GABA, a four-carbon non-protein amino acid, plays an important role in animals and plants. We previously found GABA could alleviate alkali stress in apple seedlings. However, its physiological mechanism under heavy metal cadmium (Cd) stress need to be further studied. Thus, we explored its biological role in response to Cd stress. It was verified that 0.5 mM GABA could effectively alleviate Cd toxicity. Using NMT technique, we found that exogenous GABA could significantly reduce the net Cd²⁺ fluxes in apple roots, and Cd content was significantly lower than that in roots under Cd stress. Further analysis indicated exogenous GABA could significantly reduce the expression of genes related to the uptake and transport of Cd in apples under Cd stress. In addition, exogenous GABA could significantly increase the content of amino acids in apple roots under Cd stress. GAD is a key enzyme in GABA synthesis, we obtained transgenic apple roots of overexpression MdGAD1. Compared with the control, transgenic roots accumulated less Cd, maintained lower Cd uptake by roots, and lower expression of related transport genes. These results showed that GABA could effectively alleviate Cd toxicity in apple seedlings and provide a new perspective of GABA to alleviate Cd stress.

In this study, magnetic biochar (MAB) and humic acid (HA)-coated magnetic biochar produced from apple branches without and after cellulase hydrolysis (HMAB and CHMAB, respectively) were prepared and tested as adsorbents of enrofloxacin (ENR) and moxifloxacin (MFX) in aqueous solution. Compared with MAB and HMAB, novel adsorbent CHMAB possessed a superior mesoporous structure, greater graphitization degree and abundant functional groups. When antibiotic solutions ranged from 2 to 20 mg L⁻¹, the theoretical maximum adsorption capacities of CHMAB for ENR and MFX were 48.3 and 61.5 mg g⁻¹ at 35 °C with adsorbent dosage of 0.4 g L⁻¹, respectively, while those of MAB and HMAB were 39.6 and 54.4 mg g⁻¹, and 44.7 and 59.0 mg g⁻¹, respectively. The pseudo-second-order kinetic model and Langmuir model presented a better fitting to the spontaneous and endothermic adsorption process. The maximum adsorption capacity of ENR and MFX onto CHMAB was achieved at initial pH values of 5 and 8, respectively. Additionally, the adsorption capacity of ENR and MFX decreased with increasing concentrations of K⁺ and Ca²⁺ (0.02–0.1 mol L⁻¹). Synergism between the pore-filling effect, π-π electron-donor-acceptor interactions, regular and negative charge-assisted H-bonding, surface complexation, electrostatic interactions and hydrophobic interactions may dominate the adsorption process. This study demonstrated that a novel magnetic biochar composite prepared through pyrolysis of agricultural waste lignocellulose hydrolyzed by cellulase in combination with HA coating was a promising adsorbent for eliminating quinolone antibiotics from aqueous media.

The bioavailability of Cu, Zn, Pb and Cd from field-aged orchard soils in a certified fruit plantation area of the Northeast Jiaodong Peninsula in China was assessed using bioassays with earthworms (Eisenia fetida) and chemical assays. Soil acidity increased with increasing fruit cultivation periods with a lowest pH of 4.34. Metals were enriched in topsoils after decades of horticultural cultivation, with highest concentrations of Cu (132 kg−1) and Zn (168 mg kg−1) in old apple orchards and Pb (73 mg kg−1) and Cd (0.57 mg kg−1) in vineyard soil. Earthworm tissue concentrations of Cu and Pb significantly correlated with 0.01 M CaCl2-extractable soil concentrations (R2 = 0.70, p < 0.001 for Cu; R2 = 0.58, p < 0.01 for Pb). Because of the increased bioavailability, regular monitoring of soil conditions in old orchards and vineyards is recommended, and soil metal guidelines need reevaluation to afford appropriate environmental protection under acidifying conditions.

Land-use types may affect soil aggregates' stability and organic carbon (OC) distribution characteristics, but little is known about the effects on the distribution characteristics of microplastics (MPs) in the aggregates. Hence, the MPs abundance of soil aggregates and analyzed aggregates’ stability, composition, and OC content from two soil layers of four land-use types in Gansu Province were investigated in this study. The total MPs abundances in woodland, farmland (wheat, maize, and potato), orchard, and intercropping (potato + apple orchard) of top and deep soils were 1383.3 and 1477.9, 1324.6 and 931.1, 1757.1 and 1930.9, 2127.2 and 1998.0, 1335.9 and 886.7, and 1777.5 and 1683.3 items kg⁻¹, respectively. The largest MPs abundance was detected in the >5 mm fractions of topsoil in potato (3077.3 items kg⁻¹), followed by maize (3044.7 items kg⁻¹) and intercropping (2718.4 items kg⁻¹). In the topsoil, the total MPs abundance increased significantly with decreasing aggregate stability, and also was positively correlated with bulk density, microbial biomass, and total nitrogen contents of bulk soil. Summarizing, the abundance distribution of MPs correlates with the soil aggregate characteristics of the different land-use types.

This study investigated the effects of adding biochar (BC) on the fate of ciprofloxacin (CIP) and its related antibiotic tolerance (AT) in activated sludge. Three activated sludge reactors were established with different types of BC, derived from apple, pear, and mulberry tree, respectively, and one reactor with no BC. All reactors were exposed to an environmentally relevant level of CIP that acted as a definitive selective pressure significantly promoting AT to four representative antibiotics (CIP, ampicillin, tetracycline, and polymyxin B) by up to two orders of magnitude. While CIP removal was negligible in the reactor without BC, the BC-dosed reactors effectively removed CIP (70–95% removals) through primarily adsorption by BC and biodegradation/biosorption by biomass. The AT in the BC-added reactors was suppressed by 10–99%, compared to that without BC. The BC addition played a key role in sequestering CIP, thereby decreasing the selective pressure that enabled the proactive prevention of AT increase. 16S rRNA gene sequencing analysis showed that the BC addition alleviated the CIP-mediated toxicity to community diversity and organisms related to phosphorous removal. Machine learning modeling with random forest and support vector models using AS microbiome data collectively pinpointed Achromobacter selected by CIP and strongly associated with the AT increase in activated sludge. The identification of Achromobacter as an important AT bacteria revealed by the machine learning modeling with multiple models was also validated with a linear Pearson's correlation analysis. Overall, our study highlighted Achromobacter as a potential useful sentinel for monitoring AT occurring in the environment and suggested BC as a promising additive in wastewater treatment to improve micropollutant removal, mitigate potential AT propagation, and maintain community diversity against toxic antibiotic loadings.

Evidence on the relationship between lifestyle, socio-economic factors and pesticide exposure and urinary concentrations of organophosphate (OP) pesticide metabolites among children is generally incomplete. This study investigated the relationship between socio-economic factors and reported pesticide exposures and the sum of three urinary concentrations of dialkyl phosphate metabolites (DAP) among boys living in the rural areas of the Western Cape, South Africa. Data was collected during a cross-sectional study of 183 boys from three agricultural intense areas. Measurements included a questionnaire on socio-economic and pesticide exposures and urinary DAP concentrations. Most boys (70%) lived on farms with a median age of 12 years (range: 5.0–19.5 years). Children aged >14 years had lower DAP urine concentrations (median = 39.9 ng/ml; β = −68.1 ng/ml; 95% CI: −136.8, 0.6) than children aged 9 years and younger (median = 107.0 ng/ml). DAP concentrations also varied significantly with area, with concentrations in the grape farming area, Hex River Valley (median = 61.8 ng/ml; β = −52.1; 95% CI: −97.9, −6.3 ng/ml) and the wheat farming area, Piketberg (median = 72.4 ng/ml; β = −54.2; 95% CI: 98.8, −9.7 ng/ml) lower than those in the pome farming area, Grabouw (median = 79.9 ng/ml). Other weaker and non-significant associations with increased DAP levels were found with increased household income, member of household working with pesticides, living on a farm, drinking water from an open water source and eating crops from the vineyard and or garden. The study found younger age and living in and around apple and grape farms to be associated with increased urinary DAP concentrations. Additionally, there were other pesticide exposures and socio-economic and lifestyle factors that were weakly associated with elevated urinary DAP levels requiring further study. The study provided more evidence on factors associated to urinary DAP concentrations especially in developing country settings.

The aim of this study was to elucidate the effects of apricot shell-derived biochar (ASB) and apple tree-derived biochar (ATB) on soil properties, plant growth, microbial communities, enzymatic activities, and Zn and Cd fractionation and phytoavailability in mining soils. Smelter soil contaminated by Zn (1860.0 mg kg⁻¹) and Cd (39.9 mg kg⁻¹) was collected from Fengxian, China, treated with different doses (0 (control), 1, 2.5, 5, and 10% w/w) of both biochars and cultivated by Brassica juncea in a greenhouse pot experiment. The acid-soluble, reducible, oxidizable, and residual fraction and plant tissue concentrations of Zn and Cd were determined. Biochar addition improved plant growth (22.6–29.4%), soil pH (up to 0.94 units), and soil organic matter (up to 4-fold) compared to the control. The ASB and ATB, particularly ATB, reduced the acid-soluble (21–26% for Zn and 15–35% for Cd) and the reducible (9–36% for Zn and 11–19% for Cd) fractions of Zn and Cd and altered these fractions in the organic and residual fractions. Therefore, the biochars decreased the metal concentrations in the roots (36–41% for Zn and 33–37% for Cd) and shoots (25–31% for Zn and 20–29% for Cd), which might be due to the increase in pH, biochar liming effects, and metal sorption by the biochar. The biochars impact on the bacterial community composition was selective. The ASB and ATB decreased the activities of soil β-glucosidase, dehydrogenase, and alkaline phosphatase while increasing the urease activity. The biochars, particularly ATB, can be considered as effective soil amendments for reducing the phytotoxicity of Zn and Cd in contaminated soils, improving plant growth, enhancing the abundance of specific bacterial groups and increasing urease activity; however, more attention should be paid to their negative effects on the activities of β-glucosidase, dehydrogenase, and alkaline phosphatase.

Apple orchards are highly manipulated crops in which large amounts of pesticides are used. Some of these pesticides lack target specificity and can cause adverse effects in non-target organisms. In order to evaluate the environmental risk of these products, the use of transplanted sentinel organisms avoids side-effects from past events and facilitate comparison of multiple sites in a short time. We released specimens of the terrestrial snail Xeropicta derbentina in each 5 of two kinds of apple orchards with either conventional or organic management strategies plus in a single abandoned orchard. After one month, individuals were retrieved in order to measure acetylcholinesterase (AChE) activity. Mean values of AChE activity were significantly reduced in all conventional apple orchards compared to the others. Results show that the measurement of biomarkers such as AChE inhibition in transplated X. derbentina could be useful in the environmental risk assessment of post-authorized pesticides.