Silver nanomaterials (AgNMs) are released into sewers and consequently find their way to sewage treatment plants (STPs). The AgNMs are transformed en route, mainly into silver sulfide (Ag₂S), which is only sparingly soluble in water and therefore potentially less harmful than the original AgNMs. Here we investigated the toxicity and fate of different sulfidized AgNMs using an exposure scenario involving the application of five different test materials (NM-300K, AgNO₃, Ag₂S NM-300K, Ag₂S NM and bulk Ag₂S) into a simulated STP for 10 days. The sewage sludge from each treatment was either dewatered or anaerobically digested for 35 days and then mixed into soil. We then assessed the effect on soil microorganisms over the next 180 days. After 60 days, a subsample of each test soil was used to assess chronic toxicity in oat plants (Avena sativa L) and a potential uptake into the plants. The effect of each AgNM on the most sensitive test organism was also tested without the application of sewage sludge. Although Ag sulfidized species are considered poorly soluble and barely bioavailable, we observed toxic effects on soil microorganisms. Furthermore, whether or not the AgNM was sulfidized before or during the passage through the STP, comparable effects were observed on ammonium oxidizing bacteria after sewage sludge application and incubation for 180 days. We observed the uptake of Ag into oat roots following the application of all test substances, confirming their bioavailability. The oat shoots generally containing less Ag than the roots.

To better determine phytotoxicity thresholds for metals in the soil, studies should use actual field-contaminated soil samples rather than metal-spiked soil preparations. However, there are surprisingly few such data available for Cu phytotoxicity in field-contaminated soils. Moreover, these studies differ from each other with regards to soil characteristics and experimental setups. This study aimed at more accurately estimating Cu phytotoxicity thresholds using field-collected agricultural soils (Entisols) from areas exposed to contamination from Cu mining. For this purpose, the exposure to Cu was assessed by measuring total soil Cu, soluble Cu, free Cu2+ activity, and Cu in the plant aerial tissues. On the other hand, two bioassay durations (short-term and long-term), three plant species (Avena sativa L., Brassica rapa CrGC syn. Rbr, and Lolium perenne L.), and five biometric endpoints (shoot length and weight, root length and weight, and number of seed pods) were considered. Overall plant growth was best predicted by total Cu content of the soil. Despite some confounding factors, it was possible to determine EC10, EC25 and EC50 of total Cu in the soil. Brassica rapa was more sensitive than Avena sativa for all endpoints, while Lolium perenne was of intermediate sensitivity. For the short-term bioassay (21 days for all three species), the averaged EC10, EC25 and EC50 values of total soil Cu (in mg kg−1) were 356, 621, and 904, respectively. For the long-term bioassay (62 days for oat and 42 days for turnip), the averaged EC10, EC25 and EC50 values of total soil Cu (in mg kg−1) were 355, 513, and 688, respectively. The obtained results indicate that chronic test is a suitable method for assessing Cu phytotoxicity in field-contaminated soils.

The aim of the study was to determine the effect of soil contamination with diesel oil (0, 5, 10 and 15 mL/kg d.m. of soil) on the macroelement content (nitrogen, phosphorus, potassium, sodium, magnesium and calcium) in the above-ground parts of oats (Avena sativa L.). A remediation effect of sludge as a substance which reduces the negative impact of this petroleum product on its element content in oats was also evaluated. Sewage sludge was applied in doses 0, 4, 8 and 12 g/kg of soil. The macroelement content in the above-ground parts of oats depended on the soil contamination with diesel oil and on the addition of sewage sludge to the soil. Soil contamination with diesel oil caused significant changes in the content of all macroelements in the above-ground biomass of oats. Increasing doses of the petroleum product in the series without sewage sludge decreased the content of all macroelements, except phosphorus and calcium. The highest effect was observed for the content of sodium in oats. The addition of sewage sludge to the soil alleviated the negative impact of diesel oil on the chemical composition of the plants. The application of sewage sludge to soil resulted in an increase in average content of nitrogen, sodium and magnesium (as opposed to phosphorus and partly calcium) in the above-ground parts of oats, compared to the series without sewage sludge.

Successive applications of pig manure increase Cu and Zn contents in soils and may cause toxicity to plants. However, plants may have defense strategies that reduce Cu and Zn availability in rhizosphere soil. The study aimed to evaluate growth of white oats (Avena sativa) and Cu and Zn availability in rhizosphere soil subjected to long-term applications of pig slurry (PS) and pig deep litter (PL). The study was carried out with samples of a Typic Hapludalf soil from an 11-year experiment with annual fertilization of 180 kg N ha⁻¹ as pig slurry (PS180) and pig deep litter (PL180) and a control (C) treatment. White oats were grown in pots with soil collected at 0.0–0.10 m depth. Thirty-five and 70 days after emergence (DAE), rhizosphere (RS) and bulk soil (BS) were analyzed to determine Cu and Zn availability. Plant growth, tissue Cu and Zn concentration, and content (concentration X dry weight) were measured. The application of pig manure for 11 years increased available soil Cu and Zn, as well as tissue concentration and content. Dry matter yield and plant height in PL180 were similar to those found in plants grown in the control treatment, while plants grown in PS180 had higher dry matter than in C. We found few differences in soil chemical characteristics and Cu and Zn contents between RS and BS. The high Cu concentrations in roots, especially in soil treated with PL180, show that Cu retention in the roots prevents excess Cu transport to white oat shoots.

The aim of the study was to determine the effectiveness of soil application of manure, clay, charcoal, zeolite, and calcium oxide in remediation of soil polluted with cobalt (0, 20, 40, 80, 160, 320 mg Co kg⁻¹ of soil). The following were determined: weight of harvested plants as well as the content of cobalt in grain, straw, and roots of oat. In addition, tolerance index (Ti), cobalt bioconcentration (BCF), translocation (TF), and transfer (TFr) coefficients were derived. In the series without amendments, the increasing doses of cobalt had a significant effect by decreasing the yields of oat grain and straw and the mass of its roots. Also, lower tolerance index values were noted in the objects polluted with cobalt, especially with its highest dose. The application of manure had the strongest effect on increasing the mass of particular organs of the test plant, while the application of charcoal led to a significant decrease in this respect. The application of all substances to the soil, and especially manure and calcium oxide, resulted in higher tolerance index Ti values. The growing contamination of soil with cobalt caused a significant increase in the content of this element in oat and in the values of the translocation coefficient, in contrast to the effects noted with respect to the bioconcentration and transfer coefficients. All the substances applied to soil reduced the content of cobalt and its bioconcentration in oat straw, in opposition to grain and roots, limited its translocation, but elevated the transfer of this element from soil to plants. Soil contamination with cobalt promoted the accumulation of lead and copper in grain, cadmium, lead, nickel, zinc, manganese, and iron in straw, as well as cadmium, nickel, zinc, and manganese in oat roots. As the cobalt dose increased, the content of other trace elements in oat organs either decreased or did not show any unambiguous changes. Of all the tested substances, the strongest influence on the content of trace elements was produced by calcium oxide in straw and roots and by zeolite in roots, whereas the weakest effect was generated by manure in oat grain. Oat is not the best plant for phytoremediation of soils contaminated with cobalt.

Biological organisms, used as test objects in pollution tests may be as good, or even more so, in detecting soil contamination, than chemical analyses. In this study, we used five bioassay methods, together chemical and physical-chemical tests, for comprehensive environmental assessment of contaminated soils located at the industrial waste storage sites in North-West Russia. Examined soils have been contaminated with various toxic pollutants at various times in the past. The level of contamination by Hg, Pb, Cd, Zn, Со, As, Cr, Cu, Mn, V, and As in studied soils varied depending on a site type. The concentrations of these elements were 20 to 43 times higher than the regional geochemical baseline at all sites. The organic pollutants (3,4-benzo(a)pyrene and polychlorinated biphenyls) were found at some sites. Ecotoxicological studies were carried out using test organisms from different taxonomic groups: ciliates Paramecium caudatum Ehrenberg, green algae Scenedesmus quadricauda (Turp.) Brebisson, seeds of common oat Avena sativa L.,wheat Triticum aestivum L., and a natural community of microorganisms. All the employed bioassays revealed some of the aspects of contamination, supported or supplemented each other’s estimates, and gave excellent performance at the sampling sites.

The purpose of this study was to determine the effect of soil contamination with tri- and hexavalent chromium and soil application of compost, zeolite, and CaO on the mass of oats and content of nitrogen compounds in different organs of oats. The oats mass and content of nitrogen compounds in the crop depended on the type and dose of chromium and alleviating substances incorporated to soil. In the series without neutralizing substances, Cr(VI), unlike Cr(III), had a negative effect on the growth and development of oats. The highest doses of Cr(VI) and Cr(III) stimulated the accumulation of total nitrogen but depressed the content of N-NO₃ ⁻ in most of organs of oats. Among the substances added to soil in order to alleviate the negative impact of Cr (VI) on the mass of plants, compost had a particularly beneficial effect on the growth and development of oats. The application of compost, zeolite, and CaO to soil had a stronger effect on the content of nitrogen compounds in grain and straw than in roots. Soil enrichment with either of the above substances usually raised the content of nitrogen compounds in oats grain and straw, but decreased it in roots.

In previous studies, it was demonstrated that photocatalysis by TiO₂ nanoparticles can be effective for decomposition of pollen grains and pollen allergen extracts (PAEs) for Cupressus arizonica and Platanus hybrida species. In this work, the chemical and photochemical processes of five types of PAEs belonging to family Asteraceae, tribe Astereae, and family Poaceae, tribes Poeae and Triticea, were studied. It was confirmed that the PAEs suffered almost complete decomposition, which likely led to gaseous final products. For the species of Poeae tribe, i.e., Poa pratensis, Festuca pratensis, and Avena sativa, an unusual surface chemical modification of the photocatalyst consisting in the appearance of new bands on fine core level spectra of Ti 2p, C 1s, and O 1s was observed. These changes were associated with possible doping of TiO₂ with C and N by pollen extracts. This was accompanied by a red shift of absorption spectra. The results suggest that some components of Poeae pollen can be grafted on TiO₂ surface and they can activate the photocatalyst in the visible range. These findings can open a new pathway to eco-friendly chemical engineering of photocatalysts using organic biological compounds.