Hemp stalk, a widely available agricultural waste, is an ideal eco-friendly raw material for biochar production. Carbonization experiments were conducted as a novel approach for the scalable and value-added utilization of hemp stalk under oxygen-exclusion conditions. The effects of feedstock types—Hibiscus cannabinus (KS), Corchorus spp. (JS), and Boehmeria spp. (RS)—and pyrolysis temperatures on biochar properties were analyzed through the measurements of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy. The pH and electrical conductivity (EC) of biochars increased with increasing pyrolysis temperature. Notably, EC was significantly higher for RS (940–2278 μS/cm) than for KS (517–879 μS/cm) and JS (583–863 μS/cm). The C content in these three biochars increased as the temperature increased, whereas the H/C atomic ratio decreased, most notably in JS (by 0.33%). According to FTIR and XRD data, with the pyrolysis temperature increasing, the acidic oxygen-containing groups on biochar surfaces reduced. KS700, with superior aromatic structure and stability, may be able to effectively adsorb heavy metal ions. RS700, with relatively high pH and EC, was suitable for alleviating soil acidification and nutrient deficiency. The feedstock and pyrolysis temperature significantly affected the element content, pore structure, and stability of biochars derived from hemp stalk.

Shock load from industrial wastewater is known to harm the microbial activities of the activated sludge in wastewater treatment plants (WWTPs) and disturb their performance. This study developed a system monitoring the activated sludge activities based on the relative oxygen uptake rate (ROUR) and explored the influential factors with wastewater and the activated sludge samples collected from a typical WWTP in the Taihu Lake of southern Jiangsu province, China. The ROUR was affected by the concentration of toxic substances, mixed liquid suspended solids (MLSS), hydraulic retention time (HRT) and pH. Higher toxin contents significantly decreased the ROUR and the EC₅₀ value of Zn²⁺, Ni²⁺, Cr(VI), Cu²⁺, and Cd²⁺ was 13.40, 15.54, 97.56, 12.01, and 14.65 mg/L, respectively. The ROUR declined with the increasing HRT and MLSS above 2000 mg/L had buffering capacities for the impacts of toxic substances to some extent. The ROUR remained stable within a broad range pH (6–10), covering most of the operational pH in WWTPs and behaving as an appropriate indicator for monitoring the shock load. A toxicity model assessing and predicting the ROUR was developed and fitted well with experimental data. Coupling the ROUR monitoring system and toxicity model, an online early-warning system was assembled and successfully used for predicting the toxicity of different potential toxic metals. This study provides a new universal toxicity model and an online early-warning system for monitoring the shock load from industrial wastewater, which is useful for improving the performance of WWTPs.

Brassica juncea var. multiceps (Xuelihong), a variety of B. juncea (L.) Czern., holds considerable nutritional and economic value. However, its complete chloroplast genome and the evolutionary relationships within Brassicaceae remain poorly characterized. Using Illumina NovaSeq 6000 high-throughput sequencing, we assembled and annotated the full chloroplast genome sequence of B. juncea var. multiceps. The genome is 153,483 bp in length, with 36.36% GC content, and encodes 132 genes. Codon usage analysis identified leucine (Leu) as the dominant amino acid. Thirty-one codons had relative synonymous codon usage (RSCU; a metric for codon preference) values greater than one, with 93.55% of these preferred codons ending in A/U. We detected 37 dispersed repeats (14 forward, 18 palindromic, 3 reverse, and 2 complementary) and 315 simple sequence repeats (SSRs), with mononucleotide SSRs dominating (72.70%). Analysis of the Ka/Ks ratio, a measure of selection pressure (where values greater than one indicate positive selection), indicated that ycf1, ycf2, and nadhF genes may have undergone positive selection. The nucleotide diversity analysis revealed five hypervariable hotspot-genomic regions with high mutation rates, which are critical for phylogenetic studies. Phylogenetic analysis of 26 Brassicaceae species revealed that B. juncea var. multiceps is closely related to B. juncea. Notably, this is the first complete chloroplast genome of B. juncea var. multiceps, with unique hypervariable regions not reported in other B. juncea varieties. These findings clarify evolutionary relationships in Brassicaceae, provide molecular markers for the genetic breeding of B. juncea var. multiceps, and enhance our understanding of chloroplast genome adaptation in Brassica.