Western Jilin province has the most serious area of soda salinization in Northeast China, which affects and restricts the sustainable development of agriculture. The effects of physico-chemical properties of rhizosphere and non-rhizosphere soil on soil microbial diversity and enzyme activities (polyphenol oxidase, catalase, invertase, amylase) were evaluated in typical soda saline-alkali paddy field. Community-level physiological profile (CLPP) based on Biolog-ECO plates was used to assess the functional diversity of soil microorganisms. Exchangeable sodium percentage (ESP) and pH were negative correlated with the microbial activity (AWCD), soil enzyme activities (amylase, sucrose, and catalase, except for polyphenol oxidase) in rice rhizosphere and non-rhizosphere soil (P < 0.05). The indexes of microbial diversity in rice rhizosphere soil were significantly higher than that of non-rhizosphere soil. The utilization of amino acids by rice rhizosphere microorganisms was relatively high, while non-rhizosphere soil had relatively high utilization of carboxylic acid, phenolic acid, and amine. Among the selected physico-chemical properties, soil organic carbon (SOC) and soil water content (SWC) had the greatest influence on the variation of microbial diversity indexes and enzyme activities in rhizosphere soil. ESP and pH showed a significant positive correlation with carbon source utilization, especially for amine (AM) and phenolic acid (PA) carbon source utilization (P < 0.05) by means of RDA, and the utilization rate of AM and PA carbon sources by rice rhizosphere and non-root soil microorganisms was P1 < P2 < P3.

Irrigation regime and fertilizer nitrogen (N) are considered as the most effective agricultural management systems to mitigate greenhouse gas (GHG) emissions from crop fields, but few studies have involved saline–alkaline paddy soil. Gas emitted from saline–alkaline paddy fields (1-year-old and 57-year-old) was collected during rice growing seasons by the closed chamber method. Compared to continuous flooding irrigation, lower average CH₄ flux (by 22.81% and 23.62%), but higher CO₂ flux (by 24.84% and 32.39%) was observed from intermittent irrigation fields. No significant differences of N₂O flux were detected. Application rates of N fertilizer were as follows: (1) No N (N0); (2) 60 kg ha⁻¹ (N60); (3) 150 kg ha⁻¹ (N150); and (4) 250 kg ha⁻¹ (N250). The cumulative emissions of GHG and N fertilizer additions have positive correlation, and the largest emission was detected at the rate of 250 kg N ha⁻¹ (N250). Global warming potential (GWP, CH₄ + N₂O + CO₂) of the 57-year-old field under the N250 treatment was up to 4549 ± 296 g CO₂-eq m⁻², approximately 1.5-fold that of N0 (no N application). In summary, the results suggest that intermittent irrigation would be a better regime to weaken the combined GWP of CH₄ and N₂O, but N fertilizer contributed positively to the GWP.

Road dust, which contains trace elements and certain organic matter that can be harmful to human health, plays an important role in atmospheric pollution. In this paper, concentrations of 16 elements in the road dust of Changchun, China were determined experimentally. A total of 100 samples were collected using plastic brushes and dustpans, and the elements were analyzed by an inductively coupled plasma optical emission spectrometer (ICP-OES). It was indicated that the elements could be divided into major and trace elements. The concentration of trace elements followed the trend: mercury (Hg) > manganese (Mn) > zinc (Zn) > lead (Pb) > chromium (Cr) > copper (Cu) > vanadium (V) > arsenic (As) > nickel (Ni) > cobalt (Co) > cadmium (Cd). Contamination-level-assessment calculated by the geo-accumulation index (I_geo) showed that the pollution-level ranged from non-contaminated to extreme contamination, while the calculations of enrichment factor (EF) showed that EF values exhibited a decreasing trend: Cd > Hg > As > Pb > Cu > Co > Zn > Ni > Cr > V > Mn > Mg > Fe > Sr > Ba. In our study, ingestion was the greatest exposure pathway for humans to intake trace elements by calculating the average daily dose (ADD) from three routes (ingestion, inhalation, and dermal contact). According to the health risk assessment results, the non-carcinogenic risks that human beings suffered from these elements were insignificant. Additionally, the hazard quotient (HQ) values were approximately one-tenth in the case of children. Meanwhile, the total excess cancer risk (ECR) was also lower than the acceptable level (10⁻⁶–10⁻⁴) for both adults and children.

Soil organic carbon (SOC) plays a critical role in carbon cycling and soil quality of agroecosystems. Understanding the factors influencing SOC and the main indicators for soil quality can help in better soil management and sustainable agriculture. In this study, we selected three upland fields (U1, U2 and U3) and three paddy fields (P1, P2 and P3) of saline-alkali agroecosystems to study the impacts of soil physico-chemical properties (soil pH, exchangeable sodium percentage, electrical conductivity and bulk density) and enzyme activities (soil amylase, invertase, catalase and polyphenol oxidase) on SOC dynamics. The soil pH and exchangeable sodium percentage (ESP) had profoundly negative effect on SOC. Soil amylase and invertase activities were significantly positively correlated with SOC in both upland and paddy fields. Catalase promoted the accumulation of paddy SOC and polyphenol oxidase led to the acceleration of decomposition of upland SOC. Additionally, we combined SOC contents, soil physico-chemical properties and soil enzyme activities together to obtain the main indicators of soil quality. The results suggested that, in upland sites, the main factors affecting the soil quality were soil pH, ESP and SOC. As for paddy sites, the main indicators of soil quality were soil pH, amylase and invertase. By comparing the soil quality indicators between upland and paddy fields, it was observed that the inhibiting effect of ESP on paddy soil quality was not as significant as on upland soil quality due to the irrigation practice of rice planting, which could reduce the degree of soil alkalization. Therefore, paddy development has been widely used to improve the saline-alkali land in western Jilin Province of China.