Soil Acidification, Mineral Neoformation and Heavy Metal Contamination Driven by Weathering of Sulphide Wastes in a Ramsar Wetland

Past waste disposal practices have left large volumes of sulphidic material stockpiled in a Ramsar wetland site on the Atlantic coast of southwestern Spain, leading to severe land degradation. With the aim of addressing this legacy issue, soil core samples were collected along two transects extending from the abandoned stockpiles to the adjacent marshland and subjected to XRD, SEM-EDS, ICP-OES and ICP-MS analyses. Sulphide oxidation has been shown to be a major driver of acid generation and metal leaching into the environment. The marsh soil receiving acid discharges from the sulphide wastes contains elevated levels (in mg kg−1) of Pb (up to 9838), As (up to 1538), Zn (up to 1486), Cu (up to 705), Sb (up to 225) and Tl (up to 13), which are retained both in relatively insoluble secondary minerals (mainly metal sulphates and oxides) and in easily soluble hydrated salts that serve as a transitory pool of acidity and available metals. By using a number of enrichment calculation methods that relate the metal concentrations in soil and their baseline concentrations and regulatory thresholds, there is enough evidence to conclude that these pollutants may pose an unacceptable risk to human and ecological receptors.

Studies on plant-parasitic nematodes associated with sweet potato (Ipomoea batatas L., Lam.) in Gombe State, Nigeria

Sweet potato (Ipomoea batatas L., Lam.) is one of the most frequently eaten food crops. Its production is affected by plant-parasitic nematodes as well as biotic factors. This study was conducted to document the different plant-parasitic nematodes (PPN) that limit the gainful production of sweet potato in Gombe State. Thirty soil core samples per hectare were collected at random from sweet potato farms in the three local government areas (Nafada, Kaltungo, and Yamaltu Deba) of Gombe state. The Whitehead and Hemming method and identification keys were used for the soil extraction and genera identification of the plant-parasitic nematodes respectively. A total of 15 plant-parasitic nematodes were recovered throughout the surveyed areas among which 7 are considered major nematode pests of global importance. Irrespective of the surveyed locations, Meloidogyne spp., was found to record the highest population density and prevalence value. The frequency of occurrence in Y/Deba and Nafada LGAs shows that Meloidogyne spp., wasthe most occurring (32 %) genera. In Kaltungo LGA however, Scutellonema spp., and Rotylenchusspp., were the most occurring (17 %) genera. There was a high similarity percentage (≥ 68 %) of PPN genera where 8 genera (Scutellonema spp., Nacobbus spp., Pratylenchus spp., Meloidogyne spp., Heterodera spp., Xiphinema spp., Trichodorus spp., and Rotylenchus spp.) were found to be common amongst the surveyed locations. This is the first report of plant-parasitic nematodes associated with sweet potato in Gombe state, Nigeria. Hence, it is critical to educate farmers in the regions about their effects on the crop and how to successfully manage them.

Bearing Characteristics of Diaphragm Wall Foundation under Vertical and Combined Load

To investigate the bearing characteristics of diaphragm wall foundation under combined load, the results from elasto-plastic analyses of 3D finite element models (FEM) were presented in this study. The vertical load of the diaphragm wall foundation is borne by inner and outer side resistance, resistance of soil core and the end of wall, respectively. Moreover, the sum of end resistance and soil core resistance accounts for about 75% of the vertical load. The mobilization mechanism and distribution of side resistance of the foundation were also analyzed. It is clarified that the mobilization characteristics of inner and outer side resistance of the wall are completely opposite. Due to the combined load, the horizontal load has an amplification effect on the settlement of the foundation. Additionally, the calculation methods of the Eight-component Winkler spring model and rigid pile displacement were used for determining the vertical load-bearing capacity and the overturning stability. A comparison between results from the FEM and the theoretical calculation methods showed that the results of the numerical simulation properly coincided with that of the displacement solution of theoretical model. The conclusions obtained by the above methods all indicate that the foundation has the characteristics of overall overturning failure under the combined load.

Estimation of soil carbon storage under mono-specific Enhalus acoroides meadows in Pari Island, Indonesia

Large seagrass meadows in Indonesia are predicted to have a significant ability in capturing and storing carbon and are useful to mitigate global climate change. However, most of the available data are derived from short-term carbon storage of living biomass, whereas data on long-term carbon storage in the soil is still limited. This study, therefore, aims to measure soil carbon storage in mono-specific Enhalus acoroides meadows in Pari Island. A total of nine soil cores was collected in a 100×100 m2 area. The parameters were soil depth, dry bulk density (DBD), and Corg content. We applied a PVC corer with 7.4 cm in diameter and 80 cm in length to collect the soil. The length of the soil core varied between 8 and 67 cm. The mean (±SE) of soil dry bulk density is 0.98±0.04 gr/cm3 and the median is 1.1 gr/cm3, while Corg content is 2.1±0.1% soil DW (mean±SE) and 1.9% (median). E. acoroides vegetation in Pari Island stores around 63 Mg Corg/ha organic carbon in 8-67cm or 34cm (mean depth) of topsoil. Carbon storage of these mono-specific meadows is comparable to soil carbon storage in the seagrass ecosystems per hectare areas on national, regional, and global levels.

Effects of calcium cyanamide on Collembola in a standardized field test: Part 1. Rationale and performance of the study

Background A field study lasting one year was performed to study the effects of a calcium cyanamide fertiliser (trade name: Perlka®) on Collembola in order to support the terrestrial risk assessment under the REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulation. Due to the lack of an appropriate guidance document, the design of the study was based on the ISO Guideline 11268–3, originally developed for earthworm field studies. However, the sampling procedure was adapted accordingly by applying ISO Guideline 23611–2, i.e. taking soil core and pitfall trap samples. Two groups of four plots each were treated with 200 kg/ha and 400 kg/ha Perlka®, respectively. A third group served as a fertiliser control, i.e. it was treated with a standard urea fertiliser (172.9 kg Piagran®/ha) at the same total nitrogen rate (79.5 kg/ha) as provided by the high Perlka® application rate. The fourth group served as negative control without any fertiliser treatment and the fifth group was treated with the reference item Agriclor® (480 g a.i./L chlorpyrifos), known to be toxic to springtails. Results In total 16 different Collembola species were determined. For seven species, covering all life form types, a reliable statistical evaluation was possible, which was reflected in correspondingly low MDD values in the study. A statistically significant decrease of the abundance (at least 50%) on the reference item plots compared to the untreated control was observed for six species, thus demonstrating the sensitivity of the Collembola community. Conclusion No long-lasting effects of the Perlka® application rates could be observed for any of the Collembola species. In order to support risk assessors in both industry and authorities in the interpretation of large and complex data sets typical for field studies with chemicals, further guidance on implementation and data interpretation is urgently needed.

Effects of Slope Aspect and Rainfall on Belowground Deep Fine Root Traits and Aboveground Tree Height

The vertical root distribution and rooting depth are the main belowground plant functional traits used to indicate drought resistance in arid and semiarid regions. The effects of the slope aspect on the aboveground traits are visible but not the belowground deep root traits. We aimed to investigate the fine root traits of the locust tree (Robinia pseudoacacia L.) planted on southerly and northerly aspects, and the variations in the rooting depth in regions with different rainfall, as well as assessing how deep rooting, might affect the response to drought in a loess region. We selected three study sites with different rainfall amounts, with six sampling plots at each site (three each with southerly and northerly aspects). Soil core samples were collected down to the depth where no roots were present. The locust trees tended to develop deeper fine roots rather than greater heights. The tree height and diameter were greater for locust trees on northerly aspects, whereas trees on southerly aspects had significantly deeper rooting depths. Fine root traits (root length, root area, and root dry weight density) were higher in the southerly aspect for both Changwu and Ansai, but lower in Suide. The ratio of the root front depth tree height ranged from 1.04 to 3.17, which was higher on southerly than northerly aspects, and it increased as the rainfall decreased. Locust tree growth traits (belowground fine root and aboveground tree height) were positively correlated with the mean annual rainfall. The soil moisture content of the topsoil decreased as the rainfall decreased, but the pattern varied in the deep layer. Our results suggest that the variations in the belowground rooting depth under different slope aspects may be related to plant survival strategies. The vertical extension of the rooting depth and tree height may be key functional traits that determine plant growth in drought-prone regions.

Migration of Chlorine in Plant–Soil–Leaching System and Its Effects on the Yield and Fruit Quality of Sweet Orange

Chlorine (Cl) is indispensable for the growth of plants. While rarely systematic reports are available for the effect of Cl-containing fertilizers on citrus production. This study aimed to investigate the impacts of various Cl-containing fertilizers on the nutrients in the leaves, the yield and quality of sweet orange, and the Cl migration in the plant–soil–leaching system. A 5-year field experiment (2016–2020) with five Cl treatments (0, 75, 150, 450, and 900 kg ha−1), and soil core lysimeter test with five Cl levels (0, 150, 225, 300, and 450 kg ha−1) were carried out. The results showed that 77.0% of Cl leached into above 60 cm deeper soil layer, with calcium as the main accompanying ions, resulting in less Cl being absorbed by the citrus plants. The content of Cl in the leaves and soil was enhanced by the increasing input of Cl-containing fertilizer, without yearly increased characteristics, under a mean annual rainfall of 1,474 mm. Chlorine significantly increased the yield (13.24–37.8 9%), fruit weight, and vitamin C (Vc), in addition to enhancing the flavor and the juice yield of sweet orange via improving the absorption of N and K. Moreover, the long-term application of potassium sulfate has elevated the accumulation of sulfur in the soil and in leaves; it is becoming a potential risk factor for citrus production. Taken together, the application of Cl-containing fertilizer in sweet orange is feasible, and trace absorbance of Cl could improve the yield and fruit quality of sweet orange.

Assessing the effect of topography on Cs-137 concentrations within forested soils due to the Fukushima Daiichi Nuclear Power Plant accident, Japan

Topographic effects on Cs-137 concentrations in a forested area were quantitatively examined using 58 soil core samples collected in a village in Fukushima, Japan, which was directly impacted by the radioactive plume emitted during the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. In this study, five topographic parameters and two soil properties were evaluated as controls on the soil Cs-137 concentration using generalized additive models (GAMs), a flexible statistical method for evaluating the functional dependencies of multiple parameters. GAMs employing soil dry bulk density, mass water content, and elevation explained 54 % of the observed concentrations of Cs-137 within this landscape, whereas GAMs employing elevation, slope, and upslope distance explained 47 % of the observed concentrations, which provide strong evidence of topographic effects on Cs-137 concentrations in soils. The model fit analysis confirmed that the topographic effects are strongest when multiple topographic parameters and soil properties are included. The ability of each topographic feature to predict Cs-137 concentrations was influenced by the resolution of the digital elevation models. The movement of Cs-137 into the subsurface in this area near Fukushima was faster in comparison to regions affected by the Chernobyl Nuclear Power Plant accident. These results suggest that the effects of topographic parameters should be considered carefully in the use of anthropogenic radionuclides as environmental tracers and in the assessment of current and future environmental risks due to nuclear power plant accidents.