Comparing the effect of Cu-based fungicides and pure Cu salts on microbial biomass, microbial community structure and bacterial community tolerance to Cu

The effect of Cu on three different microbial endpoints was studied using different Cu sources, in order to check the usefulness of pure Cu salts to estimate the toxicity of commercial Cu fungicides on soil microbes. Cu additions caused similar dose-response curves of substrate induced respiration (SIR) decreases regardless of Cu source, i.e. the use of pure Cu salts to estimate the effect of Cu fungicides on microbial biomass using SIR may be useful. Phospholipid fatty acid (PLFA) analysis showed that the Cu source was more important for the microbial community structure than Cu concentration. Thus, the use of Cu salts to infer the effects of Cu fungicides on microbial community structure using PLFA analysis is not recommended, since effects of Cu concentration will be confounded with Cu source. Analyzing pollution induced community tolerance (PICT) to Cu showed that the use of pure Cu salts may overestimate Cu effects if Cu salt additions modified the soil pH. The highest doses of Cu salts increased bacterial community tolerance to Cu between 300 and 600 times, while commercial Cu fungicide increases were between 20 and 160 times. Therefore, the use of pure Cu salts to estimate the Cu fungicides effects on soil microbes is not recommended for PLFAs analyses, not suitable for PICT at high Cu concentrations, while useful for SIR.Xunta de Galicia | Ref. ED431F 2018/06Agencia Estatal de Investigación | Ref. RYC-2016–2041

Assessment of polluted soil remediation using bacterial community tolerance to heavy metals as an indicator

The assessment of remediation on metal-polluted soils is usually focused on total and/or bioavailable metal content. However, these chemical variables do not provide direct information about reductions in heavy metals pressure on soil microorganisms. We propose the use of bacterial communities to evaluate the efficiency of three remediation techniques: crushed mussel shell (CMS) and pine bark (PB) as soil amendments and EDTA-washing. A soil sample was polluted with different doses of Cu, Ni, and Zn (separately). After 30 days of incubation, the remediation techniques were applied, and bacterial community tolerance to heavy metals determined. If bacterial communities develop tolerance, it is an indicator that the metal is exerting toxicity on them. Soil bacterial communities developed tolerance to Cu, Ni, and Zn in response to metal additions. After remediation, bacterial communities showed decreases in bacterial community tolerance to Cu, Ni, and Zn for all remediation techniques. For Cu and Ni, soil EDTA-washing showed the greatest reduction of bacterial community tolerance to Cu and Ni, respectively, while for Zn the soil amendment with PB was the most effective remediation technique. Thus, bacterial community tolerance to heavy metals successfully detect differences in the effectiveness of the three remediation techniques.Ministerio de Economía y Competitividad | Ref. CTM2015-73422-JINMinisterio de Economía, Industria y Competitividad | Ref. RYC-2016-20411Región de Murcia | Ref. 21525/EE/21Xunta de Galicia | Ref. ED401A-2020/08

Effects of military training, warfare and civilian ammunition debris on the soil organisms: an ecotoxicological review

Abstract Civilian and military activities are sources of water and soil contamination by inorganic and organic contaminants caused by shooting practices, warfare, and/or mechanized military training. Lead poisoning and contaminant bioaccumulation due to spent shots or other related military contaminants have been widely studied for mammals, birds, and plants. Although there are different papers on the impact on earthworms, information on micro and mesofauna (i.e., collembola, nematodes, etc.) is still scarce. Here, we review the published data regarding the impact of civilian and military shooting activities, including war-impacted areas, focusing on soil organisms, from microbial communities to the ecotoxicological effects on terrestrial organisms. One hundred eleven studies were considered where earthworms and enchytraeids were widely studied, especially under ecotoxicological assays with Pb and energetic-related compounds from military explosives. There is a lack of information on soil organism groups, such as mites, ants, or gastropods, which play important roles in soil function. Data from combined exposures (e.g., PTEs + TNT and PTEs + PAHs) is scarce since several studies focused on a single contaminant, usually Pb, when combined contaminants would be more realistic. Ecotoxicological assays should also cover other understudied ammunition elements, such as Bi, Cu, or W.Agencia Estatal de Investigación | Ref. IJC2020-044197-IAgencia Estatal de Investigación | Ref. IJC2019-042235-IAgencia Estatal de Investigación | Ref. RYC2022-036752-IXunta de Galicia | Ref. ED431C2021/46-GRCUniversidade de Vigo/CISU

Dissolved organic matter as a confounding factor in the determination of pollution-induced community tolerance (PICT) of bacterial communities to heavy metals using the leucine incorporation method

PICT methodology using the leucine incorporation method (Leu-PICT) is useful for assessing heavy metal contamination in soils. First, bacterial community is exposed to metal in the soil (selection phase), developing tolerance if metal exerts toxicity. Secondly, in detection phase, bacterial suspensions are obtained, and tolerance is quantified by a second exposition of bacterial community to the metal using Leu-PICT methodology. However, during detection phase when Leu-PICT is performed, some characteristics of bacterial suspensions may change metal bioavailability. We assess the influence of dissolved organic matter (DOM) in bacterial suspensions, as humic acids (HA), on Leu-PICT determination to Cr, Cu, Ni, Pb and Zn. Results showed that the presence of HA in bacterial suspensions causes underestimations of bacterial community tolerance to Cr (increasing Cr toxicity), and overestimations of bacterial community tolerance to Cu, Ni, Pb, and Zn (reducing metal toxicity). In addition, the magnitude of these overestimations was different depending on the metal.Xunta de Galicia | Ref. ED401A-2020/084Ministerio de Economía y Competitividad | Ref. CTM2015-73422-JINFinanciado para publicación en acceso aberto: Universidade de Vigo/CISU

Use of metal nanoparticles in agriculture. A review on the effects on plant germination

Agricultural nanotechnology has become a powerful tool to help crops and improve agricultural production in the context of a growing world population. However, its application can have some problems with the development of harvests, especially during germination. This review evaluates nanoparticles with essential (Cu, Fe, Ni and Zn) and non-essential (Ag and Ti) elements on plant germination. In general, the effect of nanoparticles depends on several factors (dose, treatment time, application method, type of nanoparticle and plant). In addition, pH and ionic strength are relevant when applying nanoparticles to the soil. In the case of essential element nanoparticles, Fe nanoparticles show better results in improving nutrient uptake, improving germination, and the possibility of magnetic properties could favor their use in the removal of pollutants. In the case of Cu and Zn nanoparticles, they can be beneficial at low concentrations, while their excess presents toxicity and negatively affects germination. About nanoparticles of non-essential elements, both Ti and Ag nanoparticles can be helpful for nutrient uptake. However, their potential effects depend highly on the crop type, particle size and concentration. Overall, nanotechnology in agriculture is still in its early stages of development, and more research is needed to understand potential environmental and public health impacts.Xunta de Galicia | Ref. ED431C 2021/46-GRCMinisterio de Ciencia e Innovación | Ref. PID 2021-124497OA-I00Xunta de Galicia | Ref. ED481B-2022-081Ministerio de Ciencia e Innovación | Ref. IJC 2019-042235-IMinisterio de Ciencia e Innovación | Ref. IJC 2020-044197-IUniversidade de Vigo/CISU

Soil abandonment as a trigger for changes in Zn fractionation in afforested former vineyard acidic soils

Zinc is an essential element for plant nutrition, but it may cause toxicity depending on its bioavailability and potential transformation in soil. In vineyard soils, high concentrations of Zn are usually found, mainly due to agricultural practices. However, a great abandonment of vineyards has recently occurred, leading to changes in the total and bioavailable Zn concentrations, as well as Zn fractionation. We analyzed Zn concentrations (total, ZnT, and bioavailable, ZnED) and fractionation in the soil of three paired sites (PM, PT, and AR) up to depths of 50 cm in active and adjacent abandoned vineyards that were already transformed into forests. The ZnT averaged at 210 mg kg−1 among all studied vineyards. The results showed changes in the vertical pattern ZnT concentrations after vineyard abandonment at the PM and PT sites, while at the AR site, no great variation occurred. The ZnED (mean values = 7 mg kg−1) decreased after abandonment at PM and AR in the uppermost surface layers, while it increased in the top 10 cm at the PT site, reaching up to 60 mg kg−1. Regarding Zn fractionation in active vineyards, the residual fraction (ZnR) was the most abundant, followed by Zn bound to crystalline Fe and Al oxy-hydroxides (ZnC) and Zn bound to soil organic matter (ZnOM). After abandonment, the ZnR slightly increased and the ZnC slightly decreased at the PM and AR sites at all depths, while the ZnOM showed a noticeable variation in the uppermost 10 cm of the PT site. These results suggest that the soil organic matter that is provided during afforestation may play an important role in Zn fractionation and mobilization, depending on its humification degree and chemical stability. Zn mobilization could result in a positive nutrient supply for plants, but caution must be taken, since an excess of Zn could cause toxicity in long-term abandoned vineyards.Xunta de Galicia | Ref. ED431C2021/46-GRCAgencia Estatal de Investigación | Ref. JC2020-044426-IUniversidade de Vig

Copper accumulation and fractionation in vineyard soils from temperate humid zone (NW Iberian Peninsula)

The occurrence of total Cu and Cu fractions (exchangeable Cu, Cu bound to organic matter, Cu bound to amorphous inorganic materials, Cu bound to crystalline Fe and Al oxides and residual Cu) was studied in 170 surface layers of soils from seven vineyard regions located in the NW Iberian Peninsula (Rías Baixas, Ribeira Sacra, Ribeiro, Monterrei, Valdeorras, O Bierzo and Vinhos Verdes). The data showed that long-term application of Cu-based fungicides has led to increased concentrations, mainly in superficial vineyard soil layers. Thus, 64% of the samples showed total Cu levels higher than 100 mg kg 1, threshold for soil contamination. Total Cu content in Ribeiro (248 ± 130 mg kg 1) and Ribeira Sacra (259 ± 118 mg kg 1) soils were significantly higher than those observed for the rest of the vineyard regions (169 ± 90, 139 ± 122, 115 ± 42, 103 ± 42 and 100 ± 48 mg kg 1 in Valdeorras, Rías Baixas, O Bierzo, Vinhos Verdes and Monterrei, respectively). Cu distribution among various soil fractions also differed between winegrowing regions; however, in general, Cu in these vineyard soils is present mainly in less mobile fractions (average values were 48 ± 12% for Cu bound to soil organic matter; 15 ± 9% for Cu associated to amorphous inorganic materials; 12 ± 9% for Cu bound to crystalline Fe and Al oxides and 23 ± 12% for residual Cu), whereas exchangeable Cu constituted approximately 3 ± 3% of total Cu. All soil samples were separated in three well differentiated groups according to their physical, chemical and Cu fractionation data (Ribeiro, Ribeira Sacra and Monterrei samples; O Bierzo, Valdeorras and Monterrei samples; Rías Baixas and Vinhos Verdes samples), being soil type, climate and fungicide application as the most determinant factors for soil quality.Xunta de Galici

Microbial community structure of vineyard soils with different pH and copper content

The phospholipid fatty acid (PLFA) pattern of vineyard soils from the Northwest of the Iberian Peninsula was studied to identify soil factors determining the microbial community structure, with special emphasis on effects of Cu pollution and pH. A wide range of soil samples, collected from six winegrowing regions (Rías Baixas, Ribeiro, Ribeira Sacra, Monterrei, Valdeorras and Vinhos Verdes) was analyzed. Physico-chemical properties, including total Cu content, five different Cu fractions and available Cu, were also determined. Total Cu varied between 33 and 1120 mg kg1 and pHwater between 4.3 and 7.3. Soil pH rather than Cu content was most important in determining the composition of the microbial community. An increase in the relative concentrations of the monounsaturated PLFAs 16:1ω5, 16:1ω7c, 17:1ω8 and 18:1ω7 and a decrease of br18:0, i17:0, 17:0 and cy19:0 was correlated to an increase in pH. A significant effect of Cu was also found, with an increase in the branched fatty acids 10Me17:0, i16:0, 10Me18:0, a17:0 and br17:0 as consequence of Cu pollution. This change in the PLFA pattern was correlated to both the total and available fractions of Cu. Although the PLFA pattern was a useful tool to assess factors affecting the microbial composition, it is difficult to differentiate between these factors.Xunta de Galicia | Ref. 09MDS013291P

Estimation of baseline levels of bacterial community tolerance to Cr, Ni, Pb, and Zn in unpolluted soils, a background for PICT (pollution-induced community tolerance) determination

The PICT method (pollution-induced community tolerance) can be used to assess whether changes in soil microbial response are due to heavy metal toxicity or not. Microbial community tolerance baseline levels can, however, also change due to variations in soil physicochemical properties. Thirty soil samples (0–20 cm), with geochemical baseline concentrations (GBCs) of heavy metals and from five different parent materials (granite, limestone, schist, amphibolite, and serpentine), were used to estimate baseline levels of bacterial community tolerance to Cr, Ni, Pb, and Zn using the leucine incorporation method. General equations (n = 30) were determined by multiple linear regression using general soil properties and parent material as binary variables, explaining 38% of the variance in log IC50 (concentration that inhibits 50% of bacterial growth) values for Zn, with 36% for Pb, 44% for Cr, and 68% for Ni. The use of individual equations for each parent material increased the explained variance for all heavy metals, but the presence of a low number of samples (n = 6) lead to low robustness. Generally, clay content and dissolved organic C (DOC) were the main variables explaining bacterial community tolerance for the tested heavy metals. Our results suggest that these equations may permit applying the PICT method with Zn and Pb when there are no reference soils, while more data are needed before using this concept for Ni and Cr.This study has been funded by the Spanish Ministry of Economy and Competitiveness through the project CTM2015-73422-JIN (FEDER Funds). David Fernández-Calviño holds a Ramón y Cajal contract (RYC-2016–20411) fnanced by the Spanish Ministry of Economy, Industry and Competitiveness. Claudia CampilloCora holds a predoctoral fellowship fnanced by Xunta de Galicia (ED481A-2020/084). Diego Soto-Gómez was supported by a postdoctoral fellowship from the Spanish Ministry of Education “Juan de la Cierva Formación (FJC2019-039176-I).