Medium nitrogen optimized Boehmeria nivea L. growth in copper contaminated soil.

Copper (Cu) pollution in agricultural soils is considered as a serious health risk due to its accumulation in plants. Thus, there is an urgent need to optimize nutrient application for higher yield with lower Cu uptake to ensure food security. A pot experiment was conducted to investigate the effectiveness of nitrogen fertilizer (N) on Boehmeria nivea growth, gas exchange characteristics, antioxidant capacity and uptake of Cu in contaminated soil. Therefore, combinations of Cu levels (0, 100, 300 mg kg-1) and N levels (0, 140, 280, 420 kg ha-1) were applied. The results showed that N at 280 kg ha-1 significantly (≤0.05) increased plant growth in terms of fresh biomass, plant height, stem diameter and number of leaves per plant up to100 mg kg-1 Cu in soil for all harvests (H1, H2, H3 and H4). However, the interactive effect of Cu and N on Cu uptake by plant varied among N levels. Furthermore, N at 280 kg ha-1 also improved the gas exchange characteristics viz., net photosynthesis (Pn), transpiration rate (Tr) and stomatal conductance (gs), while decreased oxidative stress in B. nivea up to 100 mg kg-1 Cu in soil, relative to control. Thus N at 280 kg ha-1 can be considered as an effective dose for high fresh biomass with lower Cu uptake by B. nivea grown as fodder in Cu contaminated soils (≤100 mg kg-1). Overall, present research highlighted the necessity of balanced or optimum N application for sustainable B. nivea forage production in Cu contaminated agricultural lands.

Investigating the potential of different jute varieties for phytoremediation of copper-contaminated soil.

Copper (Cu), with many documented cases of Cu toxicity in agriculture lands, is becoming an increasingly common issue in and elsewhere in China. However, fibrous crop such as jute is being used as phytoremediation candidate in Cu-contaminated soils due to its huge biomass. A pot experiment was conducted using four different varieties (HT, C-3, GC, and SH) of jute grown in highly Cu-contaminated soil (2221 mg kg-1), collected from Hubei Province, China. Results from this study showed that C-3 and HT were more resistant to Cu stress, while GC and SH had a serious effect due to high concentration of Cu and a significant decrease in growth and biomass. Furthermore, Cu in roots, leaves, stem core, and bast were higher in C-3 and HT compared with GC and SH. Likewise, at post-harvesting stage, maximum Cu concentration from Cu-contaminated soil was extracted by C-3 and HT while small amount was accumulated by GC and SH. The high content of malondialdehyde (MDA) in the leaves of GC and SH indicated that Cu induced oxidative damage while the antioxidative enzyme activities of superoxidase dismutase (SOD) and peroxidase (POD) were increased to scavenge reactive oxygen species (ROS) formed during oxidative stress in the plants. Conclusively, it can be identified that when grown in Cu-contaminated soil, C-3 and HT have greater ability to grow in polluted soils and possible phytoremediation materials to revoke a large amount of Cu.

Influence of phosphorus on copper phytoextraction via modulating cellular organelles in two jute (Corchorus capsularis L.) varieties grown in a copper mining soil of Hubei Province, China.

Soil in mining areas is typically highly contaminated with heavy metals and lack essential nutrients for plants. Phosphorus reduces oxidative stress, improves plant growth, composition, and cellular structure, as well as facilitates the phytoremediation potential of fibrous crop plant species. In this study, we investigated two jute (Corchorus capsularis) varieties HongTieGuXuan and GuBaChangJia cultivated in copper (Cu)-contaminated soil (2221 mg kg-1), under different applications of phosphorus (0, 30, 60, and 120 kg ha-1) at both anatomical and physiological levels. At the same Cu concentration, the tolerance index of HongTieGuXuan was higher than that of GuBaChangJia, indicating that HongTieGuXuan may be more tolerant to Cu stress. Although the normal concentration of P (60 kg ha-1) in the soil improved plant growth, biomass, chlorophyll content, fibre yield and quality, and gaseous exchange attributes. However, high concentration of P (120 kg ha-1) was toxic to both jute varieties affected morphological and physiological attributes of the plants under same level of Cu. Moreover, Cu toxicity increased the oxidative stress in the leaves of both jute varieties was overcome by the activities of antioxidant enzymes. Furthermore, the high concentration of Cu altered the ultrastructure of chloroplasts, plastoglobuli, mitochondria, and many other cellular organelles in both jute varieties. Thus, phytoextraction of Cu by both jute varieties increased with the increase in P application in the Cu-contaminated soil. This suggests that P application enhanced the phytoremediation potential jute plants and can be cultivated as fibrous crop in Cu-contaminated sites.

Copper Uptake and Accumulation, Ultra-Structural Alteration, and Bast Fibre Yield and Quality of Fibrous Jute (Corchorus capsularis L.) Plants Grown Under Two Different Soils of China.

Copper (Cu) is an essential heavy metal for plants, but high Cu concentration in the soil causes phytotoxicity. Some plants, however, possess a system that can overcome Cu toxicity, such as Cu localization, and an active antioxidant defence system to reduce oxidative damage induced by high Cu concentration. The present study was conducted to explore the phytoremediation potential, morpho-physiological traits, antioxidant capacity, and fibre quality of jute (Corchorus capsularis) grown in a mixture of Cu-contaminated soil and natural soil at ratios of 0:1 (control), 1:0, 1:1, 1:2 and 1:4. Our results showed that high Cu concentration in the soil decreased plant growth, plant biomass, chlorophyll content, gaseous exchange, and fibre yield while increasing reactive oxygen species (ROS), which indicated oxidative stress induced by high Cu concentration in the soil. Antioxidant enzymes, such as superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) scavenge ROS in plant cells/tissues. Furthermore, high Cu concentration did not significantly worsen the fibre quality of C. capsularis, and this plant was able to accumulate a large amount of Cu, with higher Cu accumulation in its shoots than in its roots. Transmission electron microscopy (TEM) revealed that Cu toxicity affected different organelles of C. capsularis, with the chloroplast as the most affected organelle. On the basis of these results, we concluded that high Cu concentration was toxic to C. capsularis, reducing crop yield and plant productivity, but showing little effect on plant fibre yield. Hence, C. capsularis, as a fibrous crop, can accumulate a high concentration of Cu when grown in Cu-contaminated sites.

Study on mechanical and permeability characteristics of nickel-copper-contaminated soil solidified by CFG.

The study introduces the potential use of a novel curing agent formed by mixing cement, fly ash, and desulfurization gypsum (CFG) for the stabilization/solidification of nickel-copper-contaminated soil. According to the tests of the unconfined compressive strength (UCS), permeability, and scanning electron microscope (SEM), the samples' characteristics, which include UCS, deformation, and permeability, are investigated under different curing time, ion concentration, and curing agent content. The correlation between the UCS and permeability of samples is estimated. The results demonstrates that the gradual increase of the UCS and impermeability of the samples can be recognized with the increase of curing age; however, the failure strain decreased gradually but the trend is reversed with the increase of heavy metal concentration. Besides, greater amounts of CFG results in better mechanical and impermeability properties. The correlation between UCS and permeability coefficient reveals that the UCS of contaminated soil is significantly negatively correlated with permeability coefficient, and the prediction formulas of permeability coefficient based on age and CFG content are given respectively. Moreover, the microscopic analysis demonstrates that the hydration products calcium silicate hydrate(C-S-H) and ettringite (AFt) of CFG curing agent are the main reasons for the enhancement of the UCS and impermeability of contaminated soil. However, the increase of nickel and copper concentration leads to the decrease of hydration products and the compactness of solidified soil, which is the reason for the weakening of the compressive strength and impermeability of contaminated soil.