Quantification of pesticide residues on plastic mulching films in typical farmlands of the North China

• Pesticide residuals on mulching film of Shandong, Tianjin and Hebei. • Detected 29 pesticides in soil and 30 in mulching film. • Pesticides on plastic films: 86.4‒22213.2 ng/g and in soil: 9.3‒535.3 ng/g. • Pesticides on plastic films 20 times higher than in soil. Plastic debris as new pollutants attracts much attention in the recent years. The plastic mulching films is one of the most important plastic debirs source in the environment. The aim of this work was to investigate the current status of pesticide residues on the plastic mulching films. Based on the QuEChERS method, multi-residue methods for detection of pesticide residues with gas chromatography tandem mass spectrum (GC-MS) and high performance liquid chromatography tandem mass spectrum (HPLC-MS) were developed for the analysis of the pesticides residues in plastic film and soil samples from Tianjin, Hebei and Shandong. The total concentrations of pesticide residues were in the range of 86.4‒22213.2 ng/g in plastic film debris, which was about 20 times higher than that in soil (9.3‒535.3 ng/g). Residual level of pesticides varied greatly in different samples. The historical usage and recent application of pesticides were the main sources for pesticide residues on plastic films and soil. In short, plastic mulching films could act as a sink for pesticides in farmland and the ubiquitous pesticide residues on plastic films should draw more attention.     

基于重金属有效态的农田土壤重金属污染评价研究

目前农田土壤重金属污染评价以重金属全量为依据,而评价农田土壤重金属污染影响时主要考虑农产品安全从而保障人体健康,农作物对重金属的吸收积累量则取决于土壤中有效态重金属含量。在阐述土壤重金属有效态定义的基础上,综合分析了土壤重金属有效态的影响因素及其与土壤中重金属全量和农作物中重金属含量的相关性,概括了土壤重金属有效态在土壤重金属污染评价中的应用,以期提出建立以土壤重金属有效态含量为基础、结合土壤重金属全量及作物中吸收的重金属含量的土壤重金属污染评价体系。     

Farmland damage and its impact on the overlapped areas of cropland and coal resources in the eastern plains of China

The subsidence caused by coal mining in areas where cropland and coal resources overlap in the eastern plains of China with high ground water levels has caused large amounts of water to collect in cropland, significant damage to cropland, and a sharp contradiction between people and land distribution within this region. Systematic analysis and calculation were conducted on these areas by using GIS spatial overlay analysis technology, subsidence and occupied cropland estimation models, and crop yield reduction prediction model to reveal the overlapped characteristics and extent of farmland damage, as well as to evaluate the effects of farmland damage to grain yield, farmland landscape, agricultural population, and dynamical equilibrium of the total cultivated land. Results showed that the overlapped areas of cropland and coal resources on the eastern plains of China occupied an area covering 1.33 × 10⁵ km², which accounted for 31.93% of the total cropland area. In 2020, the accumulative total area of destroyed cropland reached 3.83 × 10³ km², thus reducing grain yield by 9.63 × 10⁸ kg, and increasing the number of landless farmers to 1.91 × 10⁶. Furthermore, the quality and production capacity of cultivated land decreased, farmland landscape patterns changed, land patterns and structures were adjusted, the dynamical equilibrium of the total cultivated land was difficult to guarantee, and social instability increased in coal mining subsidence areas. These findings provided a scientific basis for relevant government departments to enact countermeasures for the coordinative production of coal and grain.     

Contamination Characteristics and Degradation Behavior of Low-Density Polyethylene Film Residues in Typical Farmland Soils of China

Low-density polyethylene (LDPE) film residues left in farmlands due to agricultural activities were extensively investigated to evaluate the present pollution situation by selecting the typical areas with LDPE film application, including Harbin, Baoding, and Handan of China. The survey results demonstrated that the film residues were ubiquitous within the investigaed areas and the amount reached 2400–8200 g ha^?1. Breakage rates of the film residues were almost at the same level in the studied fields. There were relatively small amounts of film residues remaining in neighboring farmland fields without application of LDPE film. The studies showed that the sheets of LDPE residues had the same oxidative deterioration, which was probably due to photodegradation instead of biodegradation. The higher molecular weight components of the LDPE film gradually decreased, which were reflected by the appearance of some small flakes detached from the film bodies. LDPE films in the investigated fields gradually deteriorated and the decomposing levels developed with their left time increasing. The degradation behaviors of LDPE films were confirmed by using Fourier transform infrared (FTIR), scanning electron microscopic (SEM), and gel permeation chromatography analyses.     

宝鸡市麟游县煤矿区周边农田土壤重金属污染安全评价

文章选取麟游县的北马坊煤矿、郭家河煤矿和北王煤矿为研究区域,对其周边的农田土壤进行野外采样和室内分析,测定Zn、Cr、Pb、Cu、Cd、Hg、As 7种重金属的污染状况。结果表明:测定的7种重金属元素的最大值均超过了陕西省土壤背景值和当地的土壤环境背景值。单因子污染指数评价得出,三矿区周边的土壤Hg元素的污染较严重,局部地区已经达到了重度污染;综合污染指数法评价得出,三矿区均达到了中度到重度污染水平,其中北王煤矿污染水平较高;地质累积指数法评价得出,三矿区Hg元素的累积程度属于中度污染到强污染等级,Cd元素次之。因此3矿区周边的耕地土壤已不同程度的受到重金属的污染,相关部门应该采取一定的措施治理该区的土壤。     

Pollinator insects benefit from rotational fallows

The importance of rotational fallows for pollinating insects in intensively cultivated farmland was studied in a three-year field experiment. The focus was on the establishment method (undersowing or seed mixture sown post-tillage), seed mixture (competitive Festuca pratensis-Phleum pratense-Trifolium pratense or less competitive Agrostis capillaris-Festuca ovina mixture) and duration (1 or 2 years) of the fallow. The seed mixture and duration affected the pollinators more than the method of establishment. Pollinator species richness was higher in fallows sown with less competitive than with competitive grasses and it increased in the second year. Stubble fields reached as high pollinator species richness already during the first year as fallows with less competitive grasses did in the second year. Pollinator abundance was highest in those treatments in which species richness of flowering plants was highest. The results suggest that the benefits of rotational fallows for pollinators increase when they are established as stubble or using seeds of less competitive grasses and when the field is fallowed for (at least) two summers.     

新疆焉耆盆地农田土壤重金属污染及健康风险评价

为研究新疆焉耆盆地绿洲农田土壤重金属的污染及潜在健康风险,选取194个样点采集土壤样品,测定As、Cd、Cr、Cu、Ni、Pb和Zn共7种重金属元素含量。利用地质累积指数(I_(geo))评价农田土壤污染水平,采用US EPA健康风险评价模型,对农田土壤重金属污染的潜在健康风险进行评估。结果表明,研究区农田土壤7种重金属平均含量均未超出《食用农产品产地环境质量评价标准》中的限值,但Cd、Cr、Ni、Pb和Zn含量平均值分别超出新疆灌耕土背景值的1.67、1.41、1.30、3.01和6.78倍。农田土壤中Zn呈现轻度污染,Cd与Pb呈现轻微污染,As、Cr、Cu与Ni呈现无污染态势。健康风险评估结果表明,经手-口摄入是研究区农田土壤重金属日均暴露量及健康风险主要途径。农田土壤7种重金属通过3种暴露途径的非致癌风险商(HQ)与非致癌风险指数(HI),单项致癌风险指数(CR)与总致癌风险指数(TCR)均小于安全阈值,属于可接受风险水平。研究区农田土壤重金属对儿童的非致癌风险低于成人,致癌风险高于成人。研究区农田土壤中As与Pb是最主要的非致癌风险因子,As是最主要的致癌风险因子,研究区农田土壤中As对人体的健康风险应当引起重视。     

富蕴县耕地土壤环境质量现状

通过在富蕴县建立测土配方施肥示范点，开展了耕地土壤环境质量的调查，结果表明：在富蕴县不同地貌部位0 cm~20 cm耕层土壤中，土壤常量元素的分布与微量元素相比差异较大；在山区土壤中，常量元素与微量元素的含量较高，而在戈壁沙漠地带，土壤中常、微量元素的含量均表现为最低水平；土壤pH值为7.5~8.5，适合作物生长；土壤耕层盐分含量相对较低，仅表现为轻盐化土壤类型，占总耕地面积的12.52%。     

The Use of Cluster Analysis in Distinguishing Farmland Prone to Residential Development: A Case Study of Sterling, Massachusetts

k -means nonhierarchical cluster analysis using farm size, slope, and distance to the nearest city center and highway as surrogates of farmland conversion. Discriminant analysis showed that the two groups derived from the cluster analysis were 98.8% accurate (P < 0.0000). Results from the statistical analysis may serve as a starting point for the identification of individual farms prone to residential development. To explain the driving forces of farmland conversion to residential uses, interviews should be conducted with farmers, landowners, and land buyers. The use of multivariate statistical techniques to identify farms in jeopardy of residential development, in conjunction with qualitative assessments that explain the probability of development of individual farms, may prove a useful strategy to understand and predict farmland conversion.