Long-Term Biosolids Application on Land: Beneficial Recycling of Nutrients or Eutrophication of Agroecosystems?

The impact of repeated application of alkaline biosolids (sewage sludge) products over more than a decade on soil concentrations of nutrients and trace metals, and potential for uptake of these elements by crops was investigated by analyzing soils from farm fields near Oklahoma City. Total, extractable (by the Modified Morgan test), and water-soluble elements, including macronutrients and trace metals, were measured in biosolids-amended soils and, for comparison, in soils that had received little or no biosolids. Soil testing showed that the biosolids-amended soils had higher pH and contained greater concentrations of organic carbon, N, S, P, and Ca than the control soils. Soil extractable P concentrations in the biosolids-amended soils averaged at least 10 times the recommended upper limit for agricultural soils, with P in the amended soils more labile and soluble than the P in control soils. Several trace elements (most notably Zn, Cu, and Mo) had higher total and extractable concentrations in the amended soils compared to the controls. A radish plant assay revealed greater phytoavailability of Zn, P, Mo, and S (but not Cu) in the amended soils. The excess extractable and soluble P in these biosolids-amended soils has created a long-term source of slow-release P that may contribute to the eutrophication of adjacent surface waters and contamination of groundwater. While the beneficial effects of increased soil organic carbon on measures of “soil health” have been emphasized in past studies of long-term biosolids application, the present study reveals that these benefits may be offset by negative impacts on soils, crops, and the environment from excessive nutrient loading.

Assessment of the Transfer of Trace Metals to Spontaneous Plants on Abandoned Pyrrhotite Mine: Potential Application for Phytostabilization of Phosphate Wastes

The abandoned Kettara pyrrhotite mine (Marrakech region, Morocco) is a real source of acid mine drainage (AMD) and heavy metal pollution from previous mining operations—which has spread, particularly because of wind erosion. A store-and-release cover system made of phosphate wastes was built on the site for preventing AMD. To ensure the integrity of this cover and its durability, it is desirable to revegetate it (phytostabilization) with plants adapted to the edaphoclimatic conditions of the region. In this paper, a study was carried out on the spontaneous vegetation around the phosphate cover in order to consider the selection of plants to promote the stabilization of the Kettara mine tailings pond. Nine species of native plants with their rhizospheric soils growing in agricultural soils and tailings from the Kettara mine were collected, and metals (As, Cd, Co, Cu, Pb, Zn, Ni, Cr) were analyzed. The soil analysis showed that the tailings contained high concentrations of Cu (177.64 mg/kg) and Pb (116.80 mg/kg) and that the agricultural soil contained high concentrations of As (25.07 mg/kg) and Cu (251.96 mg/kg) exceeding the toxicity level (Cu > 100 mg/kg, Pb > 100 mg/kg, As > 20 mg/kg). The plant analysis showed low trace metal accumulation in Scolymus hispanicus, Festuca ovina, Cleome brachycarpa, Carlina involucrata and Peganum harmala. These species had a bioconcentration factor (BCF) greater than 1 and a translocation factor (TF) less than 1, demonstrating a high tolerance to trace metals. Therefore, they are good candidates for use in the phytoremediation of the Kettara mine tailings. These species could also potentially be used for the phytostabilization of the phosphate waste cover of the Kettara mine, thus completing the rehabilitation process of this area.

Growth at the limits: comparing trace metal limitation of a freshwater cyanobacterium (Dolichospermum lemmermannii) and a freshwater diatom (Fragilaria crotonensis)

Freshwater phytoplankton blooms are increasing in prevalence and there are conflicting views on whether trace metals limit growth of key species and thus bloom formation. The Taupō Volcanic Zone (TVZ), New Zealand, was formed by multiple eruptions of a super-volcano which emitted rhyolitic tephra leaving lakes depleted in trace metals. This provides an opportunity to test the potential of trace metal limitation on freshwater phytoplankton growth under nanomolar concentrations. Growth responses of two algal species isolated from Lake Taupō, Dolichospermum lemmermannii (cyanobacteria) and Fragilaria crotonensis (diatom), to six biologically important trace metals (manganese, iron, zinc, cobalt, copper and molybdenum) were examined in culture experiments. These were conducted at three trace metal concentrations: (1) ambient, (2) two-times ambient, and (3) ten-times ambient concentrations in Lake Taupō. Elevated concentrations of iron significantly increased growth rates and maximum cell densities in D. lemmermannii, whereas no significant concentration dependence was observed for other trace metals. Fragilaria crotonensis showed no significant growth response to elevated concentrations of trace metals. These results highlight the importance of iron as a growth limiting nutrient for cyanobacteria and indicate that even small (twofold) increases in Fe concentrations could enhance cyanobacteria growth rates in Lake Taupō, potentially causing cyanobacterial blooms.

Trace Metal Dynamics in Shallow Hydrothermal Plumes at the Kermadec Arc

Hydrothermal vents are a source of many trace metals to the oceans. Compared to mid-ocean ridges, hydrothermal vent systems at arcs occur in shallower water depth and are much more diverse in fluid composition, resulting in highly variable water column trace metal concentrations. However, only few studies have focused on trace metal dynamics in hydrothermal plumes at volcanic arcs. During R/V Sonne cruise SO253 in 2016/2017, hydrothermal plumes from two hydrothermally active submarine volcanoes along the Kermadec arc in the Southwest Pacific Ocean were sampled: (1) Macauley, a magmatic dominated vent site located in water depths between 300 and 680 m, and (2) Brothers, located between 1,200 and 1,600 m water depth, where hydrothermalism influenced by water rock interactions and magmatically influenced vent sites occur near each other. Surface currents estimated from satellite-altimeter derived currents and direct measurements at the sites using lowered acoustic Doppler current profilers indicate the oceanic regime is dominated by mesoscale eddies. At both volcanoes, results indicated strong plumes of dissolved trace metals, notably Mn, Fe, Co, Ni, Cu, Zn, Cd, La, and Pb, some of which are essential micronutrients. Dissolved metal concentrations commonly decreased with distance from the vents, as to be expected, however, certain element/Fe ratios increased, suggesting a higher solubility of these elements and/or their stronger stabilization (e.g., for Zn compared to Fe). Our data indicate that at the magmatically influenced Macauley and Brothers cone sites, the transport of trace metals is strongly controlled by sulfide nanoparticles, while at the Brothers NW caldera wall site iron oxyhydroxides seem to dominate the trace metal transport over sulfides. Solution stabilization of trace metals by organic complexation appears to compete with particle adsorption processes. As well as extending the generally sparse data set for hydrothermal plumes at volcanic arc systems, our study presents the first data on several dissolved trace metals in the Macauley system, and extends the existing plume dataset of Brothers volcano. Our data further indicate that chemical signatures and processes at arc volcanoes are highly diverse, even on small scales.

Variation of Macro- and Microelements, and Trace Metals in Spring Wheat Genetic Resources in Siberia

Western Siberia is one of the major spring wheat regions of Russia, cultivating over 7 Mha. The objective of the study was to evaluate the variation of macro- and microelements, and of trace metals in four distinct groups of genetic resources: primary synthetics from CIMMYT (37 entries), primary synthetics from Japan (8), US hard red spring wheat cultivars (14), and material from the Kazakhstan–Siberian Network on Spring Wheat Improvement (KASIB) (74). The experiment was conducted at Omsk State Agrarian University, using a random complete block design with four replicates in 2017 and 2018. Concentrations of 15 elements were included in the analysis: macroelements, Ca, K, Mg, P, and S; microelements, Fe, Cu, Mn, and Zn; toxic trace elements, Cd, Co, Ni; and trace elements, Mo, Rb, and Sr. Protein content was found to be positively correlated with the concentrations of 11 of the elements in one or both years. Multiple regression was used to adjust the concentration of each element, based on significant correlations with agronomic traits and macroelements. All 15 elements were evaluated for their suitability for genetic enhancement, considering phenotypic variation, their share of the genetic component in this variation, as well as the dependence of the element concentration on other traits. Three trace elements (Sr, Mo, and Co) were identified as traits that were relatively easy to enhance through breeding. These were followed by Ca, Cd, Rb, and K. The important biofortification elements Mn and Zn were among the traits that were difficult to enhance genetically. The CIMMYT and Japanese synthetics had significantly higher concentrations of K and Sr, compared to the local check. The Japanese synthetics also had the highest concentrations of Ca, S, Cd, and Mo. The US cultivars had concentrations of Ca as high as the Japanese synthetics, and the highest concentrations of Mg and Fe. KASIB’s germplasm had near-average values for most elements. Superior germplasm, with high macro- and microelement concentrations and low trace-element concentrations, was found in all groups of material included.

Seasonal and Spatial Variation in Dissolved Heavy Metals in Liaodong Bay, China

Spatial–seasonal variations in dissolved heavy metals in surface seawater were analyzed based on surveys at 87 sampling sites and water samples from six rivers across Liaodong Bay. The concentrations of copper (Cu), lead (Pb), cadmium (Cd), and zinc (Zn) had ranges of 0.20–40.00 (5.45 ± 5.67), 0.51–33.64 (4.68 ± 3.93), 0.03–13.47 (2.22 ± 2.01), and 0.50–80.09 μg/L (14.22 ± 16.32), respectively, throughout the four seasons of 2020. The trace metal concentration showed a spatial gradient of high to low from river to estuary and from inshore to offshore areas. A combination of pollution levels and marine sensitivity was employed to assess the pollution degree of the heavy metals. As a whole, the single pollution factors of trace metals in Liaodong Bay were ranged in the order Pb > Zn > Cu > Cd. The total pollution degree was relatively high in autumn and summer due to increased riverine inputs after the rainy season, while relatively low in spring and winter. These findings provide baseline data for future targeting policies to protect marine environments in Liaodong Bay.

Acute and chronic toxicity of mixtures of bisphenol A and trace metals (Cd and Pb) to micro-crustacean, Daphnia magna

The occurrence of plastic additives and their ecological impacts have attracted much attention in recent years globally. Among plastic additives, the trace metals (e.g., Cd, Pb) are widely used as color pigments and stabilizers, whereas bisphenol A (BPA) is added to enhance the desired physical characteristics of plastic products. However, these additives can easily leach out of plastic materials and enter the aquatic environment causing risks to aquatic ecosystems. Although the toxicity of a single additive on various aquatic organisms has been studied, the responses of zooplankton exposed to the mixed plastic additives have not been fully understood. Therefore, this study aims to evaluate the effects of the binary mixtures (BPA+Cd, BPA+Pb) and trinary mixture (BPA+Pb+Cd) at the metal concentrations of 5 µg/L and BPA level of 50 µg/ L on the life history traits and food feeding rate of the freshwater micro-crustacean, Daphnia magna. The results showed exposures to these mixtures for 24h could significantly enhance the food feeding rate of D. magna from 2.5 – 5.8 times higher than the control. The survival rate was decreased from 50 – 90% in the organisms exposed to these mixtures after 18 incubated days. We found a synergistic effect of BPA+Pb but an antagonistic effect of BPA+Pb+Cd on the survivorship of D. magna. Similarly, the organisms in the exposures delayed their maturity age and reduced their reproduction. The potent impact order of the mixtures on D. magna was BPA+Cd > BPA+Pb+Cd > BPA+Pb. Our results evidenced the adverse effects of plastic additive mixtures on aquatic organisms. Therefore, the use and disposal of plastic materials and plastic additives should be paid more attention to protect the environment, ecosystem, and human health. Moreover, our findings proved that the toxicity of multi-contaminants on organisms could be unpredictable even the toxicity of a single contaminant is known.