Pollution of soils with As, Cd, Co, Cr, Cu, Ni, Pb and Zn, collectively termed heavy metals (HMs), can threaten human health and ecosystem functioning. Therefore, polluted soils must be remediated. ...Soil washing of strongly polluted soils and phytoextraction on moderately polluted sites seem currently the most attractive remediation methods. Both methods depend on HM solubility (extractability), which can be increased by addition of ligands such as EDTA, NTA and other aminopolycarboxylic acids. As an alternative to these synthetic and environmentally questionable chemicals, the possibility of using naturally occurring dissolved organic matter (DOM) to extract the HMs from anthropogenic polluted soils is evaluated in this review based on mainly recently published laboratory studies. DOM isolated or extracted from soils consists of fulvic acid (FA) with up to 10% low-molecular-weight-organic-acids (LMWOAs), e.g. citric, oxalic and salicylic acids. In addition to soil DOM, results with other soluble humic substances and organic waste materials have been included, e.g. food wastes that after composting give useful LMWOAs.
Although generally less efficient than EDTA and NTA, the review clearly shows potential of DOM as HM extractant. Through its carboxylate and/or phenolate functional groups, DOM can form soluble complexes with Cd2+, Co2+, Cu2+, Ni2+, Pb2+ and Zn2+ (and other di- and trivalent cations). Extraction of anionic As(III), As(V) and Cr(VI) sorbed by soil solids, mainly amorphous Al and Fe oxides, is accomplished by DOM dissolution of the sorbents (oxides). In addition to the soil HM extraction potential, use of DOM will probably extract organic pollutants, stimulate microbial activity and improve soil structure. On the other hand, the efficiency of DOM to extract HMs (and other pollutants) seems to depend of numerous variables/factors including the specific HM, DOM and polluted soil as well as environmental (external) conditions such as pH, solution:soil ratio, extraction time and metal loading of the extractant. Furthermore, several different studies have shown conflicting (inconclusive) results, e.g. of pH and ageing effects on HM extractability. Therefore, much is still to be learnt about different DOM-HM-soil systems and their dependency of external factors. To create operational and safe guidelines for using DOM as HM extractant in relation to remediation of polluted field soils by phytoextraction or soil washing, considerably more precise knowledge is needed on influence of composition of different DOM samples and of characteristics of the polluted soils for extraction of the different HMs under various, clearly specified environmental conditions. If future investigations confirm the suitability of DOM in soil remediation, the next challenges will be upscaling to field conditions as well as to ensure availability of enough good quality DOM and to complete state-of-art economic analysis of using DOM in operational phytorextraction and soil washing.
•DOM has clear potential as heavy metal (HM) extractant in remediation of polluted soils.•DOM is a naturally occurring HM complexant (ligand).•DOM can extract cationic as well as anionic HMs.•DOM may improve soil fertility and plant growth.•DOM is a promising but yet rather unconfirmed polluted soil remediator.
Pyrrolizidine alkaloids (PA)s are natural toxins produced by a variety of plants including ragwort. The PAs present a serious health risk to human and livestock. Although these compounds have been ...extensively studied in food and feed, little is known regarding their environmental fate. To fill this data gap, we investigated the occurrence of PAs in ragwort plants, soils and surface waters at three locations where ragwort was the dominant plant species to better understand their environmental distribution. The concentrations of PAs were quantified during the full growing season (April–November) and assessed in relation to rain events. PA concentrations ranged from 3.2–6.6 g/kg dry weight (dw) in plants, 0.8–4.0 mg/kg dw in soils, and 6.0–529 μg/L in surface waters. Maximum PA concentrations in the soil (4 mg/kg) and water (529 μg/L) were in mid-May just before flowering. The average distribution of PAs in water was approximately 5 g/10,000 L, compared to the average amounts present in ragwort (506 kg/ha), and soil (1.7 kg/ha). In general, concentrations of PAs increase in the soil and surface water following rain events.
Display omitted
•Determine the potential of PAs in environmental samples: plant, soil and water•Co-relate the concentrations in soil and water with the plant growth/rain events•Scale and explain the distribution of PAs from plant into soil and water•Determine the frequency of individual PAs in all corresponded samples•Assess the risk of PAs contamination, where the plant and water sources meet
Display omitted
•Spatiotemporal distribution of 27 pharmaceuticals in the Chaobai River was studied.•Agriculture area presented the highest pharmaceutical concentrations.•The acute toxic pressure in ...river was mainly driven by caffeine.•Risk assessment highlights the necessity of controlling untreated wastewater.
This study investigated the occurrence of 27 pharmaceuticals with diverse physicochemical properties in a year-long monitoring campaign in the Chaobai River, China. The correlation between the distribution of pharmaceuticals in the river and the adjacent sources was elucidated. The results indicate that the agriculture area was the most polluted area with a median summed pharmaceutical concentration of 225.3 ng L−1, followed by the urban area and the mountain area with the corresponding values of 136.9 and 29.9 ng L−1, respectively. In terms of individual compounds, 22 out of 27 compounds were detected with concentrations ranging from <1 to 1972 ng L−1. Caffeine, carbamazepine, azithromycin, bezafibrate, metoprolol, sulfadiazine, sulfamethoxazole, clarithromycin, erythromycin, roxithromycin, and trimethoprim were pharmaceuticals with relatively high levels, with median concentrations ranging from 3.3 to 25.6 ng L−1 and detection frequencies ranging from 40% to 97%. Higher concentrations were mainly observed during cold seasons, with mean concentrations 1 to 52 times as high as those during warm seasons. Spatial analysis reveals that the pharmaceutical concentrations in different areas were impacted by different sources. A wastewater treatment plant was an important source in the urban area, while the agriculture area was impacted by various treated and untreated wastewater sources. The species sensitivity distribution model and risk quotient (RQ) method were combined in the ecological risk assessment. The results indicate that the multi-substance potentially affected fraction (msPAF) values of the sampling sites were below 0.04%, whereas nearly half of RQ values were higher than 1. Caffeine was proposed as a priority compound due to its high contribution rate (i.e., 79%) to the cumulative msPAF value, which implies that increased control and management of untreated wastewater sources along the Chaobai River is necessary.
Upgrades of wastewater treatment plant (WWTP) and full-scale application of additional advanced oxidation processes have been proven to be effective in reducing the nutrient emissions to the ...environment; however, the impacts of WWTP upgrades on the receiving waters with regard to the occurrence and ecological risks of pharmaceuticals are still unclear. In this study, 27 pharmaceuticals with diverse physicochemical properties were monitored in four rivers in Beijing, each of which was heavily impacted by a large-scale WWTP. Three-year sampling campaigns were conducted, covering the periods before and after the WWTP upgrades. The results show that the newly added combined treatment processes (e.g., biological filter, ultrafiltration, ozonation, and NaClO disinfection) reduced the total pharmaceutical concentrations in the effluents by 45–74%. The composition profiles reveal that the upgrades of two studied WWTPs resulted in a significant reduction of pharmaceutical concentrations in the receiving rivers, while little impacts were observed for the other rivers. The risk assessment shows that the acute toxic pressures in the studied rivers were generally low and the WWTP upgrades were conducive to reduce the risks for most of pharmaceuticals. However, erythromycin and ofloxacin still posed high risk, indicating the potential adverse effect of pharmaceuticals on aquatic environment.
Display omitted
•18 pharmaceuticals were detected in the four receiving rivers of sewage effluent.•Wastewater treatment plant upgrades reduced the pharmaceutical emissions.•After upgrades the pharmaceutical concentrations in receiving river decreased.•Erythromycin and ofloxacin still posed high risks after upgrades.•Control and management of untreated wastewater sources are necessary.
Phytotoxins are naturally produced toxins with potencies similar/higher than many anthropogenic micropollutants. Nevertheless, little is known regarding their environmental fate and off-field ...transport to streams. To fill this research gap, a network of six basins in the Midwestern United States with substantial soybean production was selected for the study. Stream water (n = 110), soybean plant tissues (n = 8), and soil samples (n = 16) were analyzed for 12 phytotoxins (5 alkaloids and 7 phytoestrogens) and 2 widely used herbicides (atrazine and metolachlor). Overall, at least 1 phytotoxin was detected in 82% of the samples, with as many as 11 phytotoxins detected in a single sample (median = 5), with a concentration range from below detection to 37 and 68 ng/L for alkaloids and phytoestrogens, respectively. In contrast, the herbicides were ubiquitously detected at substantially higher concentrations (atrazine: 99% and metolachlor: 83%; the concentrations range from below detection to 150 and 410 ng/L, respectively). There was an apparent seasonal pattern for phytotoxins, where occurrence prior to and during harvest season (September to November) and during the snow melt season (March) was higher than that in December–January. Runoff events increased phytotoxin and herbicide concentrations compared to those in base-flow conditions. Phytotoxin plant concentrations were orders of magnitude higher compared to those measured in soil and streams. These results demonstrate the potential exposure of aquatic and terrestrial organisms to soybean-derived phytotoxins.
Cropping of maize (Zea mays L.) on sandy soil in wet climates involves a significant risk for nitrogen (N) losses, since nitrate added in fertilizers or produced from residues and manure may be lost ...outside the period with active crop N uptake. This one-year lysimeter experiment investigated the potential of Vizura®, a formulation for liquid manure (slurry) with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP), to mitigate nitrous oxide (N2O) emissions and nitrate (NO3−) leaching from a coarse sandy soil cropped with maize. Maize followed grass-clover (Lolium perenne L.-Trifolium pratense L.) with spring incorporation and was fertilised with cattle slurry. A total of 12 treatments in triplicate were included in a factorial experiment with 1 m2 large and 1.4 m deep lysimeters: 1) with or without spraying the above-ground biomass of grass-clover with DMPP before incorporation; 2) application of cattle manure with or without DMPP, or no fertilization; and 3) natural rainfall or extra rain events to represent wet spring conditions, which were simulated with an automated and programmable irrigation system. Around 20 kg N ha−1 was returned to the soil in grass-clover above-ground biomass, and 145 kg N ha−1 in cattle manure. Cumulative annual N2O emissions ranged from 0.4 to 1.3 kg N ha−1, with between 49 and 86% of emissions occurring during spring. Manure application increased N2O emissions, while extra rainfall had no effect. The mitigation of N2O emissions by DMPP ranged from 46 to 67% under natural, and from 44 to 48% under high rainfall conditions. Total annual NO3− leaching ranged from 65 to 162 kg N ha−1. The extent of NO3− leaching to 1.4 m depth during spring was low, and instead most (72–83%) of total annual NO3−-N leaching was recorded during autumn before harvest. The extra rainfall during spring increased NO3−-N leaching in the pre-harvest period, but it is not clear to what extent this was associated with the N in grass-clover residues or manure applied in spring, or from N mineralisation below the root zone. Despite evidence for a reduction of NO3− leaching in three of four scenarios, overall this effect was not significant. No DMPP was detected in leachates. In conclusion, DMPP significantly reduced N2O emissions from cattle manure on this sandy loam soil independent of rainfall, while there was no significant effect on NO3− leaching. The results indicate that N2O emissions and NO3−-N leaching were partly derived from below-ground sources of N not affected by DMPP, which should be further investigated to better predict the mitigation potential of nitrification inhibitors.
•A lysimeter facility was used for growth of maize after grass-clover on coarse sandy soil.•The nitrification inhibitor DMPP reduced N2O emissions from manure irrespective of rainfall.•Simulation of extra rainfall during spring increased NO3- leaching irrespective of DMPP.•Treating grass-clover with DMPP before incorporation did not reduce N2O or NO3- leaching.•Analyses of DMPP in selected leachate samples did not show evidence for leaching losses.
Saponin-rich extracts from Quillaja saponaria and Chenopodium quinoa have been registered by US EPA as active ingredients in biopesticides, and extract from tea seed powder, Camellia oleifera has ...been proposed for biocidal use. If saponin-rich biopesticides are efficient against pests, they are most likely also bioactive in the aquatic environment against non-target organisms. The aim of this study was to conduct an effect assessment of saponin-rich plant extracts by using species sensitivity distributions based on acute toxicity tests. The maximal concentrations protecting 95% of the aquatic species (HC5) of saponins extracted from quillaja bark, tea seed coat and quinoa seed coat were 2.91 ± 1.00, 0.22 ± 0.11 and 22.9 ± 5.84 mg/L, respectively. The 100-fold difference in toxicity between the saponin-rich extracts from different plant species, indicate that saponin toxicity depends on the species it origins from, making “read-across” between saponins a dubious exercise. In addition, the predicted environmental concentrations of different saponins are close to or higher than their water quality standard, which means that the extracts might pose a risk to the aquatic environment if not used cautiously.
Display omitted
•Saponins are the main ingredients explaining toxicity of the saponin-rich plant extracts.•Worms, zebrafish and snail embryos are the most sensitive species for all saponins.•The species-specific type of saponins affect their toxicity, making “read-across” between saponins a dubious exercise.•Saponin-based biopesticides might pose a risk to the aquatic environment if not used cautiously.
The toxicity of saponin-based biopesticides depends on the plant species from which they are derived and might pose a risk to the aquatic environment if not used cautiously.
Low-molecular-weight (LMW) carboxylic acids found in soils and soil solutions comprise mainly aliphatic mono-, di- and tricarboxylic acids and substituted benzoic and cinnamic acids. This review ...compiles current information on the content of LMW carboxylic acids in soil solutions collected by centrifugation and in lysimeters, and soil extracts in relation to type of vegetation, soil type and soil depth. Contents of LMW carboxylic acids are highest in soil solution from the upper soil layers where carbon in LMW carboxylic acids constitutes up to 10% of DOC. The concentrations of aliphatic LMW di-/tricarboxylic acids (oxalic, malonic, malic, succinic, tartaric and citric acid) are usually in the range 0–50 μM with the higher concentrations in soil solutions from meadow, permanent pasture and forest soils as compared to ley and cultivated soils. In contrast, the concentrations of aliphatic LMW monocarboxylic acids (formic, acetic, propionic, butyric, valeric and lactic acid) are commonly in the range 0–1 mM with high concentrations found in soil solutions from both cultivated and forested soils. Especially insence cedar (
Calocedrus decurrens (Torr.) Florin), ponderosa pine (
Pinus ponderosa Dougl.), Douglas fir (
Pseudotsuga menziesii Franco) and Norway spruce (
Picea abies (L.) Karst.) seem to cause higher contents of LMW carboxylic acids in soils and soil solutions as compared to other tree species. Soil solution concentrations of substituted benzoic and cinnamic acids are submicromolar for all vegetations, whereas similar amounts in the range 0–800 μmol kg
−1 of aliphatic LMW carboxylic acids and substituted benzoic and cinnamic acids are extractable from mineral soils with alkaline and dilute acid extractants. Seasonal variations are observed in soil solutions isolated by centrifugation and soil extracts with highest concentrations in 2–4 months in a period from mid spring to early summer, minimum concentrations around early autumn, and increasing concentrations during autumn.
Pyrrolizidine alkaloids (PAs) are produced in plants as defence compounds against insects. PAs present a serious health risk to humans and livestock; therefore it is necessary to have a validated ...analytical method to monitor PAs in the environment. The objective of this work is to present an UPLC-MS/MS method for quantification of PAs in environmental samples of both soil and water. A fast, reliable, and sensitive approach is developed to identify and quantify PAs in soil and water. Sample preparation was performed by clean-up and pre-concentration of the samples using MCX solid phase extraction cartridges with full optimization, and then PAs were determined by UPLC coupled with TQ-MS. In the liquid chromatography, most of the parameters were optimized and tested including gradient time, solvents, additives, and pH of the mobile phases and flow rate. In addition, the MS parameters of cone voltage, desolvation temperature, cone flows, and collision energy were optimized. The instrument limit of detection (2-7 μg L
−1
) and limit of quantification (5-9 μg L
−1
) were determined experimentally, and the method was linearity validated up to 1000 μg L
−1
. The method was applied to analyse soil and surface water samples collected in April and May 2018 in Vejle, Borup, and Holte, Denmark. In total, 15 PAs were quantified and reported for the first time in environmental samples, in a range of 3-1349 μg kg
−1
in soil and 4-270 μg L
−1
in surface water.
Pyrrolizidine alkaloids quantified in soil and water.
While the Galápagos Islands have been renowned for their unique flora and fauna since the time of Charles Darwin, the soils of the isolated island chain have been mostly overlooked and little ...information on their heavy metal contents is available. The aim of this study was therefore to examine the total heavy metal (Cd, Co, Cr, Cu, Ni, Pb, U, Zn) contents of soils from the agricultural areas on islands Isabela, Santa Cruz and San Cristóbal, and identify trends with duration of exposure to weathering processes. Additionally, the mobility of these elements was assessed using ammonium nitrate extraction. In general, levels of Cd, Co, Cr, Cu, Ni and Zn were high compared to other world locations, while Pb levels were low and U levels were similar. Ni, Co, Cr, and to a lesser extent Pb and U tended to accumulate with increasing weathering duration. Soil concentrations of Cd, Zn, Cu, and possibly Pb and U, may have been influenced by use of agrochemicals, particularly on Santa Cruz Island. Mobility of Cd displayed an increasing trend with soil age, while Ni mobility decreased. Many soils had total contents of Cd, Co, Cr, Cu, Ni and Zn above threshold values indicating possible ecological or health risks. Systematic examination of trace element contents in soils from pristine national park areas would further assist in the delineation of background levels and the development of soil quality standards to ensure crop quality, animal and human health on this unique island chain.
•Total contents of Cd, Co, Cr, Cu, Ni & Zn were above threshold values in many soils.•Ni, Co and Cr tended to accumulate in the more weathered soils.•Cd mobility was highest in older soils, while Ni mobility was lowest.
PDF
