甘肃农田耕层土壤地膜残留分布特征及影响因素

Distribution and influencing factors of plastic film residues in topsoil of farmland in Gansu Province

  • 摘要: 甘肃是全国地膜用量、覆盖面积较大和覆盖时间较长的省份, 地膜覆盖种植产生的残留地膜是影响农业绿色可持续发展的一个突出问题。通过在甘肃全省主要覆膜农田布设960个监测样地, 结合样品采集与农户调查方式, 对0~30 cm耕层土壤地膜残留分布特征及影响因素进行调查, 评估农田地膜残留现状, 为防控治理提供工作参考。结果表明: 960个样地耕层土壤均有不同程度的地膜残留, 地膜残留量为0.02~204.75 kg·hm−2, 地膜残留量中位数为12.96 kg·hm−2。地膜残留量处于清洁阈值(<75 kg∙hm−2)、轻度污染阈值(75~120 kg∙hm−2)、中度污染阈值(120~270 kg∙hm−2)、重度污染阈值(>270 kg∙hm−2)的样地占比分别为97.6%、1.8%、0.6%、0, 轻度、中度污染阈值样地大多位于河西灌溉农业区, 而所有县域、市域、区域农田地膜残留量全部小于75 kg∙hm−2。地膜残留量受覆膜年限、种植作物类型、种植户类型、回收方式等因素影响: 覆膜年限11~20 a、>20 a地膜残留量显著高于6~10 a (P<0.05), 呈现出年限越长残留量越大的趋势; 制种作物地块地膜残留量最大、设施蔬菜地块地膜残留量最小, 前者达到后者的7倍左右, 制种作物、经济作物、玉米、马铃薯、露地蔬菜、中药材地块地膜残留量显著高于设施蔬菜(P<0.05); 合作社地块的地膜残留量显著高于一般农户(P<0.05), 约为一般农户的1.5倍; 农田残膜通过人工捡拾、人工捡拾+机械回收、机械回收3种方式进行离田回收, 并以人工捡拾为主, 但是人工+机械回收的地膜残留量显著高于人工回收(P<0.0001); 相对而言, 种植作物类型是造成研究区地膜残留量空间变化的主导因素。残膜由农户回收整理后通过商贩到田现场收购、网点组织统一回收或农户自行以旧换新3种方式转运到加工企业进行再生加工后全部得到资源化利用。调查表明, 甘肃农田耕层土壤地膜残留空间分布差异较大, 总体上处于较轻水平, 呈现出少数样地污染、面上整体清洁的特征。建议以减量、回收、替代并重思路为导向进一步做好地膜残留防控工作。本研究可为进一步完善甘肃地膜科学使用回收政策和机制提供数据支撑。

     

    Abstract: The application of agricultural film mulching technology has greatly promoted the development of agriculture in arid and semi-arid areas. Gansu Province has a large amount film, large coverage area, and long coverage time for plastic film mulching on farmland. The residual plastic film produced by plastic film mulching is a prominent problem that affects the green and sustainable development of agriculture. In this study, the distribution and influencing factors of plastic film residue in the 0–30 cm soil of farmland were investigated by setting up 960 monitoring sample sites in the main areas with mulched farmland of Gansu Province, combined with sample collection and farmer survey methods. This study aimed to evaluate the current status of plastic film residue in farmlands and provide guidance for prevention and control measures of pollution of plastic film residues in Gansu Province. The results showed that the residual amount of plastic film was 0.02−204.75 kg·hm−2, and the median of plastic film residues was 12.96 kg·hm–2 in 960 sites. Most of the mild and moderate pollution sites were located in Hexi-irrigated agricultural areas. Among them, the proportion of plastic film residues was 97.6% at the clean threshold (less than 75 kg·hm−2), 1.8% at mild pollution threshold (75−120 kg·hm−2), 0.6% at moderate pollution threshold (120−270 kg·hm−2), and 0 at severe pollution threshold (higher than 270 kg·hm−2), respectively. The residual amount of plastic film was affected by the number of film mulching years, type of planting crops, type of planters, recycling methods, and other factors. The residual amount of plastic film with film mulching years of 11−20 years and >20 years was significantly higher than that with film mulching years of 6−10 years (P<0.05), and the longer the age, the greater the residue. The amount of residues of the seed crop site was the largest at nearly seven times that of the greenhouse vegetables site. Plastic film residues in the fields of seed crops, economic crops, maize, potato, outdoor vegetables, and Chinese herbal medicine were significantly higher than those in the fields of greenhouse vegetables (P<0.05). The residual amount of the cooperative field was 1.5 times that of the general farmers. The farmland residual film was recovered in three ways: manual picking up, manual picking up + mechanical recycling, and mechanical recycling. The amount of residual film in fields with the recovery method of manual picking up + mechanical recycling was significantly higher than that with manual picking up (P<0.0001). Type of planting crops was the dominant factor causing spatial changes in plastic film residues in the study area. After removal from the farmland, the residual film was regenerated and processed through merchants purchasing, networks recycling, or farmers’ exchanging. This survey of residual plastic films showed that the spatial distribution of plastic film residues in farmland soil was quite different in Gansu Province, and the residual plastic film in the topsoil of farmland was generally at a low level, showing the distribution of pollution at a few sites and overall cleanliness on the surface. Prevention and control of plastic film residues should be further carried out under the guidance of reduction, recovery, and substitution. This study provides data for further improvement of policies and mechanisms for the scientific use and recycling of plastic films in Gansu Province.

     

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