Since the Industrial Revolution, the global ambient O3 concentration has more than doubled. Negative impact of O3 on some common crops such as wheat and soybeans has been widely recognized, but there is relatively little information about maize, the typical C4 plant and third most important crop worldwide. To partly compensate this knowledge gap, the maize cultivar (Zhengdan 958, ZD958) with maximum planting area in China was exposed to a range of chronic ozone (O3) exposures in open top chambers (OTCs). The O3 effects on this highly important crop were estimated in relation to two O3 metrics, AOT40 (accumulated hourly O3 concentration over a threshold of 40 ppb during daylight hours) and POD6 (Phytotoxic O3 Dose above a threshold flux of 6 nmol O3 m−2 s−1 during a specified period). We found that (1) the reduced light-saturated net photosynthetic rate (Asat) mainly caused by non-stomatal limitations across heading and grain filling stages, but the stomatal limitations at the former stage were stronger than those at the latter stage; (2) impact of O3 on water use efficiency (WUE) of maize was significantly dependent on developmental stage; (3) yield loss induced by O3 was mainly due to a reduction in kernels weight rather than in the number of kernels; (4) the performance of AOT40 and POD6 was similar, according to their determination coefficients (R2); (5) the order of O3 sensitivity among different parameters was photosynthetic parameters > biomass parameters > yield-related parameters; (6) Responses of Asat to O3 between heading and gran filling stages were significantly different based on AOT40 metric, but not POD6. The proposed O3 metrics-response relationships will be valuable for O3 risk assessment in Asia and also for crop productivity models including the influence of O3.

Biochar has a wide range of feedstocks, and different feedstocks often resulted in different properties, such as element distribution and heavy metal immobilization performance. In this work, batch experiments were conducted to assess the effectiveness of biochar pyrolyzed from kitchen waste (KWB), corn straw (CSB), and peanut hulls (PHB) on immobilization of Cd and Pb in contaminated soil by planting swamp cabbage (Ipomoea aquatica Forsk.) with a combination of toxicological and physiological tests. The results showed that biochar could all enhance the soil pH, and reduce extractable Pb and Cd in soil by 22.61%–71.01% (KWB), 18.54%–64.35% (CSB), and 3.28%–60.25% (PHB), respectively. The biochar led to a drop in Cd and Pb accumulation in roots, stems, and leaves by 45.43%–97.68%, 59.13%–96.64%, and 63.90%–99.28% at the dosage of 60.00 mg/kg, respectively. The root length and fresh weight of swamp cabbage were promoted, while superoxide dismutase (SOD) and peroxidase (POD) decreased after biochar treatment. The distribution of heavy metal fractions before and after biochar treatment indicated that biochar could transform Cd and Pb into a state of lower bioavailability, thus inhibiting Cd and Pb uptake by swamp cabbage. Biochar with different feedstocks could be ranked by the following order according to immobilization performance: KWB > CSB > PHB.

Bitumen recovery from oil sands in northeastern Alberta, Canada produces large volumes of tailings, which are deposited in mining areas that must be reclaimed upon mine closure. A new technology of non-segregated tailings (NST) developed by Canadian Natural Resources Limited (CNRL) was designed to accelerate the process of oil sands fine tailings consolidation. However, effects of these novel tailings on plants used for the reclamation of oil sands mining areas remain to be determined. In the present study, we investigated the effects of NST on seedlings of three species of plants commonly planted in oil sands reclamation sites including paper birch (Betula papyrifera), white spruce (Picea glauca) and green alder (Alnus viridis). In the controlled-environment study, we grew seedlings directly in NST and in the two types of reclamation soils with and without added NST and we measured seedling growth, gas exchange parameters, as well as tissue concentrations of selected elements and foliar chlorophyll. White spruce seedlings suffered from severe mortality when grown directly in NST and their needles contained high concentrations of Na. The growth and physiological processes were also inhibited by NST in green alder and paper birch. However, the addition of top soil and peat mineral soil mix to NST significantly improved the growth of plants, possibly due to a more balanced nutrient uptake. It appears that NST may offer some advantages in terms of site revegetation compared with the traditional oil sands tailings that were used in the past. The results also suggest that, white spruce may be less suitable for planting at reclamation sites containing NST compared with the two studied deciduous tree species.

Planting leafy vegetables, especially pakchoi, in cadmium (Cd) polluted farmland is easy to lead to excessive Cd content in edible parts, which results in high risk of food chain. In this study, a field experiment was carried out to study the effects of intercropping of pakchoi with Cd hyperaccumulator Sedum alfredii Hance, and the roles of endophytic bacterium SaMR12 was also investigated. When intercropping with Sedum, the growth of pakchoi was not affected but their Cd concentration and accumulation were significantly increased, while which were obviously decreased by SaMR12 inoculation. After intercropping, the biomass of Sedum was significantly reduced, but their Cd concentration increased. SaMR12 inoculation significantly increased Cd accumulation of Sedum, and which increased to 3 times in Sedum monoculture. Those results showed that although intercropping with hyperaccumulator could lead to higher risk of pakchoi in Cd polluted field, intercropping with SaMR12 inoculated Sedum can decrease Cd concentration of pakchoi and promote Cd absorption of Sedum, which indicated that this endophyte can be made into a microbial inoculum as a soil additive for the safe production of vegetables and the soil Cd pollution remediation.

As one of the most cost-effective and sustainable methods for contaminants' removal, sequestration and/or detoxification, phytoremediation has already captured comprehensive attention worldwide. Nevertheless, the accurate effects of various spatial pattern in enhancing phytoremediation efficiency is not yet clear, especially for the polluted mining areas. This study designed nine planting patterns (monocropping, double intercropping and triple intercropping) of three indigenous plant species (Setaria viridis (L.), Echinochloa crus-galli (L.) and Phragmites australis (Cav.) Trin. ex Steud.) to further explore the effects of plants spatial pattern on phytoremediation efficiency. Considering the uncertainties of the residual contaminants' concentration (RCC) caused by soil anisotropy, permeability and land types, the interval transformation was introduced into the plant uptake model to simulate the remediation efficiency. Then multi-criteria decision analysis (MCDA) were applied to optimal the planting patterns, with the help of criteria of (a) the amount of heavy metal absorption; (b) the concentration of residual contaminant in soil; (c) root tolerance of heavy metals; (d) the total investment cost. Results showed that (1) the highest concentrations of Zn, Cd, and Pb of the polluted area were 7320.02, 14.30, 1650.51 mg kg⁻¹ (2) During the 180 days simulation, the highest RMSE of residue trace metals in soil are 3.02(Zn), 2.67(Pb), 2.89(Cd), respectively. (3) The result of IMCDA shows that the planting patterns of Setaria viridis, Echinochloa crus-galli and Phragmites australis in alternative a9 (269 mg kg⁻¹ year⁻¹) had the highest absorption rate of heavy metals compared with a7 (235 mg kg⁻¹ year⁻¹) and a2 (240 mg kg⁻¹ year⁻¹). After 20 years of remediation, the simulated RCC in a9 is far below the national standard, and the root toxicity is 0.12 (EC ≤ EC₂₀). In general, the optimal alternative derived from interval residual contaminant concentration can effectively express the dynamic of contaminant distribution and then can be effectively employed to evaluate the sustainable remediation methods.

Dietary consumption of contaminated vegetables may contribute to polycyclic aromatic hydrocarbon (PAH) exposure in humans; however, this exposure pathway has not been examined thoroughly. This study aims to characterize the concentrations of PAHs in six types of vegetables grown near industrial facilities in Shanghai, China. We analyzed 16 individual PAHs on the US EPA priority list, and the total concentration in vegetables ranged from 65.7 to 458.0 ng g−1 in the following order: leafy vegetables (romaine lettuce, Chinese cabbage and Shanghai green cabbage) > stem vegetables (lettuce) > seed and pod vegetables (broad bean) > rhizome vegetables (daikon). Vegetable species, wind direction, and local anthropogenic emissions were determinants of PAH concentrations in the edible part of the vegetable. Using isomer ratios and principal component analysis, PAHs in the vegetables were determined to be mainly from coal and wood combustion. The sources of PAHs in the six types of vegetables varied. Daily ingestion of PAHs due to dietary consumption of these vegetables ranged from 0.71 to 14.06 ng d−1 kg−1, with contributions from Chinese cabbage > broad bean > romaine > Shanghai green cabbage > lettuce > daikon. The daily intake doses adjusted by body weight in children were higher than those in teenagers and adults. Moreover, in adults, higher concentrations of PAHs were found in females than in males. For individuals of different age and gender, the incremental lifetime cancer risks (ILCRs) from consuming these six vegetables ranged from 4.47 × 10−7 to 6.39 × 10−5. Most were higher than the acceptable risk level of 1 × 10−6. Our findings demonstrate that planting vegetables near industrial facilities may pose potential cancer risks to those who consume the vegetables.

To evaluate the ozone (O3) sensitivity among peach tree (Prunus persica) cultivars widely planted in Beijing region and explore the possible eco-physiological response mechanisms, thirteen cultivars of peach seedlings were exposed to either charcoal-filtered air or elevated O3 (E-O3, non-filtered ambient air plus 60 ppb) for one growing season in open-top chambers. Leaf structure, stomatal structure, gas exchange and chlorophyll a fluorescence, photosynthetic pigments, antioxidant defense system and lipid peroxidation were measured in three replicated chambers. Results showed that E-O3 significantly reduced abaxial epidemis thickness, but no effects on the thicknesses of adaxial epidemis, palisade parenchyma and spongy parenchyma. Stomatal area, density and conductance were not significantly affected by E-O3. E-O3 significantly accelerated leaf senescence, as indicated by increased lipid peroxidation and more declines in light-saturated photosynthetic rate and pigments contents. The reduced ascorbate content (ASC) was decreased but antioxidant enzyme activity (CAT, APX and SOD) and total antioxidant capacity (TAC) were significantly increased by E-O3 among cultivars. The cultivars with visible symptoms also had more reductions in net photosynthetic rate than those without visible symptoms. Ozone sensitivity among cultivars was strongly linked to leaf mass per area (LMA), antioxidant enzymes activity e.g. SOD, APX rather than stomatal parameters (stomatal area, density and conductance) and ASC. Results could provide a theoretical basis for selecting and breeding the ozone-resistant cultivars of peach trees grown in high O3-polluted regions.

Green streets are increasingly being used as a stormwater management strategy to mitigate stormwater runoff at its source while providing other environmental and societal benefits, including connecting pedestrians to the street. Simultaneously, human exposure to particulate matter from urban transportation is of major concern worldwide due to the proximity of pedestrians, drivers, and cyclists to the emission sources. Vegetation used for stormwater treatment can help designers limit the exposure of people to air pollutants. This goal can be achieved through the deliberate placement of green streets, along with strategic planting schemes that maximize pollutant dispersion. This communication presents general design considerations for green streets that combine stormwater management and air quality goals. There is currently limited guidance on designing green streets for air quality considerations; this is the first communication to offer suggestions and advice for the design of green stormwater streets in regards to their effects on air quality. Street characteristics including (1) the width to height ratio of the street to the buildings, (2) the type of trees and their location, and (3) any prevailing winds can have an impact on pollutant concentrations within the street and along sidewalks. Vegetation within stormwater control measures has the ability to reduce particulate matter concentrations; however, it must be carefully selected and placed within the green street to promote the dispersion of air flow.

Many reports of trees' impacts on urban air quality neglect pattern and process at the landscape scale. Here, we describe brief campaigns to quantify the effect of trees on the dispersion of airborne particulates using high time resolution measurements along short transects away from roads. Campaigns near major highways in Queens, NY showed frequent, stochastic spikes in PM2.5. The polydisperse PM2.5 class poorly represented the behavior of discrete classes. A transect across a lawn with trees had fewer spikes in PM2.5 concentration but decreased more gradually than a transect crossing a treeless lawn. This coincided with decreased Turbulence Kinetic Energy downwind of trees, indicating recirculation, longer residence times and decreased dispersion. Simply planting trees can increase local pollution concentrations, which is a special concern if the intent is to protect vulnerable populations. Emphasizing deposition to leaf surfaces obscures the dominant impact of aerodynamics on local concentration.

This is the longest continuous experiment where ethylenediurea (EDU) was used to protect plants from ozone (O3). Effects of long-term ambient O3 exposure (23 ppm h AOT40) on biomass of an O3 sensitive poplar clone (Oxford) were examined after six years from in-ground planting. Trees were irrigated with either water or 450 ppm EDU. Above (−51%) and below-ground biomass (−47%) was reduced by O3 although the effect was significant only for stem and coarse roots. Ambient O3 decreased diameter of the lower stem, and increased moisture content along the stem of not-protected plants (+16%). No other change in the physical wood structure was observed. A comparison with a previous assessment in the same experiment suggested that O3 effects on biomass partitioning to above-ground organs depend on the tree ontogenetic stage. The root/shoot ratios did not change, suggesting that previous short-term observations of reduced allocation to tree roots may be overestimated.