Though the interaction between humic acid (HA) and heavy metals has been widely reported, the effects of HA on the toxicity of heavy metals to plants are still in debate. In this study, the regulation mechanisms of HA on Pb stress in tea plant (Camellia sinensis L.) was investigated through hydroponic experiments, and the experimental results were explained by using transmission electron microscope (TEM), scanning transmission X-ray microscopes (STXM) and isobaric tags for relative and absolute quantitation (iTRAQ) differential proteomics. Significant alleviation of Pb stress was found with HA coexistence. TEM results showed that HA greatly mitigated the damage of cells caused by Pb stress. Compared with sole Pb treatment, the addition of HA increased the contents of pectin and pectic acid in the cell wall by 10.5% and 30.5%, while arabinose (Ara) and galactose (Gal) decreased by 20.5% and 15.9%, respectively, which were beneficial for increasing Pb adsorption capacity of the cell wall and promoting cell elongation. Moreover, iTRAQ differential proteomics analysis proved that HA strengthened the antioxidant system, promoted the synthesis of cell wall, and stabilized protein and sulfur-containing substance metabolism in molecular level. Notably, the concentration of calcium (Ca) in the cell wall of HA coexistence treatment was 47.4% higher than Pb treatment. STXM results also indicated that the distribution of Ca in the cell wall was restored with the presence of HA. This might promote the formation of the egg-box model, thus alleviating Pb stress in cells. Our results reveal the regulation mechanisms of HA on Pb detoxification in plants and provide useful information for improving the safety of agricultural products.

Observational studies have indicated that low-to-moderate exposure to cadmium (Cd), lead (Pb), and mercury (Hg) adversely affects birth anthropometry, but results are inconclusive. The aim of this study was to elucidate potential impact on birth anthropometry of exposure to Cd, Pb, and Hg in pregnant women, and to identify the main dietary sources. In the NICE (Nutritional impact on Immunological maturation during Childhood in relation to the Environment) birth-cohort in northern Sweden, blood and urine were collected from pregnant women in early third trimester. Cd, Pb and Hg were measured in erythrocytes (n = 584), and Cd also in urine (n = 581), by inductively coupled plasma mass spectrometry. Dietary data were collected through a semi-quantitative food frequency questionnaire administered in mid-third trimester. Birth anthropometry data were extracted from hospital records. In multivariable-adjusted spline regression models, a doubling of maternal erythrocyte Cd (median: 0.29 μg/kg) above the spline knot of 0.50 μg/kg was associated with reduced birth weight (B: −191 g; 95% CI: −315, −68) and length (−0.67 cm; −1.2, −0.14). The association with birth weight remained when the analysis was restricted to never-smokers. Likewise, a doubling of erythrocyte Hg (median 1.5 μg/kg, mainly MeHg) above 1.0 μg/kg, was associated with decreased birth weight (−59 g; −115, −3.0), and length (−0.29 cm; −0.54, −0.047). Maternal Pb (median 11 μg/kg) was unrelated to birth weight and length. Erythrocyte Cd was primarily associated with intake of plant derived foods, Pb with game meat, tea and coffee, and Hg with fish. The results indicated that low-level maternal Cd and Hg exposure were associated with poorer birth anthropometry. Further prospective studies in low-level exposed populations are warranted.

Chinese dark tea is widely enjoyed for its multiple health-promoting effects and pleasant taste. However, its production involves fermentation by microbiota in raw tea, some of which are filamentous fungi and thus potential mycotoxin producers. Accordingly, whether mycotoxins pose health risk on dark tea consumption has become a public concern. In this study, a cleaning method of multi-functional column (MFC) and immunoaffinity column (IAC) in tandem combined to HPLC detection was developed and validated for determining ten mycotoxins of six groups (i.e., aflatoxins of B₁, B₂, G₁ and G₂, ochratoxin A, zearalenone, deoxynivalenol, fumonisins of B₁, B₂, and T-2) in dark teas. The interferences from secondary metabolites were effectively reduced, and the sensitivities and recoveries of the method were qualified for tea matrices. Six groups mycotoxins were determined in 108 samples representing the major Chinese dark teas by using the new method. Subsequently, the dietary exposure and health risks were evaluated for different age and gender groups in Kunming and Pu’er in China and Ulan Bator in Mongolia. The occurrence of zearalenone was 4.63% and that of ochratoxin A was 1.85%, with the other four groups mycotoxins were below the limits of quantification. The hazard index values for the five groups’ non-carcinogenic mycotoxins were far below 1.0. The deterministic risk assessment indicated no non-carcinogenic risks for dark tea consumption in the three areas. Probabilistic estimation showed that the maximum value of 95th percentile carcinogenic risk value for the aflatoxins was 2.12 × 10⁻⁸, which is far below the acceptable carcinogenic risk level (10⁻⁶). Hereby, six groups mycotoxins in Chinese dark tea showed no observed risk concern to consumers.

The study of emissions and depositions of atmospheric reactive nitrogen species (Nᵣs) in a region is important to uncover the sources and sinks of atmospheric Nᵣs in the region. In this study, atmospheric total Nᵣs depositions including both wet-only and dry deposition were monitored simultaneously across major land-use types in a 105 km² catchment called Jinjing River Catchment (JRC) in subtropical central China from 2015 to 2016. Based on activity data and emission factors for the main Nᵣs emission sources, ammonia (NH₃) and nitrogen oxides (NOₓ) emission inventories for the catchment were also compiled. The estimated total Nᵣs deposition in JRC was 35.9 kg N ha⁻¹ yr⁻¹, with approximately 49.7 % attributed to reduced compounds (NHₓ), and 40.5 % attributed to oxidized (NOy). The total Nᵣs emission rate in JRC was 80.4 kg N ha⁻¹ yr⁻¹, with 61.5 and 18.9 kg N ha⁻¹ yr⁻¹ from NH₃ and NOₓ emissions, respectively. Livestock excretion and fertilization were the two main contributing emission sources for NH₃, while vehicle sources contributed the bulk of NOₓ emissions. The net atmospheric budgets of Nᵣs in paddy field, forest, and tea field were +3.7, −36.1, and +23.8 kg N ha⁻¹ yr⁻¹, respectively. At the catchment scale, the net atmospheric budget of Nᵣs was +47.7 kg N ha⁻¹ yr⁻¹, with +43.7 kg N ha⁻¹ yr⁻¹ of NHₓ and +4.0 kg N ha⁻¹ yr⁻¹ of NOy, indicating that the subtropical catchment was net sources of atmospheric Nᵣs. Considering that excessive atmospheric Nᵣ emissions and deposition may cause adverse effects on the environment, effects should be conducted to mitigate the Nᵣs emissions from agriculture and transportation, and increasing the area of forest is good for reducing the net positive budget of atmospheric Nᵣs in the subtropical catchments in China.

Organic-matter decomposition has long been proposed as a tool to assess stream functional integrity, but this indicator largely depends on organic-matter selection. We assessed eight decomposition-based indicators along two well-known environmental gradients, a nutrient-enrichment gradient (0.2–1.4 mg DIN/L) in central Portugal and an acidification gradient (pH: 4.69–7.33) in north-eastern France to identify the most effective organic-matter indicator for assessing stream functional integrity. Functional indicators included natural leaf litter (alder and oak) in 10-mm and 0.5-mm mesh bags, commercial tea (Lipton green and rooibos teas in 0.25-mm mesh bags), wood sticks (wood tongue depressors) and cotton strips. Biotic indices based on benthic macroinvertebrates (IPtIN for Portugal and IBGN for France) were calculated to compare the effectiveness of structural and functional indicators in detecting stream impairment and to assess the relationship between both types of indicators. The effectiveness of organic-matter decomposition rates as a functional indicator depended on the stressor considered and the substrate used. Decomposition rates generally identified nutrient enrichment and acidification in the most acidic streams. Decomposition rates of alder and oak leaves in coarse-mesh bags, green and rooibos teas and wood sticks were positively related with pH. Only decomposition rates of rooibos tea and wood sticks were related with DIN concentration; decomposition rates along the nutrient-enrichment gradient were confounded by differences in shredder abundance and temperature among streams. Stream structural integrity was good to excellent across streams; the IPtIN index was unrelated to DIN concentration, while the IBGN index was positively related with pH. The relationships between decomposition rates and biotic indices were loose in most cases, and only decomposition rates of alder leaves in coarse-mesh bags and green tea were positively related with the IBGN. Commercial substrates may be a good alternative to leaf litter to assess stream functional integrity, especially in the case of nutrient enrichment.

Tea plant is capable of hyper-accumulating fluoride (F) in leaves, suggesting drinking tea may cause excessive F intake in our body and threaten the health. This study investigated the changes in the structure, composition, and F content in the leaf cell wall of the tea (Camellia sinensis) under different F conditions to demonstrate the role of cell wall in F enrichment in tea plants. The cell wall was shown as the main part for F accumulation (67%–92%), with most of F distributed in the pectin fraction (56%–71%). With increasing F concentration, a significant increase (p < 0.05) was observed in the F content of cell wall and its components, the level of cell wall metal ions (i.e. Cu, Mg, Zn, Al, Ca, Ba, Mn), as well as the content of total cell wall materials, cellulose, and pectin. Meanwhile, the level of Cu, Mg, Zn, pectin, and cellulose was significantly positively correlated with the F content in the leaf cell wall. F addition was shown to increase the fluorescence intensity of LM19 and 2F4 antibody-labeled low-methylesterified homogalacturonans (HGs), while decrease LM20-labeled high-methylesterified HGs, coupled with an increase in the activity and gene expression of pectin methyl esterases (PMEs) in tea leaves. All these results suggest that F addition can increase pectin content and demethylesterification, leading to increased absorption of metal cations and chelation of F in the cell wall through the action of metal ions.

Pesticides are used worldwide with potential harmful effects on both fauna and flora. The Kibale National Park in Uganda, a site renowned for its biodiversity is surrounded by tea, banana and eucalyptus plantations as well as maize fields and small farms. We previously showed presence of pesticides with potential endocrine disruptive effects in the vicinity. To further investigate the water pollution linked to agricultural pressure in this protected area, we implemented a complementary monitoring strategy based on: analytical chemistry, effects based methods and the deployment of Polar Organic Chemical Integrative Samplers (POCIS). Chemical analysis of the POCIS extracts revealed the presence of 13 pesticides: carbofuran, DEET, 2.4-D amine, carbaryl, ametryn, isoproturon, metolachlor, terbutryn, dimethoate, imidacloprid, picaridin, thiamethoxam, carbendazim, with the first three being present in the largest quantities. Water samples collected at the POCIS sampling sites exhibited thyroid and estrogen axis disrupting activities in vivo, in addition to developmental and behaviour effects on Xenopus laevis tadpoles model. Based on our observations, for the health of local human and wildlife populations, further monitoring as well as actions to reduce agrochemical use should be considered in the Kibale National Park and in regions exposed to similar conditions.

Polycyclic aromatic hydrocarbons (PAHs) have been detected in some commercial teas around the world and pose a threat to tea consumers. However, green tea polyphenols (GTP) possess remarkable antioxidant and anticancer effects. In this study, the potential of GTP to block the toxicity of the model PAH phenanthrene was examined in human embryo lung fibroblast cell line HFL-I. Both GTP and phenanthrene treatment individually caused dose-dependent inhibition of cell growth. A full factorial design experiment demonstrated that the interaction of phenanthrene and GTP significantly reduced growth inhibition. Using the median effect method showed that phenanthrene and GTP were antagonistic when the inhibitory levels were less than about 50%. Apoptosis and cell cycle detection suggested that only phenanthrene affected cell cycle significantly and caused cell death; GTP lowered the mortality of HFL-I cells exposed to phenanthrene; However, GTP did not affect modulation of the cell cycle by phenanthrene.

An emerging stress of pesticides in plant and soil is closely watched as it affects crop antioxidant systems, nutritional quality, and flavor. Although selenium (Se) can enhance the resistance of plants, the protective mechanism of nanoselenium is still not known under the long-term pesticide stress in tea trees. In this study, we investigated the potential effects of foliar application of nanoselenium for a two-year field experiment on tea plants under pesticide-induced oxidative stress. Compared to control, nano-Se (10 mg/L) markedly enhanced the protein, soluble sugar, carotenoid, tea polyphenols, and catechins contents. High levels of theanine, glutamic acid, proline, and arginine were found to be induced most likely by adjusting the GS-GOGAT cycle. Se-supplementation may promote tea leaves’ secondary metabolism, thus increasing the accumulation of total phenols and flavonoids (apigenin, kaempferol, quercetin, myricetin, and rutin). It also minimized the accumulation of malondialdehyde, hydrogen peroxide, and superoxide anion by activating the antioxidants enzymes including in the AsA-GSH cycle. Selenium-rich tea also showed better fragrance and flavor. In summary, nano-Se can ameliorate the nutrients quality and abiotic stresses resistance of crops.

Tea plants (Camellia sinensis (L.) O. Kuntze) can hyperaccumulate fluoride (F). The accumulation of F in tea leaves may induce serious health problems in tea consumers. It has been reported that selenium (Se) could reduce the accumulation of heavy metals in plants. Thus, the aim of this study was to investigate whether exogenous Se could reduce F accumulation in tea plant. The results showed that Se treatment could decrease F content in tea leaves, increase F accumulation in roots, decrease the proportion of water-soluble F in tea leaves and increase the Se content. Low F levels promoted the accumulation of Se in tea plants. Se treatment could modulate F-induced oxidative injury by decreasing malondialdehyde level and increasing the activities of superoxide dismutase, peroxidase and catalase. Moreover, Se inhibited F-induced increase in leaf iron, calcium, aluminum, leaf and root magnesium and lead contents. These results showed that Se application could decrease F content and increase Se content in tea leaves, which may be served as a novel strategy for production of healthy tea.