Heilongjiang is a “browning” river that receives substantial terrestrial organic matter, where reactivity of dissolved organic matter (DOM) may have important effect on ecosystem function and carbon biogeochemical cycle. However, little is known about microbial transformations of different DOM components, which could provide valuable insight into biogeochemical reactivity of DOM. In this study, bioavailability experiments were conducted for 55 days to determine changes of different DOM components by microbial transformations. Labile matter (C1) was detected only in initial DOM, and tryptophan-like substances (C4) were observed from day 5 onwards. Thus, three individual components were identified at each sampling time of the bioavailability experiment. The increase of Fₘₐₓ in DOM components revealed that microbial humic-like substances (C2), terrestrial humic-like substances (C3), and C4 were produced by microbial transformation, especially in the spring samples. Further, two-dimensional correlation spectroscopy (2D-COS) indicated that shorter wavelength tryptophan-like and microbial humic-like substances can be degraded by microbes or transformed into longer wavelength complex substances. Relatively simple microbial humic-like substances were preferentially produced compared to complex terrestrial humic-like substances. The results make sense to understand the biogeochemical cycling and environmental effects of DOM in the Heilongjiang River.

The acidification liquid of waste activated sludge (WAS) could be used as the additional carbon source of biological nutrient removal. Recently, the optimization of operating conditions for the acidification metabolites has attracted much attention. In this study, a three-factor Box-Behnken design (BBD) was applied to determine the relative importance of the various factors and the optimum operating during acidification using response surface method (RSM). The importance of the individual variables on the production of soluble chemical oxygen demand (SCOD) was suspended solids (SS) > shaking rate > initial oxidation-reduction potential (ORP). The increase on SS content led to a decrease on the acidification degree. Low SS could promote mass exchange and microbial activity. The maximum SCOD yield (9288.5 mg/L) was predicted under the optimum condition at 8.0 g/L SS, 144.0 mV initial ORP, and 60.0 r/min shaking rate. Also, the releasing of soluble protein and carbohydrate was calculated as responses. The individual effect of shaking rate and initial ORP had significant effect on soluble protein and carbohydrate releasing, respectively. This study would provide valuable information for increasing the efficiency of acidification.

In this modern era, the importance of information and communication technology (ICT) cannot be ignored for sustainable human development. However, Pakistan has experienced a considerable gap between ICT economic growth and human development. In this regard, this study has modeled the relationship between ICT, economic growth, and the human development index (HDI) considering urbanization, foreign direct investment (FDI), and trade for the period from 1990 to 2014. An autoregressive distributed lag (ARDL) and vector error correction model (VECM) approaches are used to analyze the data. The empirical results reveal that ICT promote human development index. Along with, economic growth has a positive and significant impact on human development. Besides, urbanization, trade, and FDI discourage human development in Pakistan. Finally, bidirectional causality is detected between the aforementioned variables. Recommendations to policymakers regarding the productive role of FDI and trade are provided.

The nexus among real income, energy consumption, financial development, and carbon emission has broadly conferred area in energy and environmental literature. However, there is no study in the literature which investigates the moderating role of financial development between real income, energy consumption, and CO₂ emission in Pakistan. This study reveals the role of financial development as a moderator in the conventional environmental Kuznets curve (EKC). To achieve the objectives of this study, two approaches are employed, (i) with main effects and (ii) with interaction variables, using autoregressive distributed lag (ARDL) bounds testing approach in the case of Pakistan covering the period 1970 to 2016. Findings of the empirical analysis confirm the EKC hypothesis in the first case (without interaction effect) and our second estimations (with interaction effect) show that financial development significantly moderates the association of real output with CO₂ emission (both for the long run and short run). The negative effect of financial development on carbon emission reveals to efficacious energy management with effective environmental performance. More precisely, the results of second estimations reveal that all three interaction variables are statistically significant but the EKC curve is no more. Thus, the current study proposes that the moderating effect of the financial sectors may be the possible reason which has been ignored by prior researchers and they found mix results regarding the existence of EKC in Pakistan. In addition, the Granger causality test confirms the feedback effect between real income and carbon emission and one-way causality from all the three interaction variables and financial development to CO₂ emission. Lastly, this study posits some important policy inferences in the perspective of new economic policy formation in Pakistan.

The use of neonicotinoid pesticides is widespread throughout agricultural regions, including the Prairie Pothole Region of North America. The occurrence of these pesticides to the abundant adjacent wetlands can result in impacts on nontarget insects, and cascading effects through wetland ecosystems. In the current study, field-based mesocosms were used to investigate the effects of multiple pulses of the neonicotinoid imidacloprid on the emergence and chironomid community composition, in an effort to simulate episodic rain events to Prairie Pothole Wetlands. Sediments from two local wetlands were placed into the mesocosm tanks and three imidacloprid pulses added, each 1 week apart at nominal concentrations of 0.2, 2.0, and 20 μg/L. Overall, a significant decrease in the emergence of adult chironomids was observed within the 2.0 μg/L and greater concentrations, with the subfamilies Chironominae and Tanypodinae showing a greater sensitivity than the members of the subfamily Orthocladiinae. The chironomid community also had a dose-related response, followed by a recovery of the community composition near the end of the experiment. Our results provide additional evidence that repeated pulses of imidacloprid may have effects on chironomids and other sensitive aquatic insects living within Prairie Pothole Wetlands, resulting in reduced food availability. We stress the need for continued monitoring of US surface waters for neonicotinoid compounds and the continuation of additional experiments looking into the impacts on aquatic communities.

Struvite precipitation has drawn much attention in the last decade as a green chemical process for phosphorus removal and recovery. Product purity affects the usefulness, and thus price, of the product when recovered struvite is sold as fertilizer. However, there is currently little research on struvite quality, as well as on models for accurately predicting. This paper presents an alternative approach to the traditional thermodynamic model where the solid with the largest positive saturation index precipitates first, depleting the concentrations of constituent ions before the next solid can precipitate. In the new thermodynamic approach, all solids with a positive saturation index precipitate simultaneously, and deplete the common pool of available ions in tandem. It was validated against experimental data, compared with the traditional thermodynamic models and a previously developed empirical model. The proposed new approach was more accurate than other models, except when both the ammonium nitrogen and magnesium concentrations were very low, a condition not likely to be encountered in industry. Therefore, this model is more suited for predicting the performance of struvite precipitation under varying wastewater conditions.

Southeast Asia has undergone rapid developments in terms of urbanization, economic and population growth. The progress in sewerage treatment infrastructure has not kept pace with such developments. The inadequacy and inefficiency of sewerage systems has prompted the release of untreated sewage into the aquatic environment of Southeast Asia causing many waterborne illnesses since surface water is utilized for recreational, agricultural and aquaculture purposes and, above all, as a source of water intake in Southeast Asia. This paper will review the current data on molecular markers of sewage pollution including sterols and linear alkylbenzenes (LABs) in Southeast Asian aquatic environment to clarify the state of sewage pollution and the competence of sewage treatment plants (STPs) in this area. Despite the importance of sewage pollution research in the region, the number of studies using molecular markers to trace the sources of sewage pollution is limited. So far, indicators of sewage pollution have been investigated in aquatic environments of Indonesia, Vietnam, Malaysia, the Philippines, Thailand, Cambodia and Brunei among Southeast Asian countries. The concentrations and diagnostic ratios of faecal sterols and LABs show the release of untreated and primary treated urban waste into water bodies of these countries. Further studies are required to fill the data gaps in Southeast Asia and come to a better understanding of the trends of sewage pollution in this part of the world. Graphical abstract

In the transportation of petroleum, large amount of oil polluted water will be produced, and the oil polluted water pumping into ocean will destroy ocean environment. To address oil-bearing ballast water, we fabricated a novel type of Fe–C microelectrolysis filler by using magnet powder, coconut shell biochar powder, bentonite, ammonium oxalate, and nickel powder. The COD and oil content removal efficiencies of 100 g/L oily wastewater were approximately 79.82% and 91.68%, respectively, after 100 min treatment at the following conditions: Fe–C mass ratio, 5:1; bentonite content, 20%; calcination temperature, 900 °C; calcination time, 2 h; ammonium oxalate content, 1.5%; and amount of nickel addition, 6.78%. The characteristics of the Fe–C microelectrolysis filler were analyzed. The surface structure of the filler was loose and porous, and its pores were developed. The Brunauer–Emmett–Teller (BET) surface area reached 49.4667 m² g⁻¹. A microelectrolysis filler is mainly mesoporous and contains large pores. Its average pore size is 2.6942 nm. Meanwhile, the results of our XRD analysis showed that some fillers were metal oxides, and most of them were simple metal substances.

Traditional composting processes must be conducted with a bulking agent to ensure adequate air space for aeration. The bulking agent and composting materials are always completely mixed. A novel layered structure was introduced in sewage sludge composting, in which no bulking agent was used and bamboo charcoal was used as a separating material. Three lab-scale composting reactors (A: sawdust and sludge; B: bamboo charcoal and sludge; and C: sawdust, bamboo charcoal, and sludge) were continuously operated for 29 days. Several physicochemical parameters were investigated to evaluate the feasibility of layered composting with bamboo charcoal. The results indicated that the maximum temperatures during the thermophilic stage in treatments A, B, and C were 51.4, 50.9, and 51 °C, respectively. Layered composting with bamboo charcoal decreased the pH of the thermophilic stage from 8.98 in A to 8.75 in C, and delayed the peaks by about 120 h. The degradation rates of dissolve organic carbon (DOC) and dissolved nitrogen (DN) were 75 and 71.5% in treatment B, respectively, which were significantly higher than those of control group A (60 and 59.1%, respectively). The total NH₃ emissions of treatment C (2127.8 mg) were significantly lower than those of A (2522.8 mg). Our results suggested that layered composting using bamboo charcoal as a separating material could be an alternative strategy to the traditional composting method. Moreover, layered composting combined with sawdust could effectively reduce NH₃ emissions and N loss.

Salts used in road de-icing during winter season inhibit the growth and development of lawn grass species. The mechanism of plant tolerance/sensitivity to such treatments is still not clear. Moreover, there is a lack of fast and non-invasive tool to detect the effect of these salts on plants growth. This study was designed to understand the tolerance mechanism of Kentucky bluegrass plants on salinity, based on some biometric and physiological parameters. In this experiment, we simulated the urban conditions where salts are used intensively for roads de-icing. Germination capacity was evaluated at five salt solutions of NaCl (0, 50, 100, 150 and 200 mM), and physiological parameters were measured during the tillering phase at salinity levels of 0, 150 and 300 mM of NaCl. Seeds of Kentucky bluegrass did not germinate under salinity. During tillering phase, salinity affected length, area and dry mass of roots as well as the relative water content of plants, negatively. Moreover, it influenced the maximum chlorophyll fluorescence yield, quantum yield of photosystem II and electron transport rate at early period of stress. This allows us to recommend these parameters for early detection of soil salinity effects on Kentucky bluegrass plants. It seems to be that the tolerance of this plant towards salinity is based on retaining water content in leaves that allow more efficient functioning of photosynthetic apparatus.