Peter Österholm

Åbo Akademi University · Department of Geology and Mineralogy

Imbalanced datasets are one of the main challenges in digital soil mapping. For these datasets, machine learning techniques commonly overestimate the majority classes and underestimate the minority ones. In general, this generates maps with poor precision and unrealistic results. Considering these maps for land use decision-making can have dire con...

Acid sulfate soils (ASS) cause big problems worldwide due to their potential to form sulfuric acid during oxidation of sulfidic materials, resulting in very acid soil (pH <4.0). Impacts include acidification of soil and water, leaching of metals, decreased nutrient supply, deterioration of water fauna and flora, and corrosion of infrastructure. The...

As critical transition zones between the land and the sea, estuaries are not only hotspots of hydrogeochemical and microbial processes/reactions, but also play a vital role in processing and transferring terrestrial fluxes of metals and nutrients to the sea. This study focused on three estuaries in the Gulf of Bothnia. All of them experience freque...

Flocculation of riverine dissolved organic matter to the particulate form in estuaries is an important mechanism for capturing dissolved metals to newly formed organic particles, regulating the metal transport from land to sea. The process is particularly relevant for rivers draining boreal acid sulfate soils of western Finland, which are known to...

Acid sulfate soils can cause environmental damage and geotechnical problems when drained or exposed to oxidizing conditions. This makes them one of the most harmful soils found in nature. In order to reduce possible damage derived from this type of soil, it is fundamental to create occurrence maps showing their localization. Nowadays, occurrence ma...

Flocculation of riverine dissolved organic matter to the particulate form in estuaries is an important mechanism for capturing dissolved metals to newly formed organic particles, regulating the metal transport to the sea. The process is particularly relevant for rivers draining boreal acid sulphate soils of western Finland, which are known to deliv...

Mine waters are a significant point source stressor for aquatic environments, not only due to their acidity and high metal concentrations, but also because of their high electrolyte concentrations. Ion-rich mine waters can disturb the seasonal mixing of lake waters, even leading to permanent stratification, i.e. meromixis. In this study, we investi...

Acid sulfate soils release metal laden, acidic waters that affect the environment, buildings, and human health. In this study, 16S rRNA gene amplicons, metagenomes, and metatranscriptomes all demonstrated distinct microbial communities and activities in the unoxidized potential acid sulfate soil, the overlying transition zone, and uppermost oxidize...

Sediments along the Baltic Sea coast can contain considerable amounts of metal sulfides that if dredged and the spoils deposited such that they are exposed to air, can release high concentrations of acid and toxic metals into recipient water bodies. Two river estuaries in western Finland were dredged from 2013 to 2018 and the dredge spoils were dep...

In Finland, acid sulfate (AS) soils are regarded as a serious environmental threat towards the Baltic Sea and watersheds situated in land areas that have emerged from the sea since the last glaciation due to glacial isostasy. The aim of this study is to compare the behavior of coarse-grained AS soil materials to the behavior of fine-grained AS soil...

Speciation of inorganic sulfur species, mainly pyrite and metastable iron sulfides by operationally defined methods, is widely used for risk assessment of acid sulfate soils by quantifying the acidity producing elements, as well as for general characterisation of marine sediments and subaqueous soils. “Traditional” sulfur speciation methods commonl...

Concern has been raised about the potential formation of acid sulfate soils and associated environmental problems related to peat extraction and, thus, peat, sediment and till characteristics of 15 well drained peat extraction fields were investigated in northern and northwestern Finland. The aim was to identify and characterize the occurrence/abun...

Rivers draining the acid sulfate soils of western Finland are known to deliver large amounts of trace metals with detrimental environmental consequences to the recipient estuaries in the eastern Gulf of Bothnia, northern Baltic Sea. However, the distribution of these metals in the coastal sea area and the relevant metal transport mechanisms have be...

Besides causing acidification, acid sulfate (AS) soils contain large nitrogen (N) stocks and are a potential source of N loading to waters and nitrous oxide (N2O) emissions. We quantified the stocks and flows of N, including crop yields, N leaching, and N2O emissions, in a cultivated AS soil in western Finland. We also investigated whether controll...

The concentrations, loads and speciation of rare earth elements (REEs) were studied in a 3.5 m thick mud depositional succession from an estuary in the Gulf of Bothnia. The uppermost 182.5 cm of the mud, estimated to have deposited from the early 1970s to 2011 (sampling year), had very high REE concentrations (596−1456 ppm) and accumulation rates (...

Due to discharge from acid sulfate (a.s.) soils, watercourses and coastal areas in the Gulf of Bothnia are periodically heavily acidified with high concentrations of potentially toxic metals. Data on water quality from 2005 to 2014 in an embanked lake, an estuary of four rivers in western Finland, showed repeated events with acidic water (pH < 5.5)...

Rivers draining the acid sulphate soils of western Finland are known to deliver large amounts of trace metals with detrimental environmental consequences to the recipient estuaries in the eastern Gulf of Bothnia, northern Baltic Sea. However, the distribution of these metals in the coastal sea area, and the relevant metal transport mechanisms have...

To efficiently mitigate bacterial mediated acid and metal discharge from acid sulfate soils, iron-and sulfur-oxidizing microorganisms that catalyze the iron sulfide dissolution should be inactivated. An organic carbon source could further be introduced into the soil to promote the growth of iron- and sulfur-reducing bacteria. In this study, acid su...

Some of the most economically valued soils for agricultural use are naturally occurring sulfide rich sediments. However, formation of acid sulfate soils with sulfuric materials (pH ≤ 4) can occur when sulfidic materials are exposed to air, which can then result in mobilisation of large amounts of acid and metals into nearby water bodies. In this st...

Mine waters are a significant point source stressor for the environment. Acid mine drainage has long been considered a big environmental issue, but recent studies suggest that the salinity of mine waters may also be harmful particularly to small, dimictic lakes which are abundant in e.g. Finland. The denser saline mine waters may cause a shift in t...

Naturally occurring sulfide rich deposits are common along the northern Baltic Sea coast that when exposed to air, release large amounts of acid and metals into receiving water bodies. This causes severe environmental implications for agriculture, forestry, and building of infrastructure. In this study, we investigated the efficiency of ultrafine-g...

Beryllium (Be) sources, transport and sinks were studied in a coastal landscape where acidic soils (acid sulfate soils) have developed after drainage of fine-grained sulfide-bearing sediments. The study included the determination of total abundance and speciation of Be in a variety of solid and aqueous materials in both the terrestrial and estuarin...

Acid sulfate (a.s.) soils have long been under investigation in Finland due to their negative impact on the environment. Earlier studies have mostly focused on fine-grained (< 63 μm) a.s. soil materials, but acidification caused by coarse-grained (≥ 63 μm) post-glacial a.s. soil materials has recently gotten more attention. Using a “let the soil sp...

Mitigating the acidic and metal-rich drainage from an acid sulfate soil in agricultural use is challenging. The approach we have chosen in the previous PRECIKEM project (2010-2014) and in the present PRECIKEM II project (2015-2018), is based on the fact that it is the soil layers below the plow layer, especially near drainage depth, that contribute...

A miniaturized sulfur speciation distillation method for reduced sulfur species that is inexpensive to manufacture, easy to use, has a low detection limit and can be used to analyse several samples simultaneously.

Leaching large amounts of acidity and metals into recipient watercourses and estuaries, acid sulfate (a.s.) soils constitute a substantial environmental issue worldwide. Mapping of these soils enables measures to be taken to prevent pollution in high risk areas. In Denmark, legislation prohibits drainage of areas classified as potential a.s. soils...

This study examines the spatial and temporal distribution patterns of arsenic (As) in solid and aqueous materials along the mixing zone of an estuary, located in the south-eastern part of the Bothnian Bay and fed by a creek running through an acid sulfate (AS) soil landscape. The concentrations of As in solution form (< 1 kDa) increase steadily fro...

Dissolved (<1 kDa) and colloidal (1 kDa-0.45 μm) size fractions of sulfate, organic carbon (OC), phosphate and 17 metals/metalloids were investigated in the acidic Vörå River and its estuary in Western Finland. In addition, geochemical modelling was used to predict the formation of free ions and complexes in these waters. The sampling was carried o...

Acid sulfate (a.s.) soil mapping constitutes a fundamental step in order to plan and carry out effective mitigation at catchment scale. The main goal of this study was to assess the use of an artificial neural network (ANN) based on a Radial Basis Function (RBF) for a.s. soil mapping and characterization of soil properties relevant for environmenta...

In Finland, poor water quality and associated ecological damage in the coastal streams related to land use on acid sulfate (a.s.) soils has been drawing a considerable amount of attention since the 1950’s. These soils originate from sulfide-bearing marine sediments mostly occurring in the coastal areas located below the highest shoreline of the for...

Potential acid sulfate soils contain reduced iron sulfides that if oxidized, can cause significant environmental damage by releasing large amounts of acid and metals. This study examines metal and acid release as well as the microbial community capable of catalyzing metal sulfide oxidation after treating acid sulfate soil with calcium carbonate (Ca...

Sulfide-bearing anoxic sediments are found in coastal regions around the world including Australia and the Baltic. Upon lowering of the groundwater by drainage, they are oxidized and form acid sulfate soils (pH < 4) that mobilize plenty of potentially toxic metals into watercourses with serious environmental consequences. Being highly valued for th...

Acid sulfate (AS) soils constitute a major environmental issue. Leaching considerable amounts of acidity and metals into watercourses, they cause severe ecological damage. Small hot spots may affect large areas of coastal waters and mapping is required in order to carry out an efficient mitigation plan. The primary aim of this study was to assess t...

Tutkimuksen päätavoitteina oli (1) selvittää sulfidisedimenttien esiintymisalueilla sijaitsevien turvetuotantoalueiden maaperän kuivatuksen aiheuttamaa valumavesien happamuus-kuormitusriskiä, (2) kehittää menetelmiä happamien kuormituspulssien ennakointiin ja seurantaan, (3) kehittää menetelmiä happaman kuormituksen neutralointiin ja (4) tarkastell...

The bioavailability of metals and their potential for environmental pollution depends not simply on total concentrations but on their chemical form. Consequently, knowledge of aqueous metal speciation is essential in investigating potential metal toxicity and mobility. Dissolved (<1 kDa), colloidal (1 kDa–0.45 μm) and particulate (>0.45 μm) size fr...

In Finland, acid sulfate (AS) soils constitute a major environmental issue. These soils leach considerable amounts of metals into watercourses, causing severe ecological damage. As small hot spot areas affect large coastal waters, mapping constitutes an essential step in the management of AS soil environmental risks (i.e. to target strategic places...

Soils containing an approximately equal mixture of metastable iron sulfides and pyrite occur in the boreal Ostrobothnian coastal region of Finland, termed "potential acid sulfate soil materials". If the iron sulfides are exposed to air, oxidation reactions result in acid and metal release to the environment that can cause severe damage. Despite tha...

This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity < 6‰). Surface water was collected in a transect from the creek mouth to the outer estuary, and settling (particulate) material in sedimen...

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using DECIPHER 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##

Sequences were screened for chimeras by the submitter using Decipher 1.1.2. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##