealed that both caffeine in DOM and coprostanol in POM represent viable alternatives for use in studies and monitoring programs even in remote areas of the Amazon, where microbiological analyses are often unfeasible.

Linking eutrophication to carbon dioxide and methane emissions from exposed mangrove soils along an urban gradient

Mangroves are one of the most important but threatened blue carbon ecosystems globally. Rapid urban growth has resulted in nutrient inputs and subsequent coastal eutrophication, associated with an enrichment in organic matter (OM) from algal and sewage sources and substantial changes in greenhouse gas (GHG) emissions. However, the effects of nitrogen (N) and phosphorus (P) enrichment on mangrove soil OM composition and GHG emissions, such as methane (CH₄) and carbon dioxide (CO₂), are still poorly understood. Here, we aim to evaluate the relationships between CO₂ and CH₄ efflux with OM composition in exposed soils from three mangrove areas along watersheds with different urbanization levels (Rio de Janeiro State, Brazil). To assess spatial (lower vs. upper intertidal zones) and seasonal (summer vs. winter) variability, we measured soil-air CO₂ and CH₄ fluxes at low spring tide, analyzing elementary (C, N, and P), isotopic (δ¹³C and δ¹⁵N), and the molecular (n-alkanes and sterols) composition of surface soil OM. A general trend of OM composition was found with increasing urban influence, with higher δ¹⁵N (proxy of anthropogenic N enrichment), less negative δ¹³C, more short-chain n-alkanes, lower C:N ratio (proxies of algal biomass), and higher epicoprostanol content (proxies of sewage-derived OM). The CO₂ efflux from exposed soils increased greatly in median (25/75 % interquartile range) from 4.6 (2.9/8.3) to 24.0 (21.5/32.7) mmol m^-2 h^-1 from more pristine to more urbanized watersheds, independent of intertidal zone and seasonality. The CO₂ fluxes at the most eutrophicated site were among the highest reported worldwide for mangrove soils. Conversely, CH₄ emissions were relatively low (three orders of magnitude lower than CO₂ fluxes), with high peaks in the lower intertidal zone during the rainy summer. Thus, our findings demonstrate the influence of coastal eutrophication on global warming potentials related to enhanced heterotrophic remineralization of blue carbon within mangrove soils.

Steroid-based tracing of sewage-sourced pollution of river water and wastewater treatment efficiency: Dissolved and suspended water phase distribution

In this work, the environmental distribution of steroid compounds and the level of sewage-derived contamination were assessed using sterol ratios in the confluence area of two major rivers in the Serbian capital, where raw sewage is discharged without any treatment. Special attention was paid to steroids partitioning between the dissolved and suspended phases of river and wastewater samples, since steroids tend to easily bind to particulate matter. The efficiency of sterol removal in two wastewater treatment plants in Serbia was also evaluated. Human/animal sterols coprostanol and cholesterol, and phytosterol β-sitosterol were the dominant compounds in all water samples. The sterol abundance pattern in river water was different from that in raw sewage, indicating a more pronounced biogenic input, as well as greater impact of wastewater discharges on the composition of the suspended phase. Severe contamination of the investigated area was determined, with the Danube being more contaminated than the Sava River due to different hydrodynamic conditions leading to significantly higher sterol levels in the suspended particulate matter. It was also shown that the greater part of human/animal sterols and phytosterols present in river water samples (83.0 ± 11.9 % and 87.1 ± 15.2 %) and wastewater samples (92.1 ± 6.8 % and 95.0 ± 5.7 %) was bound to suspended material compared to the dissolved phase, emphasizing the need to consider and analyze both water phases in the tracing of steroid-based environmental pollution in order to obtain a realistic picture of steroid contamination and their fate in the aquatic environment. A high removal rate (>98 %) of coprostanol and cholesterol during wastewater treatment was determined and only the coprostanol/(coprostanol + cholestanol) ratio was found to be sensitive enough to be affected by an improvement in the quality of treated wastewater.

Fecal sterols as sewage contamination indicators in Brazilian mangroves

Recent sewage contamination in Brazilian mangrove forests was evaluated using fecal sterols as biomarkers and socioeconomic indicators. The sterols were quantified by gas chromatography/mass spectrometry (GC/MS). Total fecal sterol concentrations ranged between 2.50 2.50 and 39.03 μg g^-1 and coprostanol, between 0.23 and 6.97 μg g^-1. Mangroves located in less urbanized regions presented low coprostanol levels and low coprostanol/cholesterol and (5β/5β + 5α) stanol ratios in sediment, while urban mangrove forests presented moderate fecal contamination. In the latter, an intense contribution of untreated domestic effluents associated to metropolitan areas was noted, leading to a significant correlation between coprostanol concentrations and inadequate sanitation, reflecting environmental problems associated to disorderly urbanization processes coupled to the absence of an adequate urban infrastructure. However, even in metropolitan areas, fecal sterol levels did not reach those of highly contaminated regions, probably due to the intense and accelerated degradation process typical of tropical environments. However, this study highlights the importance of fecal contamination assessment in mangrove areas since the presence of untreated sewage in these ecosystems is an issue of public and environmental health.

Are Sterols Useful for the Identification of Sources of Faecal Contamination in Shellfish? A Case Study

This work aimed to identify the major source(s) of faecal pollution impacting Salcott Creek oyster fisheries in the UK through the examination of the sterol profiles. The concentration of the major sewage biomarker, coprostanol, in water overlying the oysters varied between 0.01 µg L−1 and 1.20 µg L−1. The coprostanol/epicoprostanol ratio ranged from 1.32 (September) to 33.25 (February), suggesting that human sewage represents the key input of faecal material into the estuary. However, a correlation between the sterol profile of water above the oysters with that of water that enters from Tiptree Sewage Treatment Works (r = 0.82), and a sample from a site (Quinces Corner) observed to have a high population of Brent geese (r = 0.82), suggests that both sources contribute to the faecal pollution affecting the oysters. In identifying these key faecal inputs, sterol profiling has allowed targeted management practices to be employed to ensure that oyster quality is optimised.

The impact of anthropogenic activity at the tropical Sergipe-Poxim estuarine system, Northeast Brazil: Fecal indicators

The individual concentrations and sources of sterols in sediments samples collected in two periods 2017 (dry period /March and rainy period/August) were determined along with the Sergipe-Poxim estuarine system, Aracaju, Brazil. The individual sterols concentration ranged from 135 to 21,746 ng g^-1 (March) and 191 to 144,748 ng g^-1 (August) and the distribution was mainly dominated by β-sitosterol in both periods with 37.2% (March) and 70.8% (August) of the total sterols found. In all the sampling sites, the coprostanol levels were higher than 100 ng g¹ (March) and 500 ng g^-1 (August), indicating sewage contamination. Diagnostic ratios between sterols suggested the predominance of sewage sources. Pearson correlation assessed a correlation significant (March) and negligible (August) between coprostanol concentration levels and organic matter. The principal component analysis (PCA) showed that the sterols levels influenced strongly C1, as well as C2 distinguished between the plant sterols and from sewage.

Influence of anthropogenic activities and risk assessment on protected mangrove forest using traditional and emerging molecular markers (Ceará coast, northeastern Brazil)

Anthropogenic molecular markers were used to assess chemicals inputs and ecological risks associated from multiple sources to sediments in one of the largest tropical mangrove forests of South America, with a particular focus on lesser studied compounds resulting from rural activities. Total concentrations ranged from 23.4 to 228.2 ng g^-1 for polycyclic aromatic hydrocarbons (∑_PAHs), 750.4 to 5912.5 ng g^-1 for aliphatic hydrocarbons (∑_AHs), 32.4 to 696.6 ng g^-1 for pesticides (∑_pesticides), 23.1 to 2109.7 ng g^-1 for coprostanol and sterols (∑_sterols), 139.3 to 580.2 ng g^-1 for naturals hormones (∑_{natural hormones}) and 334.1 to 823.4 ng g^-1 for synthetics hormones (∑_{synthetic hormones}). The PAHs and AHs used as traditional anthropogenic markers showed a mixture between natural and anthropogenic sources, related mainly to inputs from higher plants, phytoplankton and both, biomass and petroleum combustion. Rural activities linked to agricultural pest control are the predominant source of pesticides, although minor inputs from pesticides used in urban public health campaigns and household activities were also detected. Synthetic hormones levels are two to three orders of magnitude greater than natural hormones levels and no correlations were observed between the main sewage markers and synthetic hormone concentrations, rural activities such as animal husbandry, which use drugs in management, may be the predominant anthropogenic sources of these compounds in the region. Traditional markers failed to detect ecological risks in rural areas, where synthetic substances (e.g. pesticides and hormones) are widely used and introduced in the environment.

Sterol biomarkers and fecal coliforms in a tropical estuary: Seasonal distribution and sources

The Sergipe River estuary has been subjected to a range of anthropogenic activities including food, plastic, textile, ceramic and metallurgical production plants along with domestic sewage inputs, all of which are of environmental concern. In this study, the levels of fecal coliforms (FC) in surface water samples and sterols in superficial sediment samples collected from the Sergipe River estuary were determined. Based on the FC concentrations, 58% of the water samples were considered Water Potentially Unusable (WPU) according to the United States Environmental Protection Agency (USEPA). Concentrations of coprostanol ranged from 13 to 1072 ng g^-1, indicating a significant input of sewage at some points in the estuary. Principal Component Analysis (PCA) showed that there is no clear correlation between the coprostanol and coliform data, which may be due to the high resistance to degradation of coprostanol in sediments and to recent inputs of sewage at the water sample collection points.

Sewage contamination of Amazon streams crossing Manaus (Brazil) by sterol biomarkers

Sewage pollution is a principal factor of decreasing water quality, although it has not been considered a real impact in Amazonia that is still considered a pristine environment around the world. Thus, this study aimed to assess the levels of sewage contamination in sediments from three streams crossing Manaus - a Brazilian city of 2,403,796 inhabitants in the heart of the Amazon rain forest. Cholesterol, cholestanol, brassicasterol, ergosterol, stigmasterol, β-sitosterol, campesterol, stigmastanol, coprostanol, and epicoprostanol levels were determined by liquid chromatography tandem mass spectrometry (LC-MS/MS). The fecal indicator, coprostanol, was found in high concentrations (509-12 830 ng g^-1) and high relative proportions (21-54%) in all samples collected in the Mindu stream that crosses many heavily populated districts of the city, and in the Quarenta stream that crosses the Industrial District of Manaus. The sediments of the Tarumã-Açu stream also presented coprostanol; however, concentrations (<LOQ-142 ng g^-1) and relative proportions (0-7%) were much lower in this stream. Sterol ratios indicate a severe contamination of the urban streams (Mindu and Quarenta) and a low to moderate contamination of the partially urban stream (Tarumã-Açu). This is the first study evaluating the levels of sewage contamination of Amazon streams using sterol biomarkers and the results obtained herein indicate the need of an immediate implementation of effective sewage treatment strategies. Additionally, these findings may be considered as baseline concentrations for future monitoring programs of that globally important environment.

Polycyclic aromatic hydrocarbons in sediments of the Amazon River Estuary (Amapá, Northern Brazil): Distribution, sources and potential ecological risk

The distribution, sources and potential ecological risk of priority polycyclic aromatic hydrocarbons (PAHs) in sediment from the Amazon River Estuary (Macapá and Santana, Amapá, Northern Brazil) were investigated. The total PAHs concentration (∑PAH) ranged from 22.2 to 158.9 ng g^-1 dw (mean value 49.4 ng g^-1 dw). PAHs levels in the study area were relatively low than those in nearby areas and other coastal zones worldwide, and could be considered as baseline for PAHs in Amazonic sediments. PAHs ratios and the statistical analysis showed that fossil fuel and biomass combustions, primarily from local sources, were the dominant PAHs origins. The potential ecological risk was assessed on the basis of the sediment quality guidelines, and it was found that PAHs in the sediments of the Amazon River Estuary do not cause adverse effects on living organisms; however, the abundance of naphthalene and the presence of dibenzo[a,h]anthracene and benzo[a]pyrene deserve more attention.

Concentration, distribution and source apportionment of polycyclic aromatic hydrocarbons (PAH) in Poxim River sediments, Brazil

The individual concentrations, total amount and sources of 16 priority polycyclic aromatic hydrocarbons (PAH) in sediments collected along of the Poxim River, Aracaju, Brazil, were for the first time determined. The ΣPAH ranged between 2.2±1.5ngg^-1 and 28.4±6.9ngg^-1, with a mean value of 14.4±9.3ngg^-1. The Pearson correlation test and Principal component analysis (PCA) were used to assess the correlation between the PAH, organic matter and grain size; and to differentiate the sampling stations. Diagnostic ratios presented predominance of pyrogenic sources. Therefore, the PAH quantified showed the influence of anthropogenic activities near of the Poxim River.

Distribution and sources of sterol biomarkers in sediments collected from a tropical estuary in Northeast Brazil

The Piauí-Real estuary is located along the southern coast of Sergipe state, Northeast Brazil. This estuary has great economic importance due to its physical, biological, and socioeconomic diversity, but it is subject to anthropogenic stress since the resident population in the town bordered by the estuarine system has grown in recent years. Thus, the possibility of sewage contamination originating from the approximately 450,000 inhabitants living within its drainage basin was investigated in this study. Sediment samples were collected from 15 sampling stations along the estuarine system and extracted, followed by gas chromatography-mass spectrometry (GC-MS) analysis. Six sterols were quantified, indicating natural and anthropogenic sources. Coprostanol concentrations higher than 100 ng g^-1 were observed in 47 % of the stations analyzed, indicating sewage contamination, which was confirmed by the diagnostic ratios calculated. Based on the Pearson correlation test, a significant correlation between coprostanol concentrations and total organic carbon content (TOC) was observed, indicating that sterols record the history of sewage inputs in this area. These results indicate that control of the organic inputs into the estuarine system is required. Graphical abstract Sterol markers were determined and sources assessed in surface sediments from Piauí-Real estuarine system.