Regulation of heavy metals accumulated by Acorus calamus L. in constructed wetland through different nitrogen forms.

Improving accumulation of heavy metals (HMs) by plants is an important pathway for constructed wetland (CW) to alleviate the environmental risks caused by their release. This study aims to regulate HMs (Cr, Ni, Cu, Zn, and Cd) accumulated by Acorus calamus L. in the sandy substrate CW with different nitrogen forms, including ammonia (NH4+), nitrate (NO3‾), and NH4+/NO3‾ (1:1) in synthetic tailwaters. In general, the removal efficiency of HMs by CW could reach 92.4% under the initial concentrations below 500 µg/L. Accumulation percentages of HMs in the shoots and roots of plants in CW with NH4+ and NH4+/NO3‾ influents increased by 52-395% and 15-101%, respectively, when compared with that of NO3‾ treatment. Influents with NH4+ promoted plant growth of Acorus calamus L. and metabolic functions, such as carbohydrate metabolism/amino acid metabolism, related to HMs mobilization of rhizosphere bacterial communities, which might induce more organic acids and amino acids secreted by plants and microbes during their metabolic processes. These are the main reasons for the enhancive mobilization of HMs from their precipitation fractions and their uptake by plants in CW with NH4+ treatments. Moreover, the enhancement of organics secreted from plants and microbes also led to the high denitrification efficiency and nitrogen removal in CW. Overall, this study could provide a feasible method for the enhancive accumulation of HMs by wetland plants via the regulation water treatment process to appropriately increase NH4+ for CW.

Integration of CW-MFC and anaerobic granular sludge to explore the intensified ammonification-nitrification-denitrification processes for nitrogen removal.

The integration of constructed wetland-microbial fuel cell (CW-MFC) and anaerobic granular sludge (AGS) is an important way to promote its ammonification efficiency and decrease the land use scale. This study explored the integration of CW-MFC and AGS for nitrogen removal via the intensified ammonification-nitrification-denitrification processes with initial NH3-N, NO3-N, Org-N and total nitrogen (TN) concentrations of 10.5, 13.8, 21.4, and 45.7 mg L-1 in wastewater. Two reactors with AGS inoculated with a separated area (R1) and directly inoculated into gravel substrate (R2) were designed, respectively. Results showed that chemical oxygen demand (COD) removal efficiency could reach 85% in R1 and 81% in R2, and the conversion of Org-N to NH3-N and NO3-N to gaseous nitrogen were 80% and 90%, respectively. Although the conversion efficiency of NH3-N to NO2-N/NO3-N via nitrification process was only 18%, it could reach 45%, 94%, and 98% with the aeration rates of 50-, 100-, and 200-mL min-1. According to microstructural property and microbial community analyses, the separation gravel substrate and AGS areas in R1 availed for stable particle size of AGS, archaeal diversity, and metabolic activity even with a 1.5 times daily wastewater treatment capacity than that of R2. Overall, although the intensified ammonification-nitrification-denitrification processes for nitrogen removal could be achieved with supplementary aeration, further investigation is still needed to explore other substrate materials and high CW-MFC/AGS volume ratio for intensified nitrification process in CW-MFC associated with AGS.

Morphological and transcriptional responses of Lycopersicon esculentum to hexavalent chromium in agricultural soil.

The carcinogenic, teratogenic, and mutagenic effects of hexavalent chromium (Cr[VI]) on living organisms through the food chain raise the immediate need to assess the potential toxicological impacts of Cr(VI) on human health. Therefore, the concentration-dependent responses of 12 Cr(VI)-responsive genes selected from a high-throughput Lycopersicon esculentum complementary DNA microarray were examined at different Cr concentrations. The results indicated that most of the genes were differentially expressed from 0.1 mg Cr/kg soil, whereas the lowest-observable-adverse-effect concentrations of Cr(VI) were 1.6 mg Cr/kg soil, 6.4 mg Cr/kg soil, 3.2 mg Cr/kg soil, and 0.4 mg Cr/kg soil for seed germination, root elongation, root biomass, and root morphology, respectively, implying that the transcriptional method was more sensitive than the traditional method in detecting Cr(VI) toxicity. Dose-dependent responses were observed for the relative expression of expansin (p = 0.778), probable chalcone-flavonone isomerase 3 (p = -0.496), and 12S seed storage protein CRD (p = -0.614); therefore, the authors propose the 3 genes as putative biomarkers in Cr(VI)-contaminated soil. Environ Toxicol Chem 2016;35:1751-1758. © 2015 SETAC.

[Ecological effect of road network in the typical area of Yunnan Province based on integration of landscape pattern and process].

By using the quantitative index of 'probability of connectivity', this paper analyzed the effects of road network on the landscape pattern, ecological process, and landscape function in the typical areas of Yunnan Province. Road network accelerated landscape fragmentation, and changed the structure, number, and distribution pattern of ecological process dispersal paths, with the effects increased with increasing dispersal ability. The road network generally reduced the landscape function in maintaining ecological process connectivity by > 10% and the patch function by > 40%, and the effect also increased with increasing dispersal ability.

[Niches of plant species in wetlands of the Yellow River Delta under gradients of water table depth and soil salinity].

Ordination methods were used to arrange in turn the 19 plant species in wetlands of the Yellow River Delta under gradients of water table depth and soil salinity, and to classify them into three ecological species groups, i. e. low, medium, and high water table depth/soil salinity ecological species groups. Their niche breadths and niche overlaps under the two gradients were also analyzed. The results indicated that for the gradient of water table depth, the species in medium water table depth ecological species group, such as Phragmites australis and Suaeda salsa, occupied a broad niche breadth, and those in high water table depth ecological species group, such as Typha orientalis and Myriophyllum spicatum, occupied the narrowest niche breadth. For the gradient of soil salinity, the species in high soil salinity ecological species group, such as Suaeda salsa and Tamarix chinensis, occupied a broad niche breadth, while those belonging to the medium and low soil salinity ecological species groups occupied a narrow niche breadth. The niche overlaps changed regularly along the gradients of water table depth and soil salinity. In general, the niche overlaps between the plant species of the same ecological species groups were large, whilst those between the plant species of different ecological species groups were small. Niche differentiations of the plant species under the gradients of water table depth and soil salinity might promote species coexistence, and contribute to the explanation of plant zonation mechanisms in this Delta.

[Study on the spectrum response of Brassica Campestris L leaf to the zinc pollution].

In the present paper, the spectrum response of Brassica Campestris L leaf to the stress of heavy metal zinc pollution was studied in three spectral rangess of the red edge position (680-740 nm), the visible spectrum (460-680 nm) and the near infrared spectrum (750-1000 nm). The results indicate that the Zn content in cabbage leaves increases and the chlorophyll level reduces with the increase in Zn concentration in soil. With the Zn content of Brassica Campestris L leaves increasing, the leaf spectral reflectivity in visible light (A1) and the range of red edge shift (S) ascends, the the leaf spectral reflectivity in the near infrared light (A2) decreases. The three indices of A1, A2 and S are fitted much linearly with the logarithm of zinc content in Brassica Campestris L leaves with the high squared regression coefficients of 0.942, 0.981 and 0.969 respectively. The regression models are reliable to estimate the zinc content in Brassica Campestris L leaves.