Phillips Theresa M, Seech Alan G, Lee Hung, Trevors Jack T
Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1.
Biodegradation. 2005 Aug;16(4):363-92. doi: 10.1007/s10532-004-2413-6.
The organochlorine pesticide Lindane is the gamma-isomer of hexachlorocyclohexane (HCH). Technical grade Lindane contains a mixture of HCH isomers which include not only gamma-HCH, but also large amounts of predominantly alpha-, beta- and delta-HCH. The physical properties and persistence of each isomer differ because of the different chlorine atom orientations on each molecule (axial or equatorial). However, all four isomers are considered toxic and recalcitrant worldwide pollutants. Biodegradation of HCH has been studied in soil, slurry and culture media but very little information exists on in situ bioremediation of the different isomers including Lindane itself, at full scale. Several soil microorganisms capable of degrading, and utilizing HCH as a carbon source, have been reported. In selected bacterial strains, the genes encoding the enzymes involved in the initial degradation of Lindane have been cloned, sequenced, expressed and the gene products characterized. HCH is biodegradable under both oxic and anoxic conditions, although mineralization is generally observed only in oxic systems. As is found for most organic compounds, HCH degradation in soil occurs at moderate temperatures and at near neutral pH. HCH biodegradation in soil has been reported at both low and high (saturated) moisture contents. Soil texture and organic matter appear to influence degradation presumably by sorption mechanisms and impact on moisture retention, bacterial growth and pH. Most studies report on the biodegradation of relatively low (< 500 mg/kg) concentrations of HCH in soil. Information on the effects of inorganic nutrients, organic carbon sources or other soil amendments is scattered and inconclusive. More in-depth assessments of amendment effects and evaluation of bioremediation protocols, on a large scale, using soil with high HCH concentrations, are needed.
有机氯农药林丹是六氯环己烷（HCH）的γ异构体。工业级林丹含有HCH异构体的混合物，其中不仅包括γ-HCH，还含有大量主要为α-、β-和δ-HCH。由于每个分子上氯原子的取向不同（轴向或赤道向），每种异构体的物理性质和持久性也有所不同。然而，所有这四种异构体在全球范围内都被视为有毒且难降解的污染物。人们已经在土壤、泥浆和培养基中研究了HCH的生物降解，但关于包括林丹本身在内的不同异构体的大规模原位生物修复的信息却非常少。已经报道了几种能够降解并将HCH用作碳源的土壤微生物。在选定的细菌菌株中，编码参与林丹初始降解的酶的基因已被克隆、测序、表达并对基因产物进行了表征。HCH在有氧和无氧条件下均可生物降解，不过通常仅在有氧系统中观察到矿化现象。正如大多数有机化合物一样，土壤中HCH的降解发生在中等温度和接近中性的pH条件下。土壤中HCH的生物降解在低湿度和高（饱和）湿度条件下均有报道。土壤质地和有机质似乎通过吸附机制以及对水分保持、细菌生长和pH的影响来影响降解。大多数研究报告的是土壤中相对低浓度（<500 mg/kg）HCH的生物降解情况。关于无机养分、有机碳源或其他土壤改良剂影响的信息较为零散且尚无定论。需要对高HCH浓度土壤进行大规模的改良剂效果更深入评估以及生物修复方案评价。
