Identifying nitrogen (N) pollution sources is the fundamental work of non-point source pollution load reduction from watersheds, but is hard due to complex N transport and transformation within spatially heterogenized huge areas. During September 2011, we measured water characteristics and sediment N stable isotope in four tributaries of the upper reach of the Hun River, an important water source of the Dahuofang Reservoir, a large drinking water source in Northeast China. Results showed that spatial changes in SO₄²⁻and Cl⁻contents in the tributaries were consisted with the changes in density of the population living along the tributaries. Sediment δ¹⁵N from all tributaries showed a downstream increasing trend in line with the land use change, which is characterized as more farmlands and more people around the outlet area of each tributary. Principal component analysis indicated the population density had a strong impact on N in these tributaries in the low-flow period. Tributaries and villages close to the Dahuofang Reservoir should be the major N load control objects in reduction of non-point source nitrogen load from the upper reach of the Hun River.

Uncertainties exist in the water resources system, while traditional two-stage stochastic programming is risk-neutral and compares the random variables (e.g., total benefit) to identify the best decisions. To deal with the risk issues, a risk-aversion inexact two-stage stochastic programming model is developed for water resources management under uncertainty. The model was a hybrid methodology of interval-parameter programming, conditional value-at-risk measure, and a general two-stage stochastic programming framework. The method extends on the traditional two-stage stochastic programming method by enabling uncertainties presented as probability density functions and discrete intervals to be effectively incorporated within the optimization framework. It could not only provide information on the benefits of the allocation plan to the decision makers but also measure the extreme expected loss on the second-stage penalty cost. The developed model was applied to a hypothetical case of water resources management. Results showed that that could help managers generate feasible and balanced risk-aversion allocation plans, and analyze the trade-offs between system stability and economy.

Heavy metals, which have severe toxic effects on plants, animals, and human health, are serious pollutants of the modern world. Remediation of heavy metal pollution is utmost necessary. Among different approaches used for such remediation, phytoremediation is an emerging technology. Research is in progress to enhance the efficiency of this plant-based technology. In this regard, the role of rhizospheric and symbiotic microorganisms is important. It was assessed by enumeration of data from the current studies that efficiency of phytoremediation can be enhanced by assisting with diazotrophs. These bacteria are very beneficial because they bring metals to more bioavailable form by the processes of methylation, chelation, leaching, and redox reactions and the production of siderophores. Diazotrophs also posses growth-promoting traits including nitrogen fixation, phosphorous solubilization, phytohormones synthesis, siderophore production, and synthesis of ACC-deaminase which may facilitate plant growth and increase plant biomass, in turn facilitating phytoremediation technology. Thus, the aim of this review is to highlight the potential of diazotrophs in assisting phytoremediation of heavy metals in contaminated soils. The novel current assessment of literature suggests the winning combination of diazotroph with phytoremediation technology.

Nanoparticles (NPs) are widely used in many industrial applications. NP fate and behavior in seawater are a very important issue for the assessment of their environmental impact and potential toxicity. In this study, the toxic effects of two nanomaterials, silicon dioxide (SiO₂) and titanium dioxide (TiO₂) NPs with similar primary size (~20 nm), on marine microalgae Dunaliella tertiolecta were investigated and compared. The dispersion behavior of SiO₂ and TiO₂ NPs in seawater matrix was investigated together with the relative trend of the exposed algal population growth. SiO₂ aggregates rapidly reached a constant size (600 nm) irrespective of the concentration while TiO₂ NP aggregates grew up to 4 ± 5 μm. The dose–response curve and population growth rate alteration of marine alga D. tertiolecta were evaluated showing that the algal population was clearly affected by the presence of TiO₂ NPs. These particles showed effects on 50 % of the population at 24.10 [19.38–25.43] mg L⁻¹ (EC50) and a no observed effect concentration (NOEC) at 7.5 mg L⁻¹. The 1 % effect concentration (EC1) value was nearly above the actual estimated environmental concentration in the aquatic environment. SiO₂ NPs were less toxic than TiO₂ for D. tertiolecta, with EC50 and NOEC values one order of magnitude higher. The overall toxic action seemed due to the contact between aggregates and cell surfaces, but while for SiO₂ a direct action upon membrane integrity could be observed after the third day of exposure, TiO₂ seemed to exert its toxic action in the first hours of exposure, mostly via cell entrapment and agglomeration.

Daily PM₁₀ and PM₂.₅ samples were collected between April 2009 and July 2010 at a rural site (Sinop) situated on the coast of the Central Black Sea. The concentrations of PM₁₀ and PM₂.₅ were 23.2 ± 16.7 and 9.8 ± 6.9 μg m⁻³, respectively. Coarse and fine filters were analyzed for Cl⁻, NO₃ ⁻, SO₄ ²⁻, C₂O₄ ²⁻, PO₄ ³⁻, Na⁺, NH₄ ⁺, K⁺, Mg²⁺, and Ca²⁺ by using ion chromatography. Elemental and organic carbon content in bulk quartz filters were also analyzed. The highest PM₂.₅ contribution to PM₁₀ was found in summer with a value of 0.54 due to enhanced secondary aerosols in relation to photochemistry. Cl⁻, Na⁺, and Mg²⁺ illustrated their higher concentrations and variability during winter. Chlorine depletion was chiefly attributed to nitrate. Higher nssCa²⁺ concentrations were ascribed to episodic mineral dust intrusions from North Africa into the region. Crustal material (31 %) and sea salt (13 %) were found to be accounted for the majority of the PM₁₀. The ionic mass (IM), particulate organic matter (POM), and elemental carbon (EC) explained 13, 20, and 3 % of the PM₁₀ mass, correspondingly. The IM, POM, and EC dominated the PM₂.₅ (~74 %) mass. Regarding EU legislation, the exceeded PM₂.₅ values were found to be associated with secondary aerosols, with a particular dominance of POM. For the exceeded PM₁₀ values, six of the events were dominated by dust while two and four of these exceedances were caused by sea salt and mix events, respectively.

The injury to sensitive rotational crops caused by residual herbicides from their applications has happened frequently. The assessment of activity of residual herbicide in soil has been of agronomic concern. To accurately determine the toxicity and obtain a comparable concentration that inhibits growth by 50 % (IC50) in different soils, the concentrations of imazaquin in CaCl₂(CCₐCₗ₂) and H₂O (CH₂O) extraction and in in situ pore water (CPW) were adopted for the estimation of IC50 to sorghum. The IC50 values based on CCₐCₗ₂and CH₂Owere 0.06 mg L⁻¹in soil Ansai (AS) to 0.13 mg L⁻¹in soil Huajiachi (HJC), 0.32 mg L⁻¹in soil AS to 0.71 mg L⁻¹in soil HJC, respectively, with variation coefficients of 38.32 and 34.93 %. However, CPW-based IC50 values ranged from 0.90 mg L⁻¹in soil Xiaoshan (XS) to 1.09 mg L⁻¹in soil HJC with a variation coefficient of 6.96 %. This implies that the IC50 based on imazaquin concentration in in situ pore water is almost identical in the five soils. With further studies with more herbicides and plant species, this method might be expanded for the estimation of phytotoxicity of residual herbicide(s) to plant(s).

Biodegradability is a desired characteristic for synthetic soil amendments. Cross-linked polyacrylic acid (PAA) is a synthetic superabsorbent used to increase the water availability for plant growth in soils. About 4 % within products of cross-linked PAA remains as linear polyacrylic acid (PAAₗᵢₙₑₐᵣ). PAAₗᵢₙₑₐᵣhas no superabsorbent function but may contribute to the apparent biodegradation of the overall product. This is the first study that shows specifically the biodegradation of PAAₗᵢₙₑₐᵣin agricultural soil. Two¹³C-labeled PAAₗᵢₙₑₐᵣof the average molecular weights of 530, 400, and 219,500 g mol⁻¹were incubated in soil. Mineralization of PAAₗᵢₙₑₐᵣwas measured directly as the¹³CO₂efflux from incubation vessels using an automatic system, which is based on¹³C-sensitive wavelength-scanned cavity ring-down spectroscopy. After 149 days, the PAAₗᵢₙₑₐᵣwith the larger average molecular weight and chain length showed about half of the degradation (0.91 % of the initial weight) of the smaller PAAₗᵢₙₑₐᵣ(1.85 %). The difference in biodegradation was confirmed by the δ¹³C signature of the microbial biomass (δ¹³Cₘᵢc), which was significantly enriched in the samples with short PAAₗᵢₙₑₐᵣ(−13 ‰ against reference Vienna Pee Dee Belemnite,VPDB) as compared to those with long PAAₗᵢₙₑₐᵣ(−16 ‰ VPDB). In agreement with other polymer studies, the results suggest that the biodegradation of PAAₗᵢₙₑₐᵣin soil is determined by the average molecular weight and occurs mainly at terminal sites. Most importantly, the study outlines that the size of PAA that escapes cross-linking can have a significant impact on the overall biodegradability of a PAA-based superabsorbent.

Species sensitivity distribution (SSD) is the most common method used to derive water quality criteria, but there are still issues to be resolved. Here, issues associated with application of SSD methods, including species selection, plotting position, and cutoff point setting, are addressed. A preliminary improvement to the SSD approach based on post-stratified sampling theory is proposed. In the improved method, selection of species is based on biota of a specific basin, and the whole species in the specific ecosystem are considered. After selecting species to be included and calculating the cumulative probability, a new method to set the critical threshold for protection of ecosystem-level structure and function is proposed. The alternative method was applied in a case study in which a water quality criterion (WQC) was derived for ammonia in the Songhua River (SHR), China.

With growing concerns about food safety and stricter national standards in China, attention has focused on vegetables and fish as they are an important part of the Chinese daily diet, and pesticide residues can accumulate in these foodstuffs. The local consumption habits of vegetables and fish were determined using questionnaires distributed in the major regions of the northern metropolis. Then, the samples of fruit-like vegetables, leafy and root vegetables, and five species of fish (freshwater and marine) were collected from supermarkets and traditional farmers’ markets in the city. The concentrations and profiles of pesticide residues (hexachlorocyclohexane (HCH), dichlorodiphenyl trichloroethane (DDT), and endosulfan) in the samples were determined and compared. For the vegetables, the concentration ranges of ΣDDT, ΣHCH, and Σendosulfan were not detectable (ND) to 10.4 ng/g fresh weight (f.w.), ND to 58.8 ng/g f.w., and ND to 63.9 ng/g f.w., respectively. For the fish samples, the corresponding values were 0.77–25.0 ng/g f.w., 0.02–1.42 ng/g f.w., and 1.22–22.1 ng/g f.w., respectively. Only one celery sample exceeded the maximum residue limits (MRLs) of HCH residues set by Chinese regulations (GB2763-2014). The estimated daily intakes (EDIs) and hazard ratios (HRs) were calculated using data from the recently published Exposure Factors Handbook for the Chinese Population. The EDIs and HRs showed that the levels of organochlorine pesticide (OCP) residues in vegetables and fish in this area are safe.

Phytoextraction is widely used for the reclamation of degraded sites, particularly to remove trace metals from contaminated soils. Whereas this technique demonstrates several advantages, the biomass resulting from phytoextraction processes is highly enriched in metallic elements and constitutes therefore a problematic waste. We show here that this biomass can be used for the preparation of novel polymetallic extracts, with high potential as catalysts or reagents in organic synthesis. This new concept of ecocatalysis constitutes an innovative recycling of metallic elements whose current known reserves could be exhausted in the coming decades. The ecocatalysts Eco-Zn and Eco-Ni prepared respectively from Zn and Ni hyperaccumulating plants display two distinct chemical reactivities, starting from the same substrates. Eco-Zn led to the formation of esters of commercial interest for the fragrance industry, following a hydro-acyloxy-addition reaction pathway. In contrast, Eco-Ni afforded chlorinated products thank to the hydrochlorination of alkenes. Both ecocatalysts allowed the synthesis of valuable products in high yields through methodologies in line with the spirit of sustainable chemistry.